Title of Invention	SYSTEM AND METHODS FOR MEDIUM ACCESS CONTROL IN AD HOC ULTRAWIDEBAND WIRELESS MULTIMEDIA NETWORKS
Abstract	The present invention presented in this work relates to is on the design of Medium Access Control (MAC) system and associated methods so that it can be used for Ad Hoc Ultra wideband wireless multimedia network meeting QoS requirement specification. At first the invention proposes the various MAC systems which are as follows: 1) System for nodes to get relevant performance related information from other nodes in ad hoc network; 2) ECSMA/CA/Rate MAC for ad hoc UWB data networks where all applications have either rate requirements or no performance requirements at all; 3) ECSMA/CA/AvgDely/Rate for ad hoc UWB data networks where applications have requirements for average delay and rate; 4) ECSMA/CA/QoS for ad hoc UWB Multimedia networks for applications with delay bound jitter and rate requirements. Secondly, it proposes several methods to compute length of the packet that a TN is allowed to transmit when it gains access to chancel via these different MAC systems in an ad hoc UWB networks. Third, adaptive backoff methods for these MAC systems are proposed. Hence this invention work invents an efficient MAC protocol which controls access to the channel and provides QoS guarantees for different types of applications ( like multimedia, conferencing, streaming, VoIP, web browsing etc) present in a UWB network.

Title of Invention

SYSTEM AND METHODS FOR MEDIUM ACCESS CONTROL IN AD HOC ULTRAWIDEBAND WIRELESS MULTIMEDIA NETWORKS

Abstract

The present invention presented in this work relates to is on the design of Medium Access Control (MAC) system and associated methods so that it can be used for Ad Hoc Ultra wideband wireless multimedia network meeting QoS requirement specification. At first the invention proposes the various MAC systems which are as follows: 1) System for nodes to get relevant performance related information from other nodes in ad hoc network; 2) ECSMA/CA/Rate MAC for ad hoc UWB data networks where all applications have either rate requirements or no performance requirements at all; 3) ECSMA/CA/AvgDely/Rate for ad hoc UWB data networks where applications have requirements for average delay and rate; 4) ECSMA/CA/QoS for ad hoc UWB Multimedia networks for applications with delay bound jitter and rate requirements. Secondly, it proposes several methods to compute length of the packet that a TN is allowed to transmit when it gains access to chancel via these different MAC systems in an ad hoc UWB networks. Third, adaptive backoff methods for these MAC systems are proposed. Hence this invention work invents an efficient MAC protocol which controls access to the channel and provides QoS guarantees for different types of applications ( like multimedia, conferencing, streaming, VoIP, web browsing etc) present in a UWB network.

Full Text	FIELD OF TECHNOLOGY This invention relates to the field of medium access control for ad hoc multimedia networks. More specifically, this invention relates to the field of medium access control for ad hoc Ultra-Wideband wireless multimedia networks. PRESENT STATE OF ART Ultra-Wideband (UWB) systems are mostly based on the Impulse Radio (IR) technology which uses very short pulses (such as of 0.1 to 1.5 nanoseconds). It results in wide spectral occupation in the frequency domain. One definition of a UWB transmission is a signal whose fractional bandwidth, Bf1 is larger than 2(f - f ) 0.25, where Bf =-±Ui—±LLi where fH is the highest frequency and fL is the JH ""//. lowest frequency in the transmission band. In general, an UWB network consists of TermiNodes (TNs) that are small personal devices that act both as a node and a terminal. As a terminal, a TN can initiate communication with another end-system. As a node, it forwards incoming data to an outgoing link. It includes transmission from a radio link to a radio link, from a radio link to a fixed link and from a fixed link to a radio link. Each node possesses a UWB transceiver for wireless communication with other nodes. Role of the medium access control (MAC) protocol is to coordinate transmission access to the channel that is shared by all the TNs, provide Quality of Service (QoS) guarantees for different applications and provide security. MAC domain of a TN includes the TN itself and other TNs which are within its radio range. A multi-hop UWB domain is the wireless area where the UWB technology is used and the multi-hop connectivity is exploited to obtain an end-to-end wireless communication path. Networking protocols work in this domain. Each TN works as a terminal and a node (router). An example of a distributed ad hoc network architecture consisting of a multi-hop domain is shown in Figure 1. In CSMA/CA, each node monitors the status of the channel before transmitting information. If channel is idle, a node is allowed to transmit a packet. If channel is sensed to be busy, the node defers transmission to a later time using an exponential backoff mechanism. In order to reduce the probability of two nodes colliding because they cannot listen to each other, CSMA/CA introduces a virtual carrier sending mechanism. Here, a source node which wants to transmit a packet first transmits a short control packet called RTS (request to send). This packet includes information for the source node, destination node and duration of the following transmission. The destination senses the medium and if it finds it free, transmits a CTS (clear to send) control packet that includes the same duration information. All nodes listening to either RTS or CTS packet, use this duration information along with physical carrier sensing when they want to use the medium. CSMA/CA as used in WLAN is shown in the Figure 2. The RTS frame has been shown in Figure 3 which consists of the five time slots: 1) In the first field, the frame control is transmitted; 2) The second field consists of the duration of the transmission which is going to occur; 3) In the third field the address of the receiving device is transmitted; 4) In the fourth field the address of the Transmitting device is transmitted; 5) In the fifth field, a CRC code is sent for error detection. With reference to Figure 4 CTS Frame Format has been shown where : 1) In the first field, the frame control is transferred; 2) In the second field, the duration of the transmission to be followed is specified; 3) In the third field, the address of the receiving device is transmitted; 4) Next a CRC code is transmitted for error detection. In WLAN, as specified in the IEEE 802.11x standards, available at www.ieee.org, the destination also sends an acknowledgement (ACK) back to the source node if the packet was received correctly. We note that this ACK feature is available in the CSMA/CA which is used for WLAN, but does not necessarily have to be part of other systems where CSMA/CA is used. If ACK is not used, then CSMA/CA protocol's slot configuration is as shown in the Figure 5. Here, following notations are used: Ts: Minimum time needed to sense carrier (like DIFS in IEEE802.11) Tacq: Channel acquisition time during which source and destination nodes achieve bit synchronization Trts: Time to transmit RTS packet Tcts: Time to transmit CTS packet Tdata: Time to transmit data LIMITATIONS A UWB network would typically need to support applications that are used in current internet such as multimedia conferencing, streaming, VoIP, web browsing etc. These applications have different requirements in terms of their delay bound, delay jitter rate, loss, and average delay. Current MAC protocols such as CSMA/CA and TDMA cannot specify these goals. There is need for an efficient MAC protocol which controls access to the channel and provides QoS guarantees for different types of applications present in a UWB network. It should also decide length of packets to be transmitted for each TN. UWB technology uses pico-second precision rules, and impulse radio and due to this the channel acquisition time can be very high. It can seriously impact MAC layer performance especially in protocols such as CSMA/CA where a node may also need wait to acquire the channel. If packet length is too short, it can result in poor performance due to high channel acquisition time. If packet lengths are too large, it can result in poor performance of other delay and/or jitter sensitive applications. As,bit-error rate is usually higher in wireless channels than in wired networks, longer packet lengths can also result in high packet error rate. OBJECTS OF THE INVENTION The primary object of this invention is to invent a System and Method for Medium Access control in ad hoc Ultra Wideband Wireless Multimedia Networks. It is another object of this invention to develop and modify the Media Access Control (MAC) so that QoS constraints can be extended for ad hoc wideband wireless network. It is another object of this invention to invent methods to compute length of packet that a node is allowed to transmit when it gains access to the channel via the MAC described here. It is another object of the invention to develop QoS constraints and map it at MAC layer so that the QoS concept can be extended even for ad hoc wideband wireless network. It is another object of the invention to invent methods for ad hoc wideband wireless multimedia network to meet QoS requirement at the terminal node invariably. SUMMARY OF THE INVENTION This invention first proposes the following MAC systems: - System for nodes to get relevant performance related information from other nodes in ad hoc network, - ECSMA/CA/Rate MAC for ad hoc UWB data networks where all applications have either rate requirements or no performance requirements at all, - ECSMA/CA/AvgDely/Rate for ad hoc UWB data networks where applications have requirements for average delay and rate - ECSMA/CA/QoS for ad hoc UWB Multimedia networks for applications with delay bound, jitter and rate requirements. It also proposes several methods to compute length of packets that a TN would be allowed to transmit when it gains access to channel via ECSMA/CA MAC systems described here, dynamic and adaptive scheduling methods for these MAC systems and uses QoS constraints and current network condition into account while computing length of packet that a TN is allowed to transmit. Next, it proposes adaptive backoff methods for the above MAC systems. Accordingly, the present invention comprises an enhanced CSMA/CA MAC system, for a UWB network where applications have only rate requirements where the network is a distributed Ultra- Wideband Wireless Multimedia ad hoc network consisting of a multi-hop domain, where for nodes to get relevant performance related information from other nodes in the network the RTS frame as well as the CTS frame are extended and a 1-byte control field, Rate_Cntrl, as described herein is appended to each of these to convey the rate control related information. Accordingly, the present invention further comprises a method of medium access control in an ECSMA/CA/Rate system , for an ad hoc UWB Wireless Networks where each TN is in the transmission range of any other TN in that domain, wherein each TN directly communicates with any other TN in that domain; wherein the UWB MAC domain consists of a distributed system, each TN runs ECSMA/CA/Rate MAC and where RTS and CTS frames are extended such that agg _reqrate and all other TNs each TN conveys its own value of V aSS _ servedrate(t d) j receive this value and thereby the length of packet that transmittable when it gets access to physical channel is computed. Accordingly, the present invention further comprises a method of enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their delay bound, jitter and rate requirements, termed ECSMA/CA/QoS MAC, where RTS and CTS frames are extended such that each TN conveys its information related to delay bound, and buffer in addition to average delay and rate control information in that for delay bound related information, each TN considers all its multiple flows which have requirements for delay bound and jitter and the head-of-line packet for all such delay and jitter sensitive flows of a TN. where delay bound for this flow is dbound(m,k)\ wtime(m9k,tdk) is the time period for which the head-of-line packet of flow m for the TN, 77V., has been in the system by the time tdk. And delta _rem(k,tdk) = (dbound(m,k) - wtime(m,k,td k)) ' Where {dbound{m,k)-wtime{m,k,tdk)) is maximum for the head-of-line packet for this flow m considering all the delay and jitter sensitive flows of the TN, TNk, at time, tdk. for buffer related information: and where each TN considers all its flows which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows, agg_buff{tdh,k) Where each TN, TNk, informs other nodes of the value of its agg_buff, considering only those flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames. The other objects, features and advantages of the present invention will be apparent from the accompanying drawings and the detailed description as follows. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1: represents an example of a Distributed Ad Hoc Networking Architecture consisting of a multi-hop domain; Figure 2: shows CSMA/CA as used in WLAN; Figure 3: shows RTS Frame Format; Figure 4: shows CTS Frame Format; Figure 5: shows the CSMA/CA MAC Protocol's slot configuration; Figure 6 and 7: shows the ECSMA/CA/Rate MAC in a UWB Networking System Figure 8: shows the extended RTS frame, ERTS_Rate (Type I) Frame with Rate Cntrl field; Figure 9: shows extended CTS frame, ECTS_Rate (Type I) Frame with Rate_Cntrl field; Figure 10: shows the Rate_Cntrl field, Rate_Cntrl; Figure 11: shows a QoS_Cntrl Field, QoS Cntrl; Figure 12: shows an ERTS_Rate (Type II) Frame for ECSMA/CA/Rate MAC; Figure 13: shows an ECTS_Rate (Type II) Frame for ECSMA/CA/Rate MAC; Figure 14: shows an extended ERTS_AvgDelay_Rate Frame with Rate_Cntrl and AvgDelay_Cntrl fields (Type I) Figure 15: shows an extended ECTS_AvgDelay_Rate Frame (Type I) with Rate_Cntrl and AvgDelay_Cntrl fields; Figure 16: shows an average control field, AvgDelay_Cntrl field; Figure 17: shows a QoS Control Field for ECSMA/CA/AvgDelay/Rate MAC; Figure 18: shows an ERTS_AvgDelay_Rate (Type-ll) Frame for ECSMA/CA/AvgDelay/Rate MAC; Figure 19: shows an ECTS_AvgDelay_Rate (Type-ll) Frame for ECSMA/CA/AvgDelay/Rate MAC; Figure 20: shows an ECSMA/CA/AvgDelay/Rate MAC; Figure 21: shows an ECSMA/CA/AvgDelay/Rate MAC; Figure 22: shows an ERTS_QoS (Type I) Frame; Figure 23: shows an ECTS_QoS (Type I) Frame; Figure 24: shows a QoS Control Field for ECSMA/CA/QoS MAC; Figure 25: shows an ERTS_QoS (Type II) Frame for ECSMA/CA/QoS MAC; Figure 26: shows an ECTS_QoS (Type II) Frame for ECSMA/CA/QoS MAC; Figure 27 and 28: shows ECSMA/CA/QoS MAC; DETAILED DESCRIPTION OF THE INVENTION ECSMA/CA/Rate MAC System for UWB Wireless Networks We consider a UWB MAC domain where each TN is in the transmission range of any other TN in that domain, thus each TN can directly communicate with any other TN in that domain. Next, we consider a scenario where each TN has one or more applications with rate requirement only. There could be multiple applications per TN. Thus applications running have either rate requirements or have no QoS requirements at all. It is possible that some of these applications have some other QoS requirements too but only the rate requirements are strict and other requirements are quite loose and these applications choose to explicitly specify only the rate requirements in a UWB network. Thus all applications which do not specify their rate requirements are considered to be best effort applications. In such situations, a network operator can use Enhanced CSMA/CA (ECSMA/CA/Rate) proposed here in a UWB network. In essence, the ECSMA/CA/Rate invented here is for UWB networking systems where applications either specify their QoS requirements in terms of their required rate or do not specify any QoS requirement. Referring to figure 6 , TNk has some data to send to TNZ. It senses that the channel is idle. It waits for a minimum fixed amount of time period, Tidle flX€d to check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/Rate MAC and sends an ERTS_Rate(k) message to TNZ. The TNz upon successfully receiving this message, sends an ECTS_Rate(z) message to 77V. The TN, 77V, upon successfully receiving the ECTS_Rate(z) message, sends the data packet. In figure 7,77Vk has some data to send to TNZ. It senses that the channel is idle. It waits for a minimum fixed amount of time period, Tidle flxed to check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, 77Vk computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/Rate MAC and sends an ERTS_Rate(k) message to TNZ. The 77Vz upon successfully receiving this message, sends a ECTS_Rate(z) message to 77V. It also starts a timer Twait dala. The TN, 77V, upon successfully receiving the ECTS_Rate(z) message, starts sending the data packet. This data packet may be lost or get corrupted. In such an event, the TN, 77V2, waits for Twait data, and sends an RTx_Data_Req request, asking 77Vk to retransmit the data packet. Let agg_reqratek be the aggregate required rate of 77V. If there are multiple application on a TN with rate requirements only, add the required rate of each application on a TN to compute aggregate required rate of each TN. In the system described here, each TN runs ECS MA/C A/Rate MAC. A UWB MAC domain consists of a distributed system and each TN needs to decide how much of data can it sends when it gets right to transmit on the channel. There is no centralized access point or coordinator in the system here. Thus, each TN needs to take a decision in a fair manner otherwise performance of applications running on other TNs would be impacted. Let agg_servedrate(t,k) be the aggregate served rate of 77V* at time t. It is the sum of served rate of all the applications running on a TN. Let tdk be an arbitrary time when 77V* has got access to channel with the use of ECSMA/CA/Rate and is ready to send data. Let L{td,k) be the length of data that TNk would be allowed to send with the ECSMA/CA protocol invented here. Suppose a TN,77VA, wants to send data to another TN, TNZ ai time tdk. There could be other TNs in the system which are already sending or receiving data at time tadJi or which also have data to send at time tdk. If the TN, TNk, is successful in getting access to the physical channel as per the ECSMA/CA/Rate MAC, which is described later in this document, we denote this time by tdk. Here, tdk > tdk and tdk is the first time instant after tdk when TNk is allowed to start sending control packets to TNZ as per ECSMA/CA/Rate protocol. A UWB networking system with the ECSMA/CA/Rate MAC works as follows. 1. If at time tdk, the TN, TNk, finds the channel is idle, it waits for a minimum fixed period of time to see if channel stays idle. (This step is similar to what is done in CSMA/CA). This minimum amount of time is pre-specified and we denote this by Tidle flxed 2. If the channel stays idle for Tidle flxed in step 1 above, TNk waits for an additional random amount of time which is computed as a function of network state, required QoS for each TN and observed QoS for each TN. For TNk, we denote this period of time by tdk. 3. If the channel stays idle for Tidle flxed and for random amount of time computed in step 2 (i.e. T™dom{tadk)\ the TN, TNk, sends an ERTS_Rate(k) packet to the TN, 7Wz(i.e. the TN whom it wants to send data to). This ERTS_Rate packet includes observed and required rate related information, and is described in the methods below. In this packet, it sets the duration field to be greater than or equal to the value of time that would be taken to send ERTS_Rate, ECTS_Rate and data packet in that network. TNs other than TNk and TNZ, use this value of duration and do not attempt transmission during this period. 4. If TN2 receives this packet successfully, it waits for a fixed amount of time (which we denote by Tinier flxed) and if it is ready to receive data from TNk, it sends a ECTS_Rate(z) packet to TNk. This packet includes observed and required rate related information. In the duration field, it sets a value which is greater than or equal to the time period needed for TNZ for sending the ECTS_Rate(z) message and an estimate of time for TNk\o send a data packet of size ACQ to TNZ. TNs other than TNk and TNZ, use this value of duration and do not attempt transmission during this period. 5. After sending the ECTS_Rate(z) packet, the TN, TNZ, starts a timer (referred to as TwaU data timer here), and waits for maximum amount of time which is equal to a pre-specified positive real number, Twait data. If TN2 does not receive data from TNk before expiry of the Twait data timer, it sends a RTx_Data_Req(z) message to TNk, informing TNk that the data was not received. Figure 7 shows an example of this situation. 6. If TNZ still doesn't receive data from TNk before the expiry of the timer Twait_data, it can resend the RTx_Data_Req(z) message to TNk, informing TNk that the data packet was not received. The TN, TNZ, can do for maximum of Max_RTx_Data_Req(z) times, where Max_RTx_Data_Req(z) is an integer positive finite number for TN, TNZ. 7. Upon receiving the ECTS_Rate(z) or the RTx_Data_Req(z) packet successfully, the TN, TNk, waits for Tin{er flxed and starts data transmission to TNz. In this data packet, it sets a value in the duration field which is equal to the time needed for TNk to transmit this data packet. Other TNs use this value of duration and do not attempt transmission during this period. Length of this data packet is chosen as described in the Method I below. 8. If the TN, TN2, receives data from TNk but data is not received correctly, it sends an RTx_Data_Req(z) message to TNk, informing TNk that the data packet was not received correctly. After this, the TN, TNZ, starts a timer, Twait data and waits to receive the correct data from TNk. 9. If data is still not received correctly or not received at all, the TN, TNZ, can retry sending RTx_Data_Req(z) message for the maximum of Max_RTxJDataJReq(z) times. Each time a TN waits for maximum of TWait data time period before resending a RTxJDataJReq message. 10. If the data is received correctly or Max__Rtx_Data__Req(z) number of attempts have been exhausted by the TN, TNZ, the system goes back to step 1. agg _ reqrate to use the above. For this Each TN needs to know the mm V aSS _ servedrate{t d ) j purpose, we use two different types of message formats. For Type-I message format, we extend the RTS frame as well as the CTS frame and append a 1-byte field to each of these to convey the rate control information. We call this a "Rate_Cntrl" field. We show the extended RTS frame, ERTS_Rate, in Figure 8, extended CTS frame, ECTS_Rate, in Figure 9 and rate control field, Rate_Cntrl, in Figure 10. In the Rate_Cntrl field, in the bits b1 to b7 (as in Figure 10), each TN carries its . The first bit of this field, bO in Figure 10, is set to 1 if agg _ reqrate V aSS _ servedrate{td) j agg _ reqrate V aSS _ servedrate(td ) j >1, otherwise the first bit, bO, is set to 0. We now propose a type II frame format for ERTS_Rate and ECTS_Rate frames which is shown in the Figure 11, 12 and 13. Figure 11 shows a QoS control field, QoS_Cntrl, First two bits of this field are used to convey rate control related information and other six bits are not used for ECSMA/CA/Rate MAC systems. ERTS_Rate and ECTS_Rate frames carry one-octet QoS_Cntrl field. Method II In the ECSMA/CA/Rate MAC invented here, a TN, TNk, which has data to send at time t, and has found the channel idle for Tidle Jixed period of time, computes a random amount of time T™dom and waits to see if the channel stays idle for that period and then only it can start sending data. To compute, random backoff period, an exponential backoff is used as in the CSMA/CA MAC. In the system described here, the backoff period is computed after taking into account required rate and observed rate of applications running on that TN. Let Tc be the size of contention window at any given time. For the system here, choose a random W positive number in the range (0, rc) and use this as the frac _ agg _ rate(t, k) backoff timer. Here, Wk is a pre-specified real positive number for the TN, TNk. ECSMA/CA/AvqDelav/Rate MAC System for Ad Hoc UWB Wireless Networks We consider a UWB network where each application on a TN has one of the following three types of requirements: - QoS requirements in terms of average delay and required rate, - QoS requirements in terms of required rate only, - Best effort applications with no QoS requirements. There could be multiple applications per TN and each of these could have diverse type of QoS requirement such as rate requirement, or rate and average delay requirements, or have no QoS requirements at all. In the system described here, each TN runs ECSMA/CA/AvgDelay/Rate MAC. Let agg_reqratek be the aggregate required rate of TNk considering all applications for the TN, TNk, which have requirements on rate (i.e. either applications with requirement on rate only or applications with requirement on rate and average delay). Add the required rate of each application on a TN to compute aggregate required rate of each TN. Let agg _servedrate(t,k) be the aggregate served rate of TNk at time t. It is the sum of served rate of all the applications running on a TN. Let tdk be an arbitrary time when TNk has got access to channel with the use of ECSMA/CA/AvgDelay/Rate and is ready to send data. Let L{td,k) be the length of data that TNk would be allowed to send with the ECSMA/CA/AvgDelay/Rate protocol invented here. Suppose a TN,77Vftl wants to send data to another TN, TN 2ai time tdk. There could be other TNs in the system which are already sending or receiving data at time tdk or which also have data to send at time tdk. If the TN, TNk, is successful in sending in getting access to the physical channel as per the ECSMA/CA/AvgDelay/Rate MAC, which is described later in this invention document, we denote this time by tdk. Here, tdk > tdk and tdk is the first time instant after tdk when TNk is allowed to start sending control packets to TN2 as per ECSMA/CA/AvgDelay/Rate MAC protocol. Consider a flow h of the TN TNk which has requirements for its average delay and rate. Let d°afg{k,h,tdk) be the observed average queuing delay of the IP packets flow h of the TN, 77V,, at the time tdk and d^gget{k,h)be the target queuing delay of flow h of the TN, TNk. Note that this observed average delay is in the queues in the TN, TNk, where packets have to wait before they get a chance to be transmitted. d'Jgget(.) is a finite positive real number. We extend the ERTS_Rate frame as well as the ECTS_Rate frame and append a 1-byte field, AvgDelay_Cntrl, to each of these to convey the average delay control information. We show the extended RTS frame, ERTS_AvgDelay_Rate, in Figure 14, extended CTS frame, ECTS_AvgDelay_Rate, in Figure 15 and average control field, AvgDelay_Cntrl, in Figure 16. Thus if TNa wants to send data to TNb, it sends an ERTS_AvgDelay_Rate message after getting access to channel via the ECSMA/CA/AvgDelay/Rate its average delay control field. Every other TN listens to this packet and comes to know value of the rate control and average delay control fields of TNa. Every other TN in the network listens to this ERTS_AvgDelay_Rate packet and makes note of the values given in the rate control and average delay control its average delay control field. Every other TN listens to this packet and comes to know value of the rate control and average delay control fields of TNb. considering all the flows for which observed average queuing delay is more than target queuing average delay. This invention also proposes a type II frame format for ERTS_AvgDelay_Rate and ECTS__AvgDelay_Rate frames which is shown in the Figure 18 and 19. Figure 17 shows a QoS control field, QoS__Cntrl, First two bits of this field are used to convey rate control related information, next two bits are used to convey average delay rated information, and other four bits are not used for ECSMA/CA/AvgDelay/Rate MAC systems. ERTS_AvgDelay_Rate and ECTS_AvgDelay_Rate frames carry one-octet QoS_Cntrl field. We define the following: Method VI In the ECSMA/CA/AvgDelay/Rate MAC invented here, a TIM, TNk, which has data to send at time t, and has found the channel idle for Tidle flxed period of time, computes a random amount of time Trandom and waits to see if the channel stays idle for that period and then only it can start sending data. To compute, random backoff period, an exponential backoff is used as in the CSMA/CA MAC. A threshold, frac_avgdelay_viol thres_1A, is pre-specified for each flow h which has requirement for its average delay. Here, frac avgdelay viol_thres_\h is a positive real number and frac _ avgdelay __ viol _ thres _ 1 h >0.0. Here, D(k) is a pre-specified positive real number for each TN, TNk and D(A:)>1.0. ECSMA/CA/QoS MAC System for Ad Hoc UWB Wireless Multimedia Networks We consider a UWB wireless multimedia network where applications have diverse tvoe of QoS reauirements. These include: - multimedia applications which have QoS requirements in terms of delay bound, jitter and required rate, - applications which have QoS requirements in terms of average delay and required rate, - applications which have QoS requirements in terms of required rate only, - best effort applications with no QoS requirements. There could be multiple applications per TN and each of these could have diverse type of QoS requirement. In the system described here, each TN runs ECSMA/CA/QoS MAC. Let agg_reqratek be the aggregate required rate of TNk considering all applications for the TN, TNk, which have requirements on rate (i.e. either applications with requirement on rate only or applications with requirement on rate and average delay or application with requirements on delay bound, rate and jitter). Add the required rate of each application on a TN to compute aggregate required rate of each TN. Let agg _servedrate(t,k) be the aggregate served rate of TNk at time t. It is the sum of served rate of all the applications running on a TN which have some sort of QoS requirements and does not include best effort applications. Let tdk be an arbitrary time when TNh has got access to channel with the use of ECSMA/CA/QoS MAC and is ready to send data. Let L(tdh) be the length of data that TNk would be allowed to send with the ECSMA/CA/QoS protocol invented here. Suppose a TN.77V, wants to send data to another TN, TNZ at time tdk. There could be other TNs in the system which are already sending or receiving data at time tdk or which also have data to send at time tadk. If the TN, TNk, is successful in sending in getting access to the physical channel as per the ECSMA/CA/QoS MAC, which is described later in this invention document, we denote this time by tdk. Here, tdk > tdk and tdk is the first time instant after tdk when TNk is allowed to start sending control packets to TNZ as per ECSMA/CA/QoS MAC protocol. Consider a flow h of the TN TNk which has requirements for its average delay and rate. Let d°al$g(k,h,tdk) be the observed average queuing delay of the IP packets flow h of the TN, TNk, at the time tdk and dfa^ei(k9h)be the target queuing delay of flow h of the TN, TNk. At any given time, tdk, choose one flow with requirements over average delay and rate for the TN, TNk. To select such a flow, use the mechanism presented in the ECSMA/CA/AvgDelay/Rate MAC is minimum at that time considering only those flows for which observed average queuing delay is higher than target average queuing delay. We extend the ERTS_AvgDelay_Rate frame as well as the ECTS_AvgDelay_Rate frame and append a 1-byte field, Buffer_Cntrl, and another one byte field, DBound_Cntrl, to each of these frames to convey buffer and delay bound related information. We show the extended RTS frame, ERTS_QoS, in Figure 22, extended CTS frame, ECTS_QoS, in Figure 23. We call these type-l frames. Rate_Cntrl field is used as in the ECSMA/CA/Rate MAC and AvgDelay_Cntrl field is used as in the ECSMA/CA/AvgDelay/Rate MAC. Each of these is a one octet field. The first bit indicates how to interpret information in the remaining seven bits. For Buffer_Cntrl and DBound_Cntrl, we simply use one octet field each for Type-I frames. Both of these fields carry non-negative values. We also propose a Type II, ERTS_QoS Frame and a Type II, ECTS_Frame. These are shown in the Figure 25 and 26. Each of these uses a one octet QoS control field which is shown in the Figure 24. Here, we use 2 bits for rate control related information, 2 bits for average delay related information, 2 bits for buffer depth related information and 2 bits for delay bound related information. In Figure 25 : 1) In the first field, the frame control is transmitted; 2) In the second field, the duration of the transmission which is to follow is specified; 3) In the third field, the address of the receiving device is specified; 4) In the fourth field, the address of the transmitting device is specified; 5) In the fifth field, an octet rate control field is transmitted which consists of 2 bits for rate control related information, 2 bits for average delay related information, 2 bits for buffer depth related information and 2 bits for delay bound related information; 6) The last field consists of a CRC code for error detection. The frame structure as shown in Figure 26 is as follows: 1) The first field consists of the frame control bits; 2) The second field consists of the duration of the transmission that is to follow; 3) The third field consists of the address of the receiving device; 4) The fourth field consists of the octet Qos control field; 5) The fifth and the final field consist of the CRC code for error detection. Each TN considers all its flows which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows. For TN, TNk, at time, tdk1 we denote this by agg_buff(tdfc,k). Each TN, TNk, informs other nodes of the value of its agg_buff, considering only those flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames. If Type I frame is used, then one octet is available for this information. If type-ll frame is used, then 2 bits are available to carry this information. The bits (b4, b5) in the QoS_Cntrl field are used for this purpose as given here. Let there be two pre-specified thresholds, aggbuff jh\ and aggbuff thl such that agg_buff _th2 > agg_buff Jh\ > 0. 1. If agg_buff(td,k,k)>agg_buff _th2, set (b4, b5)=(1. 1) in the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to agg_buff_th2. 2. If aggjmff Jh\ the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to agg_buff_th1. 3. If 0 QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to a small positive number fu such that 0 4. If agg_buff(tdtk9k)=0, set (b4, b5)=(0,0) in the QoS_Cntrl field of the TN which is sending such a message. To compute value of DBound_Cntrl, each TN considers all its flows which have requirements for delay bound and jitter. There could be multiple flows with requirements for delay bound and jitter for each TN. Consider the head-of-line packet for all such delay and jitter sensitive flows of a TN. This is the packet which has been in the queue (in TN) for maximum amount of time for that flow. Consider head-of-line packet of each delay and jitter sensitive flows for each TN, TNk, at time, tdk, and select a flow for which difference of the waiting time in the system and delay bound of that flow is maximum. Suppose flow m is such a selected flow for the TN, TNh% at time, td%k. Let delay bound for this flow be dbound(m,k). Let wtime(m,k,tdk) denote the time period for which the head-of-line packet of flow m for the TN, TNh, has been in the system by the time tdk. If a packet has been in a queue in the TN for a period which is greater than delay bound of the corresponding flow, then it is discarded. Thus we have, wtime(m,k,tdk) for the head-of-line packet for this flow m considering all the delay and jitter sensitive flows of the TN, TNk, at time, tdk. For such a flow of the TN, TNk, at time, tdk, we say: delta _ rem{k, tdk) = (dbound(m9 k) - wtime(m, k, td k)) Each TN, TNk1 informs other nodes of the value of its delta _rem{kjdk), by including this information in the ERTS_QoS and ECTS_QoS frames. If Type I frame is used, then one octet is available for this information. If type-ll frame is used, then 2 bits are available to carry this information. The bits (b6, b7) in the QoS_Cntrl field are used for this purpose as given here. Let there be three pre-specified thresholds, delta _ rem _ thO, delta _ rem _ th\ and delta _ rem _ thl, such that delta _ rem _ thl > delta _ rem _ th\ > delta _ rem _ thO > 0.0. 1. If delta_rem(kjdk)>delta rem thl, set (b6, b7)=(1, 1) in the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set DBound_Cntrl field of the sending TN to be equal to delta _rem jhl. 2. If delta_rem_th\ 0) in the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set DBound_Cntrl field of the sending TN to be equal to delta _ rem _ thl. 3. If delta rem_th0 the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set delta_rem of the sending TN to be equal to delta rem_th0. 4. If 0 QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set delta_rem of the sending TN to a small positive number o such that 0 With reference to figure 27,Nk has some data to send to TNZ. It senses that the channel is idle. It waits for a minimum fixed amount of time period, Tidle flxed to check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/QoS MAC and sends an ERTS_QoS(k) message to TNZ. The TNZ upon successfully receiving this message, sends a ECTSJ3oS(z) message to TNk. The TN, TNk, upon successfully receiving the ECTS_QoS(z) message, sends the data packet. In figure 28, TNk has some data to send to TNZ. It senses that the channel is idle. It waits for a minimum fixed amount of time period, Tid{e ftxed to check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/QoS MAC and sends an ERTS_QoS(k) message to TN2. The TNZ upon successfully receiving this message, sends a ECTS_QoS(z) message to TNk. It also starts a timer Twait data. The TN, TNki upon successfully receiving the ECTS_QoS(z) message, starts sending the data packet. This data packet may be lost or get corrupted. In such an event, the TN, TNZ, waits for Twait data, and sends an RTx_Data_Req(z) request, asking TNk to retransmit the data packet. Method VIM If a delay and jitter sensitive flow needs to be served when the TN, TNh, has got access to send data at time tdk, we choose L(tdk) such that frac_rate_cntrl{tdk,k) is as defined in the ECSMA/CA/Rate MAC, ACQ = It is a pre-specified, minimum length of a packet needed to reduce the impact on MAC layer performance due to higher channel acquisition time in UWB systems, Time td = tdk, Bk: a pre-specified positive scaling constant for TNk, Bk eR+, for each TN TNk, A(k) is a pre-specified scaling constant for TNk, A(k)> 1.0; Dk: a pre-specified positive scaling constant for TNk, Dk eR+, for each TN TNk, E(k) is a pre-specified scaling constant for TNk, E(k)> 1.0; Method IX In the ECSMA/CA/QoS MAC invented here, a TN, TNk, which has data to send at time t, and has found the channel idle for Tidle flxed period of time, computes a random amount of time T™kdom and waits to see if the channel stays idle for that period and then only it can start sending data. In the system described here, the backoff period is computed after taking into account required QoS and observed QoS of applications running on that TIM. Let Tc be the size of contention window at any given time. For the system here, choose a random positive number in the (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then use as follows: Other steps remain similar to those presented in the Method VIII. Method XI If agg-buff(k,tdk)>agg_buff _thres, where agg_buff_thres is a pre-specified (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then use as follows: Other steps remain similar to those presented in the Method VIII. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention. Embodiments of the invention may be implemented by using a programmed general purpose digital computer, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, optical, chemical, biological, quantum or nano-engineered systems, components and mechanisms may be used. In general, the functions of the present invention can be achieved by any means as is known in the art. Distributed, or networked systems, components and circuits can be used. Communication, or transfer, of data may be wired, wireless, or by any other means. It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope of the present invention to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above. Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term "or" as used herein is generally intended to mean "and/or" unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear. As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise. The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention. Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims. GLOSSARY OF TERMS AND THEIR DEFINITIONS ACK: Acknowledgement Channel Acquisition Time: Time taken for a transmitter and a receiver to achieve bit-synchronization. CSMA/CA: Carrier Sense Multiple Access with Collision Avoidance CTS: Clear To Send DIFS: Distributed Inter-Frame Spacing MAC: Medium Access Control MAC Domain: MAC domain of a TN includes the TN itself and other TNs which are within its radio range. Multi-hop UWB domain: It is the wireless area where the UWB technology is used and the multi-hop connectivity is exploited to obtain an end-to-end wireless communication path. QoS : Quality of service. Applications have different types of requirements and these should be met by the networks. These include delay bound, delay jitter, required rate, packet loss, and average delay. RTS: Request To Send. SIFS: Short Inter-Frame Spacing. TCP: Transport Control Protocol. A layer 4 protocol widely used in the internet. UWB: Ultra-Wideband. VoIP: Voice over IP. WLAN: Wireless Local Area Network. WE CLAIM 1. An enhanced CSMA/CA MAC system, for a UWB network where applications have only rate requirements where the network is a distributed Ultra- Wideband Wireless Multimedia ad hoc network consisting of a multi-hop domain, where for nodes to get relevant performance related information from other nodes in the network the RTS frame as well as the CTS frame are extended and a 1-byte control field, Rate_Cntrl, as described herein is appended to each of these to convey the rate control related information. 2. A system as claimed in claim 1, wherein a UWB MAC domain consists of a distributed system and each TN individually computes the quantum of data it sends when it gets right to transmit on the channel and there is no centralized access point or coordinator. 3. A system as claimed in claim 1, where a TN meets the QoS requirements in terms of average delay and required rate, and wherein the ERTS_Rate frame as well as the ECTS_Rate frame are extended and a 1-byte field, AvgDelay_Cntrl, as described herein is appended to each of these to convey the average delay control information. 4. A system as claimed in claim 1, wherein in a UWB network where each application on a TN for multimedia applications have QoS requirements in terms of delay bound, jitter and required rate, average delay and required rate, the ERTS_AvgDelay_Rate frame as well as the ECTS_AvgDelay_Rate frame are extended and a 1-byte field, Buffer_Cntrl as described herein , and another one byte field, DBound_Cntrl as described herein , are appended to each of these frames to convey buffer and delay bound related information. 5. A method of medium access control in an ECSMA/CA/Rate system , for an ad hoc UWB Wireless Networks where each TN is in the transmission range of any other TN in that domain, wherein each TN directly communicates with any other TN in that domain; wherein the UWB MAC domain consists of a distributed system, each TN runs ECSMA/CA/Rate MAC and where RTS and CTS frames are extended receive this value and thereby the length of packet that transmittable when it gets access to physical channel is computed. 6. A method of as claimed in claim 5, wherein, the length of the packet to be transmitted for a TN on gaining access to the physical channel is computed using the ECSMA/CA/Rate MAC as 7. A method as claimed in claim 5, wherein to compute Adaptive backoff , a TN, TNk, which has data to send at time t, and has found the channel idle for Tidle flxed period of time, computes a random amount of time Trandom and if the channel stays idle for that period starts sending data and wherein an exponential backoff is used in that the random backoff period is computed after taking into account required rate and observed rate of applications running on that TN in that a random positive frac rate_viol thres_2k and frac_rate_viol_thres_1 k, and the ESMA/CA/Rate MAC dynamically changes from one mode to another depending upon the required QoS and observed QoS for a node, wherein the length of data packet to send is computed as follows: 10.A method for enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their average delay and rate requirements, termed ECSMA/CA/AvgDelay/Rate MAC, RTS and CTS frames are extended such that each TN conveys its average delay related information, 14. A method of enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their delay bound, jitter and rate requirements, termed ECSMA/CA/QoS MAC, where RTS and CTS frames are extended such that each TN conveys its information related to delay bound, and buffer in addition to average delay and rate control information in that for delay bound related information, each TN considers all its multiple flows which have requirements for delay bound and jitter and the head-of-line packet for all such delay and jitter sensitive flows of a TN. where delay bound for this flow is dbound(m,k)\ wtime{m,k,tdk) is the time period for which the head-of-line packet of flow m for the (dbound(m,k)-wtime(m,k,tdk)) is maximum for the head-of-line packet for this flow m considering all the delay and jitter sensitive flows of the TN, TNk, at time, tdk. for buffer related information: and where each TN considers all its flows which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows. agg_buff{tdk,k) Where each TN, TNk, informs other nodes of the value of its agg_buff, considering only those flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames. 15. A method as claimed in claim 14, wherein the length of the packet to be allowed to be transmitted by a TN when it gains access to channel via the ECSMA/CA/QoS MAC is computed, in that if a delay and jitter sensitive flow needs to be served when the TN, TNk, has got access to send data at time tdk, L{tdk) is computed as 16. A method as claimed in claim 14, wherein the Adaptive backoff in the ECSMA/CA/QoS MAC is computed in that a TN, TNk% which has data to send at time t, and has found the channel idle for Tidle fvced period of time, computes a random amount of time T™kdom and waits to see if the channel stays idle for that period and then starts sending data.in that the backoff period is computed after taking into account required QoS and observed QoS of applications running on that TN. and a selected as the backoff timer. 17. A method as claimed in claim 14, wherein the length of packet to be allowed to be transmitted via ECSMA/CA/QoS MAC when a TN gains access to channel, is computed in that if delta_rem(k,tdk)> delta rem thres, where delta_rem_thres is a pre-specified (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then : 18. A method as claimed in claim 14, wherein the length of packet to be allowed to be transmitted via ECSMA/CA/QoS MAC when a TN gains access to channel is computed in that If agg__buff(k,tdk)> agg_buff _thres, where agg_buff_thres is a pre-specified (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then : 19. An enhanced CSMA/CA/AvgDelay/Rate MAC System for ad hoc UWB Wireless Networks as substantially as herein described particularly with reference to the figures 6-28. 20. A method for enhanced CSMA/CA/Rate medium access control for ad hoc UWB Wireless Networks as substantially as herein described particularly with reference to the figures 6-28 21. A method for enhanced CSMA/CA/QoS Medium access control for ad hoc UWB network where applications specify their delay bound, jitter and rate requirements substantially as herein described particularly with reference to the figures 6-28 Dated this 30th the day of December 2003

Full Text

FIELD OF TECHNOLOGY
This invention relates to the field of medium access control for ad hoc multimedia networks. More specifically, this invention relates to the field of medium access control for ad hoc Ultra-Wideband wireless multimedia networks.
PRESENT STATE OF ART
Ultra-Wideband (UWB) systems are mostly based on the Impulse Radio (IR) technology which uses very short pulses (such as of 0.1 to 1.5 nanoseconds). It results in wide spectral occupation in the frequency domain. One definition of a UWB transmission is a signal whose fractional bandwidth, Bf1 is larger than
2(f - f ) 0.25, where Bf =-±Ui—±LLi where fH is the highest frequency and fL is the
JH "*"//.
lowest frequency in the transmission band.
In general, an UWB network consists of TermiNodes (TNs) that are small personal devices that act both as a node and a terminal. As a terminal, a TN can initiate communication with another end-system. As a node, it forwards incoming data to an outgoing link. It includes transmission from a radio link to a radio link, from a radio link to a fixed link and from a fixed link to a radio link. Each node possesses a UWB transceiver for wireless communication with other nodes.
Role of the medium access control (MAC) protocol is to coordinate transmission access to the channel that is shared by all the TNs, provide Quality of Service (QoS) guarantees for different applications and provide security. MAC domain of a TN includes the TN itself and other TNs which are within its radio range.
A multi-hop UWB domain is the wireless area where the UWB technology is used and the multi-hop connectivity is exploited to obtain an end-to-end wireless communication path. Networking protocols work in this domain. Each TN works as a terminal and a node (router). An example of a distributed ad hoc network architecture consisting of a multi-hop domain is shown in Figure 1.

In CSMA/CA, each node monitors the status of the channel before transmitting information. If channel is idle, a node is allowed to transmit a packet. If channel is sensed to be busy, the node defers transmission to a later time using an exponential backoff mechanism. In order to reduce the probability of two nodes colliding because they cannot listen to each other, CSMA/CA introduces a virtual carrier sending mechanism. Here, a source node which wants to transmit a packet first transmits a short control packet called RTS (request to send). This packet includes information for the source node, destination node and duration of the following transmission. The destination senses the medium and if it finds it free, transmits a CTS (clear to send) control packet that includes the same duration information. All nodes listening to either RTS or CTS packet, use this duration information along with physical carrier sensing when they want to use the medium. CSMA/CA as used in WLAN is shown in the Figure 2.
The RTS frame has been shown in Figure 3 which consists of the five time slots:
1) In the first field, the frame control is transmitted;
2) The second field consists of the duration of the transmission which is going to occur;
3) In the third field the address of the receiving device is transmitted;
4) In the fourth field the address of the Transmitting device is transmitted;
5) In the fifth field, a CRC code is sent for error detection.
With reference to Figure 4 CTS Frame Format has been shown where :
1) In the first field, the frame control is transferred;
2) In the second field, the duration of the transmission to be followed is specified;
3) In the third field, the address of the receiving device is transmitted;
4) Next a CRC code is transmitted for error detection.
In WLAN, as specified in the IEEE 802.11x standards, available at www.ieee.org, the destination also sends an acknowledgement (ACK) back to the source node if the packet was received correctly. We note that this ACK feature is available in the CSMA/CA which is used for WLAN, but does not

necessarily have to be part of other systems where CSMA/CA is used. If ACK is
not used, then CSMA/CA protocol's slot configuration is as shown in the Figure
5. Here, following notations are used:
Ts: Minimum time needed to sense carrier (like DIFS in IEEE802.11)
Tacq: Channel acquisition time during which source and destination nodes
achieve bit synchronization
Trts: Time to transmit RTS packet
Tcts: Time to transmit CTS packet
Tdata: Time to transmit data
LIMITATIONS
A UWB network would typically need to support applications that are used in current internet such as multimedia conferencing, streaming, VoIP, web browsing etc. These applications have different requirements in terms of their delay bound, delay jitter rate, loss, and average delay. Current MAC protocols such as CSMA/CA and TDMA cannot specify these goals. There is need for an efficient MAC protocol which controls access to the channel and provides QoS guarantees for different types of applications present in a UWB network.
It should also decide length of packets to be transmitted for each TN. UWB technology uses pico-second precision rules, and impulse radio and due to this the channel acquisition time can be very high. It can seriously impact MAC layer performance especially in protocols such as CSMA/CA where a node may also need wait to acquire the channel. If packet length is too short, it can result in poor performance due to high channel acquisition time. If packet lengths are too large, it can result in poor performance of other delay and/or jitter sensitive applications. As,bit-error rate is usually higher in wireless channels than in wired networks, longer packet lengths can also result in high packet error rate.
OBJECTS OF THE INVENTION
The primary object of this invention is to invent a System and Method for Medium Access control in ad hoc Ultra Wideband Wireless Multimedia Networks.

It is another object of this invention to develop and modify the Media Access Control (MAC) so that QoS constraints can be extended for ad hoc wideband wireless network.
It is another object of this invention to invent methods to compute length of packet that a node is allowed to transmit when it gains access to the channel via the MAC described here.
It is another object of the invention to develop QoS constraints and map it at MAC layer so that the QoS concept can be extended even for ad hoc wideband wireless network.
It is another object of the invention to invent methods for ad hoc wideband wireless multimedia network to meet QoS requirement at the terminal node invariably.
SUMMARY OF THE INVENTION
This invention first proposes the following MAC systems:
- System for nodes to get relevant performance related information from other nodes in ad hoc network,
- ECSMA/CA/Rate MAC for ad hoc UWB data networks where all applications have either rate requirements or no performance requirements at all,
- ECSMA/CA/AvgDely/Rate for ad hoc UWB data networks where applications have requirements for average delay and rate
- ECSMA/CA/QoS for ad hoc UWB Multimedia networks for applications with delay bound, jitter and rate requirements.
It also proposes several methods to compute length of packets that a TN would be allowed to transmit when it gains access to channel via ECSMA/CA MAC systems described here, dynamic and adaptive scheduling methods for these MAC systems and uses QoS constraints and current network condition into account while computing length of packet that a TN is allowed to transmit.

Next, it proposes adaptive backoff methods for the above MAC systems.
Accordingly, the present invention comprises an enhanced CSMA/CA MAC system, for a UWB network where applications have only rate requirements where the network is a distributed Ultra- Wideband Wireless Multimedia ad hoc network consisting of a multi-hop domain, where for nodes to get relevant performance related information from other nodes in the network the RTS frame as well as the CTS frame are extended and a 1-byte control field, Rate_Cntrl, as described herein is appended to each of these to convey the rate control related information.
Accordingly, the present invention further comprises a method of medium access control in an ECSMA/CA/Rate system , for an ad hoc UWB Wireless Networks where each TN is in the transmission range of any other TN in that domain, wherein each TN directly communicates with any other TN in that domain; wherein the UWB MAC domain consists of a distributed system, each TN runs ECSMA/CA/Rate MAC and where RTS and CTS frames are extended such that

agg _reqrate
and all other TNs
each TN conveys its own value of
V aSS _ servedrate(t d) j
receive this value and thereby the length of packet that transmittable when it gets access to physical channel is computed.
Accordingly, the present invention further comprises a method of enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their delay bound, jitter and rate requirements, termed ECSMA/CA/QoS MAC, where RTS and CTS frames are extended such that each TN conveys its information related to delay bound, and buffer in addition to average delay and rate control information in that for delay bound related information, each TN considers all its multiple flows which have requirements for delay bound and jitter and the head-of-line packet for all such delay and jitter sensitive flows of a TN. where delay bound for this flow is dbound(m,k)\ wtime(m9k,tdk) is the time
period for which the head-of-line packet of flow m for the TN, 77V., has been in

the system by the time tdk. And
delta _rem(k,tdk) = (dbound(m,k) - wtime(m,k,td k)) ' Where
{dbound{m,k)-wtime{m,k,tdk)) is maximum for the head-of-line packet for this
flow m considering all the delay and jitter sensitive flows of the TN, TNk, at time,
tdk. for buffer related information: and where each TN considers all its flows
which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows, agg_buff{tdh,k) Where each TN,
TNk, informs other nodes of the value of its agg_buff, considering only those
flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames.
The other objects, features and advantages of the present invention will be apparent from the accompanying drawings and the detailed description as follows.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: represents an example of a Distributed Ad Hoc Networking Architecture consisting of a multi-hop domain;
Figure 2: shows CSMA/CA as used in WLAN;
Figure 3: shows RTS Frame Format;
Figure 4: shows CTS Frame Format;
Figure 5: shows the CSMA/CA MAC Protocol's slot configuration;
Figure 6 and 7: shows the ECSMA/CA/Rate MAC in a UWB Networking System
Figure 8: shows the extended RTS frame, ERTS_Rate (Type I) Frame with Rate Cntrl field;

Figure 9: shows extended CTS frame, ECTS_Rate (Type I) Frame with Rate_Cntrl field;
Figure 10: shows the Rate_Cntrl field, Rate_Cntrl;
Figure 11: shows a QoS_Cntrl Field, QoS Cntrl;
Figure 12: shows an ERTS_Rate (Type II) Frame for ECSMA/CA/Rate MAC;
Figure 13: shows an ECTS_Rate (Type II) Frame for ECSMA/CA/Rate MAC;
Figure 14: shows an extended ERTS_AvgDelay_Rate Frame with Rate_Cntrl and AvgDelay_Cntrl fields (Type I)
Figure 15: shows an extended ECTS_AvgDelay_Rate Frame (Type I) with Rate_Cntrl and AvgDelay_Cntrl fields;
Figure 16: shows an average control field, AvgDelay_Cntrl field;
Figure 17: shows a QoS Control Field for ECSMA/CA/AvgDelay/Rate MAC;
Figure 18: shows an ERTS_AvgDelay_Rate (Type-ll) Frame for ECSMA/CA/AvgDelay/Rate MAC;
Figure 19: shows an ECTS_AvgDelay_Rate (Type-ll) Frame for ECSMA/CA/AvgDelay/Rate MAC;
Figure 20: shows an ECSMA/CA/AvgDelay/Rate MAC;
Figure 21: shows an ECSMA/CA/AvgDelay/Rate MAC;
Figure 22: shows an ERTS_QoS (Type I) Frame;
Figure 23: shows an ECTS_QoS (Type I) Frame;
Figure 24: shows a QoS Control Field for ECSMA/CA/QoS MAC;
Figure 25: shows an ERTS_QoS (Type II) Frame for ECSMA/CA/QoS MAC;

Figure 26: shows an ECTS_QoS (Type II) Frame for ECSMA/CA/QoS MAC; Figure 27 and 28: shows ECSMA/CA/QoS MAC;
DETAILED DESCRIPTION OF THE INVENTION
ECSMA/CA/Rate MAC System for UWB Wireless Networks
We consider a UWB MAC domain where each TN is in the transmission range of any other TN in that domain, thus each TN can directly communicate with any other TN in that domain. Next, we consider a scenario where each TN has one or more applications with rate requirement only. There could be multiple applications per TN. Thus applications running have either rate requirements or have no QoS requirements at all. It is possible that some of these applications have some other QoS requirements too but only the rate requirements are strict and other requirements are quite loose and these applications choose to explicitly specify only the rate requirements in a UWB network. Thus all applications which do not specify their rate requirements are considered to be best effort applications. In such situations, a network operator can use Enhanced CSMA/CA (ECSMA/CA/Rate) proposed here in a UWB network. In essence, the ECSMA/CA/Rate invented here is for UWB networking systems where applications either specify their QoS requirements in terms of their required rate or do not specify any QoS requirement.
Referring to figure 6 , TNk has some data to send to TNZ. It senses that the
channel is idle. It waits for a minimum fixed amount of time period, Tidle flX€d to
check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk
computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/Rate MAC and sends an ERTS_Rate(k) message to TNZ. The
TNz upon successfully receiving this message, sends an ECTS_Rate(z)

message to 77V*. The TN, 77V*, upon successfully receiving the ECTS_Rate(z) message, sends the data packet.
In figure 7,77Vk has some data to send to TNZ. It senses that the channel is idle.
It waits for a minimum fixed amount of time period, Tidle flxed to check if the
channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, 77Vk computes length of
the data packet that it is allowed to send at that time as per the ECSMA/CA/Rate MAC and sends an ERTS_Rate(k) message to TNZ. The 77Vz upon successfully
receiving this message, sends a ECTS_Rate(z) message to 77V*. It also starts a
timer Twait dala. The TN, 77V*, upon successfully receiving the ECTS_Rate(z)
message, starts sending the data packet. This data packet may be lost or get corrupted. In such an event, the TN, 77V2, waits for Twait data, and sends an
RTx_Data_Req request, asking 77Vk to retransmit the data packet.
Let agg_reqratek be the aggregate required rate of 77V*. If there are multiple
application on a TN with rate requirements only, add the required rate of each application on a TN to compute aggregate required rate of each TN.
In the system described here, each TN runs ECS MA/C A/Rate MAC. A UWB MAC domain consists of a distributed system and each TN needs to decide how much of data can it sends when it gets right to transmit on the channel. There is no centralized access point or coordinator in the system here. Thus, each TN needs to take a decision in a fair manner otherwise performance of applications running on other TNs would be impacted.
Let agg_servedrate(t,k) be the aggregate served rate of 77V* at time t. It is the sum of served rate of all the applications running on a TN. Let tdk be an arbitrary time when 77V* has got access to channel with the use of

ECSMA/CA/Rate and is ready to send data. Let L{td,k) be the length of data that TNk would be allowed to send with the ECSMA/CA protocol invented here.
Suppose a TN,77VA, wants to send data to another TN, TNZ ai time tdk. There
could be other TNs in the system which are already sending or receiving data at time tadJi or which also have data to send at time tdk. If the TN, TNk, is
successful in getting access to the physical channel as per the ECSMA/CA/Rate MAC, which is described later in this document, we denote this time by tdk.
Here, tdk > tdk and tdk is the first time instant after tdk when TNk is allowed to start sending control packets to TNZ as per ECSMA/CA/Rate protocol.
A UWB networking system with the ECSMA/CA/Rate MAC works as follows.
1. If at time tdk, the TN, TNk, finds the channel is idle, it waits for a
minimum fixed period of time to see if channel stays idle. (This step is similar to what is done in CSMA/CA). This minimum amount of time is pre-specified and we denote this by Tidle flxed
2. If the channel stays idle for Tidle flxed in step 1 above, TNk waits for an
additional random amount of time which is computed as a function of network state, required QoS for each TN and observed QoS for each TN.
For TNk, we denote this period of time by tdk.
3. If the channel stays idle for Tidle flxed and for random amount of time
computed in step 2 (i.e. T™dom{tadk)\ the TN, TNk, sends an
ERTS_Rate(k) packet to the TN, 7Wz(i.e. the TN whom it wants to send
data to). This ERTS_Rate packet includes observed and required rate related information, and is described in the methods below. In this packet, it sets the duration field to be greater than or equal to the value of time that would be taken to send ERTS_Rate, ECTS_Rate and data

packet in that network. TNs other than TNk and TNZ, use this value of duration and do not attempt transmission during this period.
4. If TN2 receives this packet successfully, it waits for a fixed amount of time
(which we denote by Tinier flxed) and if it is ready to receive data from TNk,
it sends a ECTS_Rate(z) packet to TNk. This packet includes observed
and required rate related information. In the duration field, it sets a value which is greater than or equal to the time period needed for TNZ for
sending the ECTS_Rate(z) message and an estimate of time for TNk\o
send a data packet of size ACQ to TNZ. TNs other than TNk and TNZ,
use this value of duration and do not attempt transmission during this period.
5. After sending the ECTS_Rate(z) packet, the TN, TNZ, starts a timer
(referred to as TwaU data timer here), and waits for maximum amount of
time which is equal to a pre-specified positive real number, Twait data. If TN2 does not receive data from TNk before expiry of the Twait data timer, it sends a RTx_Data_Req(z) message to TNk, informing TNk that the data was not received. Figure 7 shows an example of this situation.
6. If TNZ still doesn't receive data from TNk before the expiry of the timer
Twait_data, it can resend the RTx_Data_Req(z) message to TNk, informing
TNk that the data packet was not received. The TN, TNZ, can do for
maximum of Max_RTx_Data_Req(z) times, where
Max_RTx_Data_Req(z) is an integer positive finite number for TN, TNZ.
7. Upon receiving the ECTS_Rate(z) or the RTx_Data_Req(z) packet
successfully, the TN, TNk, waits for Tin{er flxed and starts data transmission
to TNz. In this data packet, it sets a value in the duration field which is equal to the time needed for TNk to transmit this data packet. Other TNs

use this value of duration and do not attempt transmission during this period. Length of this data packet is chosen as described in the Method I below.
8. If the TN, TN2, receives data from TNk but data is not received correctly, it sends an RTx_Data_Req(z) message to TNk, informing TNk that the data packet was not received correctly. After this, the TN, TNZ, starts a timer, Twait data and waits to receive the correct data from TNk.
9. If data is still not received correctly or not received at all, the TN, TNZ,
can retry sending RTx_Data_Req(z) message for the maximum of Max_RTxJDataJReq(z) times. Each time a TN waits for maximum of TWait data time period before resending a RTxJDataJReq message.
10. If the data is received correctly or Max__Rtx_Data__Req(z) number of
attempts have been exhausted by the TN, TNZ, the system goes back to
step 1.

agg _ reqrate
to use the above. For this
Each TN needs to know the
mm
V aSS _ servedrate{t d ) j
purpose, we use two different types of message formats.
For Type-I message format, we extend the RTS frame as well as the CTS frame and append a 1-byte field to each of these to convey the rate control information. We call this a "Rate_Cntrl" field. We show the extended RTS frame, ERTS_Rate, in Figure 8, extended CTS frame, ECTS_Rate, in Figure 9 and rate control field, Rate_Cntrl, in Figure 10.

In the Rate_Cntrl field, in the bits b1 to b7 (as in Figure 10), each TN carries its
. The first bit of this field, bO in Figure 10, is set to 1 if
agg _ reqrate
V aSS _ servedrate{td) j
agg _ reqrate
V aSS _ servedrate(td ) j

>1, otherwise the first bit, bO, is set to 0.

We now propose a type II frame format for ERTS_Rate and ECTS_Rate frames which is shown in the Figure 11, 12 and 13. Figure 11 shows a QoS control field, QoS_Cntrl, First two bits of this field are used to convey rate control related information and other six bits are not used for ECSMA/CA/Rate MAC systems. ERTS_Rate and ECTS_Rate frames carry one-octet QoS_Cntrl field.

Method II
In the ECSMA/CA/Rate MAC invented here, a TN, TNk, which has data to send at time t, and has found the channel idle for Tidle Jixed period of time, computes a
random amount of time T™dom and waits to see if the channel stays idle for that
period and then only it can start sending data. To compute, random backoff period, an exponential backoff is used as in the CSMA/CA MAC. In the system described here, the backoff period is computed after taking into account required rate and observed rate of applications running on that TN. Let Tc be the size of
contention window at any given time. For the system here, choose a random
W
positive number in the range (0, *rc) and use this as the
frac _ agg _ rate(t, k)
backoff timer. Here, Wk is a pre-specified real positive number for the TN, TNk.

ECSMA/CA/AvqDelav/Rate MAC System for Ad Hoc UWB Wireless Networks
We consider a UWB network where each application on a TN has one of the following three types of requirements:
- QoS requirements in terms of average delay and required rate,
- QoS requirements in terms of required rate only,
- Best effort applications with no QoS requirements.
There could be multiple applications per TN and each of these could have diverse type of QoS requirement such as rate requirement, or rate and average delay requirements, or have no QoS requirements at all. In the system described here, each TN runs ECSMA/CA/AvgDelay/Rate MAC. Let agg_reqratek be the aggregate required rate of TNk considering all
applications for the TN, TNk, which have requirements on rate (i.e. either
applications with requirement on rate only or applications with requirement on rate and average delay). Add the required rate of each application on a TN to compute aggregate required rate of each TN. Let agg _servedrate(t,k) be the
aggregate served rate of TNk at time t. It is the sum of served rate of all the
applications running on a TN. Let tdk be an arbitrary time when TNk has got

access to channel with the use of ECSMA/CA/AvgDelay/Rate and is ready to send data. Let L{td,k) be the length of data that TNk would be allowed to send
with the ECSMA/CA/AvgDelay/Rate protocol invented here.
Suppose a TN,77Vftl wants to send data to another TN, TN 2ai time tdk. There
could be other TNs in the system which are already sending or receiving data at time tdk or which also have data to send at time tdk. If the TN, TNk, is
successful in sending in getting access to the physical channel as per the ECSMA/CA/AvgDelay/Rate MAC, which is described later in this invention document, we denote this time by tdk. Here, tdk > tdk and tdk is the first time
instant after tdk when TNk is allowed to start sending control packets to TN2 as per ECSMA/CA/AvgDelay/Rate MAC protocol.
Consider a flow h of the TN TNk which has requirements for its average delay and rate. Let d°afg{k,h,tdk) be the observed average queuing delay of the IP packets flow h of the TN, 77V,, at the time tdk and d^gget{k,h)be the target queuing delay of flow h of the TN, TNk. Note that this observed average delay is in the queues in the TN, TNk, where packets have to wait before they get a chance to be transmitted. d'Jgget(.) is a finite positive real number.
We extend the ERTS_Rate frame as well as the ECTS_Rate frame and append a 1-byte field, AvgDelay_Cntrl, to each of these to convey the average delay control information. We show the extended RTS frame, ERTS_AvgDelay_Rate, in Figure 14, extended CTS frame, ECTS_AvgDelay_Rate, in Figure 15 and average control field, AvgDelay_Cntrl, in Figure 16.

Thus if TNa wants to send data to TNb, it sends an ERTS_AvgDelay_Rate message after getting access to channel via the ECSMA/CA/AvgDelay/Rate

its average delay control field. Every other TN listens to this packet and comes to know value of the rate control and average delay control fields of TNa.
Every other TN in the network listens to this ERTS_AvgDelay_Rate packet and makes note of the values given in the rate control and average delay control

its average delay control field. Every other TN listens to this packet and comes to know value of the rate control and average delay control fields of TNb.

considering all the flows for which observed average queuing delay is more than target queuing average delay.
This invention also proposes a type II frame format for ERTS_AvgDelay_Rate and ECTS__AvgDelay_Rate frames which is shown in the Figure 18 and 19. Figure 17 shows a QoS control field, QoS__Cntrl, First two bits of this field are used to convey rate control related information, next two bits are used to convey average delay rated information, and other four bits are not used for ECSMA/CA/AvgDelay/Rate MAC systems. ERTS_AvgDelay_Rate and ECTS_AvgDelay_Rate frames carry one-octet QoS_Cntrl field.
We define the following:

Method VI
In the ECSMA/CA/AvgDelay/Rate MAC invented here, a TIM, TNk, which has data to send at time t, and has found the channel idle for Tidle flxed period of time,
computes a random amount of time Trandom and waits to see if the channel stays
idle for that period and then only it can start sending data. To compute, random backoff period, an exponential backoff is used as in the CSMA/CA MAC.

A threshold, frac_avgdelay_viol thres_1A, is pre-specified for each flow h
which has requirement for its average delay. Here, frac avgdelay viol_thres_\h is a positive real number and
frac _ avgdelay __ viol _ thres _ 1 h >0.0.

Here, D(k) is a pre-specified positive real number for each TN, TNk and D(A:)>1.0.
ECSMA/CA/QoS MAC System for Ad Hoc UWB Wireless Multimedia Networks
We consider a UWB wireless multimedia network where applications have diverse tvoe of QoS reauirements. These include:

- multimedia applications which have QoS requirements in terms of delay bound, jitter and required rate,
- applications which have QoS requirements in terms of average delay and required rate,
- applications which have QoS requirements in terms of required rate only,
- best effort applications with no QoS requirements.
There could be multiple applications per TN and each of these could have diverse type of QoS requirement. In the system described here, each TN runs ECSMA/CA/QoS MAC. Let agg_reqratek be the aggregate required rate of TNk
considering all applications for the TN, TNk, which have requirements on rate
(i.e. either applications with requirement on rate only or applications with requirement on rate and average delay or application with requirements on delay bound, rate and jitter). Add the required rate of each application on a TN to compute aggregate required rate of each TN. Let agg _servedrate(t,k) be the
aggregate served rate of TNk at time t. It is the sum of served rate of all the
applications running on a TN which have some sort of QoS requirements and does not include best effort applications. Let tdk be an arbitrary time when TNh
has got access to channel with the use of ECSMA/CA/QoS MAC and is ready to send data. Let L(tdh) be the length of data that TNk would be allowed to send
with the ECSMA/CA/QoS protocol invented here.
Suppose a TN.77V*, wants to send data to another TN, TNZ at time tdk. There
could be other TNs in the system which are already sending or receiving data at time tdk or which also have data to send at time tadk. If the TN, TNk, is
successful in sending in getting access to the physical channel as per the ECSMA/CA/QoS MAC, which is described later in this invention document, we
denote this time by tdk. Here, tdk > tdk and tdk is the first time instant after tdk when TNk is allowed to start sending control packets to TNZ as per ECSMA/CA/QoS MAC protocol.

Consider a flow h of the TN TNk which has requirements for its average delay and rate. Let d°al$g(k,h,tdk) be the observed average queuing delay of the IP packets flow h of the TN, TNk, at the time tdk and dfa^ei(k9h)be the target queuing delay of flow h of the TN, TNk. At any given time, tdk, choose one flow with requirements over average delay and rate for the TN, TNk. To select such a flow, use the mechanism presented in the ECSMA/CA/AvgDelay/Rate MAC

is minimum at that time considering only those flows for which observed average queuing delay is higher than target average queuing delay.
We extend the ERTS_AvgDelay_Rate frame as well as the ECTS_AvgDelay_Rate frame and append a 1-byte field, Buffer_Cntrl, and another one byte field, DBound_Cntrl, to each of these frames to convey buffer and delay bound related information. We show the extended RTS frame, ERTS_QoS, in Figure 22, extended CTS frame, ECTS_QoS, in Figure 23. We call these type-l frames.
Rate_Cntrl field is used as in the ECSMA/CA/Rate MAC and AvgDelay_Cntrl field is used as in the ECSMA/CA/AvgDelay/Rate MAC. Each of these is a one octet field. The first bit indicates how to interpret information in the remaining seven bits.
For Buffer_Cntrl and DBound_Cntrl, we simply use one octet field each for Type-I frames. Both of these fields carry non-negative values.
We also propose a Type II, ERTS_QoS Frame and a Type II, ECTS_Frame. These are shown in the Figure 25 and 26. Each of these uses a one octet QoS control field which is shown in the Figure 24. Here, we use 2 bits for rate control related information, 2 bits for average delay related information, 2 bits for buffer depth related information and 2 bits for delay bound related information.

In Figure 25 :
1) In the first field, the frame control is transmitted;
2) In the second field, the duration of the transmission which is to follow is specified;
3) In the third field, the address of the receiving device is specified;
4) In the fourth field, the address of the transmitting device is specified;
5) In the fifth field, an octet rate control field is transmitted which consists of 2 bits for rate control related information, 2 bits for average delay related information, 2 bits for buffer depth related information and 2 bits for delay bound related information;
6) The last field consists of a CRC code for error detection.
The frame structure as shown in Figure 26 is as follows:
1) The first field consists of the frame control bits;
2) The second field consists of the duration of the transmission that is to follow;
3) The third field consists of the address of the receiving device;
4) The fourth field consists of the octet Qos control field;
5) The fifth and the final field consist of the CRC code for error detection.
Each TN considers all its flows which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows. For TN, TNk,
at time, tdk1 we denote this by agg_buff(tdfc,k). Each TN, TNk, informs other
nodes of the value of its agg_buff, considering only those flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames. If Type I frame is used, then one octet is available for this information.
If type-ll frame is used, then 2 bits are available to carry this information. The bits (b4, b5) in the QoS_Cntrl field are used for this purpose as given here. Let there be two pre-specified thresholds, aggbuff jh\ and aggbuff thl such that
agg_buff _th2 > agg_buff Jh\ > 0.

1. If agg_buff(td,k,k)>agg_buff _th2, set (b4, b5)=(1. 1) in the QoS_Cntrl
field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to agg_buff_th2.
2. If aggjmff Jh\ the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to agg_buff_th1.
3. If 0 QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set agg_buff of the sending TN to be equal to a small positive number fu such that 0 4. If agg_buff(tdtk9k)=0, set (b4, b5)=(0,0) in the QoS_Cntrl field of the TN
which is sending such a message.
To compute value of DBound_Cntrl, each TN considers all its flows which have requirements for delay bound and jitter. There could be multiple flows with requirements for delay bound and jitter for each TN. Consider the head-of-line packet for all such delay and jitter sensitive flows of a TN. This is the packet which has been in the queue (in TN) for maximum amount of time for that flow.
Consider head-of-line packet of each delay and jitter sensitive flows for each TN, TNk, at time, tdk, and select a flow for which difference of the waiting time in
the system and delay bound of that flow is maximum. Suppose flow m is such a selected flow for the TN, TNh% at time, td%k. Let delay bound for this flow be
dbound(m,k). Let wtime(m,k,tdk) denote the time period for which the head-of-line packet of flow m for the TN, TNh, has been in the system by the time tdk. If
a packet has been in a queue in the TN for a period which is greater than delay bound of the corresponding flow, then it is discarded. Thus we have,

wtime(m,k,tdk) for the head-of-line packet for this flow m considering all the delay and jitter sensitive flows of the TN, TNk, at time, tdk.
For such a flow of the TN, TNk, at time, tdk, we say:
delta _ rem{k, tdk) = (dbound(m9 k) - wtime(m, k, td k))
Each TN, TNk1 informs other nodes of the value of its delta _rem{kjdk), by
including this information in the ERTS_QoS and ECTS_QoS frames. If Type I frame is used, then one octet is available for this information.
If type-ll frame is used, then 2 bits are available to carry this information. The bits (b6, b7) in the QoS_Cntrl field are used for this purpose as given here. Let there be three pre-specified thresholds, delta _ rem _ thO, delta _ rem _ th\ and
delta _ rem _ thl, such that delta _ rem _ thl > delta _ rem _ th\ > delta _ rem _ thO >
0.0.
1. If delta_rem(kjdk)>delta rem thl, set (b6, b7)=(1, 1) in the QoS_Cntrl
field of the TN which is sending such a message. The receiving TN would set DBound_Cntrl field of the sending TN to be equal to delta _rem jhl.
2. If delta_rem_th\ 0) in the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set DBound_Cntrl field of the sending TN to be equal to delta _ rem _ thl.
3. If delta rem_th0 the QoS_Cntrl field of the TN which is sending such a message. The receiving TN would set delta_rem of the sending TN to be equal to delta rem_th0.
4. If 0 QoS_Cntrl field of the TN which is sending such a message. The

receiving TN would set delta_rem of the sending TN to a small positive number o such that 0 With reference to figure 27,Nk has some data to send to TNZ. It senses that
the channel is idle. It waits for a minimum fixed amount of time period, Tidle flxed to
check if the channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk
computes length of the data packet that it is allowed to send at that time as per the ECSMA/CA/QoS MAC and sends an ERTS_QoS(k) message to TNZ. The
TNZ upon successfully receiving this message, sends a ECTSJ3oS(z) message
to TNk. The TN, TNk, upon successfully receiving the ECTS_QoS(z) message,
sends the data packet.
In figure 28, TNk has some data to send to TNZ. It senses that the channel is
idle. It waits for a minimum fixed amount of time period, Tid{e ftxed to check if the
channel stays idle. If the channel stays idle, it computes a random amount of time which depends upon network state, required QoS and observed QoS. If the channel stays idle for this random amount of time also, TNk computes length of
the data packet that it is allowed to send at that time as per the ECSMA/CA/QoS MAC and sends an ERTS_QoS(k) message to TN2. The TNZ upon successfully
receiving this message, sends a ECTS_QoS(z) message to TNk. It also starts a
timer Twait data. The TN, TNki upon successfully receiving the ECTS_QoS(z)
message, starts sending the data packet. This data packet may be lost or get corrupted. In such an event, the TN, TNZ, waits for Twait data, and sends an
RTx_Data_Req(z) request, asking TNk to retransmit the data packet.
Method VIM
If a delay and jitter sensitive flow needs to be served when the TN, TNh, has got access to send data at time tdk, we choose L(tdk) such that

frac_rate_cntrl{tdk,k) is as defined in the ECSMA/CA/Rate MAC,
ACQ = It is a pre-specified, minimum length of a packet needed to reduce the
impact on MAC layer performance due to higher channel acquisition time in
UWB systems,
Time td = tdk,
Bk: a pre-specified positive scaling constant for TNk, Bk eR+, for each TN TNk, A(k) is a pre-specified scaling constant for TNk, A(k)> 1.0;
Dk: a pre-specified positive scaling constant for TNk, Dk eR+, for each TN TNk, E(k) is a pre-specified scaling constant for TNk, E(k)> 1.0;
Method IX
In the ECSMA/CA/QoS MAC invented here, a TN, TNk, which has data to send at time t, and has found the channel idle for Tidle flxed period of time, computes a
random amount of time T™kdom and waits to see if the channel stays idle for that

period and then only it can start sending data. In the system described here, the backoff period is computed after taking into account required QoS and observed QoS of applications running on that TIM. Let Tc be the size of contention window
at any given time. For the system here, choose a random positive number in the

(a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then use as follows:

Other steps remain similar to those presented in the Method VIII. Method XI
If agg-buff(k,tdk)>agg_buff _thres, where agg_buff_thres is a pre-specified
(a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then use as follows:

Other steps remain similar to those presented in the Method VIII.
In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced

without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.
Embodiments of the invention may be implemented by using a programmed general purpose digital computer, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, optical, chemical, biological, quantum or nano-engineered systems, components and mechanisms may be used. In general, the functions of the present invention can be achieved by any means as is known in the art. Distributed, or networked systems, components and circuits can be used. Communication, or transfer, of data may be wired, wireless, or by any other means.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope of the present invention to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above.
Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term "or" as used herein is generally intended to mean "and/or" unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear.
As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates otherwise.

Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims.

GLOSSARY OF TERMS AND THEIR DEFINITIONS
ACK: Acknowledgement
Channel Acquisition Time: Time taken for a transmitter and a receiver to
achieve bit-synchronization.
CSMA/CA: Carrier Sense Multiple Access with Collision Avoidance
CTS: Clear To Send
DIFS: Distributed Inter-Frame Spacing
MAC: Medium Access Control
MAC Domain: MAC domain of a TN includes the TN itself and other TNs which
are within its radio range.
Multi-hop UWB domain: It is the wireless area where the UWB technology is
used and the multi-hop connectivity is exploited to obtain an end-to-end wireless
communication path.
QoS : Quality of service. Applications have different types of requirements and
these should be met by the networks. These include delay bound, delay jitter,
required rate, packet loss, and average delay.
RTS: Request To Send.
SIFS: Short Inter-Frame Spacing.
TCP: Transport Control Protocol. A layer 4 protocol widely used in the internet.
UWB: Ultra-Wideband.
VoIP: Voice over IP.
WLAN: Wireless Local Area Network.

WE CLAIM
1. An enhanced CSMA/CA MAC system, for a UWB network where applications have only rate requirements where the network is a distributed Ultra- Wideband Wireless Multimedia ad hoc network consisting of a multi-hop domain, where for nodes to get relevant performance related information from other nodes in the network the RTS frame as well as the CTS frame are extended and a 1-byte control field, Rate_Cntrl, as described herein is appended to each of these to convey the rate control related information.
2. A system as claimed in claim 1, wherein a UWB MAC domain consists of a distributed system and each TN individually computes the quantum of data it sends when it gets right to transmit on the channel and there is no centralized access point or coordinator.
3. A system as claimed in claim 1, where a TN meets the QoS requirements in terms of average delay and required rate, and wherein the ERTS_Rate frame as well as the ECTS_Rate frame are extended and a 1-byte field, AvgDelay_Cntrl, as described herein is appended to each of these to convey the average delay control information.
4. A system as claimed in claim 1, wherein in a UWB network where each application on a TN for multimedia applications have QoS requirements in terms of delay bound, jitter and required rate, average delay and required rate, the ERTS_AvgDelay_Rate frame as well as the ECTS_AvgDelay_Rate frame are extended and a 1-byte field, Buffer_Cntrl as described herein , and another one byte field, DBound_Cntrl as described herein , are appended to each of these frames to convey buffer and delay bound related information.
5. A method of medium access control in an ECSMA/CA/Rate system , for an ad
hoc UWB Wireless Networks where each TN is in the transmission range of any
other TN in that domain, wherein each TN directly communicates with any other
TN in that domain; wherein the UWB MAC domain consists of a distributed system,
each TN runs ECSMA/CA/Rate MAC and where RTS and CTS frames are extended

receive this value and thereby the length of packet that transmittable when it gets access to physical channel is computed.
6. A method of as claimed in claim 5, wherein, the length of the packet to be
transmitted for a TN on gaining access to the physical channel is computed using the
ECSMA/CA/Rate MAC as

7. A method as claimed in claim 5, wherein to compute Adaptive backoff , a TN,
TNk, which has data to send at time t, and has found the channel idle for Tidle flxed
period of time, computes a random amount of time Trandom and if the channel stays
idle for that period starts sending data and wherein an exponential backoff is used in that the random backoff period is computed after taking into account required rate and observed rate of applications running on that TN in that a random positive

frac rate_viol thres_2k and frac_rate_viol_thres_1 k, and the ESMA/CA/Rate
MAC dynamically changes from one mode to another depending upon the required QoS and observed QoS for a node, wherein the length of data packet to send is computed as follows:

10.A method for enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their average delay and rate requirements, termed ECSMA/CA/AvgDelay/Rate MAC, RTS and CTS frames are extended such that each TN conveys its average delay related information,

14. A method of enhanced CSMA/CA medium access control for ad hoc UWB network where applications specify their delay bound, jitter and rate requirements, termed ECSMA/CA/QoS MAC, where RTS and CTS frames are extended such that each TN conveys its information related to delay bound, and buffer in addition to average delay and rate control information in that for delay bound related information, each TN considers all its multiple flows which have requirements for delay bound and jitter and the head-of-line packet for all such delay and jitter sensitive flows of a TN. where delay bound for this flow is dbound(m,k)\ wtime{m,k,tdk) is the time period for which the head-of-line packet of flow m for the

(dbound(m,k)-wtime(m,k,tdk)) is maximum for the head-of-line packet for this flow
m considering all the delay and jitter sensitive flows of the TN, TNk, at time, tdk.
for buffer related information: and where each TN considers all its flows which have requirements for delay bound, jitter or average delay and adds length of pending packets for these flows. agg_buff{tdk,k) Where each TN, TNk, informs other nodes
of the value of its agg_buff, considering only those flows which have requirements for delay bound, average delay or jitter, by including this information in the ERTS_QoS and ECTS_QoS frames.
15. A method as claimed in claim 14, wherein the length of the packet to be allowed
to be transmitted by a TN when it gains access to channel via the ECSMA/CA/QoS
MAC is computed, in that if a delay and jitter sensitive flow needs to be served when
the TN, TNk, has got access to send data at time tdk, L{tdk) is computed as

16. A method as claimed in claim 14, wherein the Adaptive backoff in the
ECSMA/CA/QoS MAC is computed in that a TN, TNk% which has data to send at
time t, and has found the channel idle for Tidle fvced period of time, computes a random amount of time T™kdom and waits to see if the channel stays idle for that period and
then starts sending data.in that the backoff period is computed after taking into account required QoS and observed QoS of applications running on that TN. and a
selected as the backoff timer.
17. A method as claimed in claim 14, wherein the length of packet to be allowed to
be transmitted via ECSMA/CA/QoS MAC when a TN gains access to channel, is
computed in that if delta_rem(k,tdk)> delta rem thres, where delta_rem_thres is a

pre-specified (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then :

18. A method as claimed in claim 14, wherein the length of packet to be allowed to
be transmitted via ECSMA/CA/QoS MAC when a TN gains access to channel is
computed in that If agg__buff(k,tdk)> agg_buff _thres, where agg_buff_thres is a
pre-specified (a positive real number) threshold, and a delay and jitter sensitive flow of the TN, TNk, is selected to be served, then :

19. An enhanced CSMA/CA/AvgDelay/Rate MAC System for ad hoc UWB Wireless
Networks as substantially as herein described particularly with reference to the
figures 6-28.
20. A method for enhanced CSMA/CA/Rate medium access control for ad hoc
UWB Wireless Networks as substantially as herein described particularly with
reference to the figures 6-28
21. A method for enhanced CSMA/CA/QoS Medium access control for ad hoc UWB
network where applications specify their delay bound, jitter and rate requirements
substantially as herein described particularly with reference to the figures 6-28
Dated this 30th the day of December 2003

Documents:

1077-che-2003-abstract.pdf

1077-che-2003-claims filed.pdf

1077-che-2003-claims grand.pdf

1077-che-2003-correspondnece-others.pdf

1077-che-2003-correspondnece-po.pdf

1077-che-2003-description(complete) filed.pdf

1077-che-2003-description(complete) grand.pdf

1077-che-2003-drawings.pdf

1077-che-2003-form 1.pdf

1077-che-2003-form 19.pdf

1077-che-2003-form 26.pdf

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Patent Number

201067

Indian Patent Application Number

1077/CHE/2003

PG Journal Number

08/2007

Publication Date

23-Feb-2007

Grant Date

23-Jun-2006

Date of Filing

31-Dec-2003

Name of Patentee

M/S. SAMSUNG ELECTRONICS CO., LTD

Applicant Address

SAMSUNG ELECTRONICS COMPAMY LIMITED, KOREA, J.P TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052, KARNATAKA, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	TANEJA DR. MUKESH	SAMSUNG ELECTRONICS COMPAMY LIMITED, KOREA, J.P TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052, KARNATAKA, INDIA.

PCT International Classification Number

H04L12/28

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA