Title of Invention	METHOD FOR ESTABLISHING A TEMPORARY BUFFER FOR PACKET DATA TRANSMITTED FROM A MOBILE STATION TO A WIRELESS NETWORK
Abstract	The invention relates to a method for establishing a temporary buffer, called TBF, for packet data to be transmitted on a packet data channel from a mobile station (MS) uplink to a wireless network (BSS) it belongs to, characterized in that the method comprises the steps of : a) transmitting by the mobile station (MS) to the network (BSS) a request for the establishment of an early uplink TBF even if the mobile station has not data to transmit; b) establishing by the network an early uplink TBF to said mobile station (MS); c) scheduling by the network (BSS) permissions, also called USF, to the mobile station (MS) to transmit packet data from said early uplink TBF; d) transmitting dummy packets from said early uplink TBF by said mobile station (MS) as the proper USFs are detected and it has not data to transmit; e) transmitting available actual packet data from said early uplink TBF by said mobile station (MS) as the proper USFs are detected.

Title of Invention

METHOD FOR ESTABLISHING A TEMPORARY BUFFER FOR PACKET DATA TRANSMITTED FROM A MOBILE STATION TO A WIRELESS NETWORK

Abstract

The invention relates to a method for establishing a temporary buffer, called TBF, for packet data to be transmitted on a packet data channel from a mobile station (MS) uplink to a wireless network (BSS) it belongs to, characterized in that the method comprises the steps of : a) transmitting by the mobile station (MS) to the network (BSS) a request for the establishment of an early uplink TBF even if the mobile station has not data to transmit; b) establishing by the network an early uplink TBF to said mobile station (MS); c) scheduling by the network (BSS) permissions, also called USF, to the mobile station (MS) to transmit packet data from said early uplink TBF; d) transmitting dummy packets from said early uplink TBF by said mobile station (MS) as the proper USFs are detected and it has not data to transmit; e) transmitting available actual packet data from said early uplink TBF by said mobile station (MS) as the proper USFs are detected.

Full Text	FIELD OF THE INVENTION The present invention relates to the field of mobile radio systems from 2.5 generation, and more precisely to a method for the early establishment of uplink TBFs. To simplify the disclosure, used acronyms are given at the end of the description. For the sake of simplicity the only (E)GPRS embodiment of the invention will be described, but the same conclusions are valid for the other 3GPP systems (UMTS). BACKGROUND OF THE INVENTION Fig.1 shows the functional architecture of a GSM / EDGE network according to TS 44.060 V.6.2.0, including the following functional blocks: SGSN, GGSN, EIR, BSS, MSC/VLR, HLR, SMS-GMSC, SMS-IWMSC, SM-SC and MS. The latter includes a first functional block TE connected to a second functional block MT through a connection indicated by a Reference point R, typically supporting a standard serial interface. The MT block is connected to the Urn interface supplying packet data services on radio channels. The following interfaces are foreseen: Urn, Gi, Gp, Gb, Gn, Gp, Gf, Gs, Gr, Gd, D, E, C, whose connectivity between the relevant blocks are directly visible in the figure. In particular, the Gn interface connects two GSN nodes in the same PLMN system, while the Gp interface connects two GSN nodes belonging to different PLMN systems. The BSS block includes a plurality of BTS connected to a BSC through a respective Abis interface (fig.2). In operation, at the Um and Abis interfaces several protocols are stacked upon the physical layer, in particular MAC, RLC, and LLC. RLC gives a reliable radio link and maps the LLC frames within the physical GSM channel. Signalling procedures for accessing the radio channel are controlled by MAC, which also governs dynamic allocation of the resources (request and grant). Dynamic allocation means that a particular transmission resource, consisting for instance of a PDCH channel on a physical timeslot, is made time division shareable among more MS mobiles, each of them being engaged in an active session of data transfer, or signalling, through the same transmission resource jointly assigned. The sub-set of MAC procedures governing the dynamic allocation of resources, provides temporary connections on the physical layer, called TBFs, which include memory buffers to house the queues of RLC/MAC blocks. Each TBF connection enables the unidirectional transfer of data and user signalling within a cell between the network and a mobile station MS, or vice versa. Control messages for the establishment/abatement of a connection and the allocation/de-allocation of relevant supported physical resources, for instance of TBF buffers, contemplate different opportunities capable of covering the whole survey foreseen in the packet transfer mode of the RR sublayer. For simplicity, it is here described a very limited survey of establishment/abatement of TBF connections and of the relevant operation modes. We can start from the establishment of a TBF uplink connection following a Packet Transfer originated by the mobile. In this case the mobile requires the assignment of a GPRS channel sending a PACKET CHANNEL REQUEST message including the resources requested for the transfer of packets to the network. In case of reception, the network replies with a PACKET UPLINK ASSIGNMENT message on the control channel allocating to the mobile the resources requested for the uplink transfer of packets. The resources include one or more PDCH channels and a TFI value. The network does not assign any buffer in uplink direction (the buffer resides in the mobile). The network requires simply knowing the number of blocks that a MS mobile intends to transmit. We can now proceed examining the establishment of a TBF connection downlink following a Packet Transfer ended towards the mobile. In this case at the end of the paging procedure, the network sends the mobile a PACKET DOWNLINK ASSIGNMENT message in the Ready state on the control channel, with enclosed the list of PDCH channels allocated for the downlink transfer. A buffer, relevant to the downlink TBF, is purposely allocated to contain the RLC/MAC blocks to be sent. In the majority of the cases a TBF is kept alive only for the transfer of one or more LLC protocol units, to the right purpose of transferring the corresponding RLC/MAC blocks. The network assigns each TBF connection its own temporary identifier, called TFi (Temporary Flow Identity). The mobile shall assume that the TFI value is unique among TBF competitors in each direction, uplink or downlink. A RLC/MAC data block is identified to the TBF to which it is associated through its own field where the identifier TFI is written, and another field to indicate the uplink or downlink direction of the block. Should the RLC/MAC block be referred to a control message, a field is foreseen to indicate the message transmission direction and type. In the case of dynamic allocation, the header of each RLC/MAC block transmitted on a PDCH channel in "downlink" direction includes an additional field called USF, which is used by the network in the form of a flag to control the time division multiplexing of different mobile stations on a physical channel PDCH in uplink direction. We can now better qualify the already mentioned PACKET UPLINK ASSIGNMENT message, sent by the network towards the mobiles, stating that it includes: the identifier TFI of the downlink/TBF buffer containing the control block carrying this message, the list of the allocated PDCH channels (time slots), and a corresponding USF value for each allocated channel. Three bits are foreseen for the USF field that enable to unambiguously discriminate up to eight users sharing a time-slot, also in the borderline case in which the single TBF buffer are associated all the eight time slots of a TOMA frame. The setup time of a TBF in (E)GPRS system might be in the order of several hundreds of milliseconds. In the case of an uplink TBF this is due to the combined effects of the random access procedure, the bring-up time on the A-bis interface, the round-trip time between the mobile station and the PCU, etc. For delay sensitive real-time applications a setup time of hundreds of milliseconds would impair the performance greatly. For instance, this is the case for applications, or VoIP over cellular. In 3GPP, TSG GERAN is currently discussing possible enhancements to reduce latency in the PS domain, including solutions to reduce the initial setup time of a TBF. One idea, which has already been discussed in standardization, is the possibility to enable an "early TBF establishment", i.e. the possibility for a mobile station to request an uplink TBF even before some actual data is ready for transmission. If a mobile station is enabled to open an uplink TBF in advance (i.e. before some actual data is available for transmission), this means that no setup time will be needed as soon as there is a real need to transmit something in the uplink. Some specific proposals on how to realize this behaviour have already been presented for standardization: see for instance GP-052038 and GP-052039 (respectively become G2-050396 and G2-050397) on "Phantom TBFs". But such proposals have some important drawbacks. For instance: - they foresee the definition a special TBF type, only needed for this procedure, adding extra complexity in both the MS and the network; - they are linked to the support of multiple TBFs in both the MS and in the network, thus limiting the general applicability of the solution; - they are linked to the early detection of a SIP signalling indication by the MS. OBJECT OF THE INVENTION In view of the state of the art described, it is an object of the present invention to provide an alternative simpler solution that reuses some already available procedures in the standard and does not have the support of multiple TBFs, nor any other capability, as a pre-requisite. SUMMARY OF THE INVENTION The invention achieves said object by providing a method for establishing an uplink TBF, as disclosed in claim 1. Additional advantageous features are described in the dependent claims. The uplink TBF establishing method of the invention includes the following steps: a) transmitting by the mobile station to the network a request for the establishment of an early uplink TBF even if the mobile station has not data to transmit; b) establishing by the network an early uplink TBF to said mobile station; c) scheduling by the network permissions, also called USF, to the mobile station to transmit packet data from said early uplink TBF; d) transmitting dummy packets from said early uplink TBF by said mobile station as the proper USFs are detected and it has not data to transmit; e) transmitting available actual packet data from said early uplink TBF by said mobile station as the proper USFs are detected. As alternative to send dummy uplink control blocks, the mobile does not transmit any message if the support of this capability is indicated by the network. Thanks to the method of the invention the uplink TBF is kept in a sort of stand-by state, so that when further data needs to be transmitted the MS can immediately resume the transmission with no need to re-open the TBF passing through the random access procedure. According to a first embodiment of the invention, the early uplink TBF establishment information is a relatively new "cause" foreseen in the (EGPRS) Packet Channel Request message for one-phase access procedure, clarifying the request the mobile is performing on the (P)RACH is for an "Early TBF establishment". The specific indication to the BSS that the request being performed by the mobile station is for an "early TBF establishment" could also be used by the network to understand that the initial message transmitted by the mobile station to open the TBF (i.e. the empty LLC frame) doesn't carry any actual information. In this case the BSS could optionally decide to discard it locally (i.e. not forward it to the SGSN) therefore avoiding any impact also on the Gb interface. According to a second embodiment of the invention, and considering that the number of combination of bits still available to signal the early uplink TBF assignment cause in an access burst is very reduced, the early establishment is now a specific request to start an "extended UL TBF" in the second message of a two-phase access procedure, i.e. the Packet Resource Request message. Since this message is conveyed in a proper radio block and not in a short access burst, adding additional information to it wouldn't be problem at all. It should be noted that, even though the two-phase access procedure is intrinsically slower than the one-phase access one, this wouldn't be a problem at all in this case. This procedure would be used well before the actual need to send data, so that no extra delays would be added. The scheduler design imposes the predetermination of such real cases an early TBF establishment information is requested, such as delay-sensitive scenarios, is requested. After that, the transmission of dummy control blocks instead of true data upon the USF scheduling is currently used in the art. ADVANTAGES OF THE INVENTION The proposed solution: • Does not in introduce any delay at the very instant that incoming data to transmit become available. • Does not introduce additional procedures in the mobile station and in the network nor new TBFs types. • Does not require any capability indicator in the MS Radio Access Capability, nor to be linked to any other MS capability (e.g. mTBF or other). • Does not require the indication of specific network support. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The features of the present invention which are considered to be novel are set forth with particularity in the appended claims. The invention and its advantages may be understood with reference to the following detailed description of an embodiment thereof taken in conjunction with the accompanying drawings given for purely non-limiting explanatory purposes and wherein: - fig.1, already described, shows a GSM-EDGE system; - fig.2 shows a BSS block of fig.1 connected to several MS, constituting the scenario the present invention is implemented within; - figures 3 and 4 show two message sequence diagrams of two respective embodiments of the early uplink TBF establishment method according to the present invention. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION The GSM/EGPRS TDMA signal is structured as cyclic multiframes of 52 basic frames divided into 12 radio blocks plus two T frames used for the synchronisation and two X idle frames. Each radio block including four basic frames. The multiframe is used to time multiplex the GPRS and GSM logical channels. The LLC layer frames are segmented within the radio blocks of the RLC/MAC layer. Each radio block is transported by four consecutive Normal bursts of the multiframe. The four Normal bursts have to be intended as interleaved on four consecutive TDMA 4.615 ms frames. The resources necessary to the GPRS service foresee an additional number of logical channels supporting the transfer of radio blocks through the physical Packet Data Channel (PDCH). GPRS logical channels have names and functional characteristics greatly faithfully following those of the channels of the traditional GSM, though referred to packets. Two basic RLC/MAC block structures are used either for data transfer or for control message transfer. TS 44.060, fig. 10.0a.2.1 shows a structure for EGPRS data transfer including a RLC/MAC header and a RLC data block 1, optionally followed by a RLC data block 2. TS 44.060, fig. 10.0a.3.1 shows a structure for control message transfer including a MAC header and a RLC/MAC control block. The different components of an RLC/MAC block carrying a GPRS RLC data block or an RLC/MAC control block shall be assembled sequentially. Each component consists of an integer number of octets. The assembling of components shall be performed progressively, starting in octet number 1 of the physical block. Fig.2 shows a BSS block connected to a plurality of MS blocks. The BSS block includes a BSC block and some BTS blocks. The BSC block includes in turn a block called LLC Layer, a Physical Layer block, a TBF MANAGER block, and a Scheduler block. The BSC is connected to the SGSN block of the Figure through a Gb interface. The LLC Layer has a bi-directional connection with the TBF MANAGER that, in turn has a bi-directional connection with the Scheduler block and with the Physical Layer. The BSC is charged with the majority of the operations dealing with TBFs, and the exchange of relevant RR messages on the Abis interface. The LLC Layer sends to the TBF MANAGER the LLC frames for downlink buffered connections, and receives from the TBF MANAGER the LLC frames for the uplink connections. The TBF MANAGER sends to the Physical Layer the RLC/MAC radio blocks with the associated USF multiplexed for TDMA on each time slot. The Physical Layer sends the TBF Manager the RLC/MAC radio blocks coming indication of number of radio blocks to transmit for each DL_TBF connection and UL_TBF connection. The Scheduler, in its turn, includes a Downlink and an Uplink Scheduler providing the TBF MANAGER with scheduling information. The purpose of the packet access procedure is to establish a TBF to support the transfer of upper-layer PDUs in the direction from the mobile station to the network. Packet access shall be done on PCCCH, as defined in this clause, if a PCCCH exists. Otherwise, packet access shall be done on CCCH, as defined in 3GPP TS 44.018. The packet access can be done in either one phase (clause 7.1.2) or in two phases (clauses 7.1.2 and 7.1.3). According to TS 44.060, paragraph 7.1.2, the mobile station shall initiate the one phase packet access procedure by scheduling the sending of PACKET CHANNEL REQUEST messages on the PRACH channel corresponding to its PCCCH_GROUP and simultaneously leaving the packet idle mode. The mobile station shall use the last access parameters received on PBCCH. The PACKET CHANNEL REQUEST messages are sent on PRACH and contain an indication (establishment cause) of the type of access and parameters required to indicate the mobile station's demand of radio resource (frequency, timeslot, code, etc.). On receipt of a PACKET CHANNEL REQUEST message, the network may assign a radio resource on one or more PDCHs to be used by the mobile station for the TBF in GPRS TBF mode. On receipt of an EGPRS PACKET CHANNEL REQUEST message, the network may assign a radio resource on one or more PDCHs to be used by the mobile station for the TBF in EGPRS TBF mode or GPRS TBF mode. If the dynamic allocation medium access mode is used, the network shall include the USF values allocated for PDCHs in the PACKET UPLINK ASSIGNMENT message. In fig.3, the previous one phase access procedure is modified according to a first embodiment of the invention aimed to solve the problem of the early establishment of an uplink TBF. With reference to fig.3, the PACKET CHANNEL REQUEST message includes an additional establishment cause called "Early establishment cause" that is linked to those situations the cause is needed, for example the delay-sensitive real-time applications. The network, after having allocated the requested PDCH resources to the mobile station, predisposes it to receive dummy control block from the mobile, station In alternative the network predisposes it not to receive any messages if the support of this capability is indicated by the network. To this aim the network schedules the uplink transmission instants by conveying relevant USF flags in proper downlink messages, i.e. UPLINK ACK/NACK messages. The mobile station handshakes DUMMY control blocks to the USFs until an actual packet data is coming from the application. According to TS 44.060, paragraph 7.1.3, when the TBF is established using two phase access: in the first phase of a two phase access in a cell provided with a PCCCH, the same procedures as for one phase access are used until the network sends a PACKET UPLINK ASSIGNMENT message including a Single Block Allocation structure or Multi Block Allocation structure, denoting two phase access to the mobile station. The Multi Block Allocation structure may be used only if the mobile station has EGPRS capability (i.e. the network received an EGPRS PACKET CHANNEL REQUEST message from the mobile station). In the PACKET UPLINK ASSIGNMENT message, the network reserves a limited resource on one PDCH to the mobile station where the mobile station may transmit a PACKET RESOURCE REQUEST message and optionally an ADDITIONAL MS RADIO ACCESS CAPABILITIES message. In fig.4 the two phase access procedure is modified according to a second embodiment of the invention, also aimed to solve the problem of the early establishment of an uplink TBF. With reference to fig.4, the mobile sends a PACKET CHANNEL REQUEST message to the network, and receives back a PACKET UPLINK mobile replies to the PACKET UPLINK ASSIGNMENT message with a PACKET RESOURCE REQUEST message including an Extended uplink TBF information. The network establishes an Uplink TBF indicating the requesting mobile station and handshakes USF flags as in the previous fig.3 Although the invention has been described with particular reference to some preferred embodiments, it will be evident to those skilled in the art, that the present invention is not limited thereto, but further variations and modifications may be applied without departing from the scope thereof. USED ACRONYMS 3GPP - 3rd Generation Partnership Program BSC - Base Station Controller BSS - Base Station Subsystem BTS - Base Transceiver Station CCCH - Common Control Channel EDGE - Enhanced Data rates for GSM Evolution EGPRS - Enhanced GPRS EIR - Equipment Identity Register GERAN - GSM/EDGE Radio Access Network GGSN - Gateway GSN GMSC - Gateway MSC GP - GERAN Plenary GPRS - General Packet Radio Service GSM - Global System for Mobile communications IWMSC - InterWorking LLC - Logical Link Control MAC - Medium Access Protocol MS - Mobile Station MSC - Message Switching Centre MT - Mobile Terminated PBCCH - Packet Broadcast Control Channel PCCCH - Packet Common Control Channel PDCH - Packet Data Channel PDU - Protocol Data Unit PLMN - Public Land Mobile Network PoC - Push-to-Talk over Cellular PRACH - Physical Random Access Channel CR - Change Request RLC - Radio Link Control SC - Service Centre SGSN - Service GPRS Support Node SMS - Short Message Service TBF - Temporary Block Flow TE - Terminal Equipment TFI - TBF identifier TSG - Technical Specification Group UMTS - Universal Mobile Telecommunication System USF - Uplink State Flag VLR - Visitor Location Register VoIP - Voice over IP WE CLAIM : 1. Method for establishing a temporary buffer, called TBF, for packet data to be transmitted on a packet data channel from a mobile station (MS) uplink to a wireless network (BSS) it belongs to, characterized in that the method comprises the steps of: a) transmitting by the mobile station (MS) to the network (BSS) a request for the establishment of an early uplink TBF even if the mobile station has not data to transmit; b) establishing by the network an early uplink TBF to said mobile station (MS); c) scheduling by the network (BSS) permissions, also called USF, to the mobile station (MS) to transmit packet data from said early uplink TBF; d) transmitting dummy packets from said early uplink TBF by said mobile station (MS) as the proper USFs are detected and it has not data to transmit; e) transmitting available actual packet data from said early uplink TBF by said mobile station (MS) as the proper USFs are detected. 2. The method as claimed in claim 1, wherein after said step c) the network (BSS) predisposes it to receive dummy control block from that mobile station (MS). 3. The method as claimed in claim 2, wherein said dummy packets are discarded locally by the network (BSS). 4. The method as claimed in any of claim 1 to 3 wherein said request for the establishment an early uplink TBF is included in a PACKET CHANNEL REQUEST message of one phase packet access. 5. The method as claimed in claim 4, wherein the network (BSS) after step b) transmits a PACKET UPLINK ASSIGNMENT message to the mobile station (MS). 6. The method as claimed in any of claim 1 to 3, wherein said step a) is preceded by the following steps of two phase packet access: - transmitting, by the mobile station (MS), a PACKET CHANNEL REQUEST message to the network (BSS); - transmitting, by the network (BSS), a PACKET UPLINK ASSIGNMENT message to the mobile station (MS) 7. The method as claimed in claim 6, wherein said request for the establishment an early uplink TBF is included in a PACKET RESOURCE REQUEST message. 8. The method as claimed in any of claim 1 to 7, wherein said mobile station (MS) instead of transmitting said dummy packets does not transmit any packets if the support of this capability is indicated by the network. 9. The method as claimed in any of claim 1 to 8, wherein said early uplink TBF establishment is foreseen for delay-sensitive transmissions. 10. The method as claimed in any of claim 1 to 9, wherein wireless network (BSS) is standardized by 3GPP. ABSTRACT TITLE "METHOD FOR ESTABLISHING A TEMPORARY BUFFER FOR PACKET DATA TRANSMITTED FROM A MOBILE STATION TO A WIRELESS NETWORK" The invention relates to a method for establishing a temporary buffer, called TBF, for packet data to be transmitted on a packet data channel from a mobile station (MS) uplink to a wireless network (BSS) it belongs to, characterized in that the method comprises the steps of : a) transmitting by the mobile station (MS) to the network (BSS) a request for the establishment of an early uplink TBF even if the mobile station has not data to transmit; b) establishing by the network an early uplink TBF to said mobile station (MS); c) scheduling by the network (BSS) permissions, also called USF, to the mobile station (MS) to transmit packet data from said early uplink TBF; d) transmitting dummy packets from said early uplink TBF by said mobile station (MS) as the proper USFs are detected and it has not data to transmit; e) transmitting available actual packet data from said early uplink TBF by said mobile station (MS) as the proper USFs are detected.

Full Text

FIELD OF THE INVENTION
The present invention relates to the field of mobile radio systems from 2.5
generation, and more precisely to a method for the early establishment of uplink
TBFs. To simplify the disclosure, used acronyms are given at the end of the
description. For the sake of simplicity the only (E)GPRS embodiment of the
invention will be described, but the same conclusions are valid for the other
3GPP systems (UMTS).
BACKGROUND OF THE INVENTION
Fig.1 shows the functional architecture of a GSM / EDGE network according to
TS 44.060 V.6.2.0, including the following functional blocks: SGSN, GGSN, EIR,
BSS, MSC/VLR, HLR, SMS-GMSC, SMS-IWMSC, SM-SC and MS. The latter
includes a first functional block TE connected to a second functional block MT
through a connection indicated by a Reference point R, typically supporting a
standard serial interface. The MT block is connected to the Urn interface
supplying packet data services on radio channels. The following interfaces are
foreseen: Urn, Gi, Gp, Gb, Gn, Gp, Gf, Gs, Gr, Gd, D, E, C, whose connectivity
between the relevant blocks are directly visible in the figure. In
particular, the Gn interface connects two GSN nodes in the same PLMN system,
while the Gp interface connects two GSN nodes belonging to different PLMN
systems. The BSS block includes a plurality of BTS connected to a BSC through a
respective Abis interface (fig.2).

In operation, at the Um and Abis interfaces several protocols are stacked upon
the physical layer, in particular MAC, RLC, and LLC. RLC gives a reliable radio link
and maps the LLC frames within the physical GSM channel. Signalling procedures
for accessing the radio channel are controlled by MAC, which also governs
dynamic allocation of the resources (request and grant). Dynamic allocation
means that a particular transmission resource, consisting for instance of a PDCH
channel on a physical timeslot, is made time division shareable among more MS
mobiles, each of them being engaged in an active session of data transfer, or
signalling, through the same transmission resource jointly assigned.
The sub-set of MAC procedures governing the dynamic allocation of resources,
provides temporary connections on the physical layer, called TBFs, which include
memory buffers to house the queues of RLC/MAC blocks. Each TBF connection
enables the unidirectional transfer of data and user signalling within a cell
between the network and a mobile station MS, or vice versa. Control messages
for the establishment/abatement of a connection and the allocation/de-allocation
of relevant supported physical resources, for instance of TBF buffers,
contemplate different opportunities capable of covering the whole survey
foreseen in the packet transfer mode of the RR sublayer. For simplicity, it is here
described a very limited survey of establishment/abatement of TBF connections
and of the relevant operation modes. We can start from the establishment of a
TBF uplink connection following a Packet Transfer originated by the mobile. In
this case the mobile requires the assignment of a GPRS channel sending a
PACKET CHANNEL REQUEST message including the resources requested for the
transfer of packets to the network. In case of reception, the network replies with

a PACKET UPLINK ASSIGNMENT message on the control channel allocating to
the mobile the resources requested for the uplink transfer of packets. The
resources include one or more PDCH channels and a TFI value.
The network does not assign any buffer in uplink direction (the buffer resides in
the mobile). The network requires simply knowing the number of blocks that a
MS mobile intends to transmit. We can now proceed examining the
establishment of a TBF connection downlink following a Packet Transfer ended
towards the mobile. In this case at the end of the paging procedure, the network
sends the mobile a PACKET DOWNLINK ASSIGNMENT message in the Ready
state on the control channel, with enclosed the list of PDCH channels allocated
for the downlink transfer. A buffer, relevant to the downlink TBF, is purposely
allocated to contain the RLC/MAC blocks to be sent.
In the majority of the cases a TBF is kept alive only for the transfer of one or
more LLC protocol units, to the right purpose of transferring the corresponding
RLC/MAC blocks. The network assigns each TBF connection its own temporary
identifier, called TFi (Temporary Flow Identity). The mobile shall assume that the
TFI value is unique among TBF competitors in each direction, uplink or downlink.
A RLC/MAC data block is identified to the TBF to which it is associated through
its own field where the identifier TFI is written, and another field to indicate the
uplink or downlink direction of the block. Should the RLC/MAC block be referred
to a control message, a field is foreseen to indicate the message transmission
direction and type. In the case of dynamic allocation, the header of
each RLC/MAC block transmitted on a PDCH channel in "downlink" direction
includes an additional field called USF, which is used by the network in the form
of a flag to control the time division multiplexing of different mobile stations on a
physical channel PDCH in uplink direction. We can now better qualify the already
mentioned PACKET UPLINK ASSIGNMENT message, sent by the network towards
the mobiles, stating that it includes:

the identifier TFI of the downlink/TBF buffer containing the control block carrying
this message, the list of the allocated PDCH channels (time slots), and a
corresponding USF value for each allocated channel. Three bits are foreseen for
the USF field that enable to unambiguously discriminate up to eight users sharing
a time-slot, also in the borderline case in which the single TBF buffer are
associated all the eight time slots of a TOMA frame.
The setup time of a TBF in (E)GPRS system might be in the order of several
hundreds of milliseconds. In the case of an uplink TBF this is due to the
combined effects of the random access procedure, the bring-up time on the A-bis
interface, the round-trip time between the mobile station and the PCU, etc.
For delay sensitive real-time applications a setup time of hundreds of
milliseconds would impair the performance greatly. For instance, this is the case
for applications, or VoIP over cellular.
In 3GPP, TSG GERAN is currently discussing possible enhancements to reduce
latency in the PS domain, including solutions to reduce the initial setup time of a
TBF.
One idea, which has already been discussed in standardization, is the possibility
to enable an "early TBF establishment", i.e. the possibility for a mobile station to
request an uplink TBF even before some actual data is ready for transmission.
If a mobile station is enabled to open an uplink TBF in advance (i.e. before some
actual data is available for transmission), this means that no setup time will be
needed as soon as there is a real need to transmit something in the uplink.

Some specific proposals on how to realize this behaviour have already been
presented for standardization: see for instance GP-052038 and GP-052039
(respectively become G2-050396 and G2-050397) on "Phantom TBFs". But such
proposals have some important drawbacks. For instance:
- they foresee the definition a special TBF type, only needed for this procedure,
adding extra complexity in both the MS and the network;
- they are linked to the support of multiple TBFs in both the MS and in the
network, thus limiting the general applicability of the solution;
- they are linked to the early detection of a SIP signalling indication by the MS.
OBJECT OF THE INVENTION
In view of the state of the art described, it is an object of the present invention
to provide an alternative simpler solution that reuses some already available
procedures in the standard and does not have the support of multiple TBFs, nor
any other capability, as a pre-requisite.
SUMMARY OF THE INVENTION
The invention achieves said object by providing a method for establishing an
uplink TBF, as disclosed in claim 1. Additional advantageous features are
described in the dependent claims.

The uplink TBF establishing method of the invention includes the following steps:
a) transmitting by the mobile station to the network a request for the
establishment of an early uplink TBF even if the mobile station has not data to
transmit;
b) establishing by the network an early uplink TBF to said mobile station;
c) scheduling by the network permissions, also called USF, to the mobile station
to transmit packet data from said early uplink TBF;
d) transmitting dummy packets from said early uplink TBF by said mobile station
as the proper USFs are detected and it has not data to transmit;
e) transmitting available actual packet data from said early uplink TBF by said
mobile station as the proper USFs are detected.
As alternative to send dummy uplink control blocks, the mobile does not transmit
any message if the support of this capability is indicated by the network. Thanks
to the method of the invention the uplink TBF is kept in a sort of stand-by state,
so that when further data needs to be transmitted the MS can immediately
resume the transmission with no need to re-open the TBF passing through the
random access procedure.

According to a first embodiment of the invention, the early uplink TBF
establishment information is a relatively new "cause" foreseen in the (EGPRS)
Packet Channel Request message for one-phase access procedure, clarifying the
request the mobile is performing on the (P)RACH is for an "Early TBF
establishment". The specific indication to the BSS that the request being
performed by the mobile station is for an "early TBF establishment" could also be
used by the network to understand that the initial message transmitted by the
mobile station to open the TBF (i.e. the empty LLC frame) doesn't carry any
actual information. In this case the BSS could optionally decide to discard it
locally (i.e. not forward it to the SGSN) therefore avoiding any impact also on the
Gb interface.
According to a second embodiment of the invention, and considering that the
number of combination of bits still available to signal the early uplink TBF
assignment cause in an access burst is very reduced, the early establishment is
now a specific request to start an "extended UL TBF" in the second message of a
two-phase access procedure, i.e. the Packet Resource Request message. Since
this message is conveyed in a proper radio block and not in a short access burst,
adding additional information to it wouldn't be problem at all. It should be noted
that, even though the two-phase access procedure is intrinsically slower than the
one-phase access one, this wouldn't be a problem at all in this case. This
procedure would be used well before the actual need to send data, so that no
extra delays would be added.
The scheduler design imposes the predetermination of such real cases an early
TBF establishment information is requested, such as delay-sensitive scenarios, is
requested.

After that, the transmission of dummy control blocks instead of true data upon
the USF scheduling is currently used in the art.
ADVANTAGES OF THE INVENTION
The proposed solution:
• Does not in introduce any delay at the very instant that incoming data to
transmit become available.
• Does not introduce additional procedures in the mobile station and in the
network nor new TBFs types.
• Does not require any capability indicator in the MS Radio Access Capability, nor
to be linked to any other MS capability (e.g. mTBF or other).
• Does not require the indication of specific network support.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The features of the present invention which are considered to be novel are set
forth with particularity in the appended claims. The invention and its advantages
may be understood with reference to the following detailed description of an
embodiment thereof taken in conjunction with the accompanying drawings given
for purely non-limiting explanatory purposes and wherein:

- fig.1, already described, shows a GSM-EDGE system;
- fig.2 shows a BSS block of fig.1 connected to several MS, constituting the
scenario the present invention is implemented within;
- figures 3 and 4 show two message sequence diagrams of two respective
embodiments of the early uplink TBF establishment method according to the
present invention.
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
The GSM/EGPRS TDMA signal is structured as cyclic multiframes of 52 basic
frames divided into 12 radio blocks plus two T frames used for the
synchronisation and two X idle frames. Each radio block including four basic
frames. The multiframe is used to time multiplex the GPRS and GSM logical
channels. The LLC layer frames are segmented within the radio blocks of the
RLC/MAC layer. Each radio block is transported by four consecutive Normal
bursts of the multiframe. The four Normal bursts have to be intended
as interleaved on four consecutive TDMA 4.615 ms frames. The resources
necessary to the GPRS service foresee an additional number of logical channels
supporting the transfer of radio blocks through the physical Packet Data Channel
(PDCH). GPRS logical channels have names and functional characteristics greatly
faithfully following those of the channels of the traditional GSM, though referred
to packets.

Two basic RLC/MAC block structures are used either for data transfer or for
control message transfer. TS 44.060, fig. 10.0a.2.1 shows a structure for EGPRS
data transfer including a RLC/MAC header and a RLC data block 1, optionally
followed by a RLC data block 2. TS 44.060, fig. 10.0a.3.1 shows a structure for
control message transfer including a MAC header and a RLC/MAC control block.
The different components of an RLC/MAC block carrying a GPRS RLC data block
or an RLC/MAC control block shall be assembled sequentially. Each component
consists of an integer number of octets. The assembling of components shall be
performed progressively, starting in octet number 1 of the physical block.
Fig.2 shows a BSS block connected to a plurality of MS blocks. The BSS block
includes a BSC block and some BTS blocks. The BSC block includes in turn a
block called LLC Layer, a Physical Layer block, a TBF MANAGER block, and a
Scheduler block. The BSC is connected to the SGSN block of the Figure through a
Gb interface. The LLC Layer has a bi-directional connection with the TBF
MANAGER that, in turn has a bi-directional connection with the Scheduler block
and with the Physical Layer. The BSC is charged with the majority of the
operations dealing with TBFs, and the exchange of relevant RR messages on the
Abis interface. The LLC Layer sends to the TBF MANAGER the LLC frames for
downlink buffered connections, and receives from the TBF MANAGER
the LLC frames for the uplink connections. The TBF MANAGER sends to the
Physical Layer the RLC/MAC radio blocks with the associated USF multiplexed for
TDMA on each time slot. The Physical Layer sends the TBF Manager the
RLC/MAC radio blocks coming indication of number of radio blocks to transmit for
each DL_TBF connection and UL_TBF connection. The Scheduler, in its turn,
includes a Downlink and an Uplink Scheduler providing the TBF MANAGER with
scheduling information.

The purpose of the packet access procedure is to establish a TBF to support the
transfer of upper-layer PDUs in the direction from the mobile station to the
network. Packet access shall be done on PCCCH, as defined in this clause, if a
PCCCH exists. Otherwise, packet access shall be done on CCCH, as defined in
3GPP TS 44.018. The packet access can be done in either one phase (clause
7.1.2) or in two phases (clauses 7.1.2 and 7.1.3).
According to TS 44.060, paragraph 7.1.2, the mobile station shall initiate the one
phase packet access procedure by scheduling the sending of PACKET CHANNEL
REQUEST messages on the PRACH channel corresponding to its PCCCH_GROUP
and simultaneously leaving the packet idle mode. The mobile station shall use
the last access parameters received on PBCCH. The PACKET CHANNEL REQUEST
messages are sent on PRACH and contain an indication (establishment cause) of
the type of access and parameters required to indicate the mobile station's
demand of radio resource (frequency, timeslot, code, etc.). On receipt of a
PACKET CHANNEL REQUEST message, the network may assign a radio resource
on one or more PDCHs to be used by the mobile station for the TBF in GPRS TBF
mode. On receipt of an EGPRS PACKET CHANNEL REQUEST message, the
network may assign a radio resource on one or more PDCHs to
be used by the mobile station for the TBF in EGPRS TBF mode or GPRS TBF
mode. If the dynamic allocation medium access mode is used, the network shall
include the USF values allocated for PDCHs in the PACKET UPLINK ASSIGNMENT
message.

In fig.3, the previous one phase access procedure is modified according to a first
embodiment of the invention aimed to solve the problem of the early
establishment of an uplink TBF. With reference to fig.3, the PACKET CHANNEL
REQUEST message includes an additional establishment cause called "Early
establishment cause" that is linked to those situations the cause is needed, for
example the delay-sensitive real-time applications. The network, after having
allocated the requested PDCH resources to the mobile station, predisposes it to
receive dummy control block from the mobile, station In alternative the network
predisposes it not to receive any messages if the support of this capability is
indicated by the network. To this aim the network schedules the uplink
transmission instants by conveying relevant USF flags in proper downlink
messages, i.e. UPLINK ACK/NACK messages. The mobile station handshakes
DUMMY control blocks to the USFs until an actual packet data is coming from the
application. According to TS 44.060, paragraph 7.1.3, when the TBF is
established using two phase access: in the first phase of a two phase access in a
cell provided with a PCCCH, the same procedures
as for one phase access are used until the network sends a
PACKET UPLINK ASSIGNMENT message including a Single Block Allocation
structure or Multi Block Allocation structure, denoting two phase access to the
mobile station. The Multi Block Allocation structure may be used only if the
mobile station has EGPRS capability (i.e. the network received an EGPRS PACKET
CHANNEL REQUEST message from the mobile station). In the PACKET UPLINK
ASSIGNMENT message, the network reserves a limited resource on one PDCH to
the mobile station where the mobile station may transmit a PACKET RESOURCE
REQUEST message and optionally an ADDITIONAL MS RADIO ACCESS
CAPABILITIES message.

In fig.4 the two phase access procedure is modified according to a second
embodiment of the invention, also aimed to solve the problem of the early
establishment of an uplink TBF. With reference to fig.4, the mobile sends a
PACKET CHANNEL REQUEST message to the network, and receives back a
PACKET UPLINK mobile replies to the PACKET UPLINK ASSIGNMENT message
with a PACKET RESOURCE REQUEST message including an Extended uplink TBF
information. The network establishes an Uplink TBF indicating the requesting
mobile station and handshakes USF flags as in the previous fig.3
Although the invention has been described with particular reference to some
preferred embodiments, it will be evident to those skilled in the art, that the
present invention is not limited thereto, but further variations and modifications
may be applied without departing from the scope thereof.
USED ACRONYMS
3GPP - 3rd Generation Partnership Program
BSC - Base Station Controller
BSS - Base Station Subsystem
BTS - Base Transceiver Station
CCCH - Common Control Channel
EDGE - Enhanced Data rates for GSM Evolution
EGPRS - Enhanced GPRS
EIR - Equipment Identity Register
GERAN - GSM/EDGE Radio Access Network
GGSN - Gateway GSN
GMSC - Gateway MSC
GP - GERAN Plenary

GPRS - General Packet Radio Service
GSM - Global System for Mobile communications
IWMSC - InterWorking
LLC - Logical Link Control
MAC - Medium Access Protocol
MS - Mobile Station
MSC - Message Switching Centre
MT - Mobile Terminated
PBCCH - Packet Broadcast Control Channel
PCCCH - Packet Common Control Channel
PDCH - Packet Data Channel
PDU - Protocol Data Unit
PLMN - Public Land Mobile Network
PoC - Push-to-Talk over Cellular
PRACH - Physical Random Access Channel
CR - Change Request
RLC - Radio Link Control
SC - Service Centre
SGSN - Service GPRS Support Node
SMS - Short Message Service
TBF - Temporary Block Flow
TE - Terminal Equipment
TFI - TBF identifier
TSG - Technical Specification Group
UMTS - Universal Mobile Telecommunication System
USF - Uplink State Flag
VLR - Visitor Location Register
VoIP - Voice over IP

WE CLAIM :
1. Method for establishing a temporary buffer, called TBF, for packet data to
be transmitted on a packet data channel from a mobile station (MS) uplink
to a wireless network (BSS) it belongs to, characterized in that the
method comprises the steps of:
a) transmitting by the mobile station (MS) to the network (BSS) a request for
the establishment of an early uplink TBF even if the mobile station has not
data to transmit;
b) establishing by the network an early uplink TBF to said mobile station
(MS);
c) scheduling by the network (BSS) permissions, also called USF, to the
mobile station (MS) to transmit packet data from said early uplink TBF;
d) transmitting dummy packets from said early uplink TBF by said mobile
station (MS) as the proper USFs are detected and it has not data to
transmit;
e) transmitting available actual packet data from said early uplink TBF by said
mobile station (MS) as the proper USFs are detected.
2. The method as claimed in claim 1, wherein after said step c) the network
(BSS) predisposes it to receive dummy control block from that mobile
station (MS).

3. The method as claimed in claim 2, wherein said dummy packets are
discarded locally by the network (BSS).
4. The method as claimed in any of claim 1 to 3 wherein said request for the
establishment an early uplink TBF is included in a PACKET CHANNEL
REQUEST message of one phase packet access.
5. The method as claimed in claim 4, wherein the network (BSS) after step
b) transmits a PACKET UPLINK ASSIGNMENT message to the mobile
station (MS).
6. The method as claimed in any of claim 1 to 3, wherein said step a) is
preceded by the following steps of two phase packet access:

- transmitting, by the mobile station (MS), a PACKET CHANNEL REQUEST
message to the network (BSS);
- transmitting, by the network (BSS), a PACKET UPLINK ASSIGNMENT
message to the mobile station (MS)

7. The method as claimed in claim 6, wherein said request for the establishment
an early uplink TBF is included in a PACKET RESOURCE REQUEST message.
8. The method as claimed in any of claim 1 to 7, wherein said mobile station
(MS) instead of transmitting said dummy packets does not transmit any
packets if the support of this capability is indicated by the network.

9. The method as claimed in any of claim 1 to 8, wherein said early uplink TBF
establishment is foreseen for delay-sensitive transmissions.
10. The method as claimed in any of claim 1 to 9, wherein wireless network
(BSS) is standardized by 3GPP.

ABSTRACT

TITLE "METHOD FOR ESTABLISHING A TEMPORARY BUFFER FOR
PACKET DATA TRANSMITTED FROM A MOBILE STATION TO
A WIRELESS NETWORK"
The invention relates to a method for establishing a temporary buffer,
called TBF, for packet data to be transmitted on a packet data channel
from a mobile station (MS) uplink to a wireless network (BSS) it belongs
to, characterized in that the method comprises the steps of : a)
transmitting by the mobile station (MS) to the network (BSS) a request for
the establishment of an early uplink TBF even if the mobile station has not
data to transmit; b) establishing by the network an early uplink TBF to
said mobile station (MS); c) scheduling by the network (BSS)
permissions, also called USF, to the mobile station (MS) to transmit packet
data from said early uplink TBF; d) transmitting dummy packets from said
early uplink TBF by said mobile station (MS) as the proper USFs are
detected and it has not data to transmit; e) transmitting available actual
packet data from said early uplink TBF by said mobile station (MS) as the
proper USFs are detected.

METHOD FOR ESTABLISHING A TEMPORARY BUFFER FOR PACKET DATA TRANSMITTED FROM A MOBILE STATION TO A WIRELESS NETWORK

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