Title of Invention	METHOD OF MONITORING CONTROL CHANNEL IN WIRELESS COMMUNICATION SYSTEM
Abstract	A method of monitoring a control channel in a wireless communication system includes monitoring a physical down-link control channel (PDCCH) during a monitored duraticn, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. By monitoring a control channel during a DRX period, battery consumption of a user equipment can be reduced and an operation time of the user equipment can be increased.

Title of Invention

METHOD OF MONITORING CONTROL CHANNEL IN WIRELESS COMMUNICATION SYSTEM

Abstract

A method of monitoring a control channel in a wireless communication system includes monitoring a physical down-link control channel (PDCCH) during a monitored duraticn, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. By monitoring a control channel during a DRX period, battery consumption of a user equipment can be reduced and an operation time of the user equipment can be increased.

Full Text	Description METHOD OF MONITORING CONTROL CHANNEL IN WIRELESS COMMUNICATION SYSTEM Technical Field [1] The present invention relates to wireless communication, and more particularly, to a method of reducing battery consumption of a user equipment in a wireless com- munication system. Background Art [2] A conventional wide code division multiple access (WCDMA)-based wireless com- munication method is a very effective wireless transmission method in which voice- based data is transmitted at a low speed and a soft handover is taken into consideration, but is ineffective when data is transmitted at a high speed in a multi-path fading en- vironment. An evolved-universal mobile telecommunications system (E-UMTS) proposes a downlink transmission speed of about 100Mbps. In the E-UMTS, as a multiple access technique, orthogonal frequency division multiplexing (OFDM) is mainly concerned in downlink, and a discrete Fourier transform spread OFDM (DFT-S-OFDM) is mainly concerned in uplink in order to minimize a peak- to-average-power-ratio (PAPR) of a user equipment (UE). [3] FIG. 1 shows a structure of a wireless communication system. The wireless com- munication system may be have a network stmcture of an E-UMTS. The E-UMTS may be referred to as a long-term evolution (LTE) system. The wireless com- munication system can be widely deployed to provide a variety of communication services, such as voices, packet data, etc. [4] Referring to FIG. 1, a E-UMTS is classified into an evolved-UMTS terrstrial radio access network (E-UTRAN) and an evolved packet core (EPC). The E-UTRAN includes at least one base station (BS) 20. A user equipment (UE) 10 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc. The BS 20 is generally a fixed station that conamunicates with the UE 10 and may be referredto as another terminology, such as an evolved node-B(eNB), a base transceiver system (BTS), an access point, etc. There are one or more cells within the coverage of the BS 20. [5] Interfaces for transmitting user traffic or control traffic may be used between the BSs 20. Hereinafter, downlink is defined as communication from the BS 20 to the UE 10, and uplink is defined as communication from the UE 10 to the BS 20. [6] The BS 20 provides the UE 10 with an end-to-end point of a user plane and a control plane. The BSs 20 are interconnected by means of an X2 interface, and may have a meshed network structure in which the X2 interface always exists between the neighboring BSs 20. [7] The BSs 20 are also connected by means of an SI interface to the EPC, more specifically, to an access gateway (aGW) 30. The aGW 30 provides an end-to-end point for a session and mobility management fimction of the UE 10. The S1 interface may be provided between the BS 20 and the aGW 30 so that a plurality of nodes can be interconnected in a many-to-many manner. The aGW 30 can be classified into a part for processing user traffic and a part for processing control traffic. In this case, for inter-communication, a new interface may be used between an aGW for processing new user traffic and an aGW for processing new control traffic. The aGW 30 is also referred to as a mobility management entity/user plane entity (MME/UPE). [8] Layei's of a radio intert'ace protocol between a UE and a network can be classified into L1 layer (a first layer), L2 layer (a second layer), and L3 layer (a third layer) based on the lower three layers of the open system interconnection (OSI) model that is well- known in a communication system. A physical layer belongs to the first layer and provides an information transfer service on a physical channel. A radio resource control (RRC) layer belongs to the third layer and serves to control radio resources between the UE and the network. The UE and the network exchange RRC messages via the RRC layer. The RRC layer may be located in network nodes (i.e., a BS, an aGW, etc.) in a distributed manner, or may be located only in the BS or the aGW. [9] The radio interface protocol horizontally includes a physical layer, a data link layer, and a network layer, and vertically includes a user plane for data infonnation transfer and a control plane for control signaling delivery. [10] FIG. 2 is a diagram showing a control plane of a radio interface protocol. FIG. 3 is a diagram showing a user plane of the radio interface protocol. In FIGs. 2 and 3, a structure of the radio interface protocol between a UE and an E-UTRAN is based on the third generation partnership project (3GPP) wireless access network standard. [11] Referring to FIGs. 2 and 3, a physical layer belonging to a first layer provides an upper layer with an information transfer service on a physical channel. The physical layer is coupled with a media access control (MAC) layer, i.e., an upper layer of the physical layer, via a transport channel. Data is transferred between the MAC layer and the physical layer on the transport channel. In addition, data is transferred between different physical layers, i.e., between physical layers of a transmitting side and a receiving side. [12] The MAC layer in a second layer provides services to a radio link control (RLC) layer, i.e., an upper layer of the MAC layer, via a logical channel. The RLC layer in the second layer supports reliable data transfer. Functions of the RLC layer can be im- plemented as a function block included in the MAC layer. In this case, as indicated by a dotted line, the RLC layer may not exist. [13] A packet data convergence protocol (PDCP) belonging to the second layer perfonns a header compression function. When transmitting an Internet protocol (IP) packet such as an IPv4 packet or an IPv6 packet, the header of the IP packet may contain relatively large and unnecessary control information. The PDCP layer reduces the header size of the IP packet so as to efficiently transmit the IP packet through a radio interface. [14] An RRC layer belonging to a third layer is defined only in the control plane. The RRC layer serves to control the logical channel, the transport channel, and the physical channel in association with configuration, reconfiguration, and release of radio bearers (RBs). An RB is a service provided by the second layer for data transmission between the UE and the E-UTRAN. The RB is a logical path provided by the first and second layers of the radio protocol to deliver data between the UE and the E-UTRAN. In general, when the RB is established, characteristics of radio protocol layers and channels required to provide a specific service are defined, and all specific parameters and operation methods are stermined. [15] A downlink transport channel transmits data from the network to the UE. Examples of the downlink transport channel include a broadcast channel (BCH) for transmitting system information and a downlink-shared channel (DL-SCH) for transmitting user traffic or control messages. User traffic of downlink multicast or broadcast services or control messages can be transmitted on the DL-SCH or a downlink multicast channel (MCH). An uplink transport channel transmits data from the UE to the network. Examples of the uplink transport channel include a random access channel (RACH) for transmitting initial control messages and an uplink-shared channel (UL-SCH) for transmitting user traffic or control messages. A paging channel (PCH) may be provided to deliver paging information. [16] FIG. 4 shows an example of mapping of logical channels onto physical channels in a WCDMA system. The section 6.1 of 3GPP TS 25.211 V6.7.0 (2005-12) "Technical Specification Group Radio Access Network; Physical channels and mapping of transport channels onto physical channels (FDD) (Release 6)" can be incorporated herein by reference. [17] Referring to FIG. 4, logical channels are a dedicated channel (DCH), an enhanced dedicated channel (E-DCH), a random access channel (RACH), a broadcast channel (BCH), a forward access channel (FACH), a paging channel (PCH), and a high speed downlink shared channel (HS-DSCH). The logical channels are mapped to various physical channels. [18] FIG. 5 shows an example of mapping of logical channels onto physical channels in an E-UTRAN. The section 5.3.1 of 3GPP TS 36.300 VO.9.0 (2007-03) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN): Overall description; Stage 2 (Release 8)" can be incorporated herein by- reference. [19] Refening to FIG. 5, downlink transport channels (i.e., a DL-SCH, a PCH. and an MCH) except for a BCH are mapped to a physical downlink shared channel (PDSCH). A control channel among downlink physical channels may be a physical downlink control channel (PDCCH). Comparing FIG. 4 and HG. 5, unlike the WCDMA system using various physical channels, the E-UTRAN uses only two downlink physical channels, i.e., the PDSCH for traffic data and the PDCCH for a control signal. [20] In order to receive the PDSCH, a UE first has to monitor the PDCCH. After suc- cessfully decoding the PDCCH, the UE can receive the PDSCH by using scheduling information included in the PDCCH. However, since the PDCCH is an almost unique control channel, the PDCCH is transmitted every transmission time interval (TTI). The TTI is a unit of scheduling performed by a BS. The TTI is defined as a time for tran smitting one sub-frame. For example, 1 TTI may be 1ms. [21] Unlike the WCDMA system capable of monitoring only a control channel designed for a specific purpose, the UE in the E-URTAN needs to monitor the PDCCH every TTI in order to check the scheduling information of the UE. However, when the scheduling information of the UE is checked every TTI, the UE may experience significant battery consumption due to a relatively short TTI length. Disclosure of Invention Technical Problem [22] A method is sought for monitoiing a control channel to reduce batteiy consumption of a user equipment. Technical Solution [23] In an aspect, a method of monitoring a conti-ol channel in a wireless communication system is provided. The method includes monitoring a physical downlink control channel (PDCCH) during a monitored duration, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. [24] In another aspect, a method of monitoring a control channel in a wireless com- munication system is provided. The method includes monitoring a PDCCH during a monitored duration, wherein the monitored duration is a part of a DRX period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration, and monitoring the PDCCH during an extended period when the PDCCH is successfully decoded during the monitored duration. Advantageous Effects [25] By monitoring a control channel during a discontinuous reception (DRX) period, battery consumption of a user equipment (LIE) can be reduced in an evolved-universal mobile telecommunications system (E-UMTS), and an operation time of the UE can be increased. Brief Description of the Drawings [26] FIG. 1 shows a structure of a wireless communication system. [27] FIG. 2 is a diagram showing a control plane of a radio interface protocol. [28] FIG. 3 is a diagram showing a user plane of a radio inteface protocol. [29] FIG. 4 shows an example of mapping of logical channels onto physical channels in a wide code division multiple access (WCDMA) system. [30] FIG. 5 shows an example of mapping of logical channels onto physical channels in an evolved-universal mobile telecommunications system (E-UMTS). [31] FIG. 6 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [32] FIG. 7 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [33] FIG. 8 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [34] FIG. 9 shows an example of a method of monitoring a control channel accoi'ding to an embodiment of the present invention. [35] FIG. 10 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [36] FIG. 11 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [37] FIG. 12 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [38] FIG. 13 is a block diagram showing constitutional elements of a user equipment. Mode for the Invention [39] A user equipment (UE) monitors a downlink control channel during a monitored duration which exists for each discontinuous reception (DRX) period. The monitored duration is defined by the number of consecutive transmission time intervals (TTIs). [40] Every DRX period, the UE detects whether scheduling information of the UE itself is transmitted on a downlink control channel during a specific checking period. Upon detecting the scheduling information, the UE receives data by using the scheduling in- formation. [41 ] During the monitored duration, when no scheduling information of the UE is received from a base station (BS), the UE does not monitor the downlink control channel during the remaining cycles of the DRX period. [42] When the BS establishes the DRX period of the control channel, every DRX period, the UE monitors the control channel only during the monitored duration, and stops monitoring of the control channel during a non-monitored duration. [43] When the scheduling information of the UE is detected on the downlink control channel, that is, when decoding of the downlink control channel is successful, the UE can continuously monitor the downlink control channel during an extended period even after the monitored duration is over. [44] When the scheduling information of the UE is detected on the downlink control channel, the UE can enter a continuous reception mode. In the continuous reception mode, the UE can continuously receive the downlink control channel until a specific condition is satisfied. [45] There may be an occasion in which, after the UE enters the continuous reception mode from a discontinuous reception mode, the UE re-enters the discontinuous reception mode from the continuous mode. This occasion may occur when the UE does not detect the scheduling information of the UE on the downlink control channel during a specific time period after the UE enters the continuous reception mode. [46] Such an occasion may also occur when the UE receives from the BS an instruction, which allows the UE to enter the discontinuous reception mode, after the UE enters the continuous reception mode. [47] When the scheduling infomiation is detected within the monitored duration, the UE can extend the monitored duration. The UE can monitor the downlink control channel for the extended time period even if the monitored duration is over. [48] The downlink control channel may be any one of a paging channel and L1/L2 control channel which delivers information regarding on radio resource allocation. The L1/L2 control channel is also referredto as a physical downlink control channels (PDCCH). The downlink control channel carries resource allocation information on which the UE receives data on a downlink shared channel (DL-SCH) or on which the UE transmits data on an uplink shared channel (UL-SCH). The downlink control channel carries scheduling assignment information of the UE. Scheduling assignment may be uplink assignment and/or downlink assignment. When the downlink control channel is successful decoded, the UE can recognize that the scheduling information of the UE is being delivered on the downlink control channel. [49] The BS can inform the UE of information which indicates whether DRX is configured to monitor the control channel, information on a DRX period and a monitored duration, information on an extended period, etc. [50] The BS can infonn the UE of configuration information indicating a minimum possible number of sub-frames (or a time duration) which follow an n-th sub-frame and in which the UE has to monitor the downlink control channel. [51] The BS can inform the UE of information (i.e., configuration information of the DRX period) on a repetition period of the monitored duration in which the UE monitors the downlink control channel. [52] The BS may monitor the control channel only during the monitored duration of the DRX period, and inform the UE of DRX configuration infonnation indicating whether to stop monitoring during the non-monitored duration. [53] Upon detecting the scheduling information of the UE. the BS can infom the UE of information on an extended period in which the DRX period is inactivated and the downlink control channel is continuously monitored. [54] Information on the monitored duration or the extended period may be represented by a sub-frame to which the downlink control channel is allocated. The information on the monitored duration or the extended period may be represented by the number of consecutive sub-frames to be monitored. Alternatively, the infonnation on the monitored duration or the extended period may be represented by the number of consecutive TTIs for monitoring the downlink control channel. For example, the monitored duration is indicated by only one sub-frame, the UE monitors the downlink control channel only in the one sub-frame. Therefore, if there is data or control in- fonnation to be transmitted to the UE, the BS has to inform this only on the downlink control channel allocated to the sub-frame belonging to the monitored duration. However, when the system experiences power shortage, or when a large amount of data has to be transmitted to another user, the BS has to give up data transmission of another user in order to infonn the UE of the existence of data. That is, when only one sub-frame is included in the monitored duration of the UE, the BS experiences significant limits in utilizing radio resources. Therefore, it is effective to define a plurality of consecutive sub-frames (or a plurality of TTIs) in the monitored duration or the extended period. [55] FIG. 6 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [56] Referring to FIG. 6, a DRX period has a length of 7 TTIs, and a monitored duration has a length of 2 TTIs. The remaining cycles of the DRX period, that is. a non- monitored duration, have a length of 7 TTIs. The length of the monitored duration is defined by the number of consecutive TTIs. The TTI is a unit of scheduling radio resources. The TTI is a time required to transmit one sub-frame. At least one PDCCH and at least one physical downlink shared channel (PDSCH) can be allocated to one sub-frame. [57] A BS can inform a UE of the length of the monitored duration. The monitored duration is a part of the DRX period. The DRX period specifies periodic repetition of the monitored duration followed by the non-monitored duration. [58] Eveiy DRX period, the UE monitors at least one PDCCH during the monitored duration. The PDCCH is a control channel carrying scheduling assignment (e.g., uplink assignment or downlink assignment). If decoding is not successfully performed on the PDCCH during the monitored duration, the UE stops the monitoring of the PDCCH during the non-monitored duration. The BS can infonn the UE of information (i.e., DRX configuration) indicating whether the PDCCH is monitored during the non- monitored duration. [59] The UE monitors the PDCCH during the monitored duration. The UE may wake up only during the monitored duration to perform uplink transmission or downlink transmission. For example, the UE may periodicaUy report a channel quality indicator (CQI) to the BS during the monitored duration. [60] FIG. 7 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [61] Refening to FIG. 7, every DRX period, a UE monitors a PDCCH during a monitored duration. When decoding is successfully performed on the PDCCH during the monitored duration, that is, when data to be transmitted to the UE is detected, data on a DL-SCH is received by using information indicated on the PDCCH. [62] When the UE successfully receives the PDCCH on which uplink assignment or downlink assignment is indicated during the monitored duration, the PDCCH can be monitored during an extended period. In this example, data is indicated at 2 TTIs, and the monitored duration is further extended. If the PDCCH is not successfully decoded during the extended period, the UE re-enters the DRX period. The BS can inform the UE of infonnation on the extended period. [63] FIG. 8 shows an example of a method of monitoring a control channel according to an embodiment of the present mvention. [64] Refening to FIG. 8, a DRX period is divided into an on-period and an off-period. The on-period is a period in which a UE monitors a PDCCH. The off-period is a period in which the UE stops monitoring the PDCCH and enters DRX sleep mode. A BS can inform the UE of information on the on-period or the off-period. When the UE suc- cessfully receives the PDCCH during the off-period, downlink data can be recei\ed on a DL-SCH. [65] The on-period is defined by the number of consecutive TTIs. The off-period may also be defined by the number of consecutive TTIs. [66] The on-period and the off-period may have fixed lengths. That is, during the on- period, the UE may do not change the length of the on-period or the off-period even if scheduling information is detected on the PDCCH. In this case, the on-period and the off-period of the UE have invariable lengths. Therefore, when the on-period is over, the UE transitions to the off-period regardless of whether transmission information is received during the on-period. That is, although the PDCCH has been successfully received at the first 2 TTIs, the UE does not monitor the PDCCH during the off-period, starting from a time point when the off-period begins. [67] FIG. 9 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [68] Refening to FIG. 9, a BS instructs a UE to skip an off-period during a specific DRX period. Scheduling information may not be received within a previous on-period due to a large amount of data or control information to be sent from the BS to the UE. In this case, it can be instructed such that the off-period of the specific DRX period is skipped during the specific DRX period, and thus a current mode can be switched to a continuous reception mode only during the specific DRX period. Alternatively, in this case, it can be instructed such that the UE switches the current mode to continuously receive data by stopping DRX configuration. "When the instruction for skipping the off- period is received, the UE does not enter the off-period and performs an operation in the on-period amounting to the skipped periods of time. [69] FIG. 10 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [70] Refening to FIG. 10, when a PDCCH is successfully decoded during an on-period of a specific DRX period, the PDCCH can be further monitored for a time period amounting to an extended period. The extended period is defined by the number of consecutive TTIs for monitoring the PDCCH when downlink transmission is expected. Herein, the PDCCH is successfully decoded during an on-period having a length of 2 TTIs, and the PDCCH is monitored during an extended period having a length of 2 TTIs. Therefore, a total length of the monitored duration is 4 TTIs. [71] While receiving the downlink control channel during the on-period, when scheduling assignment (e.g., downlink assignment or uplink assignment) of the UE is detected on the downlink control channel, the UE further monitors the PDCCH for a time period amounting to the extended peiiod. If the PDCCH is not successfully decoded during the extended period, the UE re-enters the DRX period. [72] The BS can instruct the UE to switch to a continuous reception mode continuously during an on-period in a next DRX period, or sv\itch to the continuous reception mode only during se\eral DRX periods, or extends a length of the on-period. Even after the UE switches to the continuous reception mode, the BS can instruct the UE to transition to the off-period. While staying in the continuous reception mode, when the BS instructs the UE to transition to the off-period, the UE ends the continuous reception mode and transitions to the off-period. [73] FIG. 11 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [74J Referring to FIG. 11, when a PDCCH is successfully decoded during an on-period, a UE inactivates an off-period, and further monitors the PDCCH for a time period amounting to an extended period. A BS can instruct the UE to transition to the off- period during the extended period. That is, the UE can enter a DRX period directly under the instruction of the BS instead of entering the DRX period after the extended period is over. [75] FIG. 12 shows an example of a method of monitoring a control channel according to an embodiment of the present invention. [76] Referring to FIG. 12, when data is indicated, a plurality of extended periods exist. That is, when a PDCCH is successfully decoded during an on-period, a UE further monitors the PDCCH during an extended period. If the PDCCH is successfully decoded only during the extended period, the UE continuously monitors the PDCCH during an additionally extended period. When data is indicated during an on-period, the PDCCH can be continuously monitored during a plurality of extended periods after the on-period of a corresponding DRX period is over. [77] After receiving the data indication, the UE continuously monitors the PDCCH during the extended period in order to receive subsequent downlink transmission. When data indication is received again, the UE continuously monitors again the PDCCH during another extension period. If existence of data is no longer indicated during the additional extension period, the UE re-enters the DRX period. [78] Although the control channel is transmitted at a relatively short transmission period, the UE monitors the control channel only during the on-period and does not monitor the control channel during the off-period. The BS can inform the UE of DRX con- figuration by using a media access control (MAC) message or a radio resource control (RRC) message. When the control channel is monitored by using a DRX method, battery consumption of the UE can be reduced. [79] FIG. 13 is a block diagram showing constimtional elements of a UE. A UE 50 includes a processor 51, a memory 52, a radio frequency (RF) unit 53, a display unit 54, and a user interface unit 55. The memoiy 52 is coupled to the processor 51 and stores an operating system, applications, and general files. The display unit 54 displays a variety of information of the UE 50 and may use a well-known element such as a liquid crystal display (LCD), an organic light emitting diode (OLED). etc. The user interface unit 55 can be configured with a combination of well-known user interfaces such as a keypad, a touch screen, etc. The RF unit 53 is coupled to the processor 51 and transmits and/or receives radio signals. [80] Layers of the radio interface protocol are implemented in the processor 51. The processor 51 provides a control plane and a user plane. A monitoring function of the control channel can be implemented in the processor 51. [81J The steps of a method described in connection with the embodiments disclosed herein may be implemented by hardware, software or a combination thereof. The hardware may be implemented by an application specific integrated circuit (ASIC) that is designed to perform the above function, a digital signal processing (DSP), a pro- grammable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, the other electronic unit, or a combination thereof A module for performing the above function may implement the software. The software may be stored in a memory unit and executed by a processor. The memory unit or the processor may employ a variety of means that is well known to those skilled in the art. [82] As the present invention may be embothed in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing de- scription, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims. Therefore, all changes and modi- fications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are intended to be embraced by the appended claims. Claims [1] 1. A method of monitoring a control channel in a wireless communication system, the method comprising: monitoring a physical downlink control channel (PDCCH) during a monitored duration, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. [2 J The method of claim 1, further comprising: receiving a DRX configuration that allows to stop monitoring the PDCCH during the non-monitored duration. [3] The method of claim 1, wherein the monitored duration is defined by the number of consecutive transmission time intervals (TTIs). 14] The method of claim 1, further comprising: transmitting periodic channel quality indicator (CQI) reports during the monitored duration. [5] The method of claim 1, wherein the PDCCH carries scheduling assignment. [6] The method of claim 1, further comprising: monitoring the PDCCH during an extended period when successfully decoding the PDCCH indicating downlink assignment or uplink assignment during the monitored duration, the extended period defined by the number of consecutive TTIs. [7] The method of claim 6, wherein the extended period is signaled by a base station. [8] The method of claim 6, further comprising: re-entering the DRX period when the PDCCH is not decoded during the extended period. [9] A method of monitoring a control channel in a wireless communication system, the method comprising: monitoring a PDCCH during a monitored duration, wherein the monitored duration is a part of a DRX period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration: and monitoring the PDCCH during an extended period when the PDCCH is suc- cessfully decoded during the monitored duration. [10] The method of claim 9, further comprismg: stopping monitoring the PDCCH during the non-monitored duration when the PDCCH is not successfully decoded during the monitored duration. [11] The method of claim 9, wherein the monitored duration and the extended period are signaled by a base station. [12] the method of claim 9, further comprising: re-entering the DRX period when the PDCCH is not decoded during the extended period. A method of monitoring a control channel in a wireless communication system includes monitoring a physical down-link control channel (PDCCH) during a monitored duraticn, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. By monitoring a control channel during a DRX period, battery consumption of a user equipment can be reduced and an operation time of the user equipment can be increased.

Full Text

Description
METHOD OF MONITORING CONTROL CHANNEL IN
WIRELESS COMMUNICATION SYSTEM
Technical Field
[1] The present invention relates to wireless communication, and more particularly, to a
method of reducing battery consumption of a user equipment in a wireless com-
munication system.
Background Art
[2] A conventional wide code division multiple access (WCDMA)-based wireless com-
munication method is a very effective wireless transmission method in which voice-
based data is transmitted at a low speed and a soft handover is taken into consideration,
but is ineffective when data is transmitted at a high speed in a multi-path fading en-
vironment. An evolved-universal mobile telecommunications system (E-UMTS)
proposes a downlink transmission speed of about 100Mbps. In the E-UMTS, as a
multiple access technique, orthogonal frequency division multiplexing (OFDM) is
mainly concerned in downlink, and a discrete Fourier transform spread OFDM
(DFT-S-OFDM) is mainly concerned in uplink in order to minimize a peak-
to-average-power-ratio (PAPR) of a user equipment (UE).
[3] FIG. 1 shows a structure of a wireless communication system. The wireless com-
munication system may be have a network stmcture of an E-UMTS. The E-UMTS
may be referred to as a long-term evolution (LTE) system. The wireless com-
munication system can be widely deployed to provide a variety of communication
services, such as voices, packet data, etc.
[4] Referring to FIG. 1, a E-UMTS is classified into an evolved-UMTS terrstrial radio
access network (E-UTRAN) and an evolved packet core (EPC). The E-UTRAN
includes at least one base station (BS) 20. A user equipment (UE) 10 may be fixed or
mobile, and may be referred to as another terminology, such as a mobile station (MS),
a user terminal (UT), a subscriber station (SS), a wireless device, etc. The BS 20 is
generally a fixed station that conamunicates with the UE 10 and may be referredto as
another terminology, such as an evolved node-B(eNB), a base transceiver system
(BTS), an access point, etc. There are one or more cells within the coverage of the BS
20.
[5] Interfaces for transmitting user traffic or control traffic may be used between the
BSs 20. Hereinafter, downlink is defined as communication from the BS 20 to the UE
10, and uplink is defined as communication from the UE 10 to the BS 20.
[6] The BS 20 provides the UE 10 with an end-to-end point of a user plane and a

control plane. The BSs 20 are interconnected by means of an X2 interface, and may
have a meshed network structure in which the X2 interface always exists between the
neighboring BSs 20.
[7] The BSs 20 are also connected by means of an SI interface to the EPC, more
specifically, to an access gateway (aGW) 30. The aGW 30 provides an end-to-end
point for a session and mobility management fimction of the UE 10. The S1 interface
may be provided between the BS 20 and the aGW 30 so that a plurality of nodes can be
interconnected in a many-to-many manner. The aGW 30 can be classified into a part
for processing user traffic and a part for processing control traffic. In this case, for
inter-communication, a new interface may be used between an aGW for processing
new user traffic and an aGW for processing new control traffic. The aGW 30 is also
referred to as a mobility management entity/user plane entity (MME/UPE).
[8] Layei's of a radio intert'ace protocol between a UE and a network can be classified
into L1 layer (a first layer), L2 layer (a second layer), and L3 layer (a third layer) based
on the lower three layers of the open system interconnection (OSI) model that is well-
known in a communication system. A physical layer belongs to the first layer and
provides an information transfer service on a physical channel. A radio resource
control (RRC) layer belongs to the third layer and serves to control radio resources
between the UE and the network. The UE and the network exchange RRC messages
via the RRC layer. The RRC layer may be located in network nodes (i.e., a BS, an
aGW, etc.) in a distributed manner, or may be located only in the BS or the aGW.
[9] The radio interface protocol horizontally includes a physical layer, a data link layer,
and a network layer, and vertically includes a user plane for data infonnation transfer
and a control plane for control signaling delivery.
[10] FIG. 2 is a diagram showing a control plane of a radio interface protocol. FIG. 3 is a
diagram showing a user plane of the radio interface protocol. In FIGs. 2 and 3, a
structure of the radio interface protocol between a UE and an E-UTRAN is based on
the third generation partnership project (3GPP) wireless access network standard.
[11] Referring to FIGs. 2 and 3, a physical layer belonging to a first layer provides an
upper layer with an information transfer service on a physical channel. The physical
layer is coupled with a media access control (MAC) layer, i.e., an upper layer of the
physical layer, via a transport channel. Data is transferred between the MAC layer and
the physical layer on the transport channel. In addition, data is transferred between
different physical layers, i.e., between physical layers of a transmitting side and a
receiving side.
[12] The MAC layer in a second layer provides services to a radio link control (RLC)
layer, i.e., an upper layer of the MAC layer, via a logical channel. The RLC layer in
the second layer supports reliable data transfer. Functions of the RLC layer can be im-

plemented as a function block included in the MAC layer. In this case, as indicated by
a dotted line, the RLC layer may not exist.
[13] A packet data convergence protocol (PDCP) belonging to the second layer perfonns
a header compression function. When transmitting an Internet protocol (IP) packet
such as an IPv4 packet or an IPv6 packet, the header of the IP packet may contain
relatively large and unnecessary control information. The PDCP layer reduces the
header size of the IP packet so as to efficiently transmit the IP packet through a radio
interface.
[14] An RRC layer belonging to a third layer is defined only in the control plane. The
RRC layer serves to control the logical channel, the transport channel, and the physical
channel in association with configuration, reconfiguration, and release of radio bearers
(RBs). An RB is a service provided by the second layer for data transmission between
the UE and the E-UTRAN. The RB is a logical path provided by the first and second
layers of the radio protocol to deliver data between the UE and the E-UTRAN. In
general, when the RB is established, characteristics of radio protocol layers and
channels required to provide a specific service are defined, and all specific parameters
and operation methods are stermined.
[15] A downlink transport channel transmits data from the network to the UE. Examples
of the downlink transport channel include a broadcast channel (BCH) for transmitting
system information and a downlink-shared channel (DL-SCH) for transmitting user
traffic or control messages. User traffic of downlink multicast or broadcast services or
control messages can be transmitted on the DL-SCH or a downlink multicast channel
(MCH). An uplink transport channel transmits data from the UE to the network.
Examples of the uplink transport channel include a random access channel (RACH) for
transmitting initial control messages and an uplink-shared channel (UL-SCH) for
transmitting user traffic or control messages. A paging channel (PCH) may be
provided to deliver paging information.
[16] FIG. 4 shows an example of mapping of logical channels onto physical channels in
a WCDMA system. The section 6.1 of 3GPP TS 25.211 V6.7.0 (2005-12) "Technical
Specification Group Radio Access Network; Physical channels and mapping of
transport channels onto physical channels (FDD) (Release 6)" can be incorporated
herein by reference.
[17] Referring to FIG. 4, logical channels are a dedicated channel (DCH), an enhanced
dedicated channel (E-DCH), a random access channel (RACH), a broadcast channel
(BCH), a forward access channel (FACH), a paging channel (PCH), and a high speed
downlink shared channel (HS-DSCH). The logical channels are mapped to various
physical channels.
[18] FIG. 5 shows an example of mapping of logical channels onto physical channels in

an E-UTRAN. The section 5.3.1 of 3GPP TS 36.300 VO.9.0 (2007-03) "Technical
Specification Group Radio Access Network; Evolved Universal Terrestrial Radio
Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network
(E-UTRAN): Overall description; Stage 2 (Release 8)" can be incorporated herein by-
reference.
[19] Refening to FIG. 5, downlink transport channels (i.e., a DL-SCH, a PCH. and an
MCH) except for a BCH are mapped to a physical downlink shared channel (PDSCH).
A control channel among downlink physical channels may be a physical downlink
control channel (PDCCH). Comparing FIG. 4 and HG. 5, unlike the WCDMA system
using various physical channels, the E-UTRAN uses only two downlink physical
channels, i.e., the PDSCH for traffic data and the PDCCH for a control signal.
[20] In order to receive the PDSCH, a UE first has to monitor the PDCCH. After suc-
cessfully decoding the PDCCH, the UE can receive the PDSCH by using scheduling
information included in the PDCCH. However, since the PDCCH is an almost unique
control channel, the PDCCH is transmitted every transmission time interval (TTI). The
TTI is a unit of scheduling performed by a BS. The TTI is defined as a time for tran
smitting one sub-frame. For example, 1 TTI may be 1ms.
[21] Unlike the WCDMA system capable of monitoring only a control channel designed
for a specific purpose, the UE in the E-URTAN needs to monitor the PDCCH every
TTI in order to check the scheduling information of the UE. However, when the
scheduling information of the UE is checked every TTI, the UE may experience
significant battery consumption due to a relatively short TTI length.
Disclosure of Invention
Technical Problem
[22] A method is sought for monitoiing a control channel to reduce batteiy consumption
of a user equipment.
Technical Solution
[23] In an aspect, a method of monitoring a conti-ol channel in a wireless communication
system is provided. The method includes monitoring a physical downlink control
channel (PDCCH) during a monitored duration, wherein the monitored duration is a
part of a discontinuous reception (DRX) period, the DRX period specifying the
periodic repetition of the monitored duration followed by a non-monitored duration.
[24] In another aspect, a method of monitoring a control channel in a wireless com-
munication system is provided. The method includes monitoring a PDCCH during a
monitored duration, wherein the monitored duration is a part of a DRX period, the
DRX period specifying the periodic repetition of the monitored duration followed by a
non-monitored duration, and monitoring the PDCCH during an extended period when

the PDCCH is successfully decoded during the monitored duration.
Advantageous Effects
[25] By monitoring a control channel during a discontinuous reception (DRX) period,
battery consumption of a user equipment (LIE) can be reduced in an evolved-universal
mobile telecommunications system (E-UMTS), and an operation time of the UE can be
increased.
Brief Description of the Drawings
[26] FIG. 1 shows a structure of a wireless communication system.
[27] FIG. 2 is a diagram showing a control plane of a radio interface protocol.
[28] FIG. 3 is a diagram showing a user plane of a radio inteface protocol.
[29] FIG. 4 shows an example of mapping of logical channels onto physical channels in
a wide code division multiple access (WCDMA) system.
[30] FIG. 5 shows an example of mapping of logical channels onto physical channels in
an evolved-universal mobile telecommunications system (E-UMTS).
[31] FIG. 6 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[32] FIG. 7 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[33] FIG. 8 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[34] FIG. 9 shows an example of a method of monitoring a control channel accoi'ding to
an embodiment of the present invention.
[35] FIG. 10 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[36] FIG. 11 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[37] FIG. 12 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[38] FIG. 13 is a block diagram showing constitutional elements of a user equipment.
Mode for the Invention
[39] A user equipment (UE) monitors a downlink control channel during a monitored
duration which exists for each discontinuous reception (DRX) period. The monitored
duration is defined by the number of consecutive transmission time intervals (TTIs).
[40] Every DRX period, the UE detects whether scheduling information of the UE itself
is transmitted on a downlink control channel during a specific checking period. Upon
detecting the scheduling information, the UE receives data by using the scheduling in-
formation.

[41 ] During the monitored duration, when no scheduling information of the UE is
received from a base station (BS), the UE does not monitor the downlink control
channel during the remaining cycles of the DRX period.
[42] When the BS establishes the DRX period of the control channel, every DRX period,
the UE monitors the control channel only during the monitored duration, and stops
monitoring of the control channel during a non-monitored duration.
[43] When the scheduling information of the UE is detected on the downlink control
channel, that is, when decoding of the downlink control channel is successful, the UE
can continuously monitor the downlink control channel during an extended period
even after the monitored duration is over.
[44] When the scheduling information of the UE is detected on the downlink control
channel, the UE can enter a continuous reception mode. In the continuous reception
mode, the UE can continuously receive the downlink control channel until a specific
condition is satisfied.
[45] There may be an occasion in which, after the UE enters the continuous reception
mode from a discontinuous reception mode, the UE re-enters the discontinuous
reception mode from the continuous mode. This occasion may occur when the UE does
not detect the scheduling information of the UE on the downlink control channel
during a specific time period after the UE enters the continuous reception mode.
[46] Such an occasion may also occur when the UE receives from the BS an instruction,
which allows the UE to enter the discontinuous reception mode, after the UE enters the
continuous reception mode.
[47] When the scheduling infomiation is detected within the monitored duration, the UE
can extend the monitored duration. The UE can monitor the downlink control channel
for the extended time period even if the monitored duration is over.
[48] The downlink control channel may be any one of a paging channel and L1/L2
control channel which delivers information regarding on radio resource allocation. The
L1/L2 control channel is also referredto as a physical downlink control channels
(PDCCH). The downlink control channel carries resource allocation information on
which the UE receives data on a downlink shared channel (DL-SCH) or on which the
UE transmits data on an uplink shared channel (UL-SCH). The downlink control
channel carries scheduling assignment information of the UE. Scheduling assignment
may be uplink assignment and/or downlink assignment. When the downlink control
channel is successful decoded, the UE can recognize that the scheduling information of
the UE is being delivered on the downlink control channel.
[49] The BS can inform the UE of information which indicates whether DRX is
configured to monitor the control channel, information on a DRX period and a
monitored duration, information on an extended period, etc.

[50] The BS can infonn the UE of configuration information indicating a minimum
possible number of sub-frames (or a time duration) which follow an n-th sub-frame
and in which the UE has to monitor the downlink control channel.
[51] The BS can inform the UE of information (i.e., configuration information of the
DRX period) on a repetition period of the monitored duration in which the UE
monitors the downlink control channel.
[52] The BS may monitor the control channel only during the monitored duration of the
DRX period, and inform the UE of DRX configuration infonnation indicating whether
to stop monitoring during the non-monitored duration.
[53] Upon detecting the scheduling information of the UE. the BS can infom the UE of
information on an extended period in which the DRX period is inactivated and the
downlink control channel is continuously monitored.
[54] Information on the monitored duration or the extended period may be represented
by a sub-frame to which the downlink control channel is allocated. The information on
the monitored duration or the extended period may be represented by the number of
consecutive sub-frames to be monitored. Alternatively, the infonnation on the
monitored duration or the extended period may be represented by the number of
consecutive TTIs for monitoring the downlink control channel. For example, the
monitored duration is indicated by only one sub-frame, the UE monitors the downlink
control channel only in the one sub-frame. Therefore, if there is data or control in-
fonnation to be transmitted to the UE, the BS has to inform this only on the downlink
control channel allocated to the sub-frame belonging to the monitored duration.
However, when the system experiences power shortage, or when a large amount of
data has to be transmitted to another user, the BS has to give up data transmission of
another user in order to infonn the UE of the existence of data. That is, when only one
sub-frame is included in the monitored duration of the UE, the BS experiences
significant limits in utilizing radio resources. Therefore, it is effective to define a
plurality of consecutive sub-frames (or a plurality of TTIs) in the monitored duration
or the extended period.
[55] FIG. 6 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[56] Referring to FIG. 6, a DRX period has a length of 7 TTIs, and a monitored duration
has a length of 2 TTIs. The remaining cycles of the DRX period, that is. a non-
monitored duration, have a length of 7 TTIs. The length of the monitored duration is
defined by the number of consecutive TTIs. The TTI is a unit of scheduling radio
resources. The TTI is a time required to transmit one sub-frame. At least one PDCCH
and at least one physical downlink shared channel (PDSCH) can be allocated to one
sub-frame.

[57] A BS can inform a UE of the length of the monitored duration. The monitored
duration is a part of the DRX period. The DRX period specifies periodic repetition of
the monitored duration followed by the non-monitored duration.
[58] Eveiy DRX period, the UE monitors at least one PDCCH during the monitored
duration. The PDCCH is a control channel carrying scheduling assignment (e.g.,
uplink assignment or downlink assignment). If decoding is not successfully performed
on the PDCCH during the monitored duration, the UE stops the monitoring of the
PDCCH during the non-monitored duration. The BS can infonn the UE of information
(i.e., DRX configuration) indicating whether the PDCCH is monitored during the non-
monitored duration.
[59] The UE monitors the PDCCH during the monitored duration. The UE may wake up
only during the monitored duration to perform uplink transmission or downlink
transmission. For example, the UE may periodicaUy report a channel quality indicator
(CQI) to the BS during the monitored duration.
[60] FIG. 7 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[61] Refening to FIG. 7, every DRX period, a UE monitors a PDCCH during a
monitored duration. When decoding is successfully performed on the PDCCH during
the monitored duration, that is, when data to be transmitted to the UE is detected, data
on a DL-SCH is received by using information indicated on the PDCCH.
[62] When the UE successfully receives the PDCCH on which uplink assignment or
downlink assignment is indicated during the monitored duration, the PDCCH can be
monitored during an extended period. In this example, data is indicated at 2 TTIs, and
the monitored duration is further extended. If the PDCCH is not successfully decoded
during the extended period, the UE re-enters the DRX period. The BS can inform the
UE of infonnation on the extended period.
[63] FIG. 8 shows an example of a method of monitoring a control channel according to
an embodiment of the present mvention.
[64] Refening to FIG. 8, a DRX period is divided into an on-period and an off-period.
The on-period is a period in which a UE monitors a PDCCH. The off-period is a period
in which the UE stops monitoring the PDCCH and enters DRX sleep mode. A BS can
inform the UE of information on the on-period or the off-period. When the UE suc-
cessfully receives the PDCCH during the off-period, downlink data can be recei\ed on
a DL-SCH.
[65] The on-period is defined by the number of consecutive TTIs. The off-period may
also be defined by the number of consecutive TTIs.
[66] The on-period and the off-period may have fixed lengths. That is, during the on-
period, the UE may do not change the length of the on-period or the off-period even if

scheduling information is detected on the PDCCH. In this case, the on-period and the
off-period of the UE have invariable lengths. Therefore, when the on-period is over,
the UE transitions to the off-period regardless of whether transmission information is
received during the on-period. That is, although the PDCCH has been successfully
received at the first 2 TTIs, the UE does not monitor the PDCCH during the off-period,
starting from a time point when the off-period begins.
[67] FIG. 9 shows an example of a method of monitoring a control channel according to
an embodiment of the present invention.
[68] Refening to FIG. 9, a BS instructs a UE to skip an off-period during a specific
DRX period. Scheduling information may not be received within a previous on-period
due to a large amount of data or control information to be sent from the BS to the UE.
In this case, it can be instructed such that the off-period of the specific DRX period is
skipped during the specific DRX period, and thus a current mode can be switched to a
continuous reception mode only during the specific DRX period. Alternatively, in this
case, it can be instructed such that the UE switches the current mode to continuously
receive data by stopping DRX configuration. "When the instruction for skipping the off-
period is received, the UE does not enter the off-period and performs an operation in
the on-period amounting to the skipped periods of time.
[69] FIG. 10 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[70] Refening to FIG. 10, when a PDCCH is successfully decoded during an on-period
of a specific DRX period, the PDCCH can be further monitored for a time period
amounting to an extended period. The extended period is defined by the number of
consecutive TTIs for monitoring the PDCCH when downlink transmission is expected.
Herein, the PDCCH is successfully decoded during an on-period having a length of 2
TTIs, and the PDCCH is monitored during an extended period having a length of 2
TTIs. Therefore, a total length of the monitored duration is 4 TTIs.
[71] While receiving the downlink control channel during the on-period, when
scheduling assignment (e.g., downlink assignment or uplink assignment) of the UE is
detected on the downlink control channel, the UE further monitors the PDCCH for a
time period amounting to the extended peiiod. If the PDCCH is not successfully
decoded during the extended period, the UE re-enters the DRX period.
[72] The BS can instruct the UE to switch to a continuous reception mode continuously
during an on-period in a next DRX period, or sv\itch to the continuous reception mode
only during se\eral DRX periods, or extends a length of the on-period. Even after the
UE switches to the continuous reception mode, the BS can instruct the UE to transition
to the off-period. While staying in the continuous reception mode, when the BS
instructs the UE to transition to the off-period, the UE ends the continuous reception

mode and transitions to the off-period.
[73] FIG. 11 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[74J Referring to FIG. 11, when a PDCCH is successfully decoded during an on-period,
a UE inactivates an off-period, and further monitors the PDCCH for a time period
amounting to an extended period. A BS can instruct the UE to transition to the off-
period during the extended period. That is, the UE can enter a DRX period directly
under the instruction of the BS instead of entering the DRX period after the extended
period is over.
[75] FIG. 12 shows an example of a method of monitoring a control channel according
to an embodiment of the present invention.
[76] Referring to FIG. 12, when data is indicated, a plurality of extended periods exist.
That is, when a PDCCH is successfully decoded during an on-period, a UE further
monitors the PDCCH during an extended period. If the PDCCH is successfully
decoded only during the extended period, the UE continuously monitors the PDCCH
during an additionally extended period. When data is indicated during an on-period,
the PDCCH can be continuously monitored during a plurality of extended periods after
the on-period of a corresponding DRX period is over.
[77] After receiving the data indication, the UE continuously monitors the PDCCH
during the extended period in order to receive subsequent downlink transmission.
When data indication is received again, the UE continuously monitors again the
PDCCH during another extension period. If existence of data is no longer indicated
during the additional extension period, the UE re-enters the DRX period.
[78] Although the control channel is transmitted at a relatively short transmission period,
the UE monitors the control channel only during the on-period and does not monitor
the control channel during the off-period. The BS can inform the UE of DRX con-
figuration by using a media access control (MAC) message or a radio resource control
(RRC) message. When the control channel is monitored by using a DRX method,
battery consumption of the UE can be reduced.
[79] FIG. 13 is a block diagram showing constimtional elements of a UE. A UE 50
includes a processor 51, a memory 52, a radio frequency (RF) unit 53, a display unit
54, and a user interface unit 55. The memoiy 52 is coupled to the processor 51 and
stores an operating system, applications, and general files. The display unit 54 displays
a variety of information of the UE 50 and may use a well-known element such as a
liquid crystal display (LCD), an organic light emitting diode (OLED). etc. The user
interface unit 55 can be configured with a combination of well-known user interfaces
such as a keypad, a touch screen, etc. The RF unit 53 is coupled to the processor 51
and transmits and/or receives radio signals.

[80] Layers of the radio interface protocol are implemented in the processor 51. The
processor 51 provides a control plane and a user plane. A monitoring function of the
control channel can be implemented in the processor 51.
[81J The steps of a method described in connection with the embodiments disclosed
herein may be implemented by hardware, software or a combination thereof. The
hardware may be implemented by an application specific integrated circuit (ASIC) that
is designed to perform the above function, a digital signal processing (DSP), a pro-
grammable logic device (PLD), a field programmable gate array (FPGA), a processor,
a controller, a microprocessor, the other electronic unit, or a combination thereof A
module for performing the above function may implement the software. The software
may be stored in a memory unit and executed by a processor. The memory unit or the
processor may employ a variety of means that is well known to those skilled in the art.
[82] As the present invention may be embothed in several forms without departing from
the spirit or essential characteristics thereof, it should also be understood that the
above-described embodiments are not limited by any of the details of the foregoing de-
scription, unless otherwise specified, but rather should be construed broadly within its
spirit and scope as defined in the appended claims. Therefore, all changes and modi-
fications that fall within the metes and bounds of the claims, or equivalence of such
metes and bounds are intended to be embraced by the appended claims.

Claims
[1] 1. A method of monitoring a control channel in a wireless communication
system, the method comprising:
monitoring a physical downlink control channel (PDCCH) during a monitored
duration, wherein the monitored duration is a part of a discontinuous reception
(DRX) period, the DRX period specifying the periodic repetition of the
monitored duration followed by a non-monitored duration.
[2 J The method of claim 1, further comprising:
receiving a DRX configuration that allows to stop monitoring the PDCCH during
the non-monitored duration.
[3] The method of claim 1, wherein the monitored duration is defined by the number
of consecutive transmission time intervals (TTIs).
14] The method of claim 1, further comprising:
transmitting periodic channel quality indicator (CQI) reports during the
monitored duration.
[5] The method of claim 1, wherein the PDCCH carries scheduling assignment.
[6] The method of claim 1, further comprising:
monitoring the PDCCH during an extended period when successfully decoding
the PDCCH indicating downlink assignment or uplink assignment during the
monitored duration, the extended period defined by the number of consecutive
TTIs.
[7] The method of claim 6, wherein the extended period is signaled by a base station.
[8] The method of claim 6, further comprising:
re-entering the DRX period when the PDCCH is not decoded during the
extended period.
[9] A method of monitoring a control channel in a wireless communication system,
the method comprising:
monitoring a PDCCH during a monitored duration, wherein the monitored
duration is a part of a DRX period, the DRX period specifying the periodic
repetition of the monitored duration followed by a non-monitored duration: and
monitoring the PDCCH during an extended period when the PDCCH is suc-
cessfully decoded during the monitored duration.
[10] The method of claim 9, further comprismg:
stopping monitoring the PDCCH during the non-monitored duration when the
PDCCH is not successfully decoded during the monitored duration.
[11] The method of claim 9, wherein the monitored duration and the extended period
are signaled by a base station.

[12] the method of claim 9, further comprising:
re-entering the DRX period when the PDCCH is not decoded during the
extended period.

A method of monitoring a control channel in a wireless communication system includes monitoring a physical down-link control channel (PDCCH) during a monitored duraticn, wherein the monitored duration is a part of a discontinuous reception (DRX) period, the DRX period specifying the periodic repetition of the monitored duration followed by a non-monitored duration. By monitoring a control channel during a DRX period, battery consumption of a user equipment can be reduced and an operation time of the user equipment can be increased.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=3q4XmUAcevqRyaUOelfFPA==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

268254

Indian Patent Application Number

2090/KOLNP/2009

PG Journal Number

35/2015

Publication Date

28-Aug-2015

Grant Date

24-Aug-2015

Date of Filing

02-Jun-2009

Name of Patentee

LG ELECTRONICS INC.

Applicant Address

20, YEOUIDO-DONG, YEONGDEUNGPO-GU, SEOUL 105-721

Inventors:

#	Inventor's Name	Inventor's Address
1	CHUN, SUNG DUCK	LG R & D COMPLEX, 533, HOGYE 1-DONG, DONGAN-GU, ANYANG-SI, GYEONGKI-DO 431-749
2	PARK, SUNG JUN	LG R & D COMPLEX, 533, HOGYE 1-DONG, DONGAN-GU, ANYANG-SI, GYEONGKI-DO 431-749
3	YI, SEUNG JUNE	LG R & D COMPLEX, 533, HOGYE 1-DONG, DONGAN-GU, ANYANG-SI, GYEONGKI-DO 431-749
4	LEE, YOUNG DAE	LG R & D COMPLEX, 533, HOGYE 1-DONG, DONGAN-GU, ANYANG-SI, GYEONGKI-DO 431-749

PCT International Classification Number

H04L 29/08

PCT International Application Number

PCT/KR2008/001479

PCT International Filing date

2008-03-17

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-2007-0081981	2007-08-14	U.S.A.
2	60/895,418	2007-03-16	U.S.A.
3	60/896,250	2007-03-21	U.S.A.