Abstract:
A method of improving semi-persistent scheduling, abbreviated to SPS, resources reconfiguration for a user equipment in a wireless communication system is disclosed. The method comprises receiving a radio resource control, abbreviated to RRC, connection reconfiguration message corresponding to an RRC connection reconfiguration procedure; and forbidding performing SPS resources reconfiguration when the RRC connection reconfiguration procedure is not a handover procedure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 12/603,549, filed on Oct. 21, 2009, which claims the benefit of U.S. Provisional Application No. 61/109,907, filed on Oct. 30, 2008 and entitled “METHOD AND APPARATUS FOR SEMI-PERSISTENT SCHEDULING RESOURCE RECONFIGURATION IN A WIRELESS COMMUNICATIONS SYSTEM”. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method utilized in a wireless communication system and communication device thereof, and more particularly, to a method of improving semi-persistent scheduling resources reconfiguration and communication device thereof. 
     2. Description of the Prior Art 
     A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs). The radio protocol stacks of E-UTRAN is given including a radio resource control layer (RRC), a packet data convergence protocol layer (PDCP), a radio link control layer (RLC), a medium access control layer (MAC), and a physical layer (PHY). 
     In order to utilize shared channel (SCH) resources efficiently, a semi-persistent scheduling (SPS) function is introduced in the LTE system and is used in MAC, for serving upper layer applications which generate semi-static size data periodically, e.g. VoIP services. SPS resources are semi-static resources including physical resource block (PRB), modulation and coding scheme (MCS), and periodicity. Periodicity is configured by RRC, and a valid set of PRBs and MCSs is configured by RRC and selected by a physical downlink control channel (PDCCH) signaling sent from the E-UTRAN. According to current 3GPP specification, there is only an SPS pattern, i.e. periodicity, for frequency division duplex (FDD), and may exist multiple SPS patterns for time division duplex (TDD) so that SPS resources can be reconfigured to add one more SPS pattern. 
     An RRC connection reconfiguration procedure is used to modify an RRC connection, e.g. to establish/modify/release radio bearers, to perform handover, or to setup/modify/release measurements. When the UE receives an RRC connection reconfiguration message including an information element (IE) “mobilityControlInformation”, which includes parameters relevant to network controlled mobility, the UE performs an RRC connection reconfiguration procedure as a handover procedure. In the handover procedure, the UE deactivates any SPS resource if there is any SPS resource active and performs a radio resource configuration procedure in which SPS resources reconfiguration is performed when the RRC connection reconfiguration message includes an IE “radioResourceConfiguration”. Therefore, the UE can apply new SPS resources configuration after switching to a target cell. SPS resources reconfiguration intends that SPS cell radio network temporary identifier (SPS C-RNTI) which is the UE specific identity assigned by RRC for activation/modification of SPS resources is changed, periodicity is changed, an SPS pattern is added or removed for TDD, or a valid set of PRBs and MCSs is changed. 
     In addition, SPS resources may need to be reconfigured due to which a new service is activated or a service is released in the condition except the handover procedure. For example, when a VoIP service is initiated, SPS resources are usually configured for most common VoIP packet size, and when a streaming service is activated during the VoIP service, SPS resources have to be reconfigured with a large transport block size, i.e. PRBs or MCS, or a small SPS periodicity, to serve both the VoIP service and the streaming service simultaneously. The E-UTRAN can activate or modify SPS resources by sending a PDCCH signaling including SPS C-RNTI. However, SPS resources reconfiguration is not clearly specified in the RRC connection reconfiguration procedure which does not include the IE “mobilityControlInformation”, such that SPS resources reconfiguration is exactly performed only in the handover procedure. 
     Note that, for the LTE system, there is a timing issue that activation time of SPS resources is not included in any RRC message, and thus the UE does not know when to switch to new SPS resources. When the UE reconfigures SPS resources in the condition except the handover procedure, the UE may continue using prior SPS resources that are already released to receive transport blocks until receiving the PDCCH signaling, which causes the received transport blocks to be unsuccessfully decoded. 
     SUMMARY OF THE INVENTION 
     The present invention therefore provides a method and related communication device for improving SPS resources reconfiguration. 
     A method of improving semi-persistent scheduling, abbreviated to SPS, resources reconfiguration for a user equipment in a wireless communication system is disclosed. The method comprises receiving a radio resource control, abbreviated to RRC, connection reconfiguration message corresponding to an RRC connection reconfiguration procedure; and forbidding performing SPS resources reconfiguration when the RRC connection reconfiguration procedure is not a handover procedure. 
     A method of improving semi-persistent scheduling, abbreviated to SPS, resources reconfiguration for a user equipment in a wireless communication system is disclosed. The method comprises receiving a radio resource control, abbreviated to RRC, connection reconfiguration message corresponding to an RRC connection reconfiguration procedure; and when the RRC connection reconfiguration message includes SPS resources reconfiguration and the RRC connection reconfiguration procedure is not a handover procedure, considering the RRC connection reconfiguration message invalid and performing an RRC connection re-establishment procedure. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a wireless communication system. 
         FIG. 2  is a schematic diagram of a communication device according to an example of the present invention. 
         FIG. 3  and  FIG. 4  are flowcharts of processes according to examples of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1 , which is a schematic diagram of a wireless communication system  10 . The wireless communication system  10  can a long-term evolution (LTE) system or other mobile communication systems, and is briefly composed of a network and a plurality of user equipments (UEs), as the structure illustrated in  FIG. 1 . In the LTE system, the network is referred as an evolved universal terrestrial radio access network (E-UTRAN) comprising a plurality of evolved base stations (eNBs). The UEs can be devices such as mobile phones, computer systems, etc. Besides, the network and the UE can be seen as a transmitter or receiver according to transmission direction, e.g., for uplink, the UE is the transmitter and the network is the receiver, and for downlink, the network is the transmitter and the UE is the receiver. 
     Please refer to  FIG. 2 , which is a schematic diagram of a communication device  20  according to an example of the present invention. The communication device  20  can be the UE shown in  FIG. 1  and includes a processor  200 , a computer readable recording medium  210 , a communication interfacing unit  220  and a control unit  230 . The computer readable recording medium  210  is any data storage device that stores storage data  212 , including program code  214 , thereafter read and processed by the processor  200 . Examples of the computer readable recording medium  210  include a subscriber identity module (SIM), read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The control unit  230  controls the communication interfacing unit  220  and related operations and states of the communication device  20  according to processing results of the process  200 . The communication interfacing unit  220  is preferably a radio transceiver for wirelessly communicating with the network. 
     Please refer to  FIG. 3 , which is a flowchart of a process  30  according to an example of the present invention. The process  30  is also utilized for improving semi-persistent scheduling (SPS) resources reconfiguration and can be compiled into the program code  214 . The process  30  includes the following steps: 
     Step  300 : Start. 
     Step  302 : Receive an RRC connection reconfiguration message corresponding to an RRC connection reconfiguration procedure. 
     Step  304 : Forbid performing SPS resources reconfiguration when the RRC connection reconfiguration procedure is not a handover procedure. 
     Step  306 : End. 
     For the reason that the UE may decode transport blocks unsuccessfully when SPS resources reconfiguration is not exactly performed in the non-handover RRC connection reconfiguration procedure, the process  30  simply forbids performing SPS resources reconfiguration when the RRC connection reconfiguration procedure is not a handover procedure, and therefore the timing issue is avoided. In other words, the process  30  allows SPS resources reconfiguration to be performed only in the handover procedure. Note that in current specification, whether the RRC connection reconfiguration procedure is the handover procedure depends on the received RRC connection reconfiguration message including the IE “mobilityControlInformation” or not. 
     Furthermore, please refer to  FIG. 4 , which is a flowchart of a process  40  according to an example of the present invention. The process  40 , similar to the process  30 , aims to prevent SPS resources reconfiguration being performed in the non-handover RRC connection reconfiguration procedure. The process  40  can be compiled into the program code  214 , which includes the following steps: 
     Step  400 : Start. 
     Step  402 : Receive an RRC connection reconfiguration message corresponding to an RRC connection reconfiguration procedure. 
     Step  404 : When the RRC connection reconfiguration message includes SPS resources reconfiguration and the RRC connection reconfiguration procedure is not a handover procedure, consider the RRC connection reconfiguration message invalid and perform an RRC connection re-establishment procedure. 
     Step  406 : End. 
     According to the process  40 , when the received RRC connection reconfiguration message includes SPS resources reconfiguration and does not include the IE “mobilityControlInformation”, which intends that the RRC connection reconfiguration procedure is not the handover procedure, the UE acts for preventing SPS resources reconfiguration being performed. The first thing the UE does is to consider the RRC connection reconfiguration message invalid, so that the RRC connection reconfiguration procedure is fail to complete; and later, the UE performs the RRC connection re-establishment procedure to re-establish RRC connection in order to recover the RRC connection reconfiguration failure. 
     In other words, the process  40  does not allow SPS resources reconfiguration being performed in the RRC connection reconfiguration procedure which is not the handover procedure even though the RRC connection reconfiguration message includes SPS resources reconfiguration. Thus SPS resources reconfiguration is performed only in the handover procedure. 
     In conclusion, the present invention provides complete behavior of SPS resources reconfiguration for the UE so that SPS resources reconfiguration is exactly performed in any case and the timing issue is avoided. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.