Abstract:
A method for enhancing data transmission efficiency for a radio resource control, hereinafter called RRC, procedure for a user equipment, also called UE, of a wireless communications system includes initiating an RRC update procedure; sending an update message corresponding to the RRC update procedure to a network terminal; reselecting a serving cell after the update message is sent to the network terminal; and using a common HS-DSCH radio network transaction identifier, abbreviated to common H-RNTI, for a high speed downlink operation corresponding to a CELL_FACH state if the selected serving cell supports the high speed downlink operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/896,500, filed on Mar. 23, 2007 and entitled “Method And Apparatus for Improving HS-DSCH Reception when CCCH is mapped on HS-DSCH in a Wireless Communication System”, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method for enhancing data transmission efficiency for a wireless communications system and related communications device, and more particularly to a method for enhancing data transmission efficiency with a high speed downlink operation for a wireless communications system and related communications device. 
         [0004]    2. Description of the Prior Art 
         [0005]    The third generation (3G) mobile telecommunications system has adopted a Wideband Code Division Multiple Access (WCDMA) wireless air interface access method for a cellular network. WCDMA provides high frequency spectrum utilization, universal coverage, and high quality, high-speed multimedia data transmission. The WCDMA method also meets all kinds of QoS requirements simultaneously, providing diverse, flexible, two-way transmission services and better communication quality to reduce transmission interruption rates. Through the 3G mobile telecommunications system, a user can utilize a wireless communications device, such as a mobile phone, to realize real-time video communications, conference calls, real-time games, online music broadcasts, and email sending/receiving. However, these functions rely on fast, instantaneous transmission. Thus, targeting at the third generation mobile telecommunication technology, the 3rd Generation Partnership Project (3GPP) provides High Speed Package Access (HSPA) technology, which includes High Speed Downlink Package Access (HSDPA) and High Speed Uplink Package Access (HSUPA), to increase bandwidth utility rate and package data processing efficiency to improve uplink/downlink transmission rate. 
         [0006]    On the basis of HSDPA, the 3GPP further introduces HS-DSCH reception in a CELL_FACH state allowing the UE in the CELL_FACH state to monitor a High Speed Downlink Shared Channel (HS-DSCH) accompanied with a Shared Control Channel for HS-DSCH (HS-SCCH) for downlink data reception, so as to improve a peak data rate, a signaling delay, a state transition delay, download times and flexible cell capacity. 
         [0007]    A UMTS radio access network (UTRAN) enables the HS-DSCH reception in the CELL_FACH state by including parameters, related to radio resource control (RRC) configuration of HS-SCCH, HS-DSCH and a common HS-DSCH radio network transaction identifier (common H-RNTI), in the system information broadcast. For the UE in an idle mode, the parameters are configured in a “Downlink HS-PDSCH system information” information element (IE) included in a system information block (SIB) type 5/5bis. For the UE in an RRC connection mode, the parameters are configured in a “Downlink HS-PDSCH system information for connected mode” IE included in an SIB type 6. 
         [0008]    The UE may use a common or a dedicated H-RNTI to perform the HS-DSCH reception in the CELL_FACH state. The common and dedicated H-RNTIs are both used as an identity of the UE so that the UE can receive its own packets. Furthermore, the common H-RNTI can be shared by multiple UEs, whereas each dedicated H-RNTI is only allocated to one UE. During reception of media access control (MAC) packets, the UE using the common H-RNTI needs to determine whether the received packets belong to it via UE identification information (i.e. UE ID and UE ID Type) in the packet header. On the other hand, the MAC packets for the UE using the dedicated H-RNTI include no UE identification information to provide better data transmission efficiency. 
         [0009]    The UE selects a suitable common H-RNTI to use from the common H-RNTI parameter. On the other hand, if the UTRAN attempts to allocate a dedicated H-RNTI to the UE, the UTRAN sends a related configuration through RRC procedures, such as an RRC connection or a cell update procedure, and the UE stores the configuration in a H-RNTI variable. Each time the HS-DSCH reception in the CELL_FACH state is enabled, the UE uses the dedicated H-RNTI if the H-RNTI variable is set; otherwise the UE uses the common H-RNTI. 
         [0010]    The UE has an HS_DSCH_RECEPTION_CELL_FACH_STATE and an HS_DSCH_RECEPTION_OF_CCCH variable revealing a use state of the dedicated and common H-RNTIs, respectively. When the HS_DSCH_RECEPTION_CELL_FACH_STATE variable is set to “TRUE”, the UE receives packets mapped to a Dedicated Traffic Channel (DTCH) and a Dedicated Control Channel (DCCH) according to the dedicated H-RNTI. When the HS_DSCH_RECEPTION_OF_CCCH variable is set to “TRUE”, the UE receives packets mapped to a Common Control Channel (CCCH) according to the common H-RNTI. If both of the variables are set to “FALSE, this means that the HS-DSCH reception in the CELL_FACH state is deactivated. 
         [0011]    According to the RRC specification, the UE has to perform a variable determining procedure to activate or deactivate the HS-DSCH reception in the CELL_FACH state. For applying the HS-DSCH reception in the CELL_FACH state, the following conditions must be met: (1) the UE is in the CELL_FACH state; (2) the variable H_RNTI is set; (3) the SIB type 6 is defined and includes the “Downlink HS-PDSCH system information for connected mode” IE or the SIB type 5/5bis includes the “Downlink HS-PDSCH system information for connected mode” IE. If all the conditions are met, the variable HS_DSCH_RECEPTION_CELL_FACH_STATE is set to “TRUE” for starting HS-DSCH reception in low layers (the MAC and physical layer). 
         [0012]    If any of the above conditions is not met and the HS_DSCH_RECEPTION_CELL_FACH_STATE variable is set to “TRUE”, the UE sets the variable to “FALSE”. In addition, if the UE is in the CELL_FACH state and the HS_DSCH_RECEPTION_OF_CCCH variable is set to “FALSE”, the UE stops the HS-DSCH reception. 
         [0013]    The UE may initiate the cell update procedure during the HS-DSCH reception in the CELL_FACH state, and the cause to initiate a cell update procedure may be cell reselection, periodical cell update, a radio link failure, an RLC unrecoverable error or uplink data transmission. The UE also initiates a URA update procedure when performing UTRAN registration area reselection (URA Reselection) or periodical URA update. 
         [0014]    In general, RRC message exchange during the cell/URA update procedure is as follows. The UE first sends a CELL/URA UPDATE message to the UTRAN, and then receives a CELL/URA UPDATE CONFIRM message from the UTRAN for radio bearer reconfiguration or release, mobility information update or transport channel reconfiguration. 
         [0015]    According to the RRC specification, if the UE performs cell reselection after the CELL/URA UPDATE message is sent, the UE performs the following actions: clearing the H-RNTI variable; setting the HS_DSCH_RECEPTION_OF_CCCH variable to “FALSE”; stopping the HS-DSCH reception in the CELL_FACH state; re-sending the CELL/URA UPDATE message. 
         [0016]    The prior art requires the UE to stop the HS-DSCH reception in the CELL_FACH state when performing cell/URA reselection. However, if the new serving cell supports the HS-DSCH reception in the CELL_FACH state, receiving packets without the HS-DSCH reception results in lower data transmission efficiency and greater signaling delays than with the HS-DSCH reception. 
       SUMMARY OF THE INVENTION 
       [0017]    The present invention therefore provides a method for a UE of a wireless communications system and related communications device that utilizes the HS-DSCH reception in the CELL_FACH state for enhancing data transmission efficiency during cell reselection. 
         [0018]    The present invention discloses a method for enhancing data transmission efficiency for an RRC procedure for a UE of a wireless communications system. The method includes initiating an RRC update procedure; sending an update message corresponding to the RRC update procedure to a network terminal; reselecting a serving cell after the update message is sent to the network terminal; and using a common H-RNTI for a high speed downlink operation corresponding to a CELL_FACH state if the selected serving cell supports the high speed downlink operation. The high speed downlink operation includes the operation of the HS-DSCH reception in CELL_FACH state. 
         [0019]    The present invention further discloses a communications device of a wireless communications system for enhancing data transmission efficiency for an RRC procedure. The communications device includes a control circuit, a processor and a memory. The control circuit is used for realizing functions of the communications device. The processor is installed in the control circuit and used for executing a program code to command the control circuit. The memory is installed in the control circuit and coupled to the processor, and used for storing the program code. The program code includes initiating an RRC update procedure; sending an update message corresponding to the RRC update procedure to a network terminal; reselecting a serving cell after the update message is sent to the network terminal; and using a common H-RNTI for a high speed downlink operation corresponding to a CELL_FACH state if the selected serving cell supports the high speed downlink operation. The high speed downlink operation includes the operation of the HS-DSCH reception in CELL_FACH state. 
         [0020]    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 
         [0021]      FIG. 1  is a functional block diagram of a communications device. 
           [0022]      FIG. 2  is a diagram of the program code shown in  FIG. 1 . 
           [0023]      FIG. 3  is a flowchart diagram of a process according to an embodiment of the present invention. 
           [0024]      FIG. 4  is a schematic diagram of a wireless communications system. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Please refer to  FIG. 4 .  FIG. 4  is a schematic diagram of a wireless communications system  400 . The wireless communications system  400  is preferred to be a high-speed packet access (HSPA) system of a third generation (3G) mobile communications system, and is briefly formed with a network terminal and a plurality of user equipments. In  FIG. 4 , the network terminal and the user equipments are simply utilized for illustrating the structure of the wireless communications system  400 . Practically, the network terminal may include a plurality of base stations, radio network controllers and so on according to actual demands, and the user equipments can be apparatuses such as mobile phones, computer systems, etc. 
         [0026]    Please refer to  FIG. 1 , which is a functional block diagram of a communications device  100 . The communications device  100  can be utilized for realizing the user equipments or the network terminal in  FIG. 4 . For the sake of brevity,  FIG. 1  only shows an input device  102 , an output device  104 , a control circuit  106 , a central processing unit (CPU)  108 , a memory  110 , a program code  112 , and a transceiver  114  of the communications device  100 . In the communications device  100 , the control circuit  106  executes the program code  112  in the memory  110  through the CPU  108 , thereby controlling an operation of the communications device  100 . The communications device  100  can receive signals input by a user through the input device  102 , such as a keyboard, and can output images and sounds through the output device  104 , such as a monitor or speakers. The transceiver  114  is used to receive and transmit wireless signals, delivering received signals to the control circuit  106 , and outputting signals generated by the control circuit  106  wirelessly. From a perspective of a communications protocol framework, the transceiver  114  can be seen as a portion of Layer  1 , and the control circuit  106  can be utilized to realize functions of Layer  2  and Layer  3 . Preferably, the communications device  100  is utilized in a HSPA system of a third generation (3G) mobile communications system and supports a high speed downlink operation corresponding to a CELL_FACH state, including HS-DSCH reception in the CELL_FACH state. 
         [0027]    Please continue to refer to  FIG. 2 .  FIG. 2  is a diagram of the program code  112  shown in  FIG. 1 . The program code  112  includes an application layer  200 , a Layer  3   202 , and a Layer  2   206 , and is coupled to a Layer  1   218 . The Layer  3   202  includes a radio resource control (RRC) entity  222  for controlling the Layer  1   218  and the Layer  2   206  and performing peer-to-peer communication with a network terminal, such as a Node-B or a UTRAN. In addition, the RRC entity  222  can switch the communications device  100  among the idle mode, CELL_PCH, URA_PCH, CELL_FACH and CELL_DCH states. 
         [0028]    When the communications device  100  initiates a cell/URA update procedure known as an RRC update procedure, the embodiment of the present invention provides a high-speed reception managing program code  220  in the program code  112  to enhance the data transmission efficiency. Please refer to  FIG. 3 , which illustrates a schematic diagram of a process  30  according to an embodiment of the present invention. The process  30  is applied to a UE of a wireless communications system, and can be compiled into the high-speed reception managing program code  220 . The process  30  includes the following steps: 
         [0029]    Step  300 : Start. 
         [0030]    Step  302 : Initiate a cell/URA update procedure. 
         [0031]    Step  304 : Send a CELL/URA UPDATE message to a UTRAN. 
         [0032]    Step  306 : Reselect a serving cell after the CELL/URA UPDATE message is sent to the UTRAN. 
         [0033]    Step  308 : Determine whether the selected serving cell supports the HS-DSCH reception in the CELL_FACH state or not. If so, perform Step  310 ; otherwise perform Step  312 . 
         [0034]    Step  310 : Use a common H-RNTI for the HS-DSCH reception in the CELL_FACH state and then perform Step  314 . 
         [0035]    Step  312 : Stop the HS-DSCH reception in the CELL_FACH state and then perform Step  314 . 
         [0036]    Step  314 : End. 
         [0037]    According to the process  30 , the UE initiates the cell/URA update procedure due to cell/URA reselection, periodical cell/URA update or other causes, and thereby sends the CELL/URA UPDATE message for notifying the UTRAN of the procedure initiating cause. When the UE performs serving cell reselection after sending the CELL/URA UPDATE message to the UTRAN, the UE determines whether the new serving cell supports the HS-DSCH reception in the CELL_FACH state or not. Preferably, the UE determines whether an SIB type 6 includes a “Downlink HS-PDSCH system information for connected mode” IE or whether an SIB type 5/5bis includes a “Downlink HS-PDSCH system information” IE or not. If any of the SIBs includes the related IE, this means that the serving cell supports the HS-DSCH reception in the CELL_FACH state. If none of the SIBs includes the related IE, this means that the serving cell does not support the HS-DSCH reception in the CELL_FACH state. In addition, the UE could have set a dedicated H-RNTI to use for the HS-DSCH reception in the CELL_FACH state before the cell/URA update procedure. In this situation, the UE clears the dedicated H-RNTI during cell reselection. 
         [0038]    If the selected serving cell supports the HS-DSCH reception in the CELL_FACH state, the UE uses the common H-RNTI for the HS-DSCH reception in the CELL_FACH state. For putting the common H-RNTI into effect, the UE sets a HS_DSCH_RECEPTION_OF_CCCH variable to “TRUE”. During activation of the HS-DSCH reception in CELL_FACH state with the common H-RNTI, the UE starts reception of physical channels (i.e. HS-SCCH and HS-PDSCH) and transport channels (HS-DSCH) according to configuration data of the “Downlink HS-PDSCH system information for connected mode” IE or the “Downlink HS-PDSCH system information” IE. On the contrary, if the serving cell does not support the HS-DSCH reception in the CELL_FACH state, the UE stops all related operations related to the HS-DSCH reception and changes to operate in a non-high speed reception mode with reception of a secondary common control physical channel (S-CCPCH). 
         [0039]    In conclusion, the embodiment of the present invention requires the UE to use the HS-DSCH reception in the CELL_FACH state during cell reselection if the high speed downlink operation is available in the newly selected cell. Therefore, the embodiment of the present invention can enhance data transmission efficiency for the cell/URA procedure. 
         [0040]    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.