Abstract:
A method for performing radio bearer mapping in an user equipment of a wireless communications system includes setting a plurality of multiplexing options of a frequency division duplex radio bearer, called FDD RB hereinafter, when the user equipment operates in a Cell Dedicated Channel state, each of the plurality of multiplexing options corresponding to a multiplexing mode, determining whether an RB of the user equipment has one of the plurality of multiplexing options, and using a multiplexing mode corresponding to a multiplexing option of the plurality of multiplexing options for performing RB mapping when the RB has the multiplexing option.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/848,013, filed on Sep. 29, 2006 and entitled “Method and apparatus for Radio Bearer mapping in a wireless communication system,” the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and apparatus for performing radio bearer mapping in a wireless communications system, and more particularly to a method and apparatus for ensuring that an user equipment of the wireless communications system uses a proper multiplexing mode, so as to enhance transmission efficiency. 
     2. Description of the Prior Art 
     The third generation (3G) mobile communications system has adopted a Wideband Code Division Multiple Access (WCDMA) wireless air interface access method for a cellular network. WCDMA can provide 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. 
     For the universal mobile telecommunications system (UMTS), the 3G communications system comprises User Equipment (UE), the UMTS Terrestrial Radio Access Network (UTRAN), and the Core Network (CN). Communications protocols utilized include Access Stratum (AS) and Non-Access Stratum (NAS). AS comprises various sub-layers for different functions, including Radio Resource Control (RRC), Radio Link Control (RLC), Media Access Control (MAC), Packet Data Convergence Protocol (PDCP), and Broadcast/Multicast Control (BMC). The sub-layers mentioned, and their operating principles, are well known in the art, and detailed description thereof is omitted. RRC is a Layer 3 communications protocol, and is the core of the AS communications protocol. All radio resource information exchange, radio resource configuration control, QoS control, channel transmission format configuration control, packet segmentation/concatenation processing and control, and NAS protocol transmission processing is performed by the RRC layer. 
     The RRC layer is located in the Radio Network Controller (RNC) of the UTRAN and the UE, and is primarily used to manage and maintain packet switching and sequencing of a Uu Interface. The RRC layer performs radio resource control in the following manner. After the RRC of the UE obtains various measurement results from the MAC and the Physical Layer, the RRC generates a Measurement Report from the various measurement results. After processing by the RLC, the MAC, and the Physical Layer, the Measurement Report is sent to the RRC of a network, e.g. UTRAN. After a Radio Resource Assignment message sent from the RRC of the network is received, the RRC of the user equipment can perform lower layer control and setting based on a result of resolving the message, e.g. setting the operation mode, packet length, and encryption method of the RLC layer, setting the channel multiplexing mapping method and channel transmission format of the MAC, and setting the operating frequency, spreading code, transmission power, synchronization method, and measurement items of the Physical Layer. 
     Between the user equipment and the network, the RRC layer uses RRC Messages, also known as signaling, to exchange information. RRC Messages are formed from many Information Elements (IE) used for embedding necessary information for setting, changing, or releasing protocol entities of Layer 2 (RLC, MAC) and Layer 1 (Physical Layer), thereby establishing, reconfiguring, or releasing information exchange channels to perform data packet transportation. Through RRC Messages, the RRC layer can embed control signals needed by an upper layer in the RRC Message, which can be sent between the NAS of the user equipment and the CN through the radio interface to complete the required procedures. 
     From the standpoint of the RRC, all logical data communication exchange channels, be they for providing data transmission exchange to the user or for providing RRC layer control signal transmission exchange, are defined in the context of a Radio Bearer (RB). In the user end, the RB comprises one unidirectional or a pair of uplink/downlink (UL/DL) logic data transmission exchange channels. In the network, the RB comprises one unidirectional or a pair of uplink/downlink logic data transmission exchange channels. 
     In order to enhance transmission efficiency, the RRC layer of the UE can select appropriate multiplexing options according to the IE “RB mapping info” provided by the network, so as to determine statuses of UL/DL transport channels. When the UE operating in a CELL_DCH (Cell Dedicated Channel) state conforms to specified rules (e.g. when the UE receives the IE “RB mapping info”, when specified transport channels are added or deleted, when the UE performs a cell reselection or a state transition, or when the UE releases an RB), the UE shall set the multiplexing option of a frequency-division-duplex (FDD) RB according to a multiplexing option selection process  10  of the prior art shown in  FIG. 1 . The multiplexing option selection process  10  comprises the following steps, where DCH, HS-DSCH, E-DCH, and DSCH mean Dedicated Channel, High Speed Downlink Shared Channel, Enhanced Dedicated Transport Channel, and Downlink Shared Channel.
         Step  100 : Start.   Step  102 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+HS-DSCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  118 ; else, go to Step  104 .   Step  104 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+HS-DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  118 ; else, go to Step  106 .   Step  106 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+DSCH” for the DL. If true, go to Step  120 ; else, go to Step  108 .   Step  108 : Determine whether the FDD RB has a multiplexing option with transport channel type “HS-DSCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  118 ; else, go to Step  110 .   Step  110 : Determine whether the FDD RB has a multiplexing option with transport channel type “HS-DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  118 ; else, go to Step  112 .   Step  112 : Determine whether the FDD RB has a multiplexing option with transport channel type “DSCH” for the DL. If true, go to Step  120 ; else, go to Step  114 .   Step  114 : Determine whether the FDD RB has a multiplexing option with transport channel type “DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  118 ; else, go to Step  116 .   Step  116 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  118 ; else, go to Step  122 .   Step  118 : Use the corresponding multiplexing option for RB mapping, and go to Step  122 .   Step  120 : Determine that the UE behavior is unspecified, and go to Step  122 .   Step  122 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  124 ; else, go to Step  126 .   Step  124 : Use the multiplexing mode corresponding to the multiplexing option for RB mapping.   Step  126 : Do not use the multiplexing mode corresponding to the multiplexing option for RB mapping.   Step  128 : End.       

     Therefore, the multiplexing option selection process  10  must undergo Step  122 , whether the FDD RB conforms to one of the multiplexing options mentioned in Steps  102  to  116  or not. That is, the UE must determine if the FDD RB has a multiplexing option with transport channel type “DCH” for the DL and UL. Meanwhile, when the FDD RB has the multiplexing option with transport channel type “DCH” for the DL and UL, the UE uses the multiplexing mode corresponding to the multiplexing option for RB mapping; when the FDD RB does not have the multiplexing option with transport channel type “DCH” for the DL and UL, the UE does not use the multiplexing mode corresponding to the multiplexing option for RB mapping. In other words, the UE must check the conditions of Step  122  to select the multiplexing mode. In such a situation, the UE can only use the low data rate transport channel corresponding to Step  122  for RB mapping even if there are other multiplexing options with higher data rate transport channels available. Therefore, the steps before Step  122  become redundant and invalid, and the UE cannot reach a proper transmission rate. 
     In short, since the multiplexing option selection process  10  must undergo Step  122 , the UE cannot use multiplexing modes corresponding to Steps Step  102  to  116  when the FDD RB has a multiplexing option with transport channel type “DCH” for the DL and UL, leading to low transmission efficiency. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a method for performing radio bearer mapping in an user equipment of a wireless communications system comprises setting a plurality of multiplexing options of a frequency division duplex radio bearer, called FDD RB hereinafter, when the user equipment operates in a Cell Dedicated Channel state, each of the plurality of multiplexing options corresponding to a multiplexing mode, determining whether an RB of the user equipment has one of the plurality of multiplexing options, and using a multiplexing mode corresponding to a multiplexing option of the plurality of multiplexing options for performing RB mapping when the RB has the multiplexing option. 
     According to the present invention, a communications device of a wireless communications system utilized for accurately performing radio bear mapping comprises a control circuit for realizing functions of the communications device, a central processing unit installed in the control circuit for executing a program code to operate the control circuit, and a memory coupled to the central processing unit for storing the program code. The program code comprises code for setting a plurality of multiplexing options of a frequency division duplex radio bearer, called FDD RB hereinafter, when the communications device operates in a Cell Dedicated Channel state, called CEL_DCH state hereinafter, each of the plurality of multiplexing options corresponding to a multiplexing mode, code for determining whether an RB of the communications device has one of the plurality of multiplexing options, and code for using a multiplexing mode corresponding to a multiplexing option of the plurality of multiplexing options for performing RB mapping when the RB has the multiplexing option. 
     According to the embodiment of the present invention, a method for determining a multiplexing mode of a radio bearer in an user equipment of a wireless communications system comprises determining whether the radio bearer, called RB hereinafter, has a second multiplexing option only when the RB does not have a first multiplexing option, when the user equipment operates in a Cell Dedicated Channel state, and determining a multiplexing mode of the RB according to a determination result of the second multiplexing option. The first multiplexing option is a multiplexing option with a transport channel type “Dedicated Channel” for the downlink, and with a transport channel type “Enhanced Dedicated Transport Channel” for the uplink, and the second multiplexing option is a multiplexing option with a transport channel type “Dedicated Channel” for the downlink, and with a transport channel type “Dedicated Channel” for the uplink. 
     According to the embodiment of the present invention, a communications device of a wireless communications system utilized for accurately determining a multiplexing mode of a radio bearer comprises a control circuit for realizing functions of the communications device, a central processing unit installed in the control circuit for executing a program code to operate the control circuit, and a memory coupled to the central processing unit for storing the program code. The program code comprises code for determining whether the radio bearer, called RB hereinafter, has a second multiplexing option only when the RB does not have a first multiplexing option, when the communications device operates in a Cell Dedicated Channel state, and code for determining a multiplexing mode of the RB according to a determination result of the second multiplexing option. The first multiplexing option is a multiplexing option with a transport channel type “Dedicated Channel” for the downlink, and with a transport channel type “Enhanced Dedicated Transport Channel” for the uplink, and the second multiplexing option is a multiplexing option with a transport channel type “Dedicated Channel” for the downlink, and with a transport channel type “Dedicated Channel” for the uplink. 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 multiplexing option selection process according to the prior art. 
         FIG. 2  is a functional block diagram of a communications device. 
         FIG. 3  is a diagram of the program code shown in  FIG. 2 . 
         FIG. 4  is a flowchart diagram of a process according to an embodiment of the present invention. 
         FIG. 5  is a flowchart diagram of a process according to an embodiment of the present invention. 
         FIG. 6  is a schematic diagram of a multiplexing option selection process in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 2 , which is a functional block diagram of a communications device  200 . For the sake of brevity,  FIG. 2  only shows an input device  202 , an output device  204 , a control circuit  206 , a central processing unit (CPU)  208 , a memory  210 , a program code  212 , and a transceiver  214  of the communications device  200 . In the communications device  200 , the control circuit  206  executes the program code  212  in the memory  210  through the CPU  208 , thereby controlling an operation of the communications device  200 . The communications device  200  can receive signals input by a user through the input device  202 , such as a keyboard, and can output images and sounds through the output device  204 , such as a monitor or speakers. The transceiver  214  is used to receive and transmit wireless signals, delivering received signals to the control circuit  206 , and outputting signals generated by the control circuit  206  wirelessly. From a perspective of a communications protocol framework, the transceiver  214  can be seen as a portion of Layer 1, and the control circuit  206  can be utilized to realize functions of Layer 2 and Layer 3. 
     Please continue to refer to  FIG. 3 .  FIG. 3  is a diagram of the program code  212  shown in  FIG. 2 . The program code  212  comprises an application layer  300 , a Layer 3 interface  302 , and a Layer 2 interface  306 , and is coupled to a Layer 1 interface  318 . The Layer 3 interface  302  comprises a buffer for storing an RRC message  308 , and for forming an RRC PDU  314  according to the RRC message  308 . The application layer  300  provides control signals required by necessary procedures, which can be outputted by attaching the control signals to RRC PDUs  314  for setting, modifying, or releasing the Layer 2 interface  306  and the Layer 1 interface  318 , to establish, modify, or cancel data exchange channels. 
     In order to enhance transmission efficiency, the Layer 3 interface  302  can select appropriate multiplexing options according to the IE “RB mapping info” provided by the network, so as to determine statuses of UL/DL transport channels. In such a situation, the embodiment of the present invention provides an RB mapping program code  320  for accurately perform RB mapping, so as to prevent waste of radio resources. 
     Please refer to  FIG. 4 , which illustrates a schematic diagram of a process  40  in accordance with an embodiment of the present invention. The process  40  is utilized for performing RB mapping in a user equipment of a wireless communications system, and can be compiled into the RB mapping program code  320 . The process  40  comprises the following steps:
         Step  400 : Start.   Step  402 : Set a plurality of multiplexing options of an FDD RB when the user equipment operates in a CELL_DCH state, and each of the plurality of multiplexing options corresponding to a multiplexing mode.   Step  404 : Determine whether an RB of the user equipment has one of the plurality of multiplexing options.   Step  406 : Use a multiplexing mode corresponding to a multiplexing option of the plurality of multiplexing options for performing RB mapping when the RB has the multiplexing option.   Step  408 : End.       

     Therefore, according to the process  40 , when the user equipment operates in the CELL_DCH state, the embodiment of the present invention determines whether the RB of the user equipment has one of the plurality of multiplexing options, and uses a multiplexing mode corresponding to a multiplexing option of the plurality of multiplexing options for performing RB mapping when the RB has the multiplexing option. In other words, when the RB has a multiplexing option, the embodiment of the present invention directly use a multiplexing mode corresponding to the multiplexing option for RB mapping, and does not use multiplexing modes corresponding to other multiplexing options. In such a situation, the embodiment of the present invention can ensure that the user equipment uses a proper multiplexing mode, so as to enhance transmission efficiency. 
     In the process  40 , when the RB has a multiplexing option, the embodiment of the present invention uses a multiplexing mode corresponding to the multiplexing option for RB mapping. Therefore, preferably, when the RB has a multiplexing option, the embodiment of the present invention no longer determines whether the RB has another multiplexing option. In such a situation, the embodiment of the present invention can prevent the user equipment from performing redundant decision steps, such as Step  122  shown in  FIG. 1 , so that the operating efficiency of the user equipment can be enhanced. In addition, if the RB does not have any of the multiplexing options, the embodiment of the present invention preferably does not use any multiplexing mode. 
     In the prior art, a decision step (Step  122  in  FIG. 1 ) must be performed, whether the RB has a specified multiplexing option or not. In comparison, through the process  40 , the embodiment of the present invention uses a multiplexing mode corresponding to a multiplexing option for RB mapping when the RB has the multiplexing option, and does not use other multiplexing modes. Therefore, the embodiment of the present invention can ensure that the user equipment can use the proper multiplexing mode for RB mapping, so as to enhance transmission efficiency. 
     Please refer to  FIG. 5 , which illustrates a schematic diagram of a process  50  in accordance with an embodiment of the present invention. The process  50  is utilized for determining a multiplexing mode of a radio bearer in a user equipment of a wireless communications system, and can be compiled into the RB mapping program code  320 . The process  50  comprises the following steps:
         Step  500 : Start.   Step  502 : Determine whether the RB has a second multiplexing option only when the RB does not have a first multiplexing option, when the user equipment operates in a CELL_DCH state. The first multiplexing option is a multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “E-DCH” for the UL, and The second multiplexing option is a multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “DCH” for the UL.   Step  504 : Determine a multiplexing mode of the RB according to a determination result of the second multiplexing option.   Step  506 : End.       

     According to the process  50 , when the user equipment operates in the CELL_DCH state, the embodiment of the present invention checks if the RB has the second multiplexing option only when the RB does not have the first multiplexing option. That is, only when the FDD RB does not have a multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “E-DCH” for the UL, the embodiment of the present invention checks if the RB has a multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “DCH” for the UL, and determines a multiplexing mode for the RB accordingly. 
     Preferably, when the RB has the first multiplexing option, the embodiment of the present invention does not check if the RB has the second multiplexing option, and does not determine the multiplexing mode according to the determination result of the second multiplexing option. In such a situation, when the RB has the first multiplexing option, since the embodiment of the present invention does not check if the RB has the second multiplexing option, the determination result of the second multiplexing option will not affect the multiplexing mode of the RB. As a result, the user equipment can use a proper multiplexing mode, so as to reach a better transmission efficiency. Furthermore, in Step  504 , if the RB has the second multiplexing option, the embodiment of the present invention can set the RB to have a transport channel type “DCH” for the DL and UL. Oppositely, if the RB does not have the second multiplexing option, the embodiment of the present invention does not set the multiplexing mode for the RB. 
     As mentioned above, the prior art (Step  122  in  FIG. 1 ) always checks if the RB has a multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “DCH” for the UL, and determines the multiplexing mode for the RB accordingly. In comparison, only when the RB does not have the multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “E-DCH” for the UL, the embodiment of the present invention checks if the RB has the multiplexing option with a transport channel type “DCH” for the DL, and with a transport channel type “DCH” for the UL, and determines the multiplexing mode for the RB accordingly. Therefore, the embodiment of the present invention does not have to perform redundant steps, such as Step  122 , to ensure that the user equipment uses a proper multiplexing mode, so as to enhance transmission efficiency. 
     The processes  40  and  50  are embodiments of the present invention, and those skilled in the art can make alternations. For example, please refer to  FIG. 6 , which illustrates a schematic diagram of a multiplexing option selection process  60  in accordance with an embodiment of the present invention. The multiplexing option selection process  60  is utilized for performing RB mapping in a user equipment of a wireless communications system, so as to determine multiplexing modes of an FDD RB. The multiplexing option selection process  60  can be complied into the RB mapping program code  320 , and comprises the following steps:
         Step  600 : Start.   Step  602 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+HS-DSCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  622 ; else, go to Step  604 .   Step  604 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+HS-DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  622 ; else, go to Step  606 .   Step  606 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH+DSCH” for the DL. If true, go to Step  620 ; else, go to Step  608 .   Step  608 : Determine whether the FDD RB has a multiplexing option with transport channel type “HS-DSCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  622 ; else, go to Step  610 .   Step  610 : Determine whether the FDD RB has a multiplexing option with transport channel type “HS-DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  622 ; else, go to Step  612 .   Step  612 : Determine whether the FDD RB has a multiplexing option with transport channel type “DSCH” for the DL. If true, go to Step  620 ; else, go to Step  614 .   Step  614 : Determine whether the FDD RB has a multiplexing option with transport channel type “DSCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  622 ; else, go to Step  616 .   Step  616 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH” for the DL, and with transport channel type “E-DCH” for the UL. If true, go to Step  622 ; else, go to Step  618 .   Step  618 : Determine whether the FDD RB has a multiplexing option with transport channel type “DCH” for the DL, and with transport channel type “DCH” for the UL. If true, go to Step  622 ; else, go to Step  626 .   Step  620 : Determine that the UE behavior is unspecified.   Step  622 : Use a multiplexing mode corresponding to the multiplexing option for RB mapping.   Step  626 : Do not use any multiplexing mode corresponding to the multiplexing option for RB mapping.       

     Comparing the multiplexing option selection process  60  in  FIG. 6  with the multiplexing option selection process  10  in  FIG. 1 , the multiplexing option selection process  60  performs Steps  620 ,  622 , or  626  according to results of Steps  602  to  618 , and after performing Steps  620 ,  622 , or  626 , the multiplexing option selection process  60  no longer performs any decision steps. In comparison, the multiplexing option selection process  10  must perform Step  122 , whether the FDD RB has one of the multiplexing options mentioned in Steps  102  to  116 , and performs RB mapping accordingly. Therefore, the multiplexing option selection process  60  shown in  FIG. 6  can ensure that the user equipment uses the proper multiplexing mode, so as to enhance transmission efficiency. 
     In summary, the embodiment of the present invention checks if the RB has a multiplexing option with a transport type “DCH” for the DL/UL only when the RB does not have a multiplexing option with a transport type “DCH” for the DL, and with a transport type “E-DCH” for the UL, and determines the multiplexing mode for the RB accordingly. Therefore, the present invention does not perform redundant steps, to ensure that the user equipment uses the proper multiplexing mode and enhance transmission efficiency accordingly. 
     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.