Abstract:
An apparatus and method of transmitting a circuit switched (CS) voice application via an enhanced dedicated channel (E-DCH), implemented in a wireless transmit/receive unit (WTRU). The method includes receiving a grant; performing an E-TFC selection procedure based on the grant, wherein a number of bits that may be transmitted over an enhanced dedicated channel (E-DCH) is determined, determining an adaptive multi-rate (AMR) codec bit-rate based on the number of bits that may be transmitted over the E-DCH, generating AMR voice packets based on the determined AMR codec bit rate, and submitting the AMR voice packets to lower layers for transmission over the E-DCH.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/346,086 filed Dec. 30, 2008, which claims the benefit of U.S. Provisional Application No. 61/019,156 filed Jan. 4, 2008. Each of the above-referenced applications is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     This application is related to wireless communications. 
     BACKGROUND 
     The Third Generation Partnership Project (3GPP) Release 99 introduced carrying circuit-switched (CS) voice over a dedicated transport channel (DCH) on both the uplink (UL) and downlink (DL) in order to control the adaptive multi-rate (AMR) data rate. AMR is an audio data compression scheme optimized for voice coding. 
     AMR coding is used to select the optimum channel (half or full rate) and codec mode (voice and channel bit rates) to deliver the best combination of voice quality and system capacity. AMR coding improves the quality and robustness of the network connection while sacrificing some voice clarity. The AMR codec has the capability of generating voice frames containing a variable number of bits according to a set of possible data rates. The selection of a higher data rate results in a higher voice quality at the expense of requiring more resources to transmit the data. 
       FIG. 1  is a block diagram of an AMR voice system  100 . The AMR system may include a transmit side  110  and a receive side  120 . The transmit side  110  may comprise a 8-bit A law or μ-law pulse code modulator, a low pass filter, an analog-to-digital converter, a voice activity detector, a voice encoder, a comfort noise generation system, and an error concealment mechanism to combat the effects of transmission errors and lost packets. The receive side  120  may comprise components for the inverse functions. 
     As shown in  FIG. 1 , the voice encoder takes its input as a 13 bit uniform Pulse Code Modulated (PCM) signal either from the audio part of the WTRU or on the network side, from the Public Switched Telephone Network (PSTN) via an 8-bit A-law or μ-law to 13-bit uniform PCM conversion. The encoded voice at the output of the voice encoder is packetized and delivered to a discontinuous transmission control and operation block (i.e. network interface). In the receive side  120 , the inverse operations take place. 
     The detailed mapping between input blocks of 160 voice samples in 13 bit uniform PCM format to encoded blocks (in which the number of bits depends on the presently used codec mode) and from these to output blocks of 160 reconstructed voice samples is described in 3GPP TS 26.090. The encoding scheme is Multi-Rate Algebraic Code Excited Linear Prediction. The bit-rates of the source codec are listed in Table 1. 
     The multi-rate voice encoder is a single integrated voice codec with eight source rates from 4.75 Kbit/s to 12.2 Kbit/s, and a low rate background noise encoding mode. The voice coder is capable of switching its bit-rate every 20 ms voice frame upon command. An AMR voice codec capable WTRU supports the following source codec bit-rates listed in Table 1. 
     
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Source codec bit-rates for the AMR codec. 
               
             
          
           
               
                   
                 Codec mode 
                 Source codec bit-rate 
               
               
                   
                   
               
             
          
           
               
                   
                 AMR_12.20 
                 12.20 
                 Kbit/s (GSM EFR) 
               
               
                   
                 AMR_10.20 
                 10.20 
                 Kbit/s 
               
               
                   
                 AMR_7.95 
                 7.95 
                 Kbit/s 
               
               
                   
                 AMR_7.40 
                 7.40 
                 Kbit/s (IS-641) 
               
               
                   
                 AMR_6.70 
                 6.70 
                 Kbit/s (PDC-EFR) 
               
               
                   
                 AMR_5.90 
                 5.90 
                 Kbit/s 
               
               
                   
                 AMR_5.15 
                 5.15 
                 Kbit/s 
               
               
                   
                 AMR_4.75 
                 4.75 
                 Kbit/s 
               
               
                   
                 AMR_SID 
                 1.80 
                 Kbit/s (see note 1) 
               
               
                   
                   
               
             
          
         
       
     
     In a 3GPP Release 99 system, when CS voice is carried over the DCH, the AMR data rate on the UL may be controlled using transport format combination (TFC) control messages transmitted by a radio network controller (RNC). The network may alleviate UL congestion by reducing the data rate of a WTRU utilizing CS voice transmission. 
     3GPP Release 6 introduced high-speed uplink packet access (HSUPA) to provide higher data rates for uplink transmissions. As part of HSUPA, a new transport channel, the enhanced dedicated channel (E-DCH) was introduced. The E-DCH is a transport uplink channel that is used to improve capacity, data throughput, and reduce the delays for the dedicated channels in the UL. Typically in each transmission time interval (TTI), one transport block of data may be transmitted. The size of the transport block may very for each TTI. 
     In HSUPA, the MAC layer may multiplex data from multiple logical channels or MAC-d flows to a single E-DCH. The network may configure which MAC-d flows may be multiplexed together and the highest priority MAC-d flow being transmitted dictates the quality of service (QoS) parameterization of a transmission. A MAC-d flow may be defined as a flow of MAC-d PDUs which belong to logical channels that share some QoS characteristics. 
     Support for the transport of CS voice over the High-Speed Downlink Shared Channel (HS-DSCH) and the E-DCH has been introduced in Releases 7 and 8. This feature has several benefits, such as minimizing the use of DCH transport channel in a cell and faster call setup. 
     Currently, there is no method describing how to control the UL data rate of a CS voice service when it is carried over the E-DCH. There exists a need to implement the rate control of a CS voice carried over the E-DCH. 
     In a 3GPP Release 6 system, the E-DCH uses different scheduling mechanisms and a hybrid automatic repeat request (HARQ). The scheduling is typically based on scheduling grants sent by a Node-B scheduler to control the WTRU&#39;s uplink transmissions. The WTRU may transmit scheduling information to request additional resources. Scheduling grants may include absolute grants and relative grants. Absolute grants set an absolute value of an upper limit of the power a terminal may use for a transmission. Relative grants meanwhile update the resource allocation by indicating a value such as “up”, “down”, or “hold”. However, a clear mapping between transport formats and supportable data rates does not exist. Further, the resource allocation tasks of the E-DCH are shared between the RNC and the Node-B. Additionally, a WTRU may need to reduce its UL data rate due to transmission power limitations at a cell edge. 
     Accordingly, there exists a need to control the AMR data rate when CS voice service is transmitted over the E-DCH. By controlling the AMR data rate when CS voice is transmitted over the E-DCH, the UL voice coverage may be extended. 
     SUMMARY 
     An apparatus and method of transmitting a circuit switched (CS) voice application via an enhanced dedicated channel (E-DCH), implemented in a wireless transmit/receive unit (WTRU) are disclosed. The method includes receiving a grant; performing an E-TFC selection procedure based on the grant, wherein a number of bits that may be transmitted over an enhanced dedicated channel (E-DCH) is determined, determining an adaptive multi-rate (AMR) codec bit-rate based on the number of bits that may be transmitted over the E-DCH, generating AMR voice packets based on the determined AMR codec bit rate, and submitting the AMR voice packets to lower layers for transmission over the E-DCH. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a block diagram of an AMR voice system  100 ; 
         FIG. 2  shows a wireless communication system; 
         FIG. 3  is a functional block diagram of a wireless transmit/receive unit (WTRU) and the base station of the wireless communication system shown in  FIG. 2 ; 
         FIG. 4  is a flow diagram of a direct mapping implemented in a non-scheduled MAC-d flow; 
         FIG. 5  shows a flow diagram of an autonomous selection of an AMR codec-bit rate when the WTRU data rate is limited by the WTRU&#39;s transmission power; and 
         FIG. 6  is a flow diagram of a direct mapping implemented in a scheduled MAC-d flow. 
     
    
    
     DETAILED DESCRIPTION 
     When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment. 
       FIG. 2  shows a wireless communication system  200  including a plurality of WTRUs  210 , a Node-B  220 , a controlling radio network controller (CRNC)  230 , a serving radio network controller (SRNC)  240 , and a core network  250 . 
     As shown in  FIG. 2 , the WTRUs  210  are in communication with the Node-B  220 , which is in communication with the CRNC  230  and the SRNC  240 . Although three WTRUs  210 , one Node-B  220 , one CRNC  230 , and one SRNC  240  are shown in  FIG. 2 , it should be noted that any combination of wireless and wired devices may be included in the wireless communication system  200 . 
       FIG. 3  is a functional block diagram  300  of a WTRU  210  and the Node-B  220  of the wireless communication system  200  of  FIG. 2 . As shown in  FIG. 3 , the WTRU  210  is in communication with the Node-B  220  and both are configured to perform a method for controlling the data rate of a CS voice application in an evolved wireless system. 
     In addition to the components that may be found in a typical WTRU, the WTRU  210  includes a processor  215 , a receiver  216 , a transmitter  217 , and an antenna  218 . The processor  215  is configured to perform a method for controlling the data rate of a CS voice application. The receiver  216  and the transmitter  217  are in communication with the processor  215 . The antenna  218  is in communication with both the receiver  216  and the transmitter  217  to facilitate the transmission and reception of wireless data. 
     In addition to the components that may be found in a typical base station, the Node-B  220  includes a processor  225 , a receiver  226 , a transmitter  227 , and an antenna  228 . The processor  225  is configured to perform a method for controlling the data rate of a CS voice application. The receiver  226  and the transmitter  227  are in communication with the processor  225 . The antenna  228  is in communication with both the receiver  226  and the transmitter  227  to facilitate the transmission and reception of wireless data. 
     In a first embodiment, a MAC-d flow containing the CS voice data is a non-scheduled MAC-d flow. For a non-scheduled MAC-d flow, the SRNC  240  may be configured to signal a guaranteed physical layer data rate for a specific MAC-d flow or a specific service. The non-scheduled MAC-d flow may effectively disable a Node-B  220  scheduler control for this particular service. The SRNC  240  may be configured to determine a maximum number of bits from the MAC-d flow that may be transmitted in an E-DCH transport block. The serving Node-B  220  may be configured to restrict the non-scheduled MAC-d flow to be transmitted on specific HARQ processes and to inform the SRNC  240  of the restriction. For a non-scheduled flow, either direct mapping or indirect mapping may be implemented. 
       FIG. 4  is a flow diagram  400  of a direct mapping implemented in a non-scheduled MAC-d flow. The SRNC  240  may be configured to control the data rate of a CS voice application when there is a direct mapping between the number of bits for a transmission and an AMR codec bit-rate. A mapping identifying an AMR codec bit-rate for UL transmissions based on a number of bits allowed during UL transmissions may be signaled to the WTRU ( 410 ). Alternatively the WTRU  210  may be preconfigured with the mapping. For example, a non-scheduled flow of 204+x bits, where x is the number of header bits due to the Packet Data Convergence Protocol (PDCP) radio link control (RLC) and MAC headers, may be mapped to a single AMR frame of 204 bits, or a non-scheduled flow of 408+x bits may be mapped to two AMR frames of 204 bits. The WTRU  210  may receive a configuration (or reconfiguration) message ( 420 ) from the SRNC  240 . The configuration message may comprise information identifying a maximum number of bits allowed for non-scheduled UL transmissions. In response to receiving the configuration message from the SRNC  240 , the WTRU  210  may then select the proper AMR codec bit-rate ( 430 ). The selected AMR codec bit-rate may be used to generate frames that map to the new maximum number of bits ( 440 ). The WTRU  210  then transmits the generated frames via the E-DCH ( 450 ). This direct mapping method allows for a method of controlling the AMR codec bit-rate of the WTRU  210  from the SRNC  240 . 
     The WTRU  210  may be configured to autonomously determine the AMR codec bit-rate based on the maximum number of bits indicated by the SRNC  240  signaling (i.e. configuration message). For example, the WTRU  210  may receive the configuration message indicating the maximum number of bits for a non-scheduled UL transmission. The WTRU  210  may be configured to determine an AMR frame type, (when multiplied by the number of frames per transmission), that has the largest total number of bits (including required PDCP/RLC/MAC overhead) smaller than or equal to the maximum number of bits of the non-scheduled transmissions. Optionally, the Node-B  220  may signal to the WTRU  210  the number of AMR frames that should be mapped to the non-scheduled transmission in order to avoid any ambiguity. 
     The direct mapping method may also allow for adaptation of the AMR codec bit-rate in case the WTRU  210  data rate is limited by the WTRU&#39;s  210  transmission power. In this case, the number of bits available for transmission for the non-scheduled MAC-d flow is less than the maximum number of bits signaled by the SRNC  240  because the transmission power of the WTRU  210  is insufficient to transmit this maximum number of bits. This may occur as a WTRU  210  moves to a cell edge. In this case, the WTRU  210  becomes more power limited. Accordingly, in order to maintain a voice connection the WTRU  210  may adjust the codec bit-rate of the AMR codec to maintain transmission of voice data at a lower data rate, even though available power may be reduced. 
       FIG. 5  shows a flow diagram  500  of an autonomous selection of an AMR codec-bit rate when the WTRU  210  data rate is limited by the WTRU&#39;s  210  transmission power. The WTRU  210  receives a signal indicating the maximum number of bits that may be used for UL transmissions ( 510 ). The WTRU  210  then must determine the maximum number of bits that may be transmitted given the available power headroom. This is normally done as part of an enhanced-transport format combination (E-TFC) selection procedure ( 520 ). If this number of bits is larger or equal than the maximum number of bits signaled by the network ( 525 ), the WTRU  210  selects the available number of bits based on the received signal indicating the maximum number of bits signaled by the network ( 530 ). If the number of bits is smaller than the maximum number of bits signaled by the network( 525 ), WTRU  210  selects the available number of bits based on the E-TFC procedure ( 540 ). After determining the number of available bits, the WTRU  210  modifies (if needed) the AMR codec bit-rate so that the AMR codec generates frames that map to a maximum number of bits, accounting for Packet Data Convergence Protocol (PDCP), Radio Link Control (RLC), and MAC-e/es header, that is smaller than the available number of bits given the restriction ( 550 ). The WTRU  210  may then transmit data in the uplink based on the modified AMR codec bit-rate ( 560 ). The WTRU  210  may be configured to reduce the AMR codec bit-rate in advance of E-TFC selection if the WTRU  210  is aware that it will soon be in a power-limited situation in order to prevent loss of AMR frames. 
     Additionally the WTRU  210  may be configured to reduce the AMR codec bit-rate may only if the power-limited situation persists for a predetermined time period. 
     In another option, indirect mapping may be implemented for the non-scheduled flow. When an indirect mapping is implemented for the non-scheduled MAC-d flow, the SRNC  240  may be configured to signal a guaranteed physical layer data rate for a specific MAC-d flow or a specific service. However, no direct mapping between the AMR codec mode and the maximum number of bits of the non-scheduled transmissions is defined. The WTRU  210  may be configured to autonomously select an AMR codec mode that results in a predefined performance level based on at least one measured metrics. 
     The metrics used by the WTRU  210  may include one or more of the following: the number of buffered AMR frames (in RLC and/or MAC buffers); the amount of bits in buffered AMR frames; the transmission delay of AMR frames, including either the buffering delay only or the total delay (the sum of the buffering delay and HARQ transmission delay); the number of HARQ transmissions; the HARQ block error rate (BLER); the HARQ failure rate; the number or percentage of AMR frames being discarded due to excessive buffering delay (if such discard function is configured); the WTRU transmission power; the WTRU power headroom; the available number of bits to the non-scheduled flow given the transmission power obtained from E-TFC selection procedure; the throughput of the voice transmission; maximum number of bits of the non-scheduled flow; number of available HARQ processes; maximum transmission power; target HARQ BLER (signaled by the network through new RRC signaling); or any function or combination of the above metrics. 
     For example, the WTRU  110  may be configured to estimate a maximum throughput. The WTRU may determine the throughput by estimating the product between the maximum number of bits, the fraction of HARQ processes available to the non-scheduled flow, and the HARQ BLER, divided by the TTI duration (2 ms). 
     Once the WTRU  210  collects the metrics, the WTRU  210  may be configured to use the metrics to select an AMR codec bit-rate. The WTRU  210  may select a codec bit-rate that is inferior or equal to the estimated throughput, minus a margin. In the case that the available number of bits from E-TFC selection is inferior to the maximum number of bits, that number may be used instead. 
     The WTRU  210  may also use MAC segmentation (if configured) to segment voice frames. Alternatively, the MAC may restrict segmentation of CS traffic over high speed packet access (HSPA). 
     In some cases, if segmentation is not allowed in the MAC the transmission of larger CS MAC-e or MAC-es protocol data units (PDUs) may be blocked if the selected transport block (TB) size is smaller than the CS RLC PDU. The MAC may not be able to transmit the PDU until the TB size increases. However, if subsequent CS transmissions are smaller because the AMR codec bit-rate has been reduced, this may block the transmission of the subsequent packets that may be transmitted with the given selected TB size. Therefore, the MAC entity may discard the PDU if after N TTIs it is still not able to transmit it, where N is an integer number that may be configured by higher layers or predefined in the MAC. 
     In a second embodiment, a MAC-d flow containing the CS voice data is a scheduled MAC-d flow. The Node-B  220  is configured to control a maximum power ratio (e.g. via a serving grant) that the WTRU  210  may use for the MAC-d flow and other MAC-d flows, which allows the Node-B  220  to impose a limit on the data rate. 
       FIG. 6  is a flow diagram  600  of a direct mapping implemented in a scheduled MAC-d flow. A mapping identifying an AMR codec bit-rate for UL transmissions based on a number of bits allowed during UL transmissions may be signaled to the WTRU ( 610 ). Alternatively the WTRU may be preconfigured with the mapping. The WTRU  210  may receive a scheduling grant from a Node-B ( 620 ). The grant may indicate a maximum allowable transmission power or an adjustment in the maximum allowable transmission power. The number of bits available for the scheduled transmissions may be determined using an E-TFC selection procedure ( 630 ). The number of bits available to the MAC-d flow containing the CS voice bits at transmission time may vary according to the outcome of the E-TFC selection procedure. For example, the transmission may be limited by the WTRU&#39;s  210  maximum transmission power or by the presence of data from other MAC-d flows or logical channels that must be transmitted. The WTRU  210  may then select an AMR codec bit-rate based on the number of bits available and the mapping ( 640 ). The selected AMR codec bit-rate may be used to generate frames that map to the maximum number of bits ( 650 ). The WTRU  210  then transmits the generated frames via the E-DCH. This direct mapping method may allow the Node-B  220  to dynamically control the AMR codec bit-rate of the WTRU  210 . 
     When the MAC-d flow containing the CS voice bits is a scheduled flow, a direct mapping may be defined between the number of bits available for the scheduled transmissions and the AMR rate. Further, if desired, there may be signaling defined between the SRNC  240  and the Node-B  220  to allow the SRNC  240  to control the WTRU  210  data rate. 
     Optionally, once the available number of bits is known, the WTRU  210  may be configured to modify the AMR codec bit-rate to generate frames that map a number of bits (from the mapping) that is smaller than the available number of bits. Further, the WTRU  210  may be configured to reduce the AMR codec bit-rate in advance of the E-TFC selection procedure if it is determined that the available number of bits will soon be reduced in order to prevent the loss of AMR frames. 
     In another alternative, an indirect mapping may be implemented for the scheduled flow. When an indirect mapping is implemented for a scheduled MAC-d flow, the Node-B  220  may be configured to signal a grant. The WTRU  210  may use an E-TFC selection procedure to determine a number of bits available for uplink transmissions. However, no direct mapping between the AMR codec mode and the maximum number of bits of the scheduled transmissions is defined. The WTRU  210  may then autonomously select an AMR codec mode that results in a predefined performance level based on at least one measured metric. 
     The metrics used by the WTRU  210  may include one or more of the following: the number of buffered AMR frames; the amount of bits in buffered AMR frames; the transmission delay of AMR frames, including either the buffering delay only or the total delay; the number of HARQ transmissions; the HARQ BLER; the HARQ failure rate; the number or percentage of AMR frames being discarded due to excessive buffering delay; the WTRU transmission power; the WTRU power headroom; the available number of bits to the non-scheduled flow given the transmission power obtained from E-TFC selection procedure; the throughput of the voice transmission; maximum number of bits of the non-scheduled flow; number of available HARQ processes; maximum transmission power; and target HARQ BLER; or any function or combination of the above metrics. 
     In one embodiment, the WTRU  210  may be configured to estimate a maximum throughput. For example, the WTRU  210  may determine the throughput by estimating the product between a maximum number of bits determined after an E-TFC selection procedure, the fraction of HARQ processes available to the scheduled flow, and the HARQ BLER, divided by the TTI duration (2 ms). 
     Once the WTRU  210  collects the metrics, the WTRU  210  may be configured to use the metrics to select an AMR codec mode. The WTRU  210  may select a AMR codec mode that is inferior or equal to the estimated throughput, minus a margin. In the case that the available number of bits from E-TFC selection is inferior to the maximum number of bits, that number may be used instead. 
     The WTRU  210  may also use MAC segmentation (if configured) to segment voice frames. Alternatively, the MAC may restrict segmentation of CS traffic over high speed packet access (HSPA). 
     The WTRU  210  may perform the selection of an AMR codec mode according to the above every TTI, or every time the scheduled or non-scheduled grant is modified, or every time the available number of bits from E-TFC restriction changes, or every time a RLC or MAC SDU containing a voice packet has to be segmented (either at RLC or MAC layer. 
     In some cases, if segmentation is not allowed in the MAC, the transmission of larger CS MAC-e or MAC-es PDUs may be blocked if the selected TB size is smaller than the CS RLC PDU. The MAC may not be able to transmit the PDU until the TB size increases. However, if subsequent CS transmissions are smaller because the AMR codec bit-rate has been reduced, this may block the transmission of the subsequent packets that may be transmitted with the given selected TB size. Therefore, the MAC entity may discard the PDU if after N TTIs it is still not able to transmit it, where N is an integer number that may be configured by higher layers or predefined in the MAC. 
     Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
     Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. 
     A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB) module.