Abstract:
A method and apparatus for a wireless receiver are described herein. A user equipment (UE) may process control information in a first time slot of a transmission time interval (TTI) having a plurality of time slots. The UE may, in response to the control information including valid resource assignment information for the UE, receive data in the first time slot and another time slot of the TTI. The UE may, in response to the control information not including valid resource assignment information for the UE, discontinue reception in the TTI. The UE may discontinue reception for another time slot of the TTI. The circuitry may be further configured to receive a transmission indicating that a base station will discontinuously transmit to the UE. The control information may be processed prior to processing any of the data symbols of the TTI.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/414,034 filed Mar. 30, 2009 which is a division of U.S. patent application Ser. No. 10/629,434 filed Jul. 29, 2003, which issued as U.S. Pat. No. 7,529,220 on May 5, 2009, which claims priority from U.S. Application No. 60/399,810 filed Jul. 31, 2002, which is incorporated by reference as if fully set forth herein. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention generally relates to code division multiple access (CDMA) receivers, and in particular relates to an apparatus and method for achieving improved performance in a receiver by demodulating one or more desired data streams that are subject to interference from signals directed to other receivers in both the user&#39;s and other cells, background noise, or distortion caused by the radio channel. 
       BACKGROUND 
       [0003]    CDMA is a digital transmission technique where multiple signals are distinguished by their respective chip code sequences (codes). The signal structure generally has a time division component where transmissions are divided into, for example, a sequence of frames that may be further subdivided into timeslots. In addition, some systems use transmission time intervals (TTIs) where a TTI indicates the time interval over which a particular set of codes (and other formatting parameters) are valid. To implement a receiver, knowledge of the identity of the codes used to construct the transmitted signal is generally required. 
         [0004]    The receiver in the user equipment (UE) may know the identity of all codes, a subset of codes, or none of the codes used for any given transmission. Codes associated with signals directed to the desired UE are called “own-UE codes.” Codes associated with signals directed to other receivers are called “other-UE codes.” Typically, a system includes a means for the receiver to know or learn the identity of own-UE codes via initial programming, signaling, acquisition algorithms, or various other techniques that may include trial and error and may be inefficient from a power or performance standpoint. Systems may or may not provide a means to learn the identity of other-UE codes. 
         [0005]    Demodulation of data associated with any one code is subject to degraded bit error rate (BER) caused by interfering own-UE codes, other-UE codes, and other interference sources. The receiver can benefit from knowledge of the identity of own-UE or other-UE codes by implementing improved algorithms that provide a lower BER at a given signal-to-noise ratio in a radio channel with a certain multipath characteristic. 
         [0006]    Multi-User Detection or a Multi-User Detector (MUD) is one example of a receiver algorithm that simultaneously processes received signals associated with multiple codes in an attempt to minimize the impact of interference and provide a lower BER, or the same BER in less favorable SNR or multipath. The MUD operates optimally when it is configured for the exact set of transmitted codes. To achieve this, a MUD algorithm requires knowledge of the identity of transmitted own-UE and other-UE codes. 
         [0007]    One approach to implementing a MUD is to simply configure the receiver for all codes that may or may not have been transmitted. There are two disadvantages that render this approach undesirable, and possibly impractical. First, the more codes a MUD is configured to process, the greater the number of computations required to demodulate the transmitted data. Configuring a receiver only for codes that have been transmitted requires less power, fewer computations, and less processing time. Second, the BER is often degraded if the MUD is configured to process a relatively large number of codes. Configuring a receiver only for codes that have been transmitted generally provides an improvement in BER. 
         [0008]    Blind code detection (BCD) is one method of learning the identity of transmitted codes when the receiver uses a MUD algorithm and complete knowledge of the identity of all transmitted codes is not known and/or is not signaled to the receiver. The performance of BCD is measured by how well the list of transmitted codes it creates matches the actual list of transmitted codes. BCD performance is improved by making as much use as possible of a priori and signaled information about transmitted codes and by making the information available to other receiver algorithms as quickly as possible after it is received. 
         [0009]    For example, if information regarding the transmitted codes is signaled during timeslot n of frame k, then it would most benefit the receiver to have the signaled information available to demodulate the data in timeslot n or the first timeslot that uses the signaled information. If that were not possible, the next best design would make the information available to demodulate data in timeslot n+1, then n+2, and so on. If it is not possible to extract the information during frame k, it would benefit the receiver to make the information available as soon as possible afterwards such as at the end of frame k, during frame k+1, or frame k+2, and so on. Finally, if it is not possible to extract the information during the TTI, it would benefit the receiver to make the information available as soon as possible afterwards such as at the end of the TTI, during the next TTI, and so on. 
         [0010]    The delay between when signaled information about transmitted codes arrives at the receiver antenna and when the information is made available to elements of the receiver for improved demodulation performance depends on the receiver architecture. In particular, limiting factors may include the latency in signal processing paths, the amount of memory that is provided to store received samples, the clock speed of the hardware, the processing speed of a microprocessor or DSP chip, DC power limitations, the maximum number of gates, and other similar structural limitations. 
         [0011]    The Third Generation Partnership Project (3GPP) time division duplex (TDD) system, including both high and low chip rate options, and the time division-synchronous code division multiple access (TD-SCDMA) system are examples of CDMA systems that employ multi-user detection and are partitioned into TTIs, frames, and timeslots. In these systems one or more channelization codes in one or more timeslots are allocated to coded composite transport channels (CCTrCHs). In each timeslot, multiple CCTrCHs may be transmitted and may be directed to one or more UEs. 
         [0012]    During call set-up, a CCTrCH is provided with an allocation of channelization codes and timeslots which are signaled to the UE. Even though the UE has a list of allocated codes, not all of the allocated codes are used in every transmission. Thus, the UE has partial information regarding own-UE codes. Also, the list of other-UE codes is not available, except in certain cases where some hint as to the total number of codes is indicated through physical layer signaling. 
         [0013]    Each transmitted code is a combination of a channelization code, a channelization code specific multiplier, and a scrambling code as defined in Technical Specification Group Radio Access Network, Spreading and modulation (TDD), Release 4, 3GPP TS 25.223 V4.1.0 (2001-06). The scrambling code is signaled to the UE well before data demodulation initiates. The code specific multipliers are a priori associated with channelization codes, so the identity of the channelization code itself is the only one of the three that needs to be determined. BCD determines the identity of the transmitted codes by combining information that is signaled with code detection algorithms that operate on the received data. The output of BCD is a list of channelization codes that is provided to the MUD. The MUD also requires information about midamble offsets and spreading factors associated with the codes, which are also included in the BCD output. 
         [0014]    If a code allocated to a CCTrCH is not transmitted, then the CCTrCH is in discontinuous transmission (DTX). A CCTrCH is said to be in “partial DTX” if not all of the allocated codes are transmitted in a given frame. It is said to be in “full DTX” if none of the allocated codes are transmitted in a frame. Techniques to monitor whether a CCTrCH is in full DTX and provide the information to BCD are disclosed in U.S. patent application Ser. No. 10/196,857 filed Jul. 16, 2002, which is incorporated by reference as if fully set forth herein. That application provides an improved method to inform BCD if a CCTrCH is in full DTX and to monitor when the CCTrCH exits full DTX. The improvement makes the information available to BCD without having to wait for the output of certain other receiver algorithms. 
         [0015]    The identity of transmitted codes for an entire frame can be derived from the Transport Format Combination Indicator (TFCI) that is signaled to the UE and is multiplexed with the data signal as described in Technical Specification Group Radio Access Network, Physical channels and mapping of transport channels onto physical channels (TDD), Release 4, 3GPP TS 25.221 V4.1.0 (2001-06). The TFCI is transmitted in the first timeslot of every frame allocated to a CCTrCH, and optionally in subsequent timeslots in the frame. Each UE can process the received TFCI to determine the transmitted own-UE codes in each timeslot of the frame. However, this requires demodulating received data symbols and executing various other algorithms to decode and interpret the TFCI information. In a particular receiver implementation, the inherent latency of these processes could result in the identity of transmitted own-UE codes not being available when received data in the first, and possibly some subsequent, timeslots in the frame are processed in the MUD. BCD uses own-UE code information from TFCI processing when available; however, it will also function when such information is not available, though possibly with degraded performance. 
         [0016]    A CCTrCH can comprise multiple transport channels (TrCHs). Each TrCH may have its own TTI. For a 3GPP system, per Technical Specification Group Radio Access Network, Multiplexing and channel coding (TDD), Release 4, 3GPP TS 25.222 V4.1.0 (2001-03), paragraph 4.2, a TTI may be 10, 20, 40, or 80 ms corresponding to one, two, four, or eight ten-millisecond frames. The TFCI and the transmitted codes remain constant for the shortest TTI among all TrCHs in the CCTrCH. Thus the TFCI word may be repeated multiple times per frame and multiple times across several frames. The shortest TTI among all TrCHs in the CCTrCH will be referred to as TTI min . 
       SUMMARY 
       [0017]    The present invention provides methods to extract signaled information and provide it to the receiver as soon as possible after receipt and with as little additional signal processing as possible. This invention also provides a means to use repeated TFCIs to reduce complexity or improve performance. 
         [0018]    In general, a receiver may be configured to process more than one CCTrCH. This invention is described in the context of processing one CCTrCH; however, multiple processes can operate in parallel to support multiple CCTrCHs. 
         [0019]    The present invention is described in the context of operating with a receiver including BCD and a MUD. However, the present invention also has application to other CDMA receiver algorithms that benefit from a timely and accurate list of transmitted codes including, but not limited to, RAKE receivers, parallel interference cancellation (PIC), successive interference cancellation (SIC), and single user detectors. 
         [0020]    A method for performing transport format combination indicator (TFCI) processing in a wireless communications system begins by collecting received samples for a timeslot. Processing of the received samples for the timeslot that does not require a transport format combination (TFC) code list or a TFC code list valid indicator is performed. Next, a TFCI value for the timeslot is received and is processed at the timeslot rate, producing the TFC code list and the TFC code list valid indicator. Then processing in the timeslot that requires the TFC code list or the TFC code list valid indicator is performed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawings wherein: 
           [0022]      FIG. 1  ( FIG. 1A  and  FIG. 1B ) is a block diagram of a receiver constructed in accordance with the present invention; 
           [0023]      FIG. 2  is a timing diagram of a fast TFCI processing algorithm according to the present invention; 
           [0024]      FIG. 3  is a flowchart of the fast TFCI processing algorithm shown in  FIG. 2 ; 
           [0025]      FIG. 4  ( FIG. 4A  and  FIG. 4B ) is a block diagram of an alternate embodiment of a receiver constructed in accordance with the present invention; 
           [0026]      FIG. 5  is a timing diagram of an alternate fast TFCI processing algorithm according to the present invention; 
           [0027]      FIG. 6  is a flowchart of the alternate fast TFCI processing algorithm shown in  FIG. 5 ; 
           [0028]      FIG. 7  is a flowchart showing a full DTX control algorithm in accordance with the present invention; 
           [0029]      FIG. 8   a  is a flowchart showing the use of the TFCI value from the first allocated timeslot in a frame; 
           [0030]      FIG. 8   b  is a flowchart showing the use of the TFCI value from the first allocated timeslot in a minimum TTI; and 
           [0031]      FIG. 8   c  is a flowchart showing the use of TFCI values from multiple timeslots. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]      FIG. 1  ( FIG. 1A  and  FIG. 1B ) is a receiver  100  constructed in accordance with the present invention and shows only those portions of the receiver  100  that are necessary for the understanding of the present invention. Additional portions of the receiver  100  that are necessary for operation include those portions that are known in the art and are not shown. An automatic gain control (AGC)  102  processes received signals and outputs received samples  104 , as is known in the art. A preprocessing block  110  operates on the received samples and includes such functions as channel estimation, midamble cancellation, A matrix construction, and midamble power estimation. The preprocessing block  110  outputs a detected midamble list and detected midamble offsets  112 , channel estimates  114 , detected midamble powers  116 , an A matrix  118  (which is the system matrix for the multi-user detector (MUD)  170 ), data fields  120 , and a noise estimate  122 . While the preprocessing block  110  is shown as a single entity for sake of simplicity, it may comprise several different blocks. 
         [0033]    A blind code detection (BCD) block  130  includes a candidate code list generator  140 , a code energy measurement block  150 , and a code detector  160 . The candidate code list generator  140  receives a midamble scheme  142 , a physical channel map  144 , and the detected midamble list and detected midamble offsets  112  as inputs and generates a candidate code list  146  as an output. The code energy measurement block  150  receives the channel estimates  114 , the A matrix  118 , and the data fields  120  as inputs and generates a signal containing the normalized energy for all codes  152  as an output. The code detector  160  receives the candidate code list  146 , the normalized energy signal  152 , a TFC code list valid flag  248 , and a full DTX indicator flag  282  as inputs. The code detector  160  generates channelization codes, midamble offsets, and spreading factors  162  as outputs. The channelization codes is a list of codes that the MUD  170  demodulates. 
         [0034]    The function of the BCD block  130  is to provide the MUD  170  with a master list of codes to demodulate in each timeslot. The BCD block  130  performs an estimation of the codes. The reason for the estimation is that the BCD block  130  essentially operates under a “chicken and egg” scenario, in which a determination of what to demodulate is based upon what has actually been demodulated. As time progresses during a frame, the estimation becomes more accurate, but at the beginning of a frame, the estimate is made based upon other measurements. Performance of the BCD block  130  is improved by providing as much a priori information as possible regarding the transmitted codes. The BCD block  130  operates in a manner similar to that described in U.S. application Ser. No. 10/396,992 filed Mar. 25, 2003, which is incorporated by reference as if fully set forth herein. 
         [0035]    The MUD  170  receives the detected midamble powers  116 ; the A matrix  118 ; the data fields  120 ; the noise estimate  122 ; and the channelization codes, midamble offsets, and spreading factors  162  as inputs. The MUD  170  processes these signals as is known in the art and generates soft data symbols  172  and soft transport format combination indicator (TFCI) symbols  174 . The TFCI symbols  174  are used to determine which codes are assigned to the receiver  100 . 
         [0036]    A signal to interference ratio (SIR) measurement block  180  receives the channelization codes, midamble offsets, and spreading factors  162  and the soft data symbols  172  as inputs. The SIR measurement block  180  generates the SIR  182  for all codes as an output. 
         [0037]    A burst quality assignment block  190  receives the SIR  182  as an input and generates two outputs, a quality value  192  for all codes and a TFCI quality value (Q TFCI )  194  for codes having a TFCI. The quality value  192  is used by other algorithms in the receiver  100  which are not relevant to the present invention. The TFCI is carried on a particular code and will pull the SIR for that code, so that the Q TFCI    194  can be determined. 
         [0038]    The burst quality assignment block  190  maps the SIRs  182  into quality values, also referred to as Q values. For example, the Q values could be in a range from zero to one, zero to ten, zero to sixteen, or can be left as the numeric SIR value. It is possible for the SIR associated with multiple codes to be mapped to a single Q value, and is a function of the receiver  100  as to whether this type of mapping is possible. The SIR for the TFCI carrying code is mapped to the Q TFCI    194 . 
         [0039]    A full discontinuous transmission (DTX) control block  200  receives a SyncPhase value  202 , a Q 1  value  204 , a Q 2  value  206 , a TFCI value  232 , and a TFCI valid flag  250  as inputs. The SyncPhase value  202  is used to determine whether a channel has been established. The Q 1  and Q 2  values  204 ,  206  are thresholds to be applied by the full DTX control algorithm. The full DTX control block  200  generates an indicator  208  of whether the CCTrCH was in full DTX during the previous frame (shown as oldFullDTXIndicator in  FIG. 1  ( FIG. 1A  and  FIG. 1B ), which is used by the remainder of the signal processing to determine whether it can ignore certain signals based upon whether the CCTrCH is in full DTX. 
         [0040]    There are two types of DTX, partial and full. In both types of DTX, the focus is on a coded composite transport channel which can be mapped into multiple timeslots and multiple codes per timeslot, and can support a particular maximum data rate. In partial DTX, if the data rate is reduced and if the transmitter determines that it does not need all of the codes in all of the timeslots, the transmitter will not send signals for all codes in all timeslots. 
         [0041]    In full DTX, there is no data to be transmitted, so the transmitter will send a “special burst” which has a TFCI set to zero and will then go off the air for a predetermined number of frames. It is noted that while the present invention uses a TFCI set to zero, any TFCI value can be established to be the special burst value. The purpose of the special burst is to keep the receiver and the transmitter synchronized during the off-air period so that the receiver does not interpret the lack of data to mean the CCTrCH has been deleted or permanently turned off. 
         [0042]    It is important to employ a full DTX control algorithm so that the receiver can determine when the CCTrCH exits full DTX and when it should process received signals as data. If the receiver were to ignore the fact that the CCTrCH was in full DTX, it could process noise as if it were data. In such circumstances, the receiver can have a TFCI value that appears to be valid, but it will have a poor SNR because there was no data present. Since the SNR was poor, an inner loop transmit power control (TPC) bit generator  210  will generate one or more TPC bits that signal the transmitter to increase its transmitted power. The noise would then be further processed by being decoded and demultiplexed, resulting in the generation of transport blocks filled with invalid data. The CRC checks performed on these transport blocks will very likely indicate a failure. As a result, the outer loop power control will generate a higher target SIR for the inner loop power control. The net effect is that the receiver will have incorrectly signaled the transmitter to increase its power and if the transmitter complies, it would transmit excess power generating unnecessary interference, possibly disrupting performance of other receivers in the network, and wasting power. In addition, the receiver would be left with an incorrect higher target SIR for the inner loop power control which would cause it to continue to signal the transmitter to increase its transmit power even after full DTX ends. 
         [0043]    The full DTX control block  200  examines the Q TFCI    194  to determine whether the CCTrCH is still in full DTX. To illustrate this by way of example, assume that a special burst is received and that the receiver  100  is assigned TFCI values zero through 12. In the following frame, a code is received and is demodulated to have a TFCI value of 27. Because the received TFCI value is not allowed, the CCTrCH is likely still in full DTX. If the received TFCI value falls within the valid range, then the Q TFCI    194  is evaluated to determine the quality of the received TFCI value. If the Q TFCI    194  is poor, then it is likely that the CCTrCH is still in full DTX. This algorithm will be explained in greater detail below in connection with  FIG. 7 . 
         [0044]    The TPC bit generator  210  receives the SIR  182 , the old full DTX indicator  208 , and a virtual SIR value  212  as inputs. The TPC bit generator  210  generates a TPC control bit  214  which is used for inner loop power control to indicate to the transmitter whether the transmit power should be increased or decreased. The TPC bit generation algorithm compares received signal quality estimates, such as SIR, to a target value to determine whether to signal an increase or decease in power. The TPC bit generator  210  examines the SIR value (either the SIR  182  or the virtual SIR  212 ) and based upon the SIR value, will generate the control bit  214  indicating whether the base station should raise (if the SIR is low) or lower (if the SIR is high) its power. 
         [0045]    If the old full DTX indicator  208  indicates that a CCTrCH is in full DTX, then the received signal quality estimates will not be valid. Therefore, the TPC bit generator  210  will not use the SIR  182  to compute the TPC control bit  214 , but will instead use the virtual SIR  212  or some other alternate method to compute the TPC bit. The use of the old full DTX indicator  208  is one alternate algorithm that may be used to signal the full DTX state to the TPC bit generator  210 . Another alternate approach includes providing the TPC bit generator  210  with the full DTX indicator  282  from the end of full DTX detection block  280 , instead of the old full DTX indicator  208 . A further alternate approach would be to suppress the calculation of signal quality for codes associated with CCTrCHs in full DTX. If the TPC bit generator  210  receives no signal quality estimates for a CCTrCH, it uses an alternate algorithm (such as the virtual SIR  212 ) to compute the TPC bit  214 . 
         [0046]    A decoding and demultiplexing block  220  receives the soft data symbols  172  and TFC parameters  264  as inputs and outputs transport blocks  222  and cyclic redundancy checks (CRCs)  224 . The transport blocks  222  contain the demodulated data bits. The decoding and demultiplexing block  220  generates a CRC  224  for each transport block  222 . 
         [0047]    A typical implementation can ignore the full DTX state and incorrect data will be discarded when the CRC check fails. Outer loop power control typically examines the rate of CRC failures to determine if the target SIR must be increased and whether the transmitter must increase its power. If CRC failures are occurring as a result of DTX rather than insufficient transmit power, increased transmit power is not actually required. However, the receiver  100  will still signal the transmitter to increase power, thus increasing the interference to other users and wasting power at the transmitter. The present invention improves the performance of outer loop power control, and any other algorithms that examine CRC failures, by not reacting to CRC failures during full DTX, as explained below in connection with the suppress during full DTX block  270 . 
         [0048]    A TFCI decoder  230  receives the soft TFCI symbols  174  from the MUD  170  as input and outputs a TFCI value  232 . The purpose of the TFCI decoder  230  is to indicate which of the receiver&#39;s own codes have been transmitted. The TFCI value  232  is not the list of transmitted codes, but is an index to a table that contains the number of transmitted codes. As further discussed below, the table is often called a transport format combination set (TFCS). Because the TFCI value  232  gets demodulated along with the regular data received, the TFCI will not be available and cannot be used when the data contained in the first allocated timeslot of a CCTrCH in a TTI is demodulated. 
         [0049]    The combined operation of the MUD  170  and the TFCI decoder  230  will sometimes result in the output of an erroneous TFCI value  232 , which is a decoded TFCI value in the receiver that is not the same as the TFCI that was signaled by the transmitter for the current frame. An infeasible TFCI value is an erroneous TFCI value that is not a valid index of the TFCS. If the TFCI value  232  is infeasible, a process received TFCI at timeslot rate block (hereinafter “TFCI timeslot block”)  240  and a process received TFCI at frame rate block (hereinafter “TFCI frame block”)  260  will detect this condition and will not use the infeasible TFCI value  232 . The TFCI timeslot block  240  and the TFCI frame block  260  will instead use the decoded TFCI value  232  from the previous frame or from the previous TTI min  during which the CCTrCH had one or more allocated timeslots in which the TFCI value  232  was not infeasible. 
         [0050]    One alternate approach upon receipt of an infeasible TFCI value is for the TFCI timeslot block  240  and the TFCI frame block  260  to use a TFCI value  232  corresponding to the first entry in the TFCS. Another alternate approach is for the TFCI timeslot block  240  and the TFCI frame block  260  to maintain a list of recently decoded valid TFCI values  232  and select a TFCI value from the list that has been output from the TFCI decoder  230  most frequently. Regardless of the approach chosen, when the TFCI timeslot block  240  detects an infeasible TFCI value  232 , it indicates in a TFCI valid flag  250  that the received and decoded TFCI value  232  is invalid. 
         [0051]    The TFCI timeslot block  240  receives the TFCI value  232 , the physical channel map  144 , and a transport format combination set (TFCS)  244  as inputs. The TFCS  244  contains the number of codes (Ncodes) associated with each TFCI value. The TFCI timeslot block  240  outputs a TFC code list  246 , a TFC code list valid flag  248 , and the TFCI valid flag  250 . By decoding the TFCI in the timeslot, the TFCI timeslot block  240  can provide an indication of which own-UE codes have been transmitted in the timeslot that has just been processed, as well as in other timeslots that are allocated to the CCTrCH in the same TTI. If the TFCI value  232  is zero or corresponds to an entry in the TFCS, then a list of transmitted codes can be determined and is output as the TFC code list  246 . The TFC code list valid flag  248  is set to true if the TFCI has been decoded, the TFCI value  232  is not infeasible, and the TFC code list  246  has been determined. The TFCI valid flag  250  is set to true if the TFCI has been decoded and the TFCI value  232  is not infeasible. 
         [0052]    If the processing were delayed until the end of the frame, then the ability to use the own-UE code information conveyed by the TFCI to optimize the processing for the remaining timeslots is lost. The TFCI timeslot block  240  sends the TFC code list  246  to the BCD block  130 , so the MUD  170  knows as quickly as possible which codes it needs to process. The TFCI timeslot block  240  does not operate on every timeslot, but rather only operates on those timeslots that contain a TFCI. 
         [0053]    The TFCI frame block  260  receives the TFCI value  232  and a TFCS, a physical channel map (which is the physical channel map  144 ), a TFCI format/map, and a burst type as inputs  262 . The TFCI frame block  260  outputs TFC parameters  264  required by the decoding and demultiplexing block  220 . The TFC parameters  264  may be entries in the TFCS table indexed by the TFCI value  232  or may be computed from the entries. 
         [0054]    A suppress during full DTX block (hereinafter “suppress DTX block”)  270  receives the old full DTX indicator  208 , the transport blocks  222 , and the CRCs  224  as inputs. If the old full DTX indicator  208  indicates that the CCTrCH is in full DTX, then the suppress DTX block  270  prevents the reporting of CRC failures and prevents further processing of the transport blocks  222  in the receiver  100 , since the CCTrCH has been determined to be in full DTX and the transport blocks  222  and the CRCs  224  are assumed to be based on processing noise rather than a transmitted signal. If the CCTrCH is not in full DTX, then the suppress DTX block  270  outputs the transport blocks  222  and the CRCs  224  for use by other receiver processes including, but not limited to, outer loop power control. Use of the old full DTX indicator  208  is one alternate for activating the suppress DTX block  270 . Any alternate algorithm that is used to determine whether a CCTrCH is in full DTX may also be used to activate the suppress DTX block  270 . 
         [0055]    An end of full DTX detection block (hereinafter “end DTX block”)  280  receives the detected midamble powers  116 , the data fields  120 , the normalized energy for all codes  152 , and the old full DTX indicator  208  as inputs. The normalized energy for all codes  152  values includes the first code power for each coded composite transport channel. The end DTX block  280  outputs a full DTX indicator flag  282 . The end DTX block  280  performs a quick check during a timeslot to determine if the CCTrCH has exited full DTX. As a backup to the end DTX block  280 , the full DTX control block  200  is executed after the MUD  170  to help in avoiding processing timeslots while the CCTrCH is in full DTX. The end DTX block  280  will look at the first timeslot in the coded composite transport channel that is supposed to have the TFCI to attempt to determine whether the CCTrCH is in full DTX or not. 
         [0056]    There are two parts to the end of DTX detection. The first detection is performed in real time by the end DTX block  280  when a timeslot is received and before data is passed to the MUD  170 . If the end DTX block  280  indicates that the CCTrCH is in full DTX, then any data received will be ignored and not passed to the MUD  170 . Because the end DTX block  280  may have a relatively high false alarm rate, the second detection via the full DTX control block  200  assists in lowering the number of false restarts. 
         [0057]      FIGS. 2 and 3  illustrate a timing diagram and a flowchart, respectively, of a fast TFCI processing algorithm in accordance with the present invention. For sake of simplifying the discussion, steps in the flowchart of  FIG. 3  that correspond to blocks in the timing diagram of  FIG. 2  will be given like reference numerals. A timing diagram  300  shows a frame k ( 302 ) and a frame k+1 ( 304 ), each having 15 timeslots, including timeslot n ( 310 ), timeslot n+1 ( 312 ), and timeslot n+2 ( 314 ). A fast TFCI processing algorithm  320  in accordance with the present invention begins with collecting samples for timeslot n (block  322 ). The samples for timeslot n are processed by demodulating the samples after the midamble has been detected (block  324 ), which results in the soft symbols being output by the MUD. Then the TFCI value for timeslot n is received from the TFCI decoder (block  326 ). The TFCI timeslot rate processing is then executed for timeslot n (block  328 ), to produce the TFC code list and the TFC code list valid flag to the BCD algorithm (block  330 ). The BCD algorithm uses the TFC code list and the TFC code list valid flag to construct the list of channelization codes, midamble offsets, and spreading factors for the MUD for timeslot n+1 and all subsequent timeslots that have been allocated to the CCTrCH. 
         [0058]    Simultaneously with block  324 , samples are collected for timeslot n+1 (block  340 ) and put into a memory storage. Because the sample processing can take longer than one timeslot, it is necessary to collect the samples for timeslot n+1 while the samples for timeslot n are being processed; otherwise, the samples from timeslot n+1 would be lost. Next, samples for timeslot n+1 that do not need the TFC code list and the TFC code list valid flag are processed (block  342 ). Then after the TFC code list and the TFC code list valid flag have been produced (block  330 ), the samples for timeslot n+1 that require the TFC code list and the TFC code list valid flag can be processed (block  344 ). 
         [0059]    The TFCI processing algorithm  320  is considered to be “fast” because rather than waiting until the end of the frame to perform the TFCI processing, it is done as fast and as early in the frame as possible. This information is then used for the timeslot n+1 processing. 
         [0060]      FIG. 4  ( FIG. 4A  and  FIG. 4B ) is a block diagram of an alternate embodiment of a receiver  400  constructed in accordance with the present invention. Elements that are the same as in  FIG. 1  ( FIG. 1A  and  FIG. 1B ) have been given like reference numerals and operate in the same manner as discussed above in connection with  FIG. 1  ( FIG. 1A  and  FIG. 1B ). A whitening matched filter  410  receives the A matrix  118  and the data fields  120  as inputs, and extracts the soft TFCI symbols  412  and outputs them to a second TFCI decoder  420 . The second TFCI decoder  420  outputs a TFCI value  422  in a manner similar to the TFCI decoder  230 . 
         [0061]    The whitening matched filter  410  is able to extract the soft TFCI symbols  412 , because a whitening matched filter is also used in the MUD  170 . The benefit of adding the whitening matched filter  410  and the second TFCI decoder  420  is that the TFCI value  422  can be obtained faster than via the MUD  170  and the TFCI decoder  230 . The latency is reduced in both the path that feeds the TFCI value  422  to the TFCI timeslot block  240  and in providing the TFC code list  246  and the TFC code list valid flag  248  to the BCD control block  130 . By keeping both TFCI decoders  230 ,  420  in the receiver  400 , the TFCI values  232 ,  422  will be available for use in timeslot n, instead of having to wait for timeslot n+1. 
         [0062]    The processing timeline for the operation of the receiver  400  is generally the same as that shown in  FIG. 2  for the receiver  100 . An important difference is that the processing in the TFCI timeslot block  240  for timeslot n can start sooner and will finish sooner, preferably in time for the BCD  130  and subsequent receiver  400  processing, such as the MUD  170 , to use the TFC code list  246 , the TFC code list valid flag  248 , or values derived from them to process samples in timeslot n. The basic operation of the receiver  400  is as follows. First, samples received in timeslot n are collected and processed to provide the soft TFCI symbols  412  at the whitening matched filter  410  output. 
         [0063]    Then the TFCI symbols  412  for the first timeslot allocated to a CCTrCH in each TTI are extracted from the whitening matched filter  410  output. Next, the TFCI symbols  412  are decoded by the TFCI decoder  420  into the TFCI value  422 . The TFCI timeslot rate block  240  is then executed to provide the TFC code list  246  and the TFC code list valid flag  248  to the BCD block  130 . The BCD block  130  uses the TFC code list  246  and the TFC code list valid flag  248  to construct the list of channelization codes, midamble offsets, and spreading factors  162  for the MUD  170  for timeslot n and all subsequent timeslots that have been allocated to the CCTrCH. 
         [0064]      FIGS. 5 and 6  illustrate a timing diagram and a flowchart, respectively, of an alternate fast TFCI processing algorithm in accordance with the present invention. For sake of simplifying the discussion, steps in the flowchart of  FIG. 6  that correspond to blocks in the timing diagram of  FIG. 5  will be given like reference numerals. A timing diagram  500  shows a frame k ( 502 ) having 15 timeslots, including timeslot n ( 504 ) and timeslot n+1 ( 506 ). A fast TFCI processing algorithm  510  in accordance with the present invention begins with collecting samples for timeslot n (block  512 ). The samples for timeslot n that do not need the TFC code list and the TFC code list valid flag are processed (block  514 ). Then the TFCI value for timeslot n is received from the TFCI decoder (block  516 ). The TFCI timeslot rate processing is then executed for timeslot n (block  518 ), to produce the TFC code list and the TFC code list valid flag (block  520 ). Finally, the samples for timeslot n that require the TFC code list and the TFC code list valid flag are processed (block  522 ). 
         [0065]    To further improve BCD and receiver performance, the timeslot rate TFCI processing for timeslot n (block  518 ) is performed before any other data symbols in timeslot n are processed. This alternate embodiment provides the TFC code list and the TFC code list valid flag to the BCD in time to be used in all timeslots in a TTI allocated to a CCTrCH, including the first timeslot that carries the TFCI symbols. 
         [0066]    The alternate algorithm  510  can be used in connection with the alternate receiver  400  described above. By providing the whitening matched filter  410 , the algorithm  510  is able to operate quickly and produce results in timeslot n. Certain functions in the preprocessing block  110 , for example the channel estimation, need to run before the whitening matched filter  410 . These functions are among the timeslot n processing that do not need TFC code list  246  and the TFC code list valid flag  248  (block  514 ). After a certain period of time, dependent upon the length of the processing, the TFCI value is generated (block  516 ). This process is described as “faster” than that described above in connection with the receiver  100  and the MUD  170  for producing the TFCI value because the TFCI value has been obtained, passed to the BCD  130 , and the BCD  130  provides its output in time to be used by the MUD  170  in processing the signal for timeslot n. It is important that the algorithm  510  be able to have the TFCI value available before subsequent processing of the timeslot n signal, so that the subsequent processing (such as the MUD  170 ) can use the information about the transmitted codes that is conveyed by the TFCI value. 
         [0067]    Referring now to  FIG. 7 , an algorithm  600  for full DTX control begins (step  602 ) by instructing the full DTX control block to initialize the old full DTX indicator to false and instructing the end of full DTX detection block to initialize the full DTX indicator to false. Next, three flags are set as follows. A full DTX allowed flag is set based upon whether the SyncPhase is equal to one (step  604 ). If the SyncPhase is equal to one, then the receiver is in the process of setting up a channel, so full DTX is not yet applicable and the flag is set to false. If the SyncPhase is not equal to one, then the flag is set to true. A TFCI accepted flag is set to true if the quality estimate of the TFCI meets a first threshold (Q TFCI ≧Q 1 ) and if the TFCI value is valid (step  606 ); otherwise, this flag will be set to false. A special burst detected flag is set to true if the TFCI value is zero and if the quality of the TFCI meets a second threshold (Q TFCI ≧Q 2 ; step  608 ); otherwise this flag will be set to false. 
         [0068]    The flags are then evaluated to set the old full DTX indicator, based on whether the CCTrCH was in full DTX during the previous frame. A first check is made as to whether the CCTrCH is allowed to enter full DTX (step  610 ). If full DTX is not allowed, the old full DTX indicator is set to false (step  612 ) and the algorithm terminates (step  614 ). If full DTX is allowed, then a determination is made whether a special burst was received (step  620 ). If a special burst has been detected, the old full DTX indicator is set to true (step  622 ) and the algorithm terminates (step  614 ). If no special burst was detected, then a determination is made whether the TFCI is accepted (step  630 ). If the TFCI has been accepted, then the old full DTX indicator is set to false (step  612 ) and the algorithm terminates (step  614 ). If the TFCI is not accepted, then there is no change to the old full DTX indicator (step  632 ) and the algorithm terminates (step  614 ). 
         [0069]    To improve BCD and receiver performance, the codes that have not been transmitted because a CCTrCH is in full DTX are not included in the list of transmitted codes provided to the MUD. Since the first timeslot allocated to a CCTrCH in each frame always includes transmission of the TFCI-carrying code (timeslot n), information regarding the full DTX state is made available to BCD in time to be used in all timeslots in a TTI allocated to a CCTrCH that follows the first timeslot carrying the TFCI symbols. The logic to determine if a CCTrCH is in full DTX is separated into two parts: an end of full DTX detection algorithm that operates at the timeslot rate and a full DTX control algorithm that operates at the frame rate. U.S. patent application Ser. No. 10/196,857 describes an end of full DTX algorithm based on detecting the presence of a TFCI-carrying burst. That patent application also includes a “sanity check” that is similar to the full DTX control algorithm. However, the sanity check uses information that is not available until the decoding and demultiplexing algorithms are complete, and the results may not be available in time to process the next frame. The full DTX control algorithm  600  is an improvement over the sanity check in that it has lower latency. 
         [0070]    Referring now to  FIG. 8   a , a flowchart of a method  700  for using the TFCI word from the first allocated timeslot in each frame is shown. The method  700  begins (step  702 ) with a determination whether the current timeslot is the first timeslot in the frame allocated to the coded composite transport channel (CCTrCH; step  704 ). If this timeslot is the first in the frame allocated to the CCTrCH, then the decoded TFCI value from this timeslot is used to compute the TFC code list and the TFC code list valid flag (step  706 ), and the method then terminates (step  708 ). If the current timeslot is not the first in the frame allocated to the CCTrCH, then a determination is made whether the current timeslot is the last timeslot in the frame (step  710 ). If it is the last timeslot, then the method terminates (step  708 ) and the TFC code list and the TFC code list valid flag are not generated for the current frame. If the current timeslot is not the last timeslot in the frame, then the method waits for the next timeslot (step  712 ) and repeats step  704  for the next timeslot. The receiver uses the TFCI decoder output from the first timeslot allocated to the CCTrCH in each frame to compute the TFC code list and the TFC code list valid flag. Thus, the TFC code list and the TFC code list valid flag are computed only once per frame. 
         [0071]      FIG. 8   b  shows a flowchart of a method  720  for using the TFCI word from the first allocated timeslot in a minimum transmit time interval (TTI min ). The method  720  begins (step  722 ) with a determination whether the current timeslot is the first timeslot in the TTI min  allocated to the CCTrCH (step  724 ). If this timeslot is the first in the TTI min  allocated to the CCTrCH, then the decoded TFCI value from this timeslot is used to compute the TFC code list and the TFC code list valid flag (step  726 ), and the method then terminates (step  728 ). If the current timeslot is not the first in the TTI min  allocated to the CCTrCH, then a determination is made whether the current timeslot is the last timeslot in the TTI min  (step  730 ). If it is the last timeslot, then the method terminates (step  728 ) and the TFC code list and the TFC code list valid flag are not generated for the current frame. If the current timeslot is not the last timeslot in the TTI min , then the method waits for the next timeslot (step  732 ) and repeats step  724  for the next timeslot. The receiver uses the TFCI decoder output from the first timeslot allocated to the CCTrCH in TTI min  to compute the TFC code list and the TFC code list valid flag. Thus, the TFC code list and the TFC code list valid flag are computed only once per TTI min . 
         [0072]    The TTI min  becomes relevant when a CCTrCH contains multiple TrCHs multiplexed into it. Each TrCH can have a different TTI length, for example, 20, 40, or 80 milliseconds. TTI min  is the shortest TTI among all of the TrCHs that are multiplexed into the CCTrCH. The transmitted TFCI value will be constant for at least TTI min . 
         [0073]      FIG. 8   c  shows a flowchart of a method  740  for using TFCI words from multiple timeslots. The method  740  begins (step  742 ) with a determination whether the current timeslot is the first timeslot allocated to the CCTrCH (step  744 ). If this timeslot is the first timeslot allocated to the CCTrCH, then the decoded TFCI value from this timeslot is used to compute the TFC code list and the TFC code list valid flag (step  746 ). Next, a determination is made whether the current timeslot contains a repeated TFCI for the CCTrCH (step  748 ). If yes, then all of the TFCI decoder outputs are combined to obtain an improved estimate of the TFCI word (step  750 ). If the improved estimate of the TFCI word is different than the previous estimate of the TFCI word, then the improved TFCI estimate is used to construct the TFC code list and the TFC code list valid flag (step  752 ). 
         [0074]    If the current timeslot does not contain a repeated TFCI for the CCTrCH (step  748 ) or if step  752  has been executed, the next step is a determination of whether the current timeslot is the last timeslot (step  754 ). If it is the last timeslot, then the method terminates (step  756 ). If it is not the last timeslot, then the method waits for the next timeslot (step  758 ) and repeats step  744  for the next timeslot. 
         [0075]    The method  740  is applicable to any time period, whether it is a single frame or a TTI min  spanning multiple frames. If the CCTrCH has a TTI that is longer than TTI min , then the longest TTI is required to be a multiple of TTI min . In that case, the method  740  would be repeated at least every interval of TTI min . If the TFCI word decoded at the receiver is incorrect, then the TFC code list may be incorrect, which would lead to decoded data errors. The TFCI signaled to the receiver (and the transmitted code list) is constant for the number of frames corresponding to TTI min . For each CCTrCH, there is at least one TFCI transmitted per frame and possibly more. Thus, each TFCI value will be transmitted at least once and possibly multiple times per frame, and possibly in multiple frames. The TFCI processing may only use the first received TFCI; however, this does not use all possible TFCI words that have been transmitted and may lead to an unacceptably high TFCI error rate. 
         [0076]    In the method  740 , the receiver initially uses the TFCI decoder output from the first timeslot allocated to the CCTrCH in each time period (either a frame or TTI min ). If subsequent TFCI words are transmitted in a time period, then the outputs of the TFCI decoder are combined to form an improved estimate of the TFCI word. The TFCI decoder outputs may be combined by determining which TFCI word was selected most often, by soft combining the outputs corresponding to every possible TFCI word, or any other method used to combine the multiple outputs of a decoder to improve the error performance. If the improved estimate is different than the previous estimate, then the improved estimate is used to construct a new version of the TFC code list and the TFC code list valid flag. In this approach, the TFC code list and the TFC code list valid flag may be computed once or more than once per time period. Each new computation is based on a better estimate of the TFCI word, which reduces the number of TFCI errors and the number of decoded data errors. 
         [0077]    When used in conjunction with TTI min , if TTI min &gt;10 ms, then performance is further improved compared to the previous approach because there are more TFCI decoder outputs that can be combined to form a better estimate of the TFCI word. Another alternate approach is to use any combination of some or all TFCI decoder outputs within a frame or TTI min  to form a better estimate of the TFCI word. 
         [0078]    A TFCI value is valid if it equals zero, indicating a special burst, or if it corresponds to a valid entry in the TFCS. If a TFCI decoding error occurs, or if the decoded TFCI does not correspond to a valid entry in the TFCS for any other reason, then the TFC code list cannot be filled in and the TFC code list valid flag is set false. BCD nevertheless provides a list of channelization codes, midamble offsets, and spreading factors to the MUD as described in U.S. patent application Ser. No. 10/396,992. The processing of the received TFCI at the frame rate algorithm requires a TFCI value to provide TFC parameters to the decoding and demultiplexing algorithms. 
         [0079]    The present invention permits a TFCI value to be selected when the decoded TFCI is not valid. The receiver uses the decoded TFCI from the previous frame or TTI min  during which the CCTrCH had one or more allocated timeslots. An alternate approach is for the receiver to use the first entry in the TFCS. Another alternate approach is for the receiver to maintain a list of recently decoded valid TFCI words and select the value that has been decoded the most times. 
         [0080]    The present invention provides several improvements over receivers known in the art. First, in regard to the fast TFCI processing, the typical method of analyzing the TFCI was at the end of the frame. The present invention performs some TFCI processing on a timeslot basis, which permits the information contained in the TFCI to be used in timeslots during the frame in which it was received, as opposed to being limited to being used after all the timeslots in a frame have been processed or in subsequent frames. Another improvement relates to the use of the full DTX control algorithm and its interaction with the inner loop power control, outer loop power control, and processing subsequent to decoding and demultiplexing. By processing the TFCI on a timeslot basis and prior to the decoding and demultiplexing of received signals, the determination of whether the CCTrCH is in full DTX can be made sooner and the conclusion regarding the full DTX state can be used more effectively by other processing blocks. Another improvement is the use and processing of repeated TFCI transmissions to improve the likelihood of providing the correct value to subsequent processing. When a TFCI value is transmitted more than once, each repeated transmission can be used to incrementally improve the decoded TFCI value and to update the output of processing blocks that use the TFCI value. Another improvement relates to methods of determining a TFCI value when a valid TFCI word was not provided by the TFCI decoder. By using a TFCI value based on previously decoded values or valid entries in the TFCS, a valid TFCI value can be selected to process signals received in a timeslot. 
         [0081]    While this invention has been particularly shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention as described hereinabove.