Abstract:
A wireless communication method and apparatus for generating a scheduling grant based on a relative grant are disclosed. A wireless transmit/receive unit (WTRU) receives an absolute grant from a serving radio link set (RLS) and receives a relative grant from the serving RLS and at least one non-serving radio link (RL). The WTRU decodes enhanced dedicated channel (E-DCH) absolute grant channel (E-AGCH) signals to detect an absolute grant, and decodes E-DCH relative grant channel (E-RGCH) signals to detect at least one relative grant. The WTRU then calculates a serving grant based on the detected absolute grant and/or the relative grant(s). The relative grant may be detected by performing a hypothesis test on the E-RGCH signals. A multiple alternative hypothesis test is performed for detecting the E-RGCH signals from the serving RLS and a binary hypothesis test is performed for detecting the E-RGCH signals from the at least one non-serving RL.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional application No. 60/712,117 filed Aug. 29, 2005, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention is related to a wireless communication system. More particularly, the present invention is related to a wireless communication method and apparatus for generating a scheduling grant based on a relative grant received via an enhanced dedicated channel (E-DCH) relative grant channel (E-RGCH).  
       BACKGROUND  
       [0003]     Enhanced uplink (EU) is one of the major features in third generation partnership project (3GPP) frequency division duplex (FDD) systems. EU offers a peak data rate of 5.76 Mbps. In order to support EU operation, several downlink physical channels are provided to transmit control information. One of the downlink physical channels is the E-RGCH.  
         [0004]      FIG. 1  is a block diagram of a conventional wireless communication system  100  which supports EU. The system  100  comprises a wireless transmit/receive unit (WTRU)  102 , a Node-B  104  and a radio network controller (RNC)  106 . The RNC  106  controls overall E-DCH operation by configuring E-DCH parameters for the Node-B  104  and the WTRU  102 , such as initial transmit power level, maximum allowed transmit power or available channel resources per Node-B. Between the WTRU  102  and the Node-B  104 , an E-DCH  108 , an E-DCH dedicated physical control channel (E-DPCCH), an E-DCH absolute grant channel (E-AGCH)  112 , an E-RGCH  114  and an E-DCH hybrid automatic repeat request (H-ARQ) indicator channel (E-HICH)  116  are established for supporting E-DCH operations.  
         [0005]     For E-DCH transmissions, the WTRU  102  sends scheduling requests, (also known as rate requests), for the logical channels which a radio resource control (RRC) determines that reporting is needed to be made to the Node-B  104  via the E-DCH  108 . The scheduling requests are transmitted in the form of scheduling information and a happy bit. The happy bit is transmitted via the E-DPCCH  110  whenever the E-DPCCH  110  is transmitted. The Node-B  104  sends a scheduling grant to the WTRU  102  via the E-AGCH  112  or the E-RGCH  114 . The scheduling grant is one of absolute grant and a relative grant. The absolute grant is sent by an E-DCH serving radio link set (RLS) via the E-AGCH  112 , and the relative grant is sent by either the E-DCH serving RLS or an E-DCH non-serving radio link (RL) via the E-RGCH  114 . After E-DCH radio resources are allocated for the WTRU  102 , the WTRU  102  transmits uplink data via the E-DCH  108 . In response to E-DCH or E-DPCCH transmissions, the Node-B  104  sends an acknowledgement (ACK) or a non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH  116 .  
         [0006]     The E-AGCH  112  carries the absolute grant in the form of a maximum power ratio for the WTRU  102 . The maximum power ratio is given by the ratio of enhanced uplink dedicated physical data channel (E-DPDCH) over dedicated physical control channel (DPCCH) power. The E-RGCH  114  carries the relative grant. The relative grant indicates power (or power ratio) up or down commands to adjust the absolute grant. The E-DCH serving RLS may send UP, DOWN or HOLD commands. The E-DCH non-serving RL may send UP or HOLD commands. The UP, DOWN or HOLD commands indicate an increase, decrease or no change of the maximum allowed power ratio of the WTRU  102  for the scheduled transmission of data, respectively. The commands from different non-serving RLs may be different from one another. The E-DCH non-serving RLs send the relative grant to prevent system overloading in data traffic and maintain the intra-cell and inter-cell interference at the required level.  
         [0007]     The successful detection and decoding of the E-RGCH  114  is important for the performance of systems and the performance of enhanced uplink. Therefore, it is desirable to have a method and apparatus for efficiently detecting and decoding E-RGCH signals.  
       SUMMARY  
       [0008]     The present invention is related to a wireless communication method and apparatus for generating a scheduling grant based on a relative grant. A WTRU receives an absolute grant from a serving RLS and receives at least one relative grant from the serving RLS and at least one non-serving RL. The WTRU decodes E-AGCH signals to detect an absolute grant, and decodes E-RGCH signals to detect at least one relative grant. The WTRU then calculates a serving grant based on the detected absolute grant and/or the relative grant(s). The relative grant may be detected by performing a hypothesis test on the E-RGCH signals. A multiple alternative hypothesis test is performed for detecting the E-RGCH signals from the serving RLS, and a binary hypothesis test is performed for detecting the E-RGCH signals from the at least one non-serving RL. A reliability test may be further performed on the E-RGCH signals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein:  
         [0010]      FIG. 1  is a block diagram of a conventional wireless communication system;  
         [0011]      FIG. 2  is a flow diagram of a process of detecting and decoding E-RGCH signals in accordance with the present invention;  
         [0012]      FIG. 3  is a block diagram of a WTRU configured in accordance with the present invention;  
         [0013]      FIGS. 4 and 5  are block diagrams of a first hypothesis test unit and a second hypothesis test unit of the WTRU of  FIG. 3 ;  
         [0014]      FIG. 6  is a flow diagram of a process of detecting a relative grant command in accordance with the present invention; and  
         [0015]      FIG. 7  is a flow diagram of a process of generating a serving grant in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     When referred to hereafter, the terminology “WTRU” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology “Node-B” includes but is not limited to a base station, a site controller, an access point (AP) or any other type of interfacing device in a wireless environment.  
         [0017]     The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components.  
         [0018]      FIG. 2  is a flow diagram of a process  200  of detecting and decoding E-RGCH signals in accordance with the present invention. E-AGCH signals received from a serving RLS via an E-AGCH are decoded to detect an absolute grant (step  202 ). E-RGCH signals received from a serving RLS, a non-serving RL, or both via an E-RGCH are decoded to detect at least one relative grant (step  204 ). A serving grant is then generated based on the detected absolute grant and/or the relative grant(s) (step  206 ).  
         [0019]      FIG. 3  is a block diagram of a WTRU  300  configured in accordance with the present invention. The WTRU  300  includes an E-AGCH decoder  302 , an E-RGCH decoder  304  and a serving grant processor  306 . The E-AGCH decoder  302  receives and decodes E-AGCH signals  301  received from the serving RLS to detect an absolute grant. The detected absolute grant is sent to the serving grant processor  306 . The E-RGCH decoder  304  receives and decodes a plurality of E-RGCH signals  303   1 - 303   L  received via the E-RGCH to detect at least one relative grant. The detected relative grant is sent to the serving grant processor  306 . The serving grant processor  306  generates a serving grant based on the absolute grant and/or the relative grant(s).  
         [0020]     The E-RGCH decoder  304  includes a first hypothesis test unit  310   1  and at least one second hypothesis test unit  310   2 - 310   L . The E-RGCH signals received from the serving RLS are soft combined before the hypothesis test and the soft combined E-RGCH signals  303   1  are sent to the first hypothesis test unit  310   1 . The first hypothesis test unit  310   1  performs a hypothesis test on the soft combined E-RGCH signals  303   1  and outputs a relative grant, (one of UP, HOLD and DOWN command), to the serving grant processor  306 . The second hypothesis test unit  310   2 - 310   L  performs a hypothesis test on the E-RGCH signals  303   2 - 303   L  received from the non-serving RL(s) and outputs at least one relative grant, (one of HOLD and DOWN command), to the serving grant processor  306 . A multiple alternative hypothesis test is performed for detecting the E-RGCH signals from the serving RLS, and a binary hypothesis test is performed for detecting the E-RGCH signals from the non-serving RL, which will be explained in detail hereinafter.  
         [0021]     The E-RGCH decoder  304  may further include reliability test units  308   1 - 308   L  to perform a signal reliability test before decoding the E-RGCH signals  303   1 - 303   L . The signal reliability tests may be performed based on signal-to-noise ratio (SNR) measurements. It should be noted that the SNR-based signal reliability test is an example and any other method may be performed. Each of the reliability test units  308   1 - 308   L  compare a measured, (or calculated), SNR of the E-RGCH against an SNR threshold. If the measured SNR is larger than the SNR threshold, the detection of the E-RGCH signals is determined to be reliable and the hypothesis test is performed subsequently. Otherwise, the detection of the E-RGCH signals is determined not to be reliable and the following hypothesis test is not performed.  
         [0022]     Assume that the E-RGCH has average energy E l  for the l-th RLS after correlation and soft combining. For a serving RLS, the UP, HOLD and DOWN commands are represented by √{square root over (E l )}, 0 and −√{square root over (E l )}, respectively. For a non-serving RL, the DOWN and HOLD commands are represented by −√{square root over (E l )} and 0, respectively. γ l  denotes the soft sample after correlation for the l-th RLS. Without loss of generality, it is assumed that the first RLS (l=1) is the serving RLS and the remaining RLSs (l=2, 3, . . . , L) are non-serving RLs. A log likelihood ratio (LLR) for the hypothesis test for detection between UP and HOLD for the serving RLS is as follows:  
               LLR   1     (   1   )       =     ln   ⁢         P   r     ⁡     (       y     (   1   )       ⁢     ❘     ⁢     H   1       )           P   r     ⁡     (       y     (   1   )       ⁢     ❘     ⁢     H   0       )                   Equation   ⁢           ⁢     (   1   )               
 
 An LLR for hypothesis tests for detection between DOWN and HOLD for the serving RLS is as follows:  
                 LLR   2     (   1   )       =     ln   ⁢         P   r     ⁡     (       y     (   1   )       ⁢     ❘     ⁢     H   2       )           P   r     ⁡     (       y     (   1   )       ⁢     ❘     ⁢     H   0       )             ;           Equation   ⁢           ⁢     (   2   )               
 
 where H 0 , H 1  and H 2  denote the hypothesis HOLD, UP and DOWN, respectively. White Gaussian noise with variance σ 2  after correlation is assumed. The relative grant is detected by comparing the LLR 1   (l)  and LLR 2   (l)  with detection thresholds, T 1   (l)  and T 2   (l) , respectively. The detection rules for the serving RLS are as follows:  
       UP   ,         if   ⁢           ⁢     LLR   1     (   1   )         =           1   σ     ⁢     y     (   1   )       ⁢       γ   1         -       1   2     ⁢     γ   1         &gt;     T   1     (   1   )           ;         
       DOWN   ,         if   ⁢           ⁢     LLR   2     (   1   )         =           1   σ     ⁢     y     (   1   )       ⁢       γ   1         -       1   2     ⁢     γ   1         &gt;     T   2     (   1   )           ;         
 
 and 
 
         [0023]     HOLD, otherwise, 
 
 where  
         γ   1     ,     (     =       E   1       σ   2         )     ,       
 
 denotes an average SNR of the E-RGCH for the serving RLS after correlation and soft combining. 
 
         [0024]     Similarly, the LLR for hypothesis tests for detection between DOWN and HOLD for the non-serving RL, (i.e., l-th RL), is as follows:  
                 LLR   2     (   l   )       =     ln   ⁢         P   r     ⁡     (       y   1     (   l   )       ⁢     ❘     ⁢     H   2       )           P   r     ⁡     (       y   1     (   l   )       ⁢     ❘     ⁢     H   0       )             ,     l   =   2     ,   3   ,   …   ⁢           ,     L   .             Equation   ⁢           ⁢     (   3   )               
 
 The relative grant is detected by comparing the LLR 2   (l)  with a detection threshold T 2   (l) . The detection rule for the non-serving RL is as follows:  
       DOWN   ,       if   ⁢           ⁢     LLR   2     (   l   )         =           1   σ     ⁢     y     (   l   )       ⁢       γ   l         -       1   2     ⁢     γ   l         &gt;     T   2     (   l   )           ,     l   =   2     ,   3   ,   …   ⁢           ,     L   ;         
        HOLD, otherwise, 
 
 where γ l , l=2, 3, . . . , L denotes an average SNR of the E-RGCH for the non-serving RL (the l-th RLS) after correlation and soft combining. Noise estimation for σ and SNR estimation for γ are required. The thresholds T 1   (l) , T 2   (l)  and T 2   (l) , l=2, 3 , . . . , L are determined based on the performance requirements of detection and designs. The optimum detection thresholds may be determined by simulations. 
       
 
         [0026]     When multiple measurements are available, detection of the E-RGCH signals may be performed by using multiple measurement hypothesis tests. It is assumed that there are M measurements. γ m   l  denotes the soft sample after correlation for the l-th RL and the m-th correlation output. Without loss of generality, it is assumed that the first RLS is the serving RLS and the remaining RLSs are the non-serving RLs. The LLR for multiple measurement hypothesis tests for detection between UP and HOLD for the serving RLS is expressed as follows:  
               LLR   1     (   1   )       =     ln   ⁢           P   r     ⁡     (       y   1     (   1   )       ,     y   2     (   1   )       ,   …   ⁢           ,       y   M     (   1   )       ⁢     ❘     ⁢     H   1         )           P   r     ⁡     (       y   1     (   1   )       ,     y   2     (   1   )       ,   …   ⁢           ,       y   M     (   1   )       ⁢     ❘     ⁢     H   0         )         .               Equation   ⁢           ⁢     (   4   )               
 
 The LLR for multiple measurement hypothesis tests for detection between DOWN and HOLD for the serving RLS is expressed as follows:  
               LLR   2     (   1   )       =     ln   ⁢           P   r     ⁡     (       y   1     (   1   )       ,     y   2     (   1   )       ,   …   ⁢           ,       y   M     (   1   )       ⁢     ❘     ⁢     H   2         )           P   r     ⁡     (       y   1     (   1   )       ,     y   2     (   1   )       ,   …   ⁢           ,       y   M     (   1   )       ⁢     ❘     ⁢     H   0         )         .               Equation   ⁢           ⁢     (   5   )               
 
 The relative grant is detected by comparing the LLR 1   (l)  and LLR 2   (l)  with detection thresholds, T 1   (l)  and T 2   (l) , respectively. The detection rules for the serving RLS using multiple measurement hypothesis tests is as follows:  
       UP   ,         if   ⁢             ⁢             ⁢     LLR   1     (   1   )         =         ∑     m   =   1     M     ⁢     (         1   σ     ⁢     y   m     (   1   )       ⁢       γ   1         -       1   2     ⁢     γ   1         )       &gt;     T   1     (   1   )           ;         
       DOWN   ,         if   ⁢           ⁢     LLR   2     (   1   )         =         ∑     m   =   1     M     ⁢     (         1   σ     ⁢     y   m     (   1   )       ⁢       γ   1         -       1   2     ⁢     γ   1         )       &gt;     T   2     (   1   )           ;         
 
 and 
 
         [0027]     HOLD, otherwise.  
         [0028]     Similarly, the LLR for hypothesis tests for detecting between DOWN and HOLD for the non-serving RL using multiple measurement hypothesis is as follows:  
                 LLR   2     (   l   )       =     ln   ⁢         P   r     ⁡     (       y   1     (   l   )       ,     y   2     (   l   )       ,   …   ⁢           ,       y   M     (   l   )       ⁢     ❘     ⁢     H   2         )           P   r     ⁡     (       y   1     (   l   )       ,     y   2     (   l   )       ,   …   ⁢           ,       y   M     (   l   )       ⁢     ❘     ⁢     H   0         )             ,     l   =   2     ,   3   ,   …   ⁢           ,   L           Equation   ⁢           ⁢     (   6   )               
 
 The relative grant is detected by comparing the LLR 2   (l)  with a detection threshold T 2   (l) . The detection rule for the non-serving RL using multiple hypothesis tests is as follows:  
       DOWN   ,         if   ⁢           ⁢     LLR   2     (   l   )         =         ∑     m   =   1     M     ⁢           ⁢     (         1   σ     ⁢     y   m     (   l   )       ⁢       γ   l         -       1   2     ⁢     γ   l         )       &gt;     T   2     (   l   )           ;         
 
 and 
 
         [0029]     HOLD, otherwise.  
         [0000]     The thresholds T 1   (l) , T 2   (l)  and T 2   (l) , l=2, 3, . . . , L above are determined based on the performance requirements of detection and designs. The optimum detection thresholds can be determined by simulations.  
         [0030]      FIG. 4  is a block diagram of a first hypothesis test unit  310   1  in accordance with the present invention. The first hypothesis test unit  310   1  includes a first LLR calculation unit  402 , a second LLR calculation unit  404  and a threshold unit  406 . The first LLR calculation unit  402  calculates a first LLR of a conditional probability that an UP command is detected to a conditional probability that a HOLD command is detected based on the received E-RGCH signals  303   1 . The second LLR calculation unit  404  calculates a second LLR of a conditional probability that a DOWN command is detected to a conditional probability that a HOLD command is detected based on the received E-RGCH signals  303   1 . The threshold unit  406  compares the first LLR with a first detection threshold and the second LLR with a second detection threshold. The threshold unit  406  then outputs an UP command if the first LLR is equal to or greater than the first detection threshold and outputs a DOWN command if the second LLR is equal to or greater than the second detection threshold. Otherwise, the threshold unit  406  outputs a HOLD command.  
         [0031]      FIG. 5  is a block diagram of a second hypothesis test unit  310   2 - 310   L  in accordance with the present invention. The second hypothesis test unit  310   2 - 310   L  includes a second LLR calculation unit  502  and a threshold unit  504 . The LLR calculation unit  502  calculates an LLR of a conditional probability that a DOWN command is detected to a conditional probability that a HOLD command is detected based on the received E-RGCH signals  303   1 - 303   L . The threshold unit  504  compares the LLR with a detection threshold. The threshold unit  504  then outputs a DOWN command if the LLR is equal to or greater than the detection threshold. Otherwise, the threshold unit  504  outputs a HOLD command.  
         [0032]      FIG. 6  is a flow diagram of a process  600  of detecting a relative grant command in accordance with the present invention. A WTRU receives E-RGCH signals from a serving RLS and/or at least one non-serving RL (step  602 ). There may be zero, one or more than one non-serving RLs. The WTRU selects E-RGCH signals from the first RLS (step  604 ). An optional reliability test is then performed at step  606 . For example, the reliability test may be performed by determining whether an SNR of the E-RGCH is equal to or greater than an SNR threshold. If the SNR of the E-RGCH is less than the SNR threshold, E-RGCH signals from the next RLS are selected at step  632  and the process  600  returns to step  606 .  
         [0033]     If the reliability test passes, (i.e., the SNR of the E-RGCH is equal to or greater than the SNR threshold), it is further determined whether the received E-RGCH signals are from the serving RLS or the non-serving RL (step  608 ). If the received E-RGCH signals are from the serving RLS, a first LLR is calculated (step  610 ). It is then determined whether the first LLR is higher than a first detection threshold (step  612 ). If the first LLR is higher than the first detection threshold, an UP command is detected (step  614 ). If not, a second LLR is calculated (step  616 ). It is then determined whether the second LLR is higher than a second detection threshold (step  618 ). If the second LLR is higher than the second threshold, a DOWN command is detected (step  620 ). If not, a HOLD command is detected (step  622 ).  
         [0034]     If, in step  608 , it is determined that the received E-RGCH signals are from the non-serving RL, a second LLR is calculated (step  624 ). It is then determined whether the second LLR is higher than a second detection threshold (step  626 ). If the second LLR is higher than the second detection threshold, a DOWN command is detected (step  628 ). If not, a HOLD command is detected (step  630 ).  
         [0035]      FIG. 7  is a flow diagram of a process  700  for generating a serving grant in accordance with the present invention. A WTRU monitors scheduling grants, (i.e., an absolute grant and relative grant(s)), from a serving RLS and at least one non-serving RL (step  702 ). It is then determined whether there is an absolute grant or a relative grant received from the serving RLS (step  704 ). If there is an absolute grant or a relative grant received from the serving RLS, a first serving grant candidate is calculated based on the absolute grant or the relative grant (step  706 ). It is then determined whether there is at least one DOWN command received from the non-serving RL(s) (step  708 ). If a DOWN command is not received from the non-serving RL(s), a new serving grant is set to the first serving grant candidate (step  710 ) and the process  700  waits for the next transmission time interval (TTI) at step  722  before proceeding to step  704 . If there is a DOWN command received from the non-serving RL, a second serving grant candidate is calculated based on the DOWN command and a previous serving grant (step  712 ). A new serving grant is then set to a minimum one of the first serving grant candidate and the second serving grant candidate (step  714 ) and the process  700  waits for the next TTI at step  722  before proceeding to step  704 . The new serving grant is set to the minimum one because the serving cell may reduce the scheduling grant by more than the relative grant down step size.  
         [0036]     If, in step  704 , it is determined that there is no absolute grant and relative grant received from the serving RLS, it is further determined whether there is a DOWN command received from the non-serving RL (step  716 ). If there is no DOWN command received from the non-serving RL, the process  700  returns to step  702  to monitor the scheduling grants. If there is a DOWN command received from the non-serving RL, a second serving grant candidate is calculated based on the DOWN command and a previous serving grant (step  718 ). A new serving grant is then set to the second serving grant candidate (step  720 ) and the process  700  waits for the next TTI at step  722  before proceeding to step  704 .  
         [0037]     Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention.