Abstract:
A method for generating a serving grant at a wireless transmit/receive unit is disclosed. An absolute grant channel signal is decoded to obtain an absolute grant from a serving cell. A relative grant channel signal is decoded to obtain a relative grant from a serving radio link set and a relative grant from a non-serving radio link. A first serving grant candidate is generated based on the absolute grant from the serving cell or the relative grant from the serving radio link set. A second serving grant candidate is generated based on the relative grant from the non-serving radio link. The serving grant is generated based on the first serving grant candidate and the second serving grant candidate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/477,279, filed Jun. 29, 2006, which claims the benefit of U.S. Provisional Patent Application No. 60/712,307, filed Aug. 30, 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 method and apparatus for processing enhanced uplink (EU) scheduling grants. 
       BACKGROUND 
       [0003]    EU is one of the major features in the third generation partnership project (3GPP) system. EU offers a peak data rate of 5.76 Mbps. In order to support EU operation, several downlink physical channels, such as an enhanced dedicated channel (E-DCH) absolute grant channel (E-AGCH) and an E-DCH relative grant channel (E-RGCH), are provided to transmit control information. 
         [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 an 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 power ratio, 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-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 (i.e., an absolute grant (AG) or a relative grant (RG)) to the WTRU  102  via the E-AGCH  112  or the E-RGCH  114 . The AG is sent by an E-DCH serving cell, and the RG is sent by either an E-DCH serving radio link set (RLS) or an E-DCH non-serving radio link (RL). The E-DCH serving cell is a cell from which the WTRU receives AGs from a Node-B scheduler. A WTRU has one E-DCH serving cell. The E-DCH serving RLS is a set of cells which contains at least the E-DCH serving cell and from which the WTRU shall receive an AG. The WTRU has only one serving RLS. The non-serving RL is a cell which belongs to the E-DCH active set but does not belong to the serving RLS and from which the WTRU may receive an RG. The WTRU may have zero, one or several non-serving RL(s). 
         [0006]    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 . 
         [0007]    The E-AGCH  112  carries an AG which includes an AG value and an activation flag. The AG value is provided in the form of a maximum power ratio for the WTRU. The maximum power ratio is given by the ratio of E-DCH dedicated physical data channel (E-DPDCH) over dedicated physical control channel (DPCCH) power. The activation flag is used to activate or deactivate the H-ARQ processes. The activation flag may be set to either “SINGLE” or “ALL.” If the activation flag is set to “SINGLE”, a single H-ARQ process is activated or deactivated. If the activation flag is set to “ALL”, all H-ARQ processes are activated or deactivated. 
         [0008]    The E-RGCH  114  carries an RG. The RG indicates power (or power ratio) up or down commands to adjust the absolute grant. The serving RLS may send UP, DOWN or HOLD commands and the non-serving RL may send DOWN 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 for the scheduled transmission of data, respectively. The commands from different non-serving RLs are independent and may be different from one another. The E-DCH non-serving RLs send the RG to prevent system overloading in data traffic and maintain the intra-cell and inter-cell interference at the required level. 
         [0009]    A network may control single WTRU or a group of WTRUs via the E-AGCH, the E-RGCH, or both. When in a primary AG mode, the Node-B controls the resource scheduling for only a particular WTRU via the E-AGCH. When in a secondary AG mode, the Node-B controls the resource scheduling for a group of WTRUs via the E-AGCH. The E-AGCH is transmitted with an E-DCH radio network temporary identifier (E-RNTI). Two E-RNTIs may be configured for the WTRU at a time. One is a primary E-RNTI and the other is a secondary E-RNTI. Only one E-RNTI may be transmitted in the air at a time. The WTRU should monitor both E-RNTIs if the WTRU is configured with both E-RNTIs. 
         [0010]    The WTRU calculates and sets a serving grant (SG) based on the received AG and RG. A successful detection and decoding of the E-AGCH  112  and the E-RGCH  114  and proper setting of the SG are important for the performance of systems and the performance of EU. Therefore, it is desirable to have a method and apparatus for efficiently detecting and decoding the AG and RGs and processing the SG. 
       SUMMARY 
       [0011]    The present invention is related to a method and apparatus for processing EU scheduling grants. A WTRU detects a scheduling grant including at least one of an AG or an RG. Once the WTRU detects an AG or an RG, a new SG is generated and an H-ARQ process may be activated or deactivated depending on whether the received AG is a primary AG or a secondary AG, whether a scheduling mode is a primary AG mode or a secondary AG mode, whether an AG value is set to “INACTIVE” and whether a transmission time interval (TTI) is 2 ms or 10 ms. A Node-B may send either a primary AG or a secondary AG to a WTRU. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    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: 
           [0013]      FIG. 1  is a block diagram of a conventional wireless communication system; 
           [0014]      FIG. 2  is an exemplary block diagram of a WTRU configured in accordance with the present invention; 
           [0015]      FIG. 3  is a flow diagram of a process of processing SGs in accordance with the present invention; 
           [0016]      FIGS. 4A and 4B , taken together, are a flow diagram of a process of generating SGs based on scheduling grant from the serving RLS in accordance with one embodiment of the present invention; 
           [0017]      FIGS. 5A-5C  illustrates transmission and reception for AGs and processing SGs in accordance with the present invention; 
           [0018]      FIG. 6  is a block diagram of a Node-B configured in accordance with the present invention; and 
           [0019]      FIGS. 7A and 7B , taken together, are a flow diagram of a process of generating SGs based on scheduling grant from the serving RLS in accordance with another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    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. 
         [0021]    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. 
         [0022]      FIG. 2  is an exemplary block diagram of a WTRU  200  configured in accordance with the present invention. The WTRU  200  includes an E-AGCH decoder  202 , an E-RGCH decoder  204  and an SG processor  206 . The E-AGCH decoder  202  receives, and decodes, E-AGCH signals  201   a  received from the serving RLS to detect an AG  205   a.  The detected AG  205   a  is sent to the SG processor  206 . The E-RGCH decoder  204  receives, and decodes, E-RGCH signals  201   b  from the serving RLS and E-RGCH signals  201   c  from the non-serving RL(s) to detect an RG  205   b  from the serving RLS and an RG  205   c  from the non-serving RL(s), respectively. The detected RGs  205   b,    205   c  are sent to the SG processor  206 . The E-AGCH decoder  202  indicates to the SG processor  206  whether the AG  205   a  was received with a primary E-RNTI or a secondary E-RNTI. The E-AGCH  202  and the E-RGCH  204  also indicate which sub-frame the scheduling grant (i.e., AG  205   a  or RG  205   b,    205   c ) was received in. 
         [0023]    The SG processor  206  generates a current SG based on the AG and/or the RG. The SG processor  206  includes a first SG calculator  208 , a second SG calculator  210  and a controller  212 . The first SG calculator  208  receives an AG  205   a  and an RG  205   b  from the serving RLS and calculates a first SG candidate  209   a.  The second SG calculator  210  receives at least one RG  205   c  from the non-serving RL(s) and calculates a second SG candidate  209   b.  The controller  212  outputs a new SG  213  based on the first SG candidate  209   a  and/or the second SG candidate  209   b.    
         [0024]    When the WTRU  200  is in an idle state, the SG processor  206  may be temporarily turned off for power saving. The latest received secondary AG and the primary AG are saved in a memory (not shown in  FIG. 2 ) and the SG processing resumes when the WTRU  200  is activated and has data for transmission. After resuming the SG processing, the saved latest received secondary AG and the primary AG are processed by the SG processor  206  and a new SG  213  is generated. 
         [0025]    The scheduling grant processor  206  provides the amount of power that can be used by a transport format combination (TFC) selection and multiplexing unit (not shown) for scheduled data dedicated channel medium access control (MAC-d) flows. This may be identified as the ratio to the DPCCH power. Alternatively, this may be identified by the maximum transmit power that can be used for scheduled data to avoid the TFC selection and multiplexing unit to be aware of the DPCCH power measurements. The latter method is preferable since other scheduling related entities do not have to know the current DPCCH power. 
         [0026]      FIG. 3  is a flow diagram of a process  300  of processing SGs in accordance with the present invention. A WTRU monitors scheduling grants (i.e., an AG and an RG) from a serving RLS and at least one non-serving RL (step  302 ). It is then determined whether there is an AG or an RG received from the serving RLS (step  304 ). If there is an AG or an RG received from the serving RLS, a first SG candidate is calculated based on the AG and/or the RG that come from serving RLS (step  306 ). It is then determined whether there is a DOWN command received from the non-serving RL(s) (step  308 ). If no DOWN commands are received from the non-serving RL(s), a new SG is set to the first SG candidate (step  310 ) and the process  300  waits for the next transmission time interval (TTI) at step  322  before proceeding to step  304 . If there is a DOWN command received from the non-serving RL(s), a second SG candidate is calculated based on the received DOWN command and a previous SG (step  312 ). A new SG is then set to a minimum one of the first SG candidate and the second SG candidate (step  314 ) and the process  300  waits for the next TTI at step  322  before proceeding to step  304 . The new SG may be set to the minimum of the first SG candidate and the second SG candidate because the serving cell may reduce the scheduling grant by more than the RG down step size. 
         [0027]    If, in step  304 , it is determined that there is no AG or RG received from the serving RLS, it is further determined whether there is a DOWN command received from the non-serving RL(s) (step  316 ). If there is no DOWN command received from the non-serving RL, the process  300  returns to step  302  to monitor the scheduling grants. If there is a DOWN command received from the non-serving RL, a second SG candidate is calculated based on the DOWN command and a previous SG (step  318 ). A new SG is then set to the second SG candidate (step  320 ) and the process  300  waits for the next TTI at step  322  before proceeding to step  304 . 
         [0028]      FIGS. 4A and 4B , taken together, are a flow diagram of a process  400  of generating SGs based on a scheduling grant from the serving RLS in accordance with one embodiment of the present invention. A scheduling grant from a serving RLS is detected (step  402 ). It is determined whether an AG is detected (step  404 ). If it is determined that an AG is detected, a new SG may be generated and/or an H-ARQ process may become active or inactive depending on whether the received AG is a primary AG or a secondary AG, whether a scheduling mode is a primary AG mode or a secondary AG mode, whether an AG value is set to “INACTIVE” and whether the TTI is 2 ms or 10 ms. 
         [0029]    An AG may be either a primary AG or a secondary AG. The primary AG is an AG received with a primary E-RNTI and the secondary AG is an AG received with a secondary E-RNTI. The primary AG always resets the current SG. The secondary AG resets the current SG only if the WTRU is in a secondary AG mode. The WTRU is switched to a secondary AG mode if 1) for 10 ms TTI the AG value of the last primary AG was set to “INACTIVE”, and 2) for 2 ms TTI the AG value of the last primary AG was set to “INACTIVE” and the process activation flag was set to “ALL” (therefore, the scheduling mode is transited to a secondary AG mode). If the latest AG that affected the SG was the secondary AG, the WTRU is already in the secondary AG mode. 
         [0030]    A primary AG mode is a scheduling mode in which only a primary AG and an RG affect the SG (i.e., a secondary AG does not affect the SG). A secondary AG mode is a scheduling mode in which all of the primary AG, the secondary AG and the RG may affect the SG. When in a primary AG mode, the Node-B controls the resource scheduling for only a particular WTRU using a primary E-RNTI, and when in a secondary AG mode, the Node-B controls the resource scheduling for a group of WTRUs using a secondary E-RNTI. A primary AG whose AG value is set to “INACTIVE” triggers the transition from the primary AG mode to the secondary AG mode. 
         [0031]    If, at step  404 , it is determined that an AG is not detected, it is further determined whether the scheduling mode is a primary AG mode (step  406 ). If the scheduling mode is not a primary AG mode (i.e., it is a secondary AG mode), the process  400  proceeds to step  446  to wait for the next TTI. If the scheduling mode is a primary AG mode, the SG is set based on a received RG (it is assumed that an RG is received from the serving RLS), and the SG generated in the previous TTI for the same H-ARQ process (step  408 ). An RG received from the serving RLS is interpreted relative to the power ratio in the previous TTI for the same H-ARQ process as the transmission which the RG affects. If the RG indicates an UP command, then the SG is obtained by increasing the previous power ratio by the predetermined step size. If the RG indicates a DOWN command, the SG is obtained by decreasing the previous power ratio by the predetermined step size. If the RG indicates a HOLD command, the SG remains unchanged. 
         [0032]    If, at step  404 , it is determined that an AG is detected, it is further determined whether the AG is a primary AG or a secondary AG (step  410 ). If the AG is a primary AG, the scheduling mode is set to the primary AG mode (step  412 ). It is then further determined whether the AG value of the detected AG is set to “INACTIVE” (step  414 ). If the AG value is not set to “INACTIVE” (i.e., the AG value is set to a non-zero value), the SG is updated to the received AG value (step  416 ). It is then determined whether the TTI is 2 ms or 10 ms (step  418 ). If the TTI is 10 ms, all the H-ARQ processes are activated (step  424 ) and the process  400  proceeds to step  446  to wait for the next TTI. 
         [0033]    If the TTI is 2 ms, it is further determined whether the activation flag is set to “SINGLE” or “ALL” (step  420 ). If the activation flag is set to “SINGLE”, the particular H-ARQ process is activated (i.e., if the particular H-ARQ process is inactive, the H-ARQ process becomes active, and if the H-ARQ process is active, the H-ARQ process remains active) (step  422 ). If the activation flag is set to “ALL”, all H-ARQ processes are activated (i.e., inactive H-ARQ processes becomes active and active H-ARQ processes remain active) (step  424 ). An active process is an H-ARQ process for which scheduled data may be sent and an inactive process is an H-ARQ process for which non-scheduled data may be sent. 
         [0034]    If, at step  414 , it is determined that the AG value of the received AG is set to “INACTIVE”, it is further determined whether it is 2 ms or 10 ms TTI (step  425 ). If it is 2 ms TTI, it is further determined whether the activation flag is set to “SINGLE” or “ALL” (step  426 ). If the activation flag is set to “SINGLE”, only the particular H-ARQ process becomes inactive (step  428 ). If the activation flag is set to “ALL”, it is further determined whether a secondary E-RNTI is configured (step  430 ). If it is determined at step  425  that it is 10 ms TTI, the process  400  proceeds to step  430 . If the secondary E-RNTI is not configured, all H-ARQ processes are deactivated (step  432 ). If the secondary E-RNTI is configured, the current SG may be updated to the latest received AG value (step  434 ) (which will be explained in detail with reference to  FIGS. 5A-5C ). Alternatively, the SG value may not be changed and the previous SG value may remain the same. In such case, the step  434  is bypassed and the process  400  proceeds to step  436 . All H-ARQ processes are then activated and the scheduling mode is set to the secondary AG mode (steps  436 ,  438 ). 
         [0035]    If, at step  410 , it is determined that the AG is not a primary AG (i.e., the AG is a secondary AG), it is further determined whether the scheduling mode is a secondary AG mode (step  440 ). If the scheduling mode is the secondary AG mode (therefore, the secondary AG may affect the current SG), the current SG is set based on the AG value of the received AG (step  442 ). If the scheduling mode is not a secondary AG mode, (therefore, the secondary AG may not affect the current SG), the AG value of the received AG is saved in a memory and may be used later (which will be explained in detail with reference to  FIGS. 5A-5C ) (step  444 ). 
         [0036]      FIGS. 5A-5C  illustrate exemplary Node-B scheduling with a primary AG and a secondary AG in accordance with the present invention. A Node-B transmits either a primary AG or a secondary AG to the WTRU. The scheduling grant mode switches between a primary AG mode and a secondary AG mode. The primary AG always resets the current SG. The secondary AG only affects the current SG if the current scheduling mode is set to a secondary AG mode (i.e., when the last primary AG triggers the transition to the secondary AG mode), or if the latest AG that affected the SG was the secondary AG. Hereinafter, it is assumed that the initial state is a primary AG mode. However, the present invention is equally applicable to the case when the initial configuration is in a secondary AG mode. 
         [0037]    Referring to  FIG. 5A , a Node-B first sends a secondary AG  502 . Since the current scheduling mode is a primary AG mode, the AG value in the received secondary AG  502  is saved. The next AG is a primary AG  504  with an AG value set to “INACTIVE.” This triggers a transition from the primary AG mode to the secondary AG mode as indicated by a down arrow  522 . 
         [0038]    When the scheduling mode is switched from the primary AG mode to the secondary AG mode, the SG may remain the same as the previous SG in the transition period of scheduling mode switching and the SG is updated when the next AG (in this case AG  506 ) is received. Alternatively, the SG may be set to the latest received and saved secondary AG value (in this example, the AG  502 ) in transition period of scheduling mode switching to avoid the delay of SG update. 
         [0039]    The next two AGs  506 ,  508  are secondary AGs and the SG is updated with the AG values of the secondary AGs  506 ,  508 , respectively. The next AG is a primary AG  510 . The receipt of a primary AG while in a secondary AG mode triggers a transition back to the primary AG mode as indicated by an up arrow  524 . 
         [0040]    After two primary AGs are sent, a primary AG  512  with the AG value set to “INACTIVE” is received. This triggers switch of the scheduling mode back to the secondary AG mode as indicated by a down arrow  526  and the SG may remain the same and updated when the next secondary AG (in this example, the AG  513 ) is received. Alternatively, the SG may be updated with the latest secondary AG (in this example, the AG  508 ) in the scheduling mode transition period to avoid the delay of SG update. 
         [0041]    A potential problem is that the last saved secondary AG value may be out-of-date when the system stays in a primary AG mode for too long. For example, when the WTRU receive a primary AG  516 , the system has stayed in a primary AG mode for 6 TTIs and the last secondary AG  514  may be out-of-date. 
         [0042]      FIG. 5B  shows another exemplary Node-B scheduling with a primary AG and a secondary AG in accordance with the present invention. In this embodiment, the Node-B sends a secondary AG right before switching to the secondary AG mode. In  FIG. 5B , the transmission sequence of AGs is same to the case in  FIG. 5A , except the Node-B sends a secondary AG  520  just before sending the primary AG  516 . The scheduling mode has been switched from the secondary AG mode to the primary AG mode as indicated by an up arrow  528  when the primary AG  518  is received. The Node-B sends the secondary AG  520  just before switching the scheduling mode to the secondary AG mode (i.e., just before sending a primary AG  516  with an AG value set to “INACTIVE”). The AG value in the secondary AG  520  is saved and used when the scheduling mode is switched to the secondary AG mode as indicated by a down arrow  530  when the primary AG  516  is received. With this scheme, an out-of-date secondary AG may be avoided. 
         [0043]    Alternatively, the Node-B may use a time threshold to detect an out-of-date problem as shown in  FIG. 5C . The Node-B determines just before switching the scheduling mode from the primary AG mode to the secondary AG mode whether the out-of-date situation exists (i.e., whether there was any secondary AG transmitted in the time threshold from the switching point). If there was any secondary AG transmitted during the time threshold, the Node-B sends the primary AG  516  without sending the secondary AG  520 . However, if there was no secondary AG transmitted during the time period, (as shown in  FIG. 5C ), the Node-B sends the secondary AG  520  before sending the primary AG  516 . 
         [0044]    The time threshold may be implemented as a static value. Alternatively, the time threshold may be semi-statically or dynamically adjusted depending on several factors including, but not limited to, a traffic condition change rate, an interference condition variation rate, vehicle speed, or the like. If the traffic condition or interference condition change rapidly, the time threshold is adjusted to reflect the environment changes. 
         [0045]      FIG. 6  is a block diagram of a Node-B  600  configured in accordance with the present invention. The Node-B  600  includes a scheduling request processor  602  and a Node-B scheduler  604 . The scheduling request processor  602  is configured to receive and process scheduling information received from a WTRU. The Node-B scheduler  604  is configured to control resource scheduling by sending a primary AG and a secondary AG to a WTRU. The Node-B scheduler  604  controls resource scheduling for only a particular WTRU in a primary AG mode and control resource scheduling for a group of WTRUs in a secondary AG mode. 
         [0046]    In the case when the SG is set to the latest received and saved secondary AG value in transition period of scheduling mode switching in the WTRU, the Node-B scheduler  604  sends a secondary AG before switching a scheduling mode from a primary AG mode to a secondary AG mode as explained hereinabove. The Node-B scheduler  604  determines whether an out-of-date secondary AG exists before switching a scheduling mode from the primary AG mode to the secondary AG mode and switches the scheduling mode only if there is no out-of-date secondary AG exists. The Node-B scheduler  604  determines the existence of the out-of-date secondary AG by implementing a time threshold, which may be static or dynamically adjusted based on a predetermined factor. 
         [0047]      FIGS. 7A and 7B , taken together, are a flow diagram of a process  700  of generating SGs based on scheduling grant from the serving RLS in accordance with another embodiment of the present invention. The steps  702 - 724  are identical to the steps  402 - 424  in  FIG. 4A  and therefore will not be repeated herein. If, at step  714 , it is determined that the AG value of the received AG is set to “INACTIVE”, it is further determined whether the activation flag is set to “SINGLE” or “ALL” (step  726 ). If the activation flag is set to “SINGLE”, it is further determined whether it is 2 ms TTI or 10 ms TTI (step  728 ). If it is 2 ms TTI, only the particular H-ARQ process becomes inactive (step  730 ). If it is 10 ms TTI, there is no change and the process  700  proceeds to step  752  to wait for the next TTI. 
         [0048]    If, at step  726 , it is determined that the activation flag is set to “ALL”, it is further determined whether a secondary E-RNTI is configured (step  732 ). If the secondary E-RNTI is not configured, it is further determined whether it is 2 ms TTI or 10 ms TTI (step  734 ). If it is 2 ms TTI, all H-ARQ processes are deactivated (step  736 ). If it is 10 ms TTI, there is no change and the process  700  proceeds to step  752  to wait for the next TTI. 
         [0049]    If, at step  732 , it is determined that the secondary E-RNTI is configured, the current SG may be updated to the latest received AG value (step  738 ) (as explained with reference to  FIGS. 5A-5C ). Alternatively, the SG value may not be changed and the previous SG value may remain the same. In such case, the step  738  is bypassed and the process  700  proceeds to step  740 . All H-ARQ processes are then activated and the scheduling mode is set to the secondary AG mode (steps  740 ,  742 ). 
         [0050]    If, at step  710 , it is determined that the AG is not a primary AG (i.e., the AG is a secondary AG), it is further determined whether the AG value is set to “INACTIVE” (step  744 ). If the AG value is not set to “INACTIVE”, it is further determined whether the scheduling mode is a secondary AG mode (step  746 ). If the scheduling mode is the secondary AG mode, (therefore, the secondary AG may affect the current SG), the current SG is set based on the AG value of the received AG (step  748 ). If the scheduling mode is not a secondary AG mode, (therefore, the secondary AG may not affect the current SG), the AG value of the received AG is saved in a memory and may be used later, (as explained in detail with reference to  FIGS. 5A-5C ) (step  750 ). 
         [0051]    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.