Patent Abstract:
In a wireless communication system using a reference channel used for error rate measurement and associated with a plurality of transport channels multiplexed on a coded composite transport channel (CCTrCH), a method is employed for reselection of the reference channel from favorable candidate transport channels. A channel is initially selected from the plurality of multiplexed channels as the reference channel. Channels are monitored based on quantitative data content criteria to determine whether an ON or OFF state exists. A different channel is selected from the plurality of multiplexed channels as the reselected RTrCH when a better candidate transport channel in the ON state becomes available, or when the monitored RTrCH reflects an OFF state.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority from U.S. Provisional Application No. 60/414,943 filed Sep. 30, 2002, which is incorporated by reference as if fully set forth herein. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates in general to reference transport channels (RTrCHs) in wireless communications, and in particular to a method and apparatus for RTrCH reselection implementation.  
         BACKGROUND OF THE INVENTION  
         [0003]    As used herein, a wireless transmit/receive unit (WTRU) includes, but is not limited to, a user equipment, mobile station fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, a base station includes, but is not limited to, a base station, Node B, site controller, access point, or other interfacing device in a wireless environment.  
           [0004]    In wireless communications, one of the most important features in maintaining the communication link quality under fading and interference situations is power control. In third generation partnership program (3GPP) wideband code division multiple access (W-CDMA) systems utilizing time division duplex (TDD) mode, the UTRAN (SRNC-RRC) sets the initial target signal to interference ratio (SIR) to the WTRU at the call/session establishment and then subsequently continuously adjusts the target SIR of the WTRU during the life term of the call as dictated by the observation of the uplink (UL) block error rate (BLER) measurement.  
           [0005]    A variety of services, such as video, voice, and data, each having different Quality of Service (QoS) requirements, can be transmitted using a single wireless connection. This is accomplished by multiplexing several transport channels (TrCHs), each service on its own TrCH, onto a coded composite transport channel (CCTrCH). The transmitted information is sent in units of transport blocks (TBs). Each service&#39;s QoS requirement can be monitored on a BLER basis. The rate at which each service is transmitted is on a transmission time interval (TTI). The smallest interval is one frame of data, typically defined as 10 ms for a 3G communication system. Each frame is tracked by a system connection frame number (CFN), which is encoded into the frame header. TTIs are typically in intervals of 10 ms frame durations (i.e., 10, 20, 30, 40 ms, etc.). In particular for 3GPP systems, TTIs can only be 10, 20, 40, or 80 ms. The TTI for each service depends on the type of service and its QoS requirements. Because of these differences, a variety of TTIs associated with their respective TrCHs may exist on a single CCTrCH.  
           [0006]    In order to monitor the BLER value at a CCTrCH level, as opposed to a TrCH level, one approach is to simultaneously monitor the BLER value of each TrCH multiplexed on the CCTrCH. A drawback to this approach is the potentially excessive use of system resources to monitor more channels than may be necessary.  
           [0007]    Alternatively, in order to monitor the BLER level on a CCTrCH basis, a reference transport channel (RTrCH) may be selected among the transport channels multiplexed on the considered CCTrCH. The difficulty of this approach, especially for variable bit rate services, is the reselection of the RTrCH, since the initially selected RTrCH may become temporarily unavailable (OFF) during periods where it does not carry any data.  
         SUMMARY OF THE INVENTION  
         [0008]    A method and implementing equipment are provided for a wireless communication system wherein wireless communications between communication stations includes the transmission of a composite channel on which a plurality of channels are multiplexed. The invention is intended for such systems wherein an error rate measurement is performed on received signals on a reference channel selected from the plurality of multiplexed channels. The error rate measurement is conventionally used in selectively controlling transmission of the composite channel, such as in power control for example.  
           [0009]    A preferred method includes selecting a channel from the plurality of multiplexed channels as the reference channel initially used for error rate measurement. The reference channel is monitored based on quantitative data content criteria to determine an ON state when the quantitative data content criteria is met, and an OFF state when the quantitative data content criteria is not met. When monitoring of the reference channel reflects an OFF state, a different channel is selected from the plurality of multiplexed channels as the reference channel.  
           [0010]    Preferably, the channels are transport channels (TrCHs), the reference channel is a reference transport channel (RTrCH), and each TrCH has a transport time interval (TTI) of a given size, of which a largest TTI size is an integer multiple, such as in a 3GPP system. In such systems, the TrCHs are multiplexed on a coded composite transport channel (CCTrCH) and a block error rate (BLER) measurement is performed on the RTrCH. Preferably, monitoring of the RTrCH is performed no less than once during each time interval corresponding to the TTI size of the RTrCH. Alternatively, the monitoring occurs upon a data reception on any TrCH.  
           [0011]    Each TrCH has a BLER requirement. Preferably, a TrCH having a least restrictive BLER requirement is selected as the RTrCH initially used for BLER measurement. While there are N number of TrCHs multiplexed onto the CCTrCH, the TrCHs are preferably assigned a preference level for selection, first through N th , based first on their BLER requirement and then on TTI size, such that the first TrCH has a least restrictive BLER requirement and a smallest TTI size among TrCHs having the same BLER requirement and the N th  TrCH has a most restrictive BLER requirement and a largest TTI size among TrCHs having the same BLER requirement. In such case, the first TrCH is selected as the RTrCH initially used for error rate measurement. When the first TrCH is selected as the RTrCH and monitoring of the first TrCH channel reflects an OFF state, the second TrCH is then selected as the RTrCH. Generally, when an i th  TrCH is selected as the RTrCH, where i is less than N, and monitoring of the i th  TrCH channel reflects an OFF state, a different TrCH is then preferably selected as the reselected RTrCH from among the group of channels consisting of the first TrCH through the (i+1) th  TrCH.  
           [0012]    In the general case, wherein an i th  TrCH is selected as the RTrCH, where i is less than N, monitoring can be expanded such that the first through the i th  TrCHs are monitored to determine ON and OFF states of each.  
           [0013]    In general, monitoring of a TrCH is preferably performed no less than once during each time interval corresponding to the TTI size of the TrCH. Also, the determining when a TrCH is in an OFF state preferably includes determining that data was not received on the TrCH for a predetermined number of consecutive TTIs of the TrCH. Determining when the monitored TrCH is in an ON state preferably includes determining that data was received on the TrCH in at least one of a predetermined number of TTIs of the TrCH. A TrCH having the largest TTI size defines TTI boundaries based on that largest size for all TrCHs, and the selection of a different TrCH from the plurality of multiplexed TrCH as the reselected RTrCH preferably becomes effective at one of such defined TTI boundaries.  
           [0014]    The invention includes a receiver for a communication station, either a base station or a WTRU, for use in such a wireless communication system. The receiver has composite channel signal processing circuitry that includes error measurement circuitry, monitoring circuitry, and reference channel selection circuitry. The error measurement circuitry is preferably configured to perform an error rate measurement on received signals on a selected reference channel of the composite channel. The monitoring circuitry is preferably configured to monitor the selected reference channel based on quantitative data content criteria to determine an ON state when the quantitative data content criteria is met, and an OFF state when the quantitative data content criteria is not met. The reference channel selection circuitry is preferably configured with a default channel selection and is responsive to the monitoring circuitry such that when monitoring of the reference channel reflects an OFF state, the reference channel selection circuitry selects a different channel from the plurality of multiplexed channels as the reference channel for the error measurement circuitry and the monitoring circuitry.  
           [0015]    The receiver is preferably configured for a 3GPP like system, wherein the channels are TrCHs, the reference channel is a RTrCH, each TrCH has a TTI of a given size of which a largest TTI size is an integer multiple, and the TrCHs are multiplexed on a CCTrCH. In such case, the error measurement circuitry is configured to perform a BLER measurement on the RTrCH, and the monitoring circuitry is configured to monitor the RTrCH no less than once during each time interval corresponding to the TTI size of the RTrCH.  
           [0016]    Where the TrCHs each have a block error rate (BLER) requirement, the reference channel selection circuitry is preferably configured with a TrCH having a least restrictive BLER requirement as the default TrCH selection initially used as the RTrCH. Generally, where there are N number of TrCHs multiplexed onto the CCTrCH, the reference channel selection circuitry is preferably configured to assign preference level for selection of the TrCHs, first through N th , based first on their BLER requirement and then on TTI size, such that the first TrCH has a least restrictive BLER requirement and a smallest TTI size among TrCHs having the same BLER requirement and the N th  TrCH has a most restrictive BLER requirement and a largest TTI size among TrCHs having the same BLER requirement, and the first TrCH is selected as the RTrCH initially used for error rate measurement. In such case, the reference channel selection circuitry is preferably configured such that when the first TrCH is selected as the RTrCH and monitoring of the first TrCH channel reflects an OFF state, the second TrCH is then selected as the RTrCH. A TrCH having the largest TTI size defines TTI boundaries based on that largest size for all TrCHs. The reference channel selection circuitry is preferably configured such that the selecting a different TrCH from the plurality of multiplexed TrCH as the RTrCH becomes effective at one of such defined TTI boundaries.  
           [0017]    In general, the reference channel selection circuitry is preferably configured such that when an i th  TrCH is selected as the RTrCH, where i is less than N, and monitoring of the i th  TrCH channel reflects an OFF state, a different TrCH is then selected as the RTrCH from among the group of channels consisting of the first TrCH through the (i+1) th  TrCH. In such case, the monitoring circuitry is preferably configured such that when an i th  TrCH is selected as the RTrCH, where i is less than N, the first through the i th  TrCHs are monitored based on a quantitative data content criteria to determine an ON and OFF states. Preferably, the reference channel selection circuitry is then configured such that when monitoring of the i th  TrCH channel reflects an OFF state, if any TrCH is determined to be in an ON state, the highest order TrCH that is determined to be in an ON state is then selected as the RTrCH.  
           [0018]    In general, the monitoring circuitry is preferably configured such that monitoring of a TrCH is performed no less than once during each time interval corresponding to the TTI size of the TrCH. Also, the monitoring circuitry is preferably configured such that the determining when a TrCH is in an OFF state includes determining that data was not received on the TrCH for a predetermined number of consecutive TTIs of the TrCH. One alternative is that the monitoring circuitry is configured such that the determining when TrCH is in an ON state includes determining that data was received on the TrCH in at least one of a predetermined number of TTIs of the TrCH.  
           [0019]    Other advantages will be apparent from the following description of preferred embodiments, and the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    A more detailed understanding of the invention may be had from the following description of preferred embodiments, given by way of example and to be understood in conjunction with the accompanying drawing wherein:  
         [0021]    [0021]FIG. 1A shows a block diagram of communication system;  
         [0022]    [0022]FIG. 1B shows a block diagram of a WTRU related to the present invention;  
         [0023]    [0023]FIG. 1C shows a BLER measurement unit related to the present invention;  
         [0024]    [0024]FIG. 2 shows a flow diagram of an overview of a first embodiment for RTrCH monitoring and reselection;  
         [0025]    FIGS.  3 A- 3 C show an example set of transport channels for prioritization by parameters;  
         [0026]    [0026]FIG. 4 shows a flow diagram of the monitoring of the current RTrCH in “ON” state;  
         [0027]    [0027]FIG. 5 shows a representation of a transport channel monitoring point with tolerance along the time axis;  
         [0028]    [0028]FIG. 6 shows a flow diagram of the monitoring of the current RTrCH in “OFF” state;  
         [0029]    [0029]FIG. 7 shows a flow diagram for switching of RTrCHs during reselection;  
         [0030]    [0030]FIG. 8 shows an overview of a second embodiment for RTrCH monitoring and reselection shown in FIGS. 9 and 10;  
         [0031]    [0031]FIG. 9 shows a flow diagram of the monitoring of transport channels in a hot-candidate list that are in “OFF” state;  
         [0032]    [0032]FIG. 10 shows a flow diagram of the switching of RTrCHs during reselection using a hot-candidate list;  
         [0033]    [0033]FIG. 11 shows a flow diagram of the monitoring of the current RTrCH in “ON” state at every data reception;  
         [0034]    [0034]FIG. 12 shows a flow diagram of the monitoring of the current RTrCH in “OFF” state at every data reception; and  
         [0035]    [0035]FIG. 13 shows a flow diagram of the monitoring at every data reception of transport channels in a hot-candidate list in “OFF” state. 
     
    
     ACRONYMS  
       [0036]    The following acronyms are used in this application:  
                                                       3G   Third Generation           BLER   block error rate           CCTrCH   coded composite transport channel           CFN   connection frame number           MAC   medium access control           OAM   operation, administration, and maintenance           QoS   quality of service           RNC   radio network controller           RRC   radio resource control           RTrCH   reference transport channel           SIR   signal to interference ratio           SRNC   serving RNC           TrCH   transport channel           TTI   transmission time interval           UL   uplink           UMTS   universal mobile telecommunications system           UTRAN   UMTS terrestrial radio access network           VBR   variable bit rate           WTRU   wireless receive/transmit unit                      
 
       DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0037]    Although the embodiments are described in conjunction with a third generation partnership program (3GPP) wideband code division multiple access (W-CDMA) system utilizing the time division duplex mode, the embodiments are applicable to any hybrid code division multiple access (CDMA)/time division multiple access (TDMA) communication system. Additionally, the embodiments are applicable to CDMA systems, in general, such as the proposed frequency division duplex (FDD) mode of 3GPP W-CDMA.  
         [0038]    The preferred approach for BLER measurement according to the present invention is to limit the number of TrCHs to be monitored for BLER. The first embodiment exclusively limits the BLER monitoring to a single TrCH, that being the RTrCH. FIG. 2 shows a basic flow diagram for the selection of the initial RTrCH and the subsequent reselection of the RTrCHs for when it becomes necessary to replace the current RTrCH with a better candidate. To summarize, an initial RTrCH is selected based on prioritization criteria. The RTrCH is monitored for ensuring whether it is maintaining an ON status. If it is detected that its activity falls below an acceptable level, the next best candidate TrCH is chosen as the reselected RTrCH to replace the initial RTrCH, since an RTrCH in an OFF state is not preferred for BLER measurement. The timing of the reselection is also carefully tracked to prevent the transition from occurring at an inopportune time.  
         [0039]    Each step of process  100  will now be described in further detail in reference to FIG. 2. After the step  101  start, the first step is to select the initial RTrCH in step  102 . This is achieved by assignment of a preference level PL to each TrCH multiplexed onto the CCTrCH. The TrCH with the highest preference level PL 1  is selected as the initial RTrCH. The remaining TrCHs are sorted in descending order of preference level PL.  
         [0040]    As an example, FIGS.  3 A- 3 C show a set of five transport channels TrCH 1 -TrCH 5  for mapping onto the CCTrCH. FIG. 3A shows TrCH 1 -TrCH 5  sorted by channel number, each with a respective BLER requirement and TTI size. In FIG. 3B, each preference level PL is assigned based on the BLER requirement, with highest preference given to lowest BLER requirement (i.e., the least restrictive BLER requirement), which corresponds to the highest BLER requirement value. The next parameter for assigning preference level PL is TTI size. Accordingly, transport channel TrCH 2  is assigned preference level PL 1  because it has the lowest BLER requirement, 10 2 . Transport channels TrCH 4  and TrCH 1  each have a higher BLER requirement of 10 −3 , but transport channel TrCH 4  is assigned the higher preference level PL as it has the smaller TTI size of 20 ms compared to the 40 ms TTI size of TrCH 1 . Accordingly, transport channel TrCH 4  is assigned preference level PL 2  and transport channel TrCH 1  is assigned preference level PL 3 . Lastly, transport channels TrCH 3  and TrCH 5  are each assigned preference level PL 4 , as they both have the highest BLER requirement of 10 −4  and the same TTI size of 10 ms. When further tie breakers are necessary, such as with transport channels TrCH 3  and TrCH 5 , the selection of RTrCH from these two transport channels will be on a random basis.  
         [0041]    Returning to step  102  of FIG. 2, a plurality of counters associated with the ON/OFF monitoring of TrCHs and the RTrCH are initialized. (See TABLE 1 for a summary of counters along with a brief description of their related function.) The list of candidate transport channels CAND_LIST includes all transport channels multiplexed on the CCTrCH, with the exception of the RTrCH, both at initialization and throughout the reselection process. Counter COUNT(RTrCH), which monitors the number of occurrences of presence or absence of data on the RTrCH during a monitoring cycle, is reset to zero. Observation period counter OP(RTrCH), which counts how long the RTrCH is being monitored, is also reset to zero. Counter OP(RTrCH) is expressed in terms of number of RTrCH TTIs and is used while monitoring a channel in OFF state. Since process  100  only monitors one channel at any given time (i.e., RTrCH), only one of each of the above initialized parameter counters is necessary to perform monitoring and reselection of RTrCH.  
         [0042]    In step  103 , RTrCH is monitored every TTI, and the ON/OFF state of the RTrCH is recorded as RTrCH_ST. Determination of the ON/OFF state involves detection of data or the absence of data on the monitored channel RTrCH. Further, a designated observation period is used for establishing the density of the data detection for declaring an ON/OFF status with a degree of reasonable certainty. The ON/OFF status is therefore a matter of choice, established by comparing data detection to predetermined selection criteria parameters.  
         [0043]    Next, the timing of the current frame is checked for correspondence to the largest TTI boundary in order to establish whether it is the proper time for RTrCH reselection (step  104 ). The current frame is tracked by counter COUNT(F). The largest TTI boundary is the largest common TTI among the all TrCHs, including the RTrCH. This is preferably obtained by using a modulo operation to determine the TTI boundary of each TrCH. An example for largest TTI boundary determination is shown in FIG. 3C with reference to TrCH 1 - 5  of FIGS. 3A and 3B. As shown in FIG. 3C, the largest TTI boundary occurs at intervals of 40 ms due to the largest TTI size of 40ms for this set of TrCHs.  
         [0044]    In step  104 , if the current frame is not at the largest TTI boundary, then switching to a different RTrCH cannot occur at this point. The process is restarted at step  103  at the next frame. If, however, at step  104 , the current frame corresponds to the largest TTI boundary, then process  100  proceeds to step  105 , where a potential reselection of the RTrCH may occur.  
         [0045]    Step  105  is an ON/OFF status check of RTrCH state counter RTrCH_ST that was recorded in step  103 . If RTrCH_ST=ON, there is no need to reselect RTrCH, so the process returns to step  103  for continuation of monitoring the RTrCH. If RTrCH_ST=OFF at step  105 , the process proceeds to step  106  for a decision on whether there are any other candidates for RTrCH. If the list of candidates CAND_LIST is null, i.e., there are no TrCHs in the candidate list CAND_LIST, the process returns to step  103 , keeping the same RTrCH despite its OFF state. The expectation is that shortly within the next occurring frames, either the current RTrCH will come back on, or another candidate RTrCH will become available. Thus, BLER measurement using an OFF RTrCH will be kept to a minimum. Reestablishing BLER measurement is based on selecting the best possible transport channel as the RTrCH. Returning to step  106 , if there is an available candidate, an RTrCH reselection is made at step  107  to the TrCH with the highest preference level PL.  
                   TABLE 1                       Counter   Function                   COUNT(F)   Provides the count of the current frame       OP(RTrCH)   Observation period counter of the RTrCH used           during monitoring of channel in OFF state       CAND_LIST   Candidate list of TrCHs to be selected from at           RTrCH reselection       RTrCH_ST   ON/OFF state of the RTrCH       COUNT(RTrCH)   Number of occurrences of presence or absence of           data on RTrCH during one monitoring cycle                  
 
         [0046]    Each of the above steps of FIG. 2 will now be explained in further detail with reference to FIGS.  4 - 6 .  
         [0047]    In FIG. 4, a flow diagram of RTrCH monitoring process  200  is shown for when RTrCH is active (i.e., RTrCH_ST=ON) at the start (step  201 ), for determining whether the level of activity has subsided enough to declare an OFF state for RTrCH (i.e., RTrCH_ST=OFF). Process  200  occurs during step  103  of process  100 . Process  200  verifies the current RTrCH state at every TTI for that RTrCH. For example, if TrCH 2  is the RTrCH, its TTI is 20 ms, and therefore, process  200  repeats every 20 ms (i.e., TTI(RTrCH)=20).  
         [0048]    [0048]FIG. 5 illustrates adjustment of the timing of transport channel monitoring received at the MAC. In order to take into account the uplink transfer delay, the RTrCH state monitoring is not performed at the boundary (end-point) of the TTI, but rather after the end-point of the TTI. This accounts for the radio interface delay, data channel delay, and data processing delay. For simplicity, the offset with respect to the TTI end-point can be specified through OAM provisioning. For instance, a total delay is shown in FIG. 5 which is less than 0.5 TTI. In order to counteract the delay, an offset TTI_Tolerance can be specified as 0.5 TTI, where the monitoring point B is 0.5 TTI beyond the TTI boundary point A.  
         [0049]    Returning to FIG. 4, a decision occurs at step  203  to check for whether data is received on the RTrCH. If so, the counter COUNT(RTrCH) is reset to zero at step  204  and the process cycle ends at step  208 . This reset at step  204  occurs since process  200  only tracks consecutive inactive readings of the RTrCH, as the objective is to determine when the RTrCH can be declared OFF. If at step  203  no data is received on the RTrCH, the RTrCH counter COUNT(RTrCH) is incremented by one in step  205 . Following step  205  is the decision (step  206 ) whether the incremented counter COUNT(RTrCH) value has reached the predefined parameter TTI_Inactive. For example, if it is desired to have no more than five (5) sequential inactive TTIs for a RTrCH, parameter TTI_Inactive is predefined to equal five (5). Once counter COUNT(RTrCH) is incremented to a value of five (5) at step  206 , the RTrCH is declared OFF (i.e., RTrCH_ST=OFF), as shown in step  207 . When the RTrCH is set to OFF, counter COUNT(RTrCH) is reset to zero and the monitoring cycle  200  is complete at  208 .  
         [0050]    [0050]FIG. 6 shows a process  300  for monitoring the RTrCH while RTrCH_ST=OFF, to decide when it can be considered reactivated, and thus declared ON (i.e., RTrCH_ST=ON). Process  300  is part of step  103  in process  100  shown in FIG. 2. Because reselection of the RTrCH is to occur when the RTrCH is OFF, it is important to establish whether the RTrCH is indeed OFF prior to reselection. If it is determined in process  300  that the RTrCH is active enough such that RTrCH_ST can be switched from OFF to ON, the need for reselection is eliminated, and the RTrCH monitoring and reselection process  100  repeats at step  103 . Repetition of process  100  occurs at every TTI(RTrCH) plus TTI_Tolerance.  
         [0051]    Returning to FIG. 6, process  300  begins at step  301 . At step  303 , the RTrCH observation period OP(RTrCH) is incremented by one. In step  304 , the RTrCH is monitored for whether data is received. If so, RTrCH counter COUNT(RTrCH) is incremented by one in step  305 . Following step  305 , the RTrCH counter COUNT(RTrCH) is compared to the predetermined reference TTI_Active for number of active TTIs, to determine whether enough activity on the RTrCH has occurred such that the status can be switched from OFF to ON. If counter COUNT(RTrCH) does not equal the required minimum TTI_Active reference, the process ends at step  311 . However, if in step  307  the count has reached the requisite number for activity TTI_Active, the RTrCH state is set to ON (step  309 ), and counters COUNT(RTrCH) and OP(RTrCH) are reset to zero, ending the process at step  311 .  
         [0052]    Returning to step  304 , if data is not received on the RTrCH, step  306  examines whether the observation period OP(RTrCH) has reached parameter T_Activity, indicating that the predetermined number of observation periods has elapsed. Reference parameter T_Activity is useful for setting the desired period of monitored cycles of process  300  to ensure an acceptable density of activity. If the RTrCH has activity that is very spurious, then it is not ready to be considered ON. For example, if single bursts of activity are interspersed with several consecutive TTIs with no data, eventually COUNT(RTrCH) would reach TTI_Active, but with a low percentage of activity over the observation period, (e.g., 5%), the RTrCH would be of little use as a reference channel. Accordingly, with OP(RTrCH) reaching the T_Activity reference in step  306 , the counters for the RTrCH activity T_Activity and the observation period counter OP(RTrCH) are both reset to zero, bringing the monitoring process to an end at step  311 . If the observation period at step  306  is not equal to the value for T_Activity, the counters COUNT(RTrCH) and OP(RTrCH) are not reset so that their counts are maintained for subsequent cycles of process  300 , and the cycle ends at step  311 .  
         [0053]    TABLE 2, below, summarizes the parameters defined by the RNC for analysis against the various counters used for monitoring the ON/OFF state of the RTrCH:  
                           TABLE 2                                   Parameter   Description                           TTI_Inactive   Maximum number of consecutive TTIs with               inactive RTrCH that can acceptably be               endured (to declare ON RTrCH OFF)‘           TTI_Active   Minimum required number of TTIs with               active RTrCH over a period T_Activity               (used to declare an OFF RTrCH ON)           T_Activity   period of TTIs to be monitored for RTrCH               activity prior to declaring an OFF RTrCH ON           TTI(RTrCH)   TTI size for the RTrCH which is the duration               for one monitoring cycle                      
 
         [0054]    Steps  105 - 107  of FIG. 2 are shown in more detail by the flow diagram of FIG. 7. Process  400  shown in FIG. 7 determines whether to reselect the RTrCH (i.e., whether or not to switch over to a better candidate TrCH to act as the RTrCH). Process  400  occurs at every largest TTI boundary, which is at every 40 ms for the set of five transport channels TrCH  1 - 5  shown in FIG. 3C. This boundary is chosen to avoid switching transport channels that may be in midstream. For instance, if the RTrCH reselection were to occur at 20 ms in FIG. 2, TrCH 1  has not yet completed its transmission of data, and it would be undesirable to switch over to TrCH 1  as the next RTrCH at that moment.  
         [0055]    Returning to FIG. 7, process  400  begins at step  401  and proceeds to a decision at step  402  as to whether the RTrCH is ON or OFF. If the RTrCH is ON (i.e., RTrCH_ST=ON), BLER measurement on the RTrCH continues/resumes at step  406 , and switching process  400  is completed at step  407 . If the RTrCH is OFF (i.e., RTrCH_ST=OFF) at step  402 , the process proceeds to step  403  where candidate list CAND_LIST is checked for the absence of candidates. If CAND_LIST is null, the process ends at step  407 . It should be noted, however, that this would occur only if there were one TrCH multiplexed on the CCTrCH, which would indefinitely serve as the RTrCH. In such a case, monitoring process  400  continues to monitor the RTrCH to detect when its state changes to ON. If there are candidates in CAND_LIST at step  403 , process  400  proceeds to step  404  and a new RTrCH is chosen from CAND_LIST in order of highest preference level PL (step  404 ). BLER measurement on the new RTrCH commences at step  405  and the process is complete at step  407 .  
         [0056]    In a second embodiment of the present invention, more than one TrCH is monitored by BLER measurement unit  20  to track ON/OFF states. Unlike the first embodiment where only the RTrCH is monitored, all TrCHs that were once the RTrCH are kept in a hot-candidate list HOTCAND_LIST sorted by preference level PL. During the reselection process, which occurs at every largest TTI boundary, the preferred TrCH for reselection as the RTrCH is the TrCH from among the hot-candidates in HOTCAND_LIST which has the highest preference level PL and is in the ON state. In addition to the hot-candidate transport channels, transport channels in CAND_LIST are available as candidates for reselection.  
         [0057]    [0057]FIG. 8 shows a flow diagram of process  500 , which is the overview of the second embodiment for monitoring and reselection of the RTrCH. Following the start at step  501 , the RTrCH is selected from transport channels TrCHs in step  502  based on assigned preference levels PL, just as described for process  100  shown in FIG. 2, and the process counters are initialized. At step  503 , in addition to monitoring the RTrCH, each hot-candidate transport channel TrCH_i on the hot-candidate list HOTCAND_LIST is also monitored at intervals of TTI plus a nominal tolerance TTI_Tolerance for uplink transfer delay. The ON/OFF state for the RTrCH and the hot-candidates TrCH_i are recorded in TrCH_i_ST. Next, the current frame is compared for correspondence to the largest TTI boundary in step  504 . If the current frame is not at the largest TTI boundary, the process is delayed for one frame (step  506 ), and then resumed at step  503 . Once the current frame corresponds to the largest TTI boundary TTI_Boundary at step  504 , the process continues at step  505  where the next RTrCH is selected from either 1) TrCHs in the hot-candidate list HOTCAND_LIST in an ON state and with the highest preference level PL; or 2) from the candidate list CAND_LIST with the highest preference level PL. Once the RTrCH reselection is completed in step  505  the cycle is repeated beginning with step  503 .  
         [0058]    Each of the above steps of process  500  will now be explained in further detail. During initialization in step  502 , candidate list CAND_LIST is loaded with the identity of each transport channel TrCH multiplexed on the CCTrCH other than the RTrCH. Counters HOTCAND_LIST, OP(RTrCH), COUNT(TrCH_i), OP(TrCH_i) are all initialized to zero. Each hot-candidate transport channel TrCH_i is monitored by its own counter represented by COUNT(TrCH_i). Observation periods of the RTrCH and TrCH_i (i.e., OP(RTrCH) and OP(TrCH_i), respectively), are counters used to monitor how long, in terms of TTI, a given channel is being monitored.  
         [0059]    Step  503  is shown in further detail by the flow diagram of FIG. 9, which illustrates process  900  for RTrCH monitoring using TrCH hot-candidate list HOTCAND_LIST. Process  900  monitors each hot-candidate transport channel TrCH_i in HOTCAND_LIST (currently in OFF state) to determine whether it is possible to declare it to be in the ON state. Process  900  is run for each transport channel TrCH_i in the hot-candidate list at every TTI for the particular hot-candidate TrCH_i. Thus, if there are three hot-candidates TrCH_i, there will be three parallel processes  900  operating to monitor each hot-candidate TrCH_i respectively. Preferably, the monitoring point occurs at the TTI boundary of hot-candidate TrCH_i plus a nominal TTI_Tolerance.  
         [0060]    Process  900  starts at step  901  and proceeds to step  903  where it is determined whether there are any hot-candidates TrCH_i in the hot-candidate list HOTCAND_LIST. If the hot-candidate list HOTCAND_LIST is empty, process  900  ends at step  912 . If, however, there are hot-candidates TrCH_i present in HOTCAND_LIST, observation period OP(TrCH_i) is incremented (step  904 ).  
         [0061]    The next decision (step  905 ) is whether data has been received on the monitored hot-candidate TrCH_i. If data has been received, counter COUNT(TrCH_i) is incremented to reflect the data reception at step  906 . Next, COUNT(TrCH_i) is checked to determine whether the count has reached the predetermined reference value TTI_Active (i.e., to determine whether enough activity on the RTrCH has occurred such that the status TrCH_i_ST can be switched from OFF to ON). If counter COUNT(TrCH_i) does not equal the required minimum TTI_Active reference value, process  900  ends at step  912 . However, if in step  907  counter COUNT(TrCH_i) has reached the requisite number for activity, the hot-candidate state TrCH_i_ST is turned ON (step  908 ), and the hot-candidate counters COUNT(TrCH_i) and OP(TrCH_i) are reset to zero (step  911 ), before ending the process at step  912 .  
         [0062]    Returning to decision step  905 , if data is not received on the hot-candidate TrCH_i, a decision at step  910  commences where the observation period for the hot-candidate OP(TrCH_i) is checked against parameter T_Activity, yielding whether the predetermined acceptable number of observation periods has elapsed. If so, the counter COUNT(TrCH_i) for hot-candidate TrCH_i and the observation period counter OP(TrCH_i) are both reset to zero (step  911 ), and process  900  ends at step  912 . If the observation period OP(TrCH_i) is not equal to the value for T_Activity, the counters maintain their counts for subsequent cycles of process  900 , and process  900  ends at step  912 .  
         [0063]    [0063]FIG. 10 shows a flow diagram of process  1000 , which shows steps  504  and  506  in further detail. Process  1000  involves the decision making process for whether to reselect the RTrCH from the hot-candidate list HOTCAND_LIST, based on the appropriateness of the current frame timing, and if a suitable replacement transport channel has become sufficiently active. Process  1000  occurs at every largest TTI boundary, which is at every 40 ms for the set of five (5) transport channels TrCH 1 - 5  shown in FIG. 3C. As aforementioned, this boundary is chosen to avoid switching TrCHs that may be in midstream. Process  1000  begins at step  1001  and proceeds to a decision step  1002  as to whether there is at least one hot-candidate TrCH_i in the ON state in list HOTCAND_LIST. If so, BLER measurement on the current RTrCH is ceased as it now becomes the former RTrCH, and now the former RTrCH is added to HOTCAND_LIST. Next in step  1004 , the TrCH with the highest preference level PL from HOTCAND_LIST is reselected as the new RTrCH. Next in step  1005 , any TrCH_i in the HOTCAND_LIST with PL less than equal to either the new or the prior RTrCH preference level is removed. The removed TrCHs are added to CAND_LIST. Thus, HOTCAND_LIST is maintained with candidates having greater preference level PL than the current RTrCH. Reselection of RTrCH from hot-candidates TrCH_i will occur as soon as a hot-candidate TrCH_i goes ON, regardless if the RTrCH is ON or OFF. Meanwhile, monitoring is limited to hot-candidates TrCH_i, and resources are conserved by eliminating TrCHs from monitoring that are moved to the candidate list CAND_LIST. These CAND_LIST candidates will be eligible for monitoring and reselection if transferred back to HOTCAND_LIST, as described below. BLER measurement resumes in step  1006  using the new RTrCH, and process  1000  is complete at step  1007 .  
         [0064]    Returning to the decision step  1002 , if there are no hot-candidates TrCH_i in the ON state in HOTCAND_LIST, step  1008  checks the ON/OFF state RTrCH_ST for the current RTrCH. If the state of the current RTrCH is ON, BLER measurement is continued using the current RTrCH (step  1009 ), and process  1000  ends at step  1007 . If the state of the current RTrCH is OFF at step  1008 , step  1010  commences to check whether CAND_LIST is empty, and if so, process  1000  ends at step  1007 . If CAND_LIST is not null, the new RTrCH is reselected from CAND_LIST taking the TrCH with the highest preference level PL, and the current RTrCH becomes the former RTrCH and is added to HOTCAND_LIST (step  1011 ). Any TrCH in CAND_LIST with PL equal to the new RTrCH PL is added to HOTCAND_LIST (step  1012 ). Hot-candidate counter COUNT(TrCH_i) is reset to zero for each TrCH added to HOTCAND_LIST. Thus, the list of hot-candidates HOTCAND_LIST is updated to include the best candidates for subsequent reselection. Next, BLER measurement is resumed at step  1006  using the new RTrCH, and process  1000  ends at step  1007 .  
         [0065]    In an alternative of the first embodiment of the invention, reselection of the RTrCH is the same as the first embodiment process  100  using candidates from CAND_LIST, but the monitoring of the RTrCH is not in a periodic fashion on a TTI basis as in step  103  of FIG. 2. Instead, monitoring of the RTrCH occurs aperiodically at detection of data on any of the transport channels. Once data is detected, it can be established that at that moment, the current frame is at a TTI boundary. The current frame is tracked by using the encoded CFN contained in the received frame header.  
         [0066]    [0066]FIG. 11 shows a flow diagram of a process  1100 , which performs RTrCH monitoring on a data reception basis. Process  1100  is a modification of process  200  shown in FIG. 4, where monitoring of an active RTrCH is performed to determine when the RTrCH activity subsides enough that it can be declared to be in an OFF state. Process  1100  starts at step  1101 , and is repeated at every data reception on any transport channel to accommodate current frame tracking performed in step  1103 . At step  1103 , the number of elapsed TTIs between data detections, represented by TTI_Difference, is calculated, using the following relationship:  
             TTI_Difference   =     FLOOR   [             (     CFN_Current   +   256   -                     CFN_Previous        (   RTrCH   )       )        mod                 256             TTI        (   RTrCH   )         ]             Equation                 1                               
 
         [0067]    CFN_Current represents the current connection frame number CFN as identified in the received data frame received on any of the transport channels multiplexed on the CCTrCH. Value CFN_Previous(RTrCH) represents the CFN of the frame in which the last data detection occurred on the RTrCH. The FLOOR function yields the integer value rounded down from the ratio in Equation 1. The preferred frame structure is defined by a repeating set of 256 frames, as evident by the mod256 operation in Equation 1, but other frame parameter types may be readily used within the scope of the present invention, whereby Equation 1 can be modified accordingly.  
         [0068]    Following calculation step  1103  is the decision whether the number of inactive TTIs from value TTI_Difference has reached or exceeded the predetermined threshold TTI_Inactive (step  1104 ). For example, if it is desired to have no more than five (5) sequential inactive TTIs for a RTrCH, parameter TTI_Inactive is predefined to equal five (5). If value TTI_Difference meets or exceeds five (5), the RTrCH is declared OFF (RTrCH_ST=OFF), as shown in step  1105 .  
         [0069]    At decision step  1106 , it is determined whether the transport channel on which data was received is the RTrCH. If so, the counter CFN_Previous (RTrCH) is reset to zero at step  1107  and process  1100  ends at step  1108 . This reset occurs since process  1100  only tracks inactive readings of the RTrCH, as the objective is to determine when the RTrCH can be declared OFF. If, however, no data was received on the RTrCH at step  1106 , the RTrCH counter CFN_Previous(RTrCH) is not incremented in step  1107 , and process  1100  ends at step  1108 . With no data received on the RTrCH at the current frame, at least another frame has transpired without data reception, which will be accounted for at the next calculation of TTI_Difference when process  1100  is repeated at any data reception.  
         [0070]    Turning to FIG. 12, a flow diagram for a process  1200  that operates under an alternative to the first embodiment of the invention, where monitoring of the RTrCH is performed while it is OFF, to decide when it can be considered reactivated, and thus declared ON (i.e., RTrCH_ST=ON). Process  1200  is an alteration of channel monitoring process  300  of FIG. 6, where the alteration is that monitoring is triggered by RTrCH data reception. Process  1200  begins at step  1201  and the process is repeated at every data reception on the RTrCH. At step  1203 , RTrCH counter COUNT(RTrCH) is incremented by one (step  1203 ) because data was detected on the RTrCH at commencement of process  1200 . Next, TTI_Difference is calculated in step  1204  using Equation 1 for establishing the number of TTIs elapsed between data detections on the RTrCH. Observation period OP(RTrCH) is then incremented by value TTI_Difference (step  1205 ) which captures possibly several TTIs. In contrast to process  300 , in which OP(RTrCH) is incremented every TTI regardless of data detection, process  1200  has the advantage of reduced processing as monitoring is suspended during the TTIs with no data reception.  
         [0071]    Decision step  1206  examines whether the observation period OP(RTrCH) has reached parameter T_Activity indicating that the predetermined acceptable number of observation periods has elapsed. If so, RTrCH counters COUNT(RTrCH) and OP(RTrCH) are reset to zero and counter CFN_Previous(RTrCH) is reset to CFN_Current. These reset counters reflect that too much time has elapsed since the last data detection, preventing a valid channel state change from OFF to ON, and a new observation period commences.  
         [0072]    Returning to step  1206 , a negative result means that there is still an opportunity for the channel state to change, and process  1200  proceeds to step  1209 . The RTrCH counter COUNT(RTrCH) is compared to the predetermined reference TTI_Active, to determine whether enough activity on the RTrCH has occurred such that the status can be switched from OFF to ON. If counter COUNT(RTrCH) is less than the required minimum TTI_Active reference, counter CFN_Previous(RTrCH) is reset to CFN_Current (step  1208 ) and process  1200  ends at step  1212 . However, if in step  1209  the counter COUNT(RTrCH) has reached the requisite number for activity TTI_Active, the RTrCH state is set to ON (step  1210 ), and counters COUNT(RTrCH) and OP(RTrCH) are reset to zero (step  1207 ) before resetting CFN_Previous(RTrCH) at step  1208 .  
         [0073]    An alternative to the second embodiment of the present invention involves monitoring of hot-candidates, but the monitoring occurs at every data reception on any hot-candidate TrCH_i rather than at every TTI. FIG. 13 shows a flow diagram of process  1300 , which is similar to process  900  of FIG. 9. Once process  1300  commences at step  1300 , hot-candidate counter COUNT(TrCH_i) is incremented at step  1303  to reflect the reception of data. Next, value TTI_Difference is calculated according to Equation 2 (step  1304 ):  
             TTI_Difference   =     FLOOR   [             (     CFN_Current   +   256   -                     CFN_Previous        (   TrCH_i   )       )        mod                 256             TTI        (   TrCH_i   )         ]             Equation                 2                               
 
         [0074]    CFN_Current represents the current connection frame number CFN as identified in the received data frame received on any of the transport channels multiplexed on the CCTrCH. Value CFN_Previous(TrCH_i) represents the CFN of the frame in which the last data detection occurred on the monitored hot-candidate TrCH_i. Hot-candidate observation period OP(TrCH_i) is incremented by the value TTI_Difference (step  1305 ). The first decision step  1306  checks whether observation period OP(TrCH_i) has reached the predetermined parameter T_Activity, yielding whether the predetermined acceptable number of observation periods has elapsed. If true, the counter COUNT(TrCH_i) for hot-candidate TrCH_i and the observation period counter OP(TrCH_i) are both reset to zero, (step  1307 ) and frame counter CFN_Previous(TrCH_i) is reset to value CFN_Current (step  1308 ), bringing process  1300  to an end at step  1312 . If at step  1306  the observation period OP(TrCH_i) is not equal to the value for T_Activity, hot-candidate counter COUNT(TrCH_i) is checked for whether the count has reached the predetermined reference value TTI_Active. This decision at step  1309  determines whether enough activity on the hot-candidate transport channel has occurred such that the status can be switched from OFF to ON. If counter COUNT(TrCH_i) does not equal the required minimum TTI_Active reference value, the frame counter is reset at step  1308  and process  1300  ends at step  1312 . However, if in step  1309  the count has reached the requisite number for activity, the hot-candidate state TrCH_i_ST is turned ON (step  1310 ), and hot-candidate counters COUNT(TrCH_i) and OP(TrCH_i) are reset to zero (step  1307 ), before resetting CFN_Previous(TrCH_i) at step  1308 .  
         [0075]    Implementation of the preferred methods will now follow in reference to FIGS.  1 A- 1 C. FIG. 1A shows a block diagram for a 3GPP UTRAN system  10 , comprising a radio network controller (RNC)  11  communicating with WTRU  16  through base station  14 . Since the general functionality of an RNC, base station, and WTRU are known by those skilled in the art, these components will only be described hereinafter to the extent that such functionality is relevant to the present invention. RNC  11  comprises many components that interact on several communication layers, but those of interest for the purpose of the present invention are shown in FIG. 1A. They are a radio resource control (RRC) layer  12 , medium access control (MAC) layer  13 , and frame protocol (FP) entity  25 . RRC  12  is responsible for performing outer loop power control of communication system  10 , which produces target SIR adjustments. MAC  13  performs the BLER measurement, which is a necessary input for outer loop power control. Alternatively, frame protocol (FP) entity  25  performs the BLER measurement.  
         [0076]    RRC  12  is linked to MAC  13  via communication path  22 , which is linked in turn to FP  25  via communication path  24 . MAC control path  23  is used to transmit the BLER measurement from MAC  13  to RRC  12 , from which the target SIR adjustment is generated. Data channel paths  20  and  21  transmit the received communication data from WTRU  16  to MAC  13  and FP entity  25 , respectively, via base station  14 .  
         [0077]    WTRU  16  comprises RRC layer  19 , MAC layer  17 , and Li layer  18 . RRC  19  and MAC  17  perform functions similar to RRC  12  and MAC  13  associated with RNC  11 . L 1  layer  18  is a physical (PHY) layer to which transport channels are mapped on the CCTrCH for UL transmission  26 . MAC control path  27  is used to transmit the BLER measurement from MAC  17  to RRC  19  when BLER measurement is performed by MAC  17 . Alternatively, Li layer  18  performs BLER measurement of WTRU  16  and the BLER measurement is transmitted across L 1  layer control path  28  to RRC  19 .  
         [0078]    Base station  14  communicates through data channels  20 ,  21  with RNC MAC layer  13  and FP entity  25 . The SIR target adjustment is achieved through signaling over the air interface on the DL signal  15  between WTRU  16  and base station  14 . In an alternative embodiment, base station  14  includes a MAC layer, which may perform the BLER measurement in lieu of MAC layer  13  of RNC  11 .  
         [0079]    [0079]FIG. 1B shows a block diagram of WTRU  16 , comprising antenna  51 , isolator  52 , modulator  53 , amplifier  54 , data generator  55 , transmit power control unit  56 , BLER measurement unit  60 , channel estimation unit  57 , and demodulator  58 . BLER measurement unit  60  includes composite channel signal processing circuitry that comprises error measurement circuitry, monitoring circuitry and reference channel selection circuitry. A description of the BLER measurement unit  60  in the context of the remainder of WTRU  16  components now follows.  
         [0080]    On the receiver side of WTRU  16 , antenna  51  receives various RF signals. Alternatively, antenna  51  may comprise an antenna array. The received signals are passed through isolator  52  to demodulator  58  to produce a baseband signal. The baseband signal is processed by channel estimation device  57 , which commonly uses a training sequence component in the baseband signal to provide channel information, such as channel impulse responses. Channel estimation device  57  is capable of separating the RTrCH from all other channels in the baseband. BLER measurement unit  60  determines the BLER with respect to the current RTrCH. The BLER measurement is received by the transmit power control unit  56 , which converts the BLER information into a control signal for power adjustment in amplifier  54 . Amplifier  54  receives the data signal for transmission from data generator  55 . On the transmission side, the data signal is amplified according to the adjusted power control signal from transmit power control unit  56 . The amplified signal is modulated at modulator  53 , passed through isolator  52 , and transmitted over antenna  51 .  
         [0081]    [0081]FIG. 1C shows BLER measurement unit  60  in further detail. Preferably, BLER measurement unit  60  performs BLER measurements within the MAC layer  13  for RNC  11  and MAC layer  17  of WTRU  16 . BLER measurement unit  60  comprises memory unit  62 , register  64 , preference level unit  30 , TTI_Boundary unit  40 , and timer  45 . BLER measurement unit  60  is responsible for ascertaining whether a TrCH or the RTrCH is ON or OFF based on a cumulative count of presence or absence of data in the form of transport blocks (TBs) over time period in terms of TTIs, according to the preferred method embodiments.  
         [0082]    Preference level unit  30  assigns a preference level PL to each TrCH for selection as the RTrCH. Register  64  maintains the plurality of counters used in the ON/OFF state monitoring of TrCHs and the RTrCH according to the present invention, comprising frame counter COUNT(F), RTrCH observation period OP(RTrCH), candidate list CAND_LIST, hot-candidate list HOTCAND_LIST, the RTrCH ON/OFF state RTrCH_ST, RTrCH counter COUNT(RTrCH), hot-candidate observation period OP(TrCH_i), hot-candidate counter COUNT(TrCH_i), and hot-candidate ON/OF state TrCH_i_ST. Memory unit  62  stores predetermined reference settings utilized by BLER measurement unit  60  for the decision process of whether to declare a TrCH or the RTrCH in the ON or OFF state, as presented above in TABLE 2.  
         [0083]    With respect to the RTrCH monitoring point, timer  45  increments frame counter COUNT(F) every 10 ms. TTI_Boundary unit  40  works in conjunction with timer  45  to confirm whether the current frame is at a TTI boundary, and also determines the largest common TTI boundary among the candidate TrCHs to allow optimum synchronization for the switching of the RTrCHs. TTI_Boundary unit  40  performs a ratio calculation to determine TTI_Difference based on the value from counter COUNT(F) and the TTI size of the monitored transport channel. If the ratio yields an integer value, it is established that the current frame is at a TTI boundary. For example, if the TTI size is 20 ms, and the COUNT(F) value is 5, the yielded result is 50/20=2.5, which is not at a TTI boundary. Alternatively, spontaneous detection of data could commence tracking of the RTrCH state, rather than the periodic monitoring points shown in regular intervals in FIG. 5. The system CFN identified in each frame header can be used to track the number of TTIs that elapsed between occurrences of data detection on the RTrCH. This alternative embodiment would require less processing resources and eliminate the need for using timer  45 . Reference channel selection circuitry within BLER measurement unit 60 is configured to reselect RTrCH responsive to monitoring of the ON and OFF states of RTrCH and hot-candidates TrCH_i. Once reselection is made, BLER measurement commences on the new reference channel RTrCH.

Technology Classification (CPC): 7