Abstract:
A method and apparatus for allocating and using a finite resource to transmit wireless information signals to a plurality of subscriber units is disclosed. Individual subscriber units transmit data rate requests to serving base stations. The data rate requests and weight values associated with each subscriber unit are compared in order to select a subscriber unit as the recipient of data transmitted through the finite resource at any given time. To maximize throughput without starving any single subscriber unit, the method includes calculation and comparison of a desirability metric in choosing a subscriber unit from among a subset of the plurality of subscriber units having comparable weight values.

Description:
CROSS REFERENCE 
     This application is a continuation application of application Ser. No. 09/479,735, filed Jan. 7, 2000, now U.S. Pat. No. 6,393,012, issued May 21, 2002, entitled “SYSTEM FOR ALLOCATING RESOURCES IN A COMMUNICATION SYSTEM,” currently assigned to the assignee of the present application, and which is a continuation-in-part of application Ser. No. 09/229,432, filed Jan. 13, 1999, now U.S. Pat. No. 6,229,795, entitled “SYSTEM FOR ALLOCATING RESOURCES IN A COMMUNICATION SYSTEM,” issued May 8, 2001, also assigned to the assignee of the present application and which is expressly incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present application relates to communication systems. Particularly, these embodiments are directed to allocating communication resources among the plurality of subscribers to a communication system. 
     2. Related Art 
     Several solutions have been presented to address the problem of allocating limited communication resources provided by a single node in a communication system among a plurality of subscribers. It is an objective of such systems to provide sufficient resources at the nodes to satisfy the requirements of all subscribers while minimizing costs. Accordingly, such systems are typically designed with the objective of efficient allocation of resources among the various subscribers. 
     Various systems have implemented a frequency division multiple access (FDMA) scheme, which allocates resources to each of the subscribers concurrently. A communication node in such systems typically has a limited bandwidth for either transmitting information to or receiving information from each subscriber in the network at any point in time. This scheme typically involves allocating distinct portions of the total bandwidth to the individual subscribers. While such a scheme may be effective for systems in which subscribers require uninterrupted communication with the communication node, better utilization of the total bandwidth may be achieved when such constant, uninterrupted communication is not required. 
     Other schemes for allocating communication resources of a single communication node among a plurality of subscribers includes time division multiple access (TDMA) schemes. These TDMA schemes are particularly effective in allocating the limited bandwidth resources of a single communication node among a plurality of subscribers which do not require constant, uninterrupted communication with the single communication node. TDMA schemes typically dedicate the entire bandwidth of the single communication node to each of the subscribers at designated time intervals. In a wireless communication system which employs a code division multiple access (CDMA) scheme, this may be accomplished by assigning to each of the subscriber units all code channels at the designated time intervals on a time multiplexed basis. The communication node implements the unique carrier frequency or channel code associated with the subscriber to enable exclusive communication with the subscriber. TDMA schemes may also be implemented in land line systems using physical contact relay switching or packet switching. 
     TDMA systems typically allocate equal time intervals to each subscriber in a round robin fashion. This may result in an under utilization of certain time intervals by certain subscribers. Similarly, other subscribers may have communication resource requirements, which exceed the allocated time interval, leaving these subscribers under served. The system operator then has the choice of either incurring the cost of increasing the bandwidth of the node to ensure that none of the subscribers are under served, or allowing the under served subscribers to continue to be under served. 
     Accordingly, there is a need to provide a system and method of allocating communication resources among subscribers to a communication network efficiently and fairly according to a network policy of allocating the communication resources among the subscribers. 
     SUMMARY 
     An object of an embodiment of the present invention is to provide a system and method for allocating a finite resource of a communication system among a plurality of subscribers. 
     Another object of an embodiment of the present invention is to provide a system and method for allocating data transmission resources among a plurality of subscribers which have varying capacities to receive data. 
     It is another object of an embodiment of the present invention to provide a system and method for optimally allocating data transmission resources among a plurality of subscribers subject to a fairness criteria according to a network policy. 
     It is another object of an embodiment of the present invention to provide a system and method for allocating data transmission resources of a base station among a plurality of remote stations in a wireless communication network. 
     It is yet another object of an embodiment of the present invention to provide a system and method for enhancing the efficiency of transmitting data to a plurality of subscribers in a variable rate data transmission network by allocating transmission resources to each individual subscriber based upon the rate at which the subscriber can receive transmitted data. 
     Briefly, an embodiment of the present invention is directed to a resource scheduler in a communication system which includes a common node and a plurality of customer nodes associated with the common node. The common node, at any particular service interval, is capable of providing a finite resource to be seized by one or more engaging customer nodes to the exclusion of any remaining customer nodes. The resource scheduler includes logic for maintaining a weight or score associated with each of the customer nodes, logic for selecting one or more of the remaining customer nodes to seize the finite resource in a subsequent service interval based upon a comparison of the weight associated with each of the selected customer nodes and the respective weights associated with the other remaining customer nodes, and logic for changing the weights associated with the customer nodes to cause an optimal allocation of the finite resource subject to a fairness criteria. 
     The resource scheduler may maintain the weights associated with each customer node based upon the instantaneous rate at which the customer node can receive data from the common node. The resource scheduler may then favor transmission to the customer nodes having the higher rates of receiving data. By maintaining a weight associated with each of the customer nodes, and selecting individual customer nodes to seize the common node, the scheduler can optimally allocate resources to the customer nodes subject to a fairness criteria. 
     In the embodiment where the common node provides data transmission resources to the customer nodes, for example, the scheduler may apply weights to the individual customer nodes so as to favor those customer nodes capable of receiving data at higher rates. Such a weighting tends to enhance the overall data throughput of the common node. In another embodiment, the weights are applied in a manner so that the scheduler also complies with the fairness criteria. 
     In one aspect of the invention, a method of allocating a finite resource in a communication system is provided, the communication system including a common node and a plurality of customer nodes associated with the common node, each of the customer nodes having a requested data rate, wherein during any particular service interval the common node allocates the finite resource to one of the customer nodes to the exclusion of any remaining customer nodes, the method comprising the steps of: maintaining a set of weights having one weight corresponding to each of the customer nodes; identifying a minimum weight M from said set of weights; identifying a subset of said customer nodes having weights less than or equal to the sum of M and an offset K; determining a desirability metric value for each customer node in said subset; selecting, from said subset, a most desired customer node having the greatest desirability metric value; exchanging data between the common node and said most desired customer node through the finite resource and at the data rate associated with said most desired customer node; and changing said set of weights based on said most desired customer node and the data rate associated with said most desired customer node. 
     In another aspect of the invention, a wireless transmitter apparatus is provided, comprising: at least one antenna for receiving requested data rate signals from each of a plurality of customer nodes and for directing information signals to said plurality of customer nodes; a channel element for modulating a data signal for transmission through said at least one antenna to each of said plurality of customer nodes; and a channel scheduler for maintaining a set of weights corresponding to each of the customer nodes, identifying a minimum weight M from said set of weights, identifying a subset of said customer nodes having weights less than or equal to the sum of M and an offset K, determining a desirability metric value for each customer node in the subset, selecting from the subset a most desired customer node having the greatest desirability metric value, providing information corresponding to the most desired customer node to said channel element, and updating the set of weights. 
     While the embodiments disclosed herein are directed to methods and systems for allocating data transmission resources to subscribers through a forward channel in a data service network, the underlying principles have even broader applications to the allocation of resources among elements in a communication system generally. The disclosed embodiments are therefore intended to be exemplary and not limiting the scope of the claims. For example, principles described herein are applicable to communication networks in which the customer nodes compete for the ability to transmit data to a common node through a limited reverse transmission channel. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a communication network according to an embodiment of the present invention. 
         FIG. 2   a  shows a block diagram of a base station controller and base station apparatus configured in accordance with an embodiment of the present invention. 
         FIG. 2   b  shows a block diagram of a remote station apparatus configured in accordance with an embodiment of the present invention. 
         FIG. 3  shows a flow diagram illustrating the execution of a scheduling algorithm in an embodiment of the channel scheduler shown in FIG.  2 . 
         FIG. 4  shows a diagram illustrating the timing of the execution of an embodiment of the scheduling algorithm shown in FIG.  3 . 
         FIG. 5  shows a flow diagram illustrating an embodiment of the process for updating the weights for a selected queue in the embodiment identified in FIG.  3 . 
         FIGS. 6   a  through  6   c  show a flow diagram illustrating a first embodiment of the process for selecting a queue to receive data transmission in a service interval identified in FIG.  3 . 
         FIGS. 7   a  through  7   d  show a flow diagram illustrating a second embodiment of the process for selecting a queue to receive data transmission in a service interval identified in FIG.  3 . 
         FIGS. 8   a  and  8   b  show a flow diagram illustrating a third embodiment of the process for selecting a queue to receive data transmission in a service interval identified in FIG.  3 . 
         FIG. 9  shows a high level flow diagram illustrating an alternate process for updating the weights for a selected queue in the embodiment identified in FIG.  3 . 
         FIG. 10  shows a detailed flow diagram of an embodiment of the process shown in FIG.  9 . 
         FIGS. 11   a - 11   b  are block diagrams of the exemplary forward link architecture of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are directed to a system and apparatus for allocating resources among a plurality of subscribers to a communication network which are serviced by a single communication node. At individual discrete transmission intervals, or “service intervals,” individual subscribers seize a finite resource of the communication node to the exclusion of all other subscribers. The individual subscribers are selected to seize the finite resource based upon a weight or score associated with the individual subscribers. Changes in a weight associated with an individual subscriber are preferably based upon an instantaneous rate at which the individual subscriber is capable of consuming the finite resource. 
     Referring to the figures,  FIG. 1  represents an exemplary variable rate communication system. One such system is described in the U.S. patent application Ser. No. 08/963,386, now U.S. Pat. No. 6,574,211, issued Jun. 3, 2003, entitled “METHOD AND APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION,” assigned to Qualcomm, Inc. and incorporated herein by reference. The variable rate communication system comprises multiple cells  2   a - 2   g . Each cell  2  is serviced by a corresponding base station  4 . Various remote stations  6  are dispersed throughout the communication system. In the exemplary embodiment, each of remote stations  6  communicates with at most one base station  4  on a forward link at any data transmission interval. For example, base station  4   a  transmits data exclusively to remote station  6   a , base station  4   b  transmits data exclusively to remote station  6   b , and base station  4   c  transmits data exclusively to remote station  6   c  on the forward link at time slot n. As shown by  FIG. 1 , each base station  4  preferably transmits data to one remote station  6  at any given moment. In other embodiments, the base station  4  may communicate with more than one remote station  6  at a particular data transmission interval to the exclusion of all other remote stations  6  associated with the base station  4 . In addition, the data rate is variable and is dependent on the carrier-to-interference ratio (C/I) as measured by the receiving remote station  6  and the required energy-per-bit-to-noise ratio (E b /N 0 ). The reverse link from remote stations  6  to base stations  4  is not shown in  FIG. 1  for simplicity. According to an embodiment, the remote stations  6  are mobile units with wireless transceivers operated by wireless data service subscribers. 
     A block diagram illustrating the basic subsystems of an exemplary variable rate communication system is shown in  FIGS. 2   a - 2   b . Base station controller  10  interfaces with packet network interface  24 , public switched telephone network (PSTN)  30 , and all base stations  4  in the communication system (only one base station  4  is shown in  FIG. 2  for simplicity). Base station controller  10  coordinates the communication between remote stations  6  in the communication system and other users connected to packet network interface  24  and PSTN  30 . PSTN  30  interfaces with users through a standard telephone network (not shown in FIG.  2 ). 
     Base station controller  10  contains many selector elements  14 , although only one is shown in  FIG. 2   a  for simplicity. Each selector element  14  is assigned to control communication between one or more base stations  4  and one remote station  6 . If selector element  14  has not been assigned to remote station  6 , call control processor  16  is informed of the need to page remote station  6 . Call control processor  16  then directs base station  4  to page remote station  6 . 
     Data source  20  contains a quantity of data which is to be transmitted to the remote station  6 . Data source  20  provides the data to packet network interface  24 . Packet network interface  24  receives the data and routes the data to the selector element  14 . Selector element  14  transmits the data to each base station  4  in communication with remote station  6 . In the exemplary embodiment, each base station  4  maintains a data queue  40  which stores the data to be transmitted to the remote station  6 . 
     The data is transmitted in data packets from data queue  40  to channel element  42 . In the exemplary embodiment, on the forward link, a “data packet” refers to a quantity of data which is the maximum of 1024 bits and a quantity of data to be transmitted to a destination remote station  6  within a “time slot” (such as≈1.667 msec). For each data packet, channel element  42  inserts the necessary control fields. In the exemplary embodiment, channel element  42  CRC encodes the data packet and control fields and inserts a set of code tail bits. The data packet, control fields, CRC parity bits, and code tail bits comprise a formatted packet. In the exemplary embodiment, channel element  42  then encodes the formatted packet and interleaves (or reorders) the symbols within the encoded packet. In the exemplary embodiment, the interleaved packet is covered with a Walsh code, and spread with the short PNI and PNQ codes. The spread data is provided to RF unit  44  which quadrature modulates, filters, and amplifies the signal. The forward link signal is transmitted over the air through antenna  46  on forward link  50 . 
     In  FIG. 2   b  at remote station  6 , the forward link signal is received by antenna  60  and routed to a receiver within front end  62 . The receiver filters, amplifies, quadrature demodulates, and quantizes the signal. The digitized signal is provided to demodulator (DEMOD)  64  where it is despread with the short PNI and PNQ codes and decovered with the Walsh cover. The demodulated data is provided to decoder  66  which performs the inverse of the signal processing functions done at base station  4 , specifically the de-interleaving, decoding, and CRC check functions. The decoded data is provided to data sink  68 . 
     The hardware, as pointed out above, supports variable rate transmissions of data, messaging, voice, video, and other communications over the forward link. The rate of data transmitted from the data queue  40  varies to accommodate changes in signal strength and the noise environment at the remote station  6 . Each of the remote stations  6  preferably transmits a data rate control (DRC) signal to an associated base station  4  at each time slot. The DRC signal provides information to the base station  4  which includes the identity of the remote station  6  and the rate at which the remote station  6  is to receive data from its associated data queue. Accordingly, circuitry at the remote station  6  measures the signal strength and estimates the noise environment at the remote station  6  to determine the rate information to be transmitted in the DRC signal. 
     The DRC signal transmitted by each remote station  6  travels through reverse link channel  52  and is received at base station  4  through antenna  46  and RF unit  44 . In the exemplary embodiment, the DRC information is demodulated in channel element  42  and provided to a channel scheduler  12   a  located in the base station controller  10  or to a channel scheduler  12   b  located in the base station  4 . In a first exemplary embodiment, the channel scheduler  12   b  is located in the base station  4 . In an alternate embodiment, the channel scheduler  12   a  is located in the base station controller  10 , and connects to all selector elements  14  within the base station controller  10 . 
     In the first-mentioned exemplary embodiment, channel scheduler  12   b  receives information from data queue  40  indicating the amount of data queued up for each remote station, also called queue size. Channel scheduler  12   b  then performs scheduling based on DRC information and queue size for each remote station serviced by base station  4 . If queue size is required for a scheduling algorithm used in the alternate embodiment, channel scheduler  12   a  may receive queue size information from selector element  14 . 
     Embodiments of the present invention are applicable to other hardware architectures which can support variable rate transmissions. The present invention can be readily extended to cover variable rate transmissions on the reverse link. For example, instead of determining the rate of receiving data at the base station  4  based upon a DRC signal from remote stations  6 , the base station  4  measures the strength of the signal received from the remote stations  6  and estimates the noise environment to determine a rate of receiving data from the remote station  6 . The base station  4  then transmits to each associated remote station  6  the rate at which data is to be transmitted in the reverse link from the remote station  6 . The base station  4  may then schedule transmissions on the reverse link based upon the different data rates on the reverse link in a manner similar to that described herein for the forward link. 
     Also, a base station  4  of the embodiment discussed above transmits to a selected one, or selected ones, of the remote stations  6  to the exclusion of the remaining remote stations associated with the base station  4  using a code division multiple access (CDMA) scheme. At any particular time, the base station  4  transmits to the selected one, or selected ones, of the remote station  6  by using a code which is assigned to the receiving base station(s)  4 . However, the present invention is also applicable to other systems employing different time division multiple access (TDMA) methods for providing data to select base station(s)  4 , to the exclusion of the other base stations  4 , for allocating transmission resources optimally. 
     The channel scheduler  12  schedules the variable rate transmissions on the forward link. The channel scheduler  12  receives the queue size, which is indicative of the amount of data to transmit to remote station  6 , and messages from remote stations  6 . The channel scheduler  12  preferably schedules data transmissions to achieve the system goal of maximum data throughput while conforming to a fairness constraint. 
     As shown in  FIG. 1 , remote stations  6  are dispersed throughout the communication system and can be in communication with zero or one base station  4  on the forward link. In the exemplary embodiment, channel scheduler  12  coordinates the forward link data transmissions over the entire communication system. A scheduling method and apparatus for high speed data transmission are described in detail in U.S. patent application Ser. No. 08/798,951, now U.S. Pat. No. 6,335,922, issued on Jan. 1, 2002, entitled “METHOD AND APPARATUS FOR FORWARD LINK RATE SCHEDULING,” assigned to the assignee of the present invention and incorporated by reference herein. 
     According to an embodiment, the channel scheduler  12  is implemented in a computer system which includes a processor, random access memory (RAM) and a program memory for storing instructions to be executed by the processor (not shown). The processor, RAM and program memory may be dedicated to the functions of the channel scheduler  12 . In other embodiments, the processor, RAM and program memory may be part of a shared computing resource for performing additional functions at the base station controller  10 . 
       FIG. 3  shows an embodiment of a scheduling algorithm which controls the channel scheduler  12  to schedule transmissions from the base station  4  to the remote stations  6 . As discussed above, a data queue  40  is associated with each remote station  6 . The channel scheduler  12  associates each of the data queues  40  with a “weight” which is evaluated at a step  110  for selecting the particular remote station  6  associated with the base station  4  to receive data in a subsequent service interval. The channel scheduler  12  selects individual remote stations  6  to receive a data transmission in discrete service intervals. At step  102 , the channel scheduler initializes the weight for each queue associated with the base station  4 . 
     A channel scheduler  12  cycles through steps  104  through  112  at transmission intervals or service intervals. At step  104 , the channel scheduler  12  determines whether there are any additional queues to be added due to the association of an additional remote station  6  with the base station  4  detected in the previous service interval. The channel scheduler  12  also initializes the weights associated with the new queues at step  104 . As discussed above, the base station  4  receives the DRC signal from each remote station  6  associated therewith at regular intervals such as time slots. 
     This DRC signal also provides the information which the channel scheduler uses at step  106  to determine the instantaneous rate for consuming information (or receiving transmitted data) for each of the remote stations associated with each queue. According to an embodiment, a DRC signal transmitted from any remote station  6  indicates that the remote station  6  is capable of receiving data at any one of eleven effective data rates shown in Table 1. Such a variable rate transmission system is described in detail in U.S. Pat. No. 6,064,678, entitled “METHOD FOR ASSIGNING OPTIMAL PACKET LENGTHS IN A VARIABLE RATE COMMUNICATION SYSTEM,” issued May 16, 2000, assigned to the assignee of the present invention and incorporated by reference herein. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Data Transmitted in 
                   
               
               
                   
                 Service Interval (Data_Size 
                 Length/Transmission Time 
               
               
                 Effective Data 
                 (L i )) 
                 of Service Interval (L i ) 
               
               
                 Rate (R i ) 
                 (bits) 
                 (time slots ≈ 1.667 msec) 
               
               
                   
               
             
             
               
                  38.4 kbps 
                 1024 
                 16  
               
               
                  76.8 kbps 
                 1024 
                 8 
               
               
                 102.4 kbps 
                 1024 
                 6 
               
               
                 153.6 kbps 
                 1024 
                 4 
               
               
                 204.8 kbps 
                 1024 
                 3 
               
               
                 307.2 kbps 
                 1024 
                 2 
               
               
                 614.4 kbps 
                 1024 
                 1 
               
               
                 921.6 kbps 
                 1536 
                 1 
               
               
                 1228.8 kbps  
                 2048 
                 1 
               
               
                 1843.2 kbps  
                 3072 
                 1 
               
               
                 2457.6 kbps  
                 4096 
                 1 
               
               
                   
               
             
          
         
       
     
     The channel scheduler  12  at step  108  determines the length of a service interval during which data is to be transmitted to any particular remote station  6  based upon the remote station&#39;s associated instantaneous rate for receiving data (as indicated in the most recently received DRC signal). According to an embodiment, the instantaneous rate of receiving data R i  determines the service interval length L i  associated with a particular data queue at step  106 . Table 1 summarizes the L i  values for each of the eleven possible rates for receiving data at a remote station  6 . 
     The channel scheduler  12  at step  110  selects the particular data queue for transmission. The associated quantity of data to be transmitted is then retrieved from a data queue  40  and then provided to the channel element  42  for transmission to the remote station  6  associated with the data queue  40 . As discussed below, the channel scheduler  12  at step  110  selects the queue for providing the data which is transmitted in a following service interval using information including the weight associated with each of the queues. The weight associated with the transmitted queue is then updated at step  112 . 
       FIG. 4  shows a diagram illustrating the timing of the channel scheduler  12  and data transmission in service intervals.  FIG. 4  shows three discrete service intervals during transmission at time intervals S −1 , S 0  and S 1 . As steps  104  through  112  of the scheduling algorithm of  FIG. 4  are executed during service intervals  202 , the scheduling algorithm executing during the interval S 0  preferably determines which queue is to be transmitted at the interval S 1 . Also, as discussed below, the execution of steps  104  through  112  relies on information in the DRC signals received from the remote stations  6 . This information is preferably extracted from the most recently received DRC signals. Accordingly, the steps  104  through  110  are preferably executed and completed during the last time slot of the service intervals. This ensures that the decisions for allocating the subsequent service interval are based upon the most recent DRC signals (i.e., those DRC signals which are in the time slot immediately preceding the execution of the steps  104  through  110 ). 
     Steps  104  and  110  are preferably completed within a time slot while providing sufficient time for the channel scheduler  12  to schedule the transmissions for the subsequent service interval. Thus the processor and RAM employed in the channel scheduler  12  are preferably capable of performing the steps  104  through  112  within the time constraints illustrated in FIG.  4 . That is, the processor and RAM are preferably sufficient to execute steps  104  through  110 , starting at the beginning of a time slot and completing steps  104  through  110 , within sufficient time before the end of the time slot for the channel scheduler  12  to schedule transmissions in a subsequent service interval. 
     One skilled in the art will appreciate that channel scheduler  12  may be implemented using a variety of approaches without departing from the present invention. For example, channel scheduler  12  may be implemented using a computer system including a processor, random access memory (RAM) and a program memory for storing instructions to be executed by the processor (not shown). In other embodiments, the functions of channel scheduler  12  may be incorporated into a shared computing resource also used to perform additional functions at the base station  4  or the base station controller  10 . In addition, the processor used to perform channel scheduler functions may be a general-purpose microprocessor, digital signal processor (DSP), programmable logic device, application specific integrated circuit (ASIC), or other device capable of performing the algorithms described herein, without departing from the present invention. 
       FIG. 5  shows an embodiment of the process for updating the weights at step  112  (FIG.  3 ). Step  302  computes a rate threshold “C” which is an average of all of the instantaneous rates associated with queues having data. The instantaneous rates associated with queues which do not include data are preferably eliminated for this calculation. Step  304  compares the instantaneous rate associated with the Selected_Queue selected at step  110 . If an instantaneous rate associated with a Selected_Queue exceeds the threshold C, step  306  increments the weight associated with this Selected_Queue by a lower value which is preferably a number representing the quantity of data to be transmitted during the subsequent service interval from the Selected_Queue in units such as bits, bytes or megabytes. If the instantaneous rate associated with the Selected_Queue does not exceed the threshold calculated at step  302 , step  308  increments the weight of the Selected_Queue by a higher value which is preferably a multiple “G” of the quantity of data which is to be transmitted during the subsequent service interval from the Selected_Queue such as bits, bytes or megabyte quantities. 
     The selection of G is preferably based upon a fairness criteria which favors the allocation of service intervals to remote stations  6  having the capacity to receive data at higher rates. The system designer selects the size of G based upon the extent to which remote stations  6  receiving data at the higher rates are to be favored over the slower receiving remote stations  6 . The larger the value of G, the more efficiently the forward link of the base station  4  is utilized. This efficiency, however, comes at the cost of depriving the subscribers of the slower receiving remote station  6  of the transmission resources of the forward link. The system designer therefore preferably selects the value of G in a manner which balances the two competing objectives of 1) enhancing the overall efficiency of the forward link and 2) preventing acute deprivation of the slower receiving remote stations  6 . 
     Steps  304 ,  306  and  308  illustrate that selected queues having a faster associated instantaneous data rate (i.e., exceeding the threshold C) will tend to have the associated weight incremented by only a small amount, while selected queues having a lower data rate (i.e., not exceeding the threshold C) will have its associated weight incremented by a significantly greater amount. As discussed below in connection with the algorithm performed at step  110  of  FIG. 3 , this implementation tends to favor servicing remote stations which receive data at relatively faster rates over those remote stations receiving data at lower data rates. 
     This tendency enhances the throughput efficiency of the base station  4  in transmitting data in the forward link. However, as the weights associated with the often selected queues associated with the remote stations having the higher rates of receiving data (i.e., exceeding the threshold C) continue to be incremented, these weights eventually approach the weights of the queues associated with the less often selected queues associated with the remote stations having the slower rates of receiving data (i.e., not exceeding the threshold). The selection process at step  110  will then begin to favor the slower receiving remote stations as the weights of the faster receiving remote stations begin to exceed the weights of the slower receiving remote stations. This imposes a fairness restraint on the selection process at step  110  by preventing the faster receiving remote stations from dominating the forward link transmission resources of the base station to the exclusion of the slower receiving remote stations. 
     It is an objective of the present embodiment to ensure that queues having no data to transmit are not given an unfair preference for transmission over those queues having data. At steps  102  and  104 , all new queues are initialized with a weight of zero. Without being selected, such queues will continue to maintain the weight of zero provided that the queue is not selected. Therefore, step  310  in  FIG. 5  decrements the weight of all queues, to a value no less than zero, by the minimum weight of any queue with data (determined at step  309 ). This is illustrated in detail below in an example shown in Table 2. 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 Remote 
                 Remote 
                   
               
             
          
           
               
                   
                 Weights at the End of the 
                 Station 
                 Station 
                 Amount by 
               
               
                   
                 Service Interval 
                 Selected in 
                 Serviced in 
                 Which 
               
             
          
           
               
                 Service 
                 Remote 
                 Remote 
                 Remote 
                 Service 
                 Service 
                 Weights are 
               
               
                 Interval 
                 Station 1 
                 Station 2 
                 Station 3 
                 Interval 
                 Interval 
                 Decremented 
               
               
                   
               
               
                 0 
                 0 
                 0 
                 0 
                 N/A 
                 N/A 
                 N/A 
               
               
                 1 
                 1 
                 0 
                 0 
                 1 
                 N/A 
                 0 
               
               
                 2 
                 1 
                 1 
                 0 
                 2 
                 1 
                 0 
               
               
                 3 
                 0 
                 0 
                 7 
                 3 
                 2 
                 1 
               
               
                 4 
                 1 
                 0 
                 7 
                 1 
                 3 
                 0 
               
               
                 5 
                 0 
                 0 
                 6 
                 2 
                 1 
                 1 
               
               
                 6 
                 1 
                 0 
                 6 
                 1 
                 2 
                 0 
               
               
                 7 
                 0 
                 0 
                 5 
                 2 
                 1 
                 1 
               
               
                   
               
             
          
         
       
     
     This example has three remote stations each associated with a queue of data to be transmitted from a base station. The example assumes that remote station  1  has the highest data rate, remote station  2  has the next highest data and remote station  3  has the lowest data rate. For simplicity, it is assumed these data rates do not change over the service intervals  1  through  7 . It is assumed that the data rates at remote station  1  and remote station  2  each exceed the threshold C at step  304 , and that the data rate associated with remote station  3  does not exceed this threshold. It is further assumed that step  306  will increment the weight of the Selected_Queue by one if the Selected_Queue is associated with the remote station  1  or remote station  2 , and that step  308  will increment the weight of the Selected_Queue by eight if the Selected_Queue is associated with the remote station  3 . 
     At service interval  1 , the channel scheduler  12  selects the remote station  1  to receive data in the subsequent service interval, since, while it has the lowest weight along with remote stations  2  and  3 , remote station  1  has a higher rate of receiving data. Data is then transmitted to remote station  1  during service interval  2  and the weight associated with the remote station  1  is incremented by one at the end of service interval  1 . The channel scheduler  12  then selects remote station  2  to receive data in service interval  3  (since remote station  2  has the lowest weight and a faster rate of receiving data than does remote station  3 ). As shown in Table 2, the weight of remote station  2  is incremented by 1 by the end of the service interval  2 . 
     At the beginning of service interval  3 , remote station  3  has the lowest weight. The channel scheduler  12  selects remote station  3  to receive data at the service interval  4 . The state at the end of interval  3  reflects that weight of the remote station  3  was incremented from zero to eight to reflect the selection of the remote station  3 . The weights at the remote stations  1 ,  2  and  3  are then decremented by one which is consistent with step  310  ( FIG. 5 ) as indicated in Table 2. At service interval  4 , the channel scheduler  12  selects remote station  1  to receive data in service interval  4  since the queue associated with remote station  1  has the lowest weight and the highest rate for receiving data. 
     The channel scheduler  12  at service interval  5  selects remote station  2  to receive data during service interval  6 . The weight associated with the remote station  2  is first incremented at step  306  and the weights of all of the remote stations are decremented by one as reflected in the weights at the end of the service interval  5  as shown in Table 2. Remote station  1 , having the lowest weight, is then selected again in service interval  6  for receiving data in service interval  7 . 
     As shown in the embodiment of  FIG. 1 , the remote stations  6  are mobile and capable of changing associations among the different base stations  4 . For example, a remote station  6   f  is initially receiving data transmissions from the base station  4   f . The remote station  6   f  may then move out of the cell of the base station  4   f  and into the cell of the base station  4   g . The remote station  6   f  can then start transmitting its DRC signal to alert the base station  4   g  instead of the base station  4   f . By not receiving a DRC signal from the remote station  6   f , logic at the base station  4   f  deduces that the remote station  6   f  has disengaged and is no longer to receive data transmissions. The data queue associated with the remote station  6   f  may then be transmitted to the base station  4   g  via a land line or RF communication link. 
     According to an embodiment of the present invention, the channel scheduler  12  at a base station  4  assigns a weight to a queue of a remote station  6  which has disengaged and re-engaged the base station  4 . Rather than simply assigning a weight of zero to the re-engaging remote station  6 , the base station  4  preferably assigns a weight which does not give the re-engaging remote station an unfair advantage for receiving data transmissions from the base station  4 . In one embodiment, the channel scheduler  12  randomly assigns a weight to the queue of the re-engaging remote station  6  according to a uniform distribution between zero and the highest weight of any queue currently serviced by the channel scheduler  12 . In another embodiment, the base station  4  receives the weight of the re-engaging remote station  6  from the last base station associated with the remote station  6  via a land line transmission. 
     In an alternative embodiment, the channel scheduler  12  gives a re-engaging remote station  6  “partial credit” for having a past association with the base station  4 . The channel scheduler  12  determines the number of time slots that the previous service interval spans “n,” and maintains a history of the number of time slots 
     “m i ” during the previous service interval that the base station  4  received a DRC from the remote station i. The weight of the queue associated with the remote station i is then decremented at step  310  as follows: 
       W   i   =W   i   −m   i   /n×W   min   
     where: 
     
         
         
           
             W i =the weight of queue i 
             W min =the minimum weight of any queue with data to transmit to a remote station 
             m i =the number of time slots during the previous service interval that the base station received a DRC from the remote station i 
             n=the number of time slots that the previous service interval spans 
           
         
       
    
       FIGS. 6   a  through  6   c  show a flow diagram illustrating the logic performed at step  110  ( FIG. 3 ) according to an embodiment. Step  402  initializes the identity of the Selected_Queue as being the first data queue having data for transmission to an associated remote station  6 . At steps  402  through  422 , the channel scheduler  12  determines whether this initial queue or a different data queue having data should be selected for transmission to its associated remote station  6 . The Next_Queue is then retrieved at step  406  and step  408  determines whether this Next_Queue has data. If the Next_Queue does not have data, execution returns to step  406  to select a subsequent data queue. Otherwise, if this Next_Queue has data, the identity of the Current_Queue is assigned the Next_Queue. If the weight of the Current_Queue exceeds the weight of the Selected_Queue, step  412  returns execution to step  406  to retrieve a subsequent Next_Queue. Otherwise, step  414  determines whether the weight of the Current_Queue is less than the weight of the Selected_Queue. If the weight of the Current_Queue is less than the weight of the Selected_Queue, step  414  moves execution to step  420  to assign the identity of the Current_Queue to the Selected_Queue. 
     Otherwise, the logic at steps  412  and  414  dictate that if execution reaches step  416 , the weights of the Current_Queue and the Selected_Queue are equal. Step  424  assigns the Current_Queue as the Selected_Queue when the following conditions are met:
         1) the instantaneous rate of receiving data associated with the Current_Queue exceeds the instantaneous rate of receiving data associated with the Selected_Queue (step  416 ); and   2) if the service interval assigned to the Current_Queue would exhaust all of the data stored in the Current_Queue, leaving a fractional remainder of data in the service interval assigned to the Current_Queue, such a fractional remainder would not exceed any such fractional remainder of data in the Selected_Queue in the service interval assigned to the Selected_Queue (steps  418  through  422 ).       

     Otherwise, execution returns to step  406  to select the Next_Queue. 
       FIGS. 7   a  through  7   d  show a flow diagram illustrating a second embodiment of the logic performed at the step  110  for selecting a queue for transmission to an associated remote station  6 . In this embodiment, it is assumed that each base station  4  periodically transmits a control signal to all associated remote stations  6  having a fixed duration (such as eight to sixteen time slots). According to an embodiment, the base station  4  transmits this control signal once every 400 msec. During this control transmission, no data from any data queue  40  ( FIG. 2 ) may be transmitted to an associated remote station  6 . An objective of the embodiment shown at  FIGS. 7   a  and  7   b  is to select only those data queues which may completely transmit for a service interval having a length determined at step  108  before the beginning of the next control signal transmission. 
     Steps  499  through  507  filter all of the queues to determine which queues are candidates for completion before the beginning of the next control signal transmission. Step  499  determines the time “T” until the next control signal transmission by, for example, subtracting the scheduled time of the beginning of the next control signal transmission by the beginning of the next scheduled service interval. Step  501  determines whether the length of service interval associated with each queue determined at step  108  can be transmitted within the time T based upon the instantaneous rate of transmission for the remote unit  6  associated with the queue determined at step  106 . According to an embodiment, step  501  compares the service interval length with T. Step  502  then determines whether the Next_Queue includes any data. If the Next_Queue satisfies the conditions at steps  501  and  502 , the identity of the Next_Queue is assigned to the Selected_Queue. 
     Steps  504  through  508  examine the remaining data queues to determine the data queues having associated service interval (determined at step  108 ) which may be completely transmitted prior to the beginning of the next control signal transmission. Upon meeting the criteria set forth at steps  507  and  508 , the Current_Queue is assigned as the Next_Queue. Steps  512  through  526  then perform a selection process according to queue weights in a manner similar to that discussed above in connection with steps  412  through  426  in  FIGS. 6   a  through  6   c . However, in the embodiment of  FIGS. 7   a  through  7   d , only those data queues having an assigned packet length which may be completed prior to the beginning of the next control signal transmission may be candidates for selection based upon the associated queue weight. 
       FIGS. 8   a  and  8   b  show a flow diagram illustrating a third embodiment of the logic executed at step  110  at  FIG. 3  for selecting a queue for transmission. In this embodiment, subscribers of select remote units  6  are guaranteed a minimum average rate of data transmission. For each such premium remote unit, the channel scheduler  12  maintains a timer which alerts the channel scheduler  12  to schedule a transmission to its premium queue, regardless of the weights associated with the remaining queues. The time interval for the particular timer is determined based upon the average data rates guaranteed to the customer, the service interval assigned to that data queue at step  108  (see center column of Table 1), and any instantaneous data rate for receiving data determined at step  106 . Thus, the time interval associated with the premium queue timer is dynamic with respect to these values. According to an embodiment, the timer interval is determined whenever the timer is reset as follows: 
         T   j     =       Data_Size   ⁢     (     L   j     )         r   j             
where:
 
     T j =timer interval for premium queue j 
     Data_Size (L j )=quantity of data to be transmitted in service interval assigned to the premium queue j 
     r j =average data transmission rate guaranteed to the premium subscriber associated with the premium queue j 
     The timer is reset at either of two events. The first event initiating a reset of the timer is an expiration of the timer interval. The second event for initiating a reset of the timer is a selection of the associated premium data queue based upon its associated weight in a manner discussed above with reference to  FIGS. 6   a  through  6   c.    
     Steps  606  through  610  determine whether the Next_Queue is a premium queue entitled to a minimum average rate of receiving data and, if so, whether the timer associated with that premium queue has expired. If the timer has expired, step  612  assigns the identity of the Next_Queue to the Selected_Queue and execution at step  110  completes. The weight of the selected queue is then updated at step  112  as discussed above. If there are no premium queues with an expired timer, step  614  initiates the selection of the queue for transmission in the subsequent service interval at step  616  based upon the weights of the queues in a manner discussed above with references to  FIGS. 6   a  through  6   c . If the queue selected at step  616  is a premium queue having an associated timer, step  618  initiates a reset of the timer associated with the selected queue at step  620 . 
     As outlined above, the timer associated with any particular premium data queue is reset following its selection based upon the associated weight at step  620 . The associated timer is also reset when it expires before selection of the data queue. The timer thus alerts the channel scheduler  12  to override the logic directed to selecting data queues based upon weights to ensure that this subscriber is associated with the premium data queues receive a guaranteed minimum average rate of receiving data. 
       FIG. 9  shows an alternate embodiment of the process for updating the weights at step  110  (FIG.  3 ). This alternate embodiment allows the selection of a queue that does not have the smallest weight. Volatility in transmission rates makes it advantageous to sometimes select a queue that does not have the smallest weight. For example, a queue might have the lowest weight during a time slot when its requested rate is temporarily low. If the rate increases in a subsequent time slot, then transmission can then take place at the higher rate. Waiting a few time slots may allow transmission from that low-weight queue at a higher requested rate. 
     The alternate embodiment begins with step  702  by determining the sum of the values M and K. M is the minimum weight of all queues, including those with no data to send or with invalid DRC values. K is an offset used to define a range of weight values within which a queue is selected based on a Desirability Metric. 
     After determining the sum of M and K, a decision is made in step  704  about whether or not to use the Desirability Metric for queue selection. The Desirability Metric is only used to choose among queues having weights less than or equal to (M+K) as well as having valid DRC&#39;s and data to send. 
     First, all queues having valid DRC&#39;s and data to send are evaluated to determine how many also have a weight greater than the sum (M+K). If all queues having valid DRC&#39;s and data to send also have weights greater than the sum (M+K), then the lowest-weight queue among them is selected in step  706 . If one or more queues with valid DRC&#39;s and data to send have a weight less than or equal to (M+C), then one of those queues is selected in step  708  according to the Desirability Metric. 
     Once a queue is selected in either step  706  or step  708 , then queue selection is complete (shown as step  710 ), and processing continues from step  110  to  112  as in FIG.  3 . 
       FIG. 10  is a more detailed flow chart depicting an exemplary embodiment of the queue selection method depicted in FIG.  9 . In  FIG. 10 , after determining in step  702  the sum (M+K), each queue that has a valid DRC and data to send is evaluated and one queue is selected and returned from step  110 . 
     In the exemplary embodiment, the first step  702  is again to determine the sum (M+K). If there are no queues having data and a valid DRC, then no queue is selected and the method proceeds to step  772  (return to the flow of FIG.  3 ). If there is only one queue in the list having data and a valid DRC, that queue is returned. Otherwise, Q SEL  and Q CUR  are assigned in steps  754  and  756  from the two or more queues having data and a valid DRC. Q SEL  represents the currently selected queue, and Q CUR  represents the current queue being compared with Q SEL . Each queue having data and a valid DRC is compared with Q SEL , and if certain selection criteria are met, that queue replaces the current Q SEL . After all queues have been evaluated, the Q SEL  remaining is the selected queue for transmission and is returned at step  772 . 
     At step  758 , the weight of the selected queue Q SEL  is compared to (M+K). If the weight of Q SEL  is greater than (M+K), then the decision in step  762  of whether to replace Q SEL  with Q CUR  in step  764  is based solely on which queue has the lower weight. If at step  758  the weight of selected queue Q SEL  is less than or equal to (M+K), then the weight of current queue Q CUR  is compared to (M+K) at step  760 . If only Q SEL  is less than or equal to (M+K), then Q CUR  is not selected and the method proceeds to step  770 . If the weights of both Q SEL  and Q CUR  are less than or equal to (M+K), then in step  766  the queues are evaluated according to a Desirability Metric. If Q CUR  is deemed more desirable than Q SEL  according to the Desirability Metric, then Q CUR  becomes the new selected queue Q SEL  in step  764 ). 
     After each queue is evaluated, step  770  checks for queues having data to send and a valid DRC that remain to be evaluated. If more such queues remain to be evaluated, then one is selected in step  768  as the next Q CUR , and is evaluated beginning at step  758 . If no more queues remain to be evaluated, then the selected queue Q SEL  is returned at step  772 . 
     Several alternate embodiments of the present invention vary in the method used to determine K. In some embodiments, K is simply a constant. In other embodiments, K is calculated at the beginning of each round of queue selections. Some alternate embodiments also differ in the Desirability Metric used. Any methods of determining K or Desirability Metrics may be used without departing from the present invention. 
     In a particular embodiment using a “Modified Grade of Service (GOS)” algorithm, K is a constant that does not depend on the number of remote stations in the system. A filtered average throughput is maintained for each user and associated queue according to the following equation:
 
Average_Throughput={(11/TC)*Old_Average_Throughput}+(1/TC*Rate)  (1)
 
where Average_Throughput is the average throughput for each queue used in calculating the Desirability Metric value of the queue, TC is a time constant, Old_Average_Throughput is the previous value of Average_Throughput, and Rate is the bit rate used to transmit from the queue in each time slot. The Average_Throughput is updated for each queue for every transmission time slot. For all queues except the selected queue in each time slot, the Rate will be zero. The Desirability Metric value of any queues evaluated at steps  708  or  766  are determined according to the following equation:
 
Desirability_Metric=Current_Requested_Rate-Average_Throughput  (2)
 
where Current_Requested_Rate is the DRC rate of the queue and Average_Throughput is as calculated in Equation (1).
 
     One skilled in the art will appreciate that other formulas may be used to determine the Desirability Metric and the updated average throughput. For example, the formula for updating the average throughput may take into account more values of requested rate than the current value, such as the previous two requested rate values. Additionally, TC may vary over time based on the number of active users in the system or based on the variability of previous requested rates. Some of the alternate formulas that can be used to compute the Desirability Metric are described below. 
     The Modified GOS algorithm is advantageous in that it allows optimization of queue selection in an environment where DRC rates are changing over time. So, although one queue has the lowest weight during a particular time slot, that queue might not be selected if it is experiencing a transient decrease in its requested DRC rate. The Modified GOS algorithm permits a limited delay in transmission to such a queue in anticipation that the rate will increase for one of the subsequent time slots. 
     In an alternate embodiment using a “Modified GOS High DRC” algorithm, the Desirability Metric value is equal to the average throughput computed according to Equation (1). This algorithm results in slightly lower overall throughput, but requires less computational complexity. The Modified GOS High DRC algorithm does not require maintenance of a filtered average throughput value for each queue. 
     In another alternate embodiment using a “Hybrid” algorithm, the Desirability Metric value is equal to the Rate divided by Average_Throughput. The Hybrid algorithm sacrifices throughput to achieve a greater degree of “fairness” in selecting a queue for transmission by selecting a queue based on the percentage by which the requested rate exceeds the average rate. For example, the algorithm selects a first user having a requested Rate of 76.8K and an Average_Throughput of 30K instead of a second user having a requested Rate of 1228.8K and an Average_Throughput of 900K. Although greater overall throughput can be achieved by taking advantage of the rate spike of the second user, the Hybrid algorithm chooses the first user because the first user has a current rate that is more than twice his or her average throughput. 
     In a suboptimal embodiment, the Hybrid algorithm is modified by varying K according to the number of users to create a “Modified Hybrid” algorithm. In the Modified Hybrid algorithm, K is inversely proportional to the number of users, and the Desirability Metric value is equal to the Rate divided by Average_Throughput. By varying K according to the number of users to modify the Modified GOS and Modified GOS High DRC algorithms, similar alternate suboptimal embodiments are created. 
     In an alternate suboptimal embodiment, the Hybrid algorithm is modified by varying K according to the number of users to create a “Modified Hybrid” algorithm. The Modified Hybrid algorithm seeks to impose an additional degree of “fairness” at the expense of throughput. 
       FIG. 11   a  is a block diagram of a forward link architecture configured in accordance with an exemplary embodiment of the present invention. The data is partitioned into data packets and provided to CRC encoder  712 . For each data packet, CRC encoder  712  generates frame check bits (e.g., the CRC parity bits) and inserts code tail bits. The formatted packet from CRC encoder  712  comprises the data, the frame check and code tail bits, and other overhead bits described below. In the exemplary embodiment, encoder  714  encodes the formatted packet in accordance with the encoding format disclosed in U.S. Pat. No. 5,933,462, entitled “SOFT DECISION OUTPUT DECODER FOR DECODING CONVOLUTIONALLY ENCODED CODEWORDS”, issued Aug. 3, 1999, assigned to the assignee of the present invention and incorporated by reference herein. One skilled in the art will appreciate that other well known encoding formats can also be used and are within the scope of the present invention. The encoded packet from encoder  714  is provided to interleaver  716 , which reorders the code symbols in the packet. The interleaved packet is provided to frame puncture element  718 , which removes a fraction of the packet in a manner described below. The punctured packet is provided to multiplier  720 , which scrambles the data with the scrambling sequence from scrambler  722 . Puncture element  718  and scrambler  722  are described in detail in the aforementioned U.S. patent application Ser. No. 08/963,386, now U.S. Pat. No. 6,574,211. The output from multiplier  720  comprises the scrambled packet. 
     The scrambled packet is provided to variable rate controller  730 , which demultiplexes the packet into K parallel inphase and quadrature channels, where K is dependent on the data rate. In the exemplary embodiment, the scrambled packet is first demultiplexed into the inphase (I) and quadrature (Q) streams. In the exemplary embodiment, the I stream comprises even-indexed symbols and the Q stream comprises odd-indexed symbols. Each stream is further demultiplexed into K parallel channels such that the symbol rate of each channel is fixed for all data rates. The K channels of each stream are provided to Walsh cover element  732 , which covers each channel with a Walsh function to provide orthogonal channels. The orthogonal channel data are provided to gain element  734  which scales the data to maintain a constant total-energy-per-chip (and hence constant output power) for all data rates. The scaled data from gain element  734  is provided to multiplexer (MUX)  760 , which multiplexes the data with the preamble. The preamble is discussed in detail in the aforementioned U.S. patent application Ser. No. 08/963,386, now U.S. Pat. No. 6,574,211. The output from MUX  760  is provided to multiplexer (MUX)  762 , which multiplexes the traffic data, the power control bits, and the pilot data. The output of MUX  762  comprises the I Walsh channels and the Q Walsh channels. 
     In the exemplary embodiment, a forward link pilot channel provides a pilot signal that is used by remote stations  6  for initial acquisition, phase recovery, timing recovery, and ratio combining. These uses are similar to those in CDMA communication systems conforming to the IS-95 standard. In the exemplary embodiment, the pilot signal is also used by remote stations  6  to perform the C/I measurement. 
     The block diagram of the forward link pilot channel of the exemplary embodiment is also shown in  FIG. 11   a . In the exemplary embodiment, the pilot data comprises a sequence of all zeros (or all ones) which is provided to multiplier  756 . Multiplier  756  covers the pilot data with Walsh code W 0 . Since Walsh code W 0  is a sequence of all zeros, the output of multiplier  756  is the pilot data. The pilot data is time multiplexed by MUX  762  and provided to the I Walsh channel which is spread by the short PN I  code within complex multiplier  814  (see  FIG. 11   b ). 
     The exemplary block diagram of the power control channel is also shown in  FIG. 11   a . The Reverse Power Control (RPC) bits are provided to symbol repeater  750 , which repeats each RPC bit a predetermined number of times. The repeated RPC bits are provided to Walsh cover element  752 , which covers the bits with the Walsh covers corresponding to the RPC indices. The covered bits are provided to gain element  754 , which scales the bits prior to modulation to maintain a constant total transmit power. In the exemplary embodiment, the gains of the RPC Walsh channels are normalized so that the total RPC channel power is equal to the total available transmit power. The gains of the Walsh channels can be varied as a function of time for efficient utilization of the total base station transmit power while maintaining reliable RPC transmission to all active remote stations  6 . In the exemplary embodiment, the Walsh channel gains of inactive remote stations  6  are set to zero. Automatic power control of the RPC Walsh channels is possible using estimates of the forward link quality measurement from the corresponding DRC channel from remote stations  6 . The scaled RPC bits from gain element  754  are provided to MUX  762 . 
     A block diagram of the exemplary modulator used to modulate the data is illustrated in  FIG. 11   b . The I Walsh channels and Q Walsh channels are provided to summers  812   a  and  812   b , respectively, which sum the K Walsh channels to provide the signals I sum  and Q sum , respectively. The I sum  and Q sum  signals are provided to complex multiplier  814 . Complex multiplier  814  also receives short PN I  and PN Q  sequences from short code generator  838 , and multiplies the two complex inputs in accordance with the following equation: 
      ( I   mult   +jQ   mult )=( I   sum   +jQ   sum )·( PN   —   I+jPN   —   Q )=( I   sum   ·PN   —   I−Q   sum   ·PN   —   Q )+ j ( I   sum   ·PN   —   Q+Q   sum   ·PN   —   I ),  (3) 
     where I mult  and Q mult  are the outputs from complex multiplier  814  and j is the complex representation. The I mult  and Q mult  signals are provided to filters  816   a  and  816   b , respectively, which filter the signals. The filtered signals from filters  816   a  and  816   b  are provided to multipliers  818   a  and  818   b , respectively, which multiply the signals with the inphase sinusoid COS(w c t) and the quadrature sinusoid SIN(w c t), respectively. The I modulated and Q modulated signals are provided to summer  820  which sums the signals to provide the forward modulated waveform S(t). 
     The block diagram of the exemplary traffic channel shown in  FIGS. 3A and 3B  is one of numerous architectures that support data encoding and modulation on the forward link. Other architectures, such as the architecture for the forward link traffic channel in the CDMA system conforming to the IS-95 standard, can also be utilized and are within the scope of the present invention. 
     For example, one skilled in the art will appreciate that complex multiplier  814  and short code generator  838  can be replaced by a pseudo-noise (PN) spreader that performs simple multiplication of signals by PN short codes instead of complex multiplication. In addition, encoder  714  may use any of several forward error correction techniques including turbo-coding, convolutional coding, or other forms of soft decision or block coding. Also, interleaver  716  may utilize any of a number of interleaving techniques, including block interleaving, e.g., bit reversal interleaving, or pseudo-random interleaving. 
     While there has been illustrated and described what are presently considered to be the preferred embodiments of the present invention, it will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from the true scope of the invention. Additionally, many modifications may be made to adapt a particular situation to the teachings of the present invention without departing from the central inventive concept described herein. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed, but that the invention include all embodiments falling within the scope of the appended claims.