Abstract:
An apparatus and method of delivering data in a wireless communication system, the apparatus and method comprising of determining, based on first criteria, if a shared channel can utilized to transmit an actual data packet; converting said actual data packet into one or more first data packets, wherein each said one or more first data packet represent a portion of said actual data packet; and transmitting each said one or more first data packet using said shared channel.

Description:
REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT  
       [0001]     This application is related to the following co-pending U.S. patent applications: U.S. application Ser. No. 10/340,507, filed on Jan. 10, 2003 and U.S. application Ser. No. 10/426,546, filed on Apr. 29, 2003, both assigned to the assignee hereof, and expressly incorporated herein by reference. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates generally to communication and more specifically to techniques for transmitting data on using a shared channel.  
       BACKGROUND  
       [0003]     Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems. Typically, a wireless communication system comprises several base stations, wherein each base station communicates with the mobile station using a forward link and each mobile station communicates with base station using a reverse link.  
         [0004]     In the communication system described above, mobile station makes a resource assignment request to the base station. In response, the base station assigns the requested resource, if available, and provides the assignment information using a communication channel. Typically, the mobile stations are assigned a forward link data channel resources via an assignment messages that is transmitted over a designated channel.  
         [0005]     Most of the communication system described above use a forward link and a reverse link in conjunction with a Hybrid Automatic Repeat Request (H-ARQ) scheme to communicate data and other information. H-ARQ techniques have been shown to provide significant improvement in capacity. With Hybrid ARQ, a packet is sent using multiple transmissions. The packet transmission could be terminated early if the receiver can decode the packet prior to receiving all the transmission. However, when there is large number of mobile stations requesting resource assignments, the number of transmissions increases when using H-ARQ. In order to ensure that assignment information is received timely, the base station would have to increase the bandwidth, lower the number of transmissions, requiring additional signaling information or not use H-ARQ.  
         [0006]     Several methods have been employed in order maintain bandwidth and use H-ARQ, such as a multicast system. In a typical multicast system, assignment information is broadcasted over a shared channel all the mobile stations in communication with the base stations, thereby eliminating use of a dedicated resource to provide the assignment information. However, this solution creates heavy computational burden on the mobile station, since every mobile must attempt to decode every transmitted frame.  
         [0007]     Thus, there is a need for a system and method of managing the dedicated and share resources that allows transmission of assignment or other data packets to multiple mobile stations.  
       BRIEF SUMMARY  
       [0008]     Accordingly, an apparatus and method of delivering data in a wireless communication system, the apparatus and method comprising of determining, based on first criteria, if a shared channel can utilized to transmit an actual data packet; converting said actual data packet into one or more first data packets, wherein each said one or more first data packet represent a portion of said actual data packet; and transmitting each said one or more first data packet using said shared channel.  
         [0009]     A more complete appreciation of all the advantages and scope of the invention can be obtained from the accompanying drawings, the description and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:  
         [0011]      FIG. 1  shows a diagram of a wireless multiple-access communication system;  
         [0012]      FIG. 2  illustrates a superframe structure;  
         [0013]      FIG. 3  illustrates a data packet conversion diagram;  
         [0014]      FIG. 4  shows a flow diagram of an embodiment of a process to transmit data to using the shared channel;  
         [0015]      FIGS. 5A and 5B  shows a process for evaluating data received on the shared channel; and  
         [0016]      FIG. 6  show block diagrams of a base station and a terminal, respectively, in the OFDMA system. 
     
    
     DETAILED DESCRIPTION  
       [0017]     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The word “listening” is used herein to mean that a terminal is receiving and processing data received on a given channel.  
         [0018]      FIG. 1  shows a diagram of a wireless multiple-access communication system  100  that employs multi-carrier modulation. System  100  includes a number of access points (AP)  110  that communicate with one or more access terminal (AT)  120  (only two access points  110   a  and  110   b  are shown in  FIG. 1  for simplicity). An access point  110  ( 110  is further discussed in  FIG. 6 , infra) is a fixed station that is used for communicating with the access terminals. An access point  110  may also be referred to as a base station or some other terminology.  
         [0019]     An access point (AP), for example access point  110 , is an electronic device configured to communicate with one or more user access terminals and may also be referred to as an access node, access network, a base station, base terminal, fixed terminal, a fixed station, base station controller, a controller, transmitter or some other terminology. The access point, base terminal, and base station are interchangeably used in the description below. The access point may be a general purpose computer, a standard laptop, a fixed terminal, an electronic device configured to transmit, receive and process data according to air interface methods defined by an OFDMA, CDMA, GSM, WCDMA, etc. system. The access point may be an electronic module comprising one or more computer chips controlled by a controller or a processor for transmitting, receiving and processing data according to air interface methods defined by an OFDMA, CDMA, GSM, WCDMA, etc.  
         [0020]     An access terminal the access terminal  120 , may be an electronic device configured to communicate with the access point via a communication link. The access terminal may also be referred to as an terminal, a user terminal, a remote station, a mobile station, a wireless communication device, recipient terminal, or some other terminology. The access terminal, mobile terminal, user terminal, terminal are interchangeably used in the description below. Each access terminal  120  may communicate with one or multiple access points on the downlink and/or uplink at any given moment. The downlink (i.e., forward link) refers to transmission from the access point to the access terminal  120 , and the uplink (i.e., reverse link) refers to transmission from the access terminal  120  to the access point. The access terminal  120  may be any standard laptop, personal electronic organizer or assistant, a mobile phone, cellular phone, an electronic device configured to transmit, receive and process data according to air interface methods defined by an OFDMA, CDMA, GSM, WCDMA, etc. system. The access terminal may be an electronic module comprising one or more computer chips controlled by a controller or a processor for transmitting, receiving and processing data according to air interface methods defined by an OFDMA, CDMA, GSM, WCDMA, etc. system.  
         [0021]     A system controller  130  couples to the access points and may further couple to other systems/networks (e.g., a packet data network). System controller  130  provides coordination and control for the access points coupled to it. Via the access points, system controller  130  further controls the routing of data among the terminals, and between the terminals and other users coupled to the other systems/networks.  
         [0022]     The techniques described herein for managing the transmission using the shared channel may be implemented in various wireless multiple-access multi-carrier communication systems. For example, system  100  may be an OFDMA, CDMA, GSM, WCDMA, etc. system that utilizes data transmission.  
         [0023]     For clarity, these techniques are described for an OFDMA system that utilizes orthogonal frequency division multiplexing (OFDM). OFDM effectively partitions the overall system bandwidth into a number of n orthogonal frequency subcarriers, which are referred to as tones, sub-bands, bins, frequency channels, and so on.  
         [0024]     In an OFDMA system, a superframe is used which is the fundamental unit of transmission on the forward and reverse links that defines a time interval. A forward link (FL) superframe is used to transmit information from the access point  110  to THE ACCESS TERMINAL  120 . FL superframe is further discussed below in  FIG. 2 . In an embodiment, on the forward link, a superframe consists of a preamble of 6 OFDM symbols followed by a series of 6 forward link PHY frames. The OFDM symbol is comprised of n individually modulated subcarriers, which carry complex-valued data, where n is computed as a function of the system bandwidth. Generally, the superframe is multiplexed in time (OFDM symbol) and frequency (subcarrier).  
         [0025]     In the OFDMA system, multiple orthogonal “traffic” channel may be defined whereby (1) each subcarrier is used for only one traffic channel in any given time interval and (2) each traffic channel may be assigned zero, one, or multiple subcarriers in each time interval.  
         [0026]      FIG. 2  illustrates a frame structure  200  for a forward link superframe of OFDMA system according to an embodiment. The forward link superframe  200  comprises a superframe preamble portion  202  followed by 6 PHY Frames portion  204 . The superframe preamble portion  202  comprises a plurality of orthogonal channels, an Acquisition Channel (ACQCH)  220 , a Primary Broadcast Channel (PBCH)  222  (also referred to an SYNC channel), a Quick Paging Channel (QPCH)  224 , and an Other Sector Interference Channel (OSICH)  226 . Each PHY frame (for example  204   n ) of the PHY frame portion  204  comprises a plurality of physical channels, a pilot one or more pilot channel  240  (for example a Common Pilot Channel (CPICH). Also, if present, an Auxiliary Pilot Channel (AuxPICH)), a Shared Signaling Channel (SSCH)  250 , a Data Channel (DCH)  248 , a Secondary Broadcast Channel (sBCH)  242 , a Shared Data Channel (SDCH)  244  and a Power Control Channel (PCCH)  246 .  
         [0027]      FIG. 3  illustrates a data packet conversion diagram  300  which shows the conversion of an actual data packet, according to an embodiment. In an embodiment, the data packet may be converted to form TX data packets using one or more stages, a first stage  310 , a second stage  312  and a third stage  314 , described below.  
         [0028]     During a first stage  310 , for an intended recipient receiving an assignment, the data packet comprising the assignment is encrypted to form an encrypted data block. For example, encrypted data block  302  for MT 1  (targeted or intended for terminal  1 ), encrypted data block  304  for MT-ALL (targeted or intended for all the terminals), encrypted data block  306  for MT 2  (targeted or intended for terminal  2 ), and so on.  
         [0029]     During a second stage  312 , each encrypted data block, for example  302 , is further split or divided to form an encoded data block series  316  (also referred to as “series”) comprising a plurality of equal sized encoded data block  316   i  through  316   n , wherein i represents the first encoded data block and n represents number of retransmissions to be used. The n value of may be determined by bandwidth available and/or number of access terminals requesting information from the access point  110 . More the users requesting information from AN, the lower the value of n.  
         [0030]     During a third stage  314 , a prefix  322  (also refer to as a preamble) portion may be added to the encoded data block  316   i  to form a TX data packet  324 . The prefix  322  may be added to the first encoded data block  316   i  of the encoded data block series  316  and not the remaining encoded data blocks. The prefix  322  comprises one or more information bits. The information bit(s) providing a format of the packet, the access terminal  120  identification, modulation or any other information controller determines necessary for effective demodulation of the TX data packet  324 . In another embodiment, the prefix  322  is added to all the encoded data blocks of the encoded data block series  316 . Also, in another embodiment, the access point  110  may use only the first and second stages  310  and  312  to convert the actual data packet. This is generally performed by not attaching the prefix  322  to any of the encoded data blocks of the series  316 . (e.g., the length of the prefix  322  would be zero for the TX data packet  324 ).  
         [0031]     In an OFDMA system, the access point  110  determines if the SDCH  244  resource should be used to transmit the channel assignments. Generally, the SDCH  244  does not required pre-assignment of resources in order to received data and all terminals process this channel. Using the techniques described below, the may transmit data targeted to an intended access terminal  120 . The access point  110  using scheduler  630  and controller  620 , which constantly monitors the system conditions and make proper adjustments as necessary. For example, the access point  110  checks to see whether the number of encoded data blocks to transmit on SSCH have reached a capacity threshold (a maximum number of encoded data blocks allowable to be queued). The capacity threshold may be dynamically adjusted by the controller  620 . If the total number of queued encoded data blocks reach the threshold, then the access point  110  may decide to start utilizing the shared resources, such as the SDCH  244  to transmit data, for example the access terminal  120  assignment data.  
         [0032]      FIG. 4  shows a flow diagram of a process  400  used to convert the actual data packet into one or more transmittable data packets using the shared channel SDCH  244 , when used. The steps of the process  400  are executed by the access point  110 . The access point  110  is configured to utilize at least one of the components discussed in  FIG. 6 , infra. For example, the controller  620 , scheduler  630 , TX Data Processor  614 , etc. are used to execute the steps of the process  400 . At step  401 , as discussed above, the access point  110  determines if SDCH  244 , or any shared recourses, should be used to transmit actual data (for example, data representing the forward link assignment message for an access terminal  120 ). At step  402 , the access point  110  encrypts the actual data, to form encrypted data packet  302 . At step  404 , the access point  110  divides the encrypted data packet  302  to generate an encoded data block series  316  comprising one or more encoded data block  316   i - n . The number of encoded data blocks generated may vary depending on, for example, quality of service (QOS) desired by the system operator, or any other quality measurements determined by the access point  110 .  
         [0033]     At step  406 , the access point  110  converts each encoded data blocks of series  316  to the TX data packet. In an embodiment, for example, the access point  110  determines the information to include in the prefix  322  and attaches the prefix  322  only to the first encoded data blocks of series  316  when converting the encoded data block  316   i= 1 to TX data packet  324 . In another embodiment, the access point  110  attaches a prefix  322  to all the encoded data blocks of series  316 .  
         [0034]     In another embodiment, none of the encoded data blocks of the series  316  have the prefix  322  (e.g. the TX data packets are the same as the encoded data blocks). Thus, in this embodiment, the access point  110  is not required to execute step  406 . Alternatively, the access point  110  may set the length of the prefix  322  to zero.  
         [0035]     At step  408 , the access point  110  accumulates the TX data packets for transmission on a frame by frame basis according to rule of a scheme used. For example, a first scheme that requires an ACK before the next TX data packet is transmitted or an interlace transmission scheme that requires delaying transmission by one or more frame before transmitting the next TX data packet. At step  410 , the access point  110  transmits all the TX data packets, stored in step  408 , one per frame on the SDCH  244 . The step  410  is repeated until all the TX data packets, stored in memory are transmitted.  
         [0036]     Renumber figure references.  
         [0037]      FIG. 5A  shows a process  500  for evaluating data received on the shared channel SDCH  244  according to an embodiment. The steps of the process  500  are executed by the access terminal  120 , wherein the access terminal  120  is configured to use one or more components discussed in  FIG. 6 , for example, the controller  660 , RX Data Processor  656 , TX Data Processor  674 , etc. described below. Generally, information bits are continuously received on the shared channel SDCH  244 . At step  502 , the access terminal  120  receives information bits on SDCH  244 . In an embodiment, at step  504 , the access terminal  120  samples the received information and determines start of packet (e.g., the TX data packet associated with the first encoded data block of series  316 ). The access terminal  120  samples information bits, wherein the number information bits sampled is the size of prefix  322  and attempts to demodulate the sampled information bits using demodulation parameters. The demodulation parameters may be provided using various schemes, for example the demodulation parameters may have been provided when the access terminal  120  registered with the access point  110 . At step  506 , if the demodulation of the prefix  322  was successful, then the access terminal  120  executes step  508 . Otherwise, the access terminal  120  executes step  502  to continue evaluating additional information bits.  
         [0038]     At step  508 , the demodulated data extracted from prefix  322  are evaluated. The prefix  322  may provide several types of information (one or more tags), such as access terminal identification of the access terminal  120 , to indicate that the data following the prefix  322  is intended for the access terminal  120 . The prefix  322  may comprise one or more tags such as, a tag indicating how the packet was formed, a tag providing an indication of length of associated data, a tag providing an indication of the modulation scheme, a tag providing an indication that encoded data block  316   i  is present in the, a data rate tag, and one or more miscellaneous tags that provide information about the processing of the data associated with the prefix  322 .  
         [0039]     At step  510 , the access terminal  120  determines, using at least one of the tags provided in the prefix  322 , if the access terminal  120  currently processing the bits was the intended recipient of the TX data packet. If so, then at step  512 , the access terminal  120  processes the data associated with prefix  322  by extracting and demodulating the associated data using information provided by the prefix  322 . Otherwise, at step  514 , the access terminal  120  clears the data buffers and new information bits are sampled at step  502 . The information extracted from prefix  322  may be stored and later used for extracting and demodulating those TX data packets that do not have a prefix  322 .  
         [0040]      FIG. 5B  shows a process  550  for evaluating data received on the SDCH  244  according to another embodiment. The process  550  may be executed as a parallel process to process  500 , wherein the process  550  is processing information bits received on a second shared channel (not shown). The process  550  may also be executed by the access terminal  120  whenever the access point  110  is transmitting TX data packets without a prefix  322 . As stated above, generally, information bits are continuously received on the shared channel, at step  552 . At step  562 , the access terminal  120  samples received information. The sample size of the information bits is the size of the TX data packets. The size of TX data packets may be pre-stored in memory  662  or provided prior to the execution of step  552 . After sampling the data, the access terminal  120  attempts to demodulate (or decodes) sampled information to using demodulation information, such as packet size and/or demodulation parameters, to demodulate TX data packets. The demodulation parameters may also be provided upon the access terminal  120  upon registering with the access point  110 .  
         [0041]     At step  566 , the access terminal  120  attempts to decode the extracted encoded data block. At step  568 , if the attempted decoding is successful, then the access terminal  120  execute step  572  and processes the data.  
         [0042]     In another embodiment, if the system is capable of using two shared channels SDCHs, both, transmit process  300  and  400 ) and receive (process  500  and  550 ) techniques discussed above, may be employed concurrently. One shared channel may transmit data encoded with a prefix  322 , thus allowing smaller sampling and the second channel may transmit blocks of fix sizes, thus allowing quicker processing, especially for broadcast to large group of users.  
         [0043]      FIG. 6  shows a block diagram of an embodiment of an access point  110   x  and two terminals  120   x  and  120   y  in multiple-access multi-carrier communication system  100 . At access point  110   x , a transmit (TX) data processor  614  receives traffic data (i.e., information bits) from a data source  612  and signaling and other information from a controller  620  and a scheduler  630 . For example, controller  620  may execute the steps of process  400 , and scheduler  630  may provide assignments of carriers for the access terminals. These various types of data may be sent on different transport channels. TX data processor  614  encodes and modulates the received data using multi-carrier modulation (e.g., OFDM) to provide modulated data (e.g., OFDM symbols). A transmitter unit (TMTR)  616  then processes the modulated data to generate a downlink modulated signal that is then transmitted from an antenna  618 .  
         [0044]     At each of terminals  120   x  and  120   y , the transmitted and modulated signal is received by an antenna  652  and provided to a receiver unit (RCVR)  654 . Receiver unit  654  processes and digitizes the received signal to provide samples. A received (RX) data processor  656  then demodulates and decodes the samples to provide decoded data, which may include recovered traffic data, messages, signaling, and so on. The traffic data may be provided to a data sink  658 , and the carrier assignment and PC commands sent for the terminal are provided to a controller  660 .  
         [0045]     Controller  660  directs data transmission on the uplink using the specific carriers that have been assigned to the terminal and indicated in the received carrier assignment. In an embodiment, the controller  660  executes the steps of process  500  and  550 .  
         [0046]     For each active terminal  120 , a TX data processor  674  receives traffic data from a data source  672  and signaling and other information from controller  660 . For example, controller  660  may provide information indicative of the required transmit power, the maximum transmit power, or the difference between the maximum and required transmit powers for the terminal. The various types of data are coded and modulated by TX data processor  674  using the assigned carriers and further processed by a transmitter unit  676  to generate an uplink modulated signal that is then transmitted from antenna  652 .  
         [0047]     At access point  110   x , the transmitted and modulated signals from the terminals are received by antenna  618 , processed by a receiver unit  632 , and demodulated and decoded by an RX data processor  634 . Receiver unit  632  may estimate the received signal quality (e.g., the received signal-to-noise ratio (SNR)) for each terminal and provide this information to controller  620 . Controller  620  may then derive the PC commands for each terminal such that the received signal quality for the terminal is maintained within an acceptable range. RX data processor  634  provides the recovered feedback information (e.g., the required transmit power) for each terminal to controller  620  and scheduler  630 .  
         [0048]     Scheduler  630  uses the feedback information to perform a number of functions such as (1) selecting a set of terminals for data transmission on the reverse link and (2) assigning carriers to the selected terminals. The carrier assignments for the scheduled terminals are then transmitted on the forward link to these terminals.  
         [0049]     The techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units (e.g., controllers  620  and  670 , TX and RX processors  614  and  634 , and so on) for these techniques may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.  
         [0050]     For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units (e.g., memory  622  in  FIG. 6 ) and executed by processors (e.g., controllers  620 ). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.  
         [0051]     Headings are included herein for reference and to aid in locating certain sections. These headings are not intended to limit the scope of the concepts described therein under, and these concepts may have applicability in other sections throughout the entire specification.  
         [0052]     The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.  
         [0053]     What is claimed is: