Abstract:
A system and method are described for binding together a plurality of wireless data communications channels, whereby an aggregate throughput improvement is realized. A master channel amongst the channels to be bound is compatible with existing standards-based wireless data communications equipment. The master channel serves to perform MAC association and flow control. Aggregate throughput is improved by sending and receiving either multiple sets of separately encoded packets, commonly encoded packets or redundantly encoded packets.

Description:
FIELD OF THE INVENTION 
     The present invention relates to communication systems. More particularly, binding a plurality of communications channels to realize an aggregate throughput improvement is disclosed. The binding feature may be added in a manner that preserves compatibility with existing standards-based wireless data systems. 
     BACKGROUND OF THE INVENTION 
     Existing digital wireless communication systems communicate on a single RF channel, as shown by a prior-art standards-compliant client transceiver  120  in  FIG. 1 . Transceiver  120  receives and transmits digital data via data I/O  122 . This data is sent and/or received via antenna  124  to an access point  110  over a single data channel centered about a single RF frequency as illustrated by spectrum  140 . An example of such a standards-compliant client is the commercially-available Netgear model WG511 PCMCIA 802.11b/g wireless networking adaptor. 
     Although technological advances have increased the available digital throughput for any particular assigned frequency channel in a given band, there is always a desire to send data ever more rapidly or with greater integrity than can be accommodated with the single-channel approach. Thus, there is a need in the art for a method and apparatus for binding a plurality of data channels together to achieve aggregate throughput improvement including data rate and/or data integrity improvement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings. 
         FIG. 1  is a block diagram of a digital communication system showing a prior art communication channel and an advanced communication channel in some embodiments. 
         FIG. 2  is a diagram illustrating a spectrum broadcast. 
         FIGS. 3A-3C  are block diagrams illustrating digital communication system encoders. 
         FIG. 4  is a diagram illustrating a selectable band pass filter. 
     
    
    
     DETAILED DESCRIPTION 
     The invention can be implemented in numerous ways, including as a process, an apparatus, a system, a composition of matter, a computer readable medium such as a computer readable storage medium or a computer network wherein program instructions are sent over optical or electronic communication links. In this specification, these implementations, or any other form that the invention may take, are referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. 
     A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured. 
       FIG. 1  shows an access point transceiver  110  in digital wireless communication with both a client transceiver  120  according to existing digital data wireless standards and a client transceiver  130  according to bound channel communications techniques detailed herein. A single channel  140  is used to communicate between transceivers  110  and  120  while a plurality of bound channels  150  is used to communicated between transceivers  110  and  130 . The binding of multiple channels has the effect of improving aggregate throughput as will be described in detail herein. Multiple channels are considered bound if they are instantiated by a single association between advanced data transceivers. Multiple channels can be bound among multiple channels in a single band or multiple channels in multiple bands. Although any arrangement of channels can advantageously be used when bound, some channel arrangements have further advantages as will be detailed below. 
       FIG. 2  illustrates a comparison of the prior art spectrum  140  with a spectrum generated and received in one embodiment  152 . The spectrum  152  shows three adjacent, non-overlapping transmission channels wherein the center channel is designated the master channel  156 . The secondary channels  158 ,  159  occupy channels substantially equally above and below the master channel&#39;s center frequency. 
     This arrangement of channels is advantageous because when pairs of channels equally offset from a center frequency are operated contemporaneously, undesirable artifacts of the modulation of one channel upon a carrier are manifested in an equally but oppositely displaced, occupied channel. These artifacts might otherwise require expensive suppression to meet the requirements of, for example, the wireless data communications standard IEEE-802.11a. These artifacts are of less importance in prior-art single-channel systems or in the single master channel in some embodiments. 
       FIG. 3A  shows the interconnection of elements forming the data encoding and modulation portion of one embodiment. A software device driver receives and pre-processes data for transmission. The preprocessing performed by the device driver includes tagging data that can be transmitted by bound channels. An incoming data stream  301  is received by data distributor  300 . Data distributor  300  functions to detect tagged data and allocate streams of data to a plurality of encoding channels. Tags may be inserted into data stream  301  by the device driver. If data distributor  300  does not detect such tags, then all data is directed to master channel data stream  304 . If data distributor  300  does detect tags, then data is distributed among a plurality of data streams. In the embodiment shown, a multiplexer selectively feeds three buffers, which output data streams  302 ,  304  and  306 . Data streams  302 ,  304  and  306  are output to their respective packet generators  312 ,  314  and  316 . Data stream  304  is allocated to the master channel and streams  302  and  306  are allocated to secondary channels. In some embodiments, data distributor  300  allocates the data stream that requires the longest transmit time to the master channel and further distributes input stream data to data streams  302  and  306  such that their transmit times are substantially equal. 
     Packet generators  312 ,  314  and  316  packetize data in each channel in an appropriate manner. In some embodiments, packetizing is implemented as is described in the IEEE-802.11a standard. IFFT processors  322 ,  324  and  326  similarly process the packetized data into baseband encoded signals  323 ,  325  and  327 , respectively. Baseband signals  323  and  327  comprise the secondary channel signals and are up converted and down converted by complex carriers  332  and  335  respectively, carriers  332  and  335  having a frequency equal to the RF band channel spacing. Muxes  340 ,  342  and  344  allow selective passage of the baseband signals from each chain to summer  348 . The output of summer  348  feeds a digital baseband signal to analog converter (DAC)  350 . The baseband output of DAC  350  is mixed with a local oscillator signal  336  whose frequency places the output signal on a selected channel of a chosen RF band. 
     Packet generator  314  is associated with the master channel and generates beacons in a manner substantially as described by existing standards such as IEEE-802.11a. The beacon generation in the packet generators  312  and  316  associated with the secondary channels is disabled by the device driver in some embodiments. 
     Power amplifier  354  boosts the mixed signal to a level suitable for transmission. Selectable bandpass filter (BPF)  360  is, in one embodiment, set to a single-channel width when only the master channel is active and a three-channel width when two adjacent secondary channels are active. In a dual-band embodiment, power combiner  362  combines the output of power amplifier  352  and BPF  360  to feed antenna  114 . 
     The chain of processing from data stream  301  through the output of DAC  350  represents a baseband encoder chain. The chain of processing from the input of mixer  336  to the antenna  114  represents an upconverting transmitter chain. 
       FIG. 3B  shows the interconnection of elements forming the data encoding and modulation portion of another embodiment. Here, the three packet streams  323 ,  325  and  327  are generated as before. Now, however, they feed muxes  342 ,  340  and  344  directly. The outputs of the three muxes are connected to a 256-point IFFT block  370 . 256-point IFFT block  370  creates, in one processing step, an equivalent digital representation of three frequency-adjacent channels as from the output of summer  348 , above. The output of 256-point IFFT block  370  feeds DAC  350  and the remainder of the output chain (mixer  336 , PA  354  and BPF  360  connected to antenna  114 ) as in the previously-described embodiment. 
       FIG. 3C  shows the interconnection of elements forming the data encoding and modulation portion of yet another embodiment. Here, the three packet streams  323 ,  325  and  327  are generated from a common input data stream  301 . Muxes  342 ,  340  and  344  control packet data inputs to 256-point IFFT block  370 . In this manner, three frequency-adjacent channels of redundant data are created. The output of 256-point IFFT block  370  feeds DAC  350  and the remainder of the output chain (mixer  336 , PA  354  and BPF  360  connected to antenna  114 ) as in the previously-described embodiment. 
     Reception of bound streams is performed by hardware symmetric in function to the encoding described above; data is received on a master channel and one or more secondary channels, with data receivers replacing transmitters, FFT blocks replacing IFFT blocks and a data combiner replacing the data distributor. 
       FIG. 4  shows in block diagram and frequency spectrum form the use of the selectable bandpass filter (BFP)  360 . Select line  362  chooses either narrow or wide mode. In the embodiments above, the narrow setting imposes a single-channel-wide bandpass shape on the transmitted signal in order to attenuate spurious signals in adjacent channels when they are not in active use. When select line  362  chooses wide mode, the BPF  360  imposes a 3-channel-wide bandpass shape on the transmitted signal. In some embodiments, both filter bandpass shapes share a common center frequency. A coincident center frequency configuration is easier to design and manufacture. 
     When an access point transceiver and a client transceiver seek to communicate, the client, in accordance with existing standards and practice, would listen for a beacon signal from the access point and then enter into an exchange that establishes an association. An example of the association process is described in §11.3 of the IEEE-802.11-1999 standard. Various extensions of the association process allow for vendor-specific features to be advertised to and accepted by a client device (for example, Atheros Communications&#39; existing “Turbo Mode”). The channel binding feature is similarly treated as another form of vendor-specific extension to the association process. 
     The present invention has been described above in connection with a preferred embodiment thereof; however, this has been done for purposes of illustration only, and the invention is not so limited. Indeed, variations of the invention will be readily apparent to those skilled in the art and also fall within the scope of the invention. 
     Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive.