High-data-rate wireless local-area network

• US 5,809,060 A
• Filed: 12/30/1994
• Issued: 09/15/1998
• Est. Priority Date: 02/17/1994
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Micrilor, Inc. (Proxim Corp.)
• Inventors: Fischer, Jeffrey H., Cafarella, John H.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kim, Kevin
• Application Number:
  US08/369,778
• Time in Patent Office: 1,355 Days
• Field of Search: 375/200, 375/205, 375/206, 375/207, 375/208, 375/209, 375/210, 375/279, 375/280, 375/281, 375/308, 375/330, 375/331, 370/18
• US Class Current: 375/146
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/711 the interference being multi-path interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/205 in which the data are represented by the change in phase of the carrier
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

An apparatus and method for communicating data between at least two data devices, suitable for use as a wireless local-area network, that provides robust data communication via a radio communications channel corrupted by multipath interference, particularly at high data rates. A preferred embodiment of the invention represents data as a sequence of Walsh-function waveforms encoded by pseudo-noise direct-sequence spread-spectrum modulation. Walsh-function-encoding of the data provides a long symbol duration, thereby allowing the spread-spectrum modulation to provide processing gain sufficient to substantially overcome multipath interference, while providing a high data rate. In another preferred embodiment, Walsh-function modulation is supplemented with various forms of phase modulation, such as coherent PSK for bi-orthogonal signalling, and DPSK between orthogonal symbols for noncoherent bi-orthogonal signalling, thereby further increasing data rate without reducing processing gain. In another preferred embodiment, Walsh-function modulation is supplemented with spectral shaping to allow increased bandwidth occupancy, thereby further increasing the processing gain without sacrificing data rate.

Claims

1. An apparatus for communicating data between at least two data devices, the apparatus comprising:

(a) means for acquiring data from a data device;

(b) means for representing the data as a sequence of digital waveform symbols, the digital waveform symbols being selected from a set that includes more than two unique digital waveform symbols each digital waveform symbol being characterized by a symbol duration, wherein each of the unique digital waveform symbols is orthogonal with respect to each other unique digital waveform symbol in the set, and further wherein the means for representing the data as a sequence of digital waveform symbols includes;

(I) means for grouping the data into a sequence of groups of N bits each, each group representing a symbol selected from 2^N possible data symbols; and

(ii) data modulation means for representing each data symbol as a digital waveform symbol so as to form the sequence of digital waveform symbols;

(c) means for generating a direct-sequence spread spectrum encoding signal;

(d) multiplying means for combining the direct-sequence spread spectrum encoding signal with the sequence of digital waveform symbols to provide a transmit signal;

(e) modulator means for modulating a carrier signal in accordance with the transmit signal to provide a modulated signal; and

(f) means for transmitting the modulated signal;

wherein said apparatus further includes (I) means for applying differential multiphase phase shift keying to each pair of sequentially neighboring waveform symbols so as to produce a waveform modulated by a combination of differential M-ary PSK and M-ary orthogonal function modulation; and

(ii) means for applying Reed-Solomon error correction coding to each waveform symbol, and means for applying binary error correction coding to the differential multiphase shift keying.

2. The apparatus of claim 1, wherein said means for representing the data represents said data in at least one coding block and said Reed-Solomon coding includes means for correcting only a single error in a coding block and binary coding comprising separate parity bits applied to even and odd groups of a differential bi-phase shift keying data.

3. An apparatus for communicating data between at least two data devices, the apparatus comprising:

(a) means for acquiring data from a data device;

(b) means for representing the data as a sequence of digital waveform symbols, the digital waveform symbols being selected from a set that includes more than two unique digital waveform symbols, each digital waveform symbol being characterized by a symbol duration, wherein each of the unique digital waveform symbols is orthogonal with respect to each other unique digital waveform symbol in the set, and further wherein the means for representing the data as a sequence of digital waveform symbols includes;

(I) means for grouping the data into a sequence of groups of N bits each, each group representing a symbol selected from 2^N possible data symbols; and

(ii) data modulation means for representing each data symbol as a digital waveform symbol so as to form the sequence of digital waveform symbols;

(c) means for generating a direct-sequence spread spectrum encoding signal;

(d) multiplying means for combining the direct-sequence spread spectrum encoding signal with the sequence of digital waveform symbols to provide a transmit signal;

(e) modulator means for modulating a carrier signal in accordance with the transmit signal to provide a modulated signal; and

(f) means for transmitting the modulated signal;

further including (I) means for applying multiphase phase shift keying to each waveform symbol so as to produce a waveform modulated by a combination of M-ary PSK and M-ary orthogonal function modulation;

(ii) means for applying Reed-Solomon error correction coding to each waveform symbol, and (iii) means for applying binary error correction coding to the multiphase phase shift keying.

4. An apparatus for communicating data between at least two data devices, the apparatus comprising:

(a) means for acquiring data from a data device;

(b) means for representing the data as a sequence of digital waveform symbols, the digital waveform symbols being selected from a set that includes more than two unique digital waveform symbols, each digital waveform symbol being characterized by a symbol duration, wherein each of the unique digital waveform symbols is orthogonal with respect to each other unique digital waveform symbol in the set, and further wherein the means for representing the data as a sequence of digital waveform symbols includes;

(I) means for grouping the data into a sequence of groups of N bits each, each group representing a symbol selected from 2^N possible data symbols; and

(ii) data modulation means for representing each data symbol as a digital waveform symbol so as to form the sequence of digital waveform symbols;

(c) means for generating a direct-sequence spread spectrum encoding signal;

(d) multiplying means for combining the direct-sequence spread spectrum encoding signal with the sequence of digital waveform symbols to provide a transmit signal;

(e) modulator means for modulating a carrier signal in accordance with the transmit signal to provide a modulated signal; and

(f) means for transmitting the modulated signal;

wherein the set of digital waveform symbols includes a set of Walsh-function waveforms, and said apparatus further includes means for applying Reed-Solomon error correction coding to each Walsh-function waveform.

5. The apparatus of claim 4, wherein said means for representing the data represents said data in at least one coding block, and said Reed-Solomon coding includes means for correcting only a single error in a coding block.

6. The apparatus of claim 5, further including means for using a coding block that is short enough such that the single error correcting will correct a sufficient number of errors in a data packet so that the packet failure rate will meet system specifications.

7. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms; and

wherein the despreading/correlation means includes;

means for direct-sequence despreading of a DSSS encoded signal so as to provide a despread signal;

means for bandpass filtering the despread signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms;

means for splitting the filtered signal into an in-phase signal and a quadrature signal;

means for converting the in-phase signal and the quadrature signal respectively into a digital in-phase signal and a digital quadrature signal;

Walsh-function demodulator means for correlating the digital signals with the Walsh-function waveforms so as to provide correlated in-phase signals and correlated quadrature signals; and

means for demodulating the correlated in-phase signals and the correlated quadrature signals so as to provide a plurality of envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of envelope signals so as to determine the largest magnitude envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude envelope signal so as to provide a binary data stream.

8. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein said data stream includes at least one data block, and said apparatus further includes means for using a Reed-Solomon error correction for correcting only a single error in a coding block.

9. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the despreading/correlation means further includes means for providing a largest complex amplitude signal, the most-likely symbol means further includes means for providing a largest magnitude index signal, and the apparatus further comprises;

means, responsive to the largest complex amplitude signal and to the largest magnitude index signal, for binary DPSK demodulating the sequence of received symbols.

10. The apparatus of claim 9, wherein the apparatus further includes:

means for Reed-Solomon error correction decoding and means for binary error decoding.

11. The apparatus of claim 10, wherein said data stream includes at least one data block, and said apparatus further includes means for using a Reed-Solomon error correction for correcting only a single error in a coding block and erasure decoding of the binary stream.

12. The apparatus of claim 11, wherein the erasure decoding includes means for using separate parity bits applied to the even and the odd groups of a differential bi-phase shift keying data for the correction.

13. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the despreading/correlation means also provides a largest complex amplitude signal, the most-likely symbol means further includes means for providing a largest magnitude index signal, and the apparatus further comprises;

means, responsive to the largest complex amplitude signal and to the largest magnitude index signal, for M-ary DPSK demodulation of the sequence of received symbols.

14. The apparatus of claim 13, wherein the apparatus further includes:

means for error correction decoding.

15. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms, and the despreading/correlation means includes;

means for bandpass filtering the incoming signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms with DSSS encoding;

means for splitting the filtered signal into an in-phase signal and a quadrature signal;

means for converting the in-phase signal and the quadrature signal respectively into an in-phase digital signal and a quadrature digital signal;

means for direct-sequence despreading each digital signal and correlating each digital signal with the Walsh-function waveforms so as to provide despread correlated in-phase signals and despread correlated quadrature signals; and

means for demodulating the despread correlated in-phase signals and the despread correlated quadrature signals so as to provide a plurality of envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of envelope signals so as to determine the largest magnitude envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude envelope signal so as to provide a binary data stream.

16. The apparatus of claim 15, wherein the despreading/correlation means further includes means for providing a largest complex amplitude signal, the most-likely symbol means further includes means for providing a largest magnitude index signal, and the apparatus further comprises:

means, responsive to the largest complex amplitude signal and to the largest magnitude index signal, for binary DPSK demodulating the sequence of received symbols.

17. The apparatus of claim 16, wherein the apparatus further includes:

means for Reed-Solomon error correction decoding and means for binary error decoding.

18. The apparatus of claim 17, wherein said data stream includes at least one data block, and said apparatus further includes means for using a Reed-Solomon error correction for correcting only a single error in a coding block and erasure decoding of the binary stream.

19. The apparatus of claim 18, wherein the erasure decoding includes means for using separate parity bits applied to the even and the odd groups of a differential bi-phase shift keying data for the correction.

20. The apparatus of claim 15, wherein the despreading/correlation means also provides a largest complex amplitude signal, the most-likely symbol means further includes means for providing a largest magnitude index signal, and the apparatus further comprises:

means, responsive to the largest complex amplitude signal and to the largest magnitude index signal, for M-ary DPSK demodulation of the sequence of received symbols.

21. The apparatus of claim 20, wherein the apparatus further includes:

means for error correction decoding.

22. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms, and wherein the despreading/correlation means includes;

a Walsh-function correlator, for receiving an input sample sequence, the correlator including a plurality of basic cells, each basic cell having an input and two outputs, the cells being interconnected to form a binary tree structure such that each possible path through the tree structure represents a unique function upon the input sequence, thereby providing a plurality of output sample sequences.

23. The apparatus of claim 22, wherein each basic cell accepts the input sample sequence serially at a first rate f_in, and generates first and second output sample sequences in parallel at a second rate f_in /2, such that the first output sample sequence includes the sum of a current serial pair of input samples of the input sample sequence, and the second output sample sequence includes the difference of the current serial pair of input samples of the input sample sequence, wherein each output sample sequence can be provided as an input sample sequence to another basic cell.

24. The apparatus of claim 22, wherein the tree structure is partitioned into a plurality of circuit segments for fabrication as a plurality of individual integrated circuit chips,

wherein each circuit segment includes an in-phase channel and a quadrature channel of at least a subset of the set of Walsh-function correlators disposed on the same integrated circuit chip, and

wherein each integrated circuit chip includes means for receiving output signals from a plurality of chips so as to perform a full set of Walsh-function correlations, thereby demodulating the received modulated signal.

25. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms, and the despreading/correlation means includes;

means for pseudonoise despreading of a DSSS encoded signal so as to provide a despread signal;

means for bandpass filtering the despread signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms;

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide an in-phase signal;

means for converting the in-phase signal into a digital in-phase signal;

Walsh-function demodulator means for correlating the digital signal with a set of Walsh-function waveforms so as to provide a plurality of correlated in-phase signals; and

means for demodulating the correlated in-phase signals so as to provide a plurality of in-phase envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of in-phase envelope signals so as to determine the largest magnitude in-phase envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude envelope signal so as to provide a binary data stream.

26. The apparatus of claim 25, the apparatus further comprising:

means, responsive to the largest magnitude envelope signal and to the largest magnitude index signal, for M-ary PSK demodulating the sequence of received symbols.

27. The apparatus of claim 26, further including means, responsive to the most-likely symbol means, for performing error correction decoding on the most-likely symbol if the most-likely symbol has been error-correction-encoded.

28. The apparatus of claim 25, the apparatus further comprising:

means, responsive to the largest magnitude envelope signal and to the largest magnitude index signal, for binary PSK demodulating the sequence of received symbols.

29. The apparatus of claim 28, wherein the means for converting the most-likely transmitted digital waveform symbol into a digital data sequence includes means for Reed-Solomon error correction decoding and means for binary error decoding.

30. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms, and the despreading/correlation means includes;

means for bandpass filtering the incoming signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms with DSSS encoding;

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide an in-phase signal;

means for converting the in-phase signal into an in-phase digital signal;

means for direct-sequence despreading the digital signal and correlating the digital signal with a Walsh-function waveform so as to provide a despread Walsh in-phase signal; and

means for envelope demodulating the despread Walsh in-phase signal so as to provide a plurality of envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of envelope signals so as to determine the largest magnitude envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude envelope signal so as to provide a binary data stream.

31. The apparatus of claim 30, the apparatus further comprising:

means, responsive to the largest magnitude envelope signal and to the largest magnitude index signal, for binary PSK demodulating the sequence of received symbols.

32. The apparatus of claim 31, wherein the means for converting the most-likely transmitted digital waveform symbol into a digital data sequence includes means for Reed-Solomon error correction decoding and means for binary error decoding.

33. The apparatus of claim 30, the apparatus further comprising:

means, responsive to the largest magnitude envelope signal and to the largest magnitude index signal, for M-ary PSK demodulating the sequence of received symbols.

34. The apparatus of claim 33, further including means, responsive to the most-likely symbol means, for performing error correction decoding on the most-likely symbol if the most-likely symbol has been error-correction-encoded.

35. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

further including a sliding serial-correlator-based synchronizer, having a signal detector, and being responsive to one of the plurality of despread correlation signals, for detecting the presence of the input signal;

a time-tracking loop, responsive to the most-likely symbol means, for extracting changes in timing information from at least one signal selected by the most-likely symbol means.

36. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the most-likely symbol means includes an M-way comparator having a plurality of two-way comparators interconnected as an inverted binary tree structure, each two-way comparator being adapted to provide an output amplitude that is the larger of two input amplitudes, and for providing an index of the larger of the two input amplitudes, the M-way comparator being adapted to provide an index indicating the largest of M input amplitudes, and to provide the largest amplitude of the M input amplitudes.

37. The apparatus of claim 36, wherein the inverted binary tree structure is partitioned into a plurality of circuit segments for fabrication as a plurality of individual integrated circuit chips,

wherein each circuit segment includes an in-phase channel and a quadrature channel of at least a subset of the set of Walsh-function correlators disposed on the same integrated circuit chip, and

wherein each integrated circuit chip includes means for receiving output signals from a plurality of chips so as to perform a full set of Walsh-function correlations, thereby demodulating the received modulated signal.

38. A method of receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible digital waveform symbols, wherein each digital waveform symbol in the set of possible digital waveform symbols is orthogonal with respect to each other digital waveform symbol in the set, and wherein the data are grouped into a sequence of groups of N bits each, each group representing a symbol from 2_N possible data symbols, and each data symbol is represented as a digital waveform symbol so as to form the sequence of digital waveform symbols, the method comprising the steps of:

receiving the modulated signal to provide an incoming signal;

providing a timing signal;

removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal;

correlating the incoming signal with each possible orthogonal digital waveform symbol of a set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

converting the most-likely transmitted digital waveform symbol into a digital data sequence so as to provide a digital data stream; and

providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms; and

the step of removing includes the steps of;

direct-sequence despreading of a DSSS encoded signal so as to provide a despread signal;

bandpass filtering the despread signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms;

splitting the filtered signal into an in-phase signal and a quadrature signal; and

converting the in-phase signal and the quadrature signal respectively into a digital in-phase signal and a digital quadrature signal,

wherein the step of correlating includes the steps of;

correlating each digital signal with a Walsh-function waveform so as to provide a in-phase signal and a quadrature signal; and

envelope demodulating the in-phase signal and the quadrature signal so as to provide a plurality of envelope signals,

wherein the step of receiving the plurality of despread correlation signals and determining therefrom a most-likely transmitted digital waveform symbol includes the steps of;

comparing each signal of the plurality of envelope signals so as to determine the largest magnitude envelope signal indicating a Walsh-function waveform most likely to have been transmitted; and

providing a largest magnitude index signal indicative of the largest magnitude envelope signal,

and wherein the step of converting includes the step of;

decoding the largest magnitude envelope signal so as to provide a binary data stream.

39. The method of claim 38, further comprising the step of:

M-ary DPSK demodulating the sequence of received symbols.

41. The method of claim 39, further comprising the step of:

M-ary DPSK demodulating the sequence of received symbols.

43. Apparatus according to claim 41, further including means for determining the polarity of the largest magnitude envelope signal.

44. Apparatus according to claim 41,

wherein the despreading/correlation means further includes:

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide a quadrature-phase signal;

means for converting the quadrature-phase signal into a digital quadrature-phase signal;

means for despreading one of said incoming, filtered, quadrature-phase and digital quadrature-phase signals resulting in a despread digital quadrature-phase signal following conversion of the quadrature-phase signal into a digital quadrature-phase signal;

Walsh-function demodulator means for correlating the despread digital quadrature-phase signal with a set of Walsh-function waveforms so as to provide correlated quadrature-phase signals; and

means for demodulating the correlated quadrature-phase signals so as to provide a plurality of quadrature-phase envelope signals; and

wherein the most-likely symbol means further includes;

means for comparing each signal of the plurality of quadrature-phase envelope signals so as to determine the largest magnitude quadrature-phase envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude quadrature-phase envelope signal

and wherein the means for converting further includes;

data decoder means for decoding the largest magnitude quadrature-phase envelope signal so as to provide a binary data stream.

45. Apparatus according to claim 43, further including means for determining the polarity of the largest magnitude in-phase envelope signal and for determining the largest magnitude quadrature-phase envelope signal.

46. The apparatus of claim 41, the apparatus further comprising:

means, responsive to the largest magnitude in-phase envelope signal and to the largest magnitude index signal, for M-ary PSK demodulating the sequence of received symbols.

47. The apparatus of claim 45, further including means, responsive to the most-likely symbol means, for performing error correction decoding on the most-likely symbol if the most-likely symbol has been error-correction-encoded.

48. The apparatus of claim 41, the apparatus further comprising:

means, responsive to the largest magnitude in-phase envelope signal and to the largest magnitude index signal, for binary PSK demodulating the sequence of received symbols.

49. The apparatus of claim 47, wherein the means for converting the most-likely transmitted digital waveform symbol into a digital data sequence includes means for Reed-Solomon error correction decoding and means for binary error decoding.

51. Apparatus according to claim 49, further including means for determining the polarity of the largest magnitude envelope signal.

52. Apparatus according to claim 49,

wherein the correlation means further includes:

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide a quadrature-phase signal;

means for converting the quadrature-phase signal into a digital quadrature-phase signal;

Walsh-function demodulator means for correlating the digital quadrature-phase signal with a set of Walsh-function waveforms encoded with direct-sequence spread spectrum encoding so as to provide correlated quadrature-phase signals; and

means for demodulating the correlated quadrature-phase signals so as to provide a plurality of quadrature-phase envelope signals; and

wherein the most-likely symbol means further includes;

means for comparing each signal of the plurality of quadrature-phase envelope signals so as to determine the largest magnitude quadrature-phase envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude quadrature-phase envelope signal

and wherein the means for converting further includes;

data decoder means for decoding the largest magnitude quadrature-phase envelope signal so as to provide a binary data stream.

53. Apparatus according to claim 51, further including means for determining the polarity of the largest magnitude in-phase envelope signal and for determining the largest magnitude quadrature-phase envelope signal.

54. The apparatus of claim 49, the apparatus further comprising:

means, responsive to the largest magnitude in-phase envelope signal and to the largest magnitude index signal, for M-ary PSK demodulating the sequence of received symbols.

55. The apparatus of claim 53, further including means, responsive to the most-likely symbol means, for performing error correction decoding on the most-likely symbol if the most-likely symbol has been error-correction-encoded.

56. The apparatus of claim 49, the apparatus further comprising:

means, responsive to the largest magnitude in-phase envelope signal and to the largest magnitude index signal, for binary PSK demodulating the sequence of received symbols.

57. The apparatus of claim 55, wherein the means for converting the most-likely transmitted digital waveform symbol into a digital data sequence includes means for Reed-Solomon error correction decoding and means for binary error decoding.

40. A method of receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible digital waveform symbols, wherein each digital waveform symbol in the set of possible digital waveform symbols is orthogonal with respect to each other digital waveform symbol in the set, and wherein the data are grouped into a sequence of groups of N bits each, each group representing a symbol from 2_N possible data symbols, and each data symbol is represented as a digital waveform symbol so as to form the sequence of digital waveform symbols, the method comprising the steps of:

receiving the modulated signal to provide an incoming signal;

providing a timing signal;

removing the pseudonoise direct-sequence spread spectrum encoding from the incoming signal;

correlating the incoming signal with each possible orthogonal digital waveform symbol of a set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

converting the most-likely transmitted digital waveform symbol into a digital data sequence so as to provide a digital data stream; and

providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes Walsh-function waveforms; and

the step of removing includes the steps of;

bandpass filtering the incoming so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms with DSSS encoding;

splitting the filtered signal into an in-phase signal and a quadrature signal;

converting the in-phase signal and the quadrature signal respectively into a digital in-phase signal and a digital quadrature signal; and

direct-sequence despreading each digital signal so as to provide a despread in-phase digital signal and a despread quadrature digital signal;

wherein the step of correlating includes the steps of;

correlating each digital signal with a Walsh-function waveform so as to provide a in-phase signal and a quadrature signal; and

envelope demodulating the in-phase signal and the quadrature signal so as to provide a plurality of envelope signals,

wherein the step of receiving the plurality of despread correlation signals and determining therefrom a most-likely transmitted digital waveform symbol includes the steps of;

comparing each signal of the plurality of envelope signals so as to determine the largest magnitude envelope signal indicating a Walsh-function waveform most likely to have been transmitted; and

providing a largest magnitude index signal indicative of the largest magnitude envelope signal,

and wherein the step of converting includes the step of;

decoding the largest magnitude envelope signal so as to provide a binary data stream.

42. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually-orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

despreading/correlation means, responsive to the timing signal and to the incoming signal, for both removing the direct-sequence spread spectrum encoding from the incoming signal, and for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of despread correlation signals;

most-likely symbol means for receiving the plurality of despread correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms, and the despreading/correlation means includes;

means for bandpass filtering the incoming signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms;

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide an in-phase signal;

means for converting the in-phase signal into a digital in-phase signal;

means for despreading one of said incoming, filtered, in-phase and digital in-phase signals resulting in a despread digital in-phase signal following conversion of the in-phase signal into a digital in-phase signal;

Walsh-function demodulator means for correlating the despread digital in-phase signal with a set of Walsh-function waveforms so as to provide correlated in-phase signals; and

means for demodulating the correlated in-phase signals so as to provide a plurality of in-phase envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of in-phase envelope signals so as to determine the largest magnitude in-phase envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude in-phase envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude in-phase envelope signal so as to provide a binary data stream.

50. Apparatus for receiving data communicated as a modulated signal between at least two data devices, the modulated signal being of the type encoded with direct-sequence spread spectrum encoding, and including digital waveform symbols selected from a set of possible mutually-orthogonal digital waveform symbols so that said data can be grouped into and conveyed as a sequence of groups of N bits each, the apparatus comprising:

means for receiving the modulated signal to provide an incoming signal;

means for providing a timing signal;

correlation means, responsive to the timing signal and to the incoming signal, for correlating the incoming signal with each possible digital waveform symbol of said set of possible digital waveform symbols so as to provide a plurality of correlation signals;

most-likely symbol means for receiving the plurality of correlation signals, and determining therefrom a most-likely transmitted digital waveform symbol so as to provide a sequence of received symbols;

means for converting the most-likely transmitted digital waveform symbol into a digital data bit sequence so as to provide a digital data stream; and

means for providing the digital data stream to a data device;

wherein the set of possible digital waveform symbols includes a set of Walsh-function waveforms encoded with direct-sequence spread spectrum encoding, and the correlation means includes;

means for bandpass filtering the incoming signal so as to provide a filtered signal having a bandwidth substantially similar to the bandwidth of the set of Walsh-function waveforms;

means for heterodyning to baseband the filtered signal with a coherent phase reference signal so as to provide an in-phase signal;

means for converting the in-phase signal into a digital in-phase signal;

Walsh-function demodulator means for correlating the digital in-phase signal with a set of Walsh-function waveforms encoded with direct-sequence spread spectrum encoding so as to provide correlated in-phase signals; and

means for demodulating the correlated in-phase signals so as to provide a plurality of in-phase envelope signals,

wherein the most-likely symbol means includes;

means for comparing each signal of the plurality of in-phase envelope signals so as to determine the largest magnitude in-phase envelope signal indicating a Walsh-function waveform most likely to have been transmitted, and for providing a largest magnitude index signal indicative of the largest magnitude in-phase envelope signal, and

wherein the means for converting includes;

data decoder means for decoding the largest magnitude in-phase envelope signal so as to provide a binary data stream.