High-data-rate wireless local-area network

• US 6,473,449 B1
• Filed: 01/18/2000
• Issued: 10/29/2002
• Est. Priority Date: 02/17/1994
• Status: Expired due to Fees

• Current Assignee: Proxim Wireless Corporation
• Original Assignee: Proxim Inc. (Proxim Corp.)
• Inventors: Fischer, Jeffrey H., Cafarella, John H.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): AL BESHRAWI, TONY
• Application Number:
  US09/487,395
• Time in Patent Office: 1,015 Days
• Field of Search: 375/141, 375/200, 375/130, 370/471
• US Class Current: 375/141
• 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 13/0048 Walsh
• CPC Class Codes: H04J 13/102 Combining codes
• 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. A method of transmitting data through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, the method comprising the following:

(A) providing data as a sequence of digital waveform symbols with said DSSS code and with phase rotations of differential quadrature phase shift keying (DQPSK), wherein each digital waveform symbol (a) represents N data bits and (b) is selected from a set of at least 2^N possible digital waveform symbols, wherein at least some of the digital waveform symbols are orthogonal to one another;

wherein (i) each digital waveform symbol of the set is unique from the others, (ii) the symbol uniqueness is determined by a unique pulse structure, (iii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols defines a symbol modulation pulse width; and

(iv) the DQPSK relates to the phase shift between each pair of sequentially neighboring digital waveform symbols in said sequence;

(B) modulating a carrier signal as a function of the digital waveform symbols with said DSSS code and with the DQPSK phase rotations so as to produce a modulated signal; and

(C) amplifying and transmitting a radio signal as a function of the modulated signal;

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code.

2. The method according to claim 1, wherein the digital waveform symbols with said DSSS code without the DQPSK includes a quadrature component and an in-phase component.

3. The method according to claim 1, further including connecting the data device to a computer through an interface.

4. The method according to claim 1, wherein amplifying and transmitting a radio signal as a function of the modulated signal includes transmitting the radio signal through an antenna.

5. A method of transmitting data through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, the method comprising the following:

(A) providing data as a sequence of digital waveform symbols, wherein each digital waveform symbol (a) is selected from a set of at least 2^N digital waveform symbols, wherein at least some of the digital waveform symbols of the set are orthogonal to one another, and (b) represents N data bits, with each digital waveform symbol of the set being unique from the others, and (i) the symbol uniqueness being determined by a unique pulse structure and (ii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols defining a symbol modulation pulse width;

(B) applying differential quadrature phase shift keying (DQPSK) to each pair of sequentially neighboring digital waveform symbols of the sequence so as to produce a digital waveform symbol with one of four possible DQPSK phase rotations;

(C) combining (i) said DSSS code with (ii) the digital waveform symbols with the DQPSK phase rotations;

(D) modulating a carrier signal as a function of digital waveform symbols with the DSSS code and with the DQPSK phase rotations so as to produce a modulated signal; and

(E) amplifying and transmitting a radio signal as a function of the modulated signal;

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code.

6. The method according to claim 5, wherein each digital waveform symbol includes a quadrature component and an in-phase component.

7. The method according to claim 5, wherein the DSSS code includes a quadrature component and an in-phase component.

8. The method according to claim 7, wherein each digital waveform symbol includes a quadrature component and an in-phase component.

9. The method according to claim 5, further including connecting the data device to a computer through an interface.

10. The method according to claim 5, wherein amplifying and transmitting a radio signal as a function of the modulated signal includes transmitting the radio signal through an antenna.

11. A method of transmitting data through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, the method comprising the following:

(A) providing data as a sequence of digital waveform symbols with said DSSS code, wherein each digital waveform symbol with said DSSS code (a) is selected from a set of at least 2^N digital waveform symbols with said DSSS code, wherein at least some of the digital waveform symbols with said DSSS code of the set are orthogonal to one another, and (b) represents N data bits, with each digital waveform symbol of the set being unique from the others, and (i) the symbol uniqueness being determined by a unique pulse structure and (ii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols, in the absence of said DSSS code, defining a symbol modulation pulse width;

(B) applying one of four possible phase rotations of differential quadrature phase shift keying (DQPSK) to each pair of sequentially neighboring digital waveform symbols of the sequence with said DSSS code so as to produce a sequence of digital waveform symbols with said DSSS code and with DQPSK phase rotations;

(C) modulating a carrier signal as a function of digital waveform symbols with said DSSS code and with said DQPSK phase rotations so as to produce a modulated signal; and

(D) amplifying and transmitting a radio signal as a function of the modulated signal;

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code.

12. The method according to claim 11, wherein each digital waveform symbol with said DSSS code includes an in-phase component and a quadrature component.

13. The method according to claim 11, further including connecting the data device to a computer through an interface.

14. The method according to claim 11, wherein amplifying and transmitting a radio signal as a function of the modulated signal includes transmitting the radio signal through an antenna.

15. A method of transmitting data through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, the method comprising the following:

(A) providing data as a sequence of digital waveform symbols with any one of four differential quadrature phase shift keying (DQPSK) phase rotations between each pair of sequentially neighboring digital waveform symbols in said sequence, wherein each digital waveform symbol (a) is selected from a set of at least 2^N digital waveform symbols, at least some of the digital waveform symbols of the set being orthogonal to one another, and (b) represents N data bits, with each digital waveform symbol of the set being unique from the others, and (i) the symbol uniqueness being determined by a unique pulse structure and (ii) the shortest pulse width of the any of the digital waveform symbols in the set of digital waveform symbols defining a symbol modulation pulse width; and

(B) combining said DSSS code with the digital waveform symbols with said DQPSK phase rotations;

(C) modulating a carrier signal as a function of the digital waveform symbols with the DQPSK phase rotations and with the DSSS code so as to produce a modulated signal; and

(D) amplifying and transmitting a radio signal as a function of the modulated signal;

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code.

16. The method according to claim 15, wherein the digital waveform symbols without the DQPSK phase rotations each includes a quadrature component and an in-phase component.

17. The method according to claim 15, wherein the DSSS code includes a quadrature component and an in-phase component.

18. The method according to claim 17, wherein each digital waveform symbol without the DQPSK phase rotations includes a quadrature component and an in-phase component.

19. The method according to claim 15, further including connecting the data device to a computer through an interface.

20. The method according to claim 15, wherein amplifying and transmitting a radio signal as a function of the modulated signal includes transmitting the radio signal through an antenna.

21. A method of transmitting data through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, the method comprising the following:

(A) providing data as a sequence of digital waveform symbols, wherein each digital waveform symbol (a) occurs during the time of a symbol period, and (b) is selected from a set of at least 2^N digital waveform symbols, wherein at least some of the digital waveform symbols of the set are orthogonal to one another, and (c) represents N data bits, with each digital waveform symbol of the set being unique from the others, and (i) the symbol uniqueness being determined by a unique pulse structure and (ii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols defining a symbol modulation pulse width;

(B) differential quadrature phase shift keying (DQPSK) on the DSSS code in each pair of sequentially neighboring symbol periods;

(C) combining the sequence of digital waveform symbols with DSSS code after said differential quadrature phase shift keying (DQPSK) in each pair of sequentially neighboring symbol periods so as to produce a sequence of digital waveform symbols with said DSSS code and with DQPSK phase rotations;

(D) modulating a carrier signal as a function of the digital waveform symbols with the DSSS code and with the DQPSK phase rotations so as to produce a modulated signal; and

(E) amplifying and transmitting a radio signal as a function of the modulated signal;

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code.

22. The method according to claim 21, wherein each digital waveform symbol includes a quadrature component and an in-phase component.

23. The method according to claim 21, wherein the DSSS code without DQPSK on sequential symbol periods includes a quadrature component and an in-phase component.

24. The method according to claim 21, further including connecting the data device to a computer through an interface.

25. The method according to claim 21, wherein amplifying and transmitting a radio signal as a function of the modulated signal includes transmitting the radio signal through an antenna.

26. A method of receiving data transmitted through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, wherein data is transmitted as a sequence of digital waveform symbols with said DSSS code and with phase rotations of differential quadrature phase shift keying (DQPSK), wherein each of the digital waveform symbols is representative of N bits of data and is selected from a set of at least 2^N possible digital waveform symbols, at least some of the digital waveform symbols being orthogonal to one another;

wherein (i) each digital waveform symbol of the set is unique from the others, (ii) the symbol uniqueness is determined by a unique pulse structure, (iii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols defines a symbol modulation pulse width; and

(iv) the DQPSK relates to the phase shift between each pair of sequentially neighboring digital waveform symbols in said transmitted sequence; and

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code;

the method comprising the following;

receiving a radio signal from the common radio communication channel so as to provide an incoming signal as a function of the data transmitted through the communication channel and received by the data device;

correlating the incoming signal with said set of digital waveform symbols with said DSSS code so as to provide a first sequence of data bits representing a sequence of most likely transmitted digital waveform symbols;

providing a second sequence of data bits as a function of the differential phase shift between each pair of sequentially neighboring digital waveform symbols with said DSSS code in said transmitted sequence; and

converting the first and second sequence of data bits into a digital data bit sequence.

27. The method of claim 26, wherein each digital waveform symbol with DSSS code of said set includes an in-phase component and a quadrature component, and wherein the step of correlating the incoming signal includes correlating the incoming signal with the in-phase component and quadrature component of each digital waveform symbol with DSSS code of said set so as to provide a sequence of data bits representing a sequence of most likely transmitted complex digital waveform symbols.

28. The method of claim 26, wherein the step of receiving includes using an antenna to receive a radio signal from the common radio communication channel from any other data device connected to the network.

29. The method of claim 26, further including connecting the data device to a computer through a computer interface.

30. The method of claim 26, further including connecting the data device to a data interface.

31. The method of claim 26, further including connecting the data device to a printer.

32. The method of claim 26, further including connecting the data device to a mass data storage device.

33. The method of claim 32, wherein the mass data storage device is a file server.

34. The method of claim 26, further including connecting the data device to an antenna, band pass filter and a down converting stage.

35. A method of receiving data transmitted through a common radio communications channel forming a wireless connection between any two data devices of a local area network comprising a plurality of such data devices, wherein each data device (i) uses the same direct-sequence spread spectrum (DSSS) code of a known chip width and (ii) uses spread spectrum processing gain so as to suppress unknown interference signals and unknown multipath signals, wherein data is transmitted as a sequence of digital waveform symbols with said DSSS code and with phase rotations of differential quadrature phase shift keying (DQPSK), wherein each of the digital waveform symbols is representative of N bits of data and is selected from a set of at least 2^N possible digital waveform symbols, at least some of the digital waveform symbols being orthogonal to one another;

wherein (i) each digital waveform symbol of the set is unique from the others, (ii) the symbol uniqueness is determined by a unique pulse structure, (iii) the shortest pulse width of any of the digital waveform symbols in the set of digital waveform symbols defines a symbol modulation pulse width; and

(iv) the DQPSK relates to the phase shift between each pair of sequentially neighboring digital waveform symbols in said transmitted sequence; and

wherein the known chip width of said DSSS code is equal to the symbol modulation pulse width of the set of digital waveform symbols in the absence of the DSSS code;

the method comprising the following;

receiving a radio signal from the common radio communication channel so as to provide an incoming signal as a function of the data transmitted through the communication channel and received by the data device; and

performing each of the following;

(i) removing the DSSS code, (ii) correlating with digital waveform symbols of the set, and (iii) determining the phase shift between each pair of sequentially neighboring digital waveform symbols in said transmitted sequence, so as to provide a digital data bit sequence as a function of the most likely transmitted digital waveform symbols and the phase shift between each pair of sequentially neighboring digital waveform symbols in said transmitted sequence.

36. The method of claim 35, wherein each digital waveform symbol of said set includes an in-phase component and a quadrature component, and wherein the step of correlating with digital waveform symbols of the set includes correlating with the in-phase component and quadrature component of each digital waveform symbol of said set so as to provide a sequence of data bits representing a sequence of most likely transmitted complex digital waveform symbols.

37. The method of claim 35, wherein the step of receiving includes using an antenna to receive a radio signal from the common radio communication channel from any other data device connected to the network.

38. The method of claim 35, further including connecting the data device to a computer through a computer interface.

39. The method of claim 35, further including connecting the data device to a data interface.

40. The method of claim 35, further including connecting the data device to a printer.

41. The method of claim 35, further including connecting the data device to a mass data storage device.

42. The method of claim 41, wherein the mass data storage device is a file server.

43. The method of claim 35, further including connecting the data device to an antenna, band pass filter and a down converting stage.