Channel sounding for a spread-spectrum signal

• US 20010040878A1
• Filed: 07/19/2001
• Published: 11/15/2001
• Est. Priority Date: 01/14/1999
• Status: Active Grant

• Current Assignee: Aperture Net LLC (IP Edge LLC)
• Original Assignee: Linex Technologies, Inc.
• Inventors: Schilling, Donald L.
• Granted Patent: US 6,711,204 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence

Abstract

An improvement to a spread-spectrum code-division-multiple-access system, using a channel sounding signal from a base station (BS) to provide initial transmitter power levels for remote stations (RS). The base station has a BS-spread-spectrum transmitter for transmitting BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving RS-spread-spectrum signals at a second frequency. The RS-spread-spectrum signals are transmitted by the remote stations at the second frequency. The BS-spread-spectrum signals at the first frequency are outside the correlation bandwidth of the RS-spread-spectrum signals at the second frequency. The base station has a BS transmitter for transmitting a BS-channel-sounding signal at the same carrier frequency being used by the remote stations to transmit a spread-spectrum signal to the base station. The bandwidth of the BS-channel-sounding signal is much of the bandwidth of the BS-spread-spectrum signal. Each of the remote stations has an RS receiver, for receiving the BS-channel-sounding signal at the second frequency. Each RS receiver includes an RS demodulator for tracking the BS-channel-sounding signal and outputting an RS-receiver signal, and an RS-power-level circuit. In response to the RS-receiver signal, the RS-power-level circuit adjusts the initial RS-power level. The base station has an interference-reduction subsystem, located at a front end to the BS-spread-spectrum receiver. The interference-reduction subsystem reduces the BS-channel-sounding signal, transmitted from the base station, from the RS-spread-spectrum signal arriving at the base station.

Claims

1. An improvement to a spread-spectrum system having a base station and a plurality of remote stations (RS), with said base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at said base station, for transmitting a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having,

an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

a frequency-adjust circuit, coupled to said RS demodulator and responsive to the RS-receiver signal, for compensating to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station;

each of said plurality of remote stations including an RS-power-level circuit, responsive to the RS-receiver signal, for adjusting an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing, at the second frequency, the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

4. The improvement to the spread-spectrum system as set forth in

claim 1

,

2

or 3, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than ten percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

5. The improvement to the spread-spectrum system as set forth in

claim 1

,

2

or 3, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than five percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

6. The improvement to the spread-spectrum system as set forth in

claim 1

,

2

or 3, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than one percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

27. The method for improving the spread-spectrum system as set forth in

claim 1

,

2

or 3, with said interference-reduction subsystem including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

28. The method for improving the spread-spectrum system as set forth in

claim 4

, with said interference-reduction subsystem including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS- spread-spectrum signals.

29. The method for improving the spread-spectrum system as set forth in

claim 5

, with said interference-reduction subsystem including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

30. The method for improving the spread-spectrum system as set forth in

claim 6

, with said interference-reduction subsystem including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

2. An improvement to a spread-spectrum system having a base station and a plurality of remote stations (RS), with said base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at said base station, for transmitting, using radio waves, a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

each of said plurality of remote stations including an RS-power-level circuit, responsive to the RS-receiver signal, for adjusting an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

3. An improvement to a spread-spectrum system having a base station and a plurality of remote stations (RS), with said base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at said base station, for transmitting, using radio waves, a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having,

an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

a frequency-adjust circuit, coupled to said RS demodulator and responsive to the RS-receiver signal, for compensating to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

7. An improvement to a spread-spectrum system having a base station and a plurality of remote stations (RS), with said base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

BS-transmitter means, located at said base station, for transmitting, using radio waves, a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including RS-receiver means, for receiving the BS-channel-sounding signal at the second frequency, and for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

each of said plurality of remote stations including RS-power-level means, responsive to the RS-receiver signal, for adjusting an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

interference-reduction means, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

8. The improvement to the spread-spectrum system as set forth in

claim 7

, with said RS-receiver means at each of said plurality of remote stations further including compensating means, responsive to RS-receiver signal, for compensating to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station.

9. The improvement to the spread-spectrum system as set forth in

claim 7

or

8

, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than ten percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

10. The improvement to the spread-spectrum system as set forth in

claim 7

or

8

, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than five percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

11. The improvement to the spread-spectrum system as set forth in

claim 7

or

8

, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than one percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

31. The method for improving the spread-spectrum system as set forth in

claim 7

or

8

, with said interference-reduction means including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

32. The method for improving the spread-spectrum system as set forth in

claim 9

, with said interference-reduction means including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

33. The method for improving the spread-spectrum system as set forth in

claim 10

, with said interference-reduction means including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

34. The method for improving the spread-spectrum system as set forth in

claim 11

, with said interference-reduction means including a notch filter for notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

12. A method for improving a spread-spectrum system having a base station and a plurality of remote stations (RS), with said base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the method comprising the steps of:

transmitting, using radio waves, from a BS transmitter, located at said base station, a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

receiving, at each of said plurality of remote stations with an RS receiver, the BS-channel-sounding signal at the second frequency;

tracking, at each of said plurality of remote stations with an RS demodulator, a the BS-channel-sounding signal, thereby generating an RS-receiver signal;

adjusting, in response to the RS-receiver signal, an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

reducing the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

13. The method for improving the spread-spectrum system as set forth in

claim 12

, further including the step of compensating, in response to RS-receiver signal, to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station.

14. The method for improving the spread-spectrum system as set forth in

claim 12

or

13

, with the step of transmitting the BS-channel-sounding signal at the second frequency, including the step of transmitting the BS-channel-sounding signal with a bandwidth no more than ten percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

15. The method for improving the spread-spectrum system as set forth in

claim 12

or

13

, with the step of transmitting the BS-channel-sounding signal at the second frequency, including the step of transmitting the BS-channel-sounding signal with a bandwidth no more than one percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

16. The method for improving the spread-spectrum system as set forth in

claim 12

or

13

, with the step of transmitting the BS-channel-sounding signal at the second frequency, including the step of transmitting the BS-channel-sounding signal with a bandwidth no more than one percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

17. The method for improving the spread-spectrum system as set forth in

claim 12

or

13

, with the step of reducing the BS-channel-sounding signal further including the step of notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

18. The method for improving the spread-spectrum system as set forth in

claim 14

, with the step of reducing the BS-channel-sounding signal further including the step of notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

19. The method for improving the spread-spectrum system as set forth in

claim 15

, with the step of reducing the BS-channel-sounding signal further including the step of notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

20. The method for improving the spread-spectrum system as set forth in

claim 16

, with the step of reducing the BS-channel-sounding signal further including the step of notch filtering the BS-channel-sounding signal from the plurality of RS-spread-spectrum signals.

21. An improvement to a spread-spectrum system having a plurality of base stations covering a geographic area, with each base station communicating within a geographic cell with a plurality of remote stations (RS), with each base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at each base station, for transmitting a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal transmitted within a respective time slot assigned to the respective BS transmitter, and having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having,

an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

a frequency-adjust circuit, coupled to said RS demodulator and responsive to the RS-receiver signal, for compensating to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station;

each of said plurality of remote stations including an RS-power-level circuit, responsive to the RS-receiver signal, for adjusting an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing, at the second frequency, the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

24. The improvement to the spread-spectrum system as set forth in

claim 21

,

22

, or 23, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than ten percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

25. The improvement to the spread-spectrum system as set forth in

claim 21

,

22

, or 23, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than five percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

26. The improvement to the spread-spectrum system as set forth in

claim 21

,

22

, or 23, with said BS transmitter transmitting the BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal having a bandwidth no more than one percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals.

22. An improvement to a spread-spectrum system having a plurality of base stations covering a geographic area, with each base station communicating within a geographic cell with a plurality of remote stations (RS), with each base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at each base station, for transmitting a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal transmitted within a respective time slot assigned to the respective BS transmitter, and having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

each of said plurality of remote stations including an RS-power-level circuit, responsive to the RS-receiver signal, for adjusting an initial RS-power level of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing, at the second frequency, the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.

23. An improvement to a spread-spectrum system having a plurality of base stations covering a geographic area, with each base station communicating within a geographic cell with a plurality of remote stations (RS), with each base station (BS) having a BS-spread-spectrum transmitter for transmitting a plurality of BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving, at a second frequency, a plurality of RS-spread-spectrum signals from said plurality of remote stations, with the plurality of BS-spread-spectrum signals at the first frequency outside a correlation bandwidth of the plurality of RS-spread-spectrum signals at the second frequency, with each of said plurality of remote stations having an RS-spread-spectrum transmitter for transmitting an RS-spread-spectrum signal at the second frequency, the improvement comprising:

a BS transmitter, located at each base station, for transmitting a BS-channel-sounding signal at the second frequency, with the BS-channel-sounding signal transmitted within a respective time slot assigned to the respective BS transmitter, and having a bandwidth no more than twenty percent of the spread-spectrum bandwidth of the plurality of RS-spread-spectrum signals;

each of said plurality of remote stations including an RS receiver, for receiving the BS-channel-sounding signal at the second frequency, each RS receiver having,

an RS demodulator for tracking the BS-channel-sounding signal, thereby outputting an RS-receiver signal;

a frequency-adjust circuit, coupled to said RS demodulator and responsive to the RS-receiver signal, for compensating to the second frequency the RS-spread-spectrum signal of said RS-spread-spectrum transmitter located at said remote station; and

an interference-reduction subsystem, located at said base station and at a front end to said BS-spread-spectrum receiver, for reducing, at the second frequency, the BS-channel-sounding signal from the RS-spread-spectrum signal arriving at said base station.