Compensating for noise in a wireless communication system

• US 20070109995A1
• Filed: 10/23/2006
• Published: 05/17/2007
• Est. Priority Date: 10/30/1998
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chen, Feng, Denney, Lisa, Samueli, Henry, Lu, Fang, Jones, Christopher, Quigley, Thomas, Min, Jonathan, Nazareth, Sean
• Granted Patent: US 7,843,847 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04J 3/0655 using timestamps
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 2025/03808 Transmission of equaliser coefficients
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 41/142 using statistical or mathematical methods
• CPC Class Codes: H04L 5/003 Arrangements for allocating sub-channels of the transmission path
• CPC Class Codes: H04L 5/1446 of transmission speed
• CPC Class Codes: H04W 72/542 : using measured or perceived quality
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A number of features for enhancing the performance of a communication system, in which data is transmitted between a base station and a plurality of subscriber stations located different distances from the base station, are presented. The power transmission level, slot timing, and equalization of the subscriber stations are set by a ranging process. Data is transmitted by the subscriber stations in fragmented form. Various measures are taken to make transmission from the subscriber stations robust. The uplink data transmission is controlled to permit multiple access from the subscriber stations.

Claims

1. A base station that can receive signal bursts transmitted on an uplink channel of a wireless communication system, the base station comprising:

a demodulator for receiving the signal bursts on the uplink channel;

a media access controller (MAC) that generates for downlink transmission MAP messages that assign time slots in which subscriber stations may transmit signal bursts on the uplink channel, the MAP messages including idle slots that are assigned to no subscriber stations;

a transmitter that transmits the MAP messages with the idle slots to the subscriber stations; and

an adaptive notch filter connected to the demodulator, wherein coefficients of the adaptive notch filter are adjusted to suppress noise on the uplink channel sensed during the idle slots.

2. The base station of claim 1, further comprising a decision feedback equalizer coupled to the demodulator and the notch filter, the decision feedback equalizer having a feedback filter using the adjusted coefficients of the adaptive notch filter to compensate for distortion introduced by the adaptive notch filter.

3. The base station of claim 2, wherein the decision feedback equalizer has a feedforward filter for establishing pre-equalization coefficients.

4. The base station of claim 3, wherein the demodulator converts the signal bursts to binary data, the base station further comprising a signal path for carrying the binary data from the demodulator to the MAC, the notch filter and the decision feedback equalizer being in the signal path.

5. The base station of claim 4, wherein the signal path carries both the binary data and the pre-equalization coefficients to the MAC in band such that the coefficients are appended to the binary data.

6. The base station of claim 5, wherein the pre-equalization coefficients do not reflect noise received by the demodulator, the base station further comprising an uplink transmitter for transmitting the pre-equalization coefficients established by the feedforward filter.

7. The base station of claim 6, wherein the uplink transmitter is connected to the MAC to transmit the pre-equalization coefficients established by the feed forward filter.

8. A base station that can receive a signal transmitted in a wireless communication system on an uplink channel, the base station comprising:

a demodulator;

a notch filter connected to the demodulator, the notch filter having coefficients that are adjustable to cancel noise applied to the demodulator;

a media access controller (MAC) that processes binary data and generates for downlink transmission MAP messages that assign time slots in which subscriber stations may transmit signal bursts on the uplink channel; and

a decision feedback equalizer coupled to the demodulator, the decision feedback equalizer including a feedforward filter for establishing pre-equalization coefficients.

9. The base station of claim 8, wherein both binary data and pre-equalization coefficients are provided to the MAC in band such that the coefficients are appended to the binary data.

10. The base station of claim 9, wherein the pre-equalization coefficients do not reflect noise applied to the demodulator, the base station further comprising an uplink transmitter connected to the MAC to transmit the pre-equalization coefficients established by the feedforward filter.

11. A base station comprising:

means for transmitting on a downlink channel to a plurality of subscriber stations MAP messages that assign time slots in which subscriber stations may transmit signal bursts on an uplink channel, the MAP messages including idle slots that are assigned to no subscriber stations;

means for monitoring conditions on the uplink channel during the idle slots;

means for compensating for the monitored conditions on the uplink channel; and

means for receiving signal bursts on the uplink channel in response to such compensation.

12. The base station of claim 11, wherein the means for monitoring is configured to sense noise on the uplink channel during the idle slots.

13. The base station of claim 12, wherein the means for compensating is configured to adjust coefficients of a notch filter to compensate for the sensed noise on the uplink channel during the idle slots.

14. The base station of claim 13, wherein the means for compensating is further configured to adjust a feedback filter of a decision feedback filter in series with the notch filter to have the same coefficients as the notch filter to compensate for its distortion.

15. The base station of claim 14, wherein the means for compensating is further configured to adjust coefficients of a feedforward filter of the decision feedback filter based on a ranging signal of a subscriber station to compensate for intersymbol interference on the uplink channel;

and

wherein the means for transmitting is configured to transmit the adjusted coefficients on a downlink channel to the subscriber station for the purpose of pre-equalization.

16. The base station of claim 15, wherein the means for transmitting is configured to transmit the MAP messages and the adjusted coefficients on the same channel.

17. A base station comprising:

means for compensating for noise on an uplink channel;

means for receiving on the compensated uplink channel a ranging signal from a subscriber station of a plurality of subscriber stations;

means for adjusting filter coefficients to compensate for intersymbol interference on the uplink channel based on the received ranging signal; and

means for transmitting the adjusted coefficients on a downlink channel to the subscriber station for the purpose of pre-equalization of the uplink channel.

18. The base station of claim 17, wherein the means for adjusting is configured to adjust coefficients of a feedforward filter of a decision feedback filter.

19. The base station of claim 18, wherein the means for compensating is configured to adjust the coefficients of a notch filter in series with the decision feedback filter.

20. The base station of claim 19, wherein the means for compensating is further configured to adjust a feedback filter of the decision feedback filter to have the same coefficients as the notch filter to compensate for its distortion.

21. The base station of claim 20, wherein the means for transmitting is configured to transmit on a downlink channel to the subscriber stations MAP messages that assign time slots in which subscriber stations may transmit signal bursts on the uplink channel.

22. The base station of claim 21, wherein the means for transmitting is configured to transmit the MAP messages and the adjusted coefficients on the same channel.

23. In a wireless communication system, a subscriber station comprising:

a transmitter to transmit a ranging signal to a base station;

a receiver to receive pre-equalization coefficients from the base station, wherein the pre-equalization coefficients are based on the ranging signal; and

a transmit equalizer to compensate for noise associated with the subscriber station based on the pre-equalization coefficients.

24. The subscriber station of claim 23, wherein the pre-equalization coefficients represent frequency shaping necessary to compensate for the noise that is unique to the subscriber station.