Adaptive weight update method and system for a discrete multitone spread spectrum communications system

• US 6,975,668 B2
• Filed: 11/15/2001
• Issued: 12/13/2005
• Est. Priority Date: 02/24/1997
• Status: Expired due to Fees

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: Cingular Wireless II LLC (AT&T, Inc.)
• Inventors: Zhang, Hongliang
• Primary Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US09/999,048
• Publication Number:
  US 20020034217A1
• Time in Patent Office: 1,489 Days
• Field of Search: 375/147, 375/148, 375/130, 375/132, 375/133, 375/138, 375/140, 375/211, 375/219, 375/224, 375/232, 375/260, 375/347, 370/203, 370/208, 370/252, 370/280, 370/294, 370/320, 370/335, 370/342, 370/441, 370/479, 455/132, 455/133, 455/135, 455/136, 455/67.3, 455/272, 455/422, 455/424, 714/704, 714/708, 708/322, 708/323
• US Class Current: 375/140
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/0848 Joint weighting
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0026 Division using four or more dimensions
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/026 using code division

Abstract

A new method makes the most efficient use of the scarce spectral bandwidth in a wireless discrete multitone spread spectrum communications system by updating the spectral and/or spatial spreading weights at a rate that is determined by the measured quality of the link. Low quality links require more frequent updates of the spreading weights than do higher quality links. Spreading weights and despreading weights for a station are adaptively updated, depending on the error in received signals. If the error value is less than a threshold error value, then the method maintains the existing spreading weights as the current spreading weights to apply to an outgoing data signal. Alternately, if the error value is greater than the threshold error value, then the method adaptively calculates updated despreading weights at the base station from the first spread signal and calculates updated spreading weights as the current spreading weights from the updated despreading weights to apply to the outgoing data signal.

Claims

1. A highly bandwidth-efficient communications method, comprising:

receiving at a base station a new incoming spread signal comprising an incoming data signal spread over a plurality of discrete frequencies;

accessing a stored error value for a previously received spread signal;

comparing the stored error value with a threshold error value;

if the stored error value is less than the threshold error value, then maintaining existing despreading and spreading weights as current spreading weights at the base station to apply to the new incoming signal and a next outgoing data signal;

alternately, if the stored error value is greater than the threshold error value, then adaptively calculating new despreading weights at the base station from the new incoming spread signal and calculating new spreading weights from the new despreading weights to apply to the new incoming signal and the next outgoing data signal;

despreading the new incoming signal;

computing and storing a new error value for the new incoming signal; and

spreading the next outgoing data signal to distribute the outgoing data signal over a plurality of discrete tones.

2. The highly bandwidth-efficient communications method of claim 1, that further comprises:

the stored error value for the previously received spread signal being a bit error rate.

3. The highly bandwidth-efficient communications method of claim 1, that further comprises:

the stored error value for the previously received spread signal being a Reed-Solomon error value.

4. The highly bandwidth-efficient communications method of claim 1, that further comprises:

the stored error value for the previously received spread signal being a difference value between the previously received spread signal and a reference signal at the base station.

5. The highly bandwidth-efficient communications method of claim 1, that further comprises:

the stored error value for the previously received spread signal being a mean square error value.

6. The highly bandwidth-efficient communications method of claim 1, that further comprises:

the threshold error value being a limit error value less a margin error value.

7. A highly bandwidth-efficient communications system, comprising:

means for receiving at a base station a new incoming spread signal comprising an incoming data signal spread over a plurality of discrete frequencies;

means for accessing a stored error value for a previously received spread signal;

means for comparing the stored error value with a threshold error value;

means for maintaining existing despreading and spreading weights as current spreading weights at the base station to apply to the new incoming signal and a next outgoing data signal, if the stored error value is less than the threshold error value;

means for adaptively calculating new despreading weights at the base station from the new incoming spread signal and calculating new spreading weights from the new despreading weights to apply to the new incoming signal and the next outgoing data signal, if the stored error value is greater than the threshold error value;

means for despreading the new incoming signal;

means for computing and storing a new error value for the new incoming signal; and

means for spreading the next outgoing data signal to distribute the outgoing data signal over a plurality of discrete tones.

8. The highly bandwidth-effective communications system of claim 7, wherein the stored error value for the previously received spread signal is a bit error rate.

9. The highly bandwidth-effective communications system of claim 7, wherein the stored error value for the previously received spread signal is a Reed-Solomon error value.

10. The highly bandwidth-effective communications system of claim 7, wherein the stored error value for the previously received spread signal is a difference value between the previously received spread signal and a reference signal at the base station.

11. The highly bandwidth-effective communications system of claim 7, wherein the stored error value for the previously received spread signal is a mean square error value.

12. The highly bandwidth-effective communications system of claim 7, wherein the threshold error value is a limit error value less than a margin error value.