Link quality prediction

• US 20070211641A1
• Filed: 03/13/2006
• Published: 09/13/2007
• Est. Priority Date: 03/13/2006
• Status: Active Grant

• Current Assignee: Novanta Inc.
• Original Assignee: TZero Technologies Incorporated (Novanta Inc.)
• Inventors: Chari, Sujai, Fu, Dengwei, Karnam, Mohan
• Granted Patent: US 7,440,412 B2
• Time in Patent Office: Days
• US Class Current: 370/241
• CPC Class Codes: H04B 1/71637 Receiver aspects H04B1/7183 takes precedence
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A method and apparatus of predicting link quality of a link is disclosed. The method includes receiving multi-carrier modulated signals over a period of time, estimating an SNR for each received sub-carrier, constructing a sequence of the SNRs, and estimating link PER based upon knowledge of encoding and/or interleaving used during transmission, and the sequence of SNRs.

Claims

1. A method of predicting link quality of a link, comprising:

receiving multi-carrier modulated signals over a period of time;

estimating an SNR for each received sub-carrier;

constructing a sequence of the SNRs;

estimating link PER based upon knowledge of encoding used during transmission and the sequence.

2. The method of claim 1, further comprising de-interleaving the sequence of SNRs based upon knowledge of transmission interleaving.

3. The method of claim 1, wherein estimating SNR for each received sub-carrier is based upon a transmission channel, noise variance and interference.

4. The method of claim 1, wherein the multi-carrier modulated signals are OFDM signals.

5. The method of claim 1, wherein estimating link PER is performed per packet.

6. The method of claim 5, further comprising:

estimating link PER of packets over time, and maintaining a running average of estimated link PER.

7. The method of claim 6, wherein length of the running average is based upon how rapidly the transmission channels are varying.

8. The method of claim 1, wherein the PER link estimate is made at a receiver of the multi-carrier modulated signals.

9. The method of claim 1, wherein the PER link estimate is made at a transmitter of the multi-carrier modulated signals based on feedback from a receiver of the multi-carrier modulated signals.

10. The method of claim 8, wherein at least one of the receiver and a transmitter comprises multiple receive antennas.

11. The method of claim 10, wherein the receiver comprises maximal ratio combining.

12. The method of claim 10, wherein the receiver comprises phase combining.

13. The method of claim 10, wherein the receiver comprises receive antenna select diversity.

14. The method of claim 1, wherein the encoding comprises forward error correction (FEC) coding at least one of convolutional, turbo and LDPC coding.

15. The method of claim 1, wherein estimating link PER based upon knowledge of encoding used during transmission, and the sequence comprises:

convolving the sequence with codewords, wherein the codewords are constructed based upon knowledge of the encoding at the transmitter;

generating a sequence of probability of error values by mapping each output of the convolution;

estimating link PER by summing the probability of error values.

16. The method of claim 15, wherein convolving the sequence with codewords comprises convolving the sequence with each codeword of a library of codewords.

17. The method of claim 15, wherein estimating PER further comprises scaling the estimate by a ratio of packet length to interleaver length.

18. The method of claim 1, wherein estimating link PER based upon knowledge of encoding used during transmission and the sequence comprises:

convolving the sequence with each codeword of a library of codewords, wherein the codewords are constructed based upon knowledge of the encoding at the transmitter;

generating a sequence of probability of error values by mapping each output of the convolution;

estimating link PER by summing the probability of error values.

19. A receiver comprising:

means for receiving multi-carrier modulated signals over a period of time;

means for estimating an SNR for each received sub-carrier;

means for constructing a sequence of the SNRs;

means for estimating link PER based upon knowledge of encoding used during transmission, and the sequence.

20. The receiver of claim 19, wherein the receiver feeds the estimated link PER back to a transmitter.

21. The receiver of claim 19, further comprising de-interleaving the sequence of SNRs based upon knowledge of transmission interleaving.

22. A method of selecting a transmission mode of a transmission link based on a predicted link quality of the link, comprising:

receiving multi-carrier modulated signals over a period of time;

estimating an SNR for each received sub-carrier;

constructing a sequence of the SNRs;

estimating link PER for all possible transmission modes based upon knowledge of encoding used during transmission and the sequence;

selecting a transmission mode based upon the link PER estimates.

23. The method of claim 22, wherein the mode that is selected is the mode that corresponds with the best PER estimate.

24. The method of claim 22, wherein the modes comprise at least one of multiple data transmission rates, multiple codes, multiple transmit antennas and multiple receive antennas.