Efficient frame quality indicator for a wireless signal decoder

• US 6,704,299 B1
• Filed: 11/30/1999
• Issued: 03/09/2004
• Est. Priority Date: 11/30/1999
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Li, Bin, Tong, Wen
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Swickhamer, Christopher M
• Application Number:
  US09/450,789
• Time in Patent Office: 1,561 Days
• Field of Search: 370/252, 370/331, 370/332, 375/340, 375/341, 375/343, 375/349, 375/150, 455/67.3, 455/442, 455/436, 714/819
• US Class Current: 370/332
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding

Abstract

A method and apparatus for generating a frame quality indication of a frame of a received turbo encoded wireless signal is provided. A turbo decoder is used to decode a demodulated frame and provide a decoded frame. A turbo encoder is used to encode the decoded frame to provide a re-encoded frame. A modulator modulates the re-encoded frame. The frame quality is assessed based on a degree of correlation between the demodulated frame and the re-encoded modulated frame. The advantages include a less complex receiver due to reduced computational load, and potentially greater payload capacity in frames due to elimination of Yamamoto bits.

Claims

1. A method of providing a frame quality indication for a received frame of a received, encoded wireless signal, the method comprising steps of:

a) demodulating the received frame;

b) decoding the demodulated frame using a decoder, the decoder being adapted to output a decoded frame;

c) encoding the decoded frame using an encoder matched to the decoder, the encoder being adapted to output a re-encoded frame;

d) modulating the re-coded frame to provide a re-modulated frame; and

e) providing the frame quality indication used to specify the reliability of the reception of the received frame based on a comparison between the received frame and the re-modulated frame.

2. A method as claimed in claim 1, wherein the encoded wireless signal is encoded using turbo coding techniques.

3. A method as claimed in claim 1, wherein the encoded wireless signal is encoded using Viterbi-convolutional coding techniques.

4. A method as claimed in claim 1, wherein a copy of the received frame is stored in a frame store pending correlation with the re-modulated frame.

5. A method as claimed in claim 1, wherein the comparison fixer comprises the step of:

a) correlating the received frame with the re-modulated frame and computing a correlation level.

6. A method as claimed in claim 5, wherein the step of providing the frame quality indication fixer comprises the step of:

a) comparing the correlation level against a threshold level, and;

i) accepting the frame if the frame quality indication is greater than or equal to the threshold level, and

ii) rejecting the frame if the correlation level is lower than the threshold level.

7. A method as claimed in claim 5, wherein the step of providing the frame quality indication further comprises the step of:

a) comparing the correlation level against a first and second threshold level, the first threshold level being greater than the second threshold level, and;

i) accepting the frame if the correlation level is greater than or equal to the first threshold level,

ii) rejecting the frame if the correlation level is less than the first threshold level and greater or equal to the second threshold level, and

iii) rejecting the frame if the correlation level is lower than the second threshold level.

8. A method of enabling soft handover of a wireless communication session between base stations, the method comprising the steps of:

a) decoding a demodulated frame provided by demodulation of a modulated frame of a received encoded wireless signal using a decoder, the decoder being adapted to output a decoded frame;

b) encoding the decoded frame using an encoder matched to the decoder, the encoder being adapted to output a re-encoded frame;

c) modulating the re-encoded frame to provide a re-modulated frame; and

d) selectively initiating a soft handover based on a frame quality indication used to specify a reliability of the reception of the received frame by determining a correlation level resulting from a correlation between the modulated frame and the re-modulated frame.

9. A method as claimed in claim 8, wherein a copy of the modulated frame is stored in a frame store pending correlation between the modulated frame and the re-modulated frame.

10. A method as claimed in claim 8, wherein the step of selectively initiating the soft handover further comprises the step of:

a) comparing the correlation level against a first and second threshold levels, the first threshold level being greater than the second threshold level;

i) suppressing soft handover if the correlation level is greater than or equal to the first threshold level,

ii) initiating the soft handover if the correlation level is lower than the first threshold level and greater or equal to the second threshold level, and

iii) performing the soft handover if the correlation level is lower than the second threshold level.

11. A method as claimed in claim 8, wherein the step of selectively initiating the soft handover further comprises the step of:

a) comparing the correlation level against a threshold level, and;

i) suppressing soft handover if the correlation level is greater than or equal to the threshold level, and

ii) initiating the soft handover and performing the soft handoff if the correlation level is less than the threshold level.

12. A method of decoding a frame of a received encoded wireless signal, the method comprising steps of:

a) demodulating the frame of the received signal to provide a demodulated frame;

b) decoding the demodulated frame using a decoder, the decoder being adapted to output a decoded frame;

c) encoding the decoded frame using an encoder matched to the decoder, the encoder being adapted to output a re-encoded frame;

d) modulating the re-encoded frame to provide a re-modulated frame; and

e) selectively accepting the decoded frame based on a frame quality indication used to specify the reliability of the received frame by determining a correlation level resulting from a correlation between the frame of the received signal and the re-modulated frame.

13. A method as claimed in claim 12, wherein the frame of the received signal is stored in a frame store pending correlation between the frame of the received signal and the re-modulated frame.

14. A method as claimed in claim 12, wherein the step of selectively discarding the decoded frame further comprises the step of:

a) comparing the correlation level against a threshold level, and;

i) accepting the decoded frame if the correlation level is greater than or equal to the threshold level, and

ii) discarding the decoded frame if the correlation level is less than the threshold level.

15. A receiver adapted to assess a frame quality indication of a modulated received frame of a received wireless signal, the receiver comprising:

a) a demodulator for demodulating the modulated receive frame to provide a demodulated received frame;

b) a decoder adapted to decode the demodulated received frame, the decoder outputting a decoded received frame;

c) an encoder matched to the decoder, the encoder being adapted to encode the decoded received frame, the encoder being further adapted to output a re-encoded frame;

d) a modulator for modulating the re-encoded frame to output a re-modulated frame;

e) a correlator adapted to correlate the modulated received frame with the re-modulated frame, the correlator being further adapted to output a correlation level; and

f) a decision circuit adapted to assess the frame quality indication used to specify the reliability of the demodulated received frame based on the correlation level.

16. A receiver as claimed in claim 15, wherein the receiver is a turbo coding receiver.

17. A receiver as claimed in claim 15, wherein the receiver is a Viterbi-convolutional coding receiver.

18. A receiver as claimed in claim 15, wherein the receiver further comprises:

a) a frame store adapted to retrievably store a copy of the demodulated frame for correlation with the re-modulated frame.

19. A receiver as claimed in claim 15, wherein the decision circuit further comprises:

a) a register adapted to hold a threshold level, whereby the fire is accepted if the correlation level is greater than or equal to the threshold level, and otherwise the frame is rejected.

20. A receiver as claimed in claim 15, wherein the decision circuit further comprises:

a) two registers adapted to hold a first threshold level and a second threshold level, respectively, the first threshold level being greater than the second threshold level, whereby the frame is accepted if the correlation level is greater than or equal to the first threshold level, and otherwise the frame is rejected.

21. A frame quality indication generator adapted to receive a modulated received frame of an encoded wireless signal and further adapted to receive a demodulated, decoded frame output by a decoder, the frame quality indication generator comprising:

a) an encoder matched to the decoder, the encoder being adapted to encode the demodulated, decoded frame and output a re-encoded frame;

b) a modulator adapted to modulate the re-encoded frame and output a re-modulated frame;

c) a correlator adapted to correlate the modulated received frame with the re-modulated frame and output a correlation level; and

d) a decision circuit adapted to assess the frame quality indication used to specify a reliability of the modulated received frame based on the correlation level.

22. A frame quality indication generator as claimed in claim 21, wherein the frame quality indication generator is a frame quality indication generator for a turbo coding receiver.

23. A frame quality indication generator as claimed in claim 21, wherein the frame quality indication generator is a frame quality indication generator for a Viterbi-convolutional coding receiver.

24. A frame quality indication generator as claimed in claim 21, wherein the frame quality indication generator further comprises a frame store adapted to retrievably store a copy of the modulated frame signal pending correlation with the re-modulated frame.

25. A frame quality indication generator as claimed in claim 21, wherein the decision circuit further comprises:

a) a register adapted to store a threshold level, whereby the frame is accepted if the correlation level is greater than or equal to the threshold level, and otherwise the frame is rejected.

26. A frame quality indication generator as claimed in claim 21, wherein the decision circuit further comprises:

a) two registers adapted to store a first threshold level and a second threshold level, respectively, the first threshold level being greater than the second threshold level, whereby the frame is accepted if the correlation level is greater than or equal to the first threshold level, and otherwise the frame is rejected.