Adaptive channel quality estimation algorithm to support link adaptation

• US 7,203,461 B2
• Filed: 05/14/2004
• Issued: 04/10/2007
• Est. Priority Date: 06/16/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Wang, Yongqian, Chang, Li Fung, Sollenberger, Nelson R., Qiu, Xiaoxin
• Primary Examiner(s): Milord; Marceau
• Application Number:
  US10/845,955
• Publication Number:
  US 20040253968A1
• Time in Patent Office: 1,061 Days
• Field of Search: 455/63.1, 455/67.11, 455/522, 455/67.13, 455/277.2, 455/69, 455/452.2, 375/264
• US Class Current: 455/67.13
• 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 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/0075 Transmission of coding parameters to receiver H04L1/0023 takes precedence
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 1/206 for modulated signals
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178

Abstract

RF communications received by a wireless terminal from a servicing base station are used to determine the channel quality such as reported bit error probability (BEP). The RF communications may be in the form of RF bursts that are part of a data frame. An estimated BEP may be determined from the signal to noise ratio (SNR) of the RF bursts and or a sequence of soft decisions extracted from the RF bursts, and their historical performance. The SNR maps to an estimated BEP based upon the modulation format of the RF bursts. The soft decisions decode to produce a data block. When the soft decisions decoded favorably, the re-encoded data block produces a sequence of re-encoded decisions. Comparing the re-encoded decisions to the soft decisions yields a re-encoded bit error (RBER). The reported BEP may be based upon the estimated BEP, RBER, and/or RBER threshold. The RBER threshold may be adaptively incremented or decremented depending upon whether or not the RF communications were properly decoded. The size of the increment or decrement may be based on the channel quality.

Claims

1. A method to determine a channel quality, as represented by a current bit error probability (BEP) for radio frequency (RF) bursts transmitted from a servicing base station to a wireless terminal in a cellular wireless communication system, the method comprising:

receiving the RF bursts by the wireless terminal wherein the RF bursts are transmitted according to a transmission scheme;

forming a data block from the RF bursts;

decoding the data block;

determining whether decoding of the data block was successful;

determining a measured quality report for the data block;

when decoding is unsuccessful;

setting the current BEP to a weighted sum of the estimated quality report and a quality report threshold; and

incrementing the quality report threshold by an increment step size until an upper quality report threshold limit is reached;

when decoding is successful;

setting the current BEP to the measured quality report; and

decrementing the quality report threshold by a decrement step size until a lower quality report threshold limit is reached.

2. The method of claim 1, wherein the current quality report comprises a current BEP report;

the estimated quality report comprises an estimated BEP derived from SNR;

the quality report threshold comprises a Re-encoded Bit Error Rate (RBER) threshold; and

the measured quality report comprises a RBER based on re-encoding the data block.

3. The method of claim 2, wherein an updated quality report to be sent to the network is determined based upon both the current quality report and at least one prior quality report.

4. The method of claim 3, wherein the weighted sum of the estimated quality report and quality report threshold is based on a channel quality measure.

5. The method of claim 4, wherein the increment step size and decrement step size are based on a channel quality measure.

6. The method of claim 4, wherein the channel quality measure comprises a block error report (BLER).

7. The method of claim 4, wherein the transmission scheme comprises:

a coding scheme; and

a modulation format.

8. The method of claim 7, wherein the SNR maps to the estimated BEP based upon the modulation scheme of the RF burst.

9. The method of claim 7, wherein the modulation format of the RF burst is GMSK or 8PSK.

10. The method of claim 7, wherein the RBER threshold is based on a modulation and coding Scheme of the RF bursts.

11. The method of claim 1, wherein the wireless terminal operates according to the GSM standard.

12. The method of claim 1, further comprising the servicing base station selecting a transmission scheme for the wireless terminal using the updated BEP.

13. A wireless terminal that comprises:

a Radio Frequency (RF) front end;

a baseband processor communicatively coupled to the RF front end;

an enCOder/DECoder (CODEC) processing module communicatively coupled to the baseband processor;

wherein, the RF front end, the baseband processor, and the CODEC processing module are operable to;

receive RF bursts transmitted according to a transmission scheme;

form a data block from the RF bursts;

decode the data block;

determine whether decoding of the data block was successful;

determine a current quality report for the data block;

when decoding is unsuccessful;

set the current quality report to a weighted sum of the estimated quality report and a quality report threshold; and

increment the quality report threshold by an increment step size until an upper quality report threshold limit is reached;

when decoding is successful;

set the current quality report to the measured quality report; and

decrement the quality report threshold by a decrement step size until a lower quality report threshold limit is reached.

14. The wireless terminal of claim 13, wherein the current quality report comprises a current BEP report;

the estimated quality report comprises an estimated BEP derived from SNR;

the quality report threshold comprises a Re-encoded Bit Error Rate (RBER) threshold; and

the measured quality report comprises a RBER based on re-encoding the data block.

15. The wireless terminal of claim 14, wherein an updated quality report to be sent to the network is determined based upon both the estimated quality report and at least one prior quality report.

16. The wireless terminal of claim 15, wherein the weighted sum of the estimated quality report and quality report threshold is based on a channel quality measure.

17. The wireless terminal of claim 16, wherein the increment step size and decrement step size are based on a channel quality measure.

18. The wireless terminal of claim 17, wherein channel quality measure comprises a block error report (BLER).

19. The wireless terminal of claim 17, wherein the RBER is determined based upon re-encoded data and soft decisions of the data block.

20. The wireless terminal of claim 17, wherein the transmission scheme comprises:

a coding scheme; and

a modulation format.

21. The wireless terminal of claim 20, wherein the SNR maps to the estimated BEP based on the modulation format of the RF bursts.

22. The wireless terminal of claim 20, wherein the modulation format of the RF burst is GMSK or 8PSK.

23. The wireless terminal of claim 20, wherein the RBER threshold is based on a Modulation and Coding Scheme of the RF bursts.

24. The wireless terminal of claim 14, wherein the wireless terminal operates according to the GSM standard.

25. The wireless terminal of claim 14, wherein the wireless terminal provides the averaged BEP to a servicing base station, and wherein the servicing base station selects a transmission scheme for the RF bursts based on the updated BEP.

26. A method to determine a reported bit error probability (BEP) for radio frequency (RF) bursts transmitted from a servicing base station to a wireless terminal in a cellular wireless communication system, the method comprising:

receiving the RF bursts by the wireless terminal wherein the RF bursts are transmitted according to a transmission scheme;

forming a data block from the RF bursts;

decoding the data block;

determining whether decoding of the data block was successful;

determining a current BEP for the data block;

when decoding is unsuccessful, setting the reported BEP to a maximum of the estimated BEP and a Re-encoded Bit Error Rate (RBER) threshold, and further incrementing the RBER threshold by a increment step size until an upper quality report threshold limit is reached; and

when decoding is successful, setting the reported BEP to the RBER and decrementing the RBER threshold by a decrement step size until a lower quality report threshold limit is reached.

27. The method of claim 26, wherein an updated BEP reported to the servicing base station is determined based upon both the current data block and at least one prior data block.

28. The method of claim 27, wherein the wireless terminal determines the estimated BEP based on the SNR of the RF bursts when the data within the data block decodes unsuccessfully.

29. The method of claim 28, wherein the SNR is derived from training sequences of the RF bursts.

30. The method of claim 28, wherein the RBER is determined based upon re-encoded data and soft decisions of the data block.

31. The method of claim 28, wherein the transmission scheme comprises:

a coding scheme; and

a modulation format.

32. The method of claim 31, wherein the SNR maps to the estimated BEP based upon the modulation scheme of the RF burst.

33. The method of claim 31, wherein the modulation format of the RF burst is GMSK or 8PSK.

34. The method of claim 31, wherein an initial RBER threshold is based on a Modulation and Coding Scheme of the RF bursts.

35. The method of claim 26, wherein the wireless terminal operates according to the GSM standard.

36. The method of claim 26, further comprising the servicing base station selecting a transmission scheme for the wireless terminal using the updated BEP.