Cooperative link characterization and MCS selection by wireless terminal and network for improved system performance

• US 7,107,013 B2
• Filed: 04/20/2004
• Issued: 09/12/2006
• Est. Priority Date: 06/16/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Qiu, Xiaoxin
• Primary Examiner(s): Anderson, Matthew D.
• Assistant Examiner(s): West, Lewis
• Application Number:
  US10/828,043
• Publication Number:
  US 20040253927A1
• Time in Patent Office: 875 Days
• Field of Search: 455/67.13, 455/67.11, 455/452.2, 455/69, 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 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• 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 1/1816 with retransmission of the same, encoded, message
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04L 1/1835 Buffer management
• CPC Class Codes: H04L 1/1845 Combining techniques, e.g. code combining
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 2025/03401 PSK
• CPC Class Codes: H04L 25/03318 Provision of soft decisions
• 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 downlink quality report and implement link adaptation decisions. This involves first implementing an initial transmission scheme between the servicing base station and the wireless terminal. Next, a current downlink quality report corresponding to the initial transmission scheme is generated by the wireless terminal and received at the servicing base station. This downlink quality report is based in whole or in part on a bit-error probability (BEP). The current downlink quality report that corresponds to the initial transmission scheme is then compared to link adaptation thresholds. When the current downlink quality report compares unfavorably to the link adaptation thresholds, an alternative transmission scheme is selected and implemented between the servicing base station and the wireless terminals if the alternative transmission scheme is expected to result in an improved downlink quality report over the current down-link quality report.

Claims

1. A method to select a transmission scheme for a radio frequency (RF) burst between a servicing base station and individual wireless terminals in a cellular wireless communication system, the method comprising:

implementing a first transmission scheme between the servicing base station and the wireless terminal;

receiving a first downlink quality report corresponding to the first transmission scheme at the servicing base station from the wireless terminal, wherein the downlink quality report comprises;

a bit error probability (BEP) based on a re-encoded bit error (RBER) of data within the RF bursts and an estimated BEP derived from a signal to noise ratio (SNR) of the RF burst;

a block error rate (BLER) of data within the RF bursts, wherein the BLER is derived from a bitmap reported by the wireless terminal;

a mean BLER determined by averaging together the BLER of each RF burst within a data frame; and

a standard deviation of the BLER within the data frame;

comparing the first downlink quality report corresponding to the first transmission scheme to at least one link adaptation threshold for individual wireless terminals;

implementing an alternative transmission scheme between the servicing base station and the wireless terminal when the first downlink quality report compares unfavorably to the at least one link adaptation threshold, and wherein the alternative transmission scheme is expected to result in an expected quality report being improved over the first downlink quality report; and

adjusting the at least one link adaptation threshold at the servicing base station for individual wireless terminals based on the downlink quality report.

2. The method of claim 1, wherein the wireless terminal determines the BEP based on:

an estimated BEP derived from the SNR of the RF burst when the data within the RF burst decoded unfavorably; and

the estimated BEP, the RBER, and/or BLER when the data within the RF burst decoded favorably.

3. The method of claim 2, wherein the SNR is derived from a training sequence within the RF burst.

4. The method of claim 2, wherein the SNR maps to the estimated BEP based on a modulation format of the RF bursts.

5. The method of claim 4, wherein the modulation format of the RF burst is GMSK or 8PSK.

6. The method of claim 1, wherein decoding unfavorably corresponds to the data within the RF burst having a measured bit error rate (BER) exceeding a predetermined threshold value, and wherein the estimated BEP considers the measured BER at the predetermined threshold value or greater.

7. The method of claim 6, wherein the predetermined threshold value is based on a Coding Scheme of the RF burst.

8. The method of claim 1, wherein adjusting the at least one link adaptation threshold at the servicing base station for individual wireless terminals based on the downlink quality report further comprises:

incrementing the at least one link adaptation threshold when an unfavorable downlink quality report is received at the servicing base station; and

decrementing the at least one link adaptation threshold when a favorable downlink quality report is received at the servicing base station.

9. The method of claim 8, wherein:

an unfavorable downlink quality report comprises an unfavorable comparison between the BLER and a BLER threshold; and

a favorable downlink quality report comprises a favorable comparison between the BLER and the BLER threshold.

10. The method of claim 1, further comprising dynamically selecting a transmission scheme for a radio frequency (RF) burst between a servicing base station and a wireless terminal in a cellular wireless communication system using the downlink quality report of the wireless terminal.

11. A cellular wireless communication system that comprises:

at least one servicing base station operable to select a transmission scheme for a radio frequency (RF) burst between the at least one servicing base station and at least one wireless terminal;

at least one wireless terminal operable to transmit a downlink quality report on the transmission scheme, wherein the downlink quality report comprises;

a bit error probability (BEP) based on a re-encoded bit error (RBER) of data within the RF burst and an estimated BEP derived from a signal to noise ratio (SNR) of the RF burst;

a block error rate (BLER) of data within the RF bursts, wherein the BLER is derived from a bitmap reported by the wireless terminal;

a mean BLER determined by averaging together the BLER of each RF burst within a data frame; and

a standard deviation of the BLER within the data frame

a link adaptation system operably coupled to the at least one servicing base station operable to;

compare the downlink quality report to at least one link adaptation threshold of the at least one wireless terminal;

implement an alternative transmission scheme between the at least one servicing base station and the at least one wireless terminal when the downlink quality report compares unfavorably to the at least one link adaptation threshold, and wherein the alternative transmission scheme is expected to result in an expected downlink quality report being improved over the downlink quality report; and

adjust the at least one link adaptation threshold at the servicing base station for individual wireless terminals based on the downlink quality report.

12. The cellular wireless communication system of claim 11, wherein the at least one wireless terminal determines the BEP based on:

an estimated BEP derived from the SNR of the RF burst when the data within the RF burst decoded unfavorably; and

the estimated BEP, the RBER, and or BLER when the data within the RF burst decoded favorably.

13. The cellular wireless communication system of claim 12, wherein the SNR is derived from a training sequence within the RF burst.

14. The cellular wireless communication system of claim 13, wherein the SNR maps to the estimated BEP based on a modulation format of the RF burst.

15. The cellular wireless communication system of claim 14, wherein the modulation format of the RF burst is GMSK or 8PSK.

16. The cellular wireless communication system of claim 11, wherein decoding unfavorably corresponds to the data within the RF burst having a measured bit error rate (BER) exceeding a predetermined threshold value, and wherein the estimated BEP considers the measured BER at the predetermined threshold value or greater.

17. The cellular wireless communication system of claim 16, wherein the predetermined threshold value is based on a Coding Scheme of the RF burst.

18. The cellular wireless communication system of claim 11, wherein:

the at least one link adaptation threshold is incremented when an unfavorable downlink quality report is received at the servicing base station; and

the at least one link adaptation threshold is decremented when a favorable downlink quality report is received at the servicing base station.

19. The cellular wireless communication system of claim 11, wherein the wireless terminal operates according to the GSM standard.

20. A method to dynamically select a transmission scheme for a radio frequency (RF) burst between a servicing base station and individual wireless terminals in a cellular wireless communication system, the method comprising:

implementing a first transmission scheme between the servicing base station and the wireless terminal;

receiving a first downlink quality report corresponding to the first transmission scheme at the servicing base station from the wireless terminal, wherein the downlink quality report comprises;

a block error rate (BLER) of data within the RF bursts;

a mean bit error probability (BEP) determined by averaging a BEP of each RF burst within a data frame; and

a standard deviation of the BEP within the data frame, wherein the BEP is based on an estimated BEP derived from a signal to noise ratio (SNR) of the RF burst and a re-encoded bit error (RBER), wherein;

the estimated BEP is weighed more heavily when data within RF burst is decoded unfavorably;

the RBER corresponds to a bit error rate (BER) exceeding a threshold value when data within RF burst is decoded unfavorably; and

the RBER is weighed more heavily when data within RF burst is decoded favorably/,

comparing the first downlink quality report corresponding to the first transmission scheme to at least one link adaptation threshold; and

implementing an alternative transmission scheme between the servicing base station and the wireless terminal when the downlink quality report compares unfavorably to the at least one link adaptation threshold, and wherein alternative transmission scheme is expected to result in an expected quality report being improved over the first downlink quality report; and

adjusting the at least one link adaptation threshold at the servicing base station for individual wireless terminals based on the downlink quality report.

21. The method of claim 20, wherein the SNR is derived from a training sequence within the RF burst.

22. The method of claim 21, wherein the transmission scheme comprises:

a coding scheme; and

a modulation format.

23. The method of claim 22, wherein the SNR maps to the estimated BEP based on a modulation format of the RF burst.

24. The method of claim 23, wherein the modulation format of the RF burst is GMSK or 8PSK.

25. The method of claim 20, wherein:

the at least one link adaptation threshold is incremented when an unfavorable downlink quality report is received at the servicing base station; and

the at least one link adaptation threshold is decremented when a favorable downlink quality report is received at the servicing base station.

26. The method of claim 20, wherein the wireless terminal operates according to the GSM standard.