Link adaptation of a broadcast system

• US 20090154388A1
• Filed: 12/14/2007
• Published: 06/18/2009
• Est. Priority Date: 12/14/2007
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Beceem Communications, Inc. (Broadcom, Inc.)
• Inventors: Medepalli, Kamesh, Jalloul, Louay, Mudulodu, Sriram, Tujkovic, Djordje
• Granted Patent: US 8,654,695 B2
• Time in Patent Office: Days
• US Class Current: 370/312
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0019 in which mode-switching is based on a statistical approach
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0027 Scheduling of signalling, e.g. occurrence thereof
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint

Abstract

A method and apparatus of link adaptation of a broadcast system is disclosed. The method includes a base station adaptively determining a signal quality threshold. The base station broadcasts a signal, wherein the signal includes the signal quality threshold. A plurality of subscribers receives the signal, and measure a signal quality. Each of a subset of the plurality of subscribers transmits back to the base station an indicator of whether the received signal has a measured signal quality that is either above or below the signal quality threshold. A percentage of subscribers that receive the signal having a received signal quality above the signal quality threshold is estimated. A transmission modulation format and coding is selected based on the estimated percentage.

Claims

1. A method of link adaptation of a broadcast system, comprising:

a base station adaptively determining a signal quality threshold;

the base station broadcasting a signal, wherein the signal comprises the signal quality threshold;

a plurality of subscribers receiving the signal, and measuring a signal quality;

each of a subset of the plurality of subscribers transmitting back to the base station an indicator of whether the received signal has a measured signal quality that is one of above or below the signal quality threshold;

estimating a percentage of subscribers that receive the signal having a received signal quality above the signal quality threshold; and

selecting a transmission modulation format and coding based on the estimated percentage.

2. The method of claim 1, further comprising adaptively determining the signal quality threshold based on the estimated percentage.

3. The method of claim 1, further comprising the base station including a probe packet within the broadcast signal, the probe packet comprising known bits transmitted according to a selected transmission format.

4. The method of claim 3, further comprising the base station conveying the selected transmission format to the plurality of subscribers within a MAP.

5. The method of claim 3, wherein measuring a signal quality comprises each of the plurality of subscribers measuring a signal quality of the probe packet, and transmitting back to the base station the indicator if the signal quality of the probe packet is one of above or below the signal quality threshold.

6. The method of claim 2, further comprising;

if the estimate percentage increases a threshold amount over time, then increasing the signal quality threshold, and increasing the transmission modulation format and coding.

7. The method of claim 1, wherein the measured signal quality comprises at least one of CINR, CIR, BER, PER, BLER

8. The method of claim 1, further comprising collecting estimated percentages over time.

9. The method of claim 1, further comprising a plurality of multi-cast base stations, each of the multi-cast base stations estimating a percentage of subscribers that receive a multi-cast signal having a received signal quality above the signal quality threshold.

10. The method of claim 6, further comprising a base station controller estimating the percentage for each of the plurality of multi-cast stations.

11. The method of claim 6, further comprising a base station controller selecting a transmission modulation format and coding based on the estimated percentage for each of the plurality of multi-cast stations.

12. The method of claim 6, further comprising each subscriber transmitting back the indicators within scheduled frames, wherein the transmitting back of each subscriber occurs within intermittent scheduled frames.

13. The method of claim 6, wherein each subscriber transmits the indicator through a designated multiple access channel.

14. The method of claim 13, wherein each subscriber transmits the indicator back to the base station through the multiple access channel using a code randomly chosen from a predetermined set of codes.

15. The method of claim 9, wherein the transmitting back of the indicators by the subscribers is coordinated to avoid interference between transmissions of the indicators by the subscribers.

16. The method of claim 1, wherein the signal comprises layered modulation, and the transmission modulation format selection further comprises selecting a desired signal power differential between levels of the layered modulation signals.

17. The method of claim 16, further comprising:

a base station controller providing the desired signal power differential to a plurality of base stations;

the plurality of base stations broadcasting the layered modulation signal having the desired signal power differential between levels of the layered modulation signals.

18. The method of claim 17, wherein the layered modulation comprises 4QAM and 16QAM.

19. The method of claim 17, wherein the base station controller providing the desired signal power differential to a plurality of base stations, comprises:

the base station controller determining a histogram based estimated percentages;

the base station controller estimating the desired signal power differential needed to ensure a percentage of wireless links between the base stations and the subscribers that will have a desired level of signal quality, based on the histogram.

20. The method of claim 1, wherein the broadcast system comprises a multi-cast system.

21. A system for adaptively controlling layered modulation of a multiple base station multicast broadcast service, comprising:

a plurality of base stations each broadcasting a same layered modulation signal;

a plurality of subscribers receiving the layered modulation signal, and each subscriber determining a signal quality of the received layered modulation signal;

the plurality of subscribers each reporting the signal quality back to the plurality of base stations;

the plurality of base stations collecting the reported signal qualities over a predetermined period of time;

each of the plurality of base stations reporting the collected signal qualities to a base station controller; and

the base station controller statistically determining a desired signal power differential between levels of the layered modulation signals based on the collected signal qualities.

22. The method of claim 21, wherein the layered modulation comprises 4QAM and 16QAM.

23. The method of claim 21, wherein the base station controller providing the desired signal power differential to a plurality of base stations, comprises:

the base station controller determining a histogram based estimated percentages;

the base station controller estimating the desired signal power differential needed to ensure a percentage of wireless links between the base stations and the subscribers that will have a desired level of signal quality, based on the histogram.