Self optimization of time division duplex (TDD) timing and adaptive modulation thresholds
View Patent ↗A wireless broadband communication system that operates with high efficiency and reduced latency in long range point-to-point and point-to-multipoint applications. The system includes multiple transceivers and multiple antennas for transmitting and receiving wireless signals using TDD techniques over multiple channels, which include a control channel for setting both the size of the transmit bursts and the modulation threshold level. By determining the size of the transmit bursts for a subsequent data transmission based upon the number of filler packets detected in a specified number of previously received bursts, and adjusting the modulation threshold level for the subsequent transmission based upon the transmit burst size, the system provides increased data throughput, while maintaining the packet error rate at an acceptable level. As the throughput requirements of the system are relaxed, the modulation threshold levels can be adjusted to provide reduced packet error rates.
1. A method of operating a wireless communication system, said system comprising at least one first transceiver and at least one second transceiver, the method comprising the steps of:
transmitting, by said first transceiver, a first set of data bursts over at least one communication channel using a first modulation mode, said first modulation mode providing a packet error rate, wherein said first set of data bursts comprises a first predetermined number n of bursts, each of the bursts within said first set having a first burst size and comprising at least one data packet and zero or more intentionally provided filler packets;
receiving said first set of data bursts by said second transceiver;
determining a number d of data bursts within said received first set that contain no filler packets; and
determining a new burst size for a next first predetermined number n of bursts based on the number d of data bursts within said received first set that contain no filler packets.
2. The method of claim 1 wherein the step of determining a new burst size for the next first predetermined number n of bursts comprises: in a first selecting step, selecting a next larger burst size relative to said first burst size if the number d is equal to the first predetermined number n (d=n), and selecting a next smaller burst size relative to said first burst size if the number d is less than a second predetermined number N, said second predetermined number N being less than said first predetermined number n (d<N<n).
3. The method of claim 2 further comprising selecting a modulation mode providing a next higher packet error rate relative to the packet error rate provided by said first modulation mode if the next larger burst size is selected in the first selecting step, and selecting a modulation mode providing a next lower packet error rate relative to the packet error rate provided by said first modulation mode if the next smaller burst size is selected in the first selecting step.
4. The method of claim 3 further comprising providing indications of the selected burst size and the selected modulation mode to said first transceiver when one of the next larger burst size and the next smaller burst size is selected in the first selecting step.
5. The method of claim 4 wherein when the selected burst size and the selected modulation mode are provided to said first transceiver, the method further comprises:
transmitting, by said first transceiver, a second set of data bursts over said communication channel using said selected modulation mode, each of the bursts within said second set having said selected burst size;
otherwise, transmitting said second set of data bursts over said communication channel using said first modulation mode, each of the bursts within said second set having said first burst size.
6. The method of claim 5 wherein said first set of data bursts and said second set of data bursts comprise the same number n of bursts.
7. The method of claim 4 wherein indications of the selected burst size and the selected modulation mode are provided to said first transceiver by said second transceiver transmitting the indications over a control channel.
8. The method of claim 2 wherein the first selecting step further comprises selecting the next larger burst size relative to said first burst size if d is greater than n (d>n).
9. The method of claim 8 wherein each of said first burst size, said next larger burst size, and said next smaller burst size is one of a plurality of burst sizes, and wherein the second predetermined number N is equal to a number of burst sizes within said plurality of burst sizes.
10. The method of claim 1 wherein determining a number d of data bursts within said received first set that contain no filler packets comprises determining, by said second transceiver, the number d of data bursts within said received first set that contain no filler packets.
11. The method of claim 1 wherein the transmitting step comprises transmitting said first set of data bursts over said communication channel using said first modulation mode, and wherein each packet within each burst comprises at least one orthogonal frequency division modulation (OFDM) symbol.
12. The method of claim 11 wherein the size of each burst corresponds to a number of OFDM symbols included in the respective burst.
13. The method of claim 1 wherein the step of determining a new burst size for the next first predetermined number n of bursts comprises: in a first selecting step, selecting a next larger burst size relative to said first burst size if the number d is greater than the first predetermined number n (d>n), and selecting a next smaller burst size relative to said first burst size if the number d is less than a second predetermined number N, said second predetermined number N being less than said first predetermined number n (d<N<n).
14. A wireless communication system, comprising:
at least one first transceiver operative to transmit a first set of data bursts over at least one communication channel using a first modulation mode, said first modulation mode providing a packet error rate,
wherein said first set of data bursts comprises a first predetermined number n of bursts, each of the bursts within said first set having a first burst size and comprising at least one data packet and zero or more intentionally provided filler packets; and
at least one second transceiver, said second transceiver being operative:
to receive said first set of data bursts;
to determine a number d of data bursts within said received first set that contain no filler packets; and
to determine a new burst size for a next first predetermined number n of bursts based on the number d of data bursts within said received first set that contain no filler packets.
15. The system of claim 14 wherein the at least one second transceiver is configured to determine a new burst size for the next first predetermined number n of bursts based on the number d of data bursts within said received first set that contain no filler packets by selecting a next larger burst size relative to said first burst size if the number d is equal to the first predetermined number n (d=n), and selecting a next smaller burst size relative to said first burst size if the number d is less than a second predetermined number N, said second predetermined number N being less than said first predetermined number n (d<N<n).
16. The system of claim 15 wherein the at least one second transceiver is further operative to select a modulation mode providing a next higher packet error rate relative to the packet error rate provided by said first modulation mode if the next larger burst size is selected, and to select a modulation mode providing a next lower packet error rate relative to the packet error rate provided by said first modulation mode if the next smaller burst size is selected.
17. The system of claim 16 wherein the at least second transceiver is further operative to provide indications of the selected burst size and the selected modulation mode to said first transceiver.
18. The system of claim 17 wherein the at least one first transceiver is further operative, in the event the selected burst size and the selected modulation mode are provided to said first transceiver, to transmit a second set of data bursts over said communication channel using said selected modulation mode, each of the bursts within said second set having said selected burst size.
19. The system of claim 18 wherein said first set of data bursts and said second set of data bursts comprise the same number n of bursts.
20. The system of claim 15 wherein each of said first burst size, said next larger burst size, and said next smaller burst size is one of a plurality of burst sizes, and wherein the second predetermined number N is equal to a number of burst sizes within said plurality of burst sizes.
21. The system of claim 14 wherein the predetermined number n is equal to a number of bursts within said first set.
22. The system of claim 14 wherein said second transceiver is further operative to transmit the indications of the selected burst size and the selected modulation mode to said first transceiver over a control channel.
23. The system of claim 14 wherein each packet within each burst comprises at least one orthogonal frequency division modulation (OFDM) symbol.
24. The system of claim 23 wherein the size of each burst corresponds to a number of OFDM symbols included in the respective burst.
25. The system of claim 24 wherein the communication link is a broadcast style point-to-multipoint link.
26. The system of claim 14 wherein said at least one first transceiver is disposed at one end of a communication link, and said at least one second transceiver is disposed at an opposite end of the communication link.
27. The system of claim 26 wherein the communication link is a broadcast style point-to-point link.
28. The system of claim 14 wherein the at least one second transceiver is configured to determine a new burst size for the next first predetermined number n of bursts based on the number d of data bursts within said received first set that contain no filler packets by selecting a next larger burst size relative to said first burst size if the number d is greater than the first predetermined number n (d>n), and selecting a next smaller burst size relative to said first burst size if the number d is less than a second predetermined number N, said second predetermined number N being less than said first predetermined number n (d<N<n).