Data rate shifting methods and techniques

• US 20050249157A1
• Filed: 05/07/2004
• Published: 11/10/2005
• Est. Priority Date: 05/07/2004
• Status: Active Grant

• Current Assignee: Cisco Systems, Inc., Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Qian, Lu, Lewis, Michael E.
• Granted Patent: US 7,355,997 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04L 43/0829 Packet loss
• CPC Class Codes: H04L 43/0888 Throughput
• CPC Class Codes: H04L 47/25 with rate being modified by the source upon detecting a change of network conditions
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/0236 radio quality, e.g. interference, losses or delay
• CPC Class Codes: H04W 28/0242 Determining whether packet losses are due to overload or to deterioration of radio communication conditions
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

A technique for determining when to change a data rate by determining the cause of packet loss. The technique distinguishes between collision mediated packet loss and poor signal mediated packet loss. Rate shifting to a lower rate is performed after determining poor signals are causing packet loss. After switching to a lower rate, the packet loss rate can be compared to the pre-switch packet loss rate. If the packet loss rate has not improved by shifting to a lower data rate, then the data rate can be shifted to a higher rate. The technique can use a combination of channel response, signal strength, packet loss rate and throughput to determine when to switch data rates. A communication unit can maintain separate histories for each unit it is communicating with and employ a different data rate for each unit.

Claims

1. A method to optimize communications, comprising:

monitoring a performance parameter of a channel, the performance parameter being at least one selected form the group of throughput rate and packet rate loss;

monitoring signal quality; and

switching to a lower data rate after the performance parameter indicates a decrease in performance and the signal quality has degraded;

wherein the performance parameter that indicates a decrease in performance is at least one of the throughput rate decreasing and the packet loss rate increasing.

2. The method of claim 1, wherein the signal quality comprises measuring received signal strength of a received packet.

3. The method of claim 2, further comprising comparing the measured received signal strength with a previously measured received signal strength.

4. The method of claim 1, wherein the signal quality comprises obtaining an inverse Fourier transform of a packet to determine the impulse response of the channel.

5. The method of claim 1, wherein the signal quality comprises performing an autocorrelation of the channel to determine the frequency coherence of the channel.

6. The method of claim 1, wherein the signal quality comprises obtaining a Barker Correlation peak.

7. The method of claim 1, wherein a Bayesian based machine learning method is used, the machine employing two models to be compared, the first model is packet loss due to collisions and the second model is packet loss due to poor signal quality.

8. The method of claim 1, further comprising:

continuing to monitor the performance parameter after switching to the lower data rate; and

comparing the performance parameter after switching to the lower data rate with the performance parameter before switching to the lower data rate; and

switching to a higher date rate after the comparison determines that the performance parameter after switching to the lower data rate did not improve by a predetermined threshold.

9. The method of claim 1, wherein the higher data rate is the same as the data rate before switching to the lower data rate.

10. The method of claim 1, wherein the monitoring a performance parameter of a channel, and the monitoring signal quality is performed on a unit by unit basis.

11. The method of claim 1, further comprising:

switching to a higher data rate when the performance parameter indicates the signal quality has improved.

12. A method for optimizing communications, comprising:

maintaining a history of signal quality of a successfully received packet;

maintain a history of received signal strength of the successfully received packet;

maintaining a history of packet loss rate;

switching to a lower data rate after the history of packets loss rate indicates an increase in a rate of packets lost and at least one of a signal quality of a later received successfully received packet is a first predetermined threshold level below the signal quality of the successfully received packet, and a received signal strength of the later received successfully received packet is less than the received signal strength of the successfully received packet by a second predetermined threshold level.

13. The method of claim 12, further comprising:

comparing the packet loss rate of the lower data rate to the history of the packet lost rate; and

switching to a higher data rate after determining the packet loss rate of the lower data rate is greater than a predetermined threshold.

14. The method of claim 12, wherein the signal quality comprises obtaining an inverse Fourier transform of packet to determine the impulse response of the channel.

15. The method of claim 12, wherein the signal quality comprises performing an autocorrelation of the channel to determine the frequency coherence of the channel.

16. The method of claim 12, wherein the signal quality comprises obtaining a Barker Correlation peak.

17. The method of claim 12, further comprising:

switching to a higher data rate when the performance parameter indicates the signal quality has improved.

18. The method of claim 12, wherein the data rate can vary by individual communication device, the maintaining a history of signal quality of a successfully received packet is maintained by individual communication device, the maintain a history of received signal strength of the successfully received packet is maintained by individual communication device, and the maintaining a history of packet loss rate is maintained by individual communication device.

19. A communication device having a predetermined data rate for communicating with at least one other communication device, comprising:

a rate shifting module configured to decrease the data rate of the communication device after detecting an increased packet loss rate and decreased signal quality.

20. The communication device of claim 19, further comprising a packet rate measurement module measuring for determining packet loss rate including at least one of packet loss rate and throughput.

21. The communication device of claim 20, further comprising a signal quality assessment module for determining signal quality adapted to determine at least one of received signal strength from a successfully received packet, channel impulse response of a successfully received packet, frequency coherence from a successfully received packet and a Barker correlation peak from a successfully received packet.

22. The communication device of claim 21, further comprising the rate shifting module configured to receive a measurement from the packet rate measurement module and the signal quality assessment module and adapted to shift the communication device to a lower data rate after the packet rate measurement module detects one of an increased packet loss rate and decreased throughput, and the signal quality assessment module detects at least one of a decrease of received signal strength, a degradation in channel impulse response, a degradation in frequency coherence and a degradation in the Barker correlation peak.

23. The communication device of claim 22, further comprising a memory for storing a history of packet loss rate and a history of signal quality.

24. The communication device of claim 23, the communication device configured to set a data rate for each of the at least one other communication device.

25. The communication device of claim 24, the memory adapted to store a separate history of packet loss rate and a separate history of signal quality for each of the at least one other communication device.

26. A communication device, comprising:

means for measuring packet loss rate;

means for monitoring signal quality; and

means for changing a data rate responsive to the means for measuring packet loss rate and the means for monitoring signal quality.

27. The communication device of claim 26, wherein the means for changing a data rate changes the data rate to a lower data rate responsive to the means for measuring packet loss rate indicating an increased packet loss rate and the means for monitoring signal quality indicating a degradation in signal quality.

28. The communication device of claim 27, wherein:

the means for measuring packet loss rate further comprises a first memory means for maintaining packet loss rate history; and

the means for changing a data rate compares packet loss rate history after changing to the lower data rate with the packet loss rate history before changing to the lower data rate;

the means for changing a data rate responsive to change the data rate to a higher data rate responsive to the packet loss data rate being greater than a predetermined threshold.

29. The communication device of claim 29, wherein the predetermined threshold is the packet loss rate before changing to the lower data rate.