Data rate shifting methods and techniques

• US 7,355,997 B2
• Filed: 05/07/2004
• Issued: 04/08/2008
• Est. Priority Date: 05/07/2004
• Status: Expired due to Fees

• 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.
• Primary Examiner(s): LY, ANH VU H
• Application Number:
  US10/841,781
• Publication Number:
  US 20050249157A1
• Time in Patent Office: 1,432 Days
• Field of Search: None
• US Class Current: 370/328
• 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 from the group of throughput rate and packet rate loss;

monitoring signal quality;

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

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

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;

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 the higher data rate is the same as a data rate before switching to the lower data rate.

8. 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.

9. The method of claim 1, further comprising:

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

10. A method for optimizing communications, comprising:

maintaining a history of signal quality of a successfully received packet with a data rate;

maintaining 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 packet 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.

11. The method of claim 10, 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.

12. The method of claim 10, wherein the signal quality comprises obtaining an inverse Fourier transform of packet to determine the impulse response of a channel.

13. The method of claim 10, wherein the signal quality comprises performing an autocorrelation of a channel to determine the frequency coherence of the channel.

14. The method of claim 10, wherein the signal quality comprises obtaining a Barker Correlation peak.

15. The method of claim 10, further comprising:

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

16. The method of claim 10, wherein a 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 maintaining 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.

17. 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;

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;

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

wherein 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; and

wherein 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 of the lower data rate being greater than a predetermined threshold.

18. The communication device of claim 17, wherein the predetermined threshold is the packet loss rate before changing to the lower data rate.

19. An apparatus, comprising:

a packet rate measuring module configured to monitor a performance parameter, the performance parameter is at least one selected from a group consisting of throughput rate and packet rate loss;

a signal quality assessment module; and

a rate shifting module coupled to the packet rate measuring module and the signal quality assessment module;

wherein the rate shifting module is configured to switch to a lower data rate responsive to the performance parameter indicating a decrease in performance and the signal quality assessment module indicates a decrease in signal quality;

where the rate shifting module is configured to continue monitoring the performance parameter after switching to the lower data rate;

wherein the rate shifting module is configured to compare the performance parameter with the performance parameter after switching to the lower data rate;

wherein the rate shifting module is configured to switch to a higher data rate responsive to determining that the performance parameter after switching to a lower data rate did not improve by a predetermined threshold; and

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.

20. The apparatus of claim 19, wherein the signal quality assessment module measures a received signal strength of a received packet.

21. The apparatus of claim 20, wherein the rate shifting module is configured to compare the measured received signal strength of a packet received after switching to the lower data rate with a received signal strength measured before switching to the lower date rate.

22. The apparatus of claim 19, wherein the signal quality assessment module is configured to obtain an inverse Fourier transform of a packet to determine the impulse response of a channel.

23. The apparatus of claim 19, wherein the signal quality assessment module performs an autocorrelation of a channel to determine frequency coherence of the channel.

24. The apparatus of claim 19, wherein the signal quality assessment module obtains a Barker Correlation peak.

25. The apparatus of claim 19, wherein the higher data rate is the same as a data rate before switching to the lower data rate.

26. The apparatus of claim 19, wherein the rate shifting module is configured to switch to a higher data rate when the performance parameter indicates the signal quality has improved.

27. An apparatus, comprising:

a channel quality module;

a received signal strength module configured to determine the signal strengths of received signals;

a packet loss module configured to determine packet loss rate;

a rate shifting module coupled to the channel quality module, received signal strength module and the packet loss module;

wherein the rate shifting module is configured to maintain a history of signal quality of a successfully received packet with a data rate;

wherein the rate shifting module is configured to maintain a history of received signal strength of the successfully received packet;

wherein the rate shifting module is configured to maintain a history of packet loss rate; and

wherein the rate shifting module is configured to switch to a lower data rate responsive to the history of packet loss rate indicating 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.

28. The apparatus of claim 27, wherein the rate shifting module is configured to compare the packet loss rate of the lower data rate to the history of the packet lost rate;

and

wherein the rate shifting module is configured to switch to a higher data rate upon determining the packet loss rate of the lower data rate is greater than a predetermined threshold.

29. The apparatus of claim 27, wherein the channel quality module is configured to obtain an inverse Fourier transform of packet to determine the impulse response of a channel.

30. The apparatus of claim 27, wherein the channel quality module is configured to perform an autocorrelation of a channel to determine the frequency coherence of the channel.

31. The apparatus of claim 27, wherein the channel quality module is configured to obtain a Barker Correlation peak.

32. The apparatus of claim 27, wherein the rate shifting module is further configured to switch to a higher data rate when a performance parameter indicates the signal quality has improved.

33. The apparatus of claim 27, further comprising a throughput module configured to determine an effective throughput of a channel coupled to the rate shifting module.