Voice quality measurement for voice over IP in a wireless local area network

1. A method of measuring voice quality of Voice over IP (VoIP) data in a wireless network, the method comprising:

monitoring, at a detector, a set of frames wirelessly transmitted between first and second wireless devices in the wireless network, the detector being at a location remote with respect to the first and second wireless devices;

identifying missing wireless frames in the set;

determining a burst rate based on the identification of missing wireless frames in the set; and

determining a rating value indicative of voice quality based on a loss rate and burst rate determined only using frames received by the detector during monitoring.

2. The method defined in claim 1 wherein determining the rating value is performed independent of physical characteristics of the first and second wireless devices and of the wireless network.

3. The method defined in claim 1 wherein the set of frames includes VOIP data.

4. The method defined in claim 1 further comprising determining the loss rate based on the number of wireless frames in the set and an expected number of wireless frames.

5. The method defined in claim 4 wherein the loss rate is also determined based on arrival times of frames in the number of wireless frames.

6. The method defined in claim 4 wherein determining the loss rate based on the number of wireless frames in the set and an expected number of wireless frames comprises calculating the loss rate as a ratio of the number of lost wireless frames to the expected number of wireless frames in the set.

7. The method defined in claim 6 wherein the loss rate is also determined based on arrival times of frames in the number of wireless frames.

8. A method of measuring voice quality of Voice over IP data in a wireless network, the method comprising:

receiving at a detector in the wireless network a set of wireless frames transmitted between a first wireless device and a second wireless device in the wireless network in a predetermined time period, wherein the wireless frames in the set carry Voice over Internet Protocol data;

identifying missing wireless frames in the set;

determining a loss rate based on the number of wireless frames in the set and their arrival time and an expected number of wireless frames;

determining a burst rate based on the identification of missing wireless frames in the set; and

determining a rating value indicative of voice quality based on the loss rate and burst rate.

9. The method of claim 8 , comprises:

calculating the expected number of wireless frames by dividing the predetermined time period by an expected inter-frame interval;

calculating a number of lost wireless frames as the difference between the expected number of wireless frames and the number of wireless frames in the set; and

calculating the loss rate as a ratio of the number of lost wireless frame to the expected number of wireless frames in the set.

10. The method of claim 8 wherein determining the loss rate comprises:

calculating the loss rate based on the received set of wireless frames and any frames identified as missing wireless frames in the set.

11. The method defined in claim 10 wherein identifying missing wireless frames comprises identifying a frame as a missing frame if its arrival time is not its expected arrival time.

12. The method of claim 8 , wherein determining the burst rate comprises:

determining a number of found-to-lost transitions based on the identification of missing wireless frames in the set;

determining a number of lost-to-found transitions based on the identification of missing wireless frames in the set;

calculating a first probability that a wireless frame goes from a found to lost state by dividing the determined number of found-to-lost transitions by the expected number of wireless frames originating from a found state;

calculating a second probability that a wireless frame goes from a lost to found state by dividing the determined number of lost-to-found transitions by the expected number of wireless frames originating from a lost state; and

calculating the burst rate by dividing one by the sum of the first and second probabilities.

13. The method of claim 12 , further comprising:

determining arrival times of the wireless frames in the set; and

determining time ranges, wherein all of the time ranges have the same duration, and wherein each time range has a different start time and end time, and wherein the missing wireless frames are identified based on the arrival times of the wireless frames and the determined time ranges.

14. The method of claim 13 , wherein the time ranges are determined based on an expected inter-frame interval and a buffer delay associated with a jitter buffer.

15. The method of claim 12 , further comprising:

examining sequence numbers of the wireless frames in the set of wireless frames; and

comparing the sequence numbers of the wireless frames in the set of wireless frames, wherein the missing wireless frames are identified based on the comparison of the sequence numbers of the wireless frames in the set of wireless frames.

16. The method of claim 8 , further comprising:

determining actual inter-frame intervals of the wireless frames in the set of wireless frames based on the arrival times of the wireless frames in the set of wireless frames;

calculating differences between the actual inter-frame intervals and an expected interframe interval; and

calculating a jitter number based on an average of the calculated differences.

17. The method of claim 8 , further comprising:

mapping the rating value to a voice quality score.

18. The method of claim 17 , further comprising:

determining a plurality of rating values over a period of time;

mapping the plurality of rating values to a plurality of voice quality scores over the period of time;

displaying the voice quality scores over the period of time; and

displaying one or more measured wireless-related factors over the period of time in conjunction with the displayed voice quality scores over the period of time.

19. The method of claim 18 , wherein the one or more measured wireless-related factors include signal noise.

20. The method of claim 18 , wherein the one or more measured wireless-related factors include network traffic.

21. The method of claim 18 , wherein the voice quality scores are mean opinion scores.

22. A system to measure voice quality of Voice over IP data in a wireless network, the system comprising:

an access point;

a station associated with the access point; and

a detector disposed within transmission range of the access point and the station, wherein the detector is configured to:

receive a set of wireless frames transmitted between the station and the access point in a predetermined time period, wherein the wireless frames in the set carry Voice over Internet Protocol data;

identify missing wireless frames in the set;

determine a loss rate based on the number of wireless frames in the set and an expected number of wireless frames;

determine a burst rate based on the identification of missing wireless frames in the set; and

determine a rating value indicative of voice quality based on the loss rate and burst rate.

23. A detector to measure voice quality of Voice over IP data in a wireless network, the detector comprising:

an antenna configured to receive a set of wireless frames transmitted between a first wireless device and second wireless device in the wireless network in a predetermined time period, wherein the wireless frames in the set carry Voice over Internet Protocol data; and

a processor configured to execute instructions on a computer-readable medium, the computer-readable medium having instructions for:

identifying missing wireless frames in the set;

determining a loss rate based on the number of wireless frames in the set and an expected number of wireless frames;

determining a burst rate based on the identification of missing wireless frames in the set; and

determining a rating value indicative of voice quality based on the loss rate and burst rate.

24. The detector of claim 23 , wherein the computer-readable medium has instructions for:

determining a plurality of rating values over a period of time; and

mapping the plurality of rating values to a plurality of voice quality scores over the period of time.

25. The detector of claim 24 , further comprising:

a display to display the voice quality scores over the period of time and one or more measured wireless-related factors over the period of time in conjunction with the displayed voice quality scores over the period of time.

26. The detector of claim 25 , wherein the voice quality scores are mean opinion scores.

27. The computer-readable medium of claim 26 , wherein the voice quality scores are mean opinion scores.

28. The computer-readable medium of claim 24 , further comprising instructions for:

determining a plurality of rating values over a period of time;

mapping the plurality of rating values to a plurality of voice quality scores over the period of time;

displaying the voice quality scores over the period of time; and

displaying one or more measured wireless-related factors over the period of time in conjunction with the displayed voice quality scores over the period of time.

29. A computer-readable medium containing instructions which, when executed by a computer, cause the computer to measure voice quality of Voice over IP data in a wireless network, comprising instructions for:

obtaining a set of wireless frames transmitted between a first wireless devices and a second wireless device in the wireless network in a predetermined time period, wherein the wireless frames in the set carry Voice over Internet Protocol data;

identifying missing wireless frames in the set;

determining a loss rate based on the number of wireless frames in the set and an expected number of wireless frames;

determining a burst rate based on the identification of missing wireless frames in the set; and

determining a rating value indicative of voice quality based on the loss rate and burst rate.