Determining the effects of new types of impairments on perceived quality of a voice service

• US 7,099,282 B1
• Filed: 05/30/2001
• Issued: 08/29/2006
• Est. Priority Date: 12/24/1998
• Status: Expired due to Term

• Current Assignee: Far North Patents, LLC
• Original Assignee: MCI Incorporated (Verizon Communications Inc.)
• Inventors: Hardy, William Christopher
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): Tran, Thien D
• Application Number:
  US09/866,770
• Time in Patent Office: 1,917 Days
• Field of Search: 370/241, 370/246, 370/248, 370/249, 370/250, 370/251, 370/252, 370/253, 370/201, 370/242, 370/232, 370/233, 370/234
• US Class Current: 370/252
• CPC Class Codes: H04L 41/5009 Determining service level performance parameters or violations of service level contracts, e.g. violations of agreed response time or mean time between failures [MTBF]
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04M 3/2227 Quality of service monitoring

Abstract

Empirically derived models are used to relate user perception to objectively measurable characteristics, under a criterion of nearly perfect co-variance between predicted MOS values and the variations in the values of the objectively measurable characteristics. In the example context of evaluating packet switched telephony service, the present invention eliminates the need to perform subjective tests to characterize each combination of codec type and transmission protocol.

Claims

1. Where a first communications service exhibits a first performance characteristic affecting communications quality and a second communications service exhibits both the first performance characteristic and a second performance characteristic not exhibited by the first communications service, a method for determining the effect of the second performance characteristic upon the quality of the second communications service comprising the steps of:

establishing communications via the second communications service;

obtaining objective measurements of the first performance characteristic as the second performance characteristic varies;

converting the objective measurements of the first performance characteristic into subjective ratings based upon knowledge of the first communication service;

altering the subjective ratings to reflect the effects of the second performance characteristic by use of an assumed model for the effects of the second performance characteristic upon the subjective ratings of the first performance characteristic;

computing quality index values from the altered subjective ratings; and

adjusting the assumed model to improve the correlation between the quality index values and the second performance characteristic.

2. The method of claim 1 further comprising the step of:

using the assumed model in subsequent analyses of communications systems having similar characteristics.

3. The method of claim 1 wherein the first performance characteristic is speech distortion.

4. The method of claim 1 wherein the second performance characteristic is packet loss rate.

5. The method of claim 1 further comprising the step of:

adjusting the assumed model until a desired degree of correlation is achieved.

6. Where a first communications service exhibits a first performance characteristic affecting communications quality and a second communications service exhibits both the first performance characteristic and a second performance characteristic not exhibited by the first communications service, an apparatus for determining the effect of the second performance characteristic upon the quality of the second communications service comprising:

means for establishing communications via the second communications service;

means for obtaining objective measurements of the first performance characteristic as the second performance characteristic varies;

means for converting the objective measurements of the first performance characteristic into subjective ratings based upon knowledge of the first communication service;

means for altering the subjective ratings to reflect the effects of the second performance characteristic by use of an assumed model for the effects of the second performance characteristic upon the subjective ratings of the first performance characteristic;

means for computing quality index values from the altered subjective ratings; and

means for adjusting the assumed model to improve the correlation between the quality index values and the second performance characteristic.

7. The apparatus of claim 6 further comprising:

means for using the assumed model in subsequent analyses of communications systems having similar characteristics.

8. The apparatus of claim 6 wherein the first performance characteristic is speech distortion.

9. The apparatus of claim 6 wherein the second performance characteristic is packet loss rate.

10. The apparatus of claim 6 further comprising:

means for adjusting the assumed model until a desired degree of correlation is achieved.