Method and apparatus for controllable simulation of mobility

• US 20080020746A1
• Filed: 07/18/2006
• Published: 01/24/2008
• Est. Priority Date: 07/18/2006
• Status: Active Grant

• Current Assignee: Keysight Technologies Singapore (Holdings) Pte. Limited. (Keysight Technologies, Inc.)
• Original Assignee: VeriWave, Incorporated (Keysight Technologies, Inc.)
• Inventors: Alexandar, Thomas, Stott, L. Noel
• Granted Patent: US 7,672,669 B2
• Time in Patent Office: Days
• US Class Current: 455/423
• CPC Class Codes: H04W 24/06 Testing, supervising or monitoring using simulated traffic

Abstract

Systems and methods enabling the efficient and repeatable simulation of mobility, during performance measurements of wireless data communications equipment are described. These are particularly useful for testing the impact on performance of spatial separation between Wireless Local Area Network (WLAN) devices, such as clients, relative to their counterparts, such as access points. For example, in accordance with one or more embodiments of the present invention, the controlled emulation of spatial distance effects by injecting impairments into the transmitted and received wireless data packet streams are disclosed to simulate the impact of distance on properties such as signal level, signal to noise ratio, and frame error ratio. Injection of impairments may be accomplished by varying the transmit power, artificially inducing errors into transmitted frames, and withholding acknowledgements for otherwise valid received frames, at levels consonant with the amount of distance to be emulated. This enables various mobility performance measurements to be made on WLAN devices without actually requiring that they be physically separated.

Claims

1. A system for testing a wireless data communication device, comprising:

a packet transmission datapath for transmitting wireless test data packets to said wireless data communication device;

a packet reception datapath for receiving wireless test data packets from said wireless data communication device; and

wherein said packet transmission datapath introduces controlled levels of impairment into said transmitted wireless test data packets, by increasing the frame error ratio of said transmitted wireless test data packets, to emulate the effects of spatial separation between said wireless data communication device and said system.

2. The system of claim 1, wherein said packet transmission datapath further comprises transmit error injection logic adapted, to increase said frame error ratio by deliberately corrupting said transmitted wireless test data packets prior to transmission.

3. The system of claim 2, wherein said transmit error injection logic modifies a Frame Check Sequence in said transmitted wireless test data packets.

4. The system of claim 2, wherein said transmit error injection logic corrupts said transmitted wireless test data packets at regular intervals, with the interval between corrupted packets being controlled.

5. The system of claim 2, wherein said transmit error injection logic corrupts said transmitted wireless test data packets at random intervals, with the overall probability of corruption being controlled.

6. The system of claim 1, wherein said levels of impairment comprises changing the power of said transmitted wireless test data packets.

7. The system of claim 6, wherein said packet transmission datapath further includes an attenuator adapted to provide said change in power.

8. The system of claim 7, wherein said attenuator is a digital step attenuator.

9. The system of claim 1, wherein said levels of impairment are modified on a packet-by-packet basis.

10. The system of claim 1, wherein said levels of impairment are dynamically modified to emulate the movement of WLAN devices.

11. A system for testing a wireless data communication device, comprising:

a packet transmission datapath for transmitting wireless test data packets to said wireless data communication device;

a packet reception datapath for receiving wireless test data packets from said wireless data communication device; and

wherein said packet reception datapath introduces controlled levels of impairment into the packet reception process to emulate the effects of spatial separation between said wireless data communication device and said system.

12. The system of claim 11, wherein said levels of impairment comprise the effective frame error ratio of said received wireless test data packets.

13. The system of claim 12, wherein said packet reception datapath further includes receive error injection logic adapted to control said effective frame error ratio by withholding acknowledgements for said received wireless test data packets.

14. The system of claim 13, wherein said receive error injection logic withholds acknowledgements at regular intervals, with the number of received packets between said withholding of acknowledgements being controlled.

15. The system of claim 13, wherein said receive error injection logic withholds acknowledgements at random intervals, with the overall probability of said withholding of acknowledgements being controlled.

16. The system of claim 13, wherein a decision to withhold an acknowledgement is made on a packet-by-packet basis.

17. The system of claim 13, wherein a decision to withhold an acknowledgement is made according to the contents of said received wireless test data packets.

18. The system of claim 11, wherein said levels of impairment are dynamically modified to emulate movement of WLAN devices.

19. The system of claim 13, wherein said packet transmission datapath is further adapted to introduce controlled levels of impairment into said transmitted wireless test data packets to further emulate the effects of spatial separation between said wireless data communication device and said system.

20. The system of claim 19 wherein the introduction of said levels of impairment into said transmitted wireless test data packets comprise increasing the frame error ratio of said transmitted wireless test data packets.

21. The system of claim 20, wherein said packet transmission datapath further includes transmit error injection logic adapted to increase said frame error ratio by deliberately corrupting said transmitted wireless test data packets prior to transmission.

22. The system of claim 21, wherein said transmit error injection logic modifies a Frame Check Sequence in said transmitted wireless test data packets.

23. The system of claim 21, wherein said transmit error injection logic corrupts said transmitted wireless test data packets at regular intervals, with the interval between corrupted packets being controlled.

24. The system of claim 21, wherein said transmit error injection logic corrupts said transmitted wireless test data packets at random intervals, with an overall probability of corruption being controlled.

25. The system of claim 19, wherein said impairments introduced into said transmitted wireless test data packets comprise decreasing the power of said transmitted wireless test data packets.

26. The system of claim 25, wherein said packet transmission logic further comprises an attenuator adapted to provide said decrease in power.

27. The system of claim 26, wherein said attenuator is a digital step attenuator.

28. The system of claim 19, wherein said levels of impairments introduced into said transmitted wireless test data packets are modified on a packet-by-packet basis.

29. The system of claim 19, wherein said levels of impairments introduced into said transmitted wireless test data packets are dynamically modified to emulate the movement of WLAN devices.

30. A method for emulating the effects of spatial separation between a wireless data communication tester and a wireless data communication device, comprising:

transmitting wireless test data packets from said wireless data communications tester to said wireless data communications device;

receiving wireless test data packets by said wireless data communications tester from said wireless data communications device;

introducing controlled levels of transmit impairment into said transmitted wireless test data packets; and

simulating controlled levels of receive impairment in said received wireless test data packets.

31. The method of claim 30, wherein said transmit impairment is introduced by corrupting said transmitted wireless test data packets.

32. The method of claim 31, wherein said corruption of said transmitted wireless test data packets is accomplished by modifying a Frame Check Sequence of said transmitted wireless test data packets at regular intervals with a predetermined interval.

33. The method of claim 31, wherein said corruption of said transmitted wireless test data packets is accomplished by modifying the Frame Check Sequence of said transmitted wireless test data packets at random intervals with a predetermined probability.

34. The method of claim 30, wherein said transmit impairment is introduced by changing the power level of said transmitted wireless test data packets.

35. The method of claim 30, wherein said receive impairment is introduced by withholding acknowledgements for said received wireless test data packets at regular intervals with a predetermined interval.

36. The method of 30, wherein said receive impairment is introduced by withholding acknowledgements for said received wireless test data packets at random intervals with a predetermined probability.