US Patent 7672669 Method and apparatus for controllable simulation of mobility

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, clients, relative to their counterparts, access points. 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 of 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.