Implementation of a SDR-based Redundant Access Network using NI USRP-RIO

Wireless transmission is, broadly speaking, considered unreliable and unstable. For real-time applications, redundancy must be counted as a solution for preventing system unavailability. In this paper a testbed comprised of three National Instruments USRP-RIO platforms (two acting as access points, and one as a client station) was set in order to test the performance of a redundant IEEE 802.11-based access network. The 802.11 Application Framework was modified on the receiving side to allow the client to change between the two access points operating in different frequency bands, considering as the trigger values the received radiofrequency input power and throughput. Experimental results and measurements confirm that this implementation improves the reliability of the access network, and bring forward the high processing capabilities of the USRP FPGA based devices. Moreover, the test measurements were validated using the Rohde & Schwarz CMW500 Wideband Radio Communication Tester, proving the compatibility of the adopted solution.