Radio front-end enabling WLAN over white spaces cognitively

This paper describes a radio transceiver prototype based on TDD for TV white space frequencies, which can be used for WLAN based cognitive radio solutions. The prototype is designed out of off-the-shelf components and can be flexibly employed with any commercially available access points (AP) for sensing and accessing unused white spaces. This hardware with a WLAN device forms a high-IF architecture that provides high out-of-band linearity. The architecture of the prototype is briefly discussed outlining the constraints for the reception and transmission catering to 802.11b/g requirements. Performance conformance tests are discussed at length for both receiver and transmitter sections. It is shown that with the addition of this UHF converter, the performance of an AP is not degraded. The receiver sensitivity is found to be -90.7 dBm which is 8 dB better than that specified by the standard. The maximum transmitted power is 21 dBm with all the spurious requirements and EVM of the WLAN standard being satisfied.