Addressing Hidden Terminals in WLANs with Zero Forcing Coordinated Beamforming

We present here a new technique that can be used to address a well-known Hidden Terminal problem in Wireless Local Area Networks. Specifically, Zero Forcing Coordinated Beamforming can be applied, in a hidden terminal scenario, in order to null the signal of the interfering transmitter so that desired transmission can take place without collision at the receiver. Basically, a precoding range of a receiver is used as a determinant in order to take a nulling decisions based on the notion that a successful transmission depends on the interference free condition at the receiver. We demonstrate the feasibility of the approach in an USRP2/GNURadio test-bed prototype. Our scheme improves the SNR and Effective SNR from about 5 to 11 dB in a hidden terminal scenario and maintains collision free simultaneous transmissions.