Coexistence of OFDM-based WLANs by virtual subcarrier assignment (VISA) with multiple subcarrier puncturing

We have proposed a novel spatial filtering technique named "virtual subcarrier assignment" (VISA) for OFDM signals, which colors OFDM signals with different virtual subcarrier positions in their spectra to enable an adaptive array antenna at the receiver to accept the OFDM signals selectively (Hara, S., 2003; Hara and Jia, Y., 2004; Jia and Hara; 2004). We now propose an attractive application of VISA with multiple virtual subcarriers to realize easily the coexistence of multiple WLANs in a localized area. In addition, we present a multi-step RLS-based weight control algorithm to support VISA with multiple subcarrier puncturing in an IEEE 802.11a based system. The validity of the proposed system is verified by simulation results.