Virtual subcarrier assignment with multiple subcarrier puncturing for spatial filtering of OFDM signals

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 adaptive array antenna at receiver to selectively accept the OFDM signals. We develop the VISA using multiple virtual subcarrier assignment, which assigns each OFDM signal not a virtual subcarrier position but a combination of multiple virtual subcarrier positions. We propose an attractive application of the VISA with multiple virtual subcarriers to easily realize the coexistence of multiple IEEE802.11a-based WLANs without significant change in medium access control (MAC) layer and physical layer. In addition, we present two kinds of RLS-based array weight control algorithms to support an IEEE802.11a-based system employing the VISA with multiple subcarrier puncturing. The system performance is evaluated by computer simulation. Numerical results verify that the VFSA with multiple subcarrier puncturing has the potential to support the coexistence of WLANs by effectively utilizing the space resource.