Capacity enhancement by terminal originated beamforming for wireless local area networks

Abstract

In dense traffic areas, wireless local area networks (WLANs) suffer from interference problems due to the usage of the crowded unlicensed ISM band and the lack of available spectrum. To mitigate these problems, a terminal side beamforming framework is proposed--this beamforming is capable of focusing the transmission and the reception in the relevant direction of the access point to exploit the directivity of the indoor propagation channel. It provides network transparency to achieve the backwards compatibility to the existing WLAN networks, and vendor transparency to ease the system design process and thereby achieve low complexity and costs. The beamforming enabled terminal benefits in terms of capacity, energy efficiency, and security while it does not require any change on the network side costing network providers new investments. It will be an attractive value-added feature as well as low-cost solution for the future WLAN terminal design opening the door for WLAN terminal manufacturers to include the proposed solution into their product line. In this work, a WLAN terminal beamforming demonstrator has been developed to demonstrate the capacity enhancement in real environments. Signal to interference ratio (SIR) improvement as well as array gain were investigated by simulations with IEEE 802.11n cluster channel models and by experiments with the demonstrator in a typical office environment. The comparable results of simulations and experiments show significant array gain and SIR improvement. The significant capacity increase has been demonstrated in the experiments in both an interference free scenario and an interference limited scenario.