Effect of antenna directivity for outdoor mesh using MIMO systems

Wireless LAN cannot give enough throughputs in the non line of sight area. Establishing mesh networking outdoors between access points which covers non line of sight area is one solution that can expand broadband service areas simply and at low cost. The multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) system is adequate for mesh networks because of its good frequency utilization characteristics. If a directional antenna is applied to a MIMO system, we anticipate an improvement in the channel capacity through the directional-antenna gain. However, using this antenna suppresses the arrival waves, which are important to the MIMO system. Up to now, there have been only a few MIMO propagation characteristic studies that focus on antenna directivity under outdoor LOS conditions. Therefore, in this study, MIMO propagation characteristics are measured for outdoor mesh networking. This paper focuses on the channel capacity, eigenvalues, and channel correlation characteristics. The results show that the MIMO with directional antenna can improve 90% in channel capacity, 83% in eigenvalue, and 70% in channel correlation than that of MIMO with an omni-directional antenna.