Introduction

In the last few years, there has been a lot of interest in wireless ad hoc networks as they have remarkable commercial and military applications. Such wireless networks have the benefit of avoiding a wired infrastructure. However, signal fading is a severe problem for wireless communications, particularly for the multi-hop transmissions in the ad hoc networks. In real application, without considering this issue, signals may not be received properly. In order to deal with this problem, the use of diversity provides a good way to reduce signal interference. The multiple-input-multiple-output (MIMO) antenna can provide spatial diversity and multiplexing gain in wireless networks. It also represents a powerful technique for interference mitigation and reduction. Therefore, to meet the needs of future wireless communications, it is advantageous to equip the associated wireless ad hoc networks with MIMO antenna capabilities.