Multiple-Input Multiple-Output (MIMO) antenna systems present a radical way to improve the performance of wireless communications. Such systems can be utilized in wireless ad hoc networks for improved throughput in several ways. A straightforward way is to regard the MIMO system just as a new link layer technology that provides a higher data rate. In this way, MIMO systems can be integrated with legacy Media Access Control (MAC) protocols such as 802.11 DCF. Recently, a few studies have proposed MAC protocols leveraging the advantages of MIMO systems in a different way. Those new MAC protocols enhance the network throughput by allowing simultaneous multiple communications at a lower rate rather than a single communication at a higher rate in a single collision domain. In this paper, we present a new MIMO MAC protocol for Ad hoc Networks namely MIMOMAN. MIMOMAN tries to further increase the network throughput by combining the two approaches, i.e., allowing simultaneous multiple communications at a higher data rate. It is beneficial especially in a heterogeneous setting where the number of antennas installed on each node varies. As a part of the protocol, MIMOMAN also suggests a new beamforming algorithm that allows spatial reuse among spatial multiplexing MIMO links. We investigate the performance of MIMOMAN through a simulation study.
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