Joint MIMO-OFDM and MAC Design for Broadband Multihop Ad Hoc Networks

Multiple input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM) are very promising techniques to exploit diversity in the physical layer of broadband wireless communications. However, the application of these techniques to broadband multihop ad hoc networks is subject to inefficiencies since existing medium access control (MAC) schemes are designed to allow only one node to transmit in a neighborhood. Therefore, adding more relays to increase the transmission range decreases the throughput. With MIMO-OFDM, multiple transmissions can coexist in the same neighborhood. A new cooperative transceiver architecture with MIMO-OFDM and MAC scheme–multiple antennas receiver initiated busy tone medium access (MARI-BTMA) is proposed in this paper. MARI-BTMA is based on receiver initiated busy tone medium access (RI-BTMA) and uses multiple out of band busy-tones to notify the nodes about the number of users in the system to avoid the collision of the nodes on the same channel. To improve the performance at low traffic loads, an adaptive MARI-BTMA is also proposed. In this paper, both theoretical and numerical analysis of the throughput and delay are presented. Analysis and simulation results show the improved performance of MARI-BTMA compared with RI-BTMA and carrier sensing medium access/collision avoidance (CSMA/CA). Index Terms MIMO OFDM MAC MPR ad hoc networks