Channel Access Scheme for MIMO-Enabled Ad Hoc Networks with Adaptive Diversity/Multiplexing Gains

Transmission power control (TPC) is used in wireless networks to improve channel reuse and/or reduce energy consumption. It has been often applied to single-input single-output (SISO) systems, where each node is equipped with a single antenna. Multiinput multi-output (MIMO) systems can improve the throughput or the signal-to-noise ratio (SNR) by providing multiplexing or diversity gains, respectively. In this paper, we incorporate a power-controlled MAC protocol for a wireless network with two antennas per node. Our protocol, coined CMAC, combines different types of MIMO gains, allowing for dynamic switching between diversity and multiplexing modes so as to maximize a utility function that depends on both energy consumption and throughput. CMAC adapts the “antenna mode,” the transmission power, and the modulation order on a per-packet basis. By “antenna mode” we mean one of five possible transmit/receive antenna configurations: 1 × 1 (SISO), 2 × 1 (MISO-D), 1×2 (SIMO-D), 2×2 (MIMO-D), and 2×2 (MIMO-M). This research was supported in part by NSF (under grants CNS-0721935, CNS-0627118, CNS-0325979, and CNS-0313234), Raytheon, and Connection One (an I/UCRC NSF/industry/university consortium). Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the National Science Foundation. An abridged version of this paper was presented at the BROADNETS 2007 Conference, North Carolina, USA, September 10–14, 2007. M. Z. Siam (B) · M. Krunz Department of Electrical and Computer Engineering, The University of Arizona, Tucson, AZ 85721, USA e-mail: [email protected] M. Krunz e-mail: [email protected] The second, third, and fourth configurations offer a diversity gain, whereas the last configuration offers a multiplexing gain. By using control packets to bound the transmission power of potentially interfering terminals, CMAC allows for multiple interference-limited transmissions to take place in the vicinity of a receiving terminal. We study via simulations the performance of CMAC in ad hoc topologies. Our results indicate that relative to non-adaptive protocols, CMAC achieves a significant improvement in both the overall energy consumption and the throughput.