Performance of a Concurrent Link SDMA MAC Under Practical PHY Operating Conditions

• Published in: IEEE transactions on vehicular technology Vol. 60; no. 3; pp. 1301 - 1307
• Main Authors: Pengkai Zhao, Daneshrad, B, Warrier, A, Weijun Zhu, Takeshita, O
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access control; Access methods and protocols, osi model; Ad hoc networks; Adaptation; Algorithms; Applied sciences; Array signal processing; Business and industry local networks; Channel estimation; Channels; Concurrent communications; Detection, estimation, filtering, equalization, prediction; Exact sciences and technology; Information, signal and communications theory; Links; medium access control (MAC); MIMO; multi-input-multi-output (MIMO); Multiple access; Networks; Networks and services in france and abroad; Noise measurement; Nulling; Protocol (computers); Protocols; Signal and communications theory; Signal, noise; space division multiple access (SDMA); Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Throughput; Transmission and modulation (techniques and equipments); Access control; Performance evaluation; Parameter estimation; Predictor; Wireless telecommunication; Information rate; Beam forming; Mean square error; Channel estimation; Concurrent communications; space division multiple access (SDMA); Ad hoc network; Singular value decomposition; MIMO system; Estimation error; Baseline; Algorithm; Information transmission; Operating conditions; medium access control (MAC); Space division multiple access; multi-input-multi-output (MIMO); Signal processing; Access protocol; Comparative study
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2010.2103096

Space division multiple access (SDMA)-based medium access control (MAC) protocols have been proposed to enable concurrent communications and improve link throughput in multi-input-multi-output (MIMO) ad hoc networks. For the most part, the works appearing in the literature make idealized and simplifying assumptions about the underlying physical layer and some aspects of the link adaptation protocol. The result is that the performance predicted by such works may not necessarily be a good predictor of the actual performance in a fully deployed system. In this paper, we look to introduce elements into the SDMA-MAC concept that would allow us to better predict their performance under realistic operating conditions. Using a generic SDMA MAC, we look at how the network sum throughput changes with the introduction of the following: (1) use of the more practical MMSE algorithm, instead of the zero-forcing or singular-value-decomposition-based nulling algorithms used for receive beamnulling; (2) impact of channel estimation errors; (3) introduction of link adaptation mechanism specifically designed for concurrent SDMA MACs; and (4) incorporation of TX beamforming along with RX beamnulling. Following on the transmission window during which concurrent transmissions are allowed by the MAC, we qualify the impact of each of these four elements in isolation. At the conclusion, the performance of a system that incorporates elements 1-4 is presented and compared against the baseline system, showing an improvement of up to five times in the overall network sum throughput.