On the Performance of a Two-User MIMO Downlink System in Heavy Traffic

• Published in: IEEE transactions on information theory Vol. 53; no. 5; pp. 1851 - 1859
• Main Authors: Bhardwaj, S., Williams, R.J., Acampora, A.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Approximation; Base stations; Brownian motion; Channels; Communication channels; Coupled queueing systems; Data transmission; Delay; Diffusion; diffusion approximation; Diffusion processes; Downlink; Exact sciences and technology; heavy traffic; Information theory; Information, signal and communications theory; Mathematical analysis; MIMO; multiple-input multiple-output (MIMO); Multiplexers; Queues; Semimartingale Reflecting Brownian Motion (SRBM); Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teletraffic; Throughput; Traffic control; Traffic engineering; Traffic flow; Transmission and modulation (techniques and equipments); Two dimensional displays; Wireless communications; Performance evaluation; MIMO system; Design criterion; Wireless telecommunication; Information rate; Data transmission; Teletraffic; Downlink; System design; Two dimensional model; multiple-input multiple-output (MIMO); Information transmission; Brownian motion; diffusion approximation; Queueing system; Traffic management; Heavy traffic; Telecommunication channels; Diffusion process; Traffic control; Coupled queueing systems; Analog system; Semimartingale Reflecting Brownian Motion (SRBM)
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2007.894662

A multiple-input multiple-output (MIMO) downlink system in which data is transmitted to two users over a common wireless channel is considered. The channel is assumed to be fixed for all transmissions over the period of interest and the ratio of anticipated average arrival rates for the two users, also known as the relative traffic rate, is the system design parameter. A packet-based traffic model is considered where data for each user is queued at the transmit end. A queueing analog for this system leads to a coupled queueing system for which a simple policy is known to be throughput-optimal under Markovian assumptions. Since an exact expression for the performance is not available, as a measure of performance (in heavy traffic), a diffusion approximation is established. This diffusion process is a two-dimensional (2-D) Semimartingale Reflecting Brownian Motion (SRBM) living in the positive quadrant of 2-D space