Spectrum Sharing SDMA with Limited Feedback: Throughput Analysis

• Han-Shin Jo,

Vol. 6, No. 12, December 30, 2012
10.3837/tiis.2012.12.012, Download Paper (Free):

• Asymptotic throughput scaling
• space-division multiple access (SDMA)
• spectrum sharing
• precoding
• feedback overhead
• null-steering

Abstract

In the context of effective usage of a scarce spectrum resource, emerging wireless communication standards will demand spectrum sharing with existing systems as well as multiple access with higher spectral efficiency. We mathematically analyze the sum throughput of a spectrum sharing space-division multiple access (SDMA) system, which forms a transmit null in the direction of other coexisting systems while satisfying orthogonal beamforming constraints. For a large number of users , the SDMA throughput scales as at high signal-to-noise ratio (SNR) ((J - 1) at normal SNR), where is the number of transmit antennas. This indicates that multiplexing gain of the spectrum sharing SDMA is (J ? 1)/J__times less than that of the non-spectrum sharing SDMA only using orthogonal beamforming, whereas no loss in multiuser diversity gain. Although the spectrum sharing SDMA always has lower throughput compared to the non-spectrum sharing SDMA in the non-coexistence scenario, it offers an intriguing opportunity to reuse spectrum already allocated to other coexisting systems.

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