| Transmit-Nulling SDMA for Coexistence with Fixed Wireless Service |
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Han-Shin Jo1, Cheol Mun2 |
1Department of Electrical and Computer Engineering, The University of Texas at Austin
2Department of Information and Communications Engineering, Chungju National University |
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| Abstract |
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This paper proposes a systematic design for a precoding codebook for a transmit-ing space-division multiple access (TN-SDMA) sharing spectrum with existing fixed wireless service (FWS). Based on an estimated direction angle of a victim FWS system, an interfering transmitter adaptively constructs a codebook, forming a transmit in the direction angle, while satisfying orthogonal beamforming constraints. Sum throughput results indicate that the throughput loss of TN-SDMA relative to a practical SDMA, called per user unitary and rate control ($PU^2RC$), is lower at larger number of transmission antennas, lower signal-to-noise ratio, or a smaller number of users. In particular, a small loss (12% throughput loss) is provided for practical system parameters. Spectrum sharing results confirm that TNSDMA efficiently shares spectrum with FWS systems by reducing protection distance to more than 66 %. Although a TN-SDMA system always has lower throughput compared to $PU^2RC$ in non-coexistence scenarios; it offers an intriguing opportunity to re-use a spectrum already allocated to an FWS. |
| Key words:
SDMA, Orthogonal Beamforming, Transmit-Nulling, Spectrum Sharing |
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