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October 8, 2010IEEE Transactions on Wireless Communications6,585 citations

Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas

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TMThomas L. Marzetta

Key Points

  • To analyze the asymptotic performance and fundamental limits of multi-cell wireless networks when base stations deploy an unlimited number of antennas in time-division duplex operation.
  • Modeled a multi-cell system using time-division duplexing and reverse-link pilots for reciprocal forward- and reverse-link channel estimation.
  • Applied conjugate-transpose channel estimates as linear precoders on the forward link and linear combiners on the reverse link under channel fading (fast fading, log-normal shadow fading, and geometric attenuation).
  • Conducted an asymptotic multi-cellular analysis taking into account inter-cellular interference and channel-state information estimation errors as antenna count approaches infinity.
  • Uncorrelated thermal noise and fast fading effects completely vanish as the number of base station antennas tends to infinity.
  • Per-cell throughput and user capacity become independent of cell radius, spectral efficiency becomes independent of bandwidth, and required transmit energy per bit approaches zero.
  • Inter-cellular interference caused by the reuse of pilot sequences across neighboring cells (pilot contamination) persists as the sole impairment that does not vanish.

Abstract

A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.

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Cite This Study

Thomas L. Marzetta (2010) studied this question.

synapsesocial.com/papers/69df6e4dd5404a0bea5931b4https://doi.org/10.1109/twc.2010.092810.091092
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