Massive MIMO: How many antennas do we need?

Jakob Hoydis (1) , Stephan ten Brink (2) , Merouane Debbah (3)

1 E3S - Supélec Sciences des Systèmes
2 Alcatel Lucent Bell Labs
3 Chaire Radio Flexible - Chaire Radio Flexible Alcatel-Lucent/Supélec

We consider a multicell MIMO uplink channel where each base station (BS) is equipped with a large number of antennas N. The BSs are assumed to estimate their channels based on pilot sequences sent by the user terminals (UTs). Recent work has shown that, as N grows infinitely large, (i) the simplest form of user detection, i.e., the matched filter (MF), becomes optimal, (ii) the transmit power per UT can be made arbitrarily small, (iii) the system performance is limited by pilot contamination. The aim of this paper is to assess to which extent the above conclusions hold true for large, but finite N. In particular, we derive how many antennas per UT are needed to achieve \eta % of the ultimate performance. We then study how much can be gained through more sophisticated minimum-mean-square-error (MMSE) detection and how many more antennas are needed with the MF to achieve the same performance. Our analysis relies on novel results from random matrix theory which allow us to derive tight approximations of achievable rates with a class of linear receivers.

Keywords: large-scale MIMO; massive MIMO; large antenna arrays; antenna correlation; multi-cell; pilot contamination; linear receivers; uplink; path loss; physical channel model

Domains: Networking and Internet Architecture [cs.NI]; Information Theory [cs.IT]; Information Theory [math.IT]

Jakob Hoydis, Stephan ten Brink, Merouane Debbah. Massive MIMO: How many antennas do we need?. Forty-ninth Annual Allerton Conference on Communication, Control, and Computing (Allerton'11), Sep 2011, Urbana-Champaign, IL, United States. 6 p. ⟨hal-00648031⟩