Exploiting Channel Hardening and Sphere Hardening for Large Antenna Arrays

摘要

For reliable and low latency communications, we consider encoding the data streams across the spatial channels instead of transmitting independent data stream over each spatial channel, and also instead of encoding the data across time. Using a stochastic MIMO channel model, we re-examine implications of using large Massive Multiple Input Multiple Output (MIMO) antenna arrays, such as those that extend across a large surface. The effects of additive noise at receivers, with large number of antennas, for Massive MIMO systems have not been fully addressed. We present a system model that achieves both channel hardening and noise sphere hardening. With channel hardening, the receiver does not need channel state information at the receiver (CSIR), for a sufficiently large transmit array. With receiver noise sphere hardening, the variations of the length of the noise vector is constrained to very small values, enabling error free communication above an average signal-to-noise ratio (SNR), for sufficiently large receive antenna array. Such systems are advantageous for applications with low latency requirements where at a given time instant, data can be received with improved reliability.