MIMO Channel Capacity and Detectors with 1-bit ADC
The use of low resolution and especially one-bit ADCs radically changes both the theory and practice of communication. For example, the capacity maximizing transmit signals are discrete. This is in contrast with unquantized MIMO systems where the optimal input distribution is continuous. Although it is finite-dimensional, finding the optimal discrete input distribution is a challenging problem that depends on the CSIT and CSIR. In addition to capacity analysis, it is also interesting to investigate practical detection algorithms using one-bit ADCs, especially for massive MIMO systems.
We investigated the capacity of MIMO system in which a one-bit ADC is used for each in-phase and quadrature baseband received signal. We studied the channel capacity of the MIMO system with one-bit ADCs with channel state information at the transmitter. We provided bounds at infinite and finite SNR. We found that simple channel inversion precoding is nearly optimal if the channel has full row rank. If the channel is low rank, we proposed a new precoding method achieving the capacity at high SNR.
For detection algorithms using one-bit ADCs in massive MIMO systems, we implemented near maximum-likelihood (nML) detectors using convex optimization techniques for frequency flat fading channels. The performance of proposed detectors is similar to that of the ML detector with significantly reduced complexity. The detectors also can be easily incorporated with off-the-shelf channel coding techniques. For wideband frequency selective channels, we derived achievable rates of linear combiners taking MMSE channel estimation into account. It has shown that simple linear combiners work even with one-bit ADCs for massive MIMO, and frequency selectivity actually helps increasing achievable rates.
J. Mo, and R. W. Heath, Jr., “High SNR Capacity of Millimeter Wave MIMO Systems with One-Bit Quantization,” Information Theory and Applications Workshop (ITA), San Diego, CA, Feb. 2014.
J. Mo, and R. W. Heath, Jr., “Capacity Analysis of One-Bit Quantized MIMO Systems with Transmitter Channel State Information,” in IEEE Transactions on Signal Processing, vol. 63, no.20, pp. 5498-5512, Oct. 2015.
J. Mo, P. Schniter, N. G. Prelcic and R. W. Heath, Jr., “Channel Estimation in Millimeter Wave MIMO Systems with One-Bit Quantization,” 2014 Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, Nov. 2014.
J. Choi, J. Mo, and R. W. Heath, Jr., “Near Maximum-Likelihood Detector and Channel Estimator for Uplink Multiuser Massive MIMO Systems with One-Bit ADCs,” submitted to IEEE Transactions on Communications, Jul., 2015.
C. Mollén, J. Choi, E. Larsson, and R. W. Heath, Jr., “One-Bit ADCs in Wideband Massive MIMO Systems with OFDM Transmission,” to appear in Proc. of IEEE International Conference on Acoustics, Speech and Signal Processing, Mar. 2016.
C. Mollén, J. Choi, E. Larsson, and R. W. Heath, Jr., “Performance of Linear Receivers for Wideband Massive MIMO with One-Bit ADCs,” to appear in International ITG Workshop on Smart Antennas (WSA 2016), Mar. 2016.
The work was supported in part by the National Science Foundation under Grant Nos. NSF-CCF-1218338, NSF-CCF-1319556, NSF-CCF-1018368 and NSF-CCF-1218754.