On Integer-Forcing Hybrid Precoding for Downlink Millimeter Wave MIMO Systems

This paper studies a new integer-forcing (IF) hybrid precoding scheme for downlink millimeter-wave MIMO systems. First, we formulate the partially connected hybrid precoding optimization problem. Then, we decompose the problem into separate analog precoding/combining and digital precoding components. To boost the spectral efficiency, we develop an IF method for the digital precoder. Due to the unit-modulus constraint, the analog precoder is more challenging to optimize, for which we employ an element-iteration (EI) algorithm. Numerical results demonstrate that the proposed IF hybrid precoding scheme, which combines analog and digital precoding, approaches the performance upper bound of partially-connected hybrid precoding architectures. It achieves substantial performance gains over existing hybrid precoding schemes in both spectral efficiency and bit error rate (BER).