Hybrid precoding codebook design in millimetre‐wave massive MIMO systems with low‐resolution phase shifters

Millimetre‐wave (mmWave) massive multiple‐input multiple‐output (MIMO) is one of the promising techniques for 5G wireless communications and beyond. Low‐resolution hybrid precoding using low‐resolution phase shifters (PSs) is considered to be promising for mmWave massive MIMO, since it can realize an acceptable performance with significantly reduced energy consumption. However, to realize accurate channel state information acquisition, the traditional channel feedback codebooks that quantize the channel with high resolution are not suitable for low‐resolution hybrid precoding. To solve this problem, angle‐based codebook is proposed here. In the proposed codebook, the analog codebook is designed based on the channel angle‐of‐departures (AoDs) and the digital codebook is generated by the random vector quantization. Specifically, the analog codewords are optimized by a neighbour search algorithm under the constraint of low‐resolution PSs. These analog codewords are designed to be aligned with channel AoDs. In this way, they can remain unchanged in a much larger time scale, since the angle‐coherence time is much longer than the channel‐coherence time. Therefore, the channel feedback overhead can be significantly reduced. Both theoretical analyses and simulation results illustrate that the proposed codebook can achieve the acceptable achievable rate performance with low channel feedback overhead.