Multi-User Interference Suppression in Phased Arrays with Quantized Control in Millimeter Wave Communication Networks

In millimeter-wave communication networks, sidelobe leakage of phased array antennas can cause mutual interference to receiving devices, resulting in reduced network throughput. By optimizing the weights of antenna elements, nulls can be created to suppress the interference. However, commercial low-cost millimeter-wave phased arrays often not only lack amplitude control but also offer limited bits control. Therefore, interference suppression with highly quantized phase control is of great significance for practical applications of millimeter-wave communications. Existing algorithms for null steering and generation mainly consider continuous phase control which cannot adapt well to the quantized phase tuning for multi-user communications over the downlink. Moreover, the optimization of multiple nulls is inherently a discrete programming which is generally intractable. The authors propose a null generation algorithm for sole phase control based on the Levenberg-Marquardt algorithm. The algorithm takes into account phase quantization, making it convenient to implement wide and multiple nulls. Simulation results show that the algorithm can generate deep and wide nulls even with low phase resolution. Moreover, the algorithm is validated with Commercial Off-The-Shelf low-cost 60 GHz communication devices. Experimental results demonstrate that the algorithm achieves interference suppression up to 22.93 dB with a 4-bit phased array.