Hybrid Precoding and Combining for Full-Duplex Millimeter Wave Communication

Full-duplex (FD) communication is an enabling technology to increase spectral efficiency. The self- interference (SI) resulting from sharing time and frequency resources between different transceivers in FD mode must, however, be managed. At millimeter wave (mmWave) frequencies, FD communication is different than at sub-6 GHz frequencies, because non conventional MIMO architectures and large antenna arrays are often used. In this paper, we address a major challenge for FD mmWave systems: the design of hybrid precoders and combiners that simultaneously maximize the sum spectral efficiency and cancel the SI in the analog domain, to keep control of the signal level at the input of the analog- to-digital converters (ADCs). The optimal joint design is a very difficult problem, since it involves the optimization of eight precoding/combining matrices with several constraints, some of them non convex. We derive two suboptimal solutions which exhibit near- optimum spectral efficiency and significantly outperform prior work in terms of SI cancelation.