Omnidirectional Beamforming Based on Complete Complementary Codes for Uniform Rectangular Array

In a cellular system, the base station needs to broadcast the common signals cell-wide. In this paper, we study how a multiple-input multiple-output (MIMO) system can achieve omnidirectional beamforming to maximize the coverage for common signals. We consider a uniform rectangular array (URA) configuration, since for a massive MIMO a URA would be easier to deploy than uniform linear array (ULA). We construct a rank-P beamformer based on the complete complementary codes (CCCs) for a general $P\times Q(P\leq Q)$ URA. We prove that such CCCs-based scheme can obtain P beamforming vectors to generate a perfectly omnidirectional radiation beampattern. Combined with the space-time block coding (STBC), our design can provide optimum coverage for the common messages.