Multilevel millimeter wave beamforming for wireless backhaul

Due to the projected increased demand for high data rate mobile services, interest has grown in new cellular network architectures such as a tiered networks. This paper proposes a beam searching algorithm and a codebook design for multilevel beamforming in outdoor millimeter wave communication systems. In an outdoor millimeter wave scenario, the received signal suffers from severe path loss and various attenuation factors. Beamforming is an essential component to establish the wireless link in 60GHz up to 80GHz. A millimeter wave beamforming method based on joint transmitter-receiver searching of an adaptive codebook is described. To reduce search complexity, an adaptive beam width beamforming technique is developed based on a sub-array method using squinting angles. A multilevel codebook having a hierarchical tree-structure on different beam width is adaptively designed. The performance of the proposed codebook design is analyzed, and the joint search algorithm is compared with other search methods. The proposed search method and the codebook design show performance improvement with small complexity.