Optimizing Synchronization Signal Block Transmissions for Sum-Rate Maximization in Sub-Connected Hybrid Beamforming Systems

Fifth-generation millimeter wave (mmWave) systems rely on sub-connected (SC) hybrid beamforming architecture due to low power consumption and reduced hardware complexity. These systems require directional beamforming to establish communication between the base station (BS) and user equipment (UE). Typically, the communication between BS and UE occurs in two phases. In the first namely initial access (IA) phase, BS utilizes spatial beam search using synchronization signal (SS) blocks for link establishment and is followed by data transmission in the second phase. As per the 3GPP standard for 5G NR systems, existing approaches utilize a maximum IA duration of 5ms corresponding to the transmission of 64 SS blocks for beam search. The maximum transmission of SS blocks results in a significant delay in data transmission to the user. This work proposes an optimized value of the number of SS block transmissions to achieve a higher sum-rate in an SC hybrid mmWave system. Simulation results demonstrate that an optimized value of SS block transmission results in faster user discovery and yields more time for data transmission. This in turn results in an improved performance of the SC hybrid beamforming systems in terms of enhanced sum-rate capacity and reduced initial beam acquisition time.