Cell discovery is the procedure in which a user equipment (UE) finds a suitable base station (BS) to establish a communication link. When beamforming with antenna arrays is done at both transmitter and receiver, cell discovery in mm wave systems also involves finding the correct angle of arrival – angle of departure alignment between the UE and the detected BS. First, we consider the single BS scenario and present the mathematical model for the cell discovery problem. We present the details of the beam sweeping based techniques and explain the beam combining scheme to reduce the training overhead. We analytically characterize the performance of energy detector at the UE for both beam sweeping and beam combining methods under some channel assumptions. Further, we consider the multiple BS case where BSs transmit synchronization signals along with directional beamforming. We analyze the performance of the energy detector in this case as well. We finally present simulation studies with channels generated using generic mm wave channel emulators and draw inferences on the role of various parameters on the cell discovery performance.

小区发现是用户设备（UE）找到合适的基站（BS）以建立通信链路的过程。当在发射器和接收器上使用天线阵列进行波束成形时，毫米波系统中的小区发现还涉及找到正确的到达角 - UE 与检测到的 BS 之间的离开角对齐。首先，我们考虑单个 BS 场景并提出小区发现问题的数学模型。我们介绍了基于波束扫描的技术的细节，并解释了波束组合方案以减少训练开销。在某些信道假设下，我们针对波束扫描和波束组合方法分析表征了 UE 处能量检测器的性能。更远，我们考虑多个 BS 的情况，其中 BS 发送同步信号以及定向波束成形。我们也分析了这种情况下能量检测器的性能。我们最终展示了使用通用毫米波信道仿真器生成的信道的仿真研究，并推断了各种参数对小区发现性能的作用。