Optimal Beam Separation in Auxiliary Beam Pair-based Initial Access in mmWave D2D Networks

In this paper, we propose the optimization of beam separation in auxiliary beam pair (ABP) schemes to optimize the device discovery process in a millimeter wave (mmWave) device-to-device (D2D) network. Specifically, two beams are generated both at the transmitter (TX) and receiver (RX) for user detection through directional beamforming (BF). BF is employed by either splitting the uniform linear array into two halves (Auxiliary-Half (AH) scheme) or utilizing the whole antenna array (Auxiliary-Full (AF) scheme). It is shown that the separation between two beams plays a vital role in device discovery. Optimum values of probability of miss detection (PMD) and discovery delay (DD) are obtained for a suitable combination of beam pair separation at both TX and RX. Moreover, it is shown that the narrowest possible beams at TX and RX do not improve the detection probability in either AH or AF schemes.