Pilot Sequence Design for mmWave Cellular Systems With Relay Stations in the Presence of Blockage

Abstract

Due to short wavelength and weak diffraction ability, millimeter-wave (mmWave) signals are highly susceptible to blockage, which results in significant degradation in received signal power. As a possible solution for overcoming the blockage problem in millimeter-wave communication systems, the deployment of a relay station (RS) has been considered in recent years. In this paper, we discuss the problems to be considered in a relay-assisted mmWave cellular system based on orthogonal frequency division multiplexing. We describe a frame structure and a pilot-based training method to achieve efficient RS selection during blockage. In addition, a method designed to overcome the inter-symbol interference problem caused by different symbol time offsets of pilot signals received from adjacent RSs in the relayassisted mmWave cellular system is discussed. Then, we propose two different types of pilot sequences that allow a mobile station to distinguish among the pilot sources in multi-cell multi-relay environments: pilot signals based on the Zadoff-Chu sequence (PS1) and pilot signals based on the m-sequence (PS2). The correlation property of PS2 is derived and compared with that of PS1 and another sequence (Gold sequence). Simulations are performed using a blockage model to verify the properties, constraints, and advantages and disadvantages of the proposed pilot sequences in RS-assisted mmWave cellular systems. INDEX TERMS Blockage, cellular system, mmWave, pilot sequence design, relay.

A Novel Constellation Modification Method for Harmonic Modulated MPSK Data Transmission in Millimeter Wave Communication

“…Thus, the huge available bandwidth offered by the mmWave band can provide the rates of multiple gigabit per second per user [2]. Despite the significant downsides of mmWave signals, such as limited coverage, signal blockages by obstacles, and severe signal attenuation caused by short wavelengths, it appears that the frequency band utilized to deliver high data rate traffic will inevitably be shifted to mmWave or even sub-terahertz (sub-THz) frequency bands [4], [5], [6]. Consequently, studies have been conducted on the mmWave band [7].…”