Pilot-based Sequence Design to Overcome a Blockage in mmWave Cellular Systems

The deployment of relay stations (RS) has been regarded as a possible solution to the blocking problem in millimeter wave (mmWave) communication systems. In this paper, we discuss issues to be considered in relay-assisted mmWave cellular systems based on orthogonal frequency division multiplexing. We describe a pilot-based training method to achieve effective RS selection during blockage. We propose two different types of pilot sequences, which allow mobile stations to distinguish pilot sources in a multi-cell multi-relay environment: pilot signals based on Zadoff-Chu sequence (PS1) and m-sequence (PS2). Correlation properties of PS1 and PS2 are derived and compared with that of the conventional sequence (Gold sequence). A blocking model is used to verify the properties, constraints, advantages, and disadvantages of the proposed pilot sequences in the RS-assisted mmWave cellular system.