Full-Duplex SIMO Relaying for Machine-Type Communications in Cellular Networks

Abstract

To address massive access in machine-type communication (MTC), we consider in-band full- duplex (IBFD) relays to aggregate MTC packets. IBFD allows devices to receive and transmit concurrently on the same frequency band, potentially doubling the spectral efficiency. On the downside, the use of IBFD raises the interference due to an increased density of simultaneously transmitting nodes. This paper deals with a key trade-off between the increased spectral efficiency and interference in utilizing IBFD uplink relays in a densely deployed MTC network. Using stochastic geometry, we develop a framework to evaluate the end-to-end outage probability and uplink data aggregation rate. The model consists of MTC devices and IBFD relay nodes that forward MTC packets to base stations (BSs) over single-input-multiple-output channels. The BSs employ linear zero-forcing filters to cancel the interference from their associated relay nodes which may transmit simultaneously on the same frequency band. We show the somewhat surprising result that IBFD relaying does not lead to performance gains over half-duplex relays, when devices and relays are independently and homogeneously distributed in space.