Finite-Blocklength Performance of Relay-Networks over Nakagami-m Channels

Wireless cooperative communications and relay networks can significantly improve the performance of fifth generation (5G) wireless networks, which aim at providing a wide range of time-sensitive multimedia services and applications by satisfying users' stringent requirements on the delay-bounded quality of service (QoS). Finite blocklength coding (FBC) is a promising candidate technique to support time-sensitive services in 5G wireless networks, where mobile users transmit short packets to upperbound the transmission delay of multimedia traffic. In this paper, we derive closed-form expressions for the coding rates of direct and relay transmissions, respectively, under the Nakagami-m fading channel in the finite blocklength regime. We compare decoding error probabilities, coding rates, and outage probabilities between direct and relay transmissions. Our comparison results show that while relay transmission yields a larger coding rate than that of direct transmissions under the Nakagami-m fading channel, the outage probability and error rate of relay transmissions are higher than those of direct transmissions. We also derive a closedform expression for the outage probability for relay transmissions with multiple parallel relays. Finally, we evaluate and validate our derived coding rates and outage probabilities for both direct and relay transmissions in the finite blocklength regime through numerical analyses.