How Multi-Hop Relaying in mmWave Communications Improves Uplink Network Latency

For current and future wireless networks, applications such as Industrial Internet of Things (IoT) and vehicle-to-vehicle (V2V) communications are strictly delay-sensitive, requiring low latency. In order to minimize end-to-end delay of each device in such machine-to-machine (M2M) communications, we propose buffer-aided multi-hop relaying networks in the uplink, for high data rates at mmWave carrier frequencies. We formulate the problem as a multi-tier queueing system, and by leveraging stochastic geometry, we present a tractable analytical framework to investigate the signal-to-interference-plus-noise-ratio (SINR) distribution of devices at each tier, thereby computing the expected delay and delay outage probabilities for each device, which are key metrics to characterize overall network delay performance. Numerical results based on multiple cells in a dense urban scenario validate analytical results, and show that our minimum-delay relaying scheme achieves significant lower average end-to- end delay and higher effective capacity than direct association or a state-of-art max-SINR relaying scheme.