Delay-aware fair scheduling in relay-assisted high-speed railway networks

In this paper, we consider delay-aware fair downlink scheduling with heterogeneous packet arrivals and delay requirements for a relay-assisted high-speed railway (HSR) network. Data packets from multi-users requests are delivered via the two-hop network architecture to achieve a high data transmission rate instead of direct transmission. Our objective is to find a policy that minimizes the average weighted end-to-end (e2e) delay through packet scheduling under the user fairness constraint. The policy is a two-dimensional vector with the scheduling indexes in the two-hop link as its elements. We model the problem as an infinite-horizon average reward constrained Markov decision problem (CMDP) when the data arrival process and the channel process are Markovian. To address the challenge of huge complexity of MDP problems, we propose a heuristic and low-complexity algorithm. Simulation results show that the proposed algorithm outperforms the other existing schemes in terms of average weighted delay performance and user fairness.