Scheduling Strategy for Multimedia Heterogeneous High-Speed Train Networks

Recently, the high-speed train has been recognized as a fast and popular public transportation system that brings significant convenience to passengers. How to efficiently provide passengers broadband mobile services, such as voice over IP (VoIP) and multimedia services, is receiving increasing attention. To fulfill passengers' diverse demands, we consider a heterogeneous network (HetNet) structure consisting of trackside access points (TAPs) and base stations (BSs) in a high-speed rail communication system (HRCS). First, we formulate a service-scheduling problem aiming at minimizing the end-to-end delay of VoIP and multimedia services as an infinite-horizon time-average expected delay constraint Markov decision process (CMDP) model. In particular, to provide a suitable scheduling selection scheme, this paper proposes a hybrid scheduling strategy to satisfy various delay requirements. Second, we utilize the martingale theory to obtain the theoretic value of the end-to-end delay bounds under two kinds of scheduling mechanisms: first in first out (FIFO) and earliest deadline first (EDF). In the simulation, we use three kinds of real wireless data traces, namely, VoIP, gaming, and User Datagram Protocol (UDP), to evaluate our algorithms by using the Nakagami-mfading channel. From the results, we verify the optimality of the proposed scheduling algorithm in average end-to-end delay performance over FIFO and EDF and the working principle of the hybrid scheduling strategy. In addition, the martingale end-to-end delay bounds are remarkably tight to the real data trace simulation results.