Wireless Downlink Scheduling with Deadline Constraint for Realistic Channel Observation Environment

Abstract

Deadline-constrained wireless downlink transmissions,which have been widely used for a variety of real-time communication services that are related to the national economy and the people's livelihood,require each packet to be delivered in an ultra-reliable fashion within a strict delivery deadline.However,the base station (BS) cannot fully observe the channel state between itself and each device,and can be aware of the channel state for a device only when the BS receives a feedback from this device.This realistic channel observation environment makes the design of deadline-constrained downlink scheduling more challengeable.This paper aims to deal with this issue by allowing the BS to determine the transmission priority based on the packet information and partially-observable channel states.This paper uses an infinite-horizon partially observable Markov decision process (POMDP) to model the downlink transmission by only considering the head-of-line packets,but finding an optimal or near-optimal strategy for this model is computationally infeasible.As such,this paper proposes a suboptimal strategy with low complexity using the Q-function Markov decision process (QMDP) for the finite-horizon problems,and further proposes a simpler heuristic strategy.Simulation results demonstrate the performance advantage of the proposed strategies over baselines in various network scenarios,and indicate that the partial observability on the channel states indeed has a significant impact on the throughput performance.

Keywords

• deadline constraint|downlink transmission strategies|partially observable markov decision process|throughput