Uplink Cross-Layer Scheduling with Differential QoS Requirements in OFDMA Systems

Bo Bai,Khaled Ben Letaief,Wei Chen,Zhigang Cao

doi:10.1155/2010/168357

Abstract

Fair and efficient scheduling is a key issue in cross-layer design for wireless communication systems, such as 3GPP LTE and WiMAX. However, few works have considered the multiaccess of the traffic with differential QoS requirements in wireless systems. In this paper, we will consider an OFDMA-based wireless system with four types of traffic associated with differential QoS requirements, namely, minimum reserved rate, maximum sustainable rate, maximum latency, and tolerant jitter. Given these QoS requirements, the traffic scheduling will be formulated into a cross-layer optimization problem, which is convex fortunately. By separating the power allocation through the waterfilling algorithm in each user, this problem will further reduce to a kind of continuous quadratic knapsack problem in the base station which yields low complexity. It is then demonstrated that the proposed cross-layer method cannot only guarantee the application layer QoS requirements, but also minimizes the integrated residual workload in the MAC layer. To further enhance the ability of QoS assurance in heavily loaded scenario, a call admission control scheme will also be proposed. The simulation results show that the QoS requirements for the four types of traffic are guaranteed effectively by the proposed algorithms.

Highlights

Orthogonal frequency-division multiple access (OFDMA) offers a very attractive solution in providing high performance and flexible deployment for broadband wireless access network
The problem of uplink traffic scheduling with differential QoS requirements in OFDMA systems was addressed in this paper
A cross-layer optimization methodology, which jointly considers the traffic arrival process and the wireless channel conditions, was adopted to achieve better QoS for the users accessing to a common base station

Summary

Introduction

Orthogonal frequency-division multiple access (OFDMA) offers a very attractive solution in providing high performance and flexible deployment for broadband wireless access network. The typical OFDMA systems in wireless communications are 3GPP LTE-based cellular system [4] and IEEE 802.16 protocol-based WiMAX system [5] These newly emerging systems provide a platform for applying the cross-layer resource allocation and scheduling technology. The integrated residual workload method is introduced to cover the above considerations By using this method, the resource allocation and traffic scheduling can be formulated into a cross-layer optimization problem under the transmission rate constraints, which is convex . According to the results in [18, 19], this time-frequency allocation problem can be solved with a low complexity At this context, an integrated residual workload minimization (IRWM) algorithm and a heuristic call admission control (CAC) algorithm are proposed as a framework of the resource management scheme for future OFDMA-based wireless access networks.

Cross-Layer Multiaccess Queuing Model

Optimal Scheduling Policy

Simulation Results

Conclusion