Low complexity cross-layer design with packet dependent scheduling for heterogeneous traffic in multiuser OFDM systems

We propose an adaptive cross-layer design for the downlink multiuser orthogonal frequency division multiplexing (OFDM) systems, to maximize the weighted sum capacity of all users, where each user has multiple heterogeneous traffic queues simultaneously. A packet dependent (PD) scheduling scheme is employed at the medium access control (MAC) layer, which determines the packet transmission order by assigning different weights to different packets, and is shown by simulations more efficient than the previous methods where all packets in a queue have the same weight. The weight design in PD scheduling considers the delay, size and quality of service (QoS) priority level of packets. Each user weight employed in resource allocation at the physical (PHY) layer is obtained by summing up the weights of selected packets for the user. By properly choosing the number of packets used for weight calculation, the proposed cross-layer design requires a much lower overall complexity than the conventional queue based designs. It is also proven to achieve the maximum system stability region. Furthermore, simulation results show that the proposed suboptimal resource allocation algorithm provides a near-optimal performance while requiring a relatively low complexity.