Fair Scheduling in OFDMA-based Wireless Systems with QoS Constraints

In this work we consider the problem of downlink resource allocation for proportional fairness of long term received rates of data users and quality of service for real time sessions in an OFDMA-based wireless system. The base station allocates available power and bandwidth to individual users based on long term average received rates, QoS based rate constraints and channel conditions. We solve the underlying constrained optimization problem and propose an algorithm that achieves the optimal allocation. Numerical evaluation results show that the proposed algorithm provides better QoS to voice and video sessions while providing more and fair rates to data users in comparison with existing schemes.

💡 Research Summary

The paper addresses downlink resource allocation in OFDMA‑based wireless networks (specifically IEEE 802.16/WiMAX) with the dual goal of providing long‑term proportional fairness to data users while guaranteeing Quality‑of‑Service (QoS) constraints for real‑time traffic (voice and video). The authors model the system as a single base station serving N users, each demanding a single traffic type. Total bandwidth W and total transmit power P are divided among N sub‑channels (each of width Wsub). The channel gain for user i at time t, hi(t), includes path loss, shadowing, and fast fading; noise plus interference density is N0. The achievable rate on a sub‑channel is approximated by a Shannon‑type formula

 ri(wi, pi) = wi log