QoE-driven cross-layer optimization for high speed downlink packet access

This paper proposes a Quality of Experience (QoE) based cross-layer design (CLD) framework for High Speed Downlink Packet Access (HSDPA). The proposed scheme aims at maximizing the user satisfaction by taking advantage of the link adaptation mechanism of HSDPA and the rate adaptation capability of multimedia applications. The main contributions of the paper are as follows. First, we describe the multiuser rate region of HSDPA by constructing a long-term radio link layer model. Next, we formulate multimedia QoE by constructing long-term utility functions, describe the multiuser utility space and derive its properties. We show analytically that the maximization of the sum of utility (max-MOS) can be efficiently solved by a fast greedy algorithm which searches only through the boundary of the utility space. We investigate two alternatives to the max-MOS approach, which introduce additional fairness in the system. We compare our proposed QoE-based cross layer optimization schemes to a system that is configured to maximize the overall throughput. For the sake of complete- ness, we also compare our approaches to a non-optimized HSDPA system. The performance comparison is made by simulation using a software implementation of an actually deployed HSDPA system. Results show that our QoE-based approach leads to significantly improved user perceived quality compared to the other approaches.