A self-adaptive scheduling (SAS) solution for enhancing VoIP service quality in OFDM-based mobile networks

To save signaling overhead, Semi-Persistent Scheduling (SPS) is the standard for delivering Voice-over-IP (VoIP) in OFDM-based mobile networks. But uncompressed or variable-size compressed VoIP packets are problematic for SPS because they spill over the assigned semi-persistent resource whenever the ROHC (Robust Header Compression) mechanism is in an initialization or reset period, propagating system latency and accumulating unnecessary signaling overhead. In response, we propose a Self-Adaptive Scheduling (SAS) algorithm, where dynamic scheduling is used as an adaptive mechanism to assist in scheduling oversized packets, triggered by buffer information already known to the system, without requiring dedicated signaling. To analyze the performance of our proposal in theory, we created a novel theoretical model to describe VoIP traffic considering the uncompressed voice state. This is, to our best knowledge, the first effort to model the effect of uncompressed packets on VoIP performance in mobile networks from the system-level point of view. Theoretical analysis and simulation experiments validate our proposal, demonstrating its ability to enhance the VoIP user experience for a minor signaling overhead cost.