Scheduling of Real-Time Traffic in Mobile Packet Switched Core Networks

Interworking between UMTS (Universal Mobile Telecommunications System) and external networks is an important concept for fixed-mobile convergence as well as for next generation network. In order to achieve end-to-end QoS (Quality of Service) for broadband multimedia real-time services, DiffServ (Differentiated Services) mechanism should be used as QoS model and mapping of DiffServ Code Points (DSCP) into UMTS traffic classes should be applied to get efficient PHB (Per Hop Behaviour) configurations. According to the 3GPP specifications, standard QoS mapping between IP QoS classes and UMTS services authorizes both voice and video telephony to be mapped to the same QoS class. Since network resources are limited, if any segment of the network is congested, video traffic can cause significant delay of voice packets when aggregating both together to the same PHB group. In the context of QoS assurance is analyzed preposition of using LLQ (Low Latency Queueing) scheduler with the main idea of mapping voice and video telephony to different PHB groups. Within LLQ, PQ (Priority Queuing) is used for scheduling of both voice and video telephony. To proof the idea, simulation study was performed using NS-2 (Network Simulator Version 2) where changes were done within standard LLQ implementation in order to support scheduling of two queues with highest priority. New concept was compared with other schedulers like PQ (Priority Queuing), WFQ (Weighted Fair Queuing) and WRR (Weighted Round Robin). The obtained results were statistically processed using SPSS (Statistical Package for the Social Sciences) version 17.0. Summarizing research results, avenues of future research are identified.