Performance Evaluation of Mixed Traffic Schedulers in OFDMA Networks

Orthogonal Frequency Division Multiple Access based 4G cellular systems are designed to support different types of traffic through packet switching only. Hence, packet schedulers are important in increasing Real-Time (RT) traffic capacity as well as non Real-Time (nRT) data throughput of these networks without violating control channel and Quality of Service (QoS) constraints. Increasing capacity and maintaining QoS being conflicting design objectives, a desired Mixed Traffic Scheduler (MTS) algorithm is expected to yield a suitable trade-off between them. In order to identify such an algorithm for any ratio of RT and nRT users in a cell, in this paper, we compare the performance of certain MTS algorithms in terms of number of supportable users, data throughput, control channel usage, and resource usage. We propose two MTS algorithms which treat voice and video as a single traffic class. These are: (1) dynamic packet scheduling and (2) a new limited Joint Time Frequency (JTF) scheduling. These algorithms are compared with known ones like Modified Largest Weighted Delay First (Andrews et al. in IEEE Commun Mag 39(2):150–154, 2001) and SP-Dynamic (SemiPersistent for VoIP and Dynamic for Video) (Muntean and Otesteanu 2011). Impact of bundling voice and video packets on the performance of the algorithms is also investigated. Extensive system level simulations show that in addition to 14 video users per MHz, the proposed JTF scheduling with bundled VoIP and video packets can support 57.5 % more VoIP users per MHZ than the 3GPP requirement for only VoIP traffic (ITU-R 2008).