Real-Time QoS in Enhanced 3G Cellular Packet Systems of a Shared Downlink Channel

Abstract

We propose a call (user) admission control (CAC) algorithm and a scheduling framework for real-time services in the enhanced third-generation (3G) cellular systems, e.g., WCDMA HSDPA or cdma2000 HDR systems, where multiple IP users share a time-slotted downlink packet channel in each cell. At the user or flow level, the CAC algorithm maximizes user accommodations under the QoS constraint, e.g., per-user expectation of profile rate, and the constraint of location-dependent resource availability. At the packet level, our scheduling framework, named maximum cost deduction (MCD), derives two algorithms - both are QoS-aware and channel-dependent: One is called real-time MCD (rt-MCD), which minimizes a delay-derived cost function of backlogged packets at the smallest timescale; the other is called non-real-time MCD (nrt-MCD), which balances between the real-time delay deduction and the non-real-time (i.e., large-timescale) per-user fairness. The cross-layer designed CAC and MCD algorithms exploit multi-user diversity based on online measured radio resource allocation. Together they provide high system efficiency and a balance between flow-level QoS (e.g. the aggregate goodput and the blocking rate of newly arrived users) and packet-level QoS (e.g., the packet queueing delay or loss). Extensive simulations and comparisons with the prior art show that our algorithms can deliver efficient real-time services and remain robust to different load scenarios that vary according to system dynamics and/or user mobility