Robust Multi-class Signaling Overload Control for Wireless Switches

Mobile Switching Centers (MSCs) in wireless telecommunication networks must implement signaling overload controls to maintain acceptable performance during periods of high load especially due to fast changing hot spots resulting from user mobility. An MSC’s signaling load comprises a variety of service requests, some more important than the others, and it must treat them differentially under overload conditions. We propose multi-class overload control algorithms that are highly reactive to sudden bursts of signaling load and maintain high performance under a wide range of overload conditions as well. First, we introduce the concept of equivalent system load measures to convert the system load measures associated with different classes of traffic into a single measure with respect to a pre-defined base class. We use this concept to develop three multi-class overload detection and measurement algorithms. Next, we develop a new algorithm for partitioning the allowable equivalent system load across multiple traffic classes, using a strict priority scheme. Using simulations of call flows from mobile telecommunications standards, we compare different multi-class overload algorithms under a variety of overload conditions. Our simulation results indicate that our algorithm that measures system load using a combination of request acceptance rate and processor occupancy, provides highly reactive and robust overload control. Last, for the purpose of making the overload control algorithms more robust, we propose a measurement-based simple regression technique to dynamically estimate key system parameters. We find that estimates derived in this manner converge rapidly to their true values.