Mitigating Signaling Overhead From Multi-Mode Mobile Terminals

Modern cellular networks may be deployed using multiple radio-access-network technologies with multi-mode mobile terminals capable of selecting among different technologies. Such a network typically forms an overlay-underlay architecture where the underlay uses an older technology (e.g., 3G) while the overlay uses a newer technology (e.g., 4G). It has been observed that excessive signaling message updates can arise due to registration ping-pongs, and Idle-mode Signaling Reduction (ISR) has been introduced as a mechanism to reduce this update load. In this paper, we show that while ISR reduces update load, it also has the effect of increasing paging load. We investigate tradeoff between update and paging loads. Our analysis quantifies a threshold that is used to activate or deactivate ISR for each mobile terminal and results in significant signaling load reduction. We also develop a practical threshold-based algorithm that does not rely on knowledge of the structure of an overlay or terminal mobility.