Mobile real-time group communication service
INFOCOM'10 Proceedings of the 29th conference on Information communications
Delay-Sensitive Mobile Group Services Over Cellular Networks
Wireless Personal Communications: An International Journal
A scalable framework for mobile real-time group communication services
Computer Networks: The International Journal of Computer and Telecommunications Networking
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The problem of searching for mobile users in cellular networks is addressed in this study. Previous studies addressing this issue have focused on the problem of searching for a single user. As it is shown in this study, the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard. {\bf When the potential locations of different users overlap, the derivation of an optimal concurrent search for many independent users from a set of optimal single user searches is NP-hard}. In reality, a cellular network has to serve many competing search requests sharing a limited bandwidth. Since the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard, this study proposes a heuristic algorithm, that is optimal for most probable cases, and its worst case running time complexity is $O(n(\log{n} + C\log{C}))$, where $n$ is the number of mobile users that must be found, and $C$ is the number of their potential locations. {\bf The approximation ratio of the proposed search algorithm is less than 2}.