CopSearch: Asymmetric Duty Cycle Neighbor Discovery Protocol for Mobile Devices
Maotian Zhang, Panlong Yang, Lei Zhang, Yubo Yan and Laixian Peng
We investigate the neighbor discovery problem in asymmetric low duty cycle mobile networks. Previous studies either fail to ensure bounded discovery time in worst case or cannot provide satisfiable performance in average case. In this paper, we propose an asynchronous and asymmetric neighbor discovery protocol called CopSearch. By choosing the position of three different active slots, the anchor slot, the probe slot and the prime slot, CopSearch establishes a new neighbor discovery schedule. CopSearch employs single collaborative prime for fast neighbor discovery and ensures discovery in bounded time which is less than or equal to (1 + 2/α)2x1x2, where 1/x1,1/x2 are duty cycles of two mobile devices and α is a regulatory factor. We present an evaluation of CopSearch, and compare the performance of CopSearch with that of existing protocols like Disco , U-Connect  and Searchlight , showing that CopSearch achieves considerable improvement (at least 30%) on the worst-case discovery latency over existing approaches in asymmetric case.
Keywords: Neighbor discovery, low duty cycle, energy efficiency, asymmetric networks, prime-based approach, mobile networks, wireless sensor networks