Analysis and Design of Low-Duty Protocol for Smartphone Neighbor Discovery

Abstract

An effective neighbor discovery service on smartphones is required for many emerging applications—from proximity-based interactions to opportunistic phone-to-phone collaborations. For a smartphone neighbor discovery service to be usable and attractive, it needs to meet two conflicting goals: 1) phones should discover neighbors fast enough (in seconds), and 2) the service’s energy footprint should be negligible so it can be “always on” while incurring little impact on battery life. Researchers have developed an impressive collection of neighbor discovery protocols to meet these two goals. By putting these protocols into concrete smartphones settings, we identify different key factors that limit their performance. Guided by our analysis, we focus on locally synchronized protocols, where phones use time information from nearby Wi-Fi Access Points (APs) to help neighbor discovery. By overcoming the key challenges for such protocols, especially, the scalability problem under increasing number of APs and neighbors, we design a new protocol, R2, that achieves low discovery delay ( $ seconds for at least 80 percent of all connections) with a low duty cycle (1 percent).