Deploying carrier-grade WiFi: offload traffic, not money

WiFi data offloading provides a promising auxiliary to alleviate network congestion by diverting traffic from the cellular infrastructure onto WiFi access points (APs). Despite the importance and momentum of this method, the current deployment of APs by the carriers follows mostly a heuristic approach. In addition, the prevalent free-of-charge WiFi access approach may result in significant opportunity costs for the carriers as this traffic could yield non-negligible revenues. In this paper, we propose and study the problem of optimizing the deployment of WiFi offloading infrastructure, and pricing the offloading service with the goal of maximizing carrier profits. Addressing this problem is a prerequisite for the efficient integration of WiFi technology to next generation of cellular systems and the development of carrier-grade offloading solutions. Our framework considers a fundamental, intuitive model of carrier costs and revenues, and two demand models that predict how traffic will change in response to alteration in the price and the set of deployed APs. We present both analytical and approximate solutions for this intricate problem, and reveal how key network parameters shape the offloading benefits. Using a dataset of WiFi access patterns collected from real users, we evaluate the impact of offloading for different regional markets around the world. We find that in mature markets WiFi can help carriers reduce their costs, while charging users up to 50% lower than the cellular service. The gains are higher for small "virtual carriers" who resell other's mobile data services (up to a factor of 2). However, in less mature markets where the AP deployment or access costs are higher, deploying APs can actually lead to a net loss for the carrier. Our evaluation code is publicly available for the benefit of research community.