In order to cope with the expected future growth of mobile broadband traffic, network operators will be forced to dramatically increase their Radio Access Network (RAN) capacities. As neither the purchase of additional spectrum nor the deployment of new radio technologies will be able to solve this problem in the long run, we focus on a strategy for offloading the macro-infrastructure by introducing small cell sites of high spatial density (e.g., femto-cells) or by shifting significant volumes of traffic towards connections operating in the unlicensed bands (e.g., IEEE 802.11 Wi-Fi). In this paper, we address related coverage and interference issues, based on a recent measurement campaign conducted in a representative district of the city of Vienna, Austria. We provide fine-grained coverage results for both Wi-Fi and 3G which may serve as a reliable starting point for analyzing the feasibility and efficiency of future nomadic and mobile offloading strategies. Moreover, our results demonstrate that the signal strengths of user provided indoor Wi-Fi access points most often match or even exceed those of the macro-cell infrastructure in urban outdoor environments.
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