Optimizing outdoor White-Fi networks in TV white spaces
Sneihil Gopal, Sanjit K. Kaul, Sumit Roy · 2016
White-Fi networks are CSMA/CA networks that are deployed in TV white spaces. In outdoor deployments, nodes in such networks can have a communication range of several kilometers. As a result, nodes in range have heterogeneous channel gains from the TV transmitters. Also, they have heterogeneous channel gains to TV receivers. While the nodes in the network may be configured as an ad hoc network of peers or in infrastructure (access point based) mode, they use the 802.11 distributed control function (DCF) to gain access to the medium. We investigate optimization of the DCF throughput in such a White-Fi network when there are restrictions on the aggregate interference (specifically, we consider its expectation and maximum) that it can create at TV receivers. To gain insights into the interplay between the TV networks and the White-Fi network, we allow nodes in the White-Fi network to choose their payload rates, access probabilities, overhead transmission rates, and channels. The resulting optimization problem is non-convex. Our proposed solution methodology obtains large gains (about 200% for 50 nodes) in throughput over a baseline that respects restrictions on aggregate interference but assigns the same power and probability of medium access, across available channels, to all nodes in the network.