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Intellectual Merit

In this proposal, we planned to investigate algorithms and protocols to support efficient data services with the TV White Space spectrum. The main challenge is that the range of a TV White Space cell is large, i.e., in the order of a few hundred meters, due to the longer propagation distances of the TV White Space frequency. Therefore, the Medium Access Control (MAC) protocol has to be scalable to a few hundred of connected devices, which means that the current Wi-Fi protocol cannot be borrowed.

We solved this problem by inventing a novel method, namely the Analog Bloom Filter (ABF), With ABF, the base station or the router may periodically designate some resources, i.e., some subcarriers in one or a few OFDM symbols. The resources are used to support a set of orthogonal bases, such as the original OFDM subcarriers or the Zadoff-Chu sequence modulated on the subcarriers. All devices that just turned active may transmit signals on such resources simultaneously on multiple randomly selected bases; all other devices remain silent. The base station then runs a demodulation algorithm to learn which devices that have transmitted signals. Therefore, with very low overhead, ABF solves the key problem in the MAC layer: how to know which devices are active and need to transmit data? With this information, the base station can schedule data transmissions optimally. A version of ABF has been implemented on Microsoft SORA software-defined radio and has been experimentally proven to outperform existing solutions significantly. We also note that ABF is applicable to all wireless networks as the MAC layer solution, especially medium or large networks, such as the TV White Space as well as the cellular networks.

In addition, according to our original plan, we also investigated a number of other issues, including Error Estimation Code (EEC), coping with wireless interference, efficient partial packet recovery, etc. We also looked into a number of security problems in current Wi-Fi networks that may also present in TV White Space networks.