SNOW: Sensor network over white spaces

Wireless sensor networks (WSNs) face significant scalabil-ity challenges due to the proliferation of wide-Area wireless monitoring and control systems that require thousands of sensors to be connected over long distances. Due to their short communication range, existing WSN technologies such as those based on IEEE 802.15.4 form many-hop mesh net-works complicating the protocol design and network deploy-ment. To address this limitation, we propose a scalable sen-sor network architecture-called Sensor Network Over White Spaces (SNOW)-by exploiting the TV white spaces. Many WSN applications need low data rate, low power operation, and scalability in terms of geographic areas and the num-ber of nodes. The long communication range of white space radios significantly increases the chances of packet collision at the base station. We achieve scalability and energy ef-ficiency by splitting channels into narrowband orthogonal subcarriers and enabling packet receptions on the subcar-riers in parallel with a single radio. The physical layer of SNOW is designed through a distributed implementation of OFDM that enables distinct orthogonal signals from dis-tributed nodes. Its MAC protocol handles subcarrier allo-cation among the nodes and transmission scheduling. We implement SNOW in GNU radio using USRP devices. Ex-periments demonstrate that it can correctly decode in less than 0.1ms multiple packets received in parallel at differ-ent subcarriers, thus drastically enhancing the scalability of WSN.