The next generation of wireless networks will include software defined radios, cognitive radios, and multi-radio systems which will co-exist harmoniously while operating over a very wide range of frequencies. Under the umbrella of the KNOWS project we are revisiting “classical” wireless networking problems and designing new solutions that incorporate and build upon recent advances in software and hardware technologies for networking over the recently opened white spaces spectrum.<\/p>\n
The WhiteFiService APIs and web front-end\u00a0can be accessed by clicking here<\/a>. The white spaces spectrum is fundamentally different from the ISM bands where Wi-Fi operates\u00a0along three main axes. First, it exhibits spatial variation since\u00a0a channel available\u00a0at one node\u00a0might be occupied by a primary user (TV, microphone) at another node in the network. Second, the spectrum is not contiguous.\u00a0Some channels might be occupied by primary users hence causing the spectrum to be fragmented. Finally, there is\u00a0temporal variation since an available spectrum might be occupied at a later time by\u00a0a primary user, e.g. wireless microphone.<\/p>\n Given these challenges, we have\u00a0researched several techniques to form networks over this part of the spectrum. In the first version of KNOWS we introduced the concept of Time Spectrum Blocks (TSB)<\/strong> as\u00a0the fundamental unit\u00a0over which two nodes could communicate.\u00a0\u00a0We designed a control-channel based medium access control protocol, called CMAC,<\/strong> for enabling nodes with different spectrum views to access the medium.\u00a0Associated with\u00a0CMAC we\u00a0proposed and evaluated an algorithm, called bSMART<\/strong>, for efficiently allocating the spectrum to different contending nodes.<\/p>\n In the\u00a0second version of\u00a0KNOWS, we looked at the problem of setting up a base station in the white spaces spectrum. In this system, called WhiteFi<\/strong>, we eliminated the\u00a0need for a\u00a0dedicated control channel. In addition, we proposed a new technique, called SIFT<\/strong>,\u00a0that enables nodes to rapidly discover base stations operating at different center frequencies using different channel widths by analyzing signals in the time domain. We\u00a0proposed and evaluated\u00a0a new metric, called MCham,<\/strong> using which the base stations choose the “best”\u00a0chunk of the spectrum to operate on, where the spectrum chunk can span multiple channels. We have prototyped this system on Windows.<\/p>\n\t\t\t
\nCheck out deployment pictures by clicking here<\/a>.<\/p>\n