Co-Operative Use of Licensed Spectrum by Unlicensed Devices: The Concept of Bandwidth Scavenging

To mitigate the spectrum depletion due to the unprecedented wireless traffic growth, FCC has freed up large amounts of UHF spectrum and made them available to license-exempt devices. The European Commission has adopted a similar stance by pledging to quot;reuse spectrum and create a single market out of itquot;. The EC has gone as far as to call the radio spectrum the quot;economic oxygenquot;. The approach whereby license-exempt (or unlicensed) devices are allowed (under certain, often very stringent, conditions) to access unused areas of the airwaves or gaps that exist in bands that have been reserved for TV broadcasts (so-called TV White Spaces), is being trialed in the US as well as the UK and the rest of Europe, with Japan preparing its own TVWS roll-out timeline. TV White Space spectrum is an attractive alternative to expensive auctioned spectrum, for applications including e.g. small cells. In this paper we discuss an evolutionary approach looking beyond the current/emerging TV White Space concepts, for which we adopt the term Bandwidth Scavenging and which has the potential to: serve Primary User (PU) systems other than DTT; enable more dynamic spectrum sharing than the TVWS systems by providing incentives for the PU systems; allow Secondary Users (SUs) to serve as relays for PU traffic. We examine co-operation between the incumbents and SUs and demonstrate the trade-offs possible using a MATLAB simulator. We then highlight some of the changes needed in existing communication systems for the observed benefits to become a reality. We additionally discuss various models of spectrum sharing and changes needed in current spectrum legislation to support the proposed approach to collaboration.