Design Aspects of a Television White Space Device Prototype

In this paper, we describe the design challenges of a recently developed television white space (TVWS) device prototype and how those were resolved. The prototype, which includes the following components: a cognitive management entity (CME), a sensing module, a geolocation device, a TV band database, a transmitter and a receiver, was designed to take part in Singapore TVWS test trial. The major features the prototype has are: cognitive functionality, spectrum sensing and database access. The technical challenges faced during its development are described in terms of wide dynamic range, adjacent channel rejection and synchronization issues of the spectrum sensor, baseband vs intermediate frequency based sensing, non white environmental noise, security regarding database access and troubles inherent in wireless environment. Performance of the prototype is also presented in terms of cognitive operations such as, success of TV signals and other incumbent detection through database access and sensing, time required for database access, sensing, channel selection, channel switching etc. Discussion regarding setting a reasonable sensing target is also presented.