The Effect of Unlicensed Cognitive Device Operation on Digital Television Performance in the VHF/UHF Band

摘要

This paper analyzes the effects of recent development in Over-The-Air (OTA) Television Broadcasting that will allow for new full duplex digital services to be offered in the band. On February 17, 2009, the analog terrestrial television system will have fully transitioned to digital in the United States ending an era of analog TV broadcasting; Canada is to follow in August 2011. At that stage, broadcast RF spectrum will be only occupied by Digital Television (DTV) services making possible the co-existence of other (non-broadcast) digital services resulting from the improved spectrum efficiency offered by digital technology. This recent development allows for new digital services to be offered mainly to rural and remote areas where broadband Internet Multimedia Services (IMS), available in the urban and sub-urban areas are unlikely to be delivered by standard means. In an effort to improve even more the efficient use of the spectrum, the FCC issued a Notice of Proposed Rule Making (NPRM) for the development of a Cognitive Radio (CR) type Unlicensed Device (UD) that would be deployed in the television band. These UDs would operate in the vacant DTV spectrum, known as "white space", thus fostering broadband access and IMS service delivery to end users. Concerns, however, have been raised by DTV broadcasters on the impact that these devices could have on DTV reception. To that end, studies were performed at CRC to quantify the level of interference generated by the Unlicensed Devices and their effect on DTV operations. The results from these studies will be presented in this paper and show that it is imperative that the UDs cognitive radio be able to detect and avoid channels being used by incumbents i.e., DTV and Cordless Microphones (CM). These cognitive radios will have to strictly abide by a set of rules such that harmful interference to the incumbents is avoided.