부산대학교 도서관

Recent proposed rulemakings from the Federal Communications Commission in the United States offers the hope of unique access to valuable spectrum; so-called television whitespace (TVWS). Use of this spectrum is contingent upon the protection of the incumbent occupants of the proposed allocation. Television signals are among the most powerful terrestrial RF transmissions on Earth. Even so, detection of these signals to the required levels sufficient to protect these services has proven daunting. Supplemental techniques, such as geo-location, mitigate these challenges for fixed TV broadcast; however, other nomadic low power incumbents also occupy the TVWS spectrum. The most common of these are wireless microphones, a subset of which are licensed and entitled to protection. These devices are allowed a maximum conducted power level of 50 mW and 250 mW on the VHF and UHF channels, respectively. Critical to day-to-day television operations, these devices must also be afforded protection from unlicensed transmitters. Wireless microphones often operate at power levels of 25 mW or less, with inefficient antennas placed physically near the body, yielding effective radiated power levels of 5 to 10 mW, often times even less. In addition, the emissions from these devices are often audio-companded FM, making legitimate, licensed operations indistinguishable from narrowband unlicensed transmissions and other discrete carriers. To that end the IEEE 802.22 working group established task group 1 (TG1) to develop a standard for a protective, disabling beacon method capable of insuring detection of legitimate devices.