Doug Lung /
08.04.2011 03:30 PM
IEEE Publishes TV Band WRAN Standard
Last month IEEE 802.22
. This is the standard for Wireless Regional Area Networks (WRANs) operating in the VHF and UHF TV frequency bands. Such frequencies allow broadband wireless access throughout a large area of up to 100 km distant from the transmitter. The IEEE said that each WRAN could deliver up to 22 Mbps per channel and that the technology would be especially useful in serving less densely populated areas of the country, and also in developing nations.
The IEEE 802.22 technical reference linked above describes some of the unique characteristics of the technology. While the FCC has dropped the sensing requirement for most devices in favor of geolocation, the IEEE 802.22 proposal provides TV and wireless microphone protection via sensing. The physical layer is optimized to tolerate long channel response and frequency selective fading, and the MAC layer compensates for the long roundtrip delays that are possible with such long range transmissions. Cognitive radio technology allows the unlicensed devices to cooperate with other 802.22 cells on the same frequency, as well as to protect primary users.
The IEEE 802.22 document provides an excellent example of spectrum sharing that benefits new users without hurting incumbents. The IEEE 802.22 standard committee members kept the broadcast community up to date on its work by presenting papers and taking questions at events such as the annual IEEE Broadcast Technology Symposium. Broadcaster input was welcomed by the committee.
Unlike some of the proposals in the National Broadband Plan, IEEE 802.22 is targeted at rural areas where television broadcast spectrum is available, and where the long range characteristics of the VHF and UHF TV bands can be put to best use.
Compare this to the National Broadband Plan's recommendation to take away half the UHF TV channels, essentially squeezing out sharing such as that described in IEEE 802.22. The plan would also give up UHF spectrum to wireless carriers in urban markets where its greater transmission range would be a detriment to efficiency and small cell frequency reuse, unless, of course, it's used for wide area point-to-multipoint multicasting. In other words, IP broadcasting.
Edwin Kee has a nice overview of 802.22 in his Aug. 1 article WiFi 802.22 can cover 12,000 km