802.22 general information
802.22 is a new 802 LAN/MAN standards which aims at constructing Wireless Regional Area Network (WRAN) utilizing white spaces(channels that are not already used) in the allocated TV frequency spectrum. The use of the spectrum will be used in an opportunistic way in order not interfere with any TV channel that is transmitting
802.22 is a new 802 LAN/MAN standards
Wireless Regional Area Network (WRAN)
White spaces in TV frequency spectrum
802.22 based on Cognitive Radios
802.22 specifies that the network should operate in a point to multipoint basis (P2MP). The system will be formed by base station (BS) and customer-premises equipments (CPE, above mentioned as Access Points, AP's). The CPE's will be attached to a BS via a wireless link in the white spaces. The BS's will control the medium access for all the CPE's attached to it. One key feature of the WRAN Base Stations is that they will be capable of performing a distributed sensing. This is that the CPE's will be sensing the spectrum and will be sending periodic reports to the BS informing it about what they sense. The BS, with the information gathered, will evaluate whether a change is necessary in the channel utilized, or on the contrary, if it should stay transmitting and receiving in the same one
Point to multipoint basis (P2MP)
Solution to the current low usage of radio spectrum
Flexible, efficient, and reliable spectrum use
Potential to utilize the large amount of unused spectrum
Ø Required real‐time measurement dissemination
802.22 is based on cognitive radios (CRs). Cognitive Radios are seen as the solution to the current low usage of the radio spectrum. It is the key technology that will enable flexible, efficient, and reliable spectrum use by adaption the radio’s operating characteristics to the real-time conditions of the environment. CRs have the potential to utilize the large amount of unused spectrum in an intelligent way while not interfering with other incumbent devices in frequency bands already licensed for specific uses. CRs are enabled by the rapid and significant advancements in radio technologies, and can be characterized by the utilization of disruptive techniques such as wide-band spectrum sensing, real-time measurement dissemination
Example of TV band occupancy over time and frequency diagram of the channel bonding scheme illustrating
Used frequencies based on Cognitive Radios
While the major push towards the commercial deployment of CRs is coming mostly from the US, the goal of IEEE 802.22 is to define an international standard that may operate in any regulatory regime. Therefore, the current 802.22 project identifies the North American frequency range of operation from 54-862 MHz, while there is an ongoing debate to extend the operational range to 41-910 MHz as to meet additional international regulatory requirements. Also, the standard shall accommodate the various international TV channel bandwidths of 6, 7, and 8 MHz.
The most prominent target application of 802.22 WRANs is wireless broadband access in rural and remote areas, with performance comparable to those of existing fixed broadband access technologies (e.g., DSL and cable modems) serving urban and suburban areas. In the last five years, the US has dropped from third to sixteenth place both in terms of the share of the population with broadband and the speed of these connections. While availability of broadband access may not be so critical in urban and suburban areas, this certainly is not the case in rural and remote areas where about half of the US population is concentrated (a similar argument possibly applies to other countries too, especially those located in South America, Africa and Asia). Therefore, this has triggered the FCC to stimulate the development of new technologies (e.g., based on CRs) that increase the availability of broadband access in these underserved markets
The other key target markets addressed by 802.22 WRAN networks include single-family residential, multi-dwelling units, small office/home office (SOHO), small businesses, multi-tenant buildings, and public and private campuses. 802.22 network shall provide services such as data, voice, as well as audio and video traffic with appropriate Quality-of-Service (QoS) support.
The 802.22 system specifies spectral efficiencies in the range of 0.5 bit/(sec/Hz) up to 5 bit/(sec/Hz). If we consider an average of 3 bits/sec/Hz, this would correspond to a total PHY data rate of 18 Mbps in a 6 MHz TV channel. In order to obtain the minimum data rate per CPE, a total of 12 simultaneous users have been considered which leads to a required minimum peak throughput rate at edge of coverage of 1.5 Mbps per CPE in the downstream direction. In the upstream direction, a peak throughput of 384 kbps is specified, which is comparable to DSL services.
Another distinctive feature of 802.22 WRAN as compared to existing IEEE 802 standards is the BS coverage range, which can go up to 100 Km if power is not an issue (current specified coverage range is 33 Km at 4 Watts CPE EIRP). WRANs have a much larger coverage range than today’s networks, which is primarily due to its higher power and the favorable propagation characteristics of TV frequency bands. This enhanced coverage range offers unique technical challenges as well as opportunities.
802.22 wireless RAN classification as compared to other popular wireless standards