IEEE 802.22


IEEE 802.22

IEEE 802.22 is a new working group of IEEE 802 LAN/MAN standards committee 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.

Technology

The IEEE 802.22 working group on Wireless Regional Area Networks is the youngest group of the IEEE 802 LAN/MAN standards committee. Its project, formally called as "Standard for Wireless Regional Area Networks (WRAN) - Specific requirements - Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Policies and procedures for operation in the TV Bands" focuses on constructing a consistent, national fixed point-to-multipoint WRAN that will utilize UHF/VHF TV bands between 54 and 862 MHz. Specific TV channels as well as the guard bands of these channels are planned to be used for communication in IEEE 802.22.

Because the IEEE 802.22 working group was formed in 2004, nothing has yet been specified regarding the particular functionalities of the PHY/MAC layers. However the IEEE, together with the FCC, is pursuing a centralized approach for available spectrum discovery. Specifically each Access Point (AP) would be armed with a GPS receiver which would allow its position to be reported. This information would be sent back to centralized servers (in the USA these would be managed by the FCC), which would respond with the information about available free TV channels and guard bands in the area of the AP. Other proposals would allow local spectrum sensing only, where the AP would decide by itself which channels are available for communication. A combination of these two approaches is also envisioned.

Overview of the WRAN Topology

802.22 specifies that the network should operate in a point to multipoint basis (P2MP). The system will be formed by base stations (BS, above mentioned as Access Points, AP's) and customer-premises equipments (CPE). The CPE's will be attached to a BS via a wireless link in the frequencies mentioned above. 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.

An approach to the PHY layer

The goal of this layer is to provide excellent, yet simple, performance. The PHY layer must be able to adapt to different conditions and also needs to be flexible for jumping from channel to channel without errors in transmission or losing clients (CPE's). This flexibility is also required for being able to dynamically adjust the bandwidth, modulation and coding schemes. OFDMA will be the modulation scheme for transmission in up and downlinks. With OFDMA it will be possible to achieve this fast adaptation needed for the BS's and CPE's.By using just one TV channel (a TV channel has a bandwidth of 6 MHz; in some countries they can be of 7 or 8 MHz) the approximate maximum bit rate is 19 Mbit/s at a 30 km distance. The speed and distance achieved is not enough to fulfill the requirements of the standard. The feature "Channel Bonding" deals with this problem. Channel Bonding consists in utilizing more than one channel for Tx / Rx. This allows the system to have a bigger bandwidth which will be reflected in a better system performance.

An approach to the MAC layer

This layer will be based in Cognitive Radio Technology. It needs to be also able to adapt dynamically to changes in the environment by sensing the spectrum. The MAC layer will consist of two structures: Frame and Superframe. A superframe will be formed by many frames. The superframe will have an SCH (Superframe Control Header) and a preamble. These will be sent by the BS in every channel that it's possible to transmit and not cause interference. When a CPE is turned on, it will sense the spectrum, find out which channels are available and will receive all the needed information to attach to the BS. Two different types of spectrum measurement will be done by the CPE: "in-band" and "out-of-band". The in-band measurement consists in sensing the actual channel that is being used by the BS and CPE. The out-of-band measurement will consist in sensing the rest of the channels. The MAC layer will perform two different types of sensing in either in-band or out-of-band measurements: "fast sensing" and "fine sensing". Fast sensing will consist in sensing at speeds of under 1ms per channel. This sensing is performed by the CPE and the BS and the BS's will gather all the information and will decide if there is something new to be done. The fine sensing takes more time (approximately 25 ms per channel or more) and it is utilized based on the outcome of the previous fast sensing mechanism.These sensing mechanisms are primarily used to identify if there is an incumbent transmitting, and if there is a need to avoid interfering with it.

ee also

* Cognitive radio
* White Spaces Coalition

External links

* [http://www.ieee802.org/22/ IEEE 802.22 working group]

References

Cordeiro, Challapali, Birru & Shankar; "IEEE 802.22: An Introduction to the First Wireless Standard based on Cognitive Radios"; Journal of Communications, Vol. 1, No. 1, April 2006.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • IEEE 802.11 — is a set of standards for wireless local area network (WLAN) computer communication, developed by the IEEE LAN/MAN Standards Committee (IEEE 802) in the 5 GHz and 2.4 GHz public spectrum bands.General descriptionThe 802.11 family includes over… …   Wikipedia

  • IEEE 802.11 — (auch: Wireless LAN (WLAN), Wi Fi) bezeichnet eine IEEE Norm für Kommunikation in Funknetzwerken. Herausgeber ist das Institute of Electrical and Electronics Engineers (IEEE). Die erste Version des Standards wurde 1997 verabschiedet. Sie… …   Deutsch Wikipedia

  • IEEE 802.3 — est une norme pour les réseaux informatiques édictée par l Institute of Electrical and Electronics Engineers (IEEE). Cette norme est généralement connue sous le nom d Ethernet. C est aussi un sous comité du comité IEEE 802 comprenant plusieurs… …   Wikipédia en Français

  • Ieee 802 — est un comité de l IEEE qui décrit une famille de normes relatives aux réseaux locaux (LAN) et métropolitains (MAN) basés sur la transmission de données numériques par le biais de liaisons filaires ou sans fil. Plus spécifiquement, les normes… …   Wikipédia en Français

  • Ieee 802.3 — est une norme pour les réseaux informatiques édictée par l Institute of Electrical and Electronics Engineers (IEEE). Cette norme est généralement connue sous le nom d Ethernet. C est aussi un sous comité du comité IEEE 802 comprenant plusieurs… …   Wikipédia en Français

  • IEEE 802 — группа стандартов семейства IEEE, касающихся локальных вычислительных сетей (LAN) и сетей мегаполисов (MAN). В частности, стандарты IEEE 802 ограничены сетями с пакетами переменной длины. Число 802 являлось следующим свободным номером для… …   Википедия

  • IEEE 802.15 — is the 15th working group of the IEEE 802 which specializes in Wireless PAN (Personal Area Network) standards. It includes six task groups (numbered from 1 to 6):Task group 1 (WPAN/Bluetooth)IEEE 802.15.1 2002 has derived a Wireless Personal Area …   Wikipedia

  • IEEE 802 — est un comité de l IEEE qui décrit une famille de normes relatives aux réseaux locaux (LAN) et métropolitains (MAN) basés sur la transmission de données numériques par le biais de liaisons filaires ou sans fil. Plus spécifiquement, les normes… …   Wikipédia en Français

  • IEEE 802 — refers to a family of IEEE standards dealing with local area networks and metropolitan area networks.More specifically, the IEEE 802 standards are restricted to networks carrying variable size packets. (By contrast, in cell based networks data is …   Wikipedia

  • IEEE 802.15.4a — (formally called IEEE 802.15.4a 2007) is an amendment to IEEE 802.15.4 (formally called IEEE 802.15.4 20060 specifying that additional physical layers (PHYs) be added to the original standard.OverviewIEEE 802.15.4 2006 specified four different… …   Wikipedia

  • Ieee 802.11 — Exemple d équipement fabriqué sur les recommandations de la norme IEEE 802.11. Ici, un routeur avec switch 4 ports intégré de la marque Linksys. IEEE 802.11 est un terme qui désigne un ensemble de normes concernant les réseaux sans fil qui ont… …   Wikipédia en Français


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.