- IEEE 802.11y-2008
IEEE 802.11y-2008 is an amendment to the
IEEE 802.11-2007 standard that will enable high poweredWi-Fi equipment to operate on a co-primary basis in the 3650 to 3700 MHz band in the United States, except when near a grandfatheredsatellite earth station . [ [http://fjallfoss.fcc.gov/edocs_public/attachmatch/FCC-05-56A1.pdf See FCC File FCC-05-56A1.pdf paragraph 7, page 4] ] It was approved for publication by theIEEE on September 26th, 2008.Background
In June 2007 the FCC issued final rules for a novel "lite licensing" scheme in the 3650-3700 MHz band.cite web|title=FCC 07-99|publisher=US Federal Communications Commission|url =http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6519534338|] Licensees pay a small fee for a nation wide, non-exclusive license. They then pay an additional nominal fee for each high powered base station that they deploy. Neither the client devices (which may be fixed or mobile), nor their operators require a license, but these devices must receive an enabling signal from a licensed base station before transmitting. All stations must be identifiable in the event they cause interference to incumbent operators in the band. Further, there is a requirement that multiple licensees' devices are given the opportunity to transmit in the same area using a "contention based protocol" when possible. If interference between licensees, or the devices that they have enabled, cannot be mediated by technical means, licensees are required to resolve the dispute between themselves.
Features
The US 3650 MHz rules allow for registered stations to operate at much higher power than traditional Wi-Fi gear (Up to 20 watts
equivalent isotropically radiated power ). The combination of higher power limits and enhancements made to the MAC timing in 802.11-2007, will allow for the development of standards based 802.11 devices that could operate at distances of convert|5|km|mi|0 or more.IEEE 802.11y adds three new concepts to 802.11-2007 base Standard:
:Contention based protocol (CBP)- enhancements have been made to the carrier sensing and energy detection mechanisms of 802.11 in order to meet the FCC's requirements for a
contention based protocol .:Extended channel switch announcement (ECSA)- provides a mechanism for an
access point to notify the stations connected to it of its intention to change channels or to change channel bandwidth. This mechanism will allow for the WLAN to continuously choose the channel that is the least noisy and the least likely to cause interference. ECSA also provides for other functionalities besides dynamic channel selection based on quality & noise characteristics.:For instance, in 802.11y Amendment, the licensed operator can send ECSA commands to any stations operating under their control, registered or unregistered. ECSA is also used in 802.11n. In the 802.11n D2.0 implementation (which is shipping & undergoes Wi-Fi Alliance testing) 20MHz & 40MHz channel switching is provided for by the 11n PHY's ECSA implementation. Note that 802.11n is specified for operation in the 2.4GHz and 5GHz license exempt bands--but future amendments could permit 11n's PHY to operate in other bands as well.
:Dependent station enablement (DSE)- is the mechanism by which an operator extends and retracts permission to license exempt devices (referred to as dependent STAs in .11y) to use licensed radio spectrum. Fundamentally, this process satisfies a regulatory requirement that dictates that a dependent STAs operation is contingent upon its ability to receive periodic messages from a licensees base station, but DSE is extensible to other purposes in regards to channel management and coordination.
:Some of the benefits of DSE include:
::-The enabling station (aka the licensee's base station) may or may not be the access point that the dependent STA connects to. In fact, an enabling station may enable both an access point and its clients. Also, although the dependent STAs are required by regulation to receive information from the enabling station over the air, they are not required transmit over the air to complete the DSE process. A dependent STA may connect to a nearby Access Point for a short period of time and use the internet or some other means to complete the channel permissioning process with the enabling station. This flexibility reduces the likelihood of a dependent STA causing interference while attempting to connect to a far off enabling station.
::-The personal privacy and security of end users are ensured while, at the same time, licensees will have the information necessary to resolve disputes. All .11y devices transmit a unique identifier for the purpose of resolving interference. The high powered fixed stations and enabling stations transmit the location that they are operating from as their unique identifier. This location is also registered in an FCC database that will identify the licensee. The dependent STAs broadcast the location of the station that enabled it plus a unique string supplied by the enabling station. This ensures that the responsible party, the licensee, is contacted to resolve disputes. This mechanism also alleviates the problems associated with having the dependent STA broadcasting its location. Requiring all devices to have GPS or some other means of verifying their location would increase the cost and complexity of devices, and this solution may be inadequate indoors. This method also resolves fears that a mobile devices that constantly beacons its location could be used inappropriately by third parties to track a user's location.
Beyond the US 3650 band
While the scope of 802.11y was limited to operation in the US 3650-3700 MHz band in the US, care was taken so that, if the light licensing concept was well received, it would not be necessary to start the 3+ year task group process in order for 802.11y devices to operate in other countries or in other frequency bands. As a result, lightly licensed 802.11 devices will be able to operate in any 5, 10, or 20 MHz channel that regulators make available by simply adding entries to the country and regulatory information tables in Annex I and J of 802.11.
Other potential bands for 802.11y include:
:4.9 GHz - The regulatory classes and channel sizing needed to support the US public safety allocation at 4.9 GHz were added to 802.11-2007cite web|title=802.11-2007|publisher=IEEE SA|url =http://shop.ieee.org/ieeestore/Product.aspx?product_no=SS95708|] . DSE and ECSA will allow frequency coordinators to have dynamic control over channel access.
:5 GHz - Regulators and equipment manufactures continue to debate the effectiveness of dynamic frequency selection (DFS) as a mechanism to avoid incumbent users in the 5 GHz bands. For example, Canada is not currently certifying 802.11 equipment for use in the 5600-5650 MHz band that is used by certain types of weather radars.cite web|title=Low-power Licence-exempt Radiocommunication Device|publisher=Industry Canada |url =http://strategis.ic.gc.ca/epic/site/smt-gst.nsf/vwapj/rss210e.pdf/$FILE/rss210e.pdf|Additional requirements for the band 5600-5650 MHz: Until further notice, devices subject to this Section shall not be capable of transmitting in the band 5600-5650 MHz, so that Environment Canada weather radars operating in this band are protected. ] 802.11y may provide a solution that will allow WLANs access to these bands. Firstly, DSE can be used to create exclusion zones around incumbent users; Secondly, when combined with DSE, the 802.11y device identification mechanism allows devices that cause interference to be denied further access to a channel within seconds.
:IMT-Advanced candidate bands- (450-862, 2300-2400, 2700-2900, 3400-4200, and 4400-5000 MHz- Since 2003, The International Telecommunications Union (ITU) has been studying the potential for IMT-advanced services (aka systems beyond IMT-2000 or
4G ) to use a number of frequencies between 450 and 5000 MHz for the next generation of cellular infrastructure. These systems will be capable of transmitting 100 Mb/s when mobile and 1000 Mb/s while stationary. Unfortunately, with the exception of a small amount ofUHF spectrum that will become available upon the completion of the transition from analogue to digital television, these bands are occupied on a piecemeal basis by incumbent users that are not easily relocated. Extensive sharing studies have concluded that co-existence with legacy equipment over the same area is not feasible, so traditional mobile licensing approaches are not practical. Yet academic studies have shown that at any give time, even in dense urban environment, there is ample unused spectrum across the candidate bands. cite web|url=https://bwrc.eecs.berkeley.edu/Research/Cognitive/CR%20Workshop/CRintrobob.pdf |title=A Workshop on Cognitive |accessdate=2007-07-30 |last=Brodersen |first=Bob |date=2004-11-01 |publisher=BWRC ] The problem is that usage by the primary services in these bands may change over time (as is the case with some radar systems) or vary by sub-channel based on location (as is the case in the TV bands "white spaces") 802.11y, along with the continued advances in multi-band radio technology, may provide a solution to this problem by granting channel access dynamically to users based on primary user avoidance techniques, location and time.
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