IEEE 802.11y-2008 - Features

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 5 kilometres (3 mi) 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.