IEEE 802.11 Infrared Specifications

IEEE 802.11 Infrared Specifications
A good deal of thought and work went into the 802.11 standards regarding the use of IR signals;
unluckily, to little avail. Constructing a WLAN using IR technology would require that devices be
placed closer together than when using radio signals, and this may have prevented implementers,
striving for maximal computing mobility, from devoting much attention to the 802.11 IR. Plus,
although the 802.11 standards allow for IR that is not line-of-sight, there is a common perception that
IR devices must be “aimed at” each other, like a TV and its remote control. Another drawback may be
that the 802.11 infrared-based LANs are only meant to operate indoors, constrained by exterior walls
[452]. In any event, there are no wireless networking products currently available that implement this
IR PHY [453].
The 802.11 infrared (IR) PHY stipulates that light in the 850- to 950-nm range is used for
signals – which do not have to be directed – which permits the construction of a true LAN system.
The range of such signals, with sensitive receivers allowed for under the 802.11, is about 20 m (not
big enough for a regular classroom). However, in an environment lacking in reflective surfaces, the
range would be reduced. On the other hand, an IR LAN in one room would not be susceptible to
eavesdropping by (or interference from) a station in an adjacent room, because IR signals do not pass
through walls. And the standards contain a cure for offending IR devices in the same room: If such a
device does interfere, by transmitting continuously and with a very strong signal, it can be physically
isolated (placing it in a different room) from the IEEE 802.11 LAN. The 802.11 standards designate
temperatures from 0 to 40 ◦C as the range for full operation compliance with the IR PHY. When the
standards were prepared, the only regulations on IR transmissions concerned safety issues, and there
were no frequency allocation or bandwidth allocation restrictions on IR emissions worldwide [452].