Information Technology Reference
In-Depth Information
TABLE 13.3
IEEE 802.11a OFDM Channel Plan for 5 GHz
Center
Channel
Frequency (MHz)
Band and US Designation
36
5180
U-NII lower band, 5.15-5.25 GHZ
40
5200
"
44
5220
"
48
5240
"
52
5260
U-NII middle band, 5.25-5.35 GHZ
56
5280
"
60
5300
"
64
5320
"
149
5745
U-NII upper band, 5.725-5.825 GHZ
153
5765
"
157
5785
"
161
5805
"
example, one might have a wireless keyboard, mouse, phone, remote control, or
stereo speaker, all connected to their respective hosts by this low-cost technology.
Bluetooth is standardized as IEEE 802.15.1 and is one of a group of personal area
network (PAN) short-range networking technologies.
Bluetooth is a “frequency hopper,” and it uses FHSS at 2.4 GHz at 1 Mbps sig-
naling rate, for the time being. Separate synchronous and asynchronous links are
defined. The synchronous mode is connection-oriented, with slot reservations and
data paths that are symmetrical. This makes it function essentially as a time-division
multiplexer. Symmetric data rates from 108.8 kHz to 432.6 kHz are supported. The
asynchronous mode, in contrast, is connectionless and packet-switched with a
polling access method that allows a range of data rates from 57.6 to 721.0 kHz.
The combination of simple frequency-hopping technology, a low bandwidth 1
MHz symbol rate, common 2.4 GHz electronics, and adaptable power levels have
allowed this technology to become a very low-cost, low-power, single-chip solution.
Bluetooth is endorsed by almost every major semiconductor, computer, and con-
sumer products manufacturer, and is now being used in wireless keyboards, print-
ers, and even cell phone headsets. Long-term, this will be a very common method to
connect a wide range of devices within a 10-m distance. Increased power levels can
jump the range up to about 100 m, which might make it contend for some applica-
tions that are being done by WiFi now.
