Sharing the Spectrum with Bluetooth

An added complication is that IEEE 802 shares spectrum with Bluetooth. Bluetooth
provides an even more localized connectivity option—for example, to provide a localized
RF connection between an earpiece/earbud headset and a cellular phone, or to
connect a cellular phone to other peripheral devices, or to connect peripheral devices
to other peripheral devices. Table 15.2 shows the ISM band allocation by country at
2.4 GHz.
A Bluetooth transceiver is a low-power device—either 100 mW (+20 dBm), 1 mW
(0 dB) or 1 μW (-30 dBm). It uses frequency hopping at 1600 hops per second across
79 hop frequencies at 1 MHz spacings. It uses simple FM modulation to reduce component
costs and power consumption.

Present devices are either two-chip or single-chip implementations. For cost reasons,
the processes use CMOS. This tends to compromise receive sensitivity (high noise
floor), particularly in single-chip devices. Range is not included in the specification, but
vendors have derived figures of 100 meters for the 100 mW device and 10 meters for the
1 mW device, assuming -70 dBm receiver sensitivity and -5 dBi antenna gain. 364