User Manual

USER'S AND DEVELOPER'S GUIDE WRAP MULTIRADIO ACCESS SERVER
The Bluetooth frequency band is divided into distinct channels with 1 MHz channel spacing. In
order to comply with out-of-band regulations in each country, a guard band is used at the
lower and upper band edge. The frequency range is 2.400 – 2483.5 MHz, and the
corresponding channels are f = 2402 + k MHz; k = 0 – 78. Transmission utilizes channel
hopping over the specified range at 1600 kHz hop frequency. When operating in countries that
permit the use of only a subset of the overall spectrum, transmission utilizes only the approved
portions of the spectrum. The Bluetooth system utilizes Gaussian frequency shift keying
(GFSK). The signaling rate is 1 Mbit/s.
5.2 P
OWER CONSIDERATIONS
The Bluetooth system transceivers are classified into three power classes to support different
link ranges.
• Power Class 1. Output power is 1 – 100 mW (0 – 20 dBm) with mandatory power
control ranging from 4 to 20 dBm.
• Power Class 2. Output power is 0.25 – 2.5 mW (-6 – +4 dBm) with optional power
control.
• Power Class 3. Output power is less than 1 mW (0 dBm) with optional power control.
Bluegiga’s WRAP products support a 100 meter link range with Option 1 (Power Class 1).
5.3 R
ADIO FREQUENCY PROPAGATION
The radio frequency signal propagates in free space as a spherical wave, from a point source
to all directions equally. In reality, the actual signal source always differs from a theoretic
isotropic signal source. The power distribution of wireless telecommunication equipment in
space is determined by the antenna radiation pattern. In free space the signal propagates with
the speed of light and attenuates with 1/r2 relation. In reality, the environment always differs
from free space. The propagation environment of wireless telecommunication equipment is
restricted by all obstacles.
The basic mechanism of radio propagation is attributed to reflection, diffraction, and scattering
depending on existing obstacles. Since the radio frequency signal propagates
omnidirectionally, the transmitted signal arrives at the receiver following multiple paths
deformed by the aforementioned propagation mechanisms. The received signal is the
superposition of attenuated and delayed replicas of the transmitted signal, leading to fading of
the transmitted signal and broadening of the duration of the transmitted pulse. The
transmitted pulse delay spread leads to inter-symbol interference (ISI) because the
subsequent symbols interfere with each other. The ISI leads to a bit error probability (BIT)
floor that is independent of the signal to noise ratio (SNR). Depending on the time delay
spread of the transmitted pulse or the amount of widening that the transmitted pulse
experiences across the radio channel, the multipath interference differs. When the time delay
spread of the transmitted signal is very small with respect to the signaling time, the multipath
interference essentially leads to the signal fading phenomena of the received signal. When the
time delay spread of the transmitted signal is high with respect to the signaling time, the
multipath interference leads to the symbol interference phenomena of the received signal as
well.
A major difference between indoor and outdoor environments is that the former is considerably
more sensitive to changes in the geometry of the environment than the latter. This is because
of the differences in distance between obstacles. For example, a door being shut rather than
open may have a major impact on an indoor environment whereas a comparable event in an
outdoor environment may have a minor impact.
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