Thomas Kunz
Systems and Computer Engineering
166
802.11 Physical Layer
n3 versions: 2 radio (typ. 2.4 GHz), 1 IR
–data rates
1 or 2 Mbit/s
nFHSS (Frequency Hopping Spread Spectrum)
–spreading,
despreading, signal strength, typ. 1 Mbit/s
–min. 2.5
frequency hops/s (USA), two-level GFSK modulation
nDSSS (Direct Sequence Spread Spectrum)
–DBPSK
modulation for 1 Mbit/s (Differential Binary Phase Shift Keying), DQPSK for 2 Mbit/s (Differential Quadrature
PSK)
–preamble
and header of a frame is always transmitted with 1 Mbit/s, rest of transmission 1 or 2 Mbit/s
–chipping
sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code)
–max.
radiated power 1 W (USA), 100 mW (EU), min. 1mW
nInfrared
–850-950 nm,
diffuse light, typ. 10 m range
–carrier
detection, energy detection, synchonization