802.11 Physical Layer
n 3 versions: 2 radio (typ. 2.4 GHz), 1 IR
data rates 1 or 2 Mbit/s
n FHSS (Frequency Hopping Spread Spectrum)
spreading, despreading, signal strength, typ. 1 Mbit/s
min. 2.5 frequency hops/s (USA), two-level GFSK modulation
n DSSS (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
n Infrared
850-950 nm, diffuse light, typ. 10 m range
carrier detection, energy detection, synchonization