This paper deals with a Matlab-simulink simulation of IEEE 802.11b physical Layer specification. There was made a Matlab Simulink program that simulates 4 data rates (1, 2, 5.5, 11 Mbps) specified in the 802.1 lb standard. Program includes Barker coding implementation for lower data rates (1,2 Mbps) and CCK (complementary code keying) for higher data rates providing 5.5 and 11 Mbps. All data rates are using DSSS (direct sequence spread spectrum). Basic description of the program and results in graphical and numerical form are introduced as a BER to Eb/NO dependence.