Wireless LANs with DPSK

This paper investigates the performance of an indoor wireless communication system using differential phase shift keying (DPSK) modulation. The intermittence of a 1.95 GHz radio channel is examined by monitoring the bit error rate (BER) performance of the system in a teaching laboratory. The data rate is 10 Mbits/s. 'Dead zones' in the laboratory are confirmed to be caused by the multipath effect. The number of dead zones is greatly reduced as the antenna are repositioned so that the first Fresnel zone of the link is unobstructed. The experiments are conducted with manual control of the transmitted power. Consequently, it is necessary to implement the feedforward automatic gain control at the IF stage of the receiver.