An Experiment with Direct-Sequence Spread Spectrum Using Differential Phase Shift Keying Modulation for Indoor,Wireless Communications

摘要

We report on our measurements that have been made on a direct-sequence spread spectrum radio using differential phase shift keying modulation for a wireless PBX.We describe the design and implementation of a transmitter and a receiver using a Surface Acoustic Wave (SAW) filter matching the spread spectrum code of a user.The receiver performance is within I dB of the theoretical performance of a differential phase shift keying (DPSK) receiver in the presence of additive white Gaussian noise.We also show receiver performance in a multipath fading indoor environment with multipath fade notches of up to 50 dB depth.The indoor channel multipath fading can be overcome by using an equal gain diversitycombiner.We confirm that the indoor mean power levelattenuation follows the inverse fourth power of the distance.Also,we investigate the multiple access capability of the system by introducing an interfering transmitter with a different spread spectrum code sequence.