Kvaliteta prijenosa u mobilnim radiokomunikacijskim sustavima s diskretnom modulacijom faze

ln order to evaluate the characteristics for given channel modulation technique before construction, some model of the channel must be developed that adequately describes the environment. Such analysis reduces the cost of developing a complex system by reducing the amount of hardware that has to be developed for evaluation of performance. Theoretical models have a second advantage in their ability to reproduce a channel for comparison between various communication strategies, resulting in an accurate measure of relative performance. In this thesis, wideband characteristics are determined from the simulation model, and found to give access to more detailed information on the channel than is obtainable through physical measurement. The results of the wideband simulations are graphically presented. The indoor environment is characterised by a large number of propagation paths from the transmitterto receiver, and is hence classed as a multipath environment. This thesis has shown that a physically based description of the channel impulse response is required not only for evaluation and development of in-door communication systems that attempt to use the limited available radio bandwidth to best effect, but also for investigation of the propagation mechanisms involved in indoor communications. A model based on previous measurements has been presented and applied to BER estimation for BPSK, FSK and π/4 DQPSK. Even though BPSK has the lowest BER in comparison to π/4 DQPSK and FSK, π/4 DQPSK is evaluated as best modulation technique due to its spectral efficiency.