BIT ERROR SIMULATION FOR PI 4 DQPSK MOBILE RADIO-COMMUNICATIONS USING2-RAY AND MEASUREMENT-BASED IMPULSE-RESPONSE MODELS/

A combination hardware and software simulation technique that allows r eal-time bit-by-bit error simulation for mobile radio systems is descr ibed in this paper. The technique simulates mobile radio communication links and generates average bit error rate (BER) and bit-by-bit error patterns. The hardware simulates bit errors between a data source and sink in real time using the error patterns. Various communication sys tem parameters (e.g., modulation scheme, data rate, signal-to-noise ra tio, and receiver speed) and different channel environments (i.e., out door and indoor multipath fading channels) may be specified and permit performance comparison. Additive white Gaussian noise and cochannel i nterference effects are also simulated by the software. Using the simu lation tool, we studied average BER results for pi/4 DQPSK with Nyquis t pulse shaping in indoor and outdoor, flat, and frequency-selective f ading channels. BER results for high data rate (> 450 kb/s) transmissi on in channels generated by a measurement-based indoor channel model, SIRCIM [1], are compared with results in channels generated by the cla ssic two-ray Rayleigh fading model. Simulation results show that when the ratio of rms delay spread to symbol duration is greater than about 0.04, the irreducible BER is not only a function of rms delay spread but is also a function of the temporal and spatial distribution of mul tipath components. In addition, an example of bit-by-bit error simulat ion of the transmission of a video image in a mobile radio fading chan nel is shown. This simulation methodology, which has been implemented in a program called BERSIM, allows subjective evaluation of link quali ty between a source and sink in laboratory in real time without requir ing any radio frequency hardware.