BIT ERROR SIMULATION FOR PI/4 DQPSK MOBILE RADIO-COMMUNICATIONS USING 2-RAY AND MEASUREMENT-BASED IMPULSE-RESPONSE MODELS

A combination hardware and software simulation technique that allows real-time bit-by-bit error simulation for mobile radio systems is described 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 system parameters (e.g., modulation scheme, data rate, signal-to-noise ratio, and receiver speed) and different channel environments (i.e., outdoor and indoor multipath fading channels) may be specified and permit performance comparison. Additive white Gaussian noise and cochannel interference effects are also simulated by the software. Using the simulation tool, we studied average BER results for pi/4 DQPSK with Nyquist pulse shaping in indoor and outdoor, flat, and frequency-selective fading channels. BER results for high data rate (> 450 kb/s) transmission in channels generated by a measurement-based indoor channel model, SIRCIM [1], are compared with results in channels generated by the classic 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 multipath components. In addition, an example of bit-by-bit error simulation of the transmission of a video image in a mobile radio fading channel is shown. This simulation methodology, which has been implemented in a program called BERSIM, allows subjective evaluation of link quality between a source and sink in laboratory in real time without requiring any radio frequency hardware.