| Summary: | ABSTRAK
Communication systems often involve waveforms manipulation either in time axis or frequency axis. It is necessary to manipulate these waveforms for the sake of having better power efficiency or bandwidth efficiency. To analyze waveforms more easily and to produce attractive graphical display, toolboxes and special functions are very helpful. Application programs provided by MATLAB For Windows (Windows 3.11 or Windows 95) are handy for this purpose, and convenient for as to write program on it. The MATLAB programs used here are version 4.2c.1 and utilize Signal Processing Toolbox version 3.0b. In this paper, these programs will be used to simulate simple digital communication link with GMSK modulation. Nowadays, GMSK modulation is officially used by mobile cellular telephone systems viz: GSM, DCS-1800, PCS-1900, cordless telephone system DECT, and wireless data packet system CDPD. The simulation is intended to show that GMSK modulation is very efficient in bandwidth. Here, communication link assumes that data sent are already in binary and experience Additive White Gaussian Noise. The modulator used is an ordinary FM modulator with modulation index of 0.5 with Gaussian low pass filter. Demodulation processes implement coherent detection, 1 bit differential detection and 2 bit differential detection. The two last methods are noncoherent detections. With the use of MATLAB, all waveforms on each step can be evaluated clearly.
Key word: Matlab for windows, simulasi komunikasi, modulasi GMSK
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