In the thesis work, we implement a MODEM using Demand Assignment Multiple Access-Single Channel Per Carrier(DAMA-SCPC) protocol for satellite communications and analyze the timing, carrier, and frequency synchronization algoritms suitable for voice and data transmission which require high BER(Bit Error Rate) performance. In the transmitter, voice and data are modulated by BPSK or QPSK, and transmitted in the burst mode. In the receiver, the symbol timing, carrier phase and frequency are synchronized by DD(Decision Direct) method. The synchronization is compose of three functional parts: 1) to perform the baud-rate timing recovery algorithm proposed by,Mueller&Muller 2) to perform the DD carrier phase recovery which has a PLL(Phase Locked Loop) form, and 3) to perform the carrier frequency recovery using a quardricorrelator. Through simulation, it is verified that they can work well so as to have a good estimated variance performancein noisy environment.
Also, in this thesis work, a MODEM is implemented using 7 DSPs(Digital Signal Processors). The interprocessor-communication between DSPs is designed using TDM(Time Devision Multiplexer) protocol in order to reduce the hardware complexity. Through the TDM lines, the system management information and the results of calculation of algorithms at each DSP are transfered each other simultanuously at the high speed. The micellaneous circuits are integrated in two EPLDs(Erasable Programmable Logic Devices) for compact design. Because the implemented structure has a general form in view of signal processing systems, it can be utilized with flexibility at MODEMs for the other communication systems with various applications.
