| Summary: | 碩士 === 國立交通大學 === 電資學院學程碩士班 === 91 === In this thesis, we analysis the GMSK base band signal characteristics at first. There are 156 transmitted bits every time slot in the TDMA frame structure. Under the environment of fading, multi-path and noise interference, we analysis the system performance. In this thesis, we employ two detection schemes to resolve the received signals. One is differential (Decision feedback) detection, the other is decision feedback equalization detection.
In the differential detection processing, we according to the phase difference between the consecutive data to detect the transmission signals. Which has 90 degrees deviation between two adjacent symbols for GMSK signal. In addition, the decision feedback in the differential detection is used in this thesis. The major purpose is to reduce the previous inter-symbol interference on current bit decision. Because we should avoid the impact of previous data for current data when the previous data was detected.
In the decision feedback equalization detection processing, we also use 3 different methods. First one, we have no using the de-rotation processing before equalization detection. The second one, we use two equalization processing to enhance system performance. The last one, we use the de-rotation technique before equalization detection to simplify the received signals [6]. They are also use the NLMS algorithm to equalize it. After decision feedback equalization processing, we can train the channel characteristic to get transmitted data and reduce the multi-path impact in transmitted signal.
According the simulation result, we can select the suitable detection technique to receive signals depending on the system resource and environmental condition.
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