Error Performance for CPM with Catastrophic Modulation Index
| Autor: | Guan-Lin He, 何冠霖 |
|---|---|
| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 Continuous phase modulation (CPM) is a modulation with memory. The memory results from the continuity of the transmitted carrier phase from one signal interval to the next. The phase continuous property enables the detection of CPM signals using maximum likelihood sequence detection (MLSD) receiver. Also, the phase continuous property produce CPM signals with fast roll-off and narrow sidelobes, and CPM are thus attentive in mobile communications. In the literatures, it is shown that the modulation index of CPM systems may have a property called catastrophic modulation index, which causes a pair of input information sequences with infinite different symbols to generate corresponding pair of transmitting CPM signals with finite Euclidean distance. As a result, finite channel errors will cause infinite symbol errors in the demodulation. However, we found that the CPM with catastrophic modulation index the minimum Euclidean distance may be decided by this pair of transmitted signals. If the a priori probability of this pair of signals is very low, the true bit error rate (BER) may not be decided by the minimum Euclidean distance. This paper aims at finding the true BER performance of this class of CPM systems using computer stimulation. Actually, most of the CPM signals are accompanied by the characteristics of catastrophic modulation index. In this paper, the CPM receiver considered for BER simulation is MLSD. Previous researchers found that the performance of CPM using MLSD can be estimated using the minimum Euclidean distance. The simulation results show that the error performance for CPM with catastrophic modulation index is much better than the performance estimated by the minimum Euclidean distance with the increase of decision depth. The most important reason to cause such results is due to the fact that CPM signals are asymmetrical. Simulation is conducting using various phase shaping pulses, the results show it could obviously get better gains under catastrophic modulation index. For example, binary CPM with phase shaping pulse 4REC outperforms 3REC with 1.25 dB gains for the same 99.9 percent power-in-bandwidth and the same BER. In fact, previous research considered binary CPM with 4REC as a modulation scheme without good power and bandwidth efficiency. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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