| In today’s high-tech warfare, electronic warfare which is characterized byinformation intercept has become an indispensable part of the war. In the process ofinformation intercept, the third part receieves and demodulates all kinds ofnon-cooperative signals to obtain the other part information without affecting thecommunication between the transceiver and receiever. In this non-cooperativecommunication environment, people who intercept information often only know thereceived signals and some limited priori information. So how to process the receivedsignal efficiently become one of the most difficult problems in non-cooperativecommunication. In this dissertation, we mainly study the iterative receiving technologyof high order QAM under the conditions of non-cooperation receive, by using iterativeequalization technology to improve the high order QAM system performance.The current rapid development of information technology promotes the progressof modern communication technology, modern society tight demands for informationneeds higher and higher information transmission rate. So high-order modulation withhigh spectrum utilization efficiency makes it subject to a wide range of applications,128QAM,256QAM and1024QAM modulation has a wide range of applicationscenarios. In this dissertation, we mainly study the iterative receiving technology ofhigh order QAM under the conditions of non-cooperation receive, by using iterativeequalization technology to improve the high order QAM system performance.In the wireless channel, due to the impact of frequency offset and multipath, thereceived signals are serious distorted. The communication environment is even worsein the non-cooperative scenario, lower signal-to-noise ratio and no predeterminedtraining sequence making it more difficult to receive. This dissertation mainly focuseson the problems of synchronization and equalization of high order QAM signal,through iterative equalization and demodulation technology to improve theperformance of the system. While it is more difficult to solve these two problems in thenon-cooperatives system. This dissertation introduces the joint synchronization,iterative equalization and decoding technology to improve the performance of the system.In the first chapter, we describe the background of this thesis, and introduce theresearch status about the technology in this dissertation, making the direction of theresearch clarified. In chapter two, we solve the high order QAM systemsynchronization problem in the non-cooperatives scenarios, mainly focus on frequencyand phrase offset capture in cross constellation system. Besides, we also do some workon timing synchronization algorithm. All above algorithms are applied in thenon-cooperatives system which does not need training sequences and probing data. Inchapter three and four, how to iterative modulate in non-cooperatives system isinvestigated. In cooperative scenario, there are some training sequences and probingdata to adjust the equalizer coefficients and estimate parameters of the wireless channel.However, there are not training sequences and probing data, so we can not usetraditional cooperatives method to demodulate. Thus we adopt adaptive equalizer toprocess the data preliminary, and then use the known data to estimate parameters ofchannel. With these parameters, we can improve the performance of thecommunication system by using Turbo iterative equalization technology. By so doing,we not only break through the situation of no training sequences and probing data butimprove performance, taking advantages of both equalization technologies. At thebeginning of fifth chapter, PPP frame format is introduced. It is pointed that incommunication system there are many fixed data in a frame. We can use these data toimprove the performance of the system. The difference between the training sequencesand these fixed frame information is introduced. Then how to make use of these knownfixed frame information to improve performance is discussed. |
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