Font Size: a A A

Research On Low-Complexity Iterative Detection Algorithm For Continuous Phase Modulation

Posted on:2014-02-05Degree:MasterType:Thesis
Country:ChinaCandidate:G ZhangFull Text:PDF
GTID:2268330401967022Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
Continuous phase modulation (CPM) is a non-linear modulation technique. It hascharacteristics of continuous phase and constant envelope. Thus the spectrum is morecompact, the bandwidth efficiency is more higher, and the ability to anti-fading is morestronger. Therefore relatively inexpensive and high efficiency nonlinear power amplifierof the class C can be adopted to greatly reduce the cost of amplifier and decrease thepower consumption of the terminal. Meanwhile, CPM has a memory characteristic, itcan be equivalent to an encoder, thus iterative detection can be adopted which combinedwith channel coding. The general CPM receiver is complex, thus we need to consider toreduce the complexity of the receiver and to improve the system performance byiterative detection at the same time. In this article, we mainly study the low-complexityiterative detection algorithm for CPM in wireless communication systems.Firstly, the research background and the significance of this article are elaborated.Then the previous study of iterative detection for linear modulation and CPM areanalyzed. The contents of the research and structure arrangements are introducedbriefly.Secondly, a low-complexity in time domain iterative detection algorithm based onprecoding for binary CPM is studied. Combining with the differential precoding forCPM and the Laurent’s decomposition of binary CPM, the coefficient of waveform isonly associated with the transmission symbol. Therefore it largely eliminates the ownmemory of CPM and greatly simplifies the complexity of receiver demodulation. TheISI which comes from both the channel’s memory and decomposition of CPM arestudied, and a new equivalent channel for CPM equalization is proposed. Then theMMSE equalization and SFIC equalization with CPM is compared and studied, a newiterative detection algorithm base on differential precoding for CPM is proposed.Moreover, the simulation results, the complexity of algorithm and the convergence ofiteration indicate that the SFIC iterative equalization has lower computationalcomplexity than MMSE iterative equalization and the performance of SFIC algorithmcan approach the performance of MMSE algorithm through multiple iterations. Thirdly, a low-complexity iterative detection algorithm based on instantaneousfrequency estimation for M-ary CPM is studied. Instantaneous frequency estimationalgorithm can effectively obtain the phase of the current symbol by estimating thefrequency so that to compute the maximum likelihood symbol probability of each state.Then a new M-ary CPM non-coherent iterative detection algorithm is proposed. Thesimulation of the power spectrum of CPM and iterative detection performance of M-aryCPM under the same bandwidth are given. Compared with coherent iterative algorithmbase on the grid-demodulation, the instantaneous frequency estimation algorithm has alower complexity.Lastly, a low-complexity iterative detection algorithm based on the phase forwardin cooperative relay system for CPM is studied. A non-coherent detection usingdiscriminator of CPM is studied. Based on the conditional probability density function,the output of the log likelihood information is given through theoretical derivation, andthen a new non-coherent CPM iterative detection algorithm is proposed. Moreover, theiterative detection performance using different relay mode under the fading channel arecompared. The performance of phase forward which discards the amplitude informationin relay node is worse than amplify forward. But the performance of phase forward baseon the dual antenna selection which maintains the continuous phase characteristics isbetter than amplify forward.In conclusion, we mainly study the low-complexity iterative detection algorithm ofCPM and prospect the low-complexity iterative technology of CPM for further study.
Keywords/Search Tags:wireless communication, continuous phase modulation (CPM), iterativedetection, low-complexity
PDF Full Text Request
Related items