Research On Algorithm For GMSK Radio Digital Receiver

This thesis comes from a digital buoy transformation project. With thedevelopment of digital receiver,it weakens the disruption of the underwater acousticdata in the wireless transmission,but it is still unable to meet the requirements of therising air anti-submarine precision.Digital buoy is on the sea.The marinetimeradiowave propagation environment is complex,digital communications prone toerror,so it’s necessary to correct error for digital communications at sea.In thisthesis,firstly,the maritime channel characteristics are analyzed and researched,we focuson small scale fading.Martime channel obeys Rice distribution and K-factor isestimated.Secondly,the algorithms of modulation and demodulation of GMSK digitalreceiver are researched.The GMSK Linear approximation modulation algorithm isresearched, and the derotation demodulation algorithm is researched.Synchronizationalgorithm in the derotation process is the algorithm of the energy window. The BERperformace of linear approximation modulation is simulated,and it’s easy to studychannel coding followed.Then the channel coding of GMSK digital receiver isresearched,the encoding and decoding of RS code,LDPC code and the RS and LDPCconcatenated codes are respectively studied.PEG algorithm is used to construct QC-LDPC,RU linear algorithm is used to encode,and BP algorithm is used to decode.BPalgorithm is optimized on Rice channel,and cascaded RS and LDPC codes areproposed. The performances of three codes are simulated.Finally,GMSK linearapproximation modulation algorithm is simulated on the maritime channel.And theperformances of three codes are simulated on the maritime channel.The result showsthat RS code is better at dealing with unexpected errors.When the signal-to-noise ratiois low,the BER is increased.The advantages of RS code show with high signal-to-noiseratio.Whether the channel is good or poor,LDPC code shows a good error correctionperformance.The concatenated RS and LDPC codes also have a good error correctionperformance,which can meet the demand of greater data throughput.