Reserch And Implementation Of Phasical Layer In Digital Interphone Based On DMR Protocal

Digital Mobile Radio is a new global standard for digital trunking communicationsystem published by ETSI.This paper mainly focuses on physical layer of DMR protocol including4FSKmodulation and demodulation, codec technology, timing and synchronization.This paper introduces4FSK technology which is the key technology of DMRprotocol in Physical layer. Modulation has two steps: baseband modulation and I, Qmodulation. This paper makes cosine table to realize I,Q modulation to control therunning time and meet real time requirement. Demodulation also has two steps:baseband signal recovery and making decisions. This paper gives an approach of bitsynchronization in this system. Bit synchronization has been done before demodulation.Decision threshold has great impact on the correctness of modulation algorithm. Thispaper introduces the combined method of calculating decision threshold based on a lotof engineering implemetations which achieves good results.Frame synchronization can handle timing aligned effectively between sender andreceiver. According to the characteristics of burst structure in DMR protocol, this papergives a method of frame synchronization.The OMAP-L138is the main processor of digital intercom. All the techniques inphysical layer have been implemented on DSP side of OMAP-L138. This paper alsointroduces some peripheral configurations in DSP of intercom. Finally, this paper givessome codec results and4FSK error rate.