Research On The Key Technology Of Multi-center Emergency Communication System

Single-center railway emergency communication system dates back no more than30years. It has provided effective communication support for emergency and disastermanagement. However, with the birth and expansion of high-speed railways andpassenger dedicated railways, the existing single-center emergency response system isno longer adequate for the demand and needs to be migrated to a multi-centeremergency command system. This function was particularly required for therenovation of communication system of dispatch command centers by companies likeRailway Corporation, and a number of government agencies like Railway Bureau.Analysis on the railway emergency communication shows the key technology indeveloping a multi-center communication system lies in the core function of soundsignal mixing, of which the implementation relies on two core algorithms:re-sampling algorithm and audio mixing algorithm.In this paper, we first introduce several key concepts and techniques of audiosignal process, transmission and exchange, such as sound waves, audio mixing, VoIP,soft switch, SIP protocol and RTP protocol. Following that we expound two audiore-sampling algorithms at our choice: linear and polynomial algorithms, based onanalysis of digital audio signal process and characteristics of WAVE format audiosignals. We compare the advantages and disadvantages of these two algorithms andconsequently determine the parameter settings. We then proceed to implement thepolynomial re-sampling algorithm and test it with detailed result analysis. In the thirdpart, we point out the difficulty of a direct implementation of Microsoft DirectSoundSDK in large-scale railway emergency communication system, and experiment onfour potential audio mixing algorithms in line with the design concept of DirectSound:linear mixing, amplitude-limited mixing, average mixing and weight audio mixing.The weight audio mixing algorithm is our recommended algorithm. It passes thesimulation experiments and result analysis. In conclusion part, we describe theprocess to develop a multi-center emergency communication system, comparedifferent patterns of mixing process and summarize the backbone structure of such asystem. The article researches the realization of the multicenter emergencycommunication system. Mock test results comply with anticipated target, which may provide theoretical and technical guidance for implementing audio mixing betweenmulti-center and multiuser calling groups.