Design And Implementation Of Speech Processing Techniques In2.4G Digital Wireless Intercom System

Digital wireless intercom, a kind of private net for mobile communication, isdifferent from mobile communication which include mobile phones, cordless phones,and so on. There is no charges to using digital wireless intercom, which hasadvantage in no wiring, easy networking, high security and high spectrum efficiency,and so on. Currently in some busy business places such as bank business hall, theirstaffs who always need one-on-one communication find that traditional or ordinarydigital wireless intercom equipment can not satisfy demands of low price andoperating convenience. Consequently, designing a kind of dedicated digital intercom,which not only can be operated by speech, but also has the characteristics of low costand low power, has important research significance and application value.This paper, which based on system structure and working principle of digitalwireless intercom, took low cost and low power into consideration to select hardware,then proposed to apply audio SOC (system on chip) which based on Cortex-M0processor architecture and2.4G RF chip to digital wireless intercom. Meanwhile thispaper not only designed the speech module hardware drivers, but also focused onstudying speech coding technique, speech packet loss processing techniques andspeech recognition technique. This paper specific work and contributions are asfollows:(1) In order to solve the question of reducing system power consumption, we notonly proposed the strategy, which contains controlling power consumption and takingadvantage of G.721speech coding in the system, but also establishing embeddedsystem power statistical model to prove that this strategy is effective.(2) For packet loss lead to poor call quality during speech communication, thispaper put forward a new solution, which combined interleaving technique,retransmission technique and repetition technique, by studying both of the speechpacket loss processing techniques and the characteristics of2.4G wireless RF chipNRF24L01. The actual test proved that this method not only can improve the speechquality of system, but also can increase the call distance of system. (3) This paper proposed a new idea which bases on speech recognition technique, itis applying speech recognition system to digital wireless intercom. This new ideaallow users to operate digital wireless intercom by speech when they are busy, as aresult staffs improve their efficiency.(4) We make the test board and take a series of tests including power consumption,speech quality and speech recognition rate. The test result proved this new digitalwireless intercom system can achieve the desired goals.