Research On Emergency Communication Technology In Forest Fire Of The Forest Armed Forces

The forest armed forces was established in 1948,mainly responsible for forest fire prevention and fighting tasks.In the long-term forest fire fighting practice,it was found that:(1)The limited communication resources are unable to meet forest fire emergency communication needs.(2)The forest fire scene has a very serious background noise,seriously affecting the voice transmission.These have become bottleneck problems of the fire scene communication,seriously affecting organization and command of the forest fire fighting.Based on the above two shortcomings,it takes the cognitive radio(CR)technology to improve the utilization ratio of the existing spectrum and satisfy the needs of the forest fire emergency communication.The use of adaptive noise cancellation(ANC)technology to weaken the negative influence of the outside noise source,and improve the quality of the speech signal transmission.The techniques provide the experiences and references for the applied research of the forest fire emergency communication.The main contributions of this paper are as follows:1.Under different simulated fire scene channel conditions,BERs of Overlay,Underlay and hybrid Overlay/Underlay waveform are verified by simulation.In this paper,the RICEAN fading channel simulates the wireless channel environment of flat,wide grassland,farmland,wetlands and other visual areas in the forest fire fighting process;the RAYLEIGH fading channel simulates the wireless environment of high mountains and dense forests and other invisible areas;the AWGN fading channel as a reference channel;And Overlay,Underlay and Overlay / Underlay hybrid waveform sequentially are placed in AWGN,RAYLEIGH and RICEAN channels,simulation of bit error rates(BERs)by changing spreading codes and transmitting powers of the signal.The results show that hybrid Overlay/Underlay waveform performance > Overlay waveform performance > Underlay waveform performance.And as the signal power increases,the bit error rate of Overlay waveform is reduced,and the bit error rate of Underlay waveform is increased.Experimental verification of the Overlay/Underlay hybrid waveform is the optimal combination of Overlay waveform and Underlay waveform,more suitable for the fire scene channel conditions,to improve the utilization of spectrum in fire scene.2.In the background noise of different fire scene,the performance of adaptive noise cancellation(ANC)algorithm is verified by simulation.In this paper,noisy speech signals of fire scene serves as the research object and adaptive noise cancellation simulations based on LMS(least mean square),NLMS(normalized least mean square),RLS(recursive least square),BP(Back Propagation)and based on GA(genetic algorithm)optimized BP algorithm.The result shows that the BP algorithm with different training function,its noise reduction ability and convergence rate are not the same;BP algorithm of trainrp training function is the best on noise cancellation,BP algorithm of traincgf training function is the fastest on convergence rate.Based on GA optimized BP algorithm,its noise reduction ability and convergence rate have been further improved,significantly better than the BP algorithm.Experimental verification of based on GA optimized BP algorithm is more suitable for fire scene speech signal real-time denoising.