Transmit Power Allocation On Subcarrier For Underwater Acoustic Multicarrier-CDMA Based On Improved Genetic Algorithm

With the increasing shortage of land resources and the improvement of human science and technology,countries of the world has paid more attention to researching the ocean.Underwater acoustic communication is one of the key subject of marine research.However,the marine environment are full of interference,characteristics of underwater acoustic channels become strong dynamic,variability and unpredictability,and such characteristics have a bad effect on the spread of wireless signals.Thus it will be inefficient when we use CDMA(Code Division Multiple Access)or OFDM(Orthogonal Frequency Division Multiplexing)directly under the water.MC-CDMA(Multicarrier code-division multiple-access)is combining scheme of OFDM modulation and CDMA scheme,its advantages including strong anti-narrow interference ability,anti-multipath interference ability,high spectrum utilization efficiency and large system capacity.Predictably,MC-CDMA is considered to be very promising and suitable for underwater acoustic communications.Both the quality of communication and energy consumption of system need to be considered,to reduce cost and extend service life of underwater node.Therefore,this paper will focus on the subcarrier power allocation of underwater acoustic MC-CDMA,attempt to optimize the power allocation scheme by genetic algorithm.The main research work of this paper can be summarized as follows:1.Analyzed defects of existing MC-CDMA subcarrier power allocation algorithm,consider a way that to reduce the computational complexity and optimize the performance of system by using the genetic algorithm.2.An improved genetic algorithm was proposed for the problem of optimizating subcarrier power allocation,which combined two coding methods and adding optimization idea of particle swarm algorithm to improve the search speed and precision.3.Proposed a system model of MC-CDMA subcarrier power allocation based on genetic algorithm.A multi-objective optimization fitness function was designed to evaluate the result,transmit power and SINR of the signal were both the object to be optimized.4.The existing method and the improved method have been simulated,and single target and multi-objective optimization scene were tested respectively.The experimental results show that the computational complexity of genetic algorithm were less than the theoretical formula,especially in the case of large number of subcarriers.The proposed improved genetic algorithm can achieve better error performance and higher channel capacity while reduces the system energy consuming.