Chaos Communication System using MIMO Technique Sung-Wook Yoon, Jun-Hyun Lee, and Heung-Gyoon Ryu Department of Electronics and Engineering, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea magi11@naver.com, toogee89@nate.com, ecomm@cbu.ac.kr Abstract— The security of chaos communication system is superior to other digital communication system, because it has characteristics such as non-periodic, wide-band, non- predictability, easy implementation and sensitive initial condition. However, chaos communication system increases the number of transmitted symbols by spreading and transmitting information bits according to characteristic of chaos maps. So the research that improves data transmission speed is necessary for chaos communication system. If many antennas are applied to chaos communication system, the capacity of data is proportional to the number of antenna.so it is good way applying multiple-input and multiple-output (MIMO) to the chaos communication system. In this paper, we propose the correlation delay shift keying (CDSK) using 2 ´ 2 MIMO technique and evaluate BER performance over Rayleigh MIMO fading channel. Lastly we evaluate BER performance applying the boss map with 2x2 MIMO using MIMO detection algorithm such as zero forcing (ZF) and minimum mean square error (MMSE). Keywords— Chaos Communication System; CDSK; MIMO; Zero Forcing; MMSE; I. Introduction Previous digital communication technology continually used a linear system. However, as this technology reached basic limit, people started to improve performance of nonlinear communication systems applying chaos communication systems to nonlinear systems [1]. Chaos communication systems have the characteristics such as non- periodic, wide-band, non-predictability and easy implementation. Also, chaos communication system is decided by initial conditions of equation, and it has sensitive characteristic according to initial condition, because chaos signal is changed to different signal when initial condition is changed [2-3]. Chaos signal is expressed as randomly and non-linearly generated signal, but it is possible to predict in principle. And it is possible to determine value of the future by value of the past. So, if initial conditions of chaos signal is not exact, users of chaos system are impossible to predict the value of chaos signal because chaos signal has sensitive characteristic about initial conditions [1][4]. As these characteristics, the security of chaos communication system is superior to digital communication system. Due to security and advantage, chaos communication system are being studied continuously. Look at existing research, in order to solve disadvantage that bit error rate (BER) performance of this system is bad, chaos communication system is evaluated the BER performance according to chaos maps, and find a chaos map that has the best BER performance [5]. In addition, chaos users evaluate the BER performance according to chaos modulation system [6-7], and propose a new chaos map that has the best BER performance according to analysis of probability density function[8]. Also, studies about security and anti-jamming of chaos communication system was studied [9-10]. Chaos communication system has many transmitted symbols, because information signal is spread according to the characteristic of chaos map. So, study of chaos system for data rate improvement is necessary. MIMO(Multi Input Multi Output) system transmit data by several paths using several antennas. And, in receiver part, it is a technique which can reduce interference by detecting received signal at each path, and make better each data rate. MIMO system increase the capacity of data communication in proportion to number of antenna, and provide the high data processing Speed[11-12]. Therefore, study that MIMO system is applied to chaos communication system is important. MIMO detection algorithm is necessary in receiver part when MIMO system is used because signal that transmit from different antenna is added to desired signal. Also, each MIMO detection algorithm is necessary to evaluate and find MIMO detection algorithm that has good performance, because BER performance is different according to MIMO detection algorithm In this paper, in Rayleigh fading channel, BER performances of CDSK system that is applied 2x2 MIMO with Zero Forcing and MMSE evaluate. Also, BER performances of CDSK system that is applied 2x2 MIMO with MIMO detection algorithm is evaluated, and we compare BER performance of Zero Forcing and MMSE. At existing study, we proposed a novel chaos map in order to improve the BER performance[8], and we named a novel chaos map "Boss map". And we evaluate the performance of Zero Forcing and MMSE when 2x2 MIMO is applied to CDSK using Boss map. II. System Overview Fig. 1. Transmitter of CDSK system. ISBN 978-89-968650-3-2 579 February 16~19, 2014 ICACT201