Research On CMA Algorithm In MIOM-OFDM Systems

In the digital wireless communication systems, Inter-symbol interference is an importantfactor affecting the quality of communications. The main reason to produce inter-symbolinterference is the radio channel multipath effects. At present, the multipath effect is theprimary means to overcome channel adaptive blind equalization technique, blind equalizationtechnique does not require sending the training sequence can be adaptive to adjust the equalizertap co-efficient, Inter-symbol interference can be effectively removed. Constant modulusalgorithm (CMA) has the advantages, such as the computational complexity is moderate,robustness, etc. It is a good communication system of a blind equalization. CMA algorithm canbe perfectly applied to the system of constant modulus signals, but when applied to multi-modesignals (QAM signals) of the blind equalization of the system, due to the error criterion is notperfect, so the balanced results is not very ideal; On the other hand, the CMA algorithm, thephase information is not sensitive enough, so in the phase deflection channel equalization, theCMA algorithm can not correct the phase deflection.Orthogonal frequency division multiplexing (OFDM) technology is a multi-carriermodulation technology and multi-carrier orthogonal to each other. Efficient use of spectrumresources to support high-speed data transmission, and anti-multipath channel interference,therefore it’s generally considered as a key technology in the fourth generation mobilecommunication systems. MIMO technology uses multiple antenna technology, no need toincrease the antenna transmit power and channel bandwidth, can exponentially improve thecapacity of the wireless channel. A combination of both, the formation of MIMO-OFDMsystems, can effectively suppress interference and resist fading channel, which greatly improvethe system’s channel capacity and transfer rate, has also become one of the realization ofwireless channel high-speed data transmission of the most promising solutions.So here we mainly focus on the study of the performance of the constant modulusalgorithm in MIMO-OFDM systems. First of all, we will introduce the basis of theMIMO-OFDM technology and the constant modulus algorithm, and next by four of the moststeep decline in the performance of the constant modulus algorithm (SDCMA) were studiedand simulation. Then the constant modulus algorithm used in MIMO-OFDM systems, mainlyfocus on the convergence rate of four kinds SDCMA algorithm in MIMO-OFDM systems, thesteady-state error, as well as the anti-jamming capability. In the end, the CMA algorithm used in QAM communication systems, convergence is slow, steady-state error, can not overcome theshortcomings of the phase deflection, the CMA algorithm has been improved. And was verifiedby analysis and simulation, the improved algorithm has the advantages as fast convergence,small steady state error, and also can correct phase deflection.