Researches On Blind OFDMA Signal Decoding Algorithm Based On Blind Source Separation

With the rapid development of wireless communication technology,such as the rapid growth of the mobile phone users and the rapid development of a variety of emerging wireless multimedia services,the demand for spectrum resources is increasing as same as higher requirements for transmission rate,which is a great challenge for the limited wireless spectrum resources.It is urgent to search for some effective techniques to improve the spectrum utilization in the next generation of wireless communication.Having the advantages of high efficiency of spectrum utilization and fast speed of uplink transmission,the orthogonal frequency division multiplex access technology has become one of the key technologies in the future high speed wireless communication system.Thus,how to improve the decoding performance of orthogonal frequency division multiplex access has become more and more important.The multi input and multi output system can enhance the spectral efficiency by the using space-multiplexing technique,also,the speed of data transmission and channel capacity is effectively improved,it has gradually become a hot research technology in wireless communication system.In the new generation of wireless communication networks,the combination of orthogonal frequency division multiplex access and multi antenna transceiver is recognized as the main signal transmission and process techniques.As such,this thesis studies both the OFDMA blind decoding algorithm in Gauss noise channel which use single antenna and the OFDMA blind decoding algorithm in Rayleigh fading channel which use multi antennas.In this paper,we analyze the background and current situation of OFDMA decoding algorithm firstly,and analyze the common channel estimation and decoding algorithms.As the comparison object,we simulate and analyze these algorithms.For the shortcomings of the existing OFDMA decoding algorithm,The OFDMA decoding algorithm based on blind source separation under the environment of both single antenna and multi antenna is proposed.Under the condition of single antenna,The existed signal decoding methods need to maintain synchronization before decoding the signal,according to the characteristics that OFDMA signal can be regarded as the space projection of the source signal in the IFFT matrix,this paper propose the blind decoding algorithm based on blind source separation according to the characteristics of OFDMA signal.The proposed algorithm needn't to keep synchronization and estimate carrier frequency offset at the receiving end,which reduces the influence caused by the synchronization and the estimate carrier frequency offset error.The analysis results show that the blind source separation method based on blind source separation has better performance than the traditional decoding method based on FFT.Under the circumstance of multi antenna,for the independence of channels from each user to antenna,the current algorithms need to estimate the channel information before decoding based on FFT.Once the channel estimation is not accurate,the performance of OFDMA decoding based on FFT will be rapidly decreased.What's more,channel estimation requires the pilot sequence which reduces the transmission efficiency.Under the rayleigh fading channel,this paper build the blind source separation receiving model according to the characteristics of multi antenna OFDMA signal,which can complete demodulation and decoding without pilot sequences.In this paper,compared with the traditional OFDMA decoding algorithm based on FFT,the proposed OFDMA blind decoding algorithm based on blind source separation increases the channel gain and improves the decoding performance by retaining the cyclic prefix.