Study On Integer-Forcing Algorithm In CDMA/MC-CDMA System

Multi-Carrier Code Division Multiple Access (MC-CDMA) is combining the Orthogonal Frequency Division Multiplesing (OFDM) technique and Code Division Multiple Access (CDMA) technique to enhance the capability of high data rate service processing and decrease the data rate of single-link CDMA. Due to the advantages inherited from CDMA and OFDM technique, MC-CDMA technique exhibits advantages in the resistance of inter-symbol interference and frequency selective channel as well as the high spectral efficiency. In addition, because the multicarrier modulation and demodulation can be implemented by means of Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT), the system complexity is reduced significantly.Firstly, the fundamental principles and system model of CDMA and OFDM are introduced in this thesis, Secondly, it made a concrete analysis of zero-forcing (ZF) algorithm, minimum mean square estimator (MMSE) algorithm, integer-forcing (IF) algorithm, sphere-decoding (SD) algorithm and Maximum-likelihood (ML) algorithm. Due to the traditional linear detection algorithm (ZF, MMSE) with low computational complexity and the performance is far from ideal, the integer-forcing algorithm is applied to the CDMA system and MC-CDMA system. Moreover, by putting the spread matrix and the channel coefficient matrix together into a new joint channel matrix, the despreading at the receiver is avoid and the system complexity is reduced.Under the condition of the Multipath Rayleigh flat-fading channel, comparative analysis of the above several kinds of algorithm by Matlab simulation is performed, Finally, the simulation results show that the bit error rate (BER) of integer-forcing algorithm can approach the maximum-likelihood (ML) performance with a few decibels, and largely outperforms traditional linear algorithms.