Research On Multi-carrier Code Division Multiple Access Wireless Communication Technologies

A new generation wireless communication system should support the of higher information peak transmission rate. It also should be more flexible to assist changeable rates, more kinds of services and be adaptive to worse environment. Orthogonal frequency division multiplex is the key technology in the field of multi-carrier technology. In the third generation of mobile communication, code division multiple access is a representative technique. Combination of these two is a competitive scheme.Multi-carrier orthogonal frequency multiplex is a kind of modulation technology. To combine with different multiple access method, it can provide service to multiple users. Multi-carrier code division technology is a combination of CDMA and OFDM. It possesses more advantages of these two technologies. It is not only resistant to inter-symbol inference caused by effects of multi-path, but also able to support large amount of users.This paper started with existing algorithms and theories of related multi-carrier code division multiple access wireless technologies. Then emphases on power control, synchronization technologies and system architecture are researched. Main research and innovation contents are as following:1. Reverse-link predictive power control algorithm has been deeply researched in this paper. Under the quickly declining channel situation of a fast moving mobile platform, the backward closed loop algorithm cont rolled by power can bring relatively great deviation. This study, according to the frame structure of reverse link power control order in multi-carrier DS-CDMA, utilized a predictive power control algorithm. The algorithm can be used to estimate the condition in every sub-carrier channel and predict the receiving power of the next carrier ahead. The algorithm can also compensate for fading in the sub-channel and improve bit error rate performance of the system and the system's capacity.2. A new rapid step-changed PN code sequence algorithm has been researched. We have designed a new closed-loop coherent step-changed acquisition scheme. In this paper we use a novel idea to use an auxiliary signal for correlation within the income signals. Synchronization of pseudo noise code is crucial technique to multi-carrier code division multiple access receiving systems. Average acquisition time based on Markov chain system structure has been analyzed. The new algorithm can still maintain good performance even under conditions of severe signal to noise ratio, and the synchronization time is also reduced greatly.3. A modified multi-carrier direct sequence code division multiple access system is presented in this paper, in which the transmitter maximizes the orthogonal of sub-carrier in time and frequency domain by dealing with the user's pseudo noise sequence. Multi-carrier systems are much more sensitive to frequency offset, which results in inter-carrier interference and affects symbol synchronization. The performance of combined frequency diversity and time diversity can be gained by using time-frequency RAKE receiver. Simulation results show that bit error rate performance of such system structure is greatly improved.Inclusion, deep research of multi-carrier code division multiple access technologies in wireless telecommunication in the fields of power control, synchronization technologies and system architecture has been done in this paper. New algorithms had been proposed, simulation experiments test their good results.