The Suppression Method Of Inherent Interference In The Filter Bank Multi-carrier System

With the development of mobile Internet, users hope the communication service is faster and better so that they can enjoy a variety of applications. In order to realize high speed data transmission, orthogonal frequency division multiplexing (OFDM) technology is widely studied as one of the solutions.Therefore, it is widely used in a variety of communication systems. However, in the future communication scenarios, many systems will coexist in the limited spectrum resources. OFDM technology itself will cause higher influence on adjacent system because of high out of band radiation, and it uses the cyclic prefix resulting in loss of spectrum efficiency. These shortcomings make it not applicable to all communication systems. To solve these problems, a series of alternatives have been proposed, which are called the new carrier types. Filter bank multi-carrier technology is one of representatives.This dissertation summarizes four kinds of new waveform technology which are researched widely, namely FBMC, Generalized frequency division multiplexing, Universal filter multi-carrier, Filtered-Orthogonal frequency division multiplexing. This dissertation describes their characteristics and specific implementation methods, analyzes and compares them. On the basis of this, this dissertation mainly studies FBMC technology which has the most superior performance of out of band radiation.FBMC filters each sub-carrier individually and abandons the cyclic prefix.However, there is inherent interference in the system. In accordance with the characteristics of the inherent interference, FBMC must rely on offset quadrature amplitude modulation (OQAM). Due to complex response of multipath channel,the inherent interference cannot simply be overcome by OQAM. Therefore,FBMC has barriers in channel estimation and combining with multi-input and multi-output technology. The focus of this dissertation is to suppress the inherent interference of FBMC system. Firstly, a design scheme of FBMC system is proposed to employ QAM directly. The scheme uses two filters to deal with parallel sub-carrier, respectively. Therefore, the distribution characteristic of the inherent interference is changed, and the duration of the time domain symbol is shortened. Secondly, this dissertation proposes a scheme of preamble-based channel estimation, using a group of arbitrary QAM symbols as preamble sequence elements. The group of symbols is transmitted twice. The twice transmission are continuous and time independent. In the first transmission, each sub-carrier which is modulated by QAM symbol is exactly the same. In the second transmission, the adjacent sub-carriers are positive and negative staggered. Finally, the inherent interference of two transmission system has the same value but different sign. Therefore, the receiver can eliminate the inherent interference by combining the two received symbols to obtain accurate channel response values. Finally, FBMC system is abstracted by matrix model in this dissertation. In the matrix model, QAM symbols are transmitted directly in the transmitter, and receiver uses the classic strategy to suppress inherent interference in the system. Therefore, FBMC can use the multi-antenna technology, especially Alamouti coding.