Study on Papr Reduction and Offset Qam in OFDM System
|School||University of Electronic Science and Technology|
|Course||Communication and Information System|
|Keywords||PAPR Shaping filter Channel estimation Time-frequency focusing properties|
Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) to its high spectral efficiency and resistance to frequency selective fading, the third generation terrestrial cellular mobile communication system enhanced long-term evolution (3GPP LTE-Advanced), new generation wireless LAN standard (IEEE 802.11n), wireless metropolitan area network standard (IEEE 802.16e / m) core wireless transmission technology. OFDM peak to average power ratio (Peak to Average the Power Ratio, PAPR) of the inter-subcarrier interference (Inter Carrier Interference, ICI) is still to limit the transmission performance of the OFDM system with the capacity to enhance the two factors. The above problems, the OFDM system PAPR suppression technology and complicated channel environment having the robustness of an orthogonal frequency division multiplexing system, which is based on interlaced orthogonal modulation orthogonal frequency division multiplexing system (OFDM / offset QAM , OFDM / OQAM). First the traditional reserved subcarrier PAPR suppression method is based primarily convex electrode optimization theory peak offset, but the the additional subcarrier overhead reduces the spectral utilization, and the high degree of complexity. In this paper, the analysis of WiMAX system sends the signal structure characteristics, reserved loopholes carrier PAPR suppression method. Order to reduce the degree of complexity of reserving the method of the null subcarrier, by analyzing the peak joint probability density function of the transmission signal, having a low complexity reserved empty carrier PAPR suppression method. In addition, the angle of departure from the high power amplifier nonlinear suppression, the traditional pre-distortion and PAPR reduction and not jointly optimized design. In the framework of the WiMAX system structure, combined with non-linear pre-distortion and reserved loopholes carrier joint suppression method. This article provides an overview of the generalized orthogonal frequency division multiplexing system conditions, the focusing properties of time-frequency and cell density analyzed OFDM / OQAM system based on the isotropic orthogonal transformation function. By analyzing the impact of multipath interference channel real number domain orthogonality condition of OFDM / OQAM, that traditional add cyclic prefix orthogonal frequency division multiplexing and channel estimation method using the system can not be directly used for the OFDM / OQAM system. This paper analyzes the OFMM / OQAM system pilot channel interference sources based ICI inhibition of low-complexity channel estimation method and joint iterative channel estimation and signal detection algorithm is used to eliminate the residual interference pilot reference signal. Finally, the time-frequency focusing properties by observing expansion Gaussian function (Extended Gaussian Function, EGF), found that the the expansion factor regulating EGF function can change the EGF function OFDM / OQAM system-based time-frequency focusing properties. Accordingly, this article discusses the focusing characteristics of the time domain OFDM / OQAM EGF function-based adaptive system, when the radio channel having a strong multi-path interference, the system to reduce the spreading factor of the EGF function, improve the OFDM / OQAM system; When radio channel has a strong inter carrier interference, the frequency of the function of the spreading factor of the system increases the EGF, the OFDM / OQAM system focusing properties. The above research results provide a way to meet the technology needs of next-generation mobile communication system physical layer orthogonal frequency division multiplexing system to achieve a stable high spectral efficiency transmission purpose complex channel environment, as IMT-Adavancd, IEEE 802.11, IEEE 802.16 wireless communication standards such as Evolved candidate.