Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Precoding and Transmitter-Side processing techniques for multiuser MIMO OFDM systems with special emphasis on the PAPR problem | Wunder et al. EURASIP Journal on Advances in Signal Processing 2011 2011 59 http content 2011 1 59 o EURASIP Journal on Advances in Signal Processing a SpringerOpen Journal EDITORIAL Open Access Precoding and Transmitter-Side processing techniques for multiuser MIMO OFDM systems with special emphasis on the PAPR problem G Wunder 1 RFH Fischer2 S Litsyn3 and JS No4 Green information technology has significantly fuelled the discussion about energy efficiency in information networks. Already today energy cost of network operation can make up as much as 50 of the total operational cost. Notably by the complexity of networks in general the efficiency problem is hard to tackle on a global scale but entails several important sub-problems. One of these sub-problems is the energy efficiency of the high-power amplifier HPA at the very end of the radio frequency chain of the physical layer 1 . The HPA consumes a major fraction of the total energy budget of which depending on the efficiency class still much is dissipated as thermal energy and therefore wasted. While smart HPA design can alleviate much of this process there is an intrinsic problem which depends on the form how the HPA is operated high fluctuations of the input signal-typically quantified by means of the peak-to-average power ratio PAPR -enforce operating points typically well below an acceptable efficiency region. This problem becomes particularly serious in multicarrier systems such as OFDM and is the focus of this special issue. The PAPR problem brings up several challenges for the system designer. One challenge is to adjust HPA design parameters on RF level which includes pre-distortion techniques as well in some specific way here the tradeoff between power efficiency on the one hand and tolerated nonlinear distortions on the other hand will affect the overall transmission system. It is still unknown how to quantify this effect by a suitable metric. Moreover the optimal parameters .
