Nonlinear Soft-Output Signal Detector Design and Implementation for MIMO Communication Systems with High Spectral Efficiency

Author(s):  
Sizhong Chen ◽  
Fei Sun ◽  
Tong Zhang
T-Comm ◽  
2021 ◽  
Vol 15 (3) ◽  
pp. 50-58
Author(s):  
Sergei S. Pechnikov ◽  
◽  
Sergey A. Sherstyukov ◽  

Currently, increasing the speed of information transmission in wireless communication networks is a topical issue. The growing demand for spectral efficiency in radio communication systems gives rise to the introduction of signals with amplitude-phase modulation. Despite all its advantages, signals with vector modulation are characterized by a change in the envelope, which makes it impossible to use highly efficient nonlinear power amplifiers. Energy efficiency is clearly a critical factor in portable radio communications systems, where power supplies are often used in small packages, and the presence of energy losses due to heat dissipation is a significant drawback that requires additional cooling systems. In this connection, when developing modern radio communications, radio engineers are faced with the contradictory task of achieving maximum energy and spectral efficiency. One of the approaches to reduce nonlinear distortion of vector modulation is the use linearization schemes for nonlinear power amplifiers. This work is devoted to increasing the energy and spectral efficiency of signals with amplitude-phase modulation. The article discusses the restrictions imposed on the input signals for the method for optimizing of structure of spectrally effective radio signals with vector modulation, the formation of the output signal, the influence of phase shifters phase imbalance on p/2, the index of balance modulation, and the analysis of parametric sensitivity. The possibility of using quadrature modulators to form components with phase modulation and constant envelope is considered. This method was simulated and the effect of phase imbalance on the shape of the output signal constellation was revealed.


Author(s):  
KAMALA KANNAN P ◽  
GURU VIGNESH B ◽  
INIYAN P A ◽  
ILAVARASAN T

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems such as standard 802.11a/b/g/n, Digital Video Broad casting Television (DVB-TV), and Long Term Evolution (LTE) in the next mobile generation, due to its capacity in solving the problems of Inter-Symbol Interference (ISI) caused by the effects of the dispersive channel. Very recently researches focus on applying OFDM technology in optical fiber communication systems. Optical OFDM is well suited for high speed transmission systems with high spectral efficiency and attracted significant attention from the optical communication community. One of the major issues that degrade the performance of optical OFDM networks is its fiber non-linearity. Fiber non-linearities represent the fundamental limiting mechanisms to the amount of data that can be transmitted on a single optical fiber. Non-linear effects arise as optical fiber data rates, transmission lengths, number of wavelengths, and optical power level increases. Therefore, the effect of non-linearity in high data rate optical networks needs to be controlled to enhance link performances. In this paper, a nonlinearity compensation technique (Hermitian Symmetry) is implemented to improve the performance of OFDM based optical networks. This would provide high spectral efficiency, low ISI and very good Bit Error Rate (BER) performances without increasing the complexity of the network. The optical OFDM transmission system with fiber non-linearity compensation is simulated using Virtual Photonics Integrated (VPI) software.


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