Abstract
In Digital Video Broadcasting-Handheld (DVB-H) devices for cyber-physical social systems, the Discrete Fractional Fourier Transform-Orthogonal Chirp Division Multiplexing (DFrFT-OCDM) has been suggested to enhance the performance over Orthogonal Frequency Division Multiplexing (OFDM) systems under time and frequency-selective fading channels. In this case, the need for equalizers like the Minimum Mean Square Error (MMSE) and Zero-Forcing (ZF) arises, though it is excessively complex due to the need for a matrix inversion, especially for DVB-H extensive symbol lengths. In this work, a low complexity equalizer, Least-Squares Minimal Residual (LSMR) algorithm, is used to solve the matrix inversion iteratively. The paper proposes the LSMR algorithm for linear and nonlinear equalizers with the simulation results, which indicate that the proposed equalizer has significant performance and reduced complexity over the classical MMSE equalizer and other low complexity equalizers, in time and frequency-selective fading channels.
Highlights
The Digital Video Broadcasting-Handheld (DVB-H) technology is the superset of the Digital Video BroadcastingTerrestrial (DVB-T) systems for handheld devices applied in a cyber-physical human organization to share multimedia content
LSQR is equivalent to the Conjugate Gradient (CG) method applied to the standard equation, where (AT A + λ2I )x = AT b, which has the property of reducing rk monotonically, where rk = b − Axk is the residual for the approximate solution xk
SIMULATION RESULTS The non-encoded BER performance of the Discrete Fractional Fourier Transform (DFrFT)-OCDM and the Orthogonal Frequency Division Multiplexing (OFDM) system with the different Least-Squares Minimal Residual (LSMR) Equalizers are investigated by means of simulation over 105 multicarrier blocks
Summary
The Digital Video Broadcasting-Handheld (DVB-H) technology is the superset of the Digital Video BroadcastingTerrestrial (DVB-T) systems for handheld devices applied in a cyber-physical human organization to share multimedia content. The complexity of the DFrFT-OCDM system is almost the same as the OFDM system [2], [8], [17], and both cannot diagonalize the time-variant channel matrix. The equivalent Na × Na channel matrix and the noise vector in the fractional domain are given by Hα = FαHF −α and z = Fαz, respectively Both of Hand Hα are nondiagonal subcarrier channel matrices resulting of introduce ICI, which is the case when the dispersive channel comprises multipath doubly dispersive channel. The MMSE Equalizer gives the best performance in all linear Equalizers [18]; it is very complicated due to the existence of the channel matrix inversion, which needs O(Na3) complex operations [27], ZF is regarded as unpractical for high values of Na, which is the case DVB-H. Low complexity Equalizers will be examined with DFrFT-OCDM and OFDM based on the LSMR iterative algorithm
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