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We propose a message-passing algorithm of joint channel estimation and decoding for OFDM systems, where expectation propagation is exploited to deal with channel estimation. Specially, the message updating is formulated into a recursive form. As a result, for system with K subcarriers and L channel taps, only O(K + L) messages need to be tracked, and meanwhile they can be efficiently calculated using...
In this paper, the problem of sampling-jitter estimation in OFDM full-duplex radio transceivers is addressed. The sampling-jitter estimation is very challenging, because the effects are very small, but still high enough to be a problem in full-duplex radios. The proposed sampling-jitter estimation method is based on estimating only the most significant frequency components of the sampling jitter....
Underwater acoustic channels are wideband time-varying channels, which can be well-described by a multi-scale multi-lag channel model. In this paper, a robust method to estimate the channel parameters from noisy measurements is proposed. The proposed method computes the multiple Doppler scales, delays, and channel attenuation gains corresponding to different propagation paths. In this work, we adapt...
In this paper, we investigate maximum likelihood equalization (MLE) for a large-scale antenna (LSA) system with single-carrier (SC) modulation over Rician fading channels. Orthogonal frequency division multiplexing (OFDM) is usually used to deal with frequency selectivity of wireless channels. However, for a wireless system with large-scale antennas in a Rayleigh fading channel, by combining the received...
In this paper, we present a robust approach to estimate communications channel in OFDM systems exploiting the sparsity of the channel impulse response (CIR) commonly found in multi-path channels. The CIR is found as the solution of a regularized optimization problem where we minimize the least absolute deviation of a residual signal while, at the same time, encourage sparsity in the solution by an...
Two novel subspace-based blind channel estimation methods for orthogonally coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with more than two transmit antennas are proposed in this paper. The proposed methods exploit the null space induced by the orthogonal space-time block codes (OSTBC). They can be applied to systems with one or more receive...
This paper presents a software-based implementation for the MIMO transmitter baseband processing conforming to the IEEE802.11ac standard on a DSP core with vector extensions. The transmitter is implemented in four different transmission scenarios, which include 2×2 and 4×4 MIMO configurations, yielding beyond 1Gbps transmit bit rate. The implementation is done for the frequency-domain processing and...
We investigate sampling and detection of orthogonal frequency-division multiplexing (OFDM) signals with unknown carriers at sub-Nyquist rates. Efficient acquisition and processing of such broadcast signals is a challenge but constitutes a crucial part of enabling cognitive radios. In order to alleviate both the analog and digital burden when treating wideband signals, we adapt the modulated wideband...
Many alternative modulation schemes have been investigated to replace OFDM for radio systems. But they all have some weak points. In this paper, we present a novel modulation scheme, which minimizes the predecessors' drawbacks, while still keeping their advantages.
Directional modulation (DM) can be regarded as a new frontier in physical layer communication security. This new technique uses an antenna array as a spatial encryption system which partitions the surrounding space into regions where the transmission is either perfectly intelligible or intentionally obfuscated. Still, energy and spectral efficiencies of current DM systems as well as their cryptographic...
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