Jun Tao

• PhD
• University of Missouri

In this paper, we propose an approximate Bayesian soft symbol detector (SSD) for multi-input multi-output (MIMO) orthogonal frequency division multiplexing underwater acoustic communications over fast time-varying channels. It is enabled by vector approximate message passing (VAMP) algorithm coupled with expectation-maximization (EM) technique, thu...

The channel estimation (CE)-based vector approximate message passing (VAMP) soft equalizer (SE) has been proven to be an excellent technique of eliminating the inter-symbol interference (ISI) in single-carrier underwater acoustic (UWA) communications. It is attributed to the expectation propagation (EP)-like self-iterative mechanism between an inne...

Channel equalization plays a crucial role in single-carrier underwater acoustic (UWA) communications. Recently, a frequency-domain turbo equalization (FDTE) scheme enabled by the vector approximate message passing (VAMP) algorithm, was proposed, and it outperformed classic linear minimum mean square error FDTE at acceptable complexity cost. The ope...

The sparse adaptive algorithms under maximum correntropy criterion (MCC) have been developed and available for practical use due to their robustness against outliers (or impulsive noises). Especially, the proportionate updating (PU) mechanism has been widely adopted in MCC algorithms to exploit the system sparsity. In this paper, we propose a propo...

Sparse recursive least squares (RLS) adaptive filter algorithms achieve faster convergence and better performance than the standard RLS algorithm under sparse systems. Existing methods are designed by either incorporating a sparse regularization term, e.g., l1-norm, into the standard RLS cost function or introducing a proportionate matrix into the...

Vertical underwater acoustic (UWA) communications play a crucial role in deep-sea applications. A vertical UWA channel generally features a moderate multipath but with time-varying Doppler shifts as well as loud impulsive noise. To achieve a robust vertical single-carrier UWA communication, this paper proposes an enhanced iterative receiver. First,...

In this paper, the sparse direct adaptive equalization based on the recently developed proportionate recursive least squares (PRLS) adaptive filtering algorithm is investigated for multiple-input multiple-output (MIMO) underwater acoustic (UWA) communications. First, performance analysis is made for the PRLS, and simulation results show its gain ov...

The proportionate updating (PU) mechanism has been widely adopted in least mean squares (LMS) adaptive filtering algorithms to exploit the system sparsity. In this paper, we propose a proportionate recursive least squares (PRLS) algorithm for the sparse system estimation, in which, an independent weight update is assigned to each tap according to t...

In the cableless seafloor observation networks (SONs), the links among network nodes rely on underwater acoustic communication (UAC). Due to the energy constraint and the high-reliability requirement of the cableless SONs, the noncoherent UAC has been a preferred choice, even though a noncoherent UAC scheme generally suffers from low spectral effic...

The sparse direct adaptive equalization technique recently received many attentions for single-carrier underwater acoustic communications. By taking advantage of the sparse (nonuniform) structure of a direct adaptive equalizer (DAE), one obtains a sparse DAE with improved performance and/or reduced complexity compared with its nonsparse counterpart...

The vector approximate message passing (VAMP) soft frequency-domain equalizer (SFDE) has been proposed for turbo equalization. It consists of an inner soft equalizer (ISE) and an inner soft slicer (ISS), which iteratively exchange block-wise extrinsic information to improve the equalization performance, analogous to the outer turbo iteration betwee...

The sparse direct adaptive equalizer (DAE) has recently attracted much attention in underwater acoustic (UWA) communications for its improved performance compared with conventional non-sparse DAEs. The recursive least squares (RLS) type sparse DAEs were barely studied, mainly due to their high complexity despite fast convergence. This letter presen...

The high peak-to-average power ratio (PAPR) and lack of frequency diversity are two well-known issues with orthogonal frequency-division multiplexing (OFDM) modulations, especially over underwater acoustic (UWA) channels. The precoding (spreading) technique is a viable way to simultaneously address the aforementioned issues, and it has long been re...

The discrete Fourier transform (DFT) precoded orthogonal frequency-division multiplexing (OFDM) has been adopted as the uplink transmission technique in the long-term evolution terrestrial communication standard, for its lower peak-to-average power ratio (PAPR) and similar receiver complexity, compared with the standard OFDM. However, its applicati...

Equation In [1], (6) of the above named work is corrected.

An efficient adaptive turbo equalization (ATEQ) scheme is proposed for multiple-input–multiple-output underwater acoustic (UWA) communications. The proposed ATEQ scheme utilizes two layers of iterative processing: The inner-layer iteration is the soft-decision-based equalizer parameters adaptation and filtering of received signals in the equalizer,...

Compared with the soft-input, soft-output linear equalizer, the soft-input, soft-output decision-feedback equalizer (Soft-DFE) is much less investigated. This letter aims to provide a better understanding of the Soft-DFE, achieved via two comparisons: first, the two categories of designs classified by the way of treating the soft input and the soft...

The single-carrier frequency-division multiple access (SC-FDMA) or the discrete Fourier transform (DFT) pre-coded orthogonal frequency-division multiple access (OFDMA) technique has been adopted in the uplink transmission of the long term evolution (LTE) terrestrial communication standard, for its lower peak-to-average power ratio (PAPR) and simila...

Single-carrier frequency-domain turbo equalization (SC-FDTE) is investigated, with the focus on the design of soft-decision frequency-domain equalizer (SD-FDE) under minimum mean square error (MMSE) criteria. Existing SD-FDEs perform equalization on each frequency bin individually, which however only achieves suboptimal performance, and with the av...

The design of low-complexity soft-input soft-output (SISO) linear equalizer (LE) for turbo equalization can be classified into two categories: the Cat-I assuming random a priori soft input (from the decoder) and the Cat-II treating the a priori input deterministic. There is a lack of systematic comparison between the two categories. In this letter,...

A low-complexity turbo detection scheme is proposed for single-carrier multiple-input multiple-output (MIMO) underwater acoustic (UWA) communications using low-density parity-check (LDPC) channel coding. The low complexity of the proposed detection algorithm is achieved in two aspects: first, the frequency-domain equalization technique is adopted,...

An experimental investigation on turbo detection for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) underwater acoustic communications, is presented in this paper. In our detection scheme, the linear symbol estimation benefits from a hybrid soft interference cancelation and a reliability based detection orde...

A frequency-domain turbo equalization (FDTE) scheme without cyclic prefix (CP) or zero padding is proposed for single-carrier, multiple-input-multiple-output underwater acoustic communication. In the first iteration of the FDTE, the received continuous data stream is divided into consecutive blocks and a combined inter-block-interference (IBI) canc...

In this paper, an enhanced linear minimum mean square error (LMMSE) turbo equalization scheme is proposed for multiple-input multiple-output (MIMO) communication systems with bit-interleaved coded modulation (BICM) in the time domain and multiplexing in the space domain. The proposed turbo equalization scheme outperforms the conventional LMMSE turb...

This paper proposes a frequency-domain turbo detection scheme for single-carrier, multiple-input, multiple output (MIMO) underwater acoustic (UWA) transmission without using cyclic prefix (CP), aiming to achieve a low detection complexity and a high transmission efficiency simultaneously. The received data stream is divided into consecutive blocks,...

This paper proposes a reliability-based turbo detection scheme for multiple-input multiple-output (MIMO) systems with frequency-selective fading. The proposed scheme performs iterative successive soft interference cancellation (SSIC) with a block decision-feedback equalizer (BDFE). To minimize the negative impacts of error propagation in SSIC, we p...

The turbo detection of a coded under-determined multiple-input multiple-output (UD-MIMO) system is studied in this paper. A UD-MIMO system with N transmit antennas and M< Nreceive antennas has more unknowns than the observations. However, most existing low complexity detectors, such as the vertical Bell Laboratories Layered Space-Time (V- BLAST) or...

Multiple-input multiple-output (MIMO) underwater acoustic (UWA) channels introduce both space-time interference (STI) and time-varying phase distortion for transmitted signals. In such cases, the equalized symbols produced by conventional equalizer aiming for STI cancelation suffer phase rotation and thus cannot be reliably detected. In this paper,...

In this paper, a robust detection scheme is proposed for high data rate single-carrier multiple-input-multiple-output (MIMO) underwater acoustic communications. The new scheme adopts turbo block decision-feedback equalization, where the soft-decision equalizer performs successive soft interference cancellation of both the intersymbol interference i...

This paper proposes a frequency-domain detection scheme for single-carrier multiple-input, multiple-output (MIMO) underwater acoustic (UWA) communication using low-density parity-check (LDPC) codes. The new scheme employs turbo equalization technology together with iterative decoding technique, leading to a double-layer turbo detection structure. I...

The general property of noncommutativity of linear time-varying (LTV) systems has to be considered when a digital transmission system composed of LTV channel and transmit/receive filtering shall be represented in the equivalent discrete-time domain. In this correspondence, we analyze the implications of serially concatenated LTV systems with respec...

We propose an enhanced linear minimum mean square error (LMMSE) turbo equalization scheme for multiple-input multiple-output (MIMO) communication systems. The turbo equalizer employs soft interference cancellation (SIC), where tentative soft decisions of the interfering symbols are subtracted from the received samples before the LMMSE filtering. Th...

In this paper, an oversampled orthogonal frequency division multiplexing (OFDM) detector is proposed for multiple-input multiple-output (MIMO) underwater acoustic (UWA) communications. With simple time-domain oversampling and frequency-domain signal processing, the new oversampled OFDM (OOFDM) detector can achieve multipath diversity that is unavai...

This paper proposes a low-complexity turbo block decision feedback equalizer (BDFE) with reliability-based successive soft interference cancellation (SSIC) for multiple-input multiple-output (MIMO) systems. Turbo equalization in MIMO systems needs to combat both intersymbol interference (ISI) due to frequency-selective fading and multiplexing inter...

In this paper, we present a new Doppler spread estimation algorithm for broadband wireless orthogonal frequency division multiplexing (OFDM) systems with fast time-varying and frequency-selective Rayleigh or Rician fading channels. The new algorithm is developed by analyzing the statistical properties of the power of the received OFDM signal in th...

A new receiver design using iterative block decision-feedback equalizer (BDFE) is proposed for high data rate single-carrier multiple-input, multiple-output (MIMO) underwater acoustic (UWA) communications. The adoption of BDFE enables a sequence-based log-likelihood ratio (LLR) calculation during iterative equalization, thus leading to better perfo...

The joint estimation of carrier frequency offset (CFO) and channel transfer function (CTF) for orthogonal frequency-division multiplexing (OFDM) systems with phase noise is discussed in this paper. A CFO estimation algorithm is developed by exploring the time-frequency structure of specially designed training symbols, and it provides a very accurat...

In this paper, we propose a time-domain receiver design scheme for high data rate single carrier multiple-input, multiple-output (MIMO) underwater acoustic communications. In this scheme, each received packet is artificially partitioned into blocks for processing. The MIMO channel is initially estimated using training blocks at the front of transmi...

Channel estimation for orthogonal frequency division multiplexing (OFDM) system at the presence of carrier frequency offset (CFO) and phase noise is discussed in this paper. A CFO estimation algorithm is developed by exploiting the time-frequency structure of training symbols, and it provides a very accurate estimation of CFO at the presence of bot...

In this paper, we employ a time-domain channel estimation, equalization and phase correction scheme for single carrier single input multiple output (SIMO) underwater acoustic communications. In this scheme, Doppler shift, which is caused by relative motion between transducer (source) and hydrophones (receiver), is estimated and compensated in the r...

In this paper, we present a new Doppler spread estimation algorithm for broadband wireless orthogonal frequency division multiplexing (OFDM) systems with time-varying and frequency-selective Rayleigh fading. The algorithm is developed by analyzing the statistical properties of the power of received signals in the time domain, thus it excludes the i...

We propose a superimposed periodic pilot scheme for time-variant channel estimation of a multiinput and multioutput (MIMO) system. As a premise, the time-varying channel is assumed to follow a complex exponential basis expansion model. Estimation of such channel can be achieved only with a simple first-order statistics, and especially, mean-value u...

Mobile wireless links exhibit frequency selective fading , thus a receiver needs to perform channel estimation and equalization. In this paper, we propose a superimposed periodic pilot scheme for channel estimation of a multi-input and multi-output (MIMO) system with finite-impulse response (FIR). A simple first-order statistics is used, and any FI...