Sicong Liu

Narrowband Interference Cancelation Based on Priori Aided Compressive Sensing for DTMB Systems

In this paper, a novel narrowband interference (NBI) cancelation scheme based on priori aided compressive sensing (CS) for digital terrestrial multimedia broadcasting systems is proposed. The repeated training sequences in the transmitted symbols are exploited by differential measuring to acquire the CS measuring vector of the NBI, and for joint acquisition of the NBI support priori. Using the proposed priori aided sparsity adaptive matching pursuit algorithm, the sparse high-dimensional NBI can be accurately reconstructed from the measuring vector of much smaller size obtained through the proposed CS-based differential measuring method. It is verified by theoretical analysis and simulations that the proposed method outperforms conventional anti-NBI methods under multipath broadcasting channels.

Double Kill: Compressive-Sensing-Based Narrow-Band Interference and Impulsive Noise Mitigation for Vehicular Communications

Narrow-band interference (NBI) and impulsive noise (IN) are two kinds of non-Gaussian noise that have a severe impact on vehicular communications. In this paper, a novel compressive sensing (CS)-based method of simultaneous NBI and IN mitigation is proposed, which is a double kill of the two kinds of unfavorable disturbances. A CS-based time-frequency-measuring orthogonal frequency-division multiplexing (CS-TFM-OFDM) frame structure is introduced, in which the temporal repeated training sequences (TSs) are exploited by the proposed CS-based differential measuring (CS-DM) method to acquire the CS measurement vector of the NBI. With the aid of the a priori partial support, we further proposed the a priori-aided sparsity adaptive matching pursuit (PA-SAMP) to improve the accuracy and stability of NBI recovery. Meanwhile, the measurement vector of the IN is acquired from the null subcarriers in the CS-TFM-OFDM frame. After partial support of the IN is obtained, the IN is reconstructed using the proposed PA-SAMP algorithm. Hence, the two categories of non-Gaussian noise are both thoroughly eliminated, leading to the stability and robustness of vehicular communications. The proposed CS-based approach outperforms the conventional noise suppression methods in vehicular communications environments, which is validated by theoretical analysis and computer simulations.

Novel Visible Light Communication Approach Based on Hybrid OOK and ACO-OFDM

In this letter, we present a novel hybrid intensity modulation and direct detection communication system, which integrates asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and on-off keying (OOK) modulation schemes. First, the negative ACO-OFDM is proposed based on the conventional ACO-OFDM system to accommodate the on case with direct current in the OOK modulation, while the ACO-OFDM can match the off case in the OOK modulation. Therefore, the novel hybrid system combines the ACO-OFDM and OOK modulation schemes, while the signals can be recovered at the receiver to support the different qualities of service with high spectral efficiency and can be adapted to various receivers with different complexities. Simulation results are reported for the visible light channel and show that both the ACO-OFDM and OOK signals can be well recovered.

An Optimal Interleaving Scheme With Maximum Time-Frequency Diversity for PLC Systems

In this paper, an optimal interleaving scheme with maximum time-frequency diversity is proposed to combat against the narrowband interference (NBI) and time-domain impulsive noise for orthogonal frequency-division multiplexing (OFDM) systems in power-line communications (PLC). To improve the anti-NBI and anti-TIN performance, we propose two criteria based on which the optimized interleaving scheme is designed: 1) to increase the number of different OFDM blocks for one forward error correction (FEC) codeword, which is aimed at TIN mitigation and 2) to increase the number of different subcarriers mapped to the data symbols in one FEC codeword, which is aimed at NBI mitigation. Simulations show that the proposed interleaving scheme can effectively reduce the impairments caused by NBI and/or TIN in OFDM systems under PLC environments and, hence, achieve better performance than the conventional block interleaving scheme.

Nonorthogonal Time–Frequency Training-Sequence-Based CSI Acquisition for MIMO Systems

In this paper, a spectrally efficient nonorthogonal time-frequency training sequence (TS)-based channel state information (CSI) acquisition approach is proposed for multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems under the framework of structured compressed sensing (SCS). The scheme first relies on a time-domain TS that is identical for all transmit antennas to acquire the partial channel common support by utilizing the spatial correlation property of the MIMO channels and then uses the frequency-domain TS for accurate CSI recovery based on the proposed adaptive spatially-temporally joint simultaneous orthogonal matching pursuit algorithm. Here, the obtained partial channel common support can be utilized to reduce the complexity of the classical SCS algorithm and improve the signal recovery probability. Simulation results show that the proposed scheme could significantly reduce the TS overhead and demonstrate better performance than the existing MIMO-OFDM systems, which might be suitable for massive MIMO systems in future fifth-generation communications.

Priori Aided Compressed Sensing-Based Clipping Noise Cancellation for ACO-OFDM Systems

In this letter, the clipping noise is reconstructed from the selected reliable observations in the frequency domain based on the modified compressed sensing (CS) algorithm for the asymmetrically clipped optical orthogonal frequency division multiplexing modulated visible light communication system. With the aid of the priori information obtained from the received time-domain signals, the proposed priori aided sparsity adaptive matching pursuit method improves the accuracy and robustness of the recovery performance. Simulation results show that the proposed scheme outperforms conventional CS-based clipping noise cancellation counterparts.

OFDM preamble design for synchronization under narrowband interference

In this paper, an OFDM-based preamble is proposed for improving timing and frequency synchronization in the power line channel with narrowband interference (NBI) as well as transmitting several bits of transmission parameter signaling (TPS). In the time domain, an additional scrambling operation is applied to the cyclic extension of an OFDM training symbol to reduce the impact of NBI. Compared to the conventional Schmidls and Minns methods, the proposed preamble could provide even sharper correlation peak and achieve better timing detection in both AWGN and power line multipath channels under NBI, with a moderate complexity increase because more correlation and multiplication operations are required. Furthermore, the proposed preamble could also convey several bits of TPS via the variable distance of two training sequences allocated in the frequency domain. Better synchronization results can be achieved through analyses and simulations with the proposed method.

Two-Dimensional Structured-Compressed-Sensing-Based NBI Cancelation Exploiting Spatial and Temporal Correlations in MIMO Systems

Narrowband interference (NBI) caused by narrowband licensed or unlicensed services is a major concern that constrains the performance of multiple-input multiple-output (MIMO) systems. In this paper, the new and powerful signal processing theory of structured compressed sensing (SCS) is introduced to solve this problem. Exploiting the 2-D spatial and temporal correlations of NBI in MIMO systems, a novel NBI recovery method, i.e., the spatial multiple differential measuring method, is proposed in the framework of 2-D SCS. At each receive antenna, a differential measurement vector is acquired from the repeated training sequences in the IEEE 802.11 series preamble. Then, multiple measurement vectors from all receive antennas are utilized to recover and cancel NBI using the proposed SCS greedy algorithm of structured sparsity adaptive matching pursuit. Simulation results indicate that the proposed scheme outperforms the conventional schemes over the wireless MIMO channel.

Clipping Noise Elimination for OFDM Systems by Compressed Sensing With Partially Aware Support

The clipping noise, which could cause out-of-band radiation and increase bit error rate in orthogonal frequency division multiplexing systems, is necessary to be mitigated. This paper proposes a clipping noise elimination scheme based on compressed sensing (CS) with partially aware support. Specifically, the clipping noise is reconstructed from the selected reliable observations in the frequency domain with the proposed partially aware support sparsity adaptive matching pursuit algorithm. The proposed method outperforms the conventional clipping noise elimination approaches in the aspects of both the accuracy and robustness by exploiting the partially aware support, which is verified by both theoretical analysis and numerical simulation.

Structured compressive sensing-based non-orthogonal time-domain training channel state information acquisition for multiple input multiple output systems

In practical multiple input multiple output (MIMO) systems, accurate knowledge of the channel state information (CSI) is a prerequisite to guarantee the system performance. The conventional CSI acquisition methods for MIMO system usually rely on the orthogonal (either time- or frequency-domain) training sequences (TSs) to estimate the channel associated with each transmit–receive antenna pair, which is not spectrally efficient. This study proposes a non-orthogonal time-domain training-based CSI acquisition approach for MIMO systems under the framework of structured compressive sensing. By exploiting the spatial–temporal correlations of the sparse MIMO channels, a spatially–temporally spARsity-adaptivE-simultaneous orthogonal matching pursuit algorithm is proposed, which could use the inter-block interference free region of very small dimension within the received TS to recover the multiple channels. Furthermore, the proposed algorithm could utilise the priori channel partial common support to improve the recovery probability and reduce the complexity. Simulation results show that the proposed scheme has better performance and higher spectral efficiency than the conventional MIMO schemes, which might be an appealing solution for the future wireless communications.