Hongwu Liu

Power Splitting-Based SWIPT With Decode-and-Forward Full-Duplex Relaying

This paper investigates simultaneous wireless information and power transfer (SWIPT) for a decode-and-forward (DF) full-duplex relay (FDR) network. A battery group consisting of two batteries is applied to utilize the relay-harvested energy for FDR transmission. The virtual harvest-use model and the harvest-use-store model are considered, respectively. By switching between two batteries for charging and discharging with the aid of power splitting (PS), concurrent source and relay transmissions can overcome spectral efficiency loss compared with half-duplex relay (HDR)-assisted PS-SWIPT. The outage probability for the virtual harvest-use model is presented in an exact integral form and the optimal PS (OPS) ratio that maximizes the end-to-end signal-to-interference-plus-noise ratio (e-SINR) is characterized in closed form via the cubic formula. The fundamental tradeoff between the e-SINR and recycled self-power is quantified. The OPS ratios and the corresponding outage probabilities in noise-limited and interference-limited environments are also derived. In the harvest-use-store model, a greedy switching (GS) policy is implemented with energy accumulation across transmission blocks. The OPS ratio of the GS policy is presented and the corresponding outage probability is derived by modeling the relays energy levels as a Markov chain with a two-stage state transition. Numerical results verify the performance improvement of the proposed scheme over HDR-assisted PS-SWIPT in terms of outage probability and average throughput.

A Reconfigurable Digital Receiver for Transmitted Reference Pulse Cluster UWB Communications

The transmitted reference pulse cluster (TRPC) structure for ultrawide bandwidth communications contains compactly spaced reference and data pulses and enables the use of a robust autocorrelation detector at the receiver. Since the digital receiver not only can avoid the problems caused by using the analog autocorrelation but can provide flexibility in its signal processing at the expense of high sampling rate of an analog-to-digital converter (ADC) as well, we consider the digital architecture for the recently proposed TRPC signaling scheme and propose a reconfigurable TRPC (rec-TRPC) receiver. The received signal-to-noise ratio (SNR) can be maximized in the new designed receiver by using the optimum number of delay line (DL) branches. The performance of the rec-TRPC receiver is analyzed, and our semi-analytical and simulation results show that the rec-TRPC receiver structure achieves up to a 2-dB power gain over the original TRPC receiver. Furthermore, the complexity of the rec-TRPC receiver is investigated from an implementation viewpoint and compared with the digital implementation of the original TRPC receiver.

Interference mitigation study for low energy critical infrastructure monitoring applications

Low energy critical infrastructure monitoring (LECIM) applications are rapidly increasing, whose common requirements derived from the type of communications performed include reliable data transfer, energy efficiency, long deployment lifetime, and low infrastructure cost. A low rate wireless personal area network (WPAN) can help control and manage the operations of such applications. To facilitate point to multi-points communication for LECIM devices, the IEEE 802.15.4k task group is formed as an amendment to IEEE 802.15.4. In this paper, we first review the main activities of TG15.4k with the updated status and the structure of LECIM networks. Then, after analyzing the interference issues in the LECIM system, especially for the direct-sequence spreading spectrum (DSSS) physical layer, we propose the interference mitigation schemes by combining time division multiplexing (TDM), frequency division multiplexing (FDM) and code division multiplexing (CDM). Furthermore, to mitigate the homogeneous interference more effectively, the orthogonal variable spreading factor (OVSF) codes based CDM are analyzed. Monte Carlo simulation results show that the proposed interference mitigation schemes has robustness against the interference under the LECIM multi cluster environments.

QoS-Constrained Relay Control for Full-Duplex Relaying With SWIPT

This study investigates relay control for simultaneous wireless information and power transfer in full-duplex relay networks under Nakagami-

Approximate BER analysis of opportunistic relaying incremental hybrid DAF cooperative system

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Priority-Based Cloud Computing Architecture for Multimedia-Enabled Heterogeneous Vehicular Users

fading channels. Unlike previous work, harvest-transmit (HT) and general harvest-transmit-store (HTS) models are respectively considered to maximize average throughput subject to quality of service (QoS) constraints. The end-to-end outage probability of the network in an HT model is presented in an exact integral-form. To prevent outage performance degradation in an HT model, time switching (TS) is designed to maximize average throughput subject to QoS constraints of minimizing outage probability and maintaining a target outage probability, respectively. The optimal TS factors subject to QoS constraints are presented for an HT model. In general, in an HTS model, energy scheduling is performed across different transmission blocks and TS is performed within each block. Compared with the block-based HTS model without TS, the proposed general HTS model can greatly improve outage performance via greedy search (GS). By modeling the relay’s energy levels as a Markov chain with a two-stage state transition, the outage probability for the GS implementation of the general HTS model is derived. To demonstrate the practical significance of QoS-constrained relay control, numerical results are presented showing that the proposed relay control achieves substantial improvement of outage performance and successful rate.

Massive MIMO Relay Systems with Multipair Wireless Information and Power Transfer

In this paper, we propose an opportunistic relaying incremental hybrid decode-amplify-forward (OR-IHDAF) scheme and present its approximate closed-form bit-error rate (BER) expression based on a Taylor series expansion method. Simulation results about the BER performance show the correctness of the theoretical analysis and the BER comparison of the OR-IHDAF with ISDF and IHDAF schemes is also provided to show the superiority of the OR-IHDAF scheme.

Precoding design for two-way MIMO relay networks based on CP-SC transmission

In recent days, vehicles have been equipped with smart devices that offer various multimedia-related applications and services, such as smart driving assistance, traffic congestions, weather forecasting, road safety alarms, and many entertainment and comfort applications. Thus, these smart vehicles produce a large amount of multimedia-related data that require fast and real-time processing. However, due to constrained computing and storage capacities, such huge amounts of multimedia-related data cannot be processed in on-board standalone devices. Thus, multimedia cloud computing (MCC) has emerged as an economical and scalable computing technology that can process multimedia-related data efficiently while providing improved Quality of Service (QoS) to vehicular users from anywhere, at any time and on any device, at reduced costs. However, there are certain challenges, such as fast service response time and resource cost optimization, that can severely affect the performance of the MCC. Therefore, to tackle these issues, in this paper, we propose a dynamic priority-based architecture for the MCC. In the proposed scheme, we divide multimedia processing into four different subphases, while computing resources to each computing server are assigned dynamically, according to the workload, in order to process multimedia tasks according to the multimedia user Quality of Experience (QoE) requirements. The performance of the proposed scheme is evaluated in terms of service response time and resource cost optimization using the CloudSim simulator.

Resource allocation for cyclic prefixed single-carrier cognitive two-way relay networks

This paper investigates destination-aided simultaneous wireless information and power transfer (SWIPT) for a decode-and-forward relay network, in which massive multiple-input multiple-output antennas are deployed at relay to assist communications among multiple source-destination pairs. During relaying, energy signals are emitted from multiple destinations when multiple sources are sending their information signals to relay. With power splitting and unlimited antennas at relay, asymptotic expression of harvested energy is derived. The analysis reveals that asymptotic harvested energy is independent of fast fading effect of wireless channels; meanwhile transmission powers of each source and destination can be scaled down inversely proportional to the number of relay antennas. To significantly reduce energy leakage interference and multipair interference, zero-forcing processing and maximum-ratio combing/maximum-ratio transmission are employed at relay. Fundamental trade-off between harvested energy and achievable sum rate is quantified. It is shown that asymptotic sum rate is neither convex nor concave with respect to power splitting and destination transmission power. Thus, a one-dimensional embedded bisection algorithm is proposed to jointly determine the optimal power splitting and destination transmission power. It shows that destination-aided SWIPT are beneficial for harvesting energy and increasing sum rate. The significant sum rate improvements of the proposed schemes are verified by numerical results.

Two-way CP-SC relay networks with distributed space-frequency linear dispersion coding

This paper proposes a new source and relay precoding design in a two-way MIMO relay network based on cyclic prefixed single carrier (CP-SC) transmission. The source precoding, relay precoding, and decision feedback equalization with noise-prediction (DFE-NP) receivers are jointly designed to minimize the sum-mean squared error (MSE) of the network. An iterative algorithm is proposed to optimize the source and relay precoding matrices. It has been proved that in a two-way MIMO relay network with frequency-selective channels, the optimal relay precoding is a frequency-domain beamforming with a diagonal power allocation matrix, which is the transmit power across multiple beamforming directions. In order to reduce the computational complexity, a projected gradient algorithm of the diagonal matrix form is also applied in determining the power allocation matrix.