Loop Interference Research Articles

On energy conservation for fixed-wing UAV assisted practical full-duplex relaying with service requirement and bank angle limit

This paper studies a full-duplex (FD) amplify-and-forward relaying, where a fixed-wing unmanned aerial vehicle (UAV) is dispatched as a mobile relay to serve a source-destination communication pair so as to satisfy their service requirement. Here, the UAV relay flies in a circular path and hence it must continuously change its heading of flight which leads to a bank angle of the aircraft. In order to ensure flight safety, therefore, a bank angle limit is imposed on the UAV relay. By considering a practical FD relaying, namely, there exists both residual loop interference (RLI) and processing time-delay at the relay side, novel signal to interference plus noise ratio (SINR) received at the destination is analyzed, giving a closed-form expression in addition to a concise lower-bound. Armed with the SINR analysis, the size of data received by the destination during a period of flight time of the UAV is calculated, leading to a closed-form lower-bound of the size of data. Taking bank angle limit into consideration and using the calculated lower-bound of the size of data, an optimization problem with the purpose of energy conservation is solved, leading to a novel method for joint adjustment of the UAV's flight parameters. Computer simulation experiments are conducted, and the results demonstrated that the proposed optimization method performs better in terms of energy conservation compared to the benchmark techniques regardless of the value of RLI and/or the service requirement of the source-destination communication pair.

Joint Beamforming and Phase Shifts Design for RIS-Aided Multi-User Full-Duplex Systems in Smart Cities.

Full-duplex (FD) and reconfigurable intelligent surface (RIS) are potential technologies for achieving wireless communication effectively. Therefore, in theory, the RIS-aided FD system is supposed to enhance spectral efficiency significantly for the ubiquitous Internet of Things devices in smart cities. However, this technology additionally induces the loop-interference (LI) of RIS on the residual self-interference (SI) of the FD base station, especially in complicated urban outdoor environments, which will somewhat counterbalance the performance benefit. Inspired by this, we first establish an objective and constraints considering the residual SI and LI in two typical urban outdoor scenarios. Then, we decompose the original problem into two subproblems according to the variable types and jointly design the beamforming matrices and phase shifts vector methods. Specifically, we propose a successive convex approximation algorithm and a soft actor-critic deep reinforcement learning-related scheme to solve the subproblems alternately. To prove the effectiveness of our proposal, we introduce benchmarks of RIS phase shifts design for comparison. The simulation results show that the performance of the low-complexity proposed algorithm is only slightly lower than the exhaustive search method and outperforms the fixed-point iteration scheme. Moreover, the proposal in scenario two is more outstanding, demonstrating the application predominance in urban outdoor environments.

BER analysis of a full-duplex relay-assisted BPSK-SIM based VLC system for indoor applications.

This paper contemplates a relay-assisted visible light communication (VLC) system, where the light source (table lamp) acts as a relay node and cooperates with the main light source. Following the IEEE 802.15.7r1 VLC reference channel model, we assume that there are two different light sources present in an office room. The first one is the source terminal present on the ceiling and another one is the desk lamp that serves as the relay station, which works in a full-duplex method. Because of the loop interference channel, we model the VLC relay terminal using ray tracing simulations. We have analyzed the bit error rate (BER) performance of the relay-assisted VLC system using a binary phase shift keying-subcarrier intensity modulation (BPSK-SIM) technique. The proposed method outperforms existing phase shift keying (PSK) and square M-quadrature amplitude modulation (M-QAM) techniques. The proposed VLC system using the BPSK-SIM technique achieves a BER performance of 10-12 for an SNR of 20dB. The results of the proposed full-duplex and half-duplex relayed VLC systems are evaluated using equal power allocation (EPA) and optimum power allocation (OPA) techniques over three different modulation schemes, which are 2-PSK, square M-QAM, and BPSK-SIM.

Performance analysis on the low-power energy harvesting wireless sensor networks with a novel relay selection scheme

Simultaneous wireless information and power transfer (SWIPT) has been utilized widely in wireless sensor networks (WSNs) to design systems that can sustain themselves by harvesting energy from the surrounding areas. In this study, we investigated the performance of the so-called low-power energy harvesting (LPEH) WSN. Being different from other studies, we equipped each relay with a battery whose characteristics were described by an on/off (1/0) decision scheme as per the Markov property. In this context, an optimal loop interference relay selection (OPLIRS) was proposed and investigated. Moreover, the crucial role of the log-normal distribution method in characterizing the LPEH WSN’s constraints was proven and emphasized. The system performance was evaluated in terms of the overall ergodic outage probability (OP) both analytically and numerically with Monte Carlo simulation. Readers can refer to this paper for guidelines on defining the networks’ constraints, analytically derivating the problems, or use the presented results for possible comparison studies.

Ergodic Rate and Outage Performance of Full-Duplex NOMA Relaying with Channel Estimation Errors and Low-Resolution ADCs

In this paper, we analyze the performance of a full-duplex (FD) cooperative non-orthogonal multiple access (C-NOMA) relaying system with an amplify-and-forward (AF) protocol in the presence of loopback interference in FD transceivers. Particularly, by considering channel estimation errors and quantization noise in low-resolution analog-to-digital converters (ADCs), the accurate approximation expression for the ergodic rate and closed-form solution for the outage probability are derived, respectively. The validity of the theoretical results is verified by Monte Carlo simulations, which show that both channel estimation errors and quantization noise have deleterious effects on ergodic rate and outage performance for moderate and high signal-to-noise ratios (SNR). In the second phase of the C-NOMA system, both the outage performance and ergodic sum rate decrease at high SNRs due to the effects of loop interference. When the ADC dynamic range reaches a certain level, the system performance is more affected by loopback interference and channel estimation errors compared to the quantization noise of the ADCs.

Combining FD‐UAV and NOMA technologies in IoT sensor network with millimeter‐wave communications

SummaryIn this article, we exploit the huge advantages of full‐duplex (FD) transmission, nonorthogonal multiple access (NOMA) technique, unmanned aerial vehicle (UAV), and millimeter‐wave (mmWave) communications in an Internet of things (IoT) sensor network. Specifically, the UAV operates as a FD amplify‐and‐forward (AF) relay to aid communications between an IoT sensor and multiple NOMA users. Moreover, the FD‐UAV (FDU) adopts both fixed and variable gains. We obtain exact expressions of outage probability (OP) and throughput of IoT‐FDU‐NOMA‐mmWave network with fixed and variable gains at FDU over Nakagami‐ fading channels. Numerical illustrations clearly show that the OP and throughput performance of the IoT‐FDU‐NOMA‐mmWave network with variable gain are considerably higher than those with fixed gain. Since mmWave bands are used, the OP and throughput of the IoT‐FDU‐NOMA‐mmWave network are greatly affected by carrier frequency and communication distances. Consequently, when the carrier frequency or/and the distances between the IoT sensor and the users increase, the transmit power of the IoT sensor and the FDU should be increased to maintain the network performance. On the other hand, the effects of residual loop interference (LI) induced by FD transmission are remarkable. Thus, more efforts to reduce the residual LI power have to be continuously performed. Moreover, the specific impacts of the key parameters such as fading order , the positions of the FDU, and data rates are clarified. More importantly, in practice, according to the fixed gain or the variable gain that is used, we can locate the position of FDU to achieve the best performance for the IoT‐FDU‐NOMA‐mmWave network.

Paper] Study on Single Frequency Downlink with Coupling Loop Interference Canceller for Professional SC-FDE Wireless Camera using Millimeter-wave Band

Professional wireless cameras using the millimeter-wave band can transmit more information than those in the UHF band, making this band especially useful for transmitting high-quality video and audio with low latency. Although such devices have been put into practical use, there is a need to downsize the equipment on the camera side to reduce expensive millimeter-wave band components and improve operability. In this study, we configure the downlink of a professional wireless camera for UHDTV as a single frequency network (SFN) and study the expansion of coverage provided by a booster. A coupling loop interference canceller and multi-path equalizer are installed in the booster. A computer simulation shows that the booster works well. SFN interference, in which the master and booster waves multiply propagate, can be equalized through frequency domain equalization (FDE) of the single-carrier (SC) system at the receiver side.

Multi-antenna relay assisted NOMA network with multiple imperfect factors

In this paper, a 5G downlink multi-antenna relay assisted non-orthogonal multiple access (NOMA) communication system is investigated. The relay can work in half-duplex (HD) or full-duplex (FD) mode with maximum-ratio-combining/transmission antenna selection (MRC/TAS) scheme, and the direct links between the source and destinations are also considered. The exact expressions for the outage probability are derived when considering the effects of hardware impairment (HDI), imperfect successive interference cancellation (ipSIC), channel estimation error(CEE), antenna number and loop-interference (LI) for FD mode. Then, based on the accurate outage probability, the approximate low bound and asymptotic results are derived. From the derived formulas, we find that the maximum diversity order of the considered system is min{(1−μ)N+1,M+1} when CEE does not appear, where μ is the LI cancellation grade, N and M are the receiving and transmitting antenna number equipped at the relay. Otherwise the diversity decreases to one or zero regardless of multi-antenna when CEE appears, but multiple antennas still improve system performance by promoting the array gain. The FD mode may outperform the HD mode with less LI which is decided by μ. Monte Carlo simulations are also done to validate the correctness of theoretical analysis.

Performance Analysis of IRS-Assisted Full-Duplex Wireless Communication Systems With Interference

This letter considers a full-duplex wireless communication system, where two users communicate to each other through an intelligent reflecting surface (IRS). Each user is assumed to be equipped with two antennas, one each for reception and transmission. The system suffers from loop-interference (LI) between the transmit and receive antennas, self-interference (SI) through the IRS, and external interferers (EI) available at the IRS and users. The fading channels are modelled by Weibull distribution as it is a generalized and accurate model for both indoor and outdoor communications. By taking into account the IRS random reflection coefficient (RRC), and by applying the Laguerre expansion approximation, we derive closed-form expressions for outage probability and ergodic capacity. Numerical and simulation results show that LI, SI, EI and RRC have sever impacts on the system performance. The results also show the robustness of the Laguerre expansion approximation compared to non-central Chi-squared distribution, in particular, for a small number of IRS elements.

In vivo dissection of a clustered-CTCF domain boundary reveals developmental principles of regulatory insulation

Vertebrate genomes organize into topologically associating domains, delimited by boundaries that insulate regulatory elements from nontarget genes. However, how boundary function is established is not well understood. Here, we combine genome-wide analyses and transgenic mouse assays to dissect the regulatory logic of clustered-CCCTC-binding factor (CTCF) boundaries in vivo, interrogating their function at multiple levels: chromatin interactions, transcription and phenotypes. Individual CTCF binding site (CBS) deletions revealed that the characteristics of specific sites can outweigh other factors such as CBS number and orientation. Combined deletions demonstrated that CBSs cooperate redundantly and provide boundary robustness. We show that divergent CBS signatures are not strictly required for effective insulation and that chromatin loops formed by nonconvergently oriented sites could be mediated by a loop interference mechanism. Further, we observe that insulation strength constitutes a quantitative modulator of gene expression and phenotypes. Our results highlight the modular nature of boundaries and their control over developmental processes.

Performance Analysis on Low-Power Energy Harvesting Wireless Sensors Eco-Friendly Networks with a Novel Relay Selection Scheme

Simultaneous wireless information and power transfer (SWIPT) has been utilized widely in wireless sensor networks (WSNs) to design systems that can be sustained by harvesting energy from the surrounding areas. In this study, we investigated the performance of the low-power energy harvesting (LPEH) WSN. We equipped each relay with a battery that consisted of an on/off (1/0) decision scheme according to the Markov property. In this context, an optimal loop interference relay selection was proposed and investigated. Moreover, the crucial role of the log-normal distribution method in characterizing the LPEH WSN’s constraints was proven and emphasized. System performance was evaluated in terms of the overall ergodic outage probability (OP) both analytically and numerically with Monte Carlo simulation. The system had the lowest overall ergodic OP, thus, performed the best with an energy harvesting time switch of 0.175. Following the increase in the signal-to-noise ratio (SNR), the system without a direct link performed the worst. Furthermore, as more relays were deployed, the better the system performed. Finally, results showed that more than 80% of the data rates can be obtained under the household condition, without the need for extra bandwidth and power supply.

Bandit-Based Power Control in Full-Duplex Cooperative Relay Networks With Strict-Sense Stationary and Non-Stationary Wireless Communication Channels

Full-duplex relaying is an enabling technique of sixth generation (6G) mobile networks, promising tremendous rate and spectral efficiency gains. In order to improve the performance of full-duplex communications, power control is a viable way of avoiding excessive loop interference at the relay. Unfortunately, power control requires channel state information of source-relay, relay-destination and loop interference channels, thus resulting in increased overheads. Aiming to offer a low-complexity alternative for power control in such networks, we adopt reward-based learning in the sense of multi-armed bandits. More specifically, we present bandit-based power control, relying on acknowledgements/negative-acknowledgements observations by the relay. Our distributed algorithms avoid channel state information acquisition and exchange, and can alleviate the impact of outdated channel state information. Two cases are examined regarding the channel statistics of the wireless network, namely, strict-sense stationary and non-stationary channels. For the latter, a sliding window approach is adopted to further improve the performance. Performance evaluation highlights a performance-complexity trade-off, compared to optimal power control with full channel knowledge and significant gains over cases considering channel estimation and feedback overheads, outdated channel knowledge, no power control and random power level selection. Finally, it is shown that the sliding-window bandit-based algorithm provides improved performance in non-stationary settings by efficiently adapting to abrupt changes of the wireless channels.

Development of Coupling loop Interference Canceller for FM Single Frequency Network

Development of Coupling loop Interference Canceller for FM Single Frequency Network

Optimization for Signal Transmission and Reception in a Macrocell of Heterogeneous Uplinks and Downlinks

Internet-of-things (IoT) applications continue to drive advancements in serving as many heterogeneous low-latency downlinks and uplinks as possible within a constrained communication bandwidth. Full-duplexing (FD) transceivers have been introduced to implement simultaneous signal transmission and reception (STR) over the entire available frequency band. However, both inter-link interference and FD loop-interference are hardly suppressed to a necessary level for the effectiveness of FD-based STR even for microcells. This paper proposes an alternative STR technique per one time-slot for macrocells, where a fraction of a time-slot is used for downlinks and the remaining complementary fraction of the time-slot is used for uplinks. Thus, STR over the entire available bandwidth can be implemented in a way with no loop interference. Furthermore, another approach of using a fraction of the available bandwidth for downlinks and the remaining complementary fraction of the bandwidth for uplinks over the whole time-slot is also proposed. The problem of both downlink and uplink beamforming to maximize the energy efficiency of such heterogeneous networks subject to the quality-of-service in terms of downlink and uplink throughput is examined for all three possible STRs. Numerical results demonstrate the advantages of the time-fraction-wise STR and bandwidth-fraction-wise STR over the FD-based STR, where the time-fraction-wise STR is not only the best in serving the same numbers of downlinks and uplinks but also is capable of serving many more downlinks and uplinks with a higher energy efficiency.

Performance Analysis of Full-Duplex Massive MIMO Systems With Low-Resolution ADCs/DACs Over Rician Fading Channels

This paper analyzes the performance of multi-user full-duplex (FD) massive multiple-input multiple-output (MIMO) systems with low resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) under Rician fading channels. The maximum ratio combining and maximum ratio transmission are used at the base station (BS) for the uplink and downlink, respectively. By leveraging on the additive quantization noise model, tight closed-form approximations of the uplink and downlink achievable rates are obtained for both perfect and imperfect channel state information cases. The results show the impact of the Rician $K$ -factor, ADC/DAC resolution, loop interference, and inter-user interference of the systems. In addition, we adopt the power scaling law to show that to achieve a fixed level of the signal-to-interference-plus-noise ratio, the transmit power of each user and the BS can be scaled down proportionally to the inverse of the BS antenna number. Moreover, we compare the performance of the FD mode and the half-duplex mode, and study the trade-off between the achievable rate and BS energy efficiency. Numerical results show that the use of low-resolution ADCs/DACs can significantly improve the BS energy efficiency with only small reduction in the achievable rate of the FD system.

Precoding for multiuser MIMO full-duplex amplify-and-forward relay uplink communication systems

This paper examines the precoding matrix design for a multiuser multiple-input multiple-output full-duplex (FD) relay uplink communication system with an amplify-and-forward relay. The main problem in FD systems is the loop interference (LI) cancellation, and perfect LI cancellation is not possible so residual LI exists. Linear precoders are used at the sources and relay, and a minimum mean-squared-error receiver is employed at the destination to reduce the influence of the residual LI. An iterative method is developed to solve the highly nonconvex joint source, relay, and receiver optimization problem. Simulation results are presented which show that the proposed iterative optimization algorithm provides better performance than existing half duplex systems in terms of the achievable rate even with residual LI.

Asymptotic Analysis of Full-Duplex Large-Scale MIMO Systems With Low-Resolution ADCs/DACs Over Rician Fading Channels

In this article, the uplink rate and downlink achievable rates of full-duplex (FD) large-scale multiple-input–multiple-output (MIMO) systems with low-resolution analog-to-digital converters/digital-to-analog converters (ADCs/DACs) over the Rician fading channels are investigated. By utilizing the maximum ratio combining/maximum ratio transmission processing, the approximate achievable rates of uplink and downlink with imperfect channel state information environments are presented. Then, the effects of the loop interference (LI), quantization error, and interuser interference (IUI) are evaluated based on the derived rates. According to the derived results, we find that interference and noise can be wiped out by using proper power scaling law, more antennas and bigger Rician factor. The numerical results show that deploying more base station antennas can effectively eliminate the LI, IUI, and noise caused by the FD mode. We also find that the approximate achievable rates of uplink and downlink will converge to a constant as the number of quantized bits tends to infinity. Moreover, performance of an FD large-scale MIMO system is found in close relationship with the quantization bits number, which, however, is insignificant when the ADCs/DACs quantization bits are increased. Thus, the use of low-resolution ADCs/DACs is verified sufficient in a large-scale MIMO system.

Performance Evaluation of a Full-Duplex Relaying-Enabled Satellite Sensor Network.

This paper investigates the performance of a full-duplex (FD) relaying-enabled satellite sensor network under residual loop interference, where the satellite uplink and the downlink transmissions simultaneously occur over the same frequency band. Specifically, the closed-form expressions for the outage probability and ergodic capacity of the FD relaying satellite sensor network are derived by considering residual loop interference, channel statistical property, propagation loss, geometric satellite antenna pattern, and terminal elevation angle. Simulation results show the achieved performance gains of a full-duplex relaying satellite sensor network over traditional half-duplex relaying, and highlight the impact of key system parameters on the performance of the considered FD relaying satellite sensor network.

Power Allocation for Self-Coded Distributed Space-Time Codes in FD Two-Way Relaying Networks

In this paper, a power allocation space-time coding scheme based on the self-coding property of residual loop interference (RLI) for two-way full-duplex (FD) amplify-and-forward (AF) relaying networks is proposed. The relay and direct link cooperate to forward the received signals to destination node, forming the self-coded distributed space-time code, in which the relay performs self-coding using the RLI after implementing some self-interference cancellation techniques. Then, an iterative power allocation algorithm is presented. With the proposed power allocation algorithm, both amplifying factor and transmit powers of terminal nodes are jointly optimized to maximize the smaller signal-to-interference-plus-noise ratio (SINR) of terminal nodes under a total power constraint when estimated instantaneous channel state information is available. We theoretically demonstrate the benefits of the proposed power allocation algorithm compared to equal power allocation. Simulation results show that the proposed scheme achieves significant improvement in performance compared with existing schemes for FD relaying systems and half-duplex relaying systems.

Leakage rate–based untrustworthy relay selection

AbstractThis paper investigates the leakage rate based untrustworthy relay selection strategies, which are based on the untrustworthy relay terminals operate in half‐duplex, full‐duplex, and hybrid modes. The investigation considers a dual‐hop one/two‐way half/full‐duplex wireless relaying network in the system model. The investigation also considers that a finite number of friendly jammers affect the untrustworthy relay terminals. According to analytical, asymptotic, and Monte Carlo simulation results, the LR‐based untrustworthy relay selection strategies achieve cooperative diversity order in high‐signal‐to‐noise ratio. However, friendly jammers and loop interference severely affect the system performance and degrade the achievable diversity order from M to 0 and also cause system coding gain losses. In addition, friendly jammers and loop interference also degrade the system achievable rate performance and cause saturation in high SNRs.