Full-duplex Communication Research Articles

Neural Network Aided Digital Self-Interference Cancellation for Full-Duplex Communication Over Time-Varying Channels

In-band full duplex communication requires precise self-interference cancellation (SIC) to successfully decode the received desired signal. The existing neural network (NN) based SIC scheme uses offline trained NN to estimate the non-linear component of received self-interference (SI) over a static SI channel without additional NN training. For the time-varying SI channel, the NN-aided SIC method needs to retrain the NN during in-band full duplex communication to adapt time-varying channels. However, NN training is not fast enough to be done during full duplex communication. Thus, the SIC performance degrades. In this paper, we propose a digital SIC scheme using channel robust NN which takes estimates of linear SI channel coefficients as an input. It was found that the NN could learn the static part of the non-linear behavior of the SI channel well. Our solution can adapt the time-varying SI channel with only the channel coefficient estimation of linear components and a pre-trained NN. The proposed scheme can successfully reduce the SI to the noise floor for both time-invariant and time-varying SI channels.

Universal Performance Bounds for Joint Self-Interference Cancellation and Data Detection in Full-Duplex Communications

This paper studies the joint digital self-interference (SI) cancellation and data detection in an orthogonal-frequency-division-multiplexing (OFDM) full-duplex (FD) system, considering the effect of phase noise introduced by the oscillators at both the local transmitter and receiver. In particular, an universal iterative two-stage joint SI cancellation and data detection framework is considered and its performance bound independent of any specific estimation and detection methods is derived. First, the channel and phase noise estimation mean square error (MSE) lower bounds in each iteration are derived by analyzing the Fisher information of the received signal. Then, by substituting the derived MSE lower bound into the SINR expression, which is related to the channel and phase noise estimation MSE, the SINR upper bound in each iteration is computed. Finally, by exploiting the SINR upper bound and the transition information of the detection errors between two adjacent iterations, the universal bit error rate (BER) lower bound for data detection is derived.

Integrated Resource Allocation and Task Scheduling for Full-Duplex Mobile Edge Computing

Mobile edge computing (MEC) which enables communication, computation and storage capabilities at the network edge, is an emerging paradigm for 5G and beyond 5G networks. Resource-limited mobile devices can offload their tasks to the MEC server to reduce computation latency and save energy consumption. However, limited wireless spectrum resources make it hard for MEC to guarantee low latency when a large number of users offload the computation tasks or download the computed results. Full-duplex (FD) communication that allows simultaneous transmission and reception of signals over the same frequency band is a promising solution to the shortage of spectrum resources. In this paper, we study a multi-user FD-MEC system involving all the phases of uploading, computing, and downloading. With the help of an FD-capable base station (BS), two half-duplex (HD) users can form an FD pair and share the same time-frequency resource for task uploading and result downloading. We formulate a latency minimization problem considering power control, time scheduling, offloading decision, and user pairing strategy, which is a mixed-integer non-linear programming (MINLP) problem. The problem can be decomposed into two subproblems. The first subproblem is delay minimization for each possible FD pair, and the second one is to decide the offloading and user pairing strategy, and the user scheduling order. We analyze the problem in two cases: (1) the computing delay at the edge server is negligible and (2) the computing delay at the edge server is non-negligible. For both cases, the first subproblem is solved using a bisection algorithm. Then, we solve the second subproblem in the two cases by a relaxing-based algorithm and a concave-convex procedure (CCCP)-based algorithm, respectively. Finally, numerical results demonstrate that with our proposed strategies, the overall latency can be significantly reduced by integrating FD communication with the MEC system.

Joint In-Band Full-Duplex Communication and Radar Processing

In-band full-duplex (IBFD) technology has the potential to not only double the communication throughput but also enable additional capabilities. The fusion of radar and communication subsystems is an excellent example of how IBFD facilitates integration of radar functionality into a communication system. Developing and analysis of a joint IBFD radar-communication (RadCom) system is at the core of this article. This system derives the range-Doppler image from the state of an adaptive filter, which already exists in a typical IBFD transceiver. Our approach is waveform-independent and reuses the radio frequency (RF) front-end while it requires little additional digital logic. The proposed system is prototyped to assess the modem-radar coexistence in a real-world IBFD communication link budget. Employing the prototyped system, we quantify the additional required logic resources and investigate whether such a RadCom approach dictates a tradeoff between the two intended functionalities. The experimental results show that the proposed solution enables a communication system to detect targets within 20 m while maintaining an IBFD link with another communication node.

Simultaneous Wireless Power and Data Transfer System With Full-Duplex Mode Based on Double-Side LCCL and Dual-Notch Filter

The data transmission is always necessary for wireless power transfer systems, and however, the interference between power and data is the major problem for the full-duplex simultaneous wireless power and data transfer (SWPDT) system. To solve this problem, in this article, a novel SWPDT system based on the double-side <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCCL</i> and dual-notch filter is proposed. In the power transfer channel, by the double-side <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCCL</i> topology, the high impedance of power branches at the data carrier frequency reduces the power interference largely. In the data transfer channel, the dual-notch filter is utilized to separate the data carriers and realize the full-duplex communication, which could reduce the ipsilateral data interference and improve the signal-to-noise ratio (SNR). The transfer functions of data transmission are derived by the analysis on the impedance of each part. Since the interferences of power and ipsilateral data source are analyzed, the expression of SNR could be derived and the corresponding factors to improve the SNR are discussed. An optimization of data transfer channel to maximize the SNR is proposed by shifting the dual-notch filter and transformers. The experimental setup with 400-W output power and 200-kb/s data rate is conducted to verify the feasibility of the proposed SWPDT system and the correctness of the design method.

Partial and Full Relay Selection Algorithms for AF Multi-Relay Full-Duplex Networks With Self-Energy Recycling in Non-Identically Distributed Fading Channels

Full-duplex communication offers enhanced spectral efficiency for relay deployment, but suffers from the inherent self-interference from the strong transmit signal coupling to the sensitive receive chain. In this article, we propose a self-energy recycling (S-ER) protocol for full-duplex multi-relay networks, in which the energy from self-interference is harvested back at the relay for future use. Furthermore, two amplify-and-forward (AF) relay selection algorithms, namely, partial relay selection (PRS) and full relay selection (FRS) are introduced to enhance the reliability of the proposed systems. For PRS, the best relay is selected based on just the knowledge of the channels from the source to all relays, while in FRS, the best relay is selected based on the end-to-end signal-to-noise ratio, which requires knowledge of all source-relay and relay-destination links. We provide a thorough analysis on the outage performance and the spectrum efficiency of the proposed algorithms in both cases: all channel gains are independently but non-identically distributed (i.n.d.) (case 1) or independently, identically distributed (i.i.d.) (case 2) Rayleigh random variables. It is shown that SER and FRS can significantly enhance the performance of FD networks and avoid the outage floor when the number of relays increases, while the outage probability (OP) in PRS case reaches an outage floor. In addition, the end-to-end signal-to-noise ratio in both cases can be minimized if an optimal power-splitting factor is selected. All analytical results are verified by Monte Carlo simulation.

Capacity Performance for Full-Duplex Multihop Wireless Networks Using Channel Interference Balancing Allocation Scheme.

Full-duplex (FD) communication has been attractive as one of the research interests related to spectrum utilization for wireless networks from the previous evolution of communication systems. Previous studies discuss the realization of the FD system by focusing on self-interference cancellation and transmit power control in low-power wireless network scenarios. Today, capacity maximization is a key challenge in FD multihop wireless networks, in which the multi-channel allocation may lead to imbalance interference power due to the different number of simultaneous transmissions and its group selection that occurred on the same sub-channels. In this paper, we focus on the capacity maximization of the FD system by considering the influence of total interference power on each sub-channel and how to balance by selecting the different number of simultaneous transmissions to form a group that leads to a minimum difference in the total interference power on those sub-channels. Therefore, a channel interference balancing allocation (CIBA) scheme for balancing the total interference power in the multi-channel multihop wireless networks is proposed and further investigated by the idea of cooperative transmission. We also adopt the concept of interference distance to overcome the interference balancing problem of the proposed CIBA scheme. Performance evaluation results reveal that the proposed CIBA scheme achieves lesser total interference power and higher achievable capacity than other fixed channel allocation schemes.

Opportunistic Temporal Fair Mode Selection and User Scheduling in Full-Duplex Systems

In-band full-duplex (FD) communication has emerged as one of the promising techniques to improve data rates in next generation wireless systems. Typical FD scenarios considered in the literature assume FD base stations (BSs) and half-duplex (HD) users activated either in uplink (UL) or downlink (DL), where inter-user interference (IUI) is treated as noise at the DL user. This paper considers more general FD scenarios where an arbitrary fraction of the users are capable of FD and/or they can perform successive interference cancellation (SIC) to mitigate IUI. Consequently, one user can be activated in either UL or DL (HD-UL and HD-DL modes), or simultaneously in both directions requiring self-interference mitigation (SIM) at that user (FD-SIM mode). Furthermore, two users can be scheduled, one in UL and the other in DL (both operating in HD), where the DL user can treat IUI as noise (FD-IN mode) or perform SIC to mitigate IUI (FD-SIC mode). This paper studies opportunistic mode selection and user scheduling under long-term and short-term temporal fairness in single-carrier and multi-carrier (OFDM) FD systems, with the goal of maximizing system utility (e.g. sum-rate). First, the feasible region of temporal demands is characterized for both long-term and short-term fairness. Subsequently, optimal temporal fair schedulers as well as practical low-complexity online algorithms are devised. Simulation results demonstrate that using SIC to mitigate IUI as well as having FD capability at users can improve FD throughput gains significantly especially, when user distribution is concentrated around a few hotspots.

Covert Rate Optimization of Millimeter Wave Full-Duplex Communications

In this paper, we consider the problem of full-duplex covert millimeter wave (mmWave) communications, where a mmWave transmitter (Alice) sends information signals to its intended receiver (Bob) covertly in the presence of a watchful warden (Willie). For covering the presence of Alice, Bob operates in the full-duplex mode and generates jamming signals with a time-varying power. We investigate the covert rate optimization for both the single data stream case and the multiple data streams case under the constraints of the detection error probability at Willie. Specifically, for the single data stream case, we analytically characterize the minimum detection error probability at Willie and establish a framework for optimizing the analog beamforming, transmit power, and analog jamming jointly. As for the case of multiple data streams, we derive a tractable lower bound of the minimum detection error probability at Willie and formulate a joint optimization of the hybrid precoder and analog jamming design problem for the maximization of the achievable covert rate. Although the joint design problem is nonconvex, we adopt the penalty decomposition technique to handle the effect of the coupling between the analog precoder and digital precoder paving the way for the development of an iterative algorithm to locate its Karush-Kuhn-Tucker (KKT) solution. Finally, we show that our proposed joint design algorithm can be adapted to handle the multi-antenna Willie scenario and simulation results show that our proposed joint design algorithms can achieve significantly better performance as compared with some benchmark schemes.

PROTOTYPE APPLICATION OF CROWD DETECTION SYSTEM FOR TRADITIONAL MARKET VISITOR BASED ON IOT USING RFID MFRC522

Crowds of people are the government's concern in dealing with the COVID-19 pandemic because the virus transfers unwittingly from one person to another and transmits it to the closest environment. One of the locations where crowds are difficult to avoid is a traditional market and is thought to be one of the places that have the potential to become the center of the spread of COVID-19. Various efforts made by the government in suppressing crowds have yielded results, but not a few violations that occur are carried out intentionally or unintentionally, one of the efforts to prevent crowd violations is the traditional market visitor detection monitoring system by market management so that market visitors do not violate health protocols and crowds that occur in an area can be avoided. In this study, an IoT-based crowd detection system application prototype uses an RFID sensor MFRC522 as a crowd indicator based on data on the number of visitors entering a kiosk that is recorded in the database and then displayed on the application, this data becomes an indicator of which kiosk other visitors want to go to so that the crowd can be avoided. System functionality testing was carried out with 4 scenarios and system reliability testing through data transmission was carried out 10 times with test data in the form of kiosk id and visitor id sent via a single Transmission Control Protocol (TCP) with a full-duplex communication channel. The test results show that crowd indications can be detected in the application with data transmission speeds reaching 875 KB/s with an average delay of 231.4 ms and a standard deviation of 215 ± 313 ms.

IOT Based Energy Meter Reading System

Efficient use of energy plays an important role in the development of smart grid in power systems. Therefore, proper monitoring and control of energy consumption is a key step. The main priority is with smart grid. The existing energy meter system has many problems. One major problem is the lack of full duplex communication. To solve this problem, we propose a smart energy meter based on Internet of Things (lot). The proposed smart energy meter monitors and calculates power consumption using ESP 8266 12E, a Wi-Fi module and uploads it to the cloud, from where the consumer or manufacturer can view the readings. Hence, the energy analysis of the consumers become much easier and more controlled. This system also helps to detect power theft. So, this smart meter helps with home automation using IoT and enabling wireless connectivity, which is a big step towards the digital transformation of India

Cooperative Key Establishment Protocol for Full-Duplex Relay Systems

Using the fading channel characteristics, as a randomness source, for the secret key generation earns significant attention because of it’s computational less power and low energy consumption. Current researches focus on point-to-point reciprocal-based key extraction from these randomness sources. Most practical communication situations are non-line of sight, so endpoints use a relaying channel to improve communication performance. Besides that, in the upcoming 5G systems, the full-duplex (FD) communications will be one of the main techniques, which will remove the advantage of using the reciprocal feature in the randomness source common observation. In this paper, we consider the challenge of generating a symmetric secret key between two legitimate parties in the relaying channel with FD capability. We suggest an efficient key extraction protocol that accomplished an acceptable shared secret key rate compared to the direct channel traditional approach. Unlike similar schemes, we provide full statistical analysis for the construction of randomness source from the relaying channel with FD capability. Additionally, we investigate the performance analysis of the suggested key agreement protocol. We also analyze the effect of the curious-but-honest relay and an eavesdropper on the proposed protocol.

The Optimal Power Allocation for Sum Rate and Energy Efficiency of Full-Duplex Two-Way Communication Network.

Full-duplex (FD) transmission holds a great potential of improving the sum data rate of wireless communication systems. However, the self-interference introduced by the full-duplex transmitter brings a big challenge to enhance the energy efficiency. This paper investigates the power allocation problem in a full-duplex two-way (FDTW) communication network over an OFDM channel, aiming at improving the sum data rate and energy efficiency. We first characterize the sum rate and energy efficiency achieved in a single-carrier FDTW system. The optimal transmit power that achieves the maximal sum data rate is presented. The energy efficiency maximization problem is solved by using fractional programming. Then we further formulate sum rate and energy efficiency maximization problem in a multi-subcarrier FDTW system. In particular, the sub-optimal transmit power allocation which achieves a decent sum rate improvement is found by using a proposed iterative algorithm. By combining the iterative algorithm and fractional programming, we further maximize the energy efficiency of the multi-subcarrier system. With our proposed algorithm, we can easily obtain an optimal transmit power that approximates the global optimal solution. Simulation results show that using the obtained optimal transmit power allocation algorithm can significantly improve the sum rate and energy efficiency in both single-carrier and multi-subcarrier systems.

Design and analysis of IEEE 802.11 based Full Duplex WLAN MAC protocol

Full-Duplex (FD) communication is a promising technique that can be used in 5G to potentially double the system throughput compared to conventional Half Duplex (HD) transmission. Recent experiments have demonstrated near-perfect self-interference suppression techniques in the PHY layer to aid the possibility of FD communication. This paper presents a Synchronized Mode Full-Duplex (SM-FD) wireless LAN MAC protocol with appropriate modification of the IEEE 802.11 standard. The proposed SM-FD MAC protocol maintains synchronization between nodes and Access Point (AP) to increase efficiency. SM-FD MAC protocol supports WLAN having both FD and HD capable nodes by establishing both symmetrical links (Node1 ↔ AP) and asymmetrical links (Node1 → AP → Node2). To this end, we have utilized the packet-alignment-based capture effect in an efficient way. The proposed SM-FD MAC protocol has been analyzed using a Markov chain model. The analytical results for RTS and data collision probability, saturated throughput, delay, and energy spent per packet transmission have been derived and validated against simulation.

Lake experimentation of in-band full-duplex underwater acoustic communications

In-band full-duplex (IBFD) communications is a promising technique to achieve spectral-efficient communication in the underwater environment. Characteristics of self-interference and methods to suppress the self-interference are crucial to attaining IBFD acoustic communications. In this effort, we analyze the characteristic of the self-interference for the underwater acoustic channel through experimental measurements. Self-interference reduction using physical separation and digital cancellation is investigated under different transmitter-receiver geometries. An iterative IBFD receiver combining joint channel estimation, SI cancellation, and multichannel decision feedback equalizer is developed. The feasibility of coherent IBFD underwater acoustic communications was tested in a lake environment. The self-interference suppression methods and the receiver performance were evaluated using the experimental measurements. IBFD communications was demonstrated at 80 m. With 10 dB local self-interference source level reduction, IBFD communications was extended to the 170 m range. [Work supported by the National Science Foundation.]

Non-reciprocal diplexer and power combiner/divider from topological cavities with both splitting and combining functions

Multiplexers and power combiners/dividers are crucial in many applications of electromagnetic waves including microwave and terahertz communication. Full-duplex communication requires the separation of transmitted and received signals; thus, non-reciprocal multiplexers and power combiners/dividers are very essential. In this work, we present and numerically study a design concept for such non-reciprocal circuits from topological cavities. First, a quad-port circulator is made from a topological cavity and two trivial waveguides, which effectively operates as a non-reciprocal band-pass filter. Then, by parallelly connecting multiple circulators together, topological diplexers and power combiners/dividers are formed. These circuits are non-reciprocal due to the nature of photonic topological insulators, yet unlike the previously proposed non-reciprocal multiplexers or power combiners/dividers, they can both split and combine multiple frequencies or multiple power flows. The topological nature of the proposed circuits also makes them robust to any fabrication error and suitable for practical full-duplex communication applications.

Hybrid Uplink and Downlink Transmissions for Full-Duplex UAV Communication With RIS

This letter proposes a reconfigurable intelligent surface (RIS)-aided full-duplex unmanned aerial vehicle (FD-UAV) communication system. The FD-UAV performs its mission to communicate with an uplink (UL) user and a downlink (DL) user simultaneously over the same time-frequency dimension. The RIS is deployed to enhance the signal strength to the UL and DL users while suppressing the co-channel interference (CCI) from the user side. We aim to maximize the weighted sum rate of UL and DL transmissions by jointly optimizing the transmit power of the UL user, RIS’s phase-shift, and UAV trajectory. Although the formulated problem is difficult to solve due to its joint non-convexity, we propose an efficient algorithm based on the successive convex approximation and fractional programming techniques to solve the problem suboptimally. Simulation results show that the proposed RIS-aided communication system can achieve a significant sum rate gain over various bechmark schemes.

Low Access Latency and High Throughput for Full-Duplex Cognitive Radio Using Mobility Caching Placement Strategy

In a remote framework, the densely allotted radio range is not effectively utilized by an authorized primary user, which limits a secondary user to avoid disturbance to a primary user while utilizing a channel. To solve the shortage problem of accessible range, this study proposes a mobility caching placement strategy (MCPS) based sliding window scheme to optimize the latency and throughput of cognitive radio system. The performance parameters of the proposed system are analyzed using energy detection metrics by considering full-duplex communication. By the MATLAB analysis and the evaluation with and without self-interference suppression, the results demonstrate that the entrance inactivity of the MCPS based sliding window is diminished by a factor of 1.9 as contrasted with the existing full-duplex systems. With the improved latency and throughput, the proposed method can avoid the ruinous impacts of drawn-out self-residual suppression more effectively compared to the existing approaches.

Content Distribution Based on Joint V2I and V2V Scheduling in mmWave Vehicular Networks

With the explosive growth of vehicle applications, vehicular networks based on millimeter wave (mmWave) bands have attracted interests from both academia and industry. mmWave communications are able to utilize the huge available bandwidth to provide multiple Gbps transmission rates among vehicles. In this paper, we address the content distribution scheduling problem in mmWave vehicular networks. It has been challenging for all vehicles in the same network to complete content downloading due to the limited communication resources of roadside units (RSUs) and the high mobility of vehicles. We propose a joint vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) scheduling scheme to minimize the total number of content distribution time slots from a global optimization perspective. In the V2I phase, the RSU serially transmits integrity content to vehicles, which are selected according to the vehicular network topology and transmission scheduling scheme. In the V2V phase, full-duplex communications and concurrent transmissions are exploited to achieve content sharing between vehicles and improve transmission efficiency. Performance evaluations demonstrate that our proposed scheme reduces the number of time slots and significantly improves system throughput when compared with other schemes, especially under large-size file transfers and a large number of vehicles.

Simultaneous Wireless Power and Data Transfer: A Comprehensive Review

Simultaneous wireless power and data transfer (SWPDT) is widely investigated because of the increasing requirement for real-time communication between the primary and secondary sides in wireless power transfer systems. This article classifies SWPDT systems into four categories according to the type and number of data channels and data carrier generation method. They are power carrier-based SWPDT system, high-frequency data carrier-based SWPDT system, multiple inductive channels SWPDT system, and inductive–capacitive hybrid channels SWPDT system, respectively. Four key issues, including cross-talk minimization, improvement of signal-to-noise ratio, modulation method for high data rate and low bit error rate, and special design to achieve full-duplex communication and improve misalignment tolerance, are discussed. The advantages, disadvantages, and applications of the four types of SWPDT systems are summarized. Finally, conclusions and outlook of the SWPDT system are given.