Full Duplex Radios

A multiuser full-duplex (FD) two-way communication system with decode-and-forward (DF) relaying protocol is investigated over time-selective fading channels. The effect of imperfect channel state information (CSI) is considered. The fading channel based approach is used to characterize the residual self-interference (RSI) at FD nodes. The outage performance of the considered system is investigated for different scheduling schemes based on the availability of CSI at the relay node. We derive the closed-form tight approximate expressions for the system outage probability assuming independent and non-identically distributed Rayleigh fading channels. Further, the tightness of the approximation presented is verified through Monte-Carlo simulations. Our analysis reveals the significant insights about the impact of time-selective fading, imperfect CSI, and RSI on the performance of the considered system.

The role of interference in wireless networks has recently been profoundly rethought with the emergence of new techniques for combating it and exploit it to maximize the use efficiency of the physical resources. This paper presents a two-way relay channel using a lattice-based physical layer network coding scheme, a massive MIMO array, and in-band full-duplex, taking into account the residual self-interference that results after applying recently developed cancellation techniques for the loopback interference. The proposed scheme is able to ultimately exchange information across the TWRC in only one time slot, whereas four time slots would be needed in a conventional TWRC. The system's performance is shown to be mostly dependent on the number of antennas at the relay, and also dependent on the channel state information of all the channel matrices, including the one describing the loopback interference at the relay. For base-stations and relays with a few hundred antennas, the proposed scheme is feasible for wireless systems.
Index Terms—In-band full-duplex, massive multiple-input multiple-output (MIMO), Physical Layer Network Coding (PLNC), Two-way Relay Channel.

Incorporating full duplex operation in Multiple Input Multiple Output (MIMO) systems provides the potential of boosting throughput performance. However, the hardware complexity of the analog self-interference canceller in emerging full duplex MIMO designs mostly scales with the number of transmit and receive antennas, thus exploiting the benefits of analog cancellation becomes impractical for full duplex MIMO transceivers, even for moderate number of antennas. In this paper, we present two novel architectures for the analog canceller comprising of reduced number of cancellation elements, compared to the state of the art, and simple multiplexers for efficient signal routing among the transmit and receive radio frequency chains. One architecture is based on analog taps (tap refers to a line of fixed delay, variable phase shifter, and attenuator) and the other on AUXiliary (AUX) Transmitters (TXs) that locally generate the cancellation signal. In contrast to the available analog cancellation architectures, the values for each tap or each AUX TX and the configuration of the multiplexers are jointly designed with the digital transmit and receive beamforming filters according to certain performance objectives. Focusing on a narrowband flat fading channel model as an example, we present a general optimization framework for the joint design of analog self-interference cancellation and digital beamforming. We also detail the sum rate optimization objective together with its derived solution for the latter architectural components. Representative computer simulation results demonstrate the superiority both in terms of hardware complexity and achievable performance of the proposed low complexity full duplex MIMO schemes over the lately available ones.

In this paper, we study the problem of joint inband backhauling and interference mitigation in 5G heterogeneous networks (HetNets) in which a massive multiple-input multipleoutput (MIMO) macro cell base station equipped with a large number of antennas, overlaid with self-backhauled small cells is assumed. This problem is cast as a network utility maximization subject to wireless backhaul constraints. Due to the non-tractability of the problem, we first resort to random matrix theory to get a closed-form expression of the achievable rate and transmit power in the asymptotic regime, i.e., as the number of antennas and users grows large. Subsequently, leveraging the framework of stochastic optimization, the problem is decoupled into dynamic scheduling of macro cell users and backhaul provisioning of small cells as a function of interference and backhaul links. Via simulations, we evaluate the performance gains of our proposed framework under different network architectures and low/high...

—We consider a full-duplex (FD) decode-and-forward system in which the time-switching protocol is employed by the multiantenna relay to receive energy from the source and transmit information to the destination. The instantaneous throughput is maximized by optimizing receive and transmit beamformers at the relay and the time-split parameter. We study both optimum and suboptimum schemes. The reformulated problem in the optimum scheme achieves closed-form solutions in terms of transmit beamformer for some scenarios. In other scenarios, the optimization problem is formulated as a semidefinite relaxation problem and a rank-one optimum solution is always guaranteed. In the sub-optimum schemes, the beamformers are obtained using maximum ratio combining, zero-forcing, and maximum ratio transmission. When beamformers have closed-form solutions, the achievable instantaneous and delay-constrained throughput are analytically characterized. Our results reveal that beamforming increases both the energy harvesting and loop interference suppression capabilities at the FD relay. Moreover, simulation results demonstrate that the choice of the linear processing scheme as well as the time-split plays a critical role in determining the FD gains. Index Terms—Full-duplex, wireless power transfer, decode-and-forward relay, throughput, outage probability.

—This paper proposes a virtual harvest-transmit model and a harvest-transmit-store model for amplify-and-forward full-duplex relay (FDR) networks with power splitting-based simultaneous wireless information and power transfer. The relay node employs a battery group consisting of two rechargeable batteries. By switching periodically between two batteries for charging and discharging in two consecutive time slots of each transmission block, all the harvested energy in each block has been applied for full duplex transmission in the virtual harvest-transmit model. By employing energy scheduling, the relay node switches among the harvesting, relaying, harvesting-relaying, and idle behaviors at a block level, so that a part of the harvested energy in a block can be scheduled for future usage in the harvest-transmit-store model. A greedy switching policy is designed to implement the harvest-transmit-store model, where the FDR node transmits when its residual energy ensures decoding at the destination. Numerical results verify the outage performance of the proposed schemes.

Vehicles will be soon equipped with wireless communication systems enabling a variety of new services. At the basis of each service is the transmission of beacon messages that advertise of the vehicle presence. In this paper, we investigate long term evolution (LTE) as the enabling technology for vehicle to vehicle (V2V) beaconing, by exploiting: i) the direct device to device (D2D) communication provided by Release 12 of LTE; ii) the full duplex (FD) radio, which allows a wireless device to transmit and receive at the same time. Furthermore, we introduce a novel analytical framework to evaluate the resource occupation of the beaconing service in LTE and compare the results with those obtained using LTE for vehicle to infrastructure (V2I) communications.

In-band full-duplex transmission allows a relay station to theoretically double its spectral efficiency by simultaneously receiving and transmitting in the same frequency band, when compared to the traditional half-duplex or out-of-band full-duplex counterpart. Consequently, the induced self-interference suffered by the relay may reach considerable power levels, which decreases the signal-to-interference-plus-noise ratio (SINR) in a decode-and-forward (DF) relay, leading to a degradation of the relay performance. This paper presents a technique to cope with the problem of self-interference in broadband multiple-input multiple-output (MIMO) relays. The proposed method uses a time-domain cancellation in a DF relay, where a replica of the interfering signal is created with the help of a recursive least squares (RLS) algorithm that estimates the interference frequency-selective channel. Its convergence mean time is shown to be negligible by simulation results, when compared to the length of a typical orthogonal-frequency division multiplexing (OFDM) sequences. Moreover, the bit-error-rate (BER) and the SINR in a OFDM transmission are evaluated, confirming that the proposed method extends significantly the range of self-interference power to which the relay is resilient to, when compared with other mitigation schemes.

This paper investigates the outage performance of a multi-user decode-and-forward two-way relay system where the communicating nodes are equipped with fullduplex abilities. To characterize the residual self-interference (RSI) at the relay and user nodes, the fading channel based approach is used, and the RSI is modelled as a Rayleigh distributed random variable. The closed form expression for the outage probability is derived for the multi-user optimal scheduling scheme assuming independent and non-identically distributed channels. Significant insights about the impact of RSI on the system performance are observed. Specifically, it is noted that the RSI at relay affects the system more severely as compared to user nodes RSI. The analytical results are validated through simulations.

With the help of an in-band full-duplex relay station, it is possible to simultaneously transmit and receive signals from multiple users. The performance of such system can be greatly increased when the relay station is equipped with a large number of antennas on both transmitter and receiver sides. In this paper, we exploit the use of massive arrays to effectively suppress the loopback interference (LI) of a decode-and-forward relay (DF) and evaluate the performance of the end-to-end (e2e) transmission. This paper assumes imperfect channel state information is available at the relay and designs a minimum mean-square error (MMSE) filter to mitigate the interference. Subsequently, we adopt zero-forcing (ZF) filters for both detection and beamforming. The performance of such system is evaluated in terms of bit error rate (BER) at both relay and destinations, and an optimal choice for the transmission power at the relay is shown. We then propose a complexity efficient optimal power allocation (OPA) algorithm that, using the channel statistics, computes the minimum power that satisfies the rate constraints of each pair. The results obtained via simulation show that when both MMSE filtering and OPA method are used, better values for the energy efficiency are attained.

This document describes the problem space for the METIS research conducted in the radio link context. Firstly, a requirement analysis for the air interface design is conducted based on the test case descriptions presented in METIS deliverable D1.1. It follows an introduction of the research topics being pursued in the radio link research together with an illustration of how these topics are addressing the derived requirements. Moreover, it is shown which of those requirements address the needs of the METIS horizontal topics. To facilitate the achievement of these three objectives, a framework of General Requirements is introduced, which will be used throughout the project to assess and evaluate developed radio link solutions and to allow for measuring against the overall system performance goals.

The key performance metrics in wireless sensor networks are both network lifetime and an average time required to report an event reliably. The optimal solution must be taken into account to meet these metrics. Considering energy-latency constraints in sensor networks, we have developed a cluster architecture using mobile agents to detect the yarn break in spinning machine in textile industry. We have used the latency improved MAC layer protocol to access the channel in the cluster and also used energy efficient cluster formation algorithm based on residual energy of the sensor node. This protocol can handle multiple event messages efficiently. And, we mainly focused on simulating the behavior of mobile agents for information retrieval from a wireless sensor network in a event driven and poll driven wireless sensor network model.

We consider a bi-directional Full-Duplex (FD) Multiple-Input Multiple-Output (MIMO) communication system in which nodes are capable of performing transitter (TX)-Receiver (RX) digital precoding/combining and multi-tap ana-log cancellation, and have individual Signal-to-Interference-plus-noise Ratio (SINR) requirements. We present an iterative algorithm for the TX powers minimization that includes closed-form expressions for the TX/RX digital beamformers at each algorithmic iteration step. Our representative simulation results demonstrate that the proposed algorithm can reduce residual Self-Interference (SI) due to FD operation to below −110dB, which is the typical noise floor level for wireless communications. In addition, our design outperforms relevant recent solutions proposed for 2-user MIMO systems (the so called MIMO X channel) in terms of both power efficiency and computational complexity.

The global bandwidth scarcity and the ever-growing demand for fast wireless services have motivated the quest for new techniques that enhance the spectral efficiency (SE) of wireless systems. Most conventional SE increasing methods (e.g., adaptive modulation and coding) have already been exhausted. Single-channel full-duplex (SCFD) communication is a new attractive approach in which each node may simultaneously receive and transmit over the same frequency channel, and thus, it has the potential to double the current SE figures. In this paper, we derive a model for the signal-to-interference-plus-noise ratio (SINR) in a SCFD-based cellular system with imperfect self-interference cancellation. Furthermore, given a set of uplink and downlink quality of service requirements, we answer the following two fundamental questions. First, is this set achievable in the SCFD-based cellular system? Second, if the given set is achievable, what is the optimal achieving policy? To that end, we provide a unified model for the SCFD-based cellular system, and give insights in the matrix of interference channel gains. Simulation results suggest that depending on the locations of the users, a combination of full-duplex and half-duplex modes over the whole network is more favourable policy.

Incorporating full duplex operation in Multiple Input Multiple Output (MIMO) systems provides the potential of boosting throughput performance. However, the hardware complexity of the analog self-interference canceller scales with the number of transmit and receive antennas, thus exploiting the benefits of analog cancellation becomes impractical for full duplex MIMO transceivers. In this paper, we present a novel architecture for the analog canceller comprising of reduced number of taps (tap refers to a line of fixed delay and variable phase shifter and attenuator) and simple multiplexers for efficient signal routing among the transmit and receive radio frequency chains. In contrast to the available analog cancellation architectures, the values for each tap and the configuration of the multiplexers are jointly designed with the digital beamforming filters according to certain performance objectives. Focusing on a narrowband flat fading channel model as an example, we present a general optimization framework for the joint design of analog cancellation and digital beamforming. We also detail a particular optimization objective together with its derived solution for the latter architectural components. Representative computer simulation results demonstrate the superiority of the proposed low complexity full duplex MIMO system over lately available ones.

The problem of user scheduling and power allocation in full-duplex (FD) cellular networks is considered, where a FD base station communicates simultaneously with one half-duplex (HD) user on each downlink and uplink channel. First, we propose low complexity user scheduling algorithms aiming at maximizing the sum rate of the considered FD system. Second, we derive the optimal power allocation for the two communication links, which is then exploited to introduce efficient metrics for FD/HD mode switching in the scheduling procedure, in order to further boost the system rate performance. We analyze the average sum rate of the proposed algorithms over Rayleigh fading and provide closed-form expressions. Our representative performance evaluation results for the algorithms with and without optimal power control offer useful insights on the interplay among rate, transmit powers, self-interference (SI) cancellation capability, and available number of users in the system.