In-band full-duplex (IBFD) transmission represents an attractive option for increasing the throughput of wireless communication systems. A key challenge for IBFD transmission is reducing ...self-interference. Fortunately, the power associated with residual self-interference can be effectively canceled for feasible IBFD transmission with combinations of various advanced passive, analog, and digital self-interference cancellation schemes. In this survey paper, we first review the basic concepts of IBFD transmission with shared and separated antennas and advanced self-interference cancellation schemes. Furthermore, we also discuss the effects of IBFD transmission on system performance in various networks such as bidirectional, relay, and cellular topology networks. This survey covers a wide array of technologies that have been proposed in the literature as feasible for IBFD transmission and evaluates the performance of the IBFD systems compared to conventional half-duplex transmission in connection with theoretical aspects such as the achievable sum rate, network capacity, system reliability, and so on. We also discuss the research challenges and opportunities associated with the design and analysis of IBFD systems in a variety of network topologies. This work also explores the development of MAC protocols for an IBFD system in both infrastructure-based and ad hoc networks. Finally, we conclude our survey by reviewing the advantages of IBFD transmission when applied for different purposes, such as spectrum sensing, network secrecy, and wireless power transfer.
A new interference management strategy is proposed to enhance the overall capacity of cellular networks (CNs) and device-to-device (D2D) systems. We consider M out of K cellular user equipments ...(CUEs) and one D2D pair exploiting the same resources in the uplink (UL) period under the assumption of M multiple antennas at the base station (BS). First, we use the conventional mechanism which limits the maximum transmit power of the D2D transmitter so as not to generate harmful interference from D2D systems to CNs. Second, we propose a δ D -interference limited area (ILA) control scheme to manage interference from CNs to D2D systems. The method does not allow the coexistence (i.e., use of the same resources) of CUEs and a D2D pair if the CUEs are located in the δ D -ILA defined as the area in which the interference to signal ratio (ISR) at the D2D receiver is greater than the predetermined threshold, δ D . Next, we analyze the coverage of the δ D -ILA and derive the lower bound of the ergodic capacity as a closed form. Numerical results show that the δ D -ILA based D2D gain is much greater than the conventional D2D gain, whereas the capacity loss to the CNs caused by using the δ D -ILA is negligibly small.
This letter presents a new full duplex relay (FDR) system that features more efficient use of time resource and antennas. The proposed FDR system is constructed based on time and antenna-sharing and ...elimination of underlying interference. The underlying interference caused by time- and antenna-sharing is eliminated using precoding. We propose a design for the precoder and decoder, and investigate the achievable rate of the proposed FDR system when the precoder and decoder are applied. Simulation results show improved achievable rate and BER performances with the proposed FDR system compared to half duplex and conventional full duplex relay systems.
We consider energy harvesting cognitive radio networks in which a secondary transmitter harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the ...spectrum licensed to the primary network. The primary traffic is modeled as a time-homogeneous discrete Markov process, and the secondary transmitter may not be able to operate continuously due to sporadic and unstable energy sources. At the beginning of each time slot, the secondary transmitter thus needs to determine whether to remain idle so as to conserve energy, or to execute spectrum sensing to acquire knowledge of the current spectrum occupancy state. It also needs to configure the spectrum sensor detection threshold to achieve an effective tradeoff between false alarms and misdetections. This sequential decision-making, done to maximize the expected total throughput, requires the joint design of a spectrum sensing policy and a detection threshold under the energy causality and collision constraints. We formulate this stochastic optimization problem as a constrained partially observable Markov decision process (POMDP), and then convert it to a computationally tractable unconstrained POMDP. Numerical results show that the proposed approach enables efficient usage of the harvested energy by exploiting the temporal correlation of the primary traffic.
We consider a cognitive radio network with an energy-harvesting secondary transmitter to improve both energy efficiency and spectral efficiency. The goal of this paper is to determine an optimal ...spectrum sensing policy that maximizes the expected total throughput subject to an energy causality constraint and a collision constraint. The energy causality constraint comes from the fact that the total consumed energy should be equal to or less than the total harvested energy, while the collision constraint is required to protect the primary user. We first show that the system can be divided into a spectrum-limited regime and an energy-limited regime depending on where the detection threshold for the spectrum sensor lies. Assuming infinite battery capacity, we derive the optimal detection threshold that maximizes the expected total throughput subject to the energy causality constraint and the collision constraint. Analytical and numerical results show that the system is energy-limited if the energy arrival rate is lower than the expected energy consumption for a single spectrum access. They also show that a decreasing probability of accessing the occupied spectrum does not always result in decreased probability of accessing the idle spectrum in the energy-limited regime.
We consider energy harvesting cognitive radio networks to improve both energy efficiency and spectral efficiency. The goal of this paper is to analyze the theoretically achievable throughput of the ...secondary transmitter, which harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the spectrum licensed to the primary network. By modeling the temporal correlation of the primary traffic according to a time-homogeneous discrete Markov process, we derive the upper bound on the achievable throughput as a function of the energy arrival rate, the temporal correlation of the primary traffic, and the detection threshold for a spectrum sensor. The optimal detection threshold is then derived to maximize the upper bound on the achievable throughput under an energy causality constraint and a collision constraint. The energy causality constraint mandates that the total consumed energy should not exceed the total harvested energy, while the collision constraint is required to protect the primary network from secondary transmission. Analytical results show the temporal correlation of the primary traffic to enable efficient usage of the harvested energy by preventing the secondary transmitter from accessing the spectrum that may be occupied by the primary network.
This paper evaluates the outage probability of cognitive relay networks with cooperation between secondary users based on the underlay approach, while adhering to the interference constraint on the ...primary user, i.e., the limited amount of interference which the primary user can tolerate. A relay selection criterion, suitable for cognitive relay networks, is provided, and using it, we derive the outage probability. It is shown that the outage probability of cognitive relay networks is higher than that of conventional relay networks due to the interference constraint, and we quantify the increase. In addition, the outage probability is affected by the distance ratio of the interference link (between the secondary transmitter and the primary receiver) to the relaying link (between the secondary transmitter and the secondary receiver). We also prove that cognitive relay networks achieve the same full selection diversity order as conventional relay networks, and that the decrease in outage probability achieved by increasing the selection diversity (the number of relays) is not less than that in conventional relay networks.
A new interference management scheme is proposed to improve the reliability of a device-to-device (D2D) communication in the uplink (UL) period without reducing the power of cellular user equipment ...(UE). To improve the reliability of the D2D receiver, two conventional receive techniques and one proposed method are introduced. One of the conventional methods is demodulating the desired signal first (MODE 1 ), while the other is demodulating an interference first (MODE 2 ), and the proposed method is exploiting a retransmission of the interference from the base station (BS) (MODE 3 ). We derive their outage probabilities in closed forms and explain the mechanism of receive mode selection which selects the mode guaranteeing the minimum outage probability among three modes. Numerical results show that by applying the receive mode selection, the D2D receiver achieves a remarkable enhancement of outage probability in the middle interference regime from the usage of MODE 3 compared to the conventional ways of using only MODE 1 or MODE 2 .
This paper describes the derivation of detection and false-alarm probabilities for energy detectors in cognitive radio networks when a sensing node of the secondary system has correlated multiple ...antennas. The sensing performance degradation due to the antenna correlation is then investigated based on the performance analysis. The conclusions of the analysis are verified by numerical simulation results.
We consider an energy-harvesting cognitive radio system where the secondary transmitter harvests energy. This system operates under an energy causality constraint mandating that the average energy ...consumption must not exceed the average harvested energy, and a collision constraint mandating the protection of the primary system. The purpose of this paper is to identify the optimal pairing of the sensing duration and the energy detector's sensing threshold in order to maximize the average throughput of the secondary network. Since the sensing duration and sensing threshold are intertwined with the energy causality constraint, they need to be redesigned with the purpose of conserving energy in mind. Hence, the sensing duration must be shorter while still satisfying the collision constraint. The numerical results show that the optimal sensing duration is determined based on which constraint, collision or energy causality, needs to have priority. In addition, the simulation results show a pairing of the optimal sensing duration and sensing threshold provided by the coordination between the two constraints, which gives insight into how to design them.
