Full-duplex decode-and-forward relaying with joint relay-antenna selection

In this paper, we exploit the benefits of full-duplex (FD) transmission and reconfigurable intelligent surfaces (RISs) by considering a bidirectional full-duplex wireless communication system with the support of RISs. Specifically, cooperative communications are applied at two FD terminals in a RISs-assisted bidirectional full-duplex (RIS-FD) system. In this context, we successfully derive the mathematical expressions of the outage probability (OP) and the ergodic capacity (EC) of the RIS-FD system with a direct link between two terminals and multiple reflecting paths created by RISs over the Rayleigh fading channel. Numerical results show that the performance of the considered RIS-FD system depends significantly on the total number of reflecting elements in the RISs. Particularly, when the total number of reflecting elements is small, the OP and EC saturate at a high signal-to-noise ratio (SNR). However, when the total number of reflecting elements is large enough, OP decreases greatly while EC enhances significantly. In addition, the effect of residual self-interference (SI) caused by FD transmission on OP and EC is remarkable, even the residual SI level is very small. On the other hand, the influence of other system parameters such as the number of RISs (N) and the number of reflecting elements (L) are also investigated to fully consider the performance of the RIS-FD system. An important observation is that when current techniques cannot completely eliminate SI in FD transmission, the use of multiple RISs with larger L can indirectly reduce the impact of SI and significantly improve the performance of the proposed RIS-FD system. Finally, the obtained expressions are validated via Monte-Carlo simulations.

In full duplex (FD), which improves frequency efficiency and achieves flexible resource assignment between the uplink and downlink, self-interference (SI) from a transmitter should be suppressed by using antenna isolation, an analog SI canceler, and digital SI canceler (DSIC) to a level such that the data or control channel satisfies the required block error rate (BLER). This paper proposes an alternately iterative DSIC (AI-DSIC) structure for orthogonal frequency division multiplexing (OFDM) using FD. We first present the required SI suppression level considering SI, quantization noise of an analog-to-digital converter, and nonlinear distortions of a power amplifier and RF receiver circuitries for a direct conversion transceiver using FD. Then, we propose an AI-DSIC structure that iterates alternately the generation of the SI estimate, the downlink symbol estimate, and removal of each from the received signal in the downlink including SI. We investigate the average BLER performance of the AI-DSIC for OFDM using FD based on link-level simulations under the condition that the derived required signal-to-SI ratio is satisfied.

Simultaneous bidirectional transmission and recep- tion of signals on a single channel in a full duplex (FD) system is gaining increased attention from both academia and industry. Recent advances in radio transceiver design have been able to minimize the self interference (SI) to a great extent making realization of a FD transceiver possible. For FD deployment in a multi-cell environment, minimizing SI is not sufficient due to the presence of a complex array of network-wide interference. This paper investigates the critical deployment challenges for a dense urban FD multi- cell network and provides solutions for successful deployment of FD cellular networks. Extensive simulation results show that the proposed user selection and power control algorithms are able to increase the FD performance gain by more than 80% when compared to the traditional half duplex (HD) counterpart.

We investigate an amplify-and-forward (AF) full-duplex (FD) relay system, where the FD incurred self-interference (SI), through partial cancelation at relay, is treated as a useful source at destination to enhance degree of freedom in signal detection, while reducing the signal processing cost of SI cancelation. An independent component analysis (ICA) based equalization structure is employed at destination to separate and detect the desired signal from the residual SI in a semi-blind way. The mode of SI cancelation at relay is chosen adaptively based on the threshold of signal-to-interference ratio (SIR) at relay. The proposed FD relay system not only features reduced signal processing cost of SI cancelation, but also achieves much higher energy efficiency (EE) than conventional FD relay systems where SI is canceled as much as possible. Also, the proposed system enables full resource utilization via consecutive data transmission at all time and the same frequency, leading to much higher throughput and EE than the conventional time-splitting and power-splitting based SI recycling approaches that occupy partial resources. Last but not least, the proposed system demonstrates a bit error rate (BER) performance that is robust against a wide range of SI and close to the ideal case with perfect channel state information (CSI) and perfect SI cancelation, while requiring no training sequence for estimation of any channel involved.

The advent and advancement of full-duplex (FD) technology in radio transceivers is expected to lead to full-duplex enabled multi-cell (FD-MC) networks in next generation wireless communication systems. Additional interferences between FD nodes and devices are the main challenges for the deployment of such networks. As in an early deployment scenario where the base stations (BS) operate in FD mode while the user equipments (UE) remain in the half-duplex (HD) mode, the self-interference (SI) within the FD-BS, the mutual interference (MI) between the FD-BS's and between the HD-UE's paired for FD scheduling are the major issues that could jeopardize the capitalization of FD system gains if they are not well addressed. In this paper, we present a system architecture for multi-stage cancellation of SI and joint cancellation of MI and residual SI in an FD-MC network. Multiple orthogonal pilots and their derived forms are utilized for channel estimation during a common training period. System-level delay calibration necessary for SI and MI channel estimation and cancellation is also provided.

SummaryOne of the main imperfections degrading the performance of full‐duplex (FD) relaying systems is the outage floor. In this work, a power scaling method is proposed, which overcomes this effect even when there does not exist a direct channel between source and destination nodes. The system is composed of decode‐and‐forward (DF) FD relays over the Nakagami‐m fading environment. To promote system performance, joint antenna and relay selection methods are employed in the FD relaying systems. Each FD relay is equipped with multiple antennas for receiving and the other for transmitting the information. The transmitting and receiving antennas are chosen based on the instantaneous channel variations, and one relay is selected to improve the signal‐to‐interference and noise ratio (SINR) of the FD relaying system. The performance of the proposed design is investigated. Moreover, the closed‐form equations of the ergodic capacity and outage probability are attained. The analytical results are confirmed by different simulations. Results indicate that the proposed design achieves an additional spatial diversity gain because of using the antenna selection at the relay nodes. Moreover, by power scaling (PS) method, the system performance is effectively improved compared to the conventional FD relaying structures.

In-band Wireless Full Duplex communication systems are capable of transmimng and receiving in the same band by canceling the self-interference (SI) power originated during the transmission. However, several issues may degrade its performance, including the nature of wireless SI channel. In this work we study the distribution of the residual SI power of an in-band full-duplex analog post-mixer canceler, which represents the amount of uncanceled SI. The impact of the fading channel is evaluated on the distribution of the residual SI power. The results achieved confirm that the type of fading channel strongly impacts the distribution of the residual SI power. This is a first step to understand the stochastic properties of the residual SI power, which is an important feature when digital-domain cancellation is jointly adopted with analog-domain cancellation to account with the effects of the propagation channel.

We consider cooperative non-orthogonal multiple access (CNOMA) transmission through a full-duplex (FD) amplify-and-forward (AF) relay. Two CNOMA users are served by an access point (AP) through the FD-AF relay. FD relaying can be spectrally efficient if it sufficiently suppresses the self-interference (SI) from the FD operation. The feedback structure of the FD-AF relaying makes the convergence of the SI a critical problem because catastrophic system failure may occur if the system fails to converge the SI. The two linear beamforming algorithms proposed in this paper address these challenges, where the first is based on the zero-forcing (ZF) of the SI and the other regularizes the SI to improve the first scheme. The ZF-based algorithm completely nulls out the SI and incurs no convergence problems. In contrast, the second method is based on the regularization of SI to improve the first one, and it carefully locates the operating point of the FD-AF relay such that the system avoids the SI divergence. Numerical simulation results are provided to discuss the advantages and disadvantages of the proposed algorithms by comparing their average sum-rate performances.

In this paper, we investigate the fading two-hop full-duplex (FD) relay channel with self- interference, which is comprised of a source, an FD relay impaired by self-interference, and a destination, where a direct source-destination link does not exist. For this channel, we propose two buffer-aided relaying schemes with adaptive reception-transmission at the FD relay for the cases when the source and the relay both perform adaptive-rate and fixed-rate transmission, respectively. The proposed buffer-aided relaying schemes enable the FD relay to adaptively select to either receive, transmit, or simultaneously receive and transmit in a given time slot based on the qualities of the receiving, transmitting, and self-interference channels; a degree-of-freedom unavailable without buffer-aided relaying. Our numerical results show that significant performance gains are achieved using the proposed buffer-aided relaying schemes compared to conventional FD relaying, where the FD relay is forced to always simultaneously receive and transmit, and to buffer-aided half-duplex relaying, where the half-duplex relay cannot simultaneously receive and transmit. The main conclusion of this work is that FD relaying systems without buffer-aided relaying miss-out on significant performance gains.

Full-duplex (FD) wireless communication improves the attainable spectral efficiency of the wireless network with the simultaneous transmission and reception over the same frequency channel at a single timeslot. However, the effect of self-interference (SI) and inter-user interference (IUI) become crucial to take into consideration compared to the current half-duplex system. Many researches have been studied to suppress the SI and IUI, to design the medium access control (MAC) protocol, and to propose resource management techniques for realizing the FD system and truly achieving the double transmission capacity in the network. In this paper, we propose a novel FD MAC protocol with a mixture of concurrent and sequential transmission scheme, namely FD-MCST, for maximizing the transmission capacity in multihop wireless networks. Through FD-MCST, the transmitting node can cooperatively share the transmission capacity status for maximizing the network capacity. As a result, numerical simulations reveal that the proposed FD-MCST can accomplish a higher achievable network capacity of up to 1.7 times and nearly twice the achievable throughput with a reasonable amount of achievable transmission overhead about 7.7%, compared to the existing FD MAC protocols.

In this paper, a novel communication scheme that combines beamforming, energy harvesting, and cooperative non-orthogonal multiple access (NOMA) system is introduced. In the proposed scheme, NOMA is first combined with beamforming to serve more than one user in each beamforming vector. Later, simultaneous wireless information and power transfer (SWIPT) technique is exploited to encourage the strong user to relay the weak user's information messages in full-duplex (FD) manner. However, one major drawback of FD communications is the self-interference (SI) signal due to signal leakage from terminal's output to the input. Three different cases are adopted. In the first case, the SI signal is assumed to be fully cancelled at the strong user using SI cancellation techniques. In the second case, SI is only cancelled at the information decoding circuits, while being harvested in the energy harvester to provide extra energy. The third case investigates the impact of imperfect SI cancellation on system performance is investigated. It is proved that introducing SWIPT doesn't only motivate users to collaborate, but also mitigates the impact of the SI signal. In addition, the problem of total sum rate maximisation is formulated and solved locally by means of two-step difference of convex functions (DC)-based procedure. Furthermore, the outage probability of both weak and strong user is derived and provided in closed-form expressions. Numerical simulations are presented to illustrate the sum rate gain of the proposed scheme if compared with existing schemes, and to verify the derived formulas.

Recent works have demonstrated the feasibility and potential of full-duplex (FD) wireless systems to double the spectral efficiency of half-duplex (HD) systems. Self-interference (SI) cancellation is the key to FD communication and the residual SI is the major factor determining the performance of an FD radio. This paper presents a novel frequency domain based approach, for the reconstruction of SI signal in digital domain. Unlike the existing time domain reconstruction approach, which requires convolution, the proposed approach is simple and uses FFT processing for SI signal reconstruction. By means of computational complexity evaluation, it is shown that the proposed reconstruction approach offers 61% reduction in the floating point operations required to reconstruct SI signal. Furthermore, via detailed simulations on the performance of digital SI cancellation under fading channels, it is demonstrated that the SI suppression achieved with the proposed approach is not only comparable to existing approach, but with frequency domain SI channel estimates, it can offer 5-7 dB better cancellation under highly frequency selective fading conditions, suggesting its suitability for long range transmission.

Self-interference (SI) cancellation is one of the most important techniques for full duplex wireless communication. As an indispensable component, the active analog canceller (AC) needs to mitigate the analog SI to ensure it meets the analog-to-digital converter (ADC) sampling requirement. However, the active AC cancellation performance is often restricted by the nonideal electronic components, e.g., the tunable attenuator, the phase shifter and associated circuits, which introduce nonlinear distortions to the residual SI signal that enters the receive chain, as the transmit power increases. This paper presents a full duplex architecture with AC nonlinearity modeling and suppression by including an extra feedback loop right after the power amplifier and an AC nonlinear distortion modeling and cancellation process followed by SI channel estimation and digital SI cancellation. By analyzing the feedback signal feeding the AC and the residual signal after AC cancellation, the AC nonlinear distortion can be estimated and subsequently suppressed by subtracting its estimates from the received samples. The distortion-suppressed signal is then processed by the refined digital SI cancellation with channel estimation and mitigation to further improve the cancellation performance. Experiments are performed on 20-MHz Long Term Evolution-advanced signals to demonstrate the effectiveness of the proposed full duplex architecture with signal power ranging from -5 dBm to 23 dBm at the PA output while from -23 dBm to 5 dBm at the receiver front end.

Over the last decade, infrastructure relays have been employed by wireless standards, such as WiMAX and LTE, for coverage and performance enhancement. However, due to their Half-Duplex (HD) nature, these relays incur spectral losses and increase the end-to-end delay. In contrast, in-band Full-Duplex (FD) relays can effectively cope with these issues through simultaneous reception and forwarding, provided that the looped-back Self-Interference (SI) is sufficiently suppressed. Driven by the possible performance gain of FD relaying over traditional HD relay systems; in this work, we present the first implementation of IEEE 802.11a/g compliant FD relay system in GNU Radio framework. Given the Open Source nature of this real-time signal processing software, the implementation is completely transparent and can be studied in all details and modified if needed. For a holistic evaluation of our relay system, we implemented both Amplify and Forward (AF) and Decode and Forward (DF), the two widely adopted relaying strategies. We assess the performance of these relaying strategies both analytically and in simulation experiments. Our results demonstrate and underline the potential gains of full-duplex relays in-terms of spectral efficiency and end-to-end physical layer latency over traditional half-duplex relay systems.

Mitigating self-interference (SI) is vital for advancing simultaneous transmit and receive (STAR) systems. The noise and linearity of the canceller impose limitations on SI power handling. This article proposes a novel dual-path SI cancelling scheme for high-power SI handling. The proposed approach breaks self-interference cancellation (SIC) tradeoffs between operating frequency, SI power handling, and canceller noise/distortion by using a frequency-translated (FT) SI canceller and an auxiliary FT noise-cancelling (NC) path that cancels the noise/distortion from the primary canceller. This approach can work well for both full-duplex (FD) and frequency-division duplex (FDD) schemes. The 65-nm CMOS implementation achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 45-dB SIC for 12-dBm receiver (RX) SI peak power (9-dBm avg.) with only 4-dB noise figure (NF) degradation and 207-mW power consumption at 600 MHz. The SIC approach enables a blocker-1 dB with respect to SI of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 16 dBm (8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> higher than prior work) while operating from 0.5 to 1.3 GHz. Therefore, this implementation can support watt-level SI power handling with transmitter (TX)–RX isolation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 15 dB. This is demonstrated through measurements that show 30-dBm TX power handling with 22-dB initial isolation from the circulator.