Full duplex (FD) communication is considered as a promising technology in the development of 5G-advanced and 6G systems as it theoretically doubles the capability of channel. However, this improvement relying on a simultaneously bidirectional manner of communication induces intrinsic self-interference (SI) demanding to be fully cancelled, which is generally intractable. This challenge is minimized in the scenario of integrated access and backhaul (IAB) networks operated in millimeter wave (mmW) band, as its transceivers are stationary and the complexity of SI is greatly reduced by beamforming technique. As a matter of fact, FD can be a pioneering technique to unlock the full potential mmW-based IAB network by releasing its suffering of the half-duplex inefficiency. This article presents the design principle and validation of a practical SI cancellation (SIC) technique in the case of high transmission power class in mmW-based IAB networks. The proposed technique sequentially eliminates SI from the spatial, RF, and digital domains that reduces the SI down to the noise floor. To validate the technique, a prototype system is developed in accordance with 5G IAB specifications and field tests are conducted. Results suggest that the designed mmW SIC transceiver significantly reduces residual-interference to noise ratio (R-INR) to 2.1 dB or less. Additionally, a system-level simulation is conducted in line with 5G IAB evaluation methodology, which explores the potential performance gain of the proposed technique in presence of cross-link interference (CLI). Results indicate that the method could yield a cell throughput gain of about 84%, compared to the current time division duplex deployment.

This paper emphasize the importance of the inter-sector self-interference (SI) cancellation to realize the full duplex (FD) for the practical three-sectored cell deployment scenario. We measure the inter-sector SI, the interference coming from the neighboring sector in the same site, using our FD enabled prototype testbed, and then we conduct the system-level simulation to validate the the impact of the inter-sector SI along with the intra-sector SI and cross link interference (CLI) in mmWave integrated access and backhaul (IAB) networks. From our extensive simulation results, the FD operation compared with the half duplex (HD) operation achieves throughput gain of 70% with inter-sector SI cancellation (SIC), while the FD operation achieves throughput gain of 20% without inter-sector SIC. Conclusively, the inter-sector SI should be effectively cancelled out to guarantee the meaningful FD gain over HD.

This paper presents novel ultrareliable and low-latency communication (URLLC) techniques for URLLC services, such as Tactile Internet services. Among typical use cases of URLLC services are teleoperation, immersive virtual reality, cooperative automated driving, and so on. In such URLLC services, new kinds of traffic such as haptic information including kinesthetic information and tactile information need to be delivered in addition to high-quality video and audio traffic in traditional multimedia services. Furthermore, such a variety of traffic has various characteristics in terms of packet sizes and data rates with a variety of requirements of latency and reliability. Furthermore, some traffic may occur in a sporadic manner but requires reliable delivery of packets of medium to large sizes within a low latency, which is not supported by current state-of-the-art wireless communication systems and is very challenging for future wireless communication systems. Thus, to meet such a variety of tight traffic requirements in a wireless communication system, novel technologies from the physical layer to the network layer need to be devised. In this paper, some novel physical layer technologies such as waveform multiplexing, multiple-access scheme, channel code design, synchronization, and full-duplex transmission for spectrally efficient URLLC are introduced. In addition, a novel performance evaluation approach, which combines a ray-tracing tool and system-level simulation, is suggested for evaluating the performance of the proposed schemes. Simulation results show the feasibility of the proposed schemes providing realistic URLLC services in realistic geographical environments, which encourages further efforts to substantiate the proposed work.

In Fifth-Generation (5G) New Radio (NR), satisfying a scenario called Ultra-Reliable and Low-Latency Communication (URLLC) is one of main goals. URLLC requires very high reliability with low latency, 1 ms user plane latency and 99.999% reliability. In Long Term Evolution-Advanced (LTE-A) system, however, latency requirement required by URLLC cannot be satisfied because resource allocation process increases latency. In this paper, we propose DRaMA, a grant-free uplink transmission scheme for low latency required in URLLC. With its own preamble and repetition pattern, a device repeatedly transmits the same packet using different frequency resources across consecutive mini- slots right after sending the preamble. We develop a mathematical model of collision probability to design repetition patterns, which determine the device- specific frequency resources. We demonstrate that DRaMA satisfied URLLC requirements in most cases by using system level simulation.