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.

In this paper, we propose a new user-plane (UP) network architecture for 6G cellular networks, where there is no distinction between radio access network (RAN) and core network (CN). We define a new network function (NF), called merged-UP (M-UP), where the UP functions of both RAN and CN sides are merged, thus enabling efficient protocol operations. We also propose an IP flow-based radio quality-of-service (QoS) control scheme to support 6G services with diverse QoS requirements. Based on our network testbed system, we show that the proposed architecture improves the system performance in terms of packet processing load and maximum throughput.

Network virtualization and cloudification are being actively introduced into mobile networks, but the current control-plane (CP) architecture, which distinguishes radio access network (RAN) from core network (CN), is inefficient in fully utilizing the flexibility provided by such technologies. In this paper, we propose a novel CP architecture, which is based on service-based interface (SBI) throughout the network without distinction between RAN and CN, thus reducing the delay and overhead of control signaling. The proposed architecture not only reduces the completion time and amount of signaling of the control procedures by up to 27% and 45%, respectively, but also provides a cloud-friendly environment in which slices and sub-networks with various characteristics can be easily operated by configuring the CP at will.

The ever-increasing roll-out of 5G integrated access and backhaul (IAB) networks in millimeter wave (mmW) band and its current hard-constraint of half duplex operation motivate the study of full duplex (FD) communication in a high power beamforming system. In an mmW IAB network using FD, the intrinsic self-interference inherits the nature of mmW high attenuation and cross link interference can be quite manageable via sharp beamforming between fixed nodes. As a matter of fact, mmW IAB could be a pioneering use case of FD in near future. In this article, a practical self-interference cancellation (SIC) transceiver design is presented targeting for “down to noise floor” SIC in the case of high transmission power class. We developed an mmW prototype testbed system in accordance with 5G IAB specifications. Our experimental results via prototype verifies the feasibility of the designed mmW SIC transceiver and confirms the potential of 2 times throughput gain from FD compared with conventional half duplex in an IAB scenario.

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.

To provide coverage to the network devices distributed all over the globe, non-terrestrial networks (NTNs) have been recognized to complement and extend the terrestrial network to remote areas. The Low Earth Orbit (LEO) NTNs face several unprecedented challenges over 5G-NR protocol due to high differential delay and Doppler shifts which drastically impacts the performance of NR-NTN users. In this work, we investigate the impact of large differential delay and Doppler shifts within a NTN cell on the 5G-NR resource allocation and medium access control (MAC) protocol. We then propose an uplink zone-based scheduling technique to address the high differential delay and Doppler shifts for LEO satellites for LEO satellite-based NTNs. Finally, we validate the performance of the proposed strategy by comparing it with the conventional 5G-NR protocol through numerical simulations over the recently developed Samsung’s NR-NTN System Level Simulator.

Moving networks is an emerging paradigm for next-generation communication networks that envisage a technology that could support moving vehicular user equipment (VUE) with high data-rates over a reliable connection under varied mobility scenarios such as high-speed trains, buses on the freeway, etc. However, while operating at mmWave frequencies, the direct base station (BS) to the VUE (BS-to-VUE) link is adversely impacted by penetration losses and frequent link outages. Link outages are caused primarily due to extremely poor Non-Line-of-Sight (NLOS) channel conditions at mmWave frequencies. To address this problem, a novel architecture has been proposed in literature where a vehicular moving-relay (MR) is introduced that serves the VUE via access link while the backhaul to the MR is provided by a BS. In this paper, we exhaustively analyze and numerically quantify the link fragility and outage for spatially consistent channel realizations at 28 and 73 GHz for links between the BS-to-VUE, BS-to-MR, and MR-to-VUE. Furthermore, in this study, we also capture the impact of frequent transitions among LOS and NLOS conditions, human blockage events, and penetration losses. The simulation results reveal that i) the direct link between the BS and VUE would be extremely fragile with link-outage probabilities 17% and 59.5% compared to the relay-aided link with link-outage probabilities 1.1 and 2% for 28 GHz and 73 GHz respectively and that ii) the BS-to-VUE link would be impacted severely by human blockages compared to relay aided links where only the last hop MR-to-VUE link is impacted by human blockages but negligibly due to its relatively short range. Lastly, we have determined closed-form analytical expressions to estimate the link-outage probability of the BS-to-MR link.

To avoid the latency from RRC state transition procedure, legacy network maintains UE as RRC connected state for pre-defined time duration even without any traffic arrival. However, it consumes UE battery rapidly because UE should monitor PDCCH, and send CQI feedback periodically. In this paper, we design the RRC connection control to enhance energy efficiency with moderate control signaling overhead. In RRC INACTIVE state, the newly introduced in NR, both network and UE save UE context including bearer configuration and security even after UE released from network. Owing to the saved UE context, the RRC state transition from RRC INACTIVE to RRC CONNECTED requires fewer number of CN signalling. And thus network can release UE to RRC INACTIVE more aggressively with shorter timer. Furthermore, we propose the connectionless data transmission in RRC INACTIVE without RRC state transition to RRC CONNECTED. In our performance analysis, UE energy consumption can be improved by 50% for the modem only and 18% reduction for the total device including display. Furthermore, when the small data or background (keep-alive) traffic is transferred in RRC INACTIVE, the energy efficiency is increased up to double.

To enlarge the cell capacity of mobile network, LTE network offloads its traffic to WLAN network. However, User Equipment (UE) can run out of batteries rapidly due to the independent operation of multi-Radio Access Technologies (RAT), LTE and WLAN. In this paper, we propose new Multi-RAT power saving scheme, Single-RAT Monitoring which remove the duplication of periodic wake up operation. Because UE has both LTE and WLAN modem, LTE modem can monitor the traffic status for WLAN link and then activate or deactivate the WLAN modem. Our performance analysis shows that the WLAN modem applying proposed Single-RAT Monitoring consumes 11%∼99% less energy with various traffic pattern.

Achieving significant throughput enhancement is a fundamental technical challenge for next generation cellular communication systems. In order to meet the projected 1000 fold traffic increase by the year 2020, the cellular systems are intensely focusing on ultra-densification by deploying a large number of small cells in a geographical area as a practical means for aggressively increasing the areal capacity. However cell densification is inherently limited by the high inter-cell interference that it inadvertently generates which seriously jeopardizes its gain and renders it practically unsuitable to meet the projected huge traffic explosion. Furthermore, increased densification leads to increased cell edges which in turn lead to rugged user experience. In order to overcome these daunting limitations and make densification a practical reality, we propose novel mobility robustness solutions which significantly decrease the number of handover failures and minimize the interruption in the ongoing services thereby leading to an appreciably better quality of experience for the user. The performance of the proposed schemes are evaluated using computer simulations and also in the drive test with a commercial handset and network equipment in the Gang-nam station area where the network configuration is close to the dense small cell environment. The proposed schemes enhance mobility performance up to 77% and reduce the service outage by 38% in the simulation with typical handover configurations. The enhancement is also observed from the drive tests in the commercial LTE small cell network around Gang-nam station area.

In this paper, a new slotted mode operation in a cdma2000 wireless system is proposed. The proposed operation is designed to support emerging services such as Push-To-Talk(PTT) that require low paging delay and low power consumption. The proposed operation tries to minimize the paging delay and maximize battery life while using the same amount energy as that of legacy reduced slot cycle mode with the assumption that the inter-arrival time of a PTT call follows an exponential distribution. In the performance analysis, it is shown that the average paging delay can be reduced or battery life can be reduced.