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Multicast and broadcast transmissions enhance the spectrum efficiency by delivering a single packet to multiple terminal users. The service continuity (SC) mechanism enables users to continue the service reception when the original transmission is not available anymore. For multicast and broadcast transmissions, the SC mechanism is different from that of unicast because of the different reception conditions. We design and analyze a set of SC mechanisms for New Radio (NR) multicast and broadcast transmissions (MBS) in this paper. The designed SC mechanisms do not require extra data-forwarding resources while meeting the interruption time requirements of diverse applications. To minimize the signalling overhead while meeting the latency requirements, we propose a dynamic SC configuration framework. With the framework, the network condition information is collected and the most suitable SC mechanism is chosen with its parameters. Simulation results demonstrate that the proposed dynamic configuration framework outperforms the LTE eMBMS solution with up to 84.07% signaling overhead reduction, facilitating a more efficient multicast and broadcast system in NR. [ABSTRACT FROM AUTHOR]

With the development of new radio (NR) technologies, sidelink (SL) transmission plays a more vital role in supporting low latency, higher reliability vehicle-to-everything (V2X) communications. Compared with the Long-Term Evolution (LTE), NR V2X aims to support enhanced V2X use cases with more stringent latency and reliability requirements. 3GPP introduces NR V2X distributed resource allocation to fulfill the low latency requirement to reduce the delay caused by requesting transmission resources from gNB. In distributed mode, UEs autonomously select resources without the scheduling from gNB. NR V2X introduces the physical sidelink feedback channel (PSFCH) to enhance transmission reliability. This paper presents the resource allocation mechanism for NR V2X distributed mode. Since the SL feedback channel is a new feature different from LTE V2X, we discuss the potential enhancements on resource allocation utilizing SL feedback channel to improve the reliability. This paper proposes a Receiver Grant-based resource allocation, which allows the receiver to send the grant with the feedback channel. By allowing the transmitter to indicate the pre-selected resources before the end of the previous reservation, the receiver can inform the transmitter about the collided resource selection through the PSFCH. The analytical models for NR V2X distributed mode with the feedback channel are also provided for UE to estimate the collision ratio. The simulation results and the analytical model show that the proposed Receiver (Rx) Grant-based resource allocation improves transmission reliability in terms of collision ratio. For future advanced V2X use cases, the analytical models provide an evaluation method and help UE make decisions to meet the reliability requirements. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model for millimeter wave (mmWave) cellular systems that characterizes user equipment (UE) power-saving constraint is studied. On the basis of the realistic radio propagation, we model the channel quality by curve fitting and create a Markov chain based channel model. The reference signal for channel measurement in conventional cellular systems can be transmitted to the whole cell at a time, but the beam sweeping is needed in mmWave systems in order to overcome the high path loss of high-frequency electromagnetic wave. This constraint further affects the timing of channel measurement, channel quality feedback, and power consumption. A novel beam-aware dormant mechanism for power saving in mmWave systems is proposed. UEs may enter the dormant mode for power-saving when the base station (BS) is not transmitting on their beams. Therefore, the BS is suggested to consider the time gap between channel measurement and data transmission when scheduling UEs. Beam-aware scheduling framework is proposed and integrated with the beam-aware dormant mechanism. It is shown that the policy to schedule a UE after its channel measurement outperforms the one to schedule every time slot. The simulation results and mathematical expression both demonstrate that the beam-aware media access control (MAC) framework improves throughput under power constraint. [ABSTRACT FROM AUTHOR]

Millimeter wave (mmWave) frequency bands offer a new frontier for cellular wireless systems to enable multigigabit communication. However, the availability and reliability of mmWave links are significantly limited due to its propagation characteristics. To mitigate the impact of such links and provide uninterrupted network services, the study of changing link condition is important. This paper proposes a reference signal (RS) transmission scheme for a mmWave cellular system using highly directional antenna beams. The aim of RS is to estimate the channel condition, which can be used for various purposes, e.g., initial access, beam alignment, and channel state information measurement. In particular, the objective of our proposed scheme is to enable efficient RS transmission in terms of angular coverage while ensuring a fair number of RS reception at all UEs within cell coverage. In addition, we provide a framework for studying the tradeoff between RS transmission overhead and RS measurement accuracy. Through theoretical analysis and simulation, we show that the proposed scheme achieves higher efficiency, especially in a small-cell scenario with smaller number of UE presence. [ABSTRACT FROM AUTHOR]

A control/user (C/U) plane-split network, where macro- and microevolved Node Bs (eNBs) are responsible for C/U-planes, respectively, is a potential 5G solution to address the problems experienced by high-speed railway communication systems such as frequent handovers (HOs), low system capacity, and low data rate. The C-plane transition occurs during an intermacro eNB HO to reduce the frequency of HOs. However, the intermacro-eNB HO in a C/U-plane-split network is prone to handover failures (HOFs) and long service interruption time similar to the traditional long-term evolution-advanced (LTE-A) HO without improvements because it is similar to an LTE-A HO between macro-eNBs from the perspective of C-plane transition. In this paper, we realize a C/U-plane-split network using the LTE-A dual-connectivity (DC) technique and propose a dc-based prevenient HO (PHO) scheme to improve the robustness of the intermacro-eNB HO. The proposed scheme specifically is an a priori method and uses the transmit diversity based on the dc technique to reduce the risk of HOFs and the long service interruption time. Further, we first develop the analytical expressions for HO performance for PHO and LTE-A HO, where HOFs are aligned with the LTE-A specifications such that they are defined as the association between the radio link monitor and HO processes. The analytical results are verified against simulation results. Through simulations, we compare PHO with LTE-A HO and the representative schemes of the previous literature in a variety of mobility performance metrics (such as the averages of the successful HO rate, the HOF rate, the radio link failure rate, the ping-pong rate, and the service interrupt time). The results confirm that the proposed scheme achieves superior performance in the key metrics of the successful HO rate and service interrupt time. [ABSTRACT FROM PUBLISHER]

Different from conventional mobile networks designed to optimize the transmission efficiency of one particular service (e.g., streaming voice/ video) primarily, the industry and academia are reaching an agreement that 5G mobile networks are projected to sustain manifold wireless requirements, including higher mobility, higher data rates, and lower latency. For this purpose, 3GPP has launched the standardization activity for the first phase 5G system in Release 15 named New Radio (NR). To fully understand this crucial technology, this article offers a comprehensive overview of the state-of-the-art development of NR, including deployment scenarios, numerologies, frame structure, new waveform, multiple access, initial/random access procedure, and enhanced carrier aggregation (CA) for resource requests and data transmissions. The provided insights thus facilitate knowledge of design and practice for further features of NR. [ABSTRACT FROM AUTHOR]

Cloud-based wireless networking system applies centralized resource pooling to improve operation efficiency. Fog-based wireless networking system reduces latency by placing processing units in the network edge. Confluence of fog and cloud design paradigms in 5G radio access network will better support diverse applications. In this article, we describe the recent advances in fog radio access network (F-RAN) research, hybrid fog-cloud architecture, and system design issues. Furthermore, the GPP platform facilitates the confluence of computational and communications processing. Through observations from GPP platform testbed experiments and simulations, we discuss the opportunities of integrating the GPP platform with F-RAN architecture. [ABSTRACT FROM PUBLISHER]