To satisfy the high data demands in future cellular networks, an ultra-densification approach is introduced to shrink the coverage of base station (BS) and improve the frequency reuse. The gain in capacity is expected but at the expense of increased interference, frequent handovers (HOs), increased HO failure (HOF) rates, increased HO delays, increase in ping pong rate, high energy consumption, increased overheads due to frequent HO, high packet losses and bad user experience mostly in high-speed user equipment (UE) scenarios. This paper presents the general concepts of radio access mobility in cellular networks with possible challenges and current research focus. In this article, we provide an overview of HO management in longterm evolution (LTE) and 5G new radio (NR) to highlight the main differences in basic HO scenarios. A detailed literature survey on radio access mobility in LTE, heterogeneous networks (HetNets) and NR is provided. In addition, this paper suggests HO management challenges and enhancing techniques with a discussion on the key points that need to be considered in formulating an efficient HO scheme. INDEX TERMS Radio access mobility, cell selection, handover, LTE, 5G, NR, mobility enhancers. Ph.D. degree in electrical engineering with Aalto University, Finland. He has more than two years, from 2013 to 2015, of professional experience as an RF Planning and Optimization Executive at Wi-Tribe Pakistan Ltd. (Ooredoo Group). During his stay at KFUPM, he was associated with the King Abdullah University of Science and Technology (KAUST), Saudi Arabia, as a Visiting Student and a KFUPM-KAUST Joint Research Initiative. He has been a Researcher with the Helsinki Research Center, Huawei Technologies Finland Oy, since February 2018. His current research interest includes energy-efficient mobility for small-cell overlaid cellular networks. He received the Gold Medal Award for obtaining the first position in the B.Sc. degree. XAVIER GELABERT received the M.Sc. degree in electrical engineering from the KTH Royal Institute of Technology, Stockholm, in 2003, and the joint B.Sc. and M.Sc. degrees in telecom engineering and the Ph.D. degree (Hons.

Abstract-The Controller Area Network (CAN) bus serves as a legacy protocol for in-vehicle data communication. Simplicity, robustness, and suitability for real-time systems are the salient features of the CAN bus protocol. However, it lacks the basic security features such as massage authentication, which makes it vulnerable to the spoofing attacks. In a CAN network, linking CAN packet to the sender node is a challenging task. This paper aims to address this issue by developing a framework to link each CAN packet to its source. Physical signal attributes of the received packet consisting of channel and node (or device) which contains specific unique artifacts are considered to achieve this goal. Material and design imperfections in the physical channel and digital device, which are the main contributing factors behind the device-channel specific unique artifacts, are leveraged to link the received electrical signal to the transmitter. Generally, the inimitable patterns of signals from each ECUs exist over the course of time that can manifest the stability of the proposed method. Uniqueness of the channel-device specific attributes are also investigated for time-and frequency-domain. Feature vector is made up of both time and frequency domain physical attributes and then employed to train a neural network-based classifier. Performance of the proposed fingerprinting method is evaluated by using a dataset collected from 16 different channels and four identical ECUs transmitting same message. Experimental results indicate that the proposed method achieves correct detection rates of 95.2% and 98.3% for channel and ECU classification, respectively.

In this paper we address the impact of cell size on the handover procedure in a Long Term Evolution (LTE) network. In particular, we highlight the potential problems that may occur when small cell densification is applied. In addition, the impact of the User Equipment (UE) speed is also analyzed. System level simulations are provided using a detailed LTE network simulator accounting for multiple points-of-failure and channel modeling compliant with LTE standards. We conclude that a certain cell size can be found around which any increase or decrease of the cell size brings performance degradations due to different limitations in the uplink. The performance is also degraded as UE speed increases, especially for small cell sizes. And for large cell sizes, we note that low speed UEs handover failures may rise due to the inability to "escape" from a poor radio condition area.

No abstract

In this paper, we address the signaling overhead and the power consumption that results from the transmission of handover-related signaling in a Long Term Evolution (LTE) cellular network. Specifically, we analyze the contribution of the different signaling messages over the air-interface, and their impact on power consumption both at the eNB and at the User Equipment (UE) during handover (HO). A quantitative analysis is provided using system level simulations. We observe that, within the HO process, the largest contributor to air-interface signaling overhead is the transmission of the measurement report by the UE. This uplink (UL) transmission suffers from different channel impairments, due to interference and transmission range, for particular cell sizes. As a consequence, uplink signaling retransmissions are triggered causing higher signaling load and consequently higher power consumption, this being especially detrimental to battery-powered devices.