A wide variety of applications for road safety and traffic efficiency are intended to answer the urgent call for smarter, greener, and safer mobility. Although IEEE 802.11p is considered the de facto standard for on-the-road communications, stakeholders have recently started to investigate the usability of LTE to support vehicular applications. In this article, related work and running standardization activities are scanned and critically discussed; strengths and weaknesses of LTE as an enabling technology for vehicular communications are analyzed; and open issues and critical design choices are highlighted to serve as guidelines for future research in this hot topic.

Ubiquitous, reliable and low-latency machine-type communication, MTC, systems are considered to be value-adds of emerging 5G cellular networks. To meet the technical and economical requirements for exponentially growing MTC traffic, we advocate the use of small cells to handle the massive and dense MTC rollout. We introduce a novel 3GPP-compliant architecture that absorbs the MTC traffic via home evolved NodeBs, allowing us to significantly reduce congestion and overloading of radio access and core networks. A major design challenge has been to deal with the interference to human-type traffic and the large degree of freedom of the system, due to the unplanned deployments of small cells and the enormous amount of MTC devices. Simulation results in terms of MTC access delay, energy consumption, and delivery rate corroborate the superiority of the proposed working architecture.

The Internet of Things (IoT) will shortly be undergoing a major transformation from a sensor-driven paradigm to one that is heavily complemented by actuators, drones, and robots. The real-time situational awareness of such active systems requires sensed data to be transmitted in the uplink to edge-cloud, processed, and control instructions transmitted in the downlink. Since many of these applications will be mission critical, the most suitable connectivity family will be cellular due to the availability of licensed spectrum able to protect the offered communications service. However, while much focus in the past was on the uplink of machine-type communications, little attention has been paid to the end-to-end reliability, latency, and energy consumption comprising both up and downlinks. To address this gap, in this paper, we focus on the definition, design, and analysis of machine-type multicast service (MtMS). We discuss the different procedures that need to be redesigned for MtMS and we derive the most appropriate design drivers by analyzing different performance indicators, such as scalability, reliability, latency, and energy consumption. We also discuss the open issues to be considered in future research aimed at enhancing the capabilities of MtMS to support a wide variety of 5G IoT use cases.

This paper addresses the design of an adaptive resource allocation policy for the efficient delivery of multicast services in Long Term Evolution (LTE) systems. The proposed approach overcomes the intrinsic inefficiencies of Conventional Multicast Scheme (CMS) related to the different channel quality experienced by the involved users. The basic idea is to split any multicast group into subgroups and apply subgroup-based adaptive modulation and coding schemes, which enable a more efficient exploitation of multi-user diversity. The distribution of users into subgroups is determined by the solution of an optimization problem, aiming to improve the network throughput while guaranteeing fairness among multicast members.

Despite of the undisputed benefits of the long term evolution-advanced (LTE-A) networks, offering support for group-oriented services challenges the evolved multimedia broadcast multicast services (eMBMS) design in LTE-A. This is especially important when delivering video content with high bitrate requirements. The conventional multicast scheme (CMS) is proposed as a radio resource allocation solution for eMBMS to serve all multicast group members with the data rate supported by the receiver with the worst channel conditions. In this paper, we propose a novel radio resource management approach, the device-to-device (D2D)-enhanced CMS with single frequency (D2D-SF). This proposal extends the CMS with additional D2D communications in order to increase the aggregate data rate of the cell, while also maintaining the typical CMS short-term fairness. D2D-SF makes use of one or more mobile subscriber devices as forwarding devices (FD) to retransmit the data received from the base station (BS) over direct local links to other members of the multicast group. The proposed solution supports both high-rate modulation and coding schemes on the downlink from BS to FDs, and reaches cell-edge devices (hence, experiencing worse channel conditions) through high-performing D2D links (improving this experience). Testing shows how the single frequency-based D2D CMS paradigm proposed, complemented by two novel strategies for selecting FDs, achieves significant enhancements of the overall performance when delivering video content compared to both the state-of-the-art multicast solutions and novel solutions that do not employ a single-frequency paradigm.

NarrowBand-Internet of Things (NB-IoT) is a radio access technology recently standardized by 3GPP. To provide reliable connections with extended coverage, a repetition transmission scheme is applied in both Random Access CHannel (RACH) procedure and data transmission. In this letter, we model RACH in the NB-IoT network taking into account the repeated preamble transmission and collision using stochastic geometry. We derive the exact expression of RACH success probability under time correlated interference, and validate the analysis with different repetition values via independent simulations. Numerical results have shown that the repetition scheme can efficiently improve the RACH success probability in a light traffic scenario, but only slightly improves that performance with very inefficient channel resource utilization in a heavy traffic scenario.