Leonardo Goratti

Enabling disaster-resilient 4G mobile communication networks

4G Long Term Evolution is the cellular technology expected to outperform previous generations and to some extent revolutionize the experience of users by taking advantage of the most advanced radio access techniques. However, the strong dependencies between user equipment, base stations, and the Evolved Packet Core limit the flexibility, manageability, and resilience of such networks. If the communication links between UE-eNB or eNB-EPC are disrupted, mobile terminals are unable to communicate. In this article, we reshape the 4G mobile network to move toward more virtual and distributed architectures to improve disaster resilience and drastically reduce the dependency between UE, eNBs, and EPC. First, we present the flexible management entity, a distributed entity that leverages on virtualized EPC functionalities in 4G cellular systems. Second, we introduce a novel device-to-device communication scheme allowing the UE in physical proximity to communicate directly without resorting to coordination with an eNB or EPC entity.

Connectivity and security in a D2D communication protocol for public safety applications

Device-to-Device (D2D) communication is an important feature for many kinds of mobile networks and in particular for the UMTS Long Term Evolution Advanced (LTE-A) cellular technology, where an underlay network can be created between User Equipments (UEs) without the support of an evolved Node B (eNB). The possibility to allow direct links between UEs plays an important role when the commercial LTE infrastructure is subject to failures or becomes unavailable after a disaster. Project ABSOLUTE, in scenarios for public safety, proposes raising in the sky a balloon with attached a 4G eNB (AeNB) to restore temporarily connectivity. In all cases in which UEs are out-of-coverage of the AeNB like in indoors, D2D becomes crucial. In this work, we propose to establish direct links employing a communication protocol that relies on the transmission of beacon frames sent in broadcast mode by selected UEs. We delve security aspects of this D2D protocol suitable for Public Safety (PS) users with out-of-coverage UEs based on sharing encryption keys. We pursue a network connectivity analysis of the secure protocol whereby we are able to show the existence of tradeoff points between connectivity and the increased overhead added by security for different values of the system parameters.

V-Cell: Going beyond the cell abstraction in 5G mobile networks

Past years have witnessed the surge of mobile broadband Internet traffic due to the broad adoption of a number of major technical advances in new wireless technologies and consumer electronics. In this respect, mobile networks have greatly increased their availability to meet the exponentially growing capacity demand of modern mobile applications and services. The upcoming scenario in the near future lays down the possibility of a continuum of communications thanks also to the deployment of so called small cells. Conventional cellular networks and the small cells will form the foundation of this pervasive communication system. Therefore, future wireless systems must carry the necessary scalability and seamless operation to accommodate the users and integrate the macro cells and small cells together. In this work we propose the V-Cell concept and architecture. V-Cell is potentially leading to a paradigm shift when approaching the system designs that allows to overcome most of the limitations of physical layer techniques in conventional wireless networks.

Ultra-wide band sensor networks in oil and gas explorations

Seismic exploration and monitoring for oil and gas reservoirs is a peculiar application that requires a large number (1000-2000 nodes/sqkm) of geophone sensors deployed outdoors over large areas (≥ 40 sqkm) to measure backscattered wave fields from artificial sources. A storage/processing unit or sink node collects the measurements from all the geophones to obtain an image of the sub-surface. The existing cabling system to connect sensors is known to cause inefficiencies, large logistic and weight costs, as well as insufficient flexibility in survey design. Oil companies are therefore expecting that wireless connectivity will provide the enabling technology for future seismic explorations. This application represents a new challenging research area for the wireless community. Early results suggest that current off-the-shelf radio solutions do not guarantee the minimum requirements in terms of system usability and energy consumption, not even for current deployment size. This article presents a tutorial view to introduce the basic principles of seismic acquisition systems that are necessary to define the wireless geophone network specifications. Strict sampling synchronization constraint over large geographic areas, high precision sensor localization, and high data rate are all requirements calling for a scalable network system where Ultra-Wide Band radio transmissions play a key role as the only viable technology.

Introducing Mobile Edge Computing Capabilities through Distributed 5G Cloud Enabled Small Cells

Current trends in broadband mobile networks are addressed towards the placement of different capabilities at the edge of the mobile network in a centralised way. On one hand, the split of the eNB between baseband processing units and remote radio headers makes it possible to process some of the protocols in centralised premises, likely with virtualised resources. On the other hand, mobile edge computing makes use of processing and storage capabilities close to the air interface in order to deploy optimised services with minimum delay. The confluence of both trends is a hot topic in the definition of future 5G networks. The full centralisation of both technologies in cloud data centres imposes stringent requirements to the fronthaul connections in terms of throughput and latency. Therefore, all those cells with limited network access would not be able to offer these types of services. This paper proposes a solution for these cases, based on the placement of processing and storage capabilities close to the remote units, which is especially well suited for the deployment of clusters of small cells. The proposed cloud-enabled small cells include a highly efficient microserver with a limited set of virtualised resources offered to the cluster of small cells. As a result, a light data centre is created and commonly used for deploying centralised eNB and mobile edge computing functionalities. The paper covers the proposed architecture, with special focus on the integration of both aspects, and possible scenarios of application.

Technology pillars in the architecture of future 5G mobile networks: NFV, MEC and SDN

This paper analyzes current standardization situation of 5G and the role network softwarization plays in order to address the challenges the new generation of mobile networks must face. This paper surveys recent documentation from the main stakeholders to pick out the use cases, scenarios and emerging vertical sectors that will be enabled by 5G technologies, and to identify future high-level service requirements. Driven by those service requirements 5G systems will support diverse radio access technology scenarios, meet end-to-end user experienced requirements and provide capability of flexible network deployment and efficient operations. Then, based on the identified requirements, the paper overviews the main 5G technology trends and design principles to address them. In particular, the paper emphasizes the role played by three main technologies, namely SDN, NFV and MEC, and analyzes the main open issues of these technologies in relation to 5G.

Effect of Impulse Radio–Ultrawideband Based on Energy Collection on MAC Protocol Performance

In this paper, we analyze the effects of the probabilities of detection, false alarm, and frame collision survival (in the presence of simultaneous transmissions) on medium access control (MAC) protocols using impulse-radio-ultrawideband (IR-UWB) energy-collection noncoherent receivers. The MAC protocols that were considered are all IEEE 802.15.4 compatible, i.e., the IEEE 802.15.4a optional UWB clear-channel-assessment mode, the IEEE 802.15.4a ALOHA mode, and a protocol termed preamble sense multiple access (PSMA). The impact on the network throughput, energy consumption, and delay are analytically derived and verified by simulation. The results show that these effects have a considerable impact on the performance of IR-UWB MAC protocols, and a classical analysis does not properly evaluate the protocolspsila performances. The results compare the performances of the MAC protocols and highlight a number of issues with regard to adapting narrowband protocols to UWB systems. The probability of frame collision survival on simultaneous transmissions is shown to have a significant impact on the performance of a MAC protocol. The comparison shows superior performance of the PSMA protocol under typical wireless-sensor-network operation ranges.

A novel device-to-device communication protocol for public safety applications

The UMTS Long Term Evolution (LTE) is the latest and most advanced cellular technology that is coming to market. As LTE and its advanced version promise unprecedented peak data rates both in uplink and downlink, they seem to represent a striking solution for many fields requiring mobile broadband access. Nowadays, one area that is strongly emerging is represented by public safety communications. In this field, users not only need to communicate in traditional cellular fashion but they also need to communicate directly in case the network infrastructure is temporary unavailable or if the operating conditions prevent reliable links. In the the literature this is referred to as device-to-device (D2D) communication mode. This paper investigates D2D communications where beacon-enabled and simple LTE terminals are scattered over the area of a major event according to two homogeneous Poisson Point Processes. The contribution of this paper is twofold: we first devise an innovative D2D protocol and then we investigate the probability of LTE mobile terminals to form in D2D networks using a stochastic geometry approach.

Design and performance of contention based MAC protocols in WBAN for medical ICT using IR-UWB

This paper focuses on wireless body area networks (WBAN) targeted for medical ICT applications. The studied network follows a typical IEEE 802.15.4 beacon-enabled star topology. We simulate the collection of medical data from patients using wireless sensors. Impulse radio ultra wideband (IR-UWB) is chosen as a physical layer technology, in compliance with the IEEE 802.15.4a standard. Two random access methods, slotted Aloha (S-Aloha) and preamble sense multiple access (PSMA) are studied in terms of throughput and energy consumption. This paper has two main objectives: 1) to address realistic performance of the two selected MAC protocols, accounting for false alarm, miss-detection and capture effect, when using IR-UWB; 2) to obtain feedback information on the design of medical networks that use the IEEE 802.15.4 beacon-enabled star topology. Therefore, the performances are obtained increasing the number of active sensors, varying in parallel typical superframe parameters as beacon order and superframe order to test the reaction of the network at the introduction of an inactive period.

A novel multi-hop secure LTE-D2D communication protocol for IoT scenarios

The Internet-of-Things (IoT) is promising to inter-connect physical objects and machines in an intelligent network. In this context, scalable and resilient Machine-to-Machine (M2M) communication protocols are required, and the new Device-to-Device (D2D) feature of the 4G system constitutes an appealing solution. Standardization activities are still in progress, but the rapid diffusion of both LTE and IoT devices and applications leads to development of experimental proposals aimed at merging these two technologies. We contribute in this work with a novel D2D communication protocol, which enables user equipments (UEs) to become the hubs of machine-type traffic by means of a suitable radio interface and upload data in the Web via the mobile network, thus opening to new cloud services. The protocol we propose is designed for multi-hop communications between D2D-enabled terminals and it is equipped with a light-weight security mechanism. It is meant to address the communication needs of UEs inside mobile network coverage, and those of UEs that suffer from scarce radio coverage. In terms of performance, we analyse connectivity and security in the multi-hop D2D network, taking into account the interference created by the transmission of beacon signals during the discovery phase of the wide network. We resort to stochastic geometry to model the end-to-end delay and communication resilience of the multi-hop D2D network.