Karina Mabell Gomez

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.

Aerial-terrestrial communications: terrestrial cooperation and energy-efficient transmissions to aerial base stations

Hybrid aerial-terrestrial communication networks based on low-altitude platforms are expected to meet optimally the urgent communication needs of emergency relief and recovery operations for tackling large-scale natural disasters. The energy-efficient operation of such networks is important given that the entire network infrastructure, including the battery-operated ground terminals, exhibits requirements to operate under power-constrained situations. In this paper, we discuss the design and evaluation of an adaptive cooperative scheme intended to extend the survivability of the battery-operated aerial-terrestrial communication links. We propose and evaluate a real-time adaptive cooperative transmission strategy for dynamic selection between direct and cooperative links based on the channel conditions for improved energy efficiency. We show that the cooperation between mobile terrestrial terminals on the ground could improve energy efficiency in the uplink, depending on the temporal behavior of the terrestrial and aerial uplink channels. The corresponding delay in having cooperative (relay-based) communications with relay selection is also addressed. The simulation analysis corroborates that the adaptive transmission technique improves overall energy efficiency of the network whilst maintaining low latency, enabling real-time applications.

Airborne Base Stations for Emergency and Temporary Events

This paper introduces a rapidly deployable wireless network based on Low Altitude Platforms and portable land units to support disaster-relief activities, and to extend capacity during temporary mass events. The system integrates an amalgam of radio technologies such as LTE, WLAN and TETRA to provide heterogeneous communications in the deployment location. Cognitive radio is used for autonomous network configuration. Sensor networks monitor the environment in real-time during relief activities and provide distributed spectrum sensing capacities. Finally, remote communications are supported via S-band satellite links.

Energy efficient cooperative strategies in hybrid aerial-terrestrial networks for emergencies

Aerial telecommunications networks based on Low Altitude Platforms (LAPs) are expected to optimally meet the urgent needs of emergency relief and recovery operations for tackling large scale natural disasters. The energy efficient operation of such networks is important given the fact that the entire network infrastructure including the battery operated ground terminals, exhibit requirements to operate under power constrained situations. In this paper, we show that the cooperation between mobile terrestrial terminals on the ground could improve the energy efficiency in the uplink depending on the temporal behavior of the terrestrial and the aerial uplink channels. We consider cognitive context aware capabilities that could be utilized to improve the overall lifetime of the mobile ground terminals by dynamically adapting between direct and cooperative relay links. We also discuss a novel network architecture constituted of an integrated and highly dynamic multi-purpose aerial-terrestrial communications infrastructure that can be contextually extended with fast-deploying aerial platforms for emergency communications.

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.

On the performance of aerial LTE base-stations for public safety and emergency recovery

Recent events have shown that in the aftermath of an unexpected incident, communication infrastructures play an important role in supporting critical services. Airborne communication networks have been recently studied for the provision of wireless communication services and it is a promising candidate for rapidly deployable and resilient emergency networks. However, the choice of communication technologies from Aerial platforms is a challenging issue and depends on a variety of factors including platform payload capacity, coverage and capacity requirements, to name a few. In this paper, we investigate the performance of 4G LTE-WiFi multimode base stations deployed on airborne platforms which provides coverage for first responders during emergencies. We present an adapted simulation model for the analysis of hybrid aerial-terrestrial systems and study the impact of platform elevation and mobility on the cell coverage and channel capacity. Performance analysis with a platform deployment of a single Aerial Base Station (eNodeB) corroborates that airborne units with 4G communication capabilities are very promising candidates for robust communication links during emergency relief operations.

Programming Software-Defined wireless networks

Programming a mobile network requires to account for multiple complex operations, such as allocating radio resources and monitoring interference. Nevertheless, the current Software-Defined Networking ecosystem provides little support for mobile networks in term of radio data-plane abstractions, controllers, and programming primitives. Starting from the consideration that WiFi is becoming an integral part of the 5G architecture, we present a set of programming abstractions modeling three fundamental aspects of a WiFi network, namely state management of wireless clients, resource provisioning, and network state collection. The proposed abstractions hide away the implementation details of the underlying wireless technology providing programmers with expressive tools to control the state of the network. We also describe a proof-of-concept implementation of a Software-Defined Radio Access Network controller for WiFi networks and a Python-based Software Development Kit leveraging the proposed abstractions. The resulting platform can be effectively leveraged in order to implement typical control tasks such as mobility management and traffic engineering as well as applications and services such as multicast video delivery and/or dynamic content caching.

Clustering approach for aerial base-station access with terrestrial cooperation

In this paper we propose a clustering mechanism for improved energy efficiency in aerial based access systems suitable for disaster recovery scenarios and large scale public events. The aerial base station is a low altitude platform (LAP) station that provides access to several terrestrial nodes on the ground over a prescribed coverage area. The terrestrial nodes are battery operated power constrained terminals that have got no base station access except for the LAP. Since the aerial uplink is a high cost energy link we propose a cluster based approach for LAP access. The proposed clustering mechanism is simulated and is compared with the well known clustering technique HEED for energy efficiency. Results show that the proposed clustering technique improves the energy efficiency compared to the non-clustering situation as well as to the HEED clustering technique.

Aerial base stations with opportunistic links for next generation emergency communications

Rapidly deployable and reliable mission-critical communication networks are fundamental requirements to guarantee the successful operations of public safety officers during disaster recovery and crisis management preparedness. The ABSOLUTE project focused on designing, prototyping, and demonstrating a high-capacity IP mobile data network with low latency and large coverage suitable for many forms of multimedia delivery including public safety scenarios. The ABSOLUTE project combines aerial, terrestrial, and satellites communication networks for providing a robust standalone system able to deliver resilience communication systems. This article focuses on describing the main outcomes of the ABSOLUTE project in terms of network and system architecture, regulations, and implementation of aerial base stations, portable land mobile units, satellite backhauling, S-MIM satellite messaging, and multimode user equipments.