José Carlos Ribeiro

Simulation of 802.21 handovers using ns-2

The new IEEE 802.21 standard specifies link layer intelligence and other related network information to upper layers in order to optimize handovers between networks of different types, such as WiMAX, Wi-Fi, and 3GPP. This paper makes a short description of 802.21 standard, how it is implemented in ns-2, and the signaling used in a handover between WiMAX and Wi-Fi. The paper also proposes a novel and very simple approach to determine the expected number of handovers in an ns-2 simulation and also evaluates the reliability and scalability of ns-2 when simulating 802.21 scenarios with multiple nodes.

Testbed for combination of local sensing with geolocation database in real environments

This article describes an experimental testbed that combines wireless microphone sensors with a web-based terrestrial digital video broadcasting geolocation database and a program making and special events spectrumbooking platform. Software defined radio and Internet technologies are the enabling tools in use. The key sensing techniques are identified and implemented. Test trials in a real scenario have shown that the platform was able to receive information from a DVB-T geolocation database and a PMSE spectrum-booking platform, updating the list of vacant channels with blind sensing techniques. The proposed method has shown capabilities to protect primary users of interferences from secondary users of the spectrum.

Some Initial Results and Observations from a Series of Trials within the Ofcom TV White Spaces Pilot

TV White Spaces (TVWS) technology allows wireless devices to opportunistically use locally-available TV channels enabled by a geolocation database. The UK regulator Ofcom has initiated a pilot of TVWS technology in the UK. This paper concerns a large- scale series of trials under that pilot. The purposes are to test aspects of white space technology, including the white space device and geolocation database interactions, the validity of the channel availability/powers calculations by the database and associated interference effects on primary services, and the performances of the white space devices, among others. An additional key purpose is to perform research investigations such as on aggregation of TVWS resources with conventional resources and also aggregation solely within TVWS, secondary coexistence issues and means to mitigate such issues, and primary coexistence issues under challenging deployment geometries, among others. This paper provides an update on the trials, giving an overview of their objectives and characteristics, some aspects that have been covered, and some early results and observations.

Smart interface switching for energy efficient vertical handovers in ns-2

The growing presence of concurrent heterogeneous wireless access networks, together with the increasing service demands from the end-users, require re-thinking of current access selection polices and appropriate management mechanisms, namely concerning quality of service, energy efficiency, etc. The recent IEEE 802.21 standard introduces link layer intelligence as well as related network information to upper layers in order to optimise handovers between networks of different technologies, such as WiMAX, Wi-Fi and 3GPP. With the massification of mobile terminals with multiple wireless interfaces it is important to efficiently manage those interfaces not only to appropriately provide the requested services to the user, but also to do that in an energy efficient way in order to allow higher mobility to the user by extending the battery life of its terminal. The study the IEEE 802.21 standard is briefly introduced, presented in the signalling in a handover between WiMAX and Wi-Fi, and exploited through an implementation in ns-2 introducing a simple, but effective, energy-saving approach.

Coexistence Analysis and Cognitive Opportunities Selection in GSM Bands

This paper presents a characterization of spectrum opportunities in GSM900 downlink bands, for fixed and mobile scenarios. A testbed to analyze coexistence between the licensed GSM900 downlink system and an OFDM based secondary system that opportunistically shares the same spectrum is presented. Coexistence analysis is based on metrics such as spectrum collisions rate and the secondary system throughput. Using this testbed a cognitive mechanism to classify and select stable opportunities is evaluated in realistic scenarios. Keywords-Cognitive radio, GSM900, coexistence, sensing.

A security framework for cognitive radio IP based cooperative protocols

This paper describes a new security framework that will leverage the security in cognitive radio cooperative protocols. The architecture uses the 802.1X access control mechanism and is supported by a Key Distribution Center (KDC) built upon an 802.1X Authentication Server. The KDC is used, together with a new terminal identification policy and modified DHCP servers, to provide proper resource allocation and message authentication in DHCP transactions. The KDC is also used to authenticate mappings between layer 2 and 3 addresses (ARP protocol) and to distribute session keys to neighbor cognitive radio terminals, allowing them to set up other peer-to-peer secure interactions using such session keys.

Towards a secure network architecture for smart grids in 5G era

Smart grid introduces a wealth of promising applications for upcoming fifth-generation mobile networks (5G), enabling households and utility companies to establish a two-way digital communications dialogue, which can benefit both of them. The utility can monitor real-time consumption of end users and take proper measures (e.g., real-time pricing) to shape their consumption profile or to plan enough supply to meet the foreseen demand. On the other hand, a smart home can receive real-time electricity prices and adjust its consumption to minimize its daily electricity expenditure, while meeting the energy need and the satisfaction level of the dwellers. Smart Home applications for smart phones are also a promising use case, where users can remotely control their appliances, while they are away at work or on their ways home. Although these emerging services can evidently boost the efficiency of the market and the satisfaction of the consumers, they may also introduce new attack surfaces making the grid vulnerable to financial losses or even physical damages. In this paper, we propose an architecture to secure smart grid communications incorporating an intrusion detection system, composed of distributed components collaborating with each other to detect price integrity or load alteration attacks in different segments of an advanced metering infrastructure.

Extending IOPT Nets with a Module Construct

Input-output place-transition nets (IOPT nets) is a Petri net based formalism targeted for the development of embedded systems controllers. It is an extension to common place-transition Petri nets, introducing constructs to model the communication between the controller and the environment and using an execution semantics assuring a deterministic behavior. However, IOPT nets and the supporting tools framework - the IOPT-Tools - do not have a mechanism to support model structuring. Since models are flat, all the graphical components and annotations are visualized in the same page. Systems with several dozens of nodes become very difficult to manage. In this paper a modular construct for IOPT nets is presented, helping to manage large-scale systems, and the reuse of model components across projects. The algebraic specification of the model is provided and an example illustrating the concept is presented.

Distributed controllers modeling through Petri nets with multi-asynchronous-channels

This paper proposes the concept of multi-asynchronous-channel for Petri nets. Petri nets extended with multi-asynchronous-channels and time-domains support the specification of distributed controllers, where each controller has a synchronous execution but the global system is asynchronous (globally-asynchronous locally-synchronous systems). Each multi-asynchronous-channel specify the interaction between two or more distributed controllers. These channels, together with the time-domain concept, ensure the creation of network-independent models to support implementations using heterogeneous communication networks. The created models support not only the systems documentation but also their validation and implementation through simulation tools, verification tools, and automatic code generators. An application example illustrates the use of a Petri net class extended with the proposed channels.

Towards an Advanced PKI-Based Security Solution for Next Generation e-Passport and Associated Applications: The NewP@ss Approach

The electronic passport, introduced not long ago, in 2005, is continuing to evolve in order to provide higher levels of authentication for citizens crossing international borders, while respecting their privacy. A brief overview of the whole e-passport architecture is presented, as well as the key aspects and changes that this document has been going through in its evolution. In this paper we present a promising novel PKI-based security solution that could be integrated in the next generation (4G) of electronic passports, namely in its supporting overall architecture, in the ambit of the NewP@ss project.