Fernando Casadevall

ETSI reconfigurable radio systems: status and future directions on software defined radio and cognitive radio standards

This article details the current work status of the ETSI Reconfigurable Radio Systems Technical Committee, positions the ETSI work with respect to other standards efforts (IEEE 802, IEEE SCC41) as well as the European Regulatory Framework, and gives an outlook on the future evolution. In particular, software defined radio related study results are presented with a focus on SDR architectures for mobile devices such as mobile phones. For MDs, a novel architecture and inherent interfaces are presented enabling the usage of SDR principles in a mass market context. Cognitive radio principles within ETSI RRS are concentrated on two topics, a cognitive pilot channel proposal and a Functional Architecture for Management and control of reconfigurable radio systems, including dynamic self-organizing planning and management, dynamic spectrum management, joint radio resource management. Finally, study results are indicated that are targeting a SDR/CR security framework.

Discrete-time spectrum occupancy model based on Markov Chain and duty cycle models

This paper presents an empirical time-dimension model of spectrum use in the context of dynamic spectrum access. Concretely, a discrete-time two-state Markov chain with novel duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed model is assessed and corroborated with extensive empirical data from a multi-band spectrum measurement campaign. The obtained results demonstrate that the proposed approach is able to capture and reproduce with significant accuracy the statistical properties of spectrum use observed in real channels of various technologies.

Statistical Prediction of Spectrum Occupancy Perception in Dynamic Spectrum Access Networks

Cognitive radio nodes of a dynamic spectrum access network monitor the spectrum around them in order to detect and opportunistically exploit temporarily unoccupied spectrum gaps. The overall behavior of the whole network depends on the spectrum occupancy perceived by each node at its local environment. An appropriate understanding of the local perception of cognitive radio nodes in various scenarios and locations as well as its dependence on the propagation environment can provide valuable information for the design, dimensioning and performance evaluation of dynamic spectrum access networks. In this context, this work presents a novel and practical approach to predict the spectrum occupancy that would be perceived by cognitive radio nodes in realistic scenarios. Based on such approach, we explore the dependence of the spectrum occupancy perception with the considered scenario and location as well as the impact of particular parameters of the radio environment.

Spatial duty cycle model for Cognitive Radio

Spectrum occupancy modeling in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) constitutes a rather unexplored research area that still requires much more effort. This paper addresses the problem of modeling spectrum occupancy in the spatial domain by proposing a novel theoretical approach that enables modeling the occupancy level perceived at any geographical location based on the knowledge of some simple primary signal parameters. The validity of the theoretical model is verified with extensive empirical measurement results. Some examples of its potential applicability are discussed as well.

A Radio Spectrum Measurement Platform for Spectrum Surveying in Cognitive Radio

This paper presents a sophisticated radio spectrum measurement platform specifically envisaged and designed for spectrum occupancy surveys in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR). The presented tool is a very flexible computer- controlled radio measurement system, which has successfully been used in extensive spectrum measurement campaigns and empirical studies in the context of the DSA/CR technology. An exhaustive and in-depth description of the developed measurement platform is provided, with a special emphasis on implementation details and lessons learned during the development of the tool that may result helpful to other researchers and engineers in the development of similar radio spectrum measurement tools.

An overview of spectrum occupancy models for cognitive radio networks

The Dynamic Spectrum Access (DSA) paradigm based on the Cognitive Radio (CR) technology has emerged as a promising solution to conciliate the existing conflicts between spectrum demand growth and current spectrum underutilization without changes to the existing legacy wireless systems. The basic underlying idea of DSA/CR is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands temporarily unused by the licensed users. Due to the opportunistic nature of the DSA/CR paradigm, a realistic and accurate modeling of spectrum occupancy patterns becomes essential in the domain of DSA/CR research. In this context, this paper provides an overview of the existing spectrum occupancy models recently proposed in the literature to characterize the spectrum usage patterns of licensed systems in the time, frequency and space dimensions.

Modeling and simulation of joint time-frequency properties of spectrum usage in cognitive radio

The development of the Dynamic Spectrum Access/Cognitive Radio (DSA/CR) technology can significantly benefit from the availability of realistic models able to accurately capture and reproduce the statistical properties of spectrum usage in real wireless communication systems. Relying on field measurements of real systems, this paper analyzes the joint time-frequency statistical properties of spectrum usage and develops adequate models describing the observed characteristics. Based on such models, a sophisticated method is also proposed to generate artificial spectrum data for simulation or other purposes. The proposed method is able to accurately reproduce the statistical time-frequency characteristics of spectrum usage in real systems.

ETSI Reconfigurable Radio Systems — Software Defined Radio and Cognitive Radio standards

This paper details the current work status of the ETSI Reconfigurable Radio Systems (RRS) Technical Committee (TC) and gives an outlook on the future evolution. In particular, Software Defined Radio (SDR) related study results are presented with a focus on SDR architectures for Mobile Devices (MD), such as mobile phones, etc., as well as for Reconfigurable Base Stations (RBS). For MDs, a novel architecture is presented enabling the usage of SDR principles in a mass market context. Cognitive Radio (CR) principles within ETSI RRS are concentrated on two topics, a Cognitive Pilot Channel (CPC) proposal and a Functional Architecture (FA) for Management and Control of Reconfigurable Radio Systems, including Dynamic Self-Organising Planning and Management, Dynamic Spectrum Management, Joint Radio Resource Management, etc. Finally, study results are indicated which are targeting a SDR/CR security framework.

REM-based real time testbed: A proof of concept on the benefits of using REM for improving radio resource management capabilities

The knowledge of the statistical characterization of the primary user activity can make more efficient the spectrum selection techniques, which are a key technology to improve the Cognitive Radio (CR) systems performance. In order to provide this kind of primary user information, Radio Environment Maps (REM) data bases has been proposed. This paper presents a REM-based Real Time Testbed designed to validate and exploit the dynamicity of the REM data base to improve the performances of the Radio Resource Management (RRM) algorithms in the context of cognitive radio. The implemented testbed is a flexible HW/SW tool able to use spectrum measurements in licensed bands and validate the Cognitive Radio performance of the secondary users, without causing any interference on these primary users. In particular, the RRM strategy under study in the testbed envisages the optimization of the spectrum selection policy when secondary users, with different service profiles, access opportunistically a set of channels during the inactivity periods of primary users. The selection is done taking as input the statistical characterization of the primary user activity, which will be stored in the REM data base, and the secondary user service profiles.