Martine Villegas

Survey on spectrum utilization in Europe: Measurements, analyses and observations

This paper presents major results and comparisons of radio spectrum utilization measurements that have been carried out in three different locations in Europe, namely in the suburb of the city of Brno in the Czech Republic and in the suburb and the city of Paris in France during years 2008 and 2009 respectively. The analyzed radio bandwidth extends from 400 MHz to 3 GHz. The measurement method is based on the energy detection principle. Utilization performance and behaviors of major wireless communication systems and primary wireless system within different regions and different environments are investigated here. Our analyses pick out correlations between spectrum utilization within different regions and summarize common observations and physical aspects that will have to be considered in the future radio spectrum management to assure efficient spectrum utilization.

EER architecture specifications for OFDM transmitter using a class E amplifier

This letter presents envelope elimination and restoration (EER) architecture specifications in the case of orthogonal frequency division multiplex C band transmission. A key point is the recombination of envelope and phase information by supply modulation of the power amplifier (PA). Imperfections, such as time mismatch and phase noise can reduce the performances of the transmission. Compression and conversion effects when supply modulating the PA are introduced in this letter with the simulation of a class E power amplifier. This amplifier was designed under HP-ADS using a nonlinear MESFET model. Results are reported in terms of error vector measurement and spectrum for two different numbers of sub-carriers 32 and 128 in 16-QAM and 64-QAM cases.

Towards cognitive radio networks: Spectrum utilization measurements in suburb environment

This paper deals with spectrum utilization measurements in the frequency band from 100 MHz up to 3 GHz. The measurement is based on the energy detection principle using wideband logarithmically periodic antenna. The results point out the fact, that the frequency spectrum is not utilized in an optimal manner and that there do exist less or more utilized licensed frequency bands that could be possibly used by cognitive radios in an opportunistic way. Cognitive radio concept for better spectrum utilization is introduced here along with an overall approach regarding spectrum utilization in the next generation wireless networks.

Influence of time and processing mismatches between phase and envelope signals in linearization systems using envelope elimination and restoration, application to Hiperlan2

This paper is a theoretical and experimental study of the influence of time and processing mismatches between the envelope and the phase of an OFDM in an envelope elimination and restoration (EER) linearization system. We give the theoretical expression of the power spectral density of the distorted signal in the case without intersymbol interference at the emitter. In the general case, we give the average power of the distortion as a function of the time mismatch. We also propose an approximation of the distorted signal as a delayed version of the original signal, that explains the observed rotations of the constellations at the receiver on the different OFDM carrier. Others effects of EER principle are also studied, such as limitation of envelope and phase bandwidth and non-linearity of the envelope restoration command.

Analysis of a PLL based frequency synthesizer using switched loop bandwidth for Mobile WiMAX

This paper is focused on design aspects of a fractional-N PLL (phase locked loop) based frequency synthesizer proposed for the mobile WiMAX (worldwide interoperability for mobile access) standard. Requirements in terms of phase noise, settling time, frequency resolution and frequency of operation for WiMAX frequency synthesizer are presented. Furthermore, a high-speed CP (Charge Pump) PLL based synthesizer with a switched loop bandwidth is proposed and simulated. It has a 32 MHz reference frequency and a 50 kHz loop bandwidth with frequency raster of 125 kHz and 14 mus settling time.

Analysis of a modified Polar Sigma-Delta transmitter architecture for multi-radio applications

Polar sigma delta architecture has been previously proposed as an universal architecture able to offer multi-radio transmission in a mobile system. Furthermore, it has been validated for mobile WiMax, a very exigent communication standard in terms of envelope magnitude range and channel bandwidth. This paper briefly describes polar sigma delta architecture and proposes some improvements to it, particularly the digital mixing instead of analog mixing. Simulations of the enhanced architecture have been carried out using agilent advanced design system. Results are analyzed and new architecture advantages and drawbacks are pointed out.

Narrowband interference mitigation in UWB communication with energy detector

Ultra wideband (UWB) is a reliable candidate for supporting a physical layer in Body Area Networks (BAN) and because of their wideband, UWB systems can have their performance degraded due to the interference from narrowband transmission. Methods must be developed to protect UWB systems that are exposed to this negative impact of the narrowband interference (NBI). Most proposed solutions have been developed for coherent and transmitted-reference receivers but a very few of these principles are eligible with the noncoherent energy detector (ED) receiver. The work presented thereafter aims at proposing a novel method to identify and mitigate the narrowband interference in ultra wideband transmissions. We use an efficient algorithm with a modified but still simple energy detector, and the performance of the method is evaluated by means of computer simulations.

Specification of a polar sigma delta architecture for mobile multi-radio transmitter - validation on IEEE 802.16e

This paper proposes the use of a polar sigma- delta transmitter architecture in multi-radio systems, which could be employed in future cognitive radio applications. The transmitter architecture is validated for mobile WiMax, one of the most restrictive wireless standards because of its large envelope magnitude range and wide bandwidth. We focus on the bandpass antenna filter used after the power amplifier to restore envelope variation. We demonstrate the viability of using BAW filters in multi-radio systems.

Performance analysis of a BPSK-BPPM UWB physical layer for wireless body area networks

Because of the various application scenarios and use cases they make possible, Body Area Networks (BAN) have been investigated during the recent years by many academic and industrial communities. Among various technologies, Ultra Wide Band (UWB) was considered to be a good candidate for a physical layer in a BAN. Many propagation measurements have been conducted to study the wave propagation around the human body, and then design channel models. Our work aims at evaluating a UWB-Impulse Radio (IR) physical layer for BAN. This physical layer is based on Binary Phase Shift Keying (BPSK) and Binary Pulse Position Modulation (BPPM) modulations and it relies on the last IEEE 802.15.6 BAN channel models. This analysis presents the Bit or Symbol Error Rate (BER or SER) as a function of the signal to noise ratio (SNR). Computer simulations are conducted using IEEE 802.15.6 BAN channel models, and the system performances are investigated under coherent and noncoherent receivers.

A Cartesian Sigma-Delta transmitter architecture

This paper proposes a transmitter architecture that enables high Peak to Average Power Ratio (PAPR) signals transmission with good linearity and efficiency. The architecture is based on the principle of transforming a non constant envelope modulated signal in a constant one using lowpass Sigma-Delta (S?) modulators on the In-Phase and Quadrature baseband signal components. This conversion enables the use of a switched mode power amplifier which increases the transmitter power efficiency. Cartesian ΣΔ architecture performances have been studied and compared to those obtained with a Polar Sigma Delta transmitter architecture.