Eduardo Cano

Interference assessment of DVB-T within the GPS L1 and Galileo E1 band

Global navigation satellite systems (GNSS) are highly susceptible to interference, due to their low signal power. This paper studies the impact of DVB-T on the GPS L1 and Galileo E1 frequency band. An analytical tool has been developed to evaluate the probability of detection in the presence of interference, taking into account the possible effects of fading on the GNSS signal. Further, the tracking of GNSS signals has been simulated, estimating the degradation of the signal quality. Measurements on different receivers complete the study and illustrate the effects of DVB-T.

Optimal Global Navigation Satellite System pulse blanking in the presence of signal quantisation

Pulsed interference can severely degrade the performance of a GNSS receiver. For this reason, several mitigation techniques have been developed for reducing the impact of disturbing signals. Among the different pulsed interference mitigation techniques, pulse blanking (PB) has received particular attention due to its simplicity and effectiveness. In this study, the performance of PB is assessed in the presence of signal conditioning and the impact of front–end parameters, such as the number of bits used for quantisation and the gain of the automatic gain control (AGC), is analysed. The theoretical analysis is supported by Monte Carlo simulations and experimental results, which show that signal conditioning plays a fundamental role in the design of interference mitigation techniques.

Performance analysis of WiMax systems in the presence of MB-OFDM UWB interference

The European Commission has recently adopted specific power spectral density masks for Ultra Wideband devices, with detect and avoid capabilities, for coexistence with licensed standards. Under these regulations, a novel approach for analysing the Ultra Wideband interference effects on the WiMax downlink is provided in this paper. The maximum permissible interference level, as well as the signal-to-interference level that allows the Ultra Wideband interference effects to be considered as negligible, are computed by means of analytical, numerical and experimental approaches. This analysis considers a WiMax receiver operating at its minimum sensitivity level. The bit error rate and the error vector magnitude of the WiMax link are the metrics employed in this work to characterise the interference effects for both frequency hopping and non-frequency hopping Ultra Wideband interferers.

On the evaluation of MB-OFDM UWB interference effects on a WiMAX receiver

The European Commission has recently adopted specific power spectral density masks for ultra wideband (UWB) devices, with detect and avoid capabilities, for coexistence with licensed standards. Under these regulations, a novel approach for analyzing the UWB interference effects on the WiMAX downlink is provided in this paper by means of a novel theoretical computation of the bit error rate (BER), simulation results, and measurements in a conducted modality. New analytical BER expressions for both uncoded and coded WiMAX systems, impaired by a single multiband-OFDM (MB-OFDM) UWB interference signal, are obtained in this paper for a Rayleigh fading channel. The BER is expressed in terms of the characteristic function of the interference signal. The maximum permissible interference levels and the signal-to-interference (SIR) values, which allow the UWB interference effects to be considered negligible, are estimated in this paper from simulation and measurement results. The analysis considers a WiMAX receiver operating at its minimum sensitivity level. The BER, the symbol error probability (SEP), and the error vector magnitude (EVM) of the WiMAX link are the metrics employed to characterize the interference effects for both frequency hopping and nonfrequency hopping UWB interferers.

Compatibility analysis between LightSquared signals and L1/E1 GNSS reception

This paper presents experimental results showing the impact of the proposed LightSquared Long Term Evolution (LTE) signals on reception of both Global Positioning System (GPS) and Galileo civil signals in the L1/E1 band. A model for determining the impact of the interfering signal on the victim Global Navigation Satellite System (GNSS) receivers is also provided and this model is validated against the experimental data. It is shown that Galileo E1 Open Service (OS) receivers will be, in general, marginally more susceptible to this form of interference due to its greater proximity to the edge of the L1 band (as will be the new GPS III civil signal receivers in this band). While it appears that, for now, the LightSquared network will not be deployed, the approach taken and the results obtained herein can be readily adapted for any future signal that may take the place of LightSquared.

Optimal power and bit allocation schemes for ultra wideband cognitive radio systems

An optimal power and bit allocation scheme for rate maximization in the ultra wideband (UWB) cognitive radio system is presented in this paper. The scheme generates a series of M-ary quadrature amplitude modulation (M-QAM) zones over each UWB subcarrier. Total transmit power is optimally distributed among the UWB subcarriers for the use of the M-QAM modulation with a maximum M on each subcarrier. This optimization is constrained by the probability of detection, probability of false alarm, bit error rate and the UWB transmit power spectral density mask. The performance of the scheme is analyzed over different UWB fading channels. The results show that the system data rate is significantly improved by using the proposed power and bit allocation scheme.

Speed Consistency in the Smart Tachograph

In the transportation sector, safety risks can be significantly reduced by monitoring the behaviour of drivers and by discouraging possible misconducts that entail fatigue and can increase the possibility of accidents. The Smart Tachograph (ST), the new revision of the Digital Tachograph (DT), has been designed with this purpose: to verify that speed limits and compulsory rest periods are respected by drivers. In order to operate properly, the ST periodically checks the consistency of data from different sensors, which can be potentially manipulated to avoid the monitoring of the driver behaviour. In this respect, the ST regulation specifies a test procedure to detect motion conflicts originating from inconsistencies between Global Navigation Satellite System (GNSS) and odometry data. This paper provides an experimental evaluation of the speed verification procedure specified by the ST regulation. Several hours of data were collected using three vehicles and considering light urban and highway environments. The vehicles were equipped with an On-Board Diagnostics (OBD) data reader and a GPS/Galileo receiver. The tests prescribed by the regulation were implemented with specific focus on synchronization aspects. The experimental analysis also considered aspects such as the impact of tunnels and the presence of data gaps. The analysis shows that the metrics selected for the tests are resilient to data gaps, latencies between GNSS and odometry data and simplistic manipulations such as data scaling. The new ST forces an attacker to falsify data from both sensors at the same time and in a coherent way. This makes more difficult the implementation of frauds in comparison to the current version of the DT.

Semi-Analytic Techniques for Fast MATLAB Simulations

Advances in electronics and telecommunications are leading to complex systems able to efficiently use the available resources. Fast electronics, complex modulation schemes and correction codes enable transmissions on channels with unfavorable characteristics, coexistence between different services in the same frequency bands and high transmission rates. However, the complexity of such communications systems often prevents analytical characterizations. For example, figures of merit such as the Bit Error Rate (BER) are difficult to determine analytically for transmission schemes involving correction codes and communication channels with Inter-Symbol Interference (ISI) and fading. In such cases, the system is characterized through Monte Carlo simulations [1, 2]. The Monte Carlo framework involves simulations of the whole system under analysis. For example, when considering a communications system, the whole transmission-reception chain is simulated. A large number of sequences are sent through the simulated system and the message recovered by the simulated receiver is compared to the original transmitted sequence. This comparison allows one to determine the average number of transmission errors and compute the BER.

An Aggregate UWB interference model for coexistence analysis

A new statistical model for the aggregate UWB interference, which accounts for the parameters related to the spectrum sensing requested by the detect-and-avoid procedure and the environment dependent conditions such as fading, is proposed in this paper. We compute the parameters of a truncated-stable distribution used for characterizing the aggregate interference. We further show how to apply our model to derive the bit error probability of a MC-OFDM victim receiver in the presence of aggregate UWB interference. In addition, we show how the impact of a less restrictive UWB emission mask can be quickly assessed using the proposed model.

Multiuser Spectral Efficiency Maximization in Cognitive Ultra Wideband Radio Systems

A novel multiuser dynamic radio resource allocation scheme for spectral efficiency optimization in a cognitive ultra wideband radio system is presented in this paper. A new expression of computing the interference power to the primary users over the UWB multipath channel is derived in this work based on the Fenton-Wilkinson method. The subcarriers of the UWB system are grouped into subcarrier blocks according to the system coherence bandwidth. Then, a series of M-ary quadrature amplitude modulation zones are generated over each UWB subcarrier block according to the channel gain of each block and the bit error rate threshold of the system. The transmitted power and bits are optimally distributed among the UWB subcarrier blocks for the use of those zones with a maximum modulation level on each subcarrier block. The performance of the radio resource allocation schemes is analyzed over different UWB channel models. The results show that the spectral efficiency of the system is significantly improved by an optimal resource allocation technique.