A FPGA system for QRS complex detection based on Integer Wavelet Transform

Due to complexity of their mathematical computation, many QRS detectors are implemented in software and cannot operate in real time. The paper presents a real-time hardware based solution for this task. To filter ECG signal and to extract QRS complex it employs the Integer Wavelet Transform. The system includes several components and is incorporated in a single FPGA chip what makes it suitable for direct embedding in medical instruments or wearable health care devices. It has sufficient accuracy (about 95%), showing remarkable noise immunity and low cost. Additionally, each system component is composed of several identical blocks/cells what makes the design highly generic. The capacity of today existing FPGAs allows even dozens of detectors to be placed in a single chip. After the theoretical introduction of wavelets and the review of their application in QRS detection, it will be shown how some basic wavelets can be optimized for easy hardware implementation. For this purpose the migration to the integer arithmetic and additional simplifications in calculations has to be done. Further, the system architecture will be presented with the demonstrations in both, software simulation and real testing. At the end, the working performances and preliminary results will be outlined and discussed. The same principle can be applied with other signals where the hardware implementation of wavelet transform can be of benefit

Analysis of Traffic Accident Dynamics at Semaphored Crossroads – a Case Study

The paper deals with the analysis of dynamics of a traffic accident involving two vehicles and having happened at the semaphored crossroads in the afternoon hours i.e. when the traffic lights at the crossroads were functioning according to the programmed system and on the second programme. To prove the causes of the traffic accident, in analysing all the possible variants of the participants’ motions through the semaphored crossroads, the 3D display was also used. The value of EES (Energy Equivalent Speed) represents the starting parameter for calculation of vehicle’s speed in the instant of crash. Since the dynamics, or better to say motion of the participants in the traffic accident depends on properly working traffic lights, it is of great importance to present the work schedule of the traffic lights of the mentioned intersection, before we analyse the traffic accident itself. The control of all the results gained was carried out using computer programme package PC Crash 9.0 to simulate the crash. Great attention was also paid to the time intervals of vehicles’ motions. Also, the possibility of having avoided the accident in question was analysed

MIMO Networks: the Effects of Interference

Multiple-input/multiple-output (MIMO) systems promise enormous capacity increase and are being considered as one of the key technologies for future wireless networks. However, the decrease in capacity due to the presence of interferers in MIMO networks is not well understood. In this paper, we develop an analytical framework to characterize the capacity of MIMO communication systems in the presence of multiple MIMO co-channel interferers and noise. We consider the situation in which transmitters have no information about the channel and all links undergo Rayleigh fading. We first generalize the known determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues of arbitrary multiplicity. This enables the derivation of the distribution of the eigenvalues of Gaussian quadratic forms and Wishart matrices with arbitrary correlation, with application to both single user and multiuser MIMO systems. In particular, we derive the ergodic mutual information for MIMO systems in the presence of multiple MIMO interferers. Our analysis is valid for any number of interferers, each with arbitrary number of antennas having possibly unequal power levels. This framework, therefore, accommodates the study of distributed MIMO systems and accounts for different positions of the MIMO interferers.Comment: Submitted to IEEE Trans. on Info. Theor

Effects of climate change in the biomass of montado agro-sylvo-pastoral system

Mestrado em Engenharia do Ambiente - Instituto Superior de Agronomia - ULThe present dissertation aims at understanding how the future climate change scenarios may affect the production of grassland biomass in the montado agro-sylvo-pastoral system, by studying the effects of precipitation, aridity and topography (slope) in both the field, in different sites along a climatic gradient in Alentejo, and in greenhouse trials, using the seedbank collected at those sites. The impact of these three factors was studied independently, in order to understand the importance of each of them for biomass productivity and, consequently, determine the main driving factors. The results showed a stronger effect of precipitation during the growing season on biomass productivity, in both field and greenhouse trials, thus highlighting this factor, among the three studied, as the major driver of biomass response and consequently of future changes in the landscape of montado agro-sylvo-pastoral system in Alentejo. The comparison of field and greenhouse trial was also intended to study the seedbank ability to retain information regarding the past climate history of its site of origin – ‘memory’. Results showed that in greenhouse, regardless of the locations from where the soil samples were taken, the seed bank responded similarly in terms of biomass production, vegetation cover, species richness and flowering onset when subjected to similar favorable conditions in the greenhouse – regular and abundant watering.N/

Generalized Spatial Modulation in Large-Scale Multiuser MIMO Systems

Generalized spatial modulation (GSM) uses $n_t$ transmit antenna elements but fewer transmit radio frequency (RF) chains, $n_{rf}$. Spatial modulation (SM) and spatial multiplexing are special cases of GSM with $n_{rf}=1$ and $n_{rf}=n_t$, respectively. In GSM, in addition to conveying information bits through $n_{rf}$ conventional modulation symbols (for example, QAM), the indices of the $n_{rf}$ active transmit antennas also convey information bits. In this paper, we investigate {\em GSM for large-scale multiuser MIMO communications on the uplink}. Our contributions in this paper include: ($i$) an average bit error probability (ABEP) analysis for maximum-likelihood detection in multiuser GSM-MIMO on the uplink, where we derive an upper bound on the ABEP, and ($ii$) low-complexity algorithms for GSM-MIMO signal detection and channel estimation at the base station receiver based on message passing. The analytical upper bounds on the ABEP are found to be tight at moderate to high signal-to-noise ratios (SNR). The proposed receiver algorithms are found to scale very well in complexity while achieving near-optimal performance in large dimensions. Simulation results show that, for the same spectral efficiency, multiuser GSM-MIMO can outperform multiuser SM-MIMO as well as conventional multiuser MIMO, by about 2 to 9 dB at a bit error rate of $10^{-3}$. Such SNR gains in GSM-MIMO compared to SM-MIMO and conventional MIMO can be attributed to the fact that, because of a larger number of spatial index bits, GSM-MIMO can use a lower-order QAM alphabet which is more power efficient.Comment: IEEE Trans. on Wireless Communications, accepte