Martin Ekström

A Bluetooth Radio Energy Consumption Model for Low-Duty-Cycle Applications

This paper presents a realistic model of the radio energy consumption for Bluetooth-equipped sensor nodes used in a low-duty-cycle network. The model is based on empirical energy consumption measurements of Bluetooth modules. This model will give users the possibility to optimize their radio communication with respect to energy consumption while sustaining the data rate. This paper shows that transmission power cannot always be directly related to energy consumption. Measurements indicate that, when the transmission power ranges from -5 to +10 dBm, the difference in consumed energy can be detected for each transmission peak in the sniff peak. However, the change is negligible for the overall energy consumption. The nonlinear behavior of the idle state for both master and slave when increasing the interval and number of attempts is presented. The energy consumption for a master node is in direct relation to the number of slaves and will increase by approximately 50% of the consumption of one slave per additional slave, regardless of the radio setting.

Wireless ECG Network

This paper presents a time synchronized wireless ECG sensor network with reliable data communication. Wireless ECG systems are a popular research area where several research groups have presented point-to-point solutions. Alongside the wireless ECG research, the wireless sensor network research has created an increasing interest for secure, low power and predictable network applications. Combining these research areas is a natural step for the evolution of secure wireless monitoring of physiological parameters. In this study the Bluetooth radio standard has been chosen for its versatility. This paper focuses on both the hardware and the software development for a functional multihop ECG network using Bluetooth. The presented wireless ECG network is reliable up to link loss and is easily configured to send more or different types of signals. The system has been tested and verified for secure multihop communication.

Walking Intensity Estimation with a Portable Pedobarography System

The aim of this pilot study was to investigate the possibility to find a correlation between the output from a portable pedobarography system and the walking intensity expressed as walking speed. The system uses shoe insoles with force sensing resistors and wireless transmission of the data via Bluetooth. The force-time integral, at the toe-off phase of the step, for the force sensors in the forward part of the right foot was used to measure impulse data for 10 subjects performing walks in three different walking speeds. This data was then corrected by multiplication with the step frequency. This pilot study indicates that the portable pedobarography system output shows a linear relationship with the walking intensity expressed as walking speed on an individual level.

A wireless low latency control system for harsh environments

The use of wireless communication technologies in the industry offer severaladvantages. One advantage is the ability to deploy sensors where they previously could noteasily be deployed, for instanc ...

Evaluation of Closed-loop Feedback System Delay - A Time-critical Perspective for Neurofeedback Training

Neurofeedback in real-time has proven effective when subjects learn to control a BCI. To facilitate learning, a closed-loop feedback system should provide neurofeedback with maximal accuracy and mi ...

Evaluation of the IngVaL Pedobarography System for Monitoring of Walking Speed

Objectives Walking speed is an important component of movement and is a predictor of health in the elderly. Pedobarography, the study of forces acting between the plantar surface of the foot and a supporting surface, is an approach to estimating walking speed even when no global positioning system signal is available. The developed portable system, Identifying Velocity and Load (IngVaL), is a cost effective alternative to commercially available pedobarography systems because it only uses three force sensing resistors. In this study, the IngVaL system was evaluated. The three variables investigated in this study were the sensor durability, the proportion of analyzable steps, and the linearity between the system output and the walking speed. Methods Data was collected from 40 participants, each of whom performed five walks at five different self-paced walking speeds. The linearity between the walking speed and step frequency measured with R2 values was compared for the walking speed obtained ‘A’ only using amplitude data from the force sensors, ‘B’ that obtained only using the step frequency, and ‘C’ that obtained by combining amplitude data for each of the 40 test participants. Results Improvement of the wireless data transmission increased the percentage of analyzable steps from 83.1% measured with a prototype to 96.6% for IngVaL. The linearity comparison showed that the methods A, B, and C were accurate for 2, 15, and 23 participants, respectively. Conclusions Increased sensor durability and a higher percentage of analyzed steps indicates that IngVaL is an improvement over the prototype system. The combined strategy of amplitude and step frequency was confirmed as the most accurate method.

Extraction of working memory load and the importance of understanding the temporal dynamics

Working memory processing is central for higher-order cognitive functions. Although the ability to access and extract working memory load has been proven feasible, the temporal resolution is low and cross-task generalization is poor. In this study, EEG oscillatory activity was recorded from sixteen healthy subjects while they performed two versions of the visual n-back task. Observed effects in the working memory-related EEG oscillatory activity, specifically in theta, alpha and low beta power, are significantly different in the two tasks (i.e. two categories of visual stimuli) and these differences are greatest after image onset. Furthermore, cross-task generalization can be obtained by concatenating both tasks and although similar performances are observed before and after image onset, this study highlights the complexity of working memory processing related to different categories of visual stimuli, particularly after image onset, that are crucial to understand, in order to interpret the extraction of working memory load.

Experimental comparison study of UWB technologies for static human detection

This paper compares two dominant Ultra Wide Band(UWB) radar technologies Impulse and M-sequence for static human being detection in free space. The hardware and software platform for each system is described separately. These two radar platform performances are tested in real conditions and the results show that M-sequence UWB radar is better suited for detecting the static human target in larger distances.