LoRa, an abbreviation of Long Range, is a Low-Power Wide Area Network (LPWAN) radio technology that has quickly gained popularity as a communications means for the Internetof-Things (IoT). LoRa is typically used together with the MAC protocol LoRaWAN and operates in the license-free ISM-bands. As such, anyone is allowed to deploy their own LoRaWAN network, provided that they adhere to the Lo-RaWAN specication and ISM regulations. However, an uncoordinated deployment of LoRaWAN networks may cause neighboring networks to interfere and LoRaWAN frames to collide. In this paper, we present an in-depth investigation of LoRaWAN frame collisions-and the capture eect in particular-through various experiments. Contrary to previous research, we focus on correct reception of data at the application, instead of at the gateway, and we consider multi-gateway, multi-provider, and dense scenarios to obtain insight into collisions within actual networks.
The usage of wireless system and dry electrode on electroencephalography (EEG) device becomes widely demanding, particularly in commercial purposes. While the wireless system is needed for lesser cable interference and practical function for mobility, the dry electrode is very important for signal consistency in longer period of brainwave acquisition. Previously, a wireless EEG device was developed in our laboratory; however, the evaluation of the acquired brainwave is needed for further usage and development. This research aimed to compare the signal acquired by the developed EEG device using Emotiv Insight device as a benchmark, which is already an established wireless and dry electrode-based EEG on the market. The brainwave acquisitions were conducted on the subject while resting with eyes closed. AF3 and AF4 of frontal lobe channels were used as the electrode placements. The results were then characterized using frequency band analysis, SNR comparison, and general signal inspection. The result showed that the signal patterns on both devices were visually similar. A minor difference on the amplitude scale can be adjusted by normalization method. The result of alpha band calculation, which is normally detected in resting activity, found similar on both devices. Furthermore, the SNR result from developed device was considered fairly close to the benchmarking device. This study showed that developed EEG device was considered comparable to Emotiv Insight in detecting alpha band extracted from resting frontal lobe, as well as in the brainwave filtering process and accuracy.
Brainwave is widely used as an indicator of brain activity and can be detected by electroencephalography (EEG). The development of EEG device has become more advanced along with the invention of low-cost tiny electronic modules and wireless technology. This research aimed to develop a low-cost wireless modular device for brainwave acquisition based on Arduino microcontroller. The system was designed into sensor block for brainwave receiver and conditioning, and mainboard block for data processing. Dry-active electrode was developed as the sensor, followed by preamplifier module which was also installed at the sensor block. Active filter and DRL circuits were developed on the mainboard part. Arduino UNO was used as the main processor of the device. The developed modules were then evaluated using signal generator to examine the module characteristics and consistency. As the result, the preamplifier module was detected to reach 40.34 dB on gain ability. The cutoff frequency on the active filter module was calculated on 31 Hz. Furthermore, Arduino UNO was identified to have a consistency on input and output voltage.
Water surface level should get special attention as water can cause disasters such as flood when its surface exceeds a certain level. A real time early warning system to monitor water surface level is necessary for avoiding severe effects of flood to human life. A web-based water level measuring system using an ultrasonic sensor can be an alternative choice for developing the early warning system. It is known that the system has advantages in the installation and maintenance compared to other systems. This paper discusses the design of a water level measuring system integrated with an internet web server. Ultrasonic sensors are used to measure the water surface level. A GSM / GPRS-based communication system is applied for sending measured water levels to a web server. The results indicate that the measurement data are in accordance with the water levels manually obtained. The results also show that the system works real time.
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