Design and validation of an adaptive Cubesat transmitter system using a Thermal Vacuum Chamber (TVAC)

CubeSat in a low earth orbit primarily uses a UHF transmitter with a fixed RF output power. In this paper, the design of the CubeSat transmitter with adaptive power controlability is presented. The design drive is to optimise the SNR and overcome the variability of the propagation path length due to different ground station elevation angles by adjusting its transmitting power. The TVAC test is conducted to validate the performance of the adaptive function in the transmitter. The TVAC is used to emulate the satellite condition in an outer space environment. Four thermal cycles starting from +60°C to -20°C with less than 10-5Pa pressure condition are employed, which was conducted at the KIT CeNT, Japan. The transmitter was integrated inside the satellite structure as a complete CubeSat system. The output power of the transmitter is tested from 0.5W to 2W based on the proposed satellite adaptive mode. The frequency stability of the transmitter is monitored and complies with an average of 70% below requirement, which is less than 2ppm. The results indicate that the RF output power is adjustable to operate as the proposed CubeSat adaptive transmitter in a thermal vacuum condition, which was first developed in Malaysia

Estimation of satellite link’s fade margin using non-meteorological technique and worst month analysis

Satellite technology is shifting to higher frequencies such as Q or V-band to cater to greater bandwidth and higher data rates applications such as videoconferencing, internet of things (IoT) and telemedicine. The main challenge in deploying high-frequency bands in heavy precipitation areas is severe rain attenuation. In this paper, a frequency scaling technique was developed to estimate the fade margin at a higher frequency. The worst month analysis was also conducted since the analysis is also important in determining dependable fade margin. The result was evaluated and analyzed using root mean square error (RMSE) and percentage error. The proposed model offers the smallest RMSE and lowest percentage error when compared to all existing prediction models. A dependable fade margin acquired from high-accuracy rain attenuation estimation is very important. This is to apply the best mitigation technique in overcoming rain attenuation in the satellite-Earth link so that, the best system performance can be delivered

Ku-band specific attenuation coefficients for high-throughput satellites in equatorial region

Ku-band have a larger attenuation during heavy rain in the equatorial region. Despite that, Ku-band has been identified as a frequency band in high-throughput satellite systems (HTS) for broadband satellite communication. The available rain fade prediction models are still not able to accurately predict rain attenuation in the equatorial region. The models depend on the specific attenuation parameters produced based on the international telecommunication union radiocommunication sector (ITU-R) instead of the measured value. Direct measurement of specific attenuation is more accurate but difficult to obtain because the correlation of rainfall rate and satellite signal loss due to rain must be obtained simultaneously. This paper aims to derive new specific attenuation frequency-dependent coefficients for Ku-band using the semi-empirical method. The Malaysia East Asia Satellite 3 (MEASAT-3) satellite data was collected using a 13 m antenna located at Cyberjaya, Selangor while the rainfall data was collected by the nearby hydrological station. The specific attenuation was obtained from correlations of the direct measurement of rain attenuation and rainfall rate. The new frequency-dependent coefficients for Ku-band specific attenuation values are k = 4.6690 and α = 0.1941. The newly acquired specific attenuation coefficients have improved the rain attenuation model prediction for the equatorial region

Two-year rain fade empirical measurement and statistics of earth-space link at ka-band in Malaysia

Satellite communication links at a frequency above 10 GHz experience severe attenuation due to rain, particularly in tropical regions. Reliable long-term rain fade empirical data for Ka-band satellite link in Malaysia and tropical areas are indeed limited. The main objective of this paper is to provide and present the findings of an empirically measured rain fade at the Ka-band of 20.01 GHz and the cumulative distribution analysis. An 8.1 m dual Gregorian dish antenna with 21 dB/K G/T and a meteorological standard dual type tipping bucket are used to measure the Ka-band beacon signal emanating from the MEASAT-5 satellite and the rainfall intensity, respectively, for a period of two years. Cumulative distribution of rain fade for monthly, annual and monsoon seasons were compiled to reflect the accurate changes in Malaysian weather. The measured rain fade is at 10 dB and 29 dB for the exceeded percentage of 0.3% and 0.1%, respectively. At rain fade of 33 dB, the receiver begins to saturate, resulting in a QoS of 99.9% for the Ka-band. The finding provides an insight to the actual rain fade experience for the practical implementation of Ka-band satellite link and future studies of rain fade models in tropical regions

Nanosatellites constellation as an IoT communication platform for near equatorial countries

Anytime, anywhere access for real-time intelligence by Internet of Things (IoT) is changing the way that the whole world will operate as it moves toward data driven technologies. Over the next five years, IoT related devices going to have a dramatic breakthrough in current and new applications, not just on increased efficiency and cost reduction on current system, but it also will make trillion-dollar revenue generation and improve customer satisfaction. IoT communications is the networking of intelligent devices which enables data collection from remote assets. It covers a broad range of technologies and applications which connect to the physical world while allowing key information to be transferred automatically. The current terrestrial wireless communications technologies used to enable this connectivity include GSM, GPRS, 3G, LTE, WIFI, WiMAX and LoRa. These connections occur short to medium range distance however, none of them can cover a whole country or continent and the networks are getting congested with the multiplication of IoT devices. In this study, we discuss a conceptual design of a nanosatellite constellation those can provide a space-based communication platform for IoT devices for near Equatorial countries. The constellation design i.e. the orbital plane and number of satellites and launch deployment concepts are presented

Assessment of monthly rain fade in the equatorial region at C & KU-band using measat-3 satellite links

C & Ku-band satellite communication links are the most commonly used for equatorial satellite communication links. Severe rainfall rate in equatorial regions can cause a large rain attenuation in real compared to the prediction. ITU-R P. 618 standards are commonly used to predict satellite rain fade in designing satellite communication network. However, the prediction of ITU-R is still found to be inaccurate hence hinder a reliable operational satellite communication link in equatorial region. This paper aims to provide an accurate insight by assessment of the monthly C & Ku-band rain fade performance by collecting data from commercial earth stations using C band and Ku-band antenna with 11 m and 13 m diameter respectively. The antennas measure the C & Ku-band beacon signal from MEASAT-3 under equatorial rain conditions. The data is collected for one year in 2015. The monthly cumulative distribution function is developed based on the 1-year data. RMSE analysis is made by comparing the monthly measured data of C-band and Ku-band to the ITU-R predictions developed based on ITU-R’s P.618, P.837, P.838 and P.839 standards. The findings show that Ku-band produces an average of 25 RMSE value while the C-band rain attenuation produces an average of 2 RMSE value. Therefore, the ITU-R model still under predicts the rain attenuation in the equatorial region and this call for revisit of the fundamental quantity in determining the rain fade for rain attenuation to be re-evaluated

Estimating losses at 40-GHz downlink using non-meteorological techniques in heavy rain areas

The advancement of satellite communication has arisen tremendously where higher capacity communications systems are needed. Most satellite engineers are shifting to Ka, Q, and V-band upcoming since the low frequencies such as below 10 GHz are already congested. Actual measurement data at millimetre-wave frequencies in tropical regions are minimal. The prediction of rain attenuation at frequencies above 10 GHz is required to determine a reliable fade margin. In this paper, a statistical frequency scaling technique has been developed as an alternative way of estimating rain attenuation. The technique was derived based on the correlation between the attenuation ratio of a higher and lower frequency against the attenuation at a lower frequency. The attenuations from the proposed model were compared to the proposed frequency scaling by International Telecommunication Union-R (ITU-R) as well as the conventional ITU-R rain prediction model. To deliver a reliable model, validation methods have been done using a set of data with different years and locations in tropical regions. A dependent prediction technique with the lowest root mean square error (RMSE) value and error was produced. This technique is beneficial in applying suitable mitigation techniques to moderate rain fade in tropical regions

Implementation of an E-voting prototype using Ethereum blockchain in Ganache network

Digitization of a secure electoral system capable of ensuring fairness and privacy has been a long-standing challenge for a variety of reasons. One is the system's reliance on a third-party organization to manage and verify election results, rendering it insecure. There is a possibility that data will be altered during the election process. As a result, a decentralized e-voting system application capable of verification will be developed in this work using blockchain technology. The Ethereum network and the Truffle framework will be used to implement smart contracts as self-executing electoral agreements. The Ganache (local blockchain) network design demonstrated that the prototype is capable of recording every voting transaction on the network without the use of a central database. The voter can verify the election result by inspecting each voting transaction on the local blockchain. The proposed design will ensure that all voting transactions are stored in a decentralized database, ensuring that no administrative control over the ballot is exercise

Development of video-based emotion recognition system using transfer learning

Due to the complexity of its system and the numerous advantages of its implementation, video emotion identification is a popular area of study today. There have been multiple ways implemented. In this project, emotion recognition in videos will be performed using deep learning. The model will include initialization, feature extraction, emotion categorization, and prediction. LeNet and AlexNet, two distinct neural networks, are used to extract features and classify emotions. There will be some parameter tuning to determine if it enhances the employed architecture’s performance, including optimizers and batch size. Each architecture for deep learning will generate a final forecast of four fundamental emotions: disgust, happiness, sadness, and surprise. AlexNet’s performance is enhanced by the SGD optimizer, whereas RMSprop improves LeNet’s performance. Results showed that AlexNet with SGD optimizer provides 93.00% recognition accuracy