Seasonal and Diurnal Variation on Tropospheric Scintillation at Ku-Band in Tropical Climate

Tropospheric scintillation is a rapid fluctuation of the received signal amplitude which can cause propagation impairments that affect satellite communication systems operating above 10 GHz. Scintillation data was collected in Equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement campaign, utilizing MEASAT-1 Satellite with an antenna elevation angle of 75.61°. This work concentrates on the probability density function (PDF) of diurnal variations of clear sky scintillation variance analyzed on an hourly basis. Besides, seasonal variation of scintillation amplitude has been presented in this paper. From the results, it is concluded that clear sky scintillation variance is likely to occur during morning and afternoon periods. Moreover, clear sky scintillation amplitude of the South-West monsoon shows a relatively higher comparing with others monsoon seasons. Hence, signal attenuation based on seasonal and diurnal information is of great interest for the system designers to appropriately design fade margin.Tropospheric scintillation is a rapid fluctuation of the received signal amplitude which can cause propagation impairments that affect satellite communication systems operating above 10 GHz. Scintillation data was collected in Equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement campaign, utilizing MEASAT-1 Satellite with an antenna elevation angle of 75.61°. This work concentrates on the probability density function (PDF) of diurnal variations of clear sky scintillation variance analyzed on an hourly basis. Besides, seasonal variation of scintillation amplitude has been presented in this paper. From the results, it is concluded that clear sky scintillation variance is likely to occur during morning and afternoon periods. Moreover, clear sky scintillation amplitude of the South-West monsoon shows a relatively higher comparing with others monsoon seasons. Hence, signal attenuation based on seasonal and diurnal information is of great interest for the system designers to appropriately design fade margin

Disparities in the induced rain attenuation between beacon (narrowband) and broadband satellite links in tropical zones

The utilisation of higher frequency bands above 10 GHz by the satellite industries to provide the bandwidth (BW) required for broadband multimedia services, video conferencing, direct-to-home TV programmes and IP data requires the understanding of atmospheric losses and good link planning for satellite-to-earth links. The trade-off between the service availability, data rate and BW determine the type of modulation scheme and error corrections to be employed. These services also depend on the link performance under adverse atmospheric conditions, especially rain-induced attenuation. In this research, study measurements were conducted on space-to-earth satellite links using the beacon narrowband and broadband IP carrier signals of a Nigcomsat-1R satellite operating at 42.5°E. A VSAT receiving terminal at a latitude of 7.4°N, longitude of 9.04°E and altitude of 334 m above sea level was utilised to quantify the rain-induced attenuation of both the beacon and broadband signals during rain events. The measurements were then compared with the link performance under clear sky conditions. The performance revealed that, when compared with the broadband signal, the induced rain attenuation on beacon signal presented a disparity in the responses, resulting in significant variations of 10.14 dB in the carrier-tonoise ratio (C/N) and 17.42 dB in the received signal level at a Ku-band frequency of 12.518 GHz. These observations were also compared with the Crane global rain map and ITU-R P.618-12. Both models disagreed with the measurement values for Abuja, Nigeria

Comparison of Raindrop Size Distribution Characteristics Across the Southeast Asia Region

Satellite communication requires reliable estimates of the channel characteristics, especially with the future use of higher frequencies. Regardless of the rain rate, the shape of rain drop size distribution (DSD) start to considerably effect the specific attenuation. In this study DSDs are studied using ground-based two-dimensional video disdrometer measurements taken from Johor, Malaysia as well as two similar datasets from Gan and Manus, two equatorial islands. Integral rain parameters are studied to explain DSD variations across the Southeast Asia region. Slightly higher raindrop concentrations and larger diameters were observed in Johor than in Gan or Manus, which is due to Johor being affected by not only oceanic rain- fall but land rainfall as well. The measured rainfall was classified into convective and stratiform precipitation types; the results showed that the Southeast Asia region is dominated by convective rain in terms of accumulated rainfall amount, but stratiform rain occurred more frequently. Further, seasonal variations observed in Johor were insignificant and the DSD variation was mostly due to changes in percentage occurrence of the precipitation types for each monsoon season

A Mathematical Approach for Hidden Node Problem in Cognitive Radio Networks

Cognitive radio (CR) technology has emerged as a realistic solution to the spectrum scarcity problem in present day wireless networks. A major challenge in CR radio networks is the hidden node problem, which is the inability of the CR nodes to detect the primary user. This paper proposes energy detector-based distributed sequential cooperative spectrum sensing over Nakagami-m fading, as a tool to solve the hidden node problem. The derivation of energy detection performance over Nakagami-m fading channel is presented. Since the observation represents a random variable, likelihood ratio test (LRT) is known to be optimal in this type of detection problem. The LRT is implemented using the Neyman-Pearson Criterion (maximizing the probability of detection but at a constraint of false alarm probability). The performance of the proposed method has been evaluated both by numerical analysis and simulations. The effect of cooperation among a group of CR nodes and system parameters such as SNR, detection threshold and number of samples per CR nodes is investigated. Results show improved detection performance by implementing the proposed model

Spatial variations of rain intensity over a short length propagation for 5G links based on a rain gauge network

Millimeter-wave (mm-wave) frequency range is among operating bands designated for terrestrial 5G networks. A critical challenge of link-budgeting in mm-wave 5G networks is the precise estimation of rain attenuation for short-path links. The difficulties are further amplified in tropical and subtropical regions where the rainfall rate has a higher intensity. Different models have been proposed to predict rain attenuation. The distance factor is an important parameter in predicting total attenuation from specific rain attenuation. This study investigates the distance factor based on rain gauge networks and measured rain attenuation at 26 GHz for a 300 m link in Malaysia. Considerable discrepancies between available models were observed especially when applied for shorter path links. Also, significant variability of rain intensity is observed from the rain gauge network. This study recommends further investigation of the distance factor for a shorter link. Hence, a measurement campaign incorporating rain gauge networks was established to examine spatial variations of rain intensity over a less than 1 km link. The motivation is to develop a suitable distance factor model for 5G mm-wave propagation

Disparities in the induced rain attenuation between beacon (Narrowband) and broadband satellite links in tropical zones

The utilisation of higher frequency bands above 10 GHz by the satellite industries to provide the bandwidth (BW) required for broadband multimedia services, video conferencing, direct-to-home TV programmes and IP data requires the understanding of atmospheric losses and good link planning for satellite-to-earth links. The trade-off between the service availability, data rate and BW determine the type of modulation scheme and error corrections to be employed. These services also depend on the link performance under adverse atmospheric conditions, especially rain-induced attenuation. In this research, study measurements were conducted on space-to-earth satellite links using the beacon narrowband and broadband IP carrier signals of a Nigcomsat-1R satellite operating at 42.5°E. A VSAT receiving terminal at a latitude of 7.4°N, longitude of 9.04°E and altitude of 334 m above sea level was utilised to quantify the rain-induced attenuation of both the beacon and broadband signals during rain events. The measurements were then compared with the link performance under clear sky conditions. The performance revealed that, when compared with the broadband signal, the induced rain attenuation on beacon signal presented a disparity in the responses, resulting in significant variations of 10.14 dB in the carrier-to-noise ratio (C/N) and 17.42 dB in the received signal level at a Ku-band frequency of 12.518 GHz. These observations were also compared with the Crane global rain map and ITU-R P.618-12. Both models disagreed with the measurement values for Abuja, Nigeria

Interfade Duration Statistics at Ku-band for Satellite Earth Links System in Equatorial Malaysia: Modeling Distribution

 Fade dynamics is one of more important parameters when implementing Fade Mitigation Techniques (FMTs) to counteract an excessive attenuation that affect satellite communication systems operating above 10 GHz. The statistics of probable duration between two rain fade namely interfade duration enables system operator to estimate how long the system will need to recover before the next outage and assist in designing the FMTs. In this paper, interfade duration statistics have been derived from one year of slant path attenuation measurements data collected in Equatorial Johor Bahru at 12.2 GHz with elevation angle of 75.61o. The result had shown the dependency of number of events with attenuation thresholds. Empirical interfade duration statistics are also obtained and suitable model distribution are proposed.

A methodology for precise estimation of rain attenuation on terrestrial millimetre wave links from raindrop size distribution measurements

Attenuation by atmospheric rain is the most significant impairment in millimetre wave frequencies (mmWave). Modern instruments could provide detailed measurements of rain, such as raindrop size distributions (DSDs). The analysis of DSDs could estimate their effects on past or co-located links measurements. This study presents propagation analysis in the mmWave bands using measurements of two terrestrial links working at 26 and 38 GHz carried out in Johor, Malaysia. Statistics obtained have been analysed in detail to extract any excess attenuation. The DSDs provided by a disdrometer have been used to estimate rain attenuation. The derived results show that the estimation can provide reasonable accuracy after extracting the wet antenna effects and having the advantage of the availability of measurements from various types of equipment

Rain attenuation statistics for mobile satellite communications estimated from radar measurements in Malaysia

Mobile satellite communications will play a significant role in the next 5th generation mobile services. The use of high-frequency bands will be the enabler of this advancement. However, at high frequencies, excess rain attenuation causes severe signal losses and presents a major threat for the system availability, especially in the tropical region. To that end, this study presents the rain attenuation impact on mobile satellite communications estimated using long-term radar measurements in Malaysia, by exploiting the horizontal structure of rain from the radar database and simulating inner-city and highway mobile terminals scenarios. Additionally, a scaling factor was presented to scale available fixed satellite terminals measurements to mobile terminals operating at the same locality under similar conditions. In comparison to the available link measurements, the radar database was reliable enough to provide highly accurate estimates. In all simulation scenarios, the mobile terminal will depart the rainy area soon enough and experience lower attenuation statistics in comparison with the fixed terminal. The provided results will help determine the overall future system performance, especially in tropical regions

Investigation of HAPs Propagation Channel for Wireless Access in a Tropical Region at Ka-Band

In the last few years, High Altitude Platforms (HAPs) have attracted considerable effort due to their ability to exploit the advantages of satellite and terrestrial-based systems. Rain attenuation is the most dominant atmospheric impairment, especially at such frequency band. This paper addresses the modelling of rain attenuation and describes a propagation channel model for HAPs at Ka-band to provide efficient and robust wireless access for tropical regions. The attenuation due to rain is modeled based on three years measured data for Johor Bahru to estimate the actual effect of rain on signals at Ka band. The radio propagation channel is usually characterized as a random multipath channel. Specifically, a statistical derivation of probability distribution function for Rayleigh and Rician fading channels are presented. The model consists of multiple path scattering effects, time dispersion, and Doppler shifts acting on the HAPs communication link. Simulation results represent the fading signal level variations. Results show perfect agreement between simulation and theoretical, thereby conforming to the multipath structures. The information obtained will be useful to system engineers for HAPs link budget analysis in order to obtain the required fade margin for optimal system performance in tropical regions