Ali K. Lwas

Comparison of empirical propagation path loss models for mobile communications in the suburban area of Kuala Lumpur

The empirical propagation path loss models have important influence in mobile communication systems design. They become important tools in both research and industrial communities owing to their speed of implementation and their limited dependence on detailed knowledge of the terrain. The mobile services are increasing rapidly and hence the mobile stations are required to design with best quality of service. Path loss models are considered frequently to estimate power budgets and cell coverages. Four empirical models namely, the Lee model, the Stanford University Interim (SUI) model, the COST-231 Hata model and Egli model have been investigated in this work. The measurements were carried out at University Putra Malaysia (UPM) campus and Gombak area. The measured data is used to validate the applicability of the four models mentioned previously in suburban environments. The results show that Egli model, COST-231 Hata model and SUI model over-predict the path loss in all coverage areas. The Lee model shows the best performance to the measured path loss.

Rain attenuation analysis using synthetic storm technique in Malaysia

Generated rain attenuation time series plays an important role for investigating the rain fade characteristics in the lack of real fade measurements. A suitable conversion technique can be applied to measured rain rate time series to produce rain attenuation data and be utilized to understand the rain fade characteristics. This paper focuses on applicability of synthetic storm technique (SST) to convert measured rain rate data to rain attenuation time series. Its performance is assessed for time series generation over a tropical location Kuala Lumpur, in Malaysia. From preliminary analysis, it is found that SST gives satisfactory results to estimate the rain attenuation time series from the rain rate measurements over this region.

Analysis of Synthetic Storm Technique Based on Ku-Band Satellite Beacon Measurements in Malaysia

Most of the existing rain attenuation prediction models were proposed based on measurements taken in temperate climates. These models are found not accurate in tropical regions and were thus modified in order for such models to be applied in tropical regions. Synthetic Storm Technique (SST) is one of the most reliable methods to estimate rain attenuation time series in Europe. However, due to the lack of measured data in the tropical regions of the world, the above-mentioned method is yet to be validated for those regions. This paper aims to investigate SST validity in Malaysia by focusing on both rain events and the overall statistical behavior. Its performance is assessed based on concurrent measurement of Ku-band satellite beacon and rain rate over University of Science Malaysia (USM) campus at Tronoh. Preliminary analysis shows that SST is capable of providing details of time-series of many rain events to reflect the dynamics of rain fade. However, it is unable to predict the entire range of rain intensity.

Analysis of the Synthetic Storm Technique Using Rain Height Models to Predict Rain Attenuation in Tropical Regions

This paper aims to investigate the utilization of the Synthetic Storm Technique (SST) to convert rain rate time series to rain attenuation time series using the ITU-R P.839, Stutz man and Bryant rain height models. Furthermore, the study aims to compare the actual rain attenuation with that predicted by the SST using the three above-mentioned rain height models based on rain rate and rain attenuation both measured concurrently. The study relies on rain rate time series and rain attenuation time series measured at University Science Malaysia (USM) campus (4.390 N, 100.980 E). The study found that the higher the rain rate, the higher is the percentage error for the SST predicated rain attenuation using the three above-mentioned rain height models as compared with measured rain attenuation. However, it is observed that when the Stutz man model applied as part of the SST model, the prediction is more accurate of the three rain height models.

Characterization of indoor propagation for three dimensional femtocell environment

Femtocell gains the interest of more than 160 mobile operators around the world. For the reason that femtocell improve the signal power inside the building and reduce the main network traffic and thus increase the capacity. However, deployment the femtocell may cause interference to the existing network. Therefore, understanding the behavior of indoor signal propagation is essential to minimize the interference and get the total benefit of femtocell deployment. In this paper, measurements of the signal strength at 2.6 GHz were carried out for three dimensional scenario using Omni-directional antenna. The line of sight and none of sight cases were considered in the proposed scenario. These measurements are important in order to propose an empirical model for indoor propagation that may be used in system level simulators. In addition, a comparison with available models for indoor propagation was conducted. It was found that the available models in the literature are underestimated the measured data.

Rain fade mitigation on earth-to-satellite microwave links using site diversity

Rain is the major challenge to design reliable earth to satellite microwave link at higher frequencies in tropical regions. Site diversity is one of the techniques used to mitigate this problem. Hodge and ITU-R Site Diversity Gain Models and ITU-R Diversity Improvement Factor Model are analyzed based on measurements at two locations in Malaysia. The measured rain intensity at IIUM and UKM campus for six months period with 1 minute integration time was used to predict attenuation with MEASAT3A as reference satellite. Two locations are separated by 37.36 Km distance. The measured site diversity gain and improvement factor are compared with predicted values. It is found that highly available satellite links can be achieved through site diversity.