In this paper, the effect of rain attenuation on the FSS allocation in the 7250-7750 MHz in the Space-to-Earth direction is studied for a satellite at 78.5 • E longitude. A simulation model based on the ITU-R P618-10 rain model is used to predict the rain attenuation in the C-, Ku-and X-bands in 15 different locations with varying rainfall intensities of between 145-300 mm/hr in East and West Malaysia. The simulations assume a 1.8 m receive antenna with 65% aperture efficiency, QPSK modulation and use of either vertical or horizontal polarization. The downlink centre frequencies used in this study are 4200 MHz, 7750 MHz and 11200 MHz for C-, X-and Ku-bands respectively. The average free-space path loss calculated for each band is used to estimate the signal attenuation due to rain and the corresponding E b /N o (dB) is computed at varying rain intensities. The results show that when using vertical receive polarization, all 15 locations of study with a rainfall intensity of up to 200 mm/hr could receive the X-band signal. At 200 mm/hr rain intensity in the horizontal receive, most of the X-band links could achieve the threshold E b /N o of 7.68 dB with a ULPC adjustment of approximately 1.5 dB where required. At 300 mm/hr rain intensity, video signals in the X-band were no longer receivable in both polarizations. At 145 mm/hr rain intensity, only one location with high satellite elevation and greater height above mean sea level maintained the Ku-band link in the horizontal receive. In the vertical receive, the Ku-band link was receivable at all locations at 145 mm/hr but were no longer receivable at 200 mm/hr. The study concluded that the elevation angle towards the satellite is a major factor in determining the quality of the signal in the X-band. The other factors that affected the receive E b /N o was the polarization, depth of rain and height of the earth station above
In Malaysia, the incumbent WiMAX operator utilises the bands of 2360-2390MHz to provide broadband services. Like all Radio Frequency (RF), WiMAX is susceptible to path loss. In this paper, field strength data collected in Cyberjaya, Malaysia is used to calculate the path loss suffered by the WiMAX signals. The measured path loss is compared with the theoretical path loss values estimated by the COST-231 Hata model, the Stanford University Interim (SUI) model and the Egli model. The best model to estimate the path loss based on the path loss exponents was determined to be the COST-231 Hata model. From this observation, an optimised model based on COST-231 Hata parameters is developed to predict path loss for suburban and open urban environments in the 2360-2390MHz band. The optimised model is validated using standard deviation error analysis, and the results indicate that the new optimised model predicts path loss in both suburban and open urban environments with very low standard deviation errors of less than 4.3dB and 1.9dB respectively. These values show that the model optimisation was done successfully and that the new optimised models will be able to determine the path loss suffered by the WiMAX signals more accurately. The optimised model may be used by telecommunication providers to improve their service.
Abstract-Free space path loss modelling is a model used to model path loss propagation for Wireless Local Area Networks. In some cases, the estimation of path loss by the FSL model can be inaccurate as it does not take into account the effects of multipath propagation. The International Telecommunication Union Recommendation, ITU-R P.1411-7 provides prediction methods for the planning of short-range outdoor radio communication systems and radio local area networks in the frequency range of 300 MHz to 100 GHz. This recommendation further proposes a location variability correction, ρ, which models the standard deviation of field strength due to small scale fading. This paper investigates the feasibility of using the ITU-R P.1141-7 Recommendation to estimate the path loss for 802.11n signals experienced by pedestrians in a suburban environment. Received signal strengths were collected from field experiments, and the measured path loss was compared with estimated path loss values. The results show that for areas with high levels of small scale fading, the ITU-R P.1141-7 was able to estimate the path loss for IEEE 802.11n signals with a higher accuracy of 10 dB than the FSL model.
Underestimation of path loss when planning the deployment of 802.11n APs can lead to coverage gaps and user dissatisfaction. The use of Free Space Path Loss modelling can sometimes lead to underestimation of path loss in urban environments when the effect of small scale fading is not considered. A field experiment was conducted with the aim to investigate the applicability of the ITU-R P.1141-7 Recommendation in path loss estimation of 802.11n signals in an urban environment in Malaysia. The results showed that Section 4.3 of ITU-R P.1411-7 can estimate the path loss of 802.11n signals with very low error margins of between 0 dB and 5 dB for transmitter receiver distances of 50 m and more. At these distances, the average difference of path loss estimation between FSPL and measured path loss is approximately 18 dB. The study concludes that 802.11n APs may need to be placed at closer proximities than previously assumed if FSPL is used to model the path loss. This is to ensure that targeted traffic is actually offloaded; coverage gaps are reduced; user satisfaction is improved.
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