CSNDSP 2006Iran Telecommunication Research Center1 Flat Fading Modeling in Fixed Microwave Radio Links Based on ITU-R P Iran Telecommunication Research Center (ITRC) Mehrbod Mohajer, Ramin Khosravi, Mehrnoosh Khabiri

Iran Telecommunication Research Center ICEE Outlines  Introduction  Outage Calculation  Fading Prediction in ITU-R P  Simulations  Conclusion

Iran Telecommunication Research Center ICEE Propagation Scenarios in LOS Point-to-Point Links Link Design

Iran Telecommunication Research Center ICEE What is the Problem?  In multi path situation, several rays with different delays and amplitudes are constructively or destructively added to the ray of direct or line-of-sight (LOS) path which introduce signal fluctuations.  If the signal falls below a certain point the link can be considered to be non functioning. Outage

Iran Telecommunication Research Center ICEE What can we do about it?  We cannot possibly know all the details of the environment through which the signal propagates.  We need to take a statistical view of the behaviour of the received field strength.  It is necessary to model the fading effects in such a way that a reasonable fade margin is obtained to achieve acceptable outage time.  Regarding to PTP links are used as high-availability links in the backbone of networks, the model should have the detailed shape of low probability section of distribution.

Iran Telecommunication Research Center ICEE Which Model?  Traditionally, the well-known lognormal distribution is widely used in the fixed wireless system design procedure.  In order to evaluate the performance of high- availability links, a distribution fading model is required which can precisely present the deep fade depths probability distribution.  Conventional distributions can not provide the detailed shape of deep fade depths probability.  The ITU-R P model derived from empirical measurements can perform this task excellently.

Iran Telecommunication Research Center ICEE All Important Propagation Standards ITU-R P (2005) TIA-845: Radiowave Propagation ETSI: BRAN HIPERACCESS IEEE IEC Why ITU-R P ?

Iran Telecommunication Research Center ICEE Propagation Effects in ITU-R P.530 Fading Multi-Hop Links Rain Attenuation XPD Diffraction Distortion Variation in Angle of Arrival/Launch

Iran Telecommunication Research Center ICEE Outlines  Introduction  Outage Calculation  Fading Prediction in ITU-R P  Simulations  Conclusion

Iran Telecommunication Research Center ICEE Fade Margin Concept Transmitter 1 Receiver 1 Splitter Transmitter 2 Receiver 2 Output Power (Tx) Branching Losses waveguide Propagation Losses Antenna Gain Branching Losses Receiver threshold Value Fade Margin

Iran Telecommunication Research Center ICEE Outage Time t RSL Noise power threshold Fade Margin The real RSL value which varies in time due to fading processes. The RSL value for a path subject to Free-space and atmospheric attenuation only.

Iran Telecommunication Research Center ICEE Improving Outage Time t RSL Free-space and atmospheric losses. Noise power threshold Fade Margin  By increasing the fade margin, we can improve the outage time.

Iran Telecommunication Research Center ICEE Outlines  Introduction  Outage Calculation  Fading Prediction in ITU-R P  Simulations  Conclusion

Iran Telecommunication Research Center ICEE Fading Prediction in ITU-R P  Flat Fading Prediction  For Small Percentage of Time (Deep Fade Depths)  For All Percentage of Time (Shallow and Deep Fade Depths)  Selective Frequency Fading Prediction

Iran Telecommunication Research Center ICEE Flat Fading (Deep Fade Depth) Detailed Link Design ApplicationsQuick Planning Applications These relations were derived from multiple regressions on fading data for 251 links in various geo-climatic regions of the world with

Iran Telecommunication Research Center ICEE Flat Fading (Shallow and Deep Fade Depths) Detailed Link Design ApplicationsQuick Planning Applications Deep Fade Depths Shallow Fade Depths

Iran Telecommunication Research Center ICEE Outlines  Introduction  Outage Calculation  Fading Prediction in ITU-R P  Simulations  Conclusion

Iran Telecommunication Research Center ICEE Simulations Fade probability for ITU-R P and Lognormal models

Iran Telecommunication Research Center ICEE PDF of the ITU-R P model Deep fade depths probability Shallow fade depths probability

Iran Telecommunication Research Center ICEE Simulations BER of QPSK modulation with various channel models

Iran Telecommunication Research Center ICEE Conclusion  The outage calculation and fade margin concept are reviewed.  The prediction methods of multi-path fading are introduced based on ITU-R P standard.  The ITU-R P model is more accurate in comparison to the conventional models like Lognormal model.  It is shown that using the theoretical lognormal model instead of empirical ITU-R model will cause to overestimation or underestimation in link design calculations. Therefore, please use ITU-R P.530 model in your link design

Iran Telecommunication Research Center ICEE Any Question? Thanks For Being Such a Good Audience