- 1. By- Dr. Jesmin Akhter Professor Institute of Information Technology Jahangirnagar University Wireless and Mobile Communication ICT-4203
- 2. Fading Distributions • Describes how the received signal amplitude changes with time. • Remember that the received signal is combination of multiple signals arriving from different directions, phases and amplitudes. • With the received signal we mean the baseband signal, namely the envelope of the received signal (i.e. r(t)). (The envelope of an oscillating signal is a smooth curve outlining its extremes) • Fading Distribution is a statistical characterization of the multipath fading. This fading characteristics of a mobile radio signal are described by the following three statistical distributions - • Rician Distribution • Rayleigh Distribution • Lognormal Distribution
- 3. Rayleigh Distributions • Describes the received signal envelope distribution for channels, where all the components are non-LOS: • i.e. there is no line-of–sight (LOS) component.
- 4. Rayleigh Fading Distribution • The Rayleigh distribution is commonly used to describe the statistical time varying nature of the received envelope of a flat fading signal, or the envelope of an individual multipath component. • The Rayleigh distribution is given as: • is the rms value of the received voltage before envelope detection, 2 is the time-average power/local average power of the received signal before envelope detection and r2 is instantaneous power. p r r r r r ( ) exp( ) 2 2 2 2 0 0 0
- 5. Ricean Distributions • Describes the received signal envelope distribution for channels where one of the multipath components is LOS component. • i.e. there is one LOS component.
- 6. Ricean Fading Distribution • When there is a dominant stationary signal component present, the small-scale fading envelope distribution is Ricean. The effect of a dominant signal arriving with many weaker multipath signals gives rise to the Ricean distribution. • The Ricean distribution degenerates to a Rayleigh distribution when the dominant component fades away. • The Ricean distribution is often described in terms of a parameter K which is defined as the ratio between the deterministic signal power and the variance of the multipath. • K is known as the Ricean factor • As A0, K - dB, Ricean distribution degenerates to Rayleigh distribution. 0 0 0 , 0 ) ( ] 2 ) ( exp[ ) ( 2 0 2 2 2 2 r A r Ar I A r r r p K A 2 2 2
- 7. PDF • Probability density function of Ricean distributions: K=-∞dB (Rayleigh) and K=6dB. For K>>1, the Ricean pdf is approximately Gaussian about the mean.
- 9. • Propagation path-loss models play an important role in the design of cellular systems to specify key system parameters such as transmission power, frequency, antenna heights, and so on. • Several models have been proposed for cellular systems operating in different environments (indoor, outdoor, urban, suburban, rural). • Okumura Model • Hata Model • Cost 231 Model Propagation Path-Loss Models
- 10. • The Okumura model is a Radio propagation model that was built using the data collected in the city of Tokyo, Japan. • The model is ideal for using in cities with many urban structures but not many tall blocking structures. • The model served as a base for the Hata Model. • Okumura model was built into three modes. • Urban, suburban and open areas. • The model for urban areas was built first and used as the base for others. Okumura model
- 11. 50% of measured values lie above this threshold and 50% of measured values lie below this threshold value
- 18. Thank You

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