PCS Extension to Hata Model, Walfisch Bertoni Model, Indoor Propagation and Partition Losses

Instructor: Dr. Mustafa Shakir

PCS Extension to Hata Model PCS Extension to Hata Model Euorpean

Cooperative for Scientific and Technical Research (EURO-COST)

Walfisch and Bertoni Model Walfisch and Bertoni considers the impact of rooftops

and building height by using diffraction to predict average signal strength at street level

P0 represents the free space loss

P1 is based upon diffraction and determines the signal loss from the rooftop to the street

Q2 gives the reduction in the rooftop signal due to the row of the buildings which immediately shadow thereceiver at street level

The pathloss S as product of three fators

Indoor PropagationIndoor channels are different from traditional mobile radio

channels in two different ways: The distances covered are much smaller The variablity of the environment is much greater for a

much smaller range of T-R separation distances. The propagation inside a building is influenced by: Layout of the building Construction materials Building type: sports arena, residential home,

factory,...

Microcells Models Smaller cells for increased capacity

Base station height is typically about that as lamp posts in a street(3-6 m above ground level)

Coverage is typically few hundred meters and is determined mostly by specific locations and electrical characteristics of surrounding buildings

Dominant propagation mechanisms are: Free space propagation + multiple reflection+ scattering+ diffraction

around vertical edges of buildings and rooftops

Indoor Propagation Indoor propagation is domited by the same

mechanisms as outdoor: reflection, scattering, diffraction.

--However, conditions are much more variable Doors/windows open or not

The mounting place of antenna: desk, ceiling, etc. The level of floors Indoor channels are classified as Line-of-sight (LOS) Obstructed (OBS) with varying degrees of clutter.

Indoor Propagation Buiding types Residential homes in suburban areas Residential homes in urban areas Traditional office buildings with fixed walls (hard partitions) Open plan buildings with movable wall panels (soft

partitions) Factory buildings Grocery stores Retail stores Sport arenas

Indoor propagation events and parameters

Temporal fading for fixed and moving terminals Motion of people inside building causes Ricean Fading for the stationary

receivers Portable receivers experience in general:

Rayleigh fading for OBS propagation paths Ricean fading for LOS paths.

Multipath Delay Spread Buildings with fewer metals and hard-partitions typically have small rms

delay spreads: 30-60ns.

---Can support data rates excess of several Mbps without equalization Larger buildings with great amount of metal and open aisles may have rms

delay spreads as large as 300ns.

---Can not support data rates more than a few hundred Kbps without equalization.

Path Loss The following formula that we have seen earlier also describes the indoor path

loss:

-- PL(d)[dBm] = PL(d0) + 10nlog(d/d0) + Xs

>>n and s depend on the type of the building

>>Smaller value for s indicates the accuracy of the path loss model.

Partition Losses In building path loss:Partition losses (same

floor) Partition losses between floors Signal Penetration into Buildings

There are two kind of partition at the same floor:

Hard partions: the walls of the rooms Soft partitions: moveable partitions that does

not span to the ceiling The path loss depends on the type of the partitions

Partitions vary widely in physical and electrical characteristics making it difficult to apply general models to indoor installations specifically.

Introduction-Fading

One of the most interesting applications of radio communications, that is communication between mobile people, has many impairments.

Due to multiple users, mobility and environment dynamics, the mobile radio channel is impaired by noise, interference as well as time-varying fluctuations

System design requires statistical characterization of both disturbances and random channel space/time variations

Envelope variations are due to phenomena on different spatial/temporal

Wireless Propagation Environment

Multipath Effects Rapid changes in signal strength over a small travel distance or time

interval

Random frequency/phase modulation due to Doppler shifts on different multipath signals

Time dispersion caused by multipath propagation delays

Impulse Response Model of a Multipath Channel

A mobile radio channel may be modeled as a linear filter with a time varying impulse response, where the time variation is due to receiver motion in space.

The filtering nature of the channel is caused by the summation of amplitudes and delays of the multiple arriving waves at any instant of time.

Channel Impulse Response

Due to the different multipath waves which have propagation delays which vary over different spatial locations of the receiver, the impulse response of the linear time invariant channel should be a function of the position of the receiver.

Multipath Radio Channel