Pathloss 4.0 & MW Link Planning Part 1

Copyright © 2007 Telefocal Asia Pte Ltd. All rights reserved.1


Agenda – Day One

Introduction

Microwave Link Planning

Process Flow Chart

DTM and Coordinate System

Pathloss 4.0

Summary Module

Terrain Data Module

Antenna Height Module

Network Module

Diffraction Module


Network Module

Worksheet Module

Diffraction Module

Reflection Module

Multipath Module

Applying Divesity and Protection

Agenda – Day Two


Design of Passive Repeaters

Interference Analysis

Protection and Diversity

Practicle use of Pathloss 4.0

Agenda – Day Three



Microwave Applications

Transmission

Cell Site / Base Station Interconnect

Long haul E1 / 45M / STM-1 transport

Local Wireless Links

Access

Next-to-last mile transport for LMDS, WiMAX, WIP

Backhaul from digital loop carrier & DSLAM

CLEC metropolitan wireless links

Architectures

Linear (tree & branch, hub & spoke)

Ring (unidirectional path switch ring, ATM, IP)

Hybrid SONET / Microwave


Microwave Transport

Requires line of site

Frequency bands

“Low frequency” = 2 - 11 GHz

“High frequency” = 13 - 38 GHz

Capacities range from 2 E1s to STM-1

Availability based on:

Distance

Terrain

Precipitation

Climate


How Far Can You Go ?

Practical limits governed by many factors:

Frequency

Climate

Propagation Anomalies

Terrain

Antenna Performance / Center Lines

Rainfall Rate (for high frequencies)

Radio Performance

These are weighed against your desired . . .

Availability Objectives


6 GHz (20-60 Km)

11 GHz (10-30 Km)

18/23 GHz (1-8 Km)

Longer paths may require space diversity receiversSome bands are limited to 2-16 E1 radios

How Far Can You Go?


30 40 50 60 70 80 90 100 120 140 160 180 200 240 300 MHz

3 4 5 6 7 8 9 10 12 14 16 18 20 24 30 GHz

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4

AM Marine

Short Wave - International Broadcast - Amateur

3 4 5 6 7 8 9 10 12 14 16 18 20 24 30 MHz

CB

26 28

VHF LOW Band FM VHF VHF TV 7-13

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 GHz

UHF UHF TV 14-69 GPS

Cellular GSM1800, GSM1900

Broadcasting

Land-Mobile

Aeronautical

Mobile telephony

Terrestrial Microwave

Satellite

Frequency Spectrum


4 GHz High capacity band (max STM-1) Satellite users hinder Good propagation

LL66 GGHHzz Best high capacity band (max STM-1) Some low capacity channels Excellent propagation

UU66 GGHHzz Best low-mid capacity band (max STM-1) Very good propagation

10 GHz Low capacity band (max STM-1) Low congestion Adverse rain impact begins

What bands to use?


11 GHz High capacity band (max STM-1) Some low-cap channels Adverse rain impact

18 GHz Low-medium capacity band (max STM-1) Small antennas More adverse rain impact Satellite users growing encroachment

23 GHz Low-medium capacity band (max STM-1) Small antennas More adverse rain impact Shared with govt. users

What bands to use?


How Far Can You Go?

Below 8 GHz

Minimal influence

Above 8 GHz

Rain begins to dominate

Long paths may be practical up to 12 GHz

But only in dryer regions

The higher the frequency . . .

The more significant the impact


Good

AverageModerateDifficultVery Difficult

Average

Good

AverageAverage

Difficult

Difficult

Good

Difficult

Based on Bellcore c Factors

Very Difficult

Good

Propagation Regions


Basic Propagation Losses

Basic Propagation Losses fall into eight well defined categories:

Free-Space Propagation Loss - Basic transmission loss between two points in free space, each using an isotropic antenna.

Atmospheric Absorption - Absorption of EM energy by the oxygen and water molecules in the atmosphere. Above ~ 8 GHz.

Reflection Loss/Gain - Out of phase signals can cause 35-40 dB of attenuation, in phase can give 6 dB up fades.

Rain Attenuation - Significant only above 8 GHz..

Diffraction Loss - Losses caused by insufficient clearance over intermediate terrain features

Airborne Particles - Sand and dust only above ~ 14 GHz.

Fog and Clouds - Problem only above ~ 20 GHz.


Super refractive

Propagation Anomalies

Ducting

Subrefractive


Path Clearance

Two factors are involved

The K factor

Fresnel zones

The K factor

Describes the effective curvature of the earthRelative to air density vs. elevationInfluenced by pressure, temp and humidity

Fresnel zones

Describe the minimum clearance required for a microwave beam to travel as if through free space (i.e. a vacuum)


Atmospheric Propagation

Microwaves travel a straight line in free space

If a microwave beam is launched in free space (a vacuum) it will travel in a straight line.

The atmosphere is not free space

Vertical density gradients within the atmosphere cause a microwave signal to be curved

The density gradients are a function of air pressure, temperature, and humidity.


Class Work.

Assignment:

D= 20km

D1= 14.5km

D2= 5.5km

Antenna Hight = 30meter

Obstacle Hight = 18meter

Freq = 18 GHz

Find the First fresnel Zone and Check the Fresnel clearance


The Microwave Link ?

Microwave radio link, in the context of this course, refers to point-to-point fixed links that operate in duplex mode.

In its simplest form the microwave link can be one hop, consisting of one pair of antennas spaced as little as one or two kilometers apart, or can be a backbone, including multiple hops, spanning several thousand kilometers.


Terminal “A”

RadioMultiplex

Tx

Rx

RadioMultiplex

Tx

Rx

Terminal “B”

Antenna

Path

FeederData Data

Antenna

Feeder

The Microwave Link (Cont’d)

The above drawing is functional block diagram of a typical microwave link consisting of set of multiplexers, digital microwave radios, antennas and transmission lines.


• Sometimes radios are configured as outdoor units ( ODU ) and in this case transmission lines are not required and antennas are integrated as part of the radio RF head units. In GSM deployments where roll outs are quick, this is a very desirable feature.

• The fundamental aim of a microwave radio link is to deliver sufficient signal power to the radio at the far end of the link to achieve desired performance objectives. This is the challenge of link planning.

• For proper operation a microwave link must fulfill LOS condition.



Unfortunately, atmospheric conditions and rain effect modify the propagation of microwaves so that even if the link planner can see from point A to point B ( true LOS ), it may not be possible to place antennas at those two points and achieve a satisfactory communication performance.

A valuable characteristic of LOS transmission is that we can predict the level of a signal arriving at a distant receiver with known accuracy under non fading conditions. ( The link budget method ).

Microwave link performance and availability are predicted using a number of empirical prediction models.

For different frequency bands, capacities and under different propagation conditions, microwave link distances vary.



General design considerations:

Specifications of the network and system

Preliminary map study and site locations

Field survey and site survey

Preparation of path profiles

Determination of antenna heights

Ground-reflection calculations

Performance and availability predictions

Frequency planning

Equipment selection

Grounding and safety considerations

Microwave Link Planning


The Planning Process Teams

System Engineer

LOS Survey Team

Transmission Engineer

Site Acquisition Team

Network User: Fixed, Mobile, Utility, TV, PMP


Field Survey shall include:

• Verify exact site coordinates• Confirmation of LOS• Check-up of suspected reflection points,vegetation

buildings and other man made obstacles• Determination of height of, and distance to critical obstacles• Check propagation conditions• Classify Path types• Site survey

Field Survey and Site Determination


Survey Report

This report can include the following :

• Confirmation of LOS indicating equipment used for accuracy

• Site description and layout

• Antenna and tower heights

• Path Classifications ( overland paths, coastal links or water paths )

• Path elevations, coordinates, heights of obstructions and vegetations

• Propagation conditions

• Frequency interference probabilities

• Photographs


Digital Terrian Models (DTM)

Digital Terrain Models

DTM is a simple digital representation of a portion of the earth’s surface.

DTM may be used as a digital model of any single-valued surface. e.g.

Geological horizons

Rainfall or pressure

Population density


Digital Terrian Models (DTM)

DTM Generation

Most DTM data are derived from three alternative sources

Ground surveys

Survey data may be input directly into computer systems.

DTM generated from survey data is very accurate.

Expensive and time consuming process.

Photogrammetricdata capture

Based on the stereoscopic interpretation of aerial photographs or satellite imagery.

Cartographic data sources

Deriving DTM from cartographic documents


Map Scales

A defined dimensional relationship between reality and the map (Robinson et al., 1995):

a) Verbal: “one cm represents ten kilometers”

b) Representative fraction: 1:10,000

c) Graphic scale:

d) Area scale: Represents square kilometers

5000 0 5000 1000 0 Me te rs


Calculate Map Scales

For example, if 2 cm on a map represents 1 km on the ground the scale would be 2 cm = 1 km, or...

Scale is “unitless” because it is a ratio.


Examples small vs. large scale

Small scale: 1:250,000

Large scale: 1:50,000


Coordinate systems

• A coordinate system is a reference system based on mathematical rules for specifying positions (locations) on the surface of the earth. The coordinate values can be spherical (latitude and longitude) or planar (such as Universal Transverse Mercator).

• A coordinate system is usually defined by a datum, ellipsoid and projection, and is specified in terms of units (e.g. degrees, meters).


Types of Coordinate Systems

Geographic coordinate system:Uses latitude and longitude for locating positions on the uniformly curved surface of the earth.

Rectangular/plane coordinate systems:Used to locate positions on a flat map.For example Universal Transverse Mercator (UTM)


Geographic Coordinate System

The Equator (latitude) and Prime Meridian (longitude) are the reference points. Usually Greenwich, England is the Prime Meridian.

The Cartographic Boundary Files, the Road Network Files and the representative points are disseminated in latitude/longitude coordinates.

Prime meridian

Equator


Decimal Degrees (DD)

Decimal degrees are similar to degrees/ minutes/seconds (DMS) except that minutes and seconds are expressed as decimal values.

Decimal degrees make digital storage of coordinates easier and computations faster.

60.34444 instead of 60º20'40"


Example: Converting DMS to DD

20 minutes.= 0.33333 (20/60)40 seconds = 0.01111 (40/3600)

Add up the degrees to get an answer:60º + 0.33333 + 0.01111=60.34444 DD

60º20'40"degrees

minutes

seconds



Introduction

The following Slides outlines the method of use and the parameters to be used when planning a transmission link

In order for a link to operate reliably and provide the quality of service required for the transmission of data the recommendations outlined in ITU –R.F1491 for quality of service and ITU-R.F1493 for availability of service are used as guide lines


Necessary Data for Microwave Network Design& How to place it in your PATHLOSS Program

Pathloss 4.0 (licensed)

Rain File This folder contents Rain data for each area of the world according to 4 standards (Canada, Crane, Crane_96 & ITU)

Equipment File

Terrain Data File (GTOPO303)


Rain File

ITU World Rain Regions The ITU rain region are from A to Q are based on Characterstics of precipation for propagation Modeliong Recommendation ITU-R Pn.837-1

A world Map showing the ITU rain region is given on Figure


Rain File

This data will automatically placed in Pathloss Folder after program set up


Equipment

This folder contents 4 folders but for our Microwave design we just use 2 folders as the followings

MAS which contents Microwave Antenna Data for different Antenna Manufacturer (Andrew , RFS , ERICSSON , …………..) as shown in Figure

MRS which contents Microwave Radio Data for different Manufacturer


Equipment

Equipment Folder is available on Pathloss CD and can be download from Pathloss Website


Terrain Data File (GTOPO303)

This folder contents the Terrain data for all the world

WARNINGThis data is not accurate so we usually get terrain data from contours maps or from

path survey.

Just we use this data for reference

So it isn't allowed to use this data to create path profile

How to set this data?

Create new folder in your PATHLOSS folder & name it as Gopo30303

Copy inside it the necessary area files (each area has 2 files)

Run PathLoss program

Go to configure menu & click terrain database as shown in fig.

Set Primary (No Selection) & Secondary (GTopo30 Global 30sec) as shown in Fig.

Click Set Up Secondary – Set Directory – choose Gtopo30303 folder then kick OK – click Close – click OK as shown in Fig.


Terrain Data File


How to operate PATHLOSS

PATHLOSS program is full Microwave Network design software. For our work we shall use PATHLOSS for the following

Make Network Configuration

Make Path Profile to find antenna height in each station

Calculate Link Budget to find Antenna diameters , RX level & Link Availability

Frequency Plan for overall network

Frequency Interference calculations for overall network


Setting up Pathloss 4

Before PL4 can be used certain parameters need to be set up.

When the program is first launched the Summary Module will open.

In the Summary Module select the Configure dropdown tag


Geographic defaults

Click on Geographic Defaults and the Geographic Defaults setup box will be displayed. Set up the parameters applicable to your region.


Terrain Database

If you are using a DTM for profile generation then set up the terrain database as described, if not omit this step.

Reselect the Configure dropdown menu and select Terrain Database. The e Configure Terrain Database dialog box will appear. Set the Primary Data Base for your DTM from the dropdown box.

Next select Setup Primary and from the dialog box choose Set Directory and configure the path to the directory where the DTM is stored.

If the DTM requires an index table follow the steps below, if not omit them.

Once this has been completed select Index in the same dialog box. When the Index Screen appears select Files, and then select Import List. The index list will be imported, but you will need to fill in the UTM Zone numbers. The zone numbers are attached at the end of this document, UTM Index File.


Directories

Close all open dialog boxes and reselect the Configure dropdown menu and select Directories

Chose Microwave Antenna Codes and set up the path for the program to locate the directory containing the Antenna Files.

Repeat the process for Microwave radio Codes.

PL4 is now set up for use. Next we will discuss the various modules to be used.


Modules

PL 4 is divided into a number of modules each module is used to plan different parts of the link or transmission network. Only the basic functions of the modules required for transmission planning are discussed in this document.

Summary Module

Terrain Data Module


Work Sheet Module

Diffraction Module

Reflections Module

Multipath Module

Print Profile Module

Network Module


Summary Module


Summary Module

Site Names - enter an abbreviated name code.

Call Sign – enter the site call sign code. This code is used when performing interference calculations.

Station Code – enter the station code if available or leave blank.

Owner Code – enter the owner code if available or leave blank.

Latitude – make sure that the same latitude is entered for the same site each time this field in filled in.

Longitude – make sure that the same longitude is entered for the same site each time this field in filled in.

Tower heights – enter the height of the towers on each site.

Operator Code – enter the operator code if available or leave blank.

Frequency (MHz) – enter the frequency band the link will operate in e.g. 7500 or 15000.

Selecting the Report tag can generate a report of the Summary Module.


Terrain Data Module

From the Modules dropdown menu select Terrain Data and the Terrain Data Worksheet will be displayed. It is assumed that a DTM will be used to enter the terrain data. If it is not available the data will have to be recorded using a 1:50,000 map and entered into the module manually.


Terrain Data Module (Cont’d): Generate Profile

Select the Operations dropdown menu and choose Generate Profile, tick the Span Missing Files box and click Generate

Close the Generate Profile dialog box. The DTM records data points every 200 meters and there will be a number of points indicating the same ground elevation. These duplicated data points are not required for the accuracy of the profile so they can be deleted.

Select the Operation dropdown menu and choose Strip Redundant Points. Set the tolerance to 0 and click OK. Next reselect the Operations dropdown menu and Accept-Reject Changes. Choose

Yes when the Delete Marked Point dialog box opens.


Terrain Data Module (Cont’d): Ground Clutter

Ground clutter can be added to the profile in the form of trees, buildings, water towers and off path obstructions. Double click in the Structure Field of the display and select the type of structure you wish to insert. In the structure dialog box enter the structure information.

If a range of 25 meters high tress had been inserted on to the profile the following dialog boxes would have been used and the profile will be as shown.


Terrain Data Module (Cont’d):

Selecting the Report tag at the top of the profile will generate a Report detailing the terrain data.



PL4 is able to calculate antenna heights for various combinations of antennas. The combinations most commonly used are Single antennas per site, TR-TR and space diversity antennas using two antennas per site, TRDR-TRDR.

From the Module dropdown menu select Antenna Heights. The screen below displayed the Antenna Height information for a diversity link


Calculating Kmin

In order to calculate the antenna heights we need to know what the Kmin value for the link.

To do this select the Operations dropdown menu and select Minimum K.

Record the calculated value.


Set Clearance Criteria

Next reselect the Operations dropdown menu and choose Set Clearance Criteria and enter the recorded value of Kmin in the dialog box for the 2nd Criteria – K and set the 2nd Criteria - %F1 to 60.

If space diversity is used enter the following - under the Diversity Option enter 1.333 for 1st Criteria – K and set the 1st Criteria - %F1 to 30. This is in accordance with the ITU recommendations for diversity link operations. If a non-diversity path is being planned then the Diversity criteria are left blank.


Calculate Antenna Heights

Press F9 to calculate the main antenna heights. Press F7 to change the calculation to the Diversity Path, if used, and press F9 again. The calculated antenna heights will be displayed in boxes at the top of the screen.

Click in one of the Antenna Height boxes and the Microwave Antenna Heights dialog box will be displayed

Adjust the antenna heights to the nearest metre to the calculated antenna heights. Diversity antenna heights are normally set 200 wavelengths below the main antenna, in a 7,500 MHz link this is approximately 8 metres. Diversity antennas can be set further apart from the main antenna to combat multipath or ducting, but these greater distances will not improve the link quality significantly, but will improve the link availability.

The antenna height calculations are similar for non diversity links, only the diversity calculation is omitted.


Print Profile Module

Select Module – Print Profile and the profile to be printed will be displayed. Three formats of display are available:

Flat Earth Drawn using multiple K values Curved Earth Straight Axis Only drawn for a single K value Curved Earth Curved Axis Only drawn for a single K value The profile below is an example of the Flat Earth Display.


Print Profile Module (Cont’d)

The various display options are selected by Clicking on Format and then selecting an option from the dropdown menu.

The profile Title Block can also be selected from this menu, this provides information about the link including the initials of the person planning the link as well as drawing number. This information should be included with each profile.

Documents

Pathloss 4.0 & MW Link Planning Part 1