Pathloss 4.0 & MW Link Planning Part 3

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

Agenda

Design of Passive Repeaters

Interference Analysis

Protection and Diversity

Practicle use of Pathloss 4.0


Microwave Repeaters


Microwave Repeaters

Microwave repeaters can be classified as: Passive Repeaters RF Repeaters


Microwave Repeaters

WHY USE THEM ? When a microwave hop is required in a place

which has some unavoidable physical obstacles.

Where a mountain peak has to be surmounted which may be so inaccessible that power cannot be provided for a usual active repeater.


Passive Repeaters Types

There are two main types of Passive Repeaters:

Passive or plane reflectors Back-to-back antenna passives


Passive Repeaters Advantages

Passive repeaters have the following advantages over active sites: No power is required; No regular road access is required; No equipment housing is needed; They are environmentally friendly; Little or no maintenance is required.


Types of Passive Repeater Applications


Flat or Plane Passive Repeater: Pictorial View


Plane Passive Repeater Applications

Redirect microwave signals over an obstruction.

Plan ViewPlan View


Plane Passive Repeater Applications

Utilize the surrounding terrain to eliminate the need for tall antenna structures


Back-to-back antennas

Use of back-to-back antennas are practical when the reflection angle is

large. The gain of a repeater with back-to-back antennas is given by:

is the gain of one of the two antennas at the repeater in dBis the gain of the other antenna at the repeater in dBis the coupling loss ( waveguide, etc. ) between the antennas in dB


The Aloum to Lolodorf CRTV link has been used as an example in this document

Step 1:

The first step is to generate and save two path profiles and link budgets:

Profile 1 - Site 1(Aloum) to Passive (Lolodorf Passive)

Profile 2 - Passive (Lolodorf Passive) to Site 2 (Lolodorf CRTV)

The passive repeater site has to have the same co-ordinates and elevation in both profiles.

When entering the frequency for the second path profile use the same frequency and Hi/Lo configuration as the first profile but change the polarisation.

It is not necessary to enter the microwave terminal equipment for the passive repeater site as they are not used in the final link budget. It is advisable to enter the antenna information for the passive repeater site as this will provide a link budget starting point when optimising the link performance.

Creating Passive Repeater using Pathloss 4


Step 2:Open Profile 1 (Aloum-Lolodorf Passive) in the Worksheet section of PL4.

Profile 1 Aloum to Lolodorf Passive



Step 3:1. Click on the Operations tab and select Create Passive Repeater.

Selecting Create Passive Repeater



2. Next select the type of passive repeater to be created Back-to-Back Antennas

Selecting Back-to-Back Antennas



3. Select Profile 2 (Lolodorf Passive-Lolodorf CRTV.pl4) from the list of profiles

Selecting Profile 2



Passive Repeater Profile Aloum-Lolodorf Passive-Lolodorf CRTV

The second profile will be joined to the first and the passive repeater site indicated. Save the new profile under a name indicting that it is a passive repeater profile (Aloum-Lolodorf Passive-Lolodorf CRTV.pl4).



Step 4:The connection between the two passive antennas has to be made. Click on the P symbol to open the Passive Repeater information and enter the cable information

The Passive Repeater Information Form



Step 5:Adjust the antenna sizes, TX power outputs etc. to ensure that the link budget meets the performance requirements for the link.

Once satisfied with the results save the profile.

Reports:Two reports need to be generated for the passive repeater link:

1. The Full Report – this provides the configuration and performance information of the complete link, but excludes the passive repeater site.

2. The passive repeater report – this provides configuration information on the passive repeater site.



Full report:Select Reports – Full Report from the menu at the top of the page

Selecting the Full Report



The full link report will be generated:





Passive repeater report:Select Reports – Passive from the menu at the top of the page

Selecting the Passive Repeater Report



The Passive Repeater Report



Section 8B: Interference


Introduction

Any unwanted signal Copy of wanted signal delayed due to

multipath propagation An adjacent channel’s signal traveling over

the same link A signal from another radio link or RF source


Interference Classes

There are two interference classes:

Between the same system ( Intra System Case): Controllable

Between different systems ( Inter System Case): Un controllable


IntrasystemThis type of interference is caused by an undesired signal generated within the system. Two possible cases:

Intrasystem Interference

• Overreach interference

• Spur or junction interference.


Co channel Overreach Interference

Site D

Site A

Site B

Site C

OVERREAC

H

F1

F1

F2

F1


• Plan for a longer overreach path to add additional free-space loss to the undesired signal.

• Maximize antenna discrimination against the overreach path.

• Use a suitable route such that the overreach path can be blocked by the terrain.

Solutions: Overreach Interference


Co channel Spur and Nodal Interference

F1F2 F1F1

F1F1

F1F2

F1F2F1F1

Spur Interference

F1Nodal Interference


Use antenna with a very high front-to-back

ratio.

Worst case: Switch to 4 Frequency plan

Solutions Co channel Nodal Interference


Caused by reception of an unwanted transmission from of a different system.

Can be coordinated by adjusting the antenna discrimination and receiver selectivity, and choosing proper frequency plans.

Best Option: Coordination, control, and sometimes compromising on the radio channel through direct negotiation with the other operator on the same Frequency bands.

Note: With proper Government run Spectrum management coordination shall not happen.

Intersystem Interference


MSC 1

MSC 2

BSC 2

Hub

Example: Intersystem Interference


Intra system interference can be calculated by following method Go to Network Page by clicking ctrl N – Defaults menu – Link Label

Select TX Frequency & Polarization – Press Rest All as per shown in Fig.

Have a look to your network & make sure that all links Frequencies & Polarizations are correct according to your plan. If there is any mistake in any link please go to its work sheet & make it correct

Interference Calculation Procedure by using Pathloss 4


Select Interference – Calculate Intra and the Interference Calculation dialog box will be displayed

Enter the parameters for the calculation and press Calculate. The calculation will be carried out and saved in the same directory as the network diagram. If a second interference calculation is carried out it will overwrite the first when it is saved.



Error LogOnce the calculation is completed a number of reports can be viewed. The Error Log should be viewed to make sure that there are no missing files and that the calculation is valid. Select Interference – View Error Log

Every Site must have Call Sign

Antenna files and Radio files used in Link Budgeting must be in the selected

directories

Frequency Assign to every link

Every Link have PL4 file



Interference – Reports To view the reports select Interference – Reports and select the report to be viewed.


The Summary option provided a summary on a site by site basis of any interference cases.


The Cross Reference option provides case by case cross reference of all the interference cases found in the network.


The Case Detail option provides all the technical information on each interference case.


The Hi-Lo Violations should be viewed first to make sure that all sites are either transmitting high or transmitting low. The only exception to this rule is if different frequency bands are used at a site


When you are satisfied with the results of the interference calculation the PL 4 files associated with the interference study can be updated. Select Interference – Update Pathloss Files. The choice is either to update the threshold degradation or to remove the threshold degradation.



Space Diversity antennas located to de-correlate ground or water reflections.

Rm-m

Rm-d

Height-GainPattern

S

k = 4/3Water Reflections

2S

Tx

S/D Rx

R’m-m

R’m-d

For Ground & Water Reflections

Space Diversity Protection


Documents

Pathloss 4.0 & MW Link Planning Part 3