PATHLOSS 4.0

INTERFERENCE

1. General

Interference is :

a. Any unwanted signal

b. Copy of wanted signal delayed due to multipath propagation

c. An adjacent channel’s signal traveling over the same link

d. A signal from another radio link or RF source

There are two interference classes:

a. Between the same system ( Intra System Case): Controllable

b. Between different systems ( Inter System Case): Un controllable

Intrasystem

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

A. Overreach interference

Solution:

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

b. Maximize antenna discrimination against the overreach path.

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

B. Spur or junction interference.

Solution :

a. Use antenna with a very high front-to-back ratio.

b. Worst case: Switch to 4 Frequency plan

Intersystem Interference

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

2. Can be coordinated by adjusting the antenna discrimination and receiver selectivity, and choosing proper frequency plans.
3. Best Option: Coordination, control, and sometimes compromising on the radio channel through direct negotiation with the other operator on the same Frequency bands.
4. Note: With proper Government run Spectrum management coordination shall not happen.

2. Calculating Interference Using Pathloss 4.0

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.

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 Log

Once 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

a. Every Site must have Call Sign

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

c. Frequency Assign to every link

d. 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.

Image 9

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.