# Link Calculator

The ‘Link calculator’ analyzes the microwave propagation measurements of the wireless links. It can be accessed through the Network Map by clicking on the ‘link calculation’ button available in microwave links.

## View

The app includes two view possibilities. If it is accessed via the menu, the view provides a form table and a blank information table. The form table offers inputs for latitude and longitude values of the two points of a link. By entering this geographical information the data in the information table gets updated.

The information table contains the calculation inputs and outputs. If the Link Calculator is accessed through the ‘calculate link’ button, only this table with pre-filled geographical locations is shown. Currently, input variables of the link calculation include Polarization, Frequency, Rain Model, and Rainfall Rate. Outputs of the calculation are Free Space Loss and Rain Loss. The results will be visible upon clicking the ‘Calculate’ button at the bottom of the table.

### Average Mean Sea Level

Denotes the ground elevation of the sites on each end.

### Antenna Height Above Ground

Is the height at which the antenna is mounted from the ground.

### Distance

The distance in the information table is auto-filled when the microwave link is selected and the calculator is accessed through the ‘calculate link’ button in the Network Map. If the points are entered manually, the distance is calculated after clicking the ‘Calculate’ button.

### Polarization

A selection of Vertical and Horizontal polarization is possible.

### Frequency

A selection of known and regulated microwave bands is possible.

### Rainfall Rate

Rainfall rate can be entered in the field, however if the local information is not available, the digital map and rainfall values of ITU-R P.837-7 [1] is used. The latitude grid is from -90 North degrees to +90 North degrees and the longitude grid is from -180 degrees East to +180 East. For this calculation, the pre-computed R_0.01 map is used. A selection is possible through the Rain Model drop-down list. When the ITU model is selected, the rainfall rate will be shown in the rainfall rate field after clicking the ‘Calculate’ button.

## Calculations

Wireless signal attenuation is calculated based on ITU Recommendations for Propagation. At the moment these calculations include the free space loss and rain loss.

### Free Space Loss

Calculates the Free Space Path Loss for a point-to-point non-terrestrial link using the recommended formula in ITU-R P.525-4 [2]. The output is shown in dB hence the distance is attributed in the calculation.

### Rain Loss

Calculates the rain induced attenuation on microwave signal. The calculation is based on the recommended formula in ITU-R P.838-3 [3], taking into account the polarization of the signal, rainfall rate, and distance. The manual calculation is also possible if ‘Specific Rain’ is selected as rain model. After selecting the inputs, rain loss will be calculated by clicking the ‘Calculate’ button.