PDA

View Full Version : OFDM radio over water using P.530-12


A.Tiangdah
05-06-2010, 09:29 AM
Dear All,

Does anyone has an experience with OFDM radio deployment over water/sea condition?

According to the ITU-R P.530-12, 0.72 of K value has been recommended for 48Km distance, then it led me to get almost 30dB diffraction loss since we have quite the limited Antenna Heights, but it was only 5dB diffraction loss when using a standard K 4/3 which seems to be acceptable for 0.6F1.

We discovered that sometime K 4/3 is working fine for OFDM over water condition even it has 15dB diffraction loss during design stage.

So:

1. What is the proper K value for OFDM? Should I follow the P.530-12 or just using the standard K 4/3?
2. What is the max of diffraction loss that OFDM radio can be suffering?
3. Is there any further concerning issues of the OFDM designing?

Highly appreciated to all comments/suggestions...

BRs,

A. Tiangdah

ImranSabir
05-06-2010, 07:23 PM
Dear All,

Does anyone has an experience with OFDM radio deployment over water/sea condition?

According to the ITU-R P.530-12, 0.72 of K value has been recommended for 48Km distance, then it led me to get almost 30dB diffraction loss since we have quite the limited Antenna Heights, but it was only 5dB diffraction loss when using a standard K 4/3 which seems to be acceptable for 0.6F1.

We discovered that sometime K 4/3 is working fine for OFDM over water condition even it has 15dB diffraction loss during design stage.

So:

1. What is the proper K value for OFDM? Should I follow the P.530-12 or just using the standard K 4/3?
2. What is the max of diffraction loss that OFDM radio can be suffering?
3. Is there any further concerning issues of the OFDM designing?

Highly appreciated to all comments/suggestions...

BRs,

A. Tiangdah

1. What is the proper K value for OFDM? Should I follow the P.530-12 or just using the standard K 4/3?
The K-factor is independent of the Radio or hardware. K-factor represents the propagation effect rather, the affect of Earth bulge". The k-factor depends on the area where the link is installed, the temperature, pressure, humidity and dN/dh value of the area under observation. For such a long hop length Planning a link with 4/3 is not recommended as per my experience. Better plan it for 100%F1 @ k=4/3 and 0.6F1@ k=0.6 to be on the safe side.

2. What is the max of diffraction loss that OFDM radio can be suffering?
I have not worked in particular on OFDM radio but in general if the link is experiencing Diffraction loss you have to plan the link in a way thats its Availability and Quality objectives are in line with the recommended values. To compensate the affect of Diffraction loss, u have to increase the RSL either by using Bigger Antenna or increasing the power. Similarly using the Higher freq can reduce the Diffraction loss dur to smaller Fresnel Diameter.

A.Tiangdah
05-06-2010, 07:58 PM
2. What is the max of diffraction loss that OFDM radio can be suffering?

I have not worked in particular on OFDM radio but in general if the link is experiencing Diffraction loss you have to plan the link in a way thats its Availability and Quality objectives are in line with the recommended values. To compensate the affect of Diffraction loss, u have to increase the RSL either by using Bigger Antenna or increasing the power. Similarly using the Higher freq can reduce the Diffraction loss dur to smaller Fresnel Diameter.

Reference to the answer (2) How about the planning percentage of F1 (0.6 or 1.0?) when dealing with a high Diffraction loss by maintaining AV and Quality objectives? Still we keep the link as a clear LOS for OFDM?

The Path profile telling us that the obstrucle is totally caused by earth curve due to this link is located over the sea and we have very limited tower height.

FYI., we're now locating in Tropical area which is 0.6F1 as recommended by ITU.

Thank you so much for your answering: