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This question refers to the link below: http://www.brighthubengineering.com/consumer-appliances-electronics/102752-the-longley-rice-propagation-model-and-tv-white-space-for-ultra-wifi/

What does this line means: In other words, this radio propagation model forecasts long-lasting median transmission loss across asymmetrical terrain relative to white-space transmission loss.

Can anyone please explain?

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The article you referenced is talking about the TV signals themselves. This can be different for various receiving locations due to distance or terrain.

White space is the portion of the NTSC (or PAL) scan where there is no visual information so there is room for some data to be inserted.

Thus, your question is a combination of the two, but really can be reduced only to the one - that of the reach of the TV signal.

In other words, with the same data modulated onto the signal, the dominant characteristic for throughput is the strength of the carrier at the receiving end. Like listening for other signals through noise.

Answer: It is a measure of the loss of data (either in rate or entirely) due to the propagation of the carrier TV signal to a specific receiver.

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I believe what it's trying to say is that it predicts the transmission loss over terrain (hills, mountains, valleys, etc.) compared to transmission through clear air.

For an example of terrain, consider receiving a transmission from a television or radio station that's, say, 40 miles away from you with hills, valleys, ridges, etc., in the space between.

For an example of clear air, consider receiving a transmission from a geosynchronous satellite that's precisely overhead at all times, and you're using a highly directional antenna (e.g., a parabolic) mounted high enough that there's essentially nothing between the transmitter and the receiver that the signal could reflect from on its way to the receiving antenna so multipath (for example) is limited to atmospheric effects.

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  • \$\begingroup\$ What does long-lasting mean? \$\endgroup\$ – Creator Nov 7 '17 at 0:54
  • \$\begingroup\$ @Creator: it means things that aren't transient--e.g., come and gone in a few milliseconds. \$\endgroup\$ – Jerry Coffin Nov 7 '17 at 0:57
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rev A

In this context;

1) "Long Range" means 1 km to 2000 km.

2) "white" path loss is the path loss in the spare (white) spectrum previously allocated to future TV channel, which the FCC intends to use for a wide variety of digital communications.

Some of the losses are called Rice Fading ( or Ricean) with multipath phase cancellation of varying amplitudes not included in Friis Loss models.

3) "asymmetrical terrain" causes additional path loss from shadow effects of terrain different from assumed point-point loss in Friis Loss calculators, which has a positive effect for co-channel shared access separated by terrain and a negative effect for point-point communication.

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