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To: Bernard Levy who wrote (10120)	1/21/1999 10:57:00 PM
From: SteveG	Respond to of 12468

<...As I indicated earlier, if you use antennas of the same size at 28Ghz and 38Ghz, the increased frequency attenuation is more than made up by the increased transmitter and antenna gains...> So do these radios use antennas of the same size? And if so, if it is "more" than made up for, does 38Ghz then actually have LESS (dry) real world attenuation than 28Ghz? And does this effect have limits? (ie., could an even bigger antenna offer even LESS 38Ghz attenuation?) And then for rain fade, 24 and 28Ghz may be more consistent, but during no or light rain (drop size being the factor, not amount of precipitation. BTW, what is the absorption coefficient of snowflakes? Higher than a fat "desert storm" water drop?), 38Ghz is the better link? And are we talking rate adapting down or lost packets? IOW, is lifeline voice preserved? <..I fail completely to see what advantage an HFC cable structure would have over FTTC+VDSL for the last 100 feet...> The prohibitive cost of telco FTTC. My ADSL pessimism isn't about the technology in theory/lab. It is about the technology running in over the real world condition of the copper plant. Thanks very much for sharing your insights and ideas, Bernard. Regards- Steve

To: Bernard Levy who wrote (10120)	1/22/1999 10:57:00 PM
From: Peter Ecclesine	Read Replies (2) \| Respond to of 12468

Hi Steve, Attenuation (in dB/km) for horizontal path due to rain, gases and fog CCIR 719,712 Frequency 8GHz 18GHz 28GHz 38GHz 48GHz 58GHz Rainfall 1"/hr .14 2 4.6 6.6 8 9 2"/hr .6 4.6 9 13 15 17 6"/hr 2 15 23 33 38 43 So if a normal link strives to have 20dB margin in worst case operation, maximum path length can be calculated from radiated power and worst case rainfall expected. e.g. 38GHz, Miami = 6"/hr rainfall = 33dB/km attenuation .001% of the year, with 120 dB link budget (from antenna sizes and transmit power), a 4km link will have < 99.999 availability, but a 3.5km link would achieve five nines. Raising the link budget to 132dB would enable the 4km link to have five nines availability. If the link is in Barstow = 1"/hr rainfall = 6.6dB/km .001% of the year, with 120dB link budget, 18km link will achieve five nines availability. Rainfall attenuation is negligible below 10GHz. petere