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Radio Frequency signal loss compared to a conventional meteor burst system 
     last updated 10/12/2002

Baseline - - - -
    Base station: 5,000 watt transmitter with a tall antenna
    Remote Station: 5 watt transmitter with an whip antenna
       New remote station 0.1 watt ( FCC generally approves this low without licenses)

Proposed Meteor Burst system change from baseline in db (= signal level)
  examining the worst case: Remote to Base Station

Base station receiver antenna array: +5db  
  - receive/transmit in 30 degree sectors instead of current 120 degree sectors
  - array of smart antennas ( not too wide of angle possible for meteor bursts)
  - antenna array mounted > 3 wavelengths (27 feet) above the ground
       see web page on Smart Antennas

Base station antenna space diversity: +40db  
Have base station antennas spread across 10-30 KM of antenna farm.  e.g. BLAST
Note: This should also increase the percentage of time that fading signal can be received at base station

Demodulation: +6 db  
There are a variety of modulation types to consider - QASK, RAKE (time diversity), 

Forward Error Correction: +6db  
Add bits to packet so that noise bursts can be removed without delay for packet re-transmission

Process gain: +20db
The signal is spread across the spectrum.
Signal is retrieved from the noise at the base receiver by correlation - as with GPS
A 20 db gain assumes that 10k bits/sec is spread 100X across 1MHz
Note: Process gain is not used in the path from base to remote since it could increase power consumption by 100X

Transmit power -15db =  0.1 watt instead of 5 watts

 Net gain = 62db (+5, +40, +6, +6, +20 +0 -15)

This will allow a decrease in antenna efficiency at personal transmitter: -52 db  
       which permits the use of a very small antenna, and leaves an additional 10 db signal transmission losses (foliage, buildings, etc)

 Note: Emergency messages will probably use 100 tx bits for every data bit
    thus emergency messages will have an additional 20db

the above estimates are taken from:
- Spread Spectrum Systems with commercial applications - Dixon 1994
- Meteor Burst Communications  theory and practice  D. Schilling 1993
- Robust Modulation Methods & Smart Antennas in Wireless Communications B Pattan 2000
- The Comprehensive guide to wireless technologies  2000
 -     and 10 other professional papers.

ToDo as of 8/02:
 - Check capability of current meteor-burst systems in low signal locations
      such as in buildings, deep valleys, and forests
 - Estimate number of communications channels needed in urban area

First estimate of transmission power required at base:
  0.1 watt + 50 db (40db antenna diversity +10db process gain) = about 30 watt