User's Manual

Canopy 900 MHz AP and SM User Guide
Issue 2 August, 2004 Page 9 of 16
Depending on local practices, this may mean selecting all frequencies to scan (the SM will register to any
frequency, but takes longer to scan), only one frequency to scan (forces the SM to only register to an AP on
that frequency and minimizes scan time after SM reboot), or the three recommended AP frequencies of
906, 915, and 924 MHz (allows for an SM to “switchover” to an AP on another frequency if the one it is
registered to fails or loses signal).
Figure 1: Highlights of 900 MHz AP Configuration Page
2.5 Range of 40 Miles LOS, Increased Foliage Penetration NLOS
Description
The Canopy 900 MHz modules have a Line-of-Sight (LOS) range of 40 miles (over 64 km), and increased
Non-Line-of-Sight (NLOS) range. NLOS range is dependent on foliage, topography, obstructions, and
other RF engineering considerations. The physics of longer-wavelength 900 MHz, the power allowed by
regulatory authorities, and the low Canopy Carrier-to-Interference (C/I) ratio combine to support service
over these increased LOS and NLOS ranges.
While the expected typical range in real-world conditions is 40 miles, the AP can be set for a range up to
120 miles (over 190 km) to accommodate long shots with very clear Fresnel zone (possibly due to high
tower or mountain top location) and quiet RF environment.
Setting the range higher tells the software to have a slightly longer switchover time between transmit and
receive to accommodate longer air delay. This reduces the slots per frame available for data, which slightly
reduces aggregate throughput at the AP. However, the predictability of Canopy point-to-multi-point
throughput continues. All SMs served by an AP set to a given range continue to have the same throughput
regardless of their distance from the AP.