30 | About the Radio
Aprisa SRi User Manual 1.1.0
Frequency Hopping Synchronization
The base and remote have a pre-arranged pseudo-random channel sequence to follow where pseudo-random
channels and sequence pattern are determined per base station ID parameter settings. Up to 8 base stations
with overlapping coverage are allowed with minimal interference (see figure below).
For better channel synchronization and performance, remotes inherit zones and black-list channels settings
from the base station during registration or when user updates blacklist channels settings on the base
station. The radio frequency hopping is done on all active channels (across all zones).
A remote will override its configured channels once it registers and gets updates from base station or when
base station changes its channels configuration. At power-on, the Aprisa SRi base station immediately starts
hopping and sending packets, ACKs and beacon control packets. When a remote is powered-on or has lost
sync with the base station, it picks a random channel from its hop channel set and listens for a beacon with
a default of up to 180 seconds (a good link sync on average will be < 10 sec), covering 400 channels. A
remote doesn’t try to register before it is synch
ronized with the base station. On idle, a beacon is sent by
base station per hop set to keep sync and channel sequence. To avoid miss-synchronization, remote radios
are constantly checking for whitelist channel mismatch and in case of a mismatch, the remote will correct
the mismatch accordingly.
