About the Radio | 25
Aprisa SRi User Manual 1.1.0
Product Overview
Network Coverage and Capacity
The Aprisa SRi has a typical link range of up to 50 km / 30 miles, however, geographic features, such as
hills, mountains, trees and foliage, or other path obstructions, such as buildings, will limit radio coverage.
Additionally, geography may reduce network capacity at the edge of the network where errors may occur
and require retransmission. However, the Aprisa SRi uses 1 W (+30 dBm) peak output power and Forward
Error Correction (FEC) which greatly improves the sensitivity and system gain performance of the radio
resulting in less retries and minimal reduction in capacity.
Ultimately, the overall performance of any specific network will be defined by a range of factors including
the RF output power, the modulation used and its related receiver sensitivity, interference from other
unlicensed radios, the geographic location, the number of remote radios in the base station coverage area
and the traffic profile across the network. Effective network design will distribute the total number of
remote radios across the available base stations to ensure optimal geographic coverage and network
capacity.
One base station can register and operate with up to 500 remote radios.
The practical limit of remote radios that can operate with one base station is determined by a range of
factors including the number of services, the packet sizes, the protocols used, the message types and
network timeouts.
Automatic Registration
On start-up, the remote radio listens for the base station and tries to sync with base station frequency
hopping before attempting registration. It then transmits a registration message to the base station which
responds with a registration response. The base station records the details of all the remote radios active
in the network.
If a remote radio cannot register with the base station after multiple attempts within 10 minutes, it will
automatically reboot. If remote is not able to register with base station in 5 attempts, then a ‘Network
Configu
ration Warning’ alarm event will be raised indicating that a remote is not registered with the base
station.
If a remote radio has registered with the base station but then loses communication, it will automatically
reboot within 2 minutes.
Remote Messaging
There are two message types in the Aprisa SRi network, broadcast messages and unicast messages. Broadcast
messages are transmitted by the base station to the remote radios and unicast messages are transmitted by
the remote radio to the base station. These messages are commonly referred to as uplink (unicast remote
to base) and downlink (broadcast base to remote).
All remotes within the coverage area will receive broadcast messages and pass them on to either the
Ethernet or serial interface. The RTU determines if the message is intended for it and will accept it or
discard it.
