User's Manual

42 Planning for the Street Lighting Solution
• When receiving a message, the Street Light Bridge module replies only
on the channel on which the message was received (PL or RF). In this
case, “reply” means response, acknowledgement, challenge, or reply.
• When receiving a proxy request, the Street Light Bridge module forwards
the request to both the RF and PL channels.
A Street Light Bridge module does not repeat a packet onto the RF channel
unless it receives a request from the Segment Controller to repeat. When
directed to repeat onto the RF channel, the receiver waits until all the retries
from the originator have completed before repeating onto the same channel.
Thus, a Street Light Bridge module attempts to keep the RF channel clear while
another module is using it, and does not send responses while the originator is
busy sending repeats of the request.
The Street Light Bridge module uses information in each packet header to detect
packet duplication, replay attacks, and network intrusion.
Scheduling
The Segment Controller includes an Event Scheduler application that you can
use to schedule events. Thus, for example, you can schedule luminaires to turn
on at sundown, dim at the end of the evening rush hour, brighten at the start of
the morning rush hour, and then turn off at sunrise. In general, you would not
define an event schedule for Street Light Bridge modules (they should run
continuously).
See Chapter
6, Controlling a Street Lighting Network , on page 77, for more
information about scheduling.
Device and Network Recovery Planning
The Street Light Bridge module has a watchdog mechanism that covers the main
processor, the Smart Transceiver, and the radio communication chip. That is, if
LonTalk (ISO/IEC 14908-1) communications are lost, the Smart Transceiver
resets; if the radio communications are lost, the radio communication chip resets.
Figure 10 shows a simple street lighting network with two Street Light Bridge
modules. This section considers two recovery scenarios: loss of SLB A or loss of
SLB B. For any extended outage (generally longer than 15 minutes), the
Segment Controller should report the outage so that network management
personnel can investigate and repair the outage.
Figure 10. An Example Street Lighting Network
These scenarios assume that both SLB A and B have the same RF channel lists
(primary 25, 20, 15 and secondary 11, 17, 26) – an assumption that should apply
to nearly all street lighting networks. Also, these scenarios assume that the
network has good communications prior to device failure.