RC11xx(HP)-TM
RC25xx(HP)-TM
RC17xx(HP)-TM
2016 Radiocrafts AS
RC11xx(HP)/25xx(HP)/17xx(HP)-TM Data Sheet rev. 1.48 Page 22 of 86
2016 Tiny Mesh AS
Radiocrafts
Embedded Wireless Solutions
Clustered Node Detection and Network Congestion Avoidance
(CND/NCA™)
The Clustered Node Detection feature is a unique Tinymesh™ function, provided to prevent RF network
congestion in situations where multiple Tinymesh™ devices are located densely together. In, for
instance, energy metering installations, large groups of meters may often be located side-by side,
forming clusters of devices ranging from a handful of units, to tens or hundreds of meters in the same
location.
In such clustered situations, there is a risk of excessive amounts of radio traffic, causing network
congestion and bad connectivity, as the RF bandwidth will be filled with radio packets intended for
network maintenance, and there will be very little bandwidth available for data packets containing
payload data.
The Clustered Node Detection feature is controllable through the following, configurable parameters:
CLUSTERED NODE RSSI
. The default RSSI setting is 60 (-30 dBm). Lower settings will effectively disable
this function, as the value will be lower than the RX saturation level for the radio. By increasing the
value, the cluster detection function may be adapted to situations with modules using lower TX output
power.
CLUSTERED NODE DEVICE LIMIT
. The default setting is 10, forcing the clustered node detection
function to start reducing unnecessary RF traffic when more than ten devices are located closely
together.
Optimizing Polled Systems
Wireless Tinymesh™ networks are well suited for replacement of wired multi-drop systems, offering
significantly lower installation and infrastructure cost. Transparent as well as Packet mode
configurations of Tinymesh™ may satisfy the requirement for an RS485 or similar multi-drop
replacement.
Multi-drop systems often use a polled communication protocol, with a master device sending individually
addressed, or broadcast 'poll' commands, asking for response from slave devices.
A wireless mesh will generally provide less communication bandwidth as compared to a wired system,
and unnecessary communication overhead should be avoided when possible, to increase payload
throughput. The Tinymesh™ protocol stack provides a number of mechanisms that serve to improve
data throughput in master-slave systems.
In systems configured for
TRANSPARENT MODE OPERATION
, it is advisable that the master (Gateway)
performs broadcast polling rather than sending individual device poll commands.
Note: Successful implementation of broadcast polling requires that the networked devices will respond
with data packets containing the device address as part of the data payload.
When receiving a command broadcast, the networked devices will attempt communicating the
command response more or less simultaneously after executing the received command. The
Tinymesh™ Router Device that first detects a clear RF channel when performing the Listen Before Talk
procedure, will immediately start transmission. Other devices will detect that the radio channel is busy,
and will retry communication after a random time period. This automatic retry mechanism will ensure
that responses from all devices are communicated to the master (Gateway) Device error free and within
an optimum time period.
Tinymesh™ Packet mode configuration provides additional means for creating efficient replacements for
wired, polled systems. In Tinymesh™ wireless networks configured for
PACKET MODE OPERATION
, the
ORIGIN ID
of the response packet may be used to identify the individual device, eliminating the
requirement for having device address as part of the data payload. Individual Tinymesh™ devices may
also be set to generate automatic, time generated status reports, and devices may be configured to
automatically generate messages on digital or analogue input status changes, eliminating the need for
the master controller poll function. For further information, please reference the later chapter on
AUTOMATIC STATUS REPORTING
.
