Establishing SignalFire Network Traffic Limits for Reliable Operations

Many industrial wireless systems utilize radio modules or a standards-based protocol to support varying data communications with its network.  SignalFire developed the radio network for its telemetry systems from the ground up to meet the specific needs of the “last mile” sensor data collection.  In addition to providing high data reliability and long-range transmissions, the SignalFire radio network has a low power and user-friendly design providing for an overall best total cost of ownership.

In addition, the SignalFire radio network optimized the data transmission rate for sensor measurements to maximize range and reliability.  In some other network radio systems, a higher data rate is utilized to accommodate high bandwidth devices such as video cameras but comes at the expense of range.  The SignalFire wireless mesh network eliminates the need to compromise reliability for data range.

As a maximum number of useable bandwidths exist for any radio network, the SignalFire network approaches over-the-air throughput in terms of number of remote device readings per gateway.  A single SignalFire Gateway can accommodate one message per second on average (60 packets per-minute), which is over 86,000 messages per day.  This traffic amount allows adequate network bandwidth for meshing and wireless configuration including remote PACTware configuration of HART instruments.

How to Calculate Network Traffic Load

To calculate the packets per-minute, evaluate the number of remote devices and their check-in (or reporting) interval.  A calculator built into the SignalFire Toolkit software simplifies this task.  To open the calculator, select the ‘Packet/Minute Calculator’ from the Tools Menu on the main toolkit window.

Begin using the calculator by entering the number of nodes configured at each check-in interval.  The calculator will display the average packets per minute, which should be less than 60.  The example below shows a network consisting of 65 nodes and a packet-per-minute average of 48.1, which is well under the limit.

To maximize your available network throughput, simply limit the number of remote devices that have fast check-in intervals.

Viewing Network Load at the Gateway

When connected to a Gateway with the ToolKit software, packets-per-minute is displayed in the left-hand side of the window.  This “real-time” view of the current Gateway load will quickly indicate if a Gateway is too heavily loaded.

Best Practices for Reducing Network Load

Consider the check-in interval required for the application. Longer check-in periods reduce network traffic while extending battery life.

Limit the number of devices configured with 5 and 15 second check-in intervals.

When using Pressure Scouts (sensor nodes), consider using alarm threshold settings to limit the number of messages the unit sends in normal operation before exceeding the configured alarm threshold(s).

Using the ToolKit Packet/Minute Calculator along with best practices will ensure a reliable network under different operating conditions.