Operating guide
3.2 3G and 4G connections
The data throughput is typically lower in a 3G or 4G mobile internet
connection than in a wired internet connection. 4G is though faster
than 3G. Data throughput depends on both the bandwidth and also
on the latency time.
Bandwidth on fast 3G or 4G connections may be comparable to band-
width of wired internet connections in ideal situation, but it may be
affected by signal quality, signal strength and often depends also
on other users utilization of the total bandwidth available from the
mobile internet connection provider's antenna.
3.3 IP addressing
IP addressing is also often different from wired internet connec-
tions as mobile internet connections typically use a dynamic
private IP address which is renewed/changed regularly and static
IP addressing is seldom an option.
It must be ensured that the IP address of the 3G modem is public
instead of private, i.e. accessible by other devices/servers on the
internet.
3.4 DynDNS service
To avoid the need for a static IP address of the 3G or 4G modem
the DynDNS service can be used.
This service translates a URL, which is user defined, but unique to
each modem, into the current IP address of the modem.
The modem must send its IP address to the DynDNS service pro-
vider whenever its IP address changes.
3.5 Costs
Costs typically apply to mobile internet connections which are
based on the amount of data transferred to and from the modem.
In the calculation of the data transmitted to and from the modem
not only the known data generated by the SCADA server is includ-
ed, but also any other irrelevant and unwanted data transmitted
by other devices on the internet to the IP address of the modem.
VI.HX.F2.02
ECL Comfort 296 / 310 via 3G / 4G to SCADA server
Latency time is though significantly longer in mobile internet con-
nections which results in significantly reduced performance of the
Modbus protocol.
The OPC Server must be configured to tolerate this longer re-
sponse time to requests. The performance of the SCADA system
also benefits from limiting the amount of data and sensor values
etc. requested from the controllers.
The IP addressing topic is important to SCADA systems as the
communication scheme typically used is that the SCADA server
initiates Modbus-TCP connections to the ECL Comfort 296 / 310
controllers and therefore needs to know the IP addresses of the
controllers.
The SCADA server will then be able to access the modem by ad-
dressing the URL of the modem.
The modem must support the DynDNS service and an account at
the DynDNS service provider must be available.
Flat rate subscriptions may be an alternative to achieve a fixed cost
independent of transmitted and received data.
Another alternative is a private network or virtual private network
(VPN) which ensures that only the controllers and SCADA server
within such network can exchange data.
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