3.3.1. Further information about IP address solutions using GPRS Systems
GPRS is a communication technology that allows data acquisition systems to overcome the difficulty
of cabling for wide area remote sites. GPRS applications are becoming more prevalent, but the
dynamic IP address issues associated with GPRS networking continue to frustrate system integrators.
The trouble with I/O devices with GPRS capability is that they receive a different IP address every
time they connect to the GPRS network.
Three distinct solutions have been developed to overcome this challenge:
Solution 1: Public Static IP Address
The first option is to obtain a public static IP address; some carriers (telecom service providers) can
assign a static IP address to a specific SIM card. This way, all the I/O devices will have their own
static IP address. The main benefit of this solution is that it behaves like a wired solution. However,
not all carriers offer this kind of service.
Solution 2: VPN Service Provided by Carrier/MVNO
A VPN (Virtual Private Network) is a secure LAN solution that groups specific devices together. The
VPN grouping concept solves the dynamic IP address issues and prevents unauthorized persons
from accessing the data. For this VPN solution, customers are required to buy one of a number of
different GPRS on-line services to be able to access a Virtual Private Network (VPN). When the
GPRS device dials up, the carrier will assign a private IP address which is on the same network
segment as the host and can maintain bi-directional communication using a polling architecture. Many
enterprise clients turn to mobile virtual network operators (MVNO). These MVNO’s acquire numerous
GPRS services and then rents them out to customers who are looking for a small number of IP
addresses.
Unfortunately, some countries do not have MVNOs, and some carriers do not provide VPN services.
For this reason, this solution may be unfeasible for some users.
Aeroqual has used www.wyless.com successfully to communicate with AQM instruments.
Solution 3: DDNS
Using dynamic IP addresses is often necessary since many ISPs do not provide static IP addresses.
The Dynamic Domain Name System (DDNS) is used to convert a device’s name into a dynamic IP
address so that remote devices can communicate with the control centre using a fixed domain name.
DDNS takes care of the Dynamic IP address of a device, and DNS the static IP address of a device.
With most remote GPRS devices, you need to apply for a hostname for each of the devices handled
by the DDNS server. When GPRS devices get an IP address from the carrier, they will automatically
connect to the GPRS network. Each time a GPRS device’s built-in DDNS client gets a new IP
address, it will send the IP address to the DDNS sever.
Aeroqual has integrated the “DynDNS Pro” service from
modem. For a small annual fee you can configure up to 30 host names to use with up to 30
modems.
3.3.2. Email Message
This function assumes the modem is fitted and correctly configured. It is activa
ted by the “Enable
Email Alert” tick box under Operations. Up to 5 Email recipients can be connected at once.
