1.     Summary

     Basing on the street lights field monitoring solution of Schneider, Beijing Inhand Company has built up a safe, reliable, powerful remote wireless solution with GPRS/EDGE and Internet by using InRouter 319Cwireless routers, InHand SMS Center and Netscreent router devices. This solution will help connect distributed PLC and its controlled devices to the control center through a wireless network with safe VPN (Virtual Private Network) technology, basing on the GPRS/EDGE network provided by mobile operators. The access of monitoring center to remote control points will be as convenient as to local devices.
2． Technology Solution
    2.1. Network Architecture
 
    1. At field ends, the controller adopts PLC-Twdio of Shneider, which accords with the
industrial Ethernet protocol and has Ethernet interfaces.
    2. PLC connection wireless routers---After power on, InRouter 319G/E starts a VPN connection to the monitoring center VPN internet Firewall according to the configuration from the network administrator.
    3. As the VPN construction succeeds, servers of the monitoring center will access the PLC which connects to the InRouter 319G/E to realize the monitoring and maintenance of field devices.
2.2 Remote Monitoring Function
“The Configuration Software server” in the monitoring center can gather field PLC data directly while the “engineer station” can also use programming software to implement maintenance through the access to this PLC address.
2.3 Remote Maintenance Function for Engineers on Business
       VPN Firewall in the center has functions such as routing and VPN access. Network management engineers responsible for the firewall maintenance can set various configurations for network intercommunication. With these functions, technology engineers or administrators can realize the VPN connection to the monitoring center through internet and access the connected PLC through VPN Firewall of the center.
      The security is ensured with the distribution of accounts, passwords, routing policies and identity validity according to the requirement, which is implemented by network management engineers responsible for the maintenance of this firewall.
     
 
 
     This mode has provided us a flexible, safe mechanism to maintain filed devices. If an engineer is out on business when Filed 1 is in need of maintenance, network management engineers in the monitoring center will generate temporarily a VPN policy for him to admit his VPN dialing-in to the center and set the routing rules of Field 1.With this configuration, the engineer can use a notebook or a PC to dialup internet, then connect with the monitoring center in VPN method and access the PLC of Field 1 with programming software. As the maintenance is completed, the engineer ends VPN connection, at the same time his temporary setting can be deleted by the network management engineers in the monitoring center.
2.4 Short Message (SMS) Alarm Function
        According to some applications, clients probably need to monitor some address values of PLC or RTU, and to receive an alarm when the values are out of range. We can also provide short message (SMS) alarms as well as field alarms.
As the below figure shows:
     
      After the VPN connection is built up between InRouter319G/E and VPN FIREWALL of the monitoring center, short message (SMS) servers of the center will implement real-time monitoring on the values of nominated addresses in every field PLC, and send alarming short messages (SMS) to the receivers set beforehand as soon as the values are out of certain range. Meanwhile short message servers can realize the PLC control by special SMS function according to requirements.
      
3． Solution Features and Advantages
Required environment, devices and software:
       Ø Helping the control center realize access to internet and possessing IP of public  network;
       Ø Qualified with SIM cards providing China Mobile data service;
       Ø Field coverage by GPRS/EDGE network signal of China Mobile;
       Ø InRouter 300G/E or InRouter 319G/E (VPN solution);
       Ø VPN Firewall (Intermediate and advanced VPNs such as Cisco or Netscreen is  recommend for the access to firewalls and routers in the control center) ;
       Ø Engineers station and configuration software severs( determined by customer  monitoring requirements);
       Ø InHand SMSCenter software + InHand SMS modem * 1(supplied only for SMS  function);
       Ø One SMS server(supplied only for SMS function required ); 
 Technical parameters:
       Ø EDGE network access;
       Ø Communication rate: uplink rate: average 80kbps    downlink rate: 110kbp;(measured data)
       Ø Icmp average delay 600ms;
       Ø Ipsec VPN access;
       Ø InRouter 319C features:
Voltage: DC 24V;
Shell: industrial design；
Installation mode: on rack;
LAN interface: Ethernet RJ45
 
Advantages:
       Ø Wireless access to internet and wide coverage, basing on GPRS/EDGE network of  operators, available for the remote monitoring of distributed devices;
       Ø Relatively low cost;
       Ø Fast speed of projects implementation;
       Ø Data security ensured by technology methods such VPN;
       Ø Promoted work efficiency and convenient maintenance wherever in the monitoring center or out on business.