GPRS universal wireless packet service is a wireless packet switching technology based on GSM system, providing end-to-end, wide-area wireless IP connection. GPRS makes full use of shared wireless channels and uses IP Over PPP to achieve high-speed and remote access of data terminals. As a transitional technology (2.5G) for the evolution of existing GSM networks to third-generation mobile communications, GPRS has significant advantages in many respects.
The networking of the GPRS wireless monitoring system is relatively simple, and the GPRS modem can be directly connected to the user device through a RS232 or RS485 interface.
Access to the data terminal (GPRS modem): GPRS users can choose CMNET and APN access network, CMNET is usually used for public users, APN for industrial users, generally in one packet, the user needs to set user name and password, this will have better security. In addition, APN users can apply to bind a fixed IP address of the mobile intranet.
The networking of the data center is slightly more complicated. Combined with the characteristics of the GPRS bearer network, according to the GPRS application fields, we provide the data center networking plans in various application forms for developers’ reference. Selecting the networking form depends on the amount of business data, reliability requirements, data confidentiality, and network conditions.
Plan 1: GPRS MODEM access way(The monitoring center being as the data terminal is bound to the fixed IP address)
This plan is suitable for enterprises that do not have access to the Internet and have high security requirements; it is suitable for applications where they do not have no high requirement for the total data bandwidth, such as data acquisition systems using the Polling transport protocol; all data is run in the GPRS network; all GPRS terminals are required to communicate directly; the data center's GPRS data terminal access point is bound to a fixed IP address. (ie at least provide one SIM card with a fixed IP address)
Plan 2: Internet access way(The monitoring center accesses the wireless network via the Internet.)The enterprise has a stable, permanent access to the Internet; the router port address of the enterprise and the IP address of the monitoring center should be public, which are provided by the ISP that provides the Internet access for the enterprise. As for this solution, the client must first apply for the fixed IP address of the public network to the INTERNET operator. The center uses the public network to fix the IP, and the monitoring point directly initiates the connection to the center. Or the client company has a server connected to the Internet and has a fixed IP address on the public network, however, considering the stable operation of the server, it is usually not allowed to install other applications on the server. Therefore, the GPRS data center system can not be installed on the server, it can be solved by NAT port mapping.
This plan is very good in real-time and stability, but the fixed IP usage fee of the public network is relatively high.
Plan 3: Dedicated line access way (The monitoring center accesses the wireless network via DDN special line)
The plan is suitable for enterprises that do not have access to the Internet or that have high security requirements, it is also suitable for industries such as finance, securities, and industrial monitoring; the enterprise accesses China Mobile's router through a dedicated line, and access router of the client must provide a public IP address.
Plan 4: Dynamic IP solution
For an application system without a fixed IP, the networking mode is the same as “fixed IP access”. The key to solving the problem is the data center. There are currently two solutions:
1. SMS sends IP
When the IP address of the data center changes, the central site can notify the latest IP address of the terminal device by SMS and notify the connection. SMS sending can use GPRS modem via Internet or USB interface.
2. Dynamic Domain Name Server
When using the dynamic DNS method, there are a few things to prepare first.
First is Domain Name, it is necessary to apply for a set of third-level or second-level domain.
Second is to go to the Domain Management Center to specify the dynamic DNS service.
When the preparation is completed, a client software will be obtained from the domain management center to maintain the dynamic IP and the Domain Name, after the computer in the data center is powered on, the dynamic IP can be obtained from the ISP, and then the client software can be connected to the DDNS server, refresh the domain name and make comparison between IP and the domain name. The GPRS terminal can perform the forward and reverse interpretation of the Domain Name through the DNS method, and then establish connection.
GPRS modem can provide several following applications: