China Mobile, China Unicom's GPRS network, CDMA network has covered a large area, and data transmission is achieved through wireless networks.
can. Wireless MODEM uses GPRS, CDMA modules via China Mobile, China Unicom's GPRS, CDMA network for data transmission, and
After the TCP / IP protocol is subjected to a data package, it can flexibly implement a variety of equipment access, the engineering installation is simple, and in the application of industrial field data transmission,
Very good solution to data transfer in remote non-telephone-free lines. It is more simple and flexible to compare, more simple, flexible.
Easy to operability, while also reduced costs, wireless Modem Transmission Schemes is the best choice for modern industrial field data transmission. At present, China Mobile, China Unicom's GPRS network, CDMA network data transmission bandwidth is around 40kbps, and limited by bandwidth, number
According to the acquisition plan, the active alarm, data wheel patrol, alarm active callback, etc., the transmission bandwidth occupies less acquisition method. At the same time considering
Support for the real-time collection scheme, the wireless MODEM transfer program can only be supplemented by the current transmission scheme. With the continuous development of wireless communication technology, the wireless transmission data bandwidth will continue to improve, using 3G wireless network, the data transmission bandwidth will reach 2m, no
The line transfer program will gradually become the main application solution for monitoring transmission networking. Currently, due to the inherent characteristics of GPRS and CDMA, the applications of GPRS and CDMA in various fields are also more extensive, but about transmission
The use of TCP / IP protocols or UDP protocols, but they argue a lot.
It is simple to say the difference between TCP and UDP first: 1. Based on the connection and connection 2. Requirements for system resources (more TCP, less UDP) 3. The UDP program structure is simpler 4. Flow mode and datagram mode 5. TCP guarantees the correctness of the data, UDP may packet, TCP guarantees data order, UDP does not guarantee
In addition, talk about their differences in conjunction with the GPRS network: 1. There is a certain delay in TCP transmission, probably 1600ms (mobile), and the UDP response speed is slightly fast. 2. TCP Baotou Source Port 16-bit Target Port 16-bit serial number 32-bit response number 32-bit TCP head length 4 bit RESERVED 6-bit control code 6-bit window size 16-bit offset 16 bit checksum 16-bit option 32 bits (can Select) So we got the smallest size of the TCP header. It is 20 bytes.
UDP Baotou Source Port 16-bit destination port 16-bit length 16-bit checks and 16-bit UDP packages are much smaller. It is true. Because UDP is non-reliable. The design is to send the packet as quickly as possible. So UDP Association
It is very streamlined.
3. GPRS network port resource, UDP is very shortage, fast change; and TCP uses reliable link transmission, there is no problem with port changes
Industrial applications generally have the following characteristics,
1. When you are required, there are also some occasions that are timing transmission. In general, the server center and GPRS terminal are required during the entire transmission process.
It is ready to transfer data from each other. The TCP itself is a reliable link transmission, providing an hourly two-way transmission channel, which can meet the requirements of industrial field transmission. GPRS
There is also a limit on the TCP link: this link is long (about 20 minutes, depending on the specific situation), there is no data traffic, will
The priority of this link is automatically reduced until this link is enforced. So in actual use, a heartbeat package is also used (usually a byte data)
Maintain this link. UDP due to its own characteristics, as well as the finish of the GPRS network UDP port resource, the port is easy to change after a period of time, and the port is easy to change.
The influence of the student is to send data from the server center to the GPRS terminal, and the GPRS terminal is not received. The specific reason is that the mobile gateway has been transferred from it, and it is necessary to send the host to the host. This IP and port numbers are maintained. This host can take the initiative to send UDP packages and I am
It was found in the test. This interval is very short. I will send a UDP package in more than 1 minute to maintain it, but it is possible to lose this.
The port is, at this time, if the host wants to actively send data to GPRS, then it is certainly no, only the GPRS terminal device sends a UDP package, mobile
Revoluting a transfer IP and port to you can be two-way communications.
2. The packet loss rate of data is required. Some industrial occasions, such as electricity, water meter reading, environmental monitoring, etc., do not allow data from the transmission process
Loss or maximum requirements data reliability. From this point of view, it is clear that the TCP is more powerful, reliability, and smaller packet loss in the wireless data transmission process.
rate. This is also true in actual tests. Taking the GPRS terminal equipment provided by Xiamen Lands Communications Co., Ltd. as an example: TCP in millither 9, UDP is around 17,000.
3. Requires costs. At present, there is a large part of the GPRS equipment to replace the previous wireless digital radio station. In addition to the scope of use, it considers
The main problem is the cost. It is of course most willing to accept. And the cost is directly related to traffic, low flow, low cost
. Although TCP itself is more than UDP, UDP often needs to maintain bidirectional channels in practical applications, you must pass a lot of heartbeats.
Data to maintain port resources. Total comparison, the actual traffic of UDP is larger than TCP. Many users don't know in the early days.
UDP requires a large number of heartbeat packages to maintain port resources, often think that UDP is more saving more than TCP, in fact, there is one
Misunderstanding.
4. In some specific applications, such as some banks of time interactive system, high requirements for response speed, at this time, the data transmission frequency is faster, not
Need a large number of heartbeat packages to maintain UDP port resources, it is more advantageous to use UDP.
5. In the current 1: N transmission mode, there are both multiple GPRS terminal devices to transfer data to one server center. At this time, UDP will be smaller than TCP.
It is much better because UDP consumes less system resources. But in practical applications, it is found that many users are also transmitted by TCP, build
Estuary Central 1: A (1: N), that is, each sub-center corresponds to the N / A device, independently processing data, and then delivers the data to the main center. This
Of the transmission protocols that use TCP during transmission, and it is well to process the problem of system consumption of multi-link of the central server. In general, I think TCP / IP protocols can meet the current requirements of remote data transmission, which provides a more stable and more convenient transmission channel.
It is very good to meet the requirements of remote data transmission.
