Competition between UDP and TCP Protocols in the Communication Network

In the communication field, we are still using the inherent GPRS communication method. The network protocol for it includes the UDP protocol and the TCP protocol. Now let's talk about the selection and requirements of the following two protocols based on the GPRS network bearer capability. Now let's take a look at the following article.

◆ Network carrying capacity

GPRS group business channel can adopt CS-1 ~ Different encoding methods of CS-4 (9.05 kbit/s, 13.4 kbit/s, 15.6 kbit/s, 21.4 kbit/s, kbit/s, in addition, the wireless environment is good, and when the channel is sufficient, the theoretical maximum rate supported by the GPRS network can be 171.2 kbps, this speed can fully support some application services with high bandwidth requirements, such as multimedia image transmission services. However, the actual data transmission rate is affected by Network encoding methods and terminal support, CS-3, CS-4 receiving reference sensitivity is low, the two encoding methods can be used only in areas close to the base station and good signal ｡

At present, GPRS uses CS-2 channel coding scheme to ensure that more than 90% of the residential area coverage, to meet the requirements of C/I not less than 9dB ~ 4. GPRS Channel (PDCH). At least one static group data service channel is set at the initial stage of GPRS wireless channel allocation, and PDCH allocation will be adjusted based on GPRS traffic, dynamic Channels are preferentially allocated to voice channels to ensure GSM quality. Therefore, the GPRS bandwidth is 13.4Kbps ~ 54.4Kbps ｡

On China Mobile's GPRS network, the uplink and downlink channels are allocated using the uplink and downlink asymmetry methods. The uplink speed is small and the downlink speed is large, usually 1 + 2, 1 + 3, 2 + 4, etc. This is mainly set for customers to access the Internet. In industrial applications, the opposite is true, the uplink data is larger than the downlink data. Therefore, when considering the GPRS network bandwidth problem, we should consider the uplink bandwidth with a narrow bandwidth ｡

GPRS services are characterized by data channel sharing, which facilitates paybytraffic. However, in the case of a large number of terminals and a large amount of data in a residential area, terminals must compete in limited bandwidth, leading to high disconnection rate and difficulty in accessing the Internet. This is the new application feature that emerged after one year of GPRS activation: GPRS is not competitive in the individual user market, but it has a strong advantage in a large amount of industry data transmission ｡

Limited Bandwidth Resources Demand applications: small data volumes and high transmission efficiency ｡

◆ Industrial Application Requirements

GPRS industry applications, such as power meter reading, pipe network monitoring, meteorological collection, and financial services, are communication between terminal devices and data servers. Before GPRS transmission is provided, there are radio stations, MODEM (telephone lines), leased lines, Direct cable connections, and other methods. These methods provide great communication quality differences. In industrial applications, the requirements for transmission reliability are high. Generally, data loss is not acceptable. Therefore, you must ensure that no data is lost. Basically, GRPS applications use the TCP protocol for transmission, ensure data security and accuracy ｡

The UDP protocol is used for transmission, which greatly reduces the data reliability ｡

The TCP protocol performs multi-packet unified validation according to the protocol window, which can reduce the number of ACK packets. However, in industrial applications, the application features a small amount of data, therefore, it is worthwhile to use certain network resources in exchange for reliable data transmission ｡

In the entire application system, the transmission guarantee is completed by the application protocol and the network protocol. You must make full use of the advantages of the application protocol and network protocol, the goal is to achieve the best overall transmission quality, the highest efficiency, and the best effect. In application protocols, most of them have basic transmission assurance functions, and then use TCP protocol for data communication, it will bring GRPS applications in industrial fields closer to perfection ｡

◆ Other issues to be considered

TCP connection ensures data transmission reliability. Each specific TCP implementation must select a Maximum message Segment survival time MSL (Maximum Segment Lifetime) it is the longest time in the network before any packet segment is discarded. We know this time is limited. RFC 793 [Postel 1981c] indicates that MSL is 2 minutes, the commonly used value in the implementation is 30 seconds, 1 minute, or 2 minutes. For most real-time monitoring systems, this is enough. When using UDP connections, when the network is congested, some data packets are discarded, causing the loss of some required data ｡

The Application of GPRS in the power system has just started and is in a small-scale trial phase. No matter the UDP or TCP protocol is used, there will be no significant pressure on the network and server systems. When the TCP protocol is used, reliable transmission is more convenient. With the development of network bandwidth from 10 m, m to m, in the future, the TCP protocol will be used in urban electric power distribution network automation, meter reading, and other applications in a better way ｡

◆ Conclusion

In industrial applications, the characteristics of industrial applications need to be carefully analyzed and UDP or TCP protocol should be selected as needed. A few applications with scattered multiple points, small data volumes, high real-time requirements, and a large number of terminals should be selected, UDP protocol can be considered. For most industrial applications with large data volumes, strict data reliability requirements, a small number of terminals, and some special applications, TCP is a mandatory protocol with a wide application area ｡