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Data communication and its application prospects
Data communication, as a key communication service, plays a crucial role in enabling generalized telematics. With the growing integration of computers and intelligent devices across various fields, the scope of data communication is continuously expanding. Common applications include file transfer, email, voicemail, text viewing, directory searching, smart user telegrams, and remote telemetry control. For each specific application, the necessary communication functions must be implemented within the telematics system or computer network, typically defined through layered protocols.
**First, the basic concepts and exchange methods of data communication**
**1. The basic concept of data communication**
**(1) Information, data, and signals**
1. Information represents the attributes and relationships of an object, reflecting the existence and movement of physical entities.
2. Data can be broadly understood as "digital form of information." Narrowly, it refers to structured digital information such as statistical, meteorological, or measurement data. In computer networks, data is generally seen as binary code used for storage, processing, and transmission.
3. A signal is a medium that carries information. Terms like electrical, electromagnetic, optical, or modulated signals refer to different forms of transmission media carrying specific data.
**(2) Model of data communication system**
The communication system model outlines how data is transmitted from one point to another.
**2. Data communication exchange methods**
**2.1 Three common switching methods**
1. **Circuit switching** involves establishing a dedicated physical connection between two devices during communication. This connection remains exclusive until the communication ends, making it ideal for real-time, continuous data transfer but inefficient in terms of resource utilization.
2. **Message switching** stores the entire message at intermediate nodes before forwarding it once the destination path is available. This method improves network efficiency but introduces significant delays.
3. **Packet switching** divides messages into smaller packets, which are then transmitted individually across the network using a store-and-forward approach. This method is highly efficient and widely used in modern networks.
**2.2 Application areas of each method**
1. Circuit switching is commonly used in public telephone and telegraph networks, as well as in circuit-switched public data networks (CSPDNs). It offers low delay and high reliability, but its low line utilization makes it less suitable for bursty traffic.
2. Message switching is ideal for communication between terminals with varying speeds and protocols. However, due to large delays and memory requirements, it is not suitable for time-sensitive applications.
3. Packet switching combines the advantages of both circuit and message switching, offering flexibility, efficiency, and scalability. It is widely used in modern data networks.
**Second, classification of data communications**
**Wired data communication**
**1.1 Digital Data Network (DDN)**
A DDN consists of subscriber loops, digital channels, and a central management system. It uses fiber optics, microwave, or satellite links to provide reliable digital communication. While the network aims for full digital transmission, some parts still use traditional copper lines, leading to lower quality.
**1.2 Packet Switched Network (PSPDN)**
Based on the CCITT X.25 recommendation, this network uses store-and-forward techniques to divide messages into segments with address information. It supports multiple virtual paths and has dynamic routing capabilities, though its performance is generally limited compared to newer technologies.
**1.3 Frame Relay Network**
Frame relay evolved from packet switching technology, allowing efficient bandwidth sharing and dynamic allocation. It uses virtual circuits and simplifies network node processing by focusing only on the physical and link layers. Its high transmission quality and low error rate make it ideal for bursty traffic.
**1.4 Asynchronous Transfer Mode (ATM)**
ATM uses fixed-length cells for fast and efficient switching, supporting broadband services like video conferencing and interactive TV. It maintains the real-time benefits of circuit switching while being flexible enough to handle diverse data types. ATM is a key technology for B-ISDN and is also used for wide area network interconnection and LAN emulation.
**2. Wireless data communication**
Wireless data communication, also known as mobile data communication, allows data transmission via radio waves, enabling mobility. Unlike wired communication, which is limited to fixed locations, wireless communication extends the reach of data networks to portable and mobile users. It connects with wired networks to provide seamless access for users on the move.