Data transmission refers to the complete process of securely and accurately transferring data from the "source" (the device that generates/stores the data) to the "destination" (the device that receives/uses the data) through a specific "transmission medium" and "communication protocol." Essentially, it is the "spatial transfer" of data, supporting the interconnectivity of all electronic devices.

Ⅰ. Core Components (Each is indispensable)

Data itself: The core content of the transmission, including text, images, video, audio, commands, sensor data, etc. (e.g., WeChat messages, online course videos, mobile payment transaction information).

Source and Destination: The source is the sender of the data (e.g., your mobile phone, company server, camera); the destination is the receiver (e.g., a friend's mobile phone, home computer, cloud storage device).

Transmission medium: The "channel" for data transmission, divided into two categories:
Wired media: Network cables (twisted pair), fiber optics, coaxial cables (e.g., cable TV lines), characterized by stability and high speed;
Wireless media: Radio waves, infrared rays, satellite signals, characterized by flexibility and no need for wiring (e.g., Wi-Fi, 5G, Bluetooth).

Communication Protocol: The "rulebook" for data transmission, specifying data encoding methods, transmission rates, error correction mechanisms, address identification, etc. (e.g., TCP/IP for internet access, BLE for Bluetooth transmission, UDP for video calls).

Ⅱ. Key Processes (Simplified Version)

1. Source end "encodes/packs" data: Converts raw data into a format suitable for transmission (e.g., converts text into binary code, adds a "checksum" to video data to prevent errors);

2. Transmits through the transmission medium: Data propagates in the channel in the form of electrical signals (wired) or electromagnetic waves (wireless);

3. Destination end receives and "decodes/unpacks": Restores the original data and checks for errors (if an error occurs, a retransmission is requested);

4. Transmission completes: The destination end successfully reads or uses the data (e.g., opens a file, plays a video).

Ⅲ. Common Types (Classified by Scenario)

By Transmission Direction: One-way transmission (e.g., broadcasting, surveillance camera feed), two-way transmission (e.g., WeChat chat, video calls);
By Transmission Method: Serial transmission (data is sent bit by bit, e.g., transferring files via USB cable), parallel transmission (multiple bits of data are sent simultaneously, e.g., connecting a computer motherboard to a hard drive);
By Network Range: Short-range transmission (transferring photos via Bluetooth, connecting a printer to a computer), long-range transmission (browsing the web, cross-city video conferencing).

Ⅳ. Core Indicators (Measurement of Transmission Quality)

Transmission Rate: The amount of data transmitted per unit time (e.g., 100Mbps broadband, 5G peak rate 1Gbps);
Latency: The time it takes for data to travel from the source to the destination (e.g., 20ms latency in games, hundreds of milliseconds latency in satellite communication);
Reliability: The probability of data transmission without loss or errors (e.g., TCP protocol automatically retransmits lost data);
Bandwidth: The maximum speed that the transmission medium can support (e.g., 1000Mbps bandwidth for a gigabit network cable).