Data transmission in data communication refers to the complete process of reliably transmitting raw data (text, sensor data, instructions, etc.) from the sending end (such as a computer, sensor, or module) to the receiving end (such as a server, controller, or terminal device) through a specific communication medium (wired/wireless) after a series of processing steps including encoding, transmission, decoding, and verification. The core issue is solving the problems of "how to transmit data, how to transmit it accurately, and how to transmit it stably." This can be broken down into the following key stages and dimensions, explained using both simple analogies and professional details:

I. The Core Prerequisite for Transmission: Data is First "Packaged" (Encoding and Modulation)

Raw data (such as the sensor's temperature value "25℃" or the text "Hello") cannot be directly transmitted through the communication medium and must be processed first:

Encoding: Converting the raw data into binary digital signals (0s and 1s), and then "packaging" it according to protocol rules (such as adding check bits and address bits) – similar to attaching a shipping label (writing the recipient and sender) and adding shockproof packaging when packing a package.

Example: The text "Hello" is first converted to ASCII code (H=72→01001000, and so on), and then encapsulated into data packets conforming to protocols such as TCP/IP and LoRa.

Modulation (wireless/partial wired transmission): Converting binary digital signals into analog/radio frequency signals adapted to the communication medium—for example, in wireless transmission, 0/1 signals are loaded onto VHF/UHF radio waves, much like a courier choosing a "transportation vehicle" (truck, airplane) to adapt to a route.

Example: In VHF radio data transmission, FSK (Frequency Shift Keying) modulation is used, with different frequencies of radio waves representing 0 and 1.

II. Core Carrier of Transmission: Communication Medium ("Transportation Route")

Data is transmitted through media, which fall into two main categories, directly affecting transmission distance, speed, and stability:

Wired Media: Network cables (twisted pair), optical fibers, coaxial cables, etc.—like highways/railways, providing stable transmission and minimal interference.

Example: Network cables transmit Ethernet data, while optical fibers are used for long-distance, high-speed transmission (such as intercity data leased lines).

Wireless Media: Radio waves (VHF/UHF, Bluetooth, LoRa), infrared, satellite signals, etc. – like the sky/ocean, no wiring required, suitable for mobile or remote scenarios.

Example: VHF band (30300MHz) radio waves, relying on their strong diffraction ability, achieve short-to-medium distance data transmission of 550km outdoors.

III. Core Guarantee for Transmission: Reliability Mechanisms ("Preventing Lost or Wrong Transmissions")

Data transmission may be affected by interference (such as radio interference, poor network cable contact), leading to loss or errors. Mechanisms are needed to ensure reliability:

Error Control: The sending end adds a "checksum" (such as CRC check, parity check), and the receiving end verifies it – like a "counterfeit code" on a package, which the recipient checks for integrity.

Example: In LoRa data transmission, CRC32 verification is used; if an error is found, the sending end is required to retransmit.

Retransmission Mechanism: If the receiving end does not receive data or finds an error, it notifies the sending end to retransmit – like a lost package being resent.

Flow control: When the receiving end is busy (e.g., buffer full), it notifies the sending end to pause transmission—similar to asking a courier to delay delivery when the recipient is not home.

IV. Transmission Examples in Real-World Application Scenarios (VHF Radio Data Transmission)

Taking outdoor sensor data transmission as an example, the complete process is as follows:

1. The sensor collects temperature data (raw data: 28℃);

2. The transmitting end (Ebyte VHF module) encodes "28℃" into binary (00011100), adds a check bit and device address, and encapsulates it into a data packet;

3. Through FSK modulation, the data packet is loaded onto a 150MHz (VHF band) radio wave for transmission;

4. The radio wave travels 510km through the air, and the receiving end (VHF module) receives the signal;

5. The receiving end demodulates the signal, extracts the data packet, and verifies the data's accuracy using the check bit;

6. Decoding yields "28℃," which is then transmitted to the server or controller, completing the transmission.