Mobile Air Interface

- Overview

Mobile air interface technology is the wireless connection between a mobile device and a base station, defining how data is transmitted over the radio link. 

It involves both the physical and data link layers of the OSI model and specifies the methods for transmitting information, such as frequency, channel bandwidth, and modulation schemes. 

Technologies like LTE, 5G NR, and Wi-Fi have their own specific air interface standards, often developed by industry bodies like the 3GPP, though some methods can be proprietary. 

- How Mobile Air Interface works

• Communication link: The air interface is the radio-frequency connection between a device (like a smartphone) and the network's base station or cell tower.
• Data transmission: It is the technology that governs how information is sent over the air between the base station and the mobile unit.
• Handover: As a mobile user moves, the device connects to different base stations, causing the active link to change periodically.
• Standards: Most air interface technologies are defined by standards created by multinational bodies, ensuring interoperability between different devices and networks.

- Key Aspects and Technologies

1. Physical and data link layers: The air interface encompasses layers 1 (physical) and 2 (data link) of the OSI model.
2. Modulation schemes: It specifies how data is modulated for transmission. Examples include:

• OFDMA: Used in LTE and 5G, it divides the signal into many sub-channels to increase efficiency.
• CDMA: Used in some earlier cellular networks, it spreads the signal across a wider frequency band.
• TDMA: Used in GSM, it divides the channel into time slots.

3. MIMO: Multiple-Input Multiple-Output uses multiple antennas to increase data throughput and range, and is a key component of modern air interface solutions. 

4. Examples of standards:

• 5G NR (New Radio): The air interface standard for 5G technology.
• LTE (Long-Term Evolution): A 4G standard that uses OFDMA.
• Wi-Fi: Based on IEEE 802.11 standards for local area wireless networks.

- Proprietary vs. Standard

While many air interfaces are defined by public standards, some companies have developed proprietary methods whose technical details are not publicly available.

[More to come ...]