Mobile Air Interface and Mobile Backhaul

• Function: It transports data between the Radio Access Network (RAN) and the core network, ensuring data is sent to and from the central network for processing and distribution.
• Importance: It's essential for the reliability, speed, and capacity of the mobile network, especially for 5G, as it handles the high volumes of data from many cell sites.

• Fiber optic: Fiber backhaul is a common, high-capacity solution for connecting sites to the core network.
• Microwave radio: Used for point-to-point and point-to-multipoint connections, which can be implemented wirelessly.
• DSL variants: Includes technologies like ADSL, VDSL, and SHDSL, which use existing telephone lines.
• Ethernet: A widely used standard for network connections that can be used for backhaul.
• Other interfaces: Other methods like PDH, SDH/SONET, and VoIP over IP networks are also used. 

Please refer to the following for more information:

• Wikipedia: Air Interface
• Wikipedia: Backhaul

- Mobile Air Interface Technology

The air interface is the radio link between a mobile device and a base station in wireless communication, encompassing the physical and data link layers of the OSI model. 

It defines the technology for wireless data transmission, including the specific radio frequencies, modulation schemes, and channel bandwidth. 

While many air interface technologies are standardized through international bodies, some proprietary methods remain.

In cellular telephone communications, the air interface is the radio-frequency portion of the circuit between the cellular phone set or wireless modem (usually portable or mobile) and the active base station. As a subscriber moves from one cell to another in the system, the active base station changes periodically.

The air interface technology specifies the method for transmitting information over the air between base stations and mobile units. Most air interface technologies are specified in standards that are agreed upon by multinational bodies comprising representatives in the wireless industry. 

Some air interface methods, however, remain proprietary with certain companies and details of their operation may or may not be publicly accessible.

An air interface is the radio frequency portion of a mobile network that connects a user's device to the nearest base station, with the connection handled by a technology like 5G New Radio (NR). 

5G NR is the global standard for 5G's air interface, designed for higher speeds and lower latency to support a wider range of services. 

Key concepts: 

• Air Interface: The wireless, radio frequency connection between a mobile device (like a smartphone) and the network's base station.
• Handoff: The process of a user's active connection being transferred from one base station to another as they move.
• 5G New Radio (5G NR): The specific radio access technology developed by 3GPP for 5G networks, providing the air interface for 5G services.
• Radio Access Technology (RAT): The overall term for the technology used for the air interface. Examples include 5G NR, 4G LTE, Wi-Fi, and Bluetooth.
• Key features of 5G NR: It is designed for enhanced connectivity, higher data rates, lower latency, and greater flexibility to support a diverse set of applications and devices.

The mobile air interface is the wireless radio link between a device and a base station, while mobile backhaul is the wired or wireless network that connects the base station to the core network. 

For 5G, these technologies include using some of the air interface spectrum for backhaul (Integrated Access and Backhaul or IAB), fiber optic cables, and advanced wireless microwave systems. 

6G is expected to evolve these concepts with even higher frequencies and more intelligent, AI-native air interfaces that can dynamically optimize their design for different applications and environments.

A. Mobile Air Interface:

1. 5G: The air interface uses spectrum in bands up to 300 GHz, with 5G New Radio (NR) as the primary technology. Technologies like beamforming are critical for efficient use of these high-frequency bands.

2. 6G: 6G is predicted to operate at even higher frequencies, potentially up to 1 THz, requiring significant innovations in radio technology.

• AI-native design: One major area of research is using machine learning (ML) to create an "AI-native" air interface that can be dynamically optimized for specific tasks, hardware, and environments, moving beyond traditional fixed protocols. 
• Evolving waveform: While some propose using 5G waveforms, others suggest that this could limit innovation. The physical layer may see disruptive changes rather than just incremental improvements.

B. Mobile Backhaul:

1. 5G: The backhaul needs to support high speeds and low latency to handle 5G's data demands. 

• Integrated Access and Backhaul (IAB): A 5G technology that re-purposes the air interface spectrum for wireless backhaul to reduce costs and speed up deployment, especially for small cells.
• Fiber and wireless: Fiber optic cables are a dominant backhaul technology, but high-demand wireless solutions, such as E/V band microwave systems, are also seeing increased use to meet 5G capacity requirements.

2. 6G: The backhaul network will need to be even more advanced to meet 6G's demanding requirements.

• Higher speed wireless: Advancements in sub-THz wireless technology are expected to offer an over-the-air backhaul solution that is both fast and agile, potentially complementing or even outperforming fiber in some scenarios.
• Mesh and intelligence: 5G's need for intelligent, high-capacity mesh backhaul networks is likely to continue, with 6G building on this by integrating network intelligence and more flexible architectures.

[More to come ...]