Mid-Band Spectrum and the Co-Existence with Radio Altimeters

Last updated on Mar 15, 2023

Introduction

Mid-band spectrum refers to the range of radio frequencies between 3.7 GHz and 24 GHz, which is a critical part of the radio spectrum used for various wireless communications technologies, including 5G. The mid-band spectrum has the advantage of providing high data rates and excellent coverage area, making it ideal for mobile communications. However, the coexistence of mid-band spectrum and radio altimeters has raised concerns, as they operate in adjacent frequencies, which could cause interference. In this article, we will discuss technically the mid-band spectrum and its coexistence with radio altimeters.

Mid-band Spectrum

The mid-band spectrum refers to a range of radio frequencies between 3.7 GHz and 24 GHz. It is also known as the C-band and is one of the most important frequency ranges for 5G networks. The mid-band spectrum has the advantage of providing high data rates, excellent coverage area, and better penetration through obstacles than the high-band spectrum. The mid-band spectrum is also used for other wireless communication technologies such as satellite communications, fixed wireless, and microwave links.

The mid-band spectrum is divided into three sub-bands:

Low Mid-band: This sub-band ranges from 3.7 GHz to 6 GHz and is used for satellite and fixed wireless communications.
Mid Mid-band: This sub-band ranges from 6 GHz to 14 GHz and is used for point-to-point microwave links and mobile wireless communications.
High Mid-band: This sub-band ranges from 14 GHz to 24 GHz and is used for mobile wireless communications, satellite communications, and microwave links.

The mid-band spectrum has several advantages over the high-band spectrum, including better coverage area and better penetration through obstacles. However, the mid-band spectrum also has some disadvantages compared to the low-band spectrum, such as lower coverage area and lower penetration through obstacles.

Radio Altimeters

A radio altimeter is a device that measures the altitude of an aircraft above the ground using radio waves. The radio altimeter transmits a signal towards the ground and receives the reflected signal. By measuring the time delay between the transmitted and received signals, the radio altimeter can determine the altitude of the aircraft.

Radio altimeters operate in the frequency range between 4.2 GHz and 4.4 GHz, which is very close to the lower end of the mid-band spectrum. The radio altimeter band is divided into two parts:

Main radio altimeter band: This band ranges from 4.2 GHz to 4.4 GHz and is used for radio altimeters.
Secondary radio altimeter band: This band ranges from 4.4 GHz to 4.5 GHz and is used as a backup for radio altimeters.

Coexistence of Mid-band Spectrum and Radio Altimeters

The coexistence of mid-band spectrum and radio altimeters has raised concerns as they operate in adjacent frequencies, which could cause interference. The interference could lead to inaccurate altitude measurements, which could be dangerous for aircraft during takeoff and landing. To ensure that mid-band spectrum and radio altimeters can coexist, the International Civil Aviation Organization (ICAO) has established some guidelines for mid-band spectrum use.

The ICAO guidelines require that the use of mid-band spectrum should not interfere with the operation of radio altimeters. The guidelines require that the use of mid-band spectrum should not cause more than 1% of the radio altimeter errors. The guidelines also require that mid-band spectrum users should coordinate with radio altimeter users to avoid interference.

To ensure compliance with the ICAO guidelines, mid-band spectrum users are required to conduct tests to measure the impact of their operations on radio altimeters. The tests measure the amount of interference caused by mid-band spectrum users and determine whether the interference is within

the limits established by the ICAO guidelines. If the interference is within the limits, the mid-band spectrum user can operate without causing interference to radio altimeters.

If the interference exceeds the limits, mid-band spectrum users are required to take measures to reduce the interference. These measures may include reducing the power of the mid-band spectrum signals or modifying the antenna pattern. Mid-band spectrum users may also be required to change their operating frequency to avoid interfering with radio altimeters.

The coexistence of mid-band spectrum and radio altimeters is critical to ensure the safety of aircraft during takeoff and landing. The ICAO guidelines and testing procedures help to ensure that mid-band spectrum and radio altimeters can coexist without causing interference.

Conclusion

In conclusion, the mid-band spectrum is a critical part of the radio spectrum used for various wireless communication technologies, including 5G. The mid-band spectrum provides high data rates and excellent coverage area, making it ideal for mobile communications. However, the coexistence of mid-band spectrum and radio altimeters has raised concerns as they operate in adjacent frequencies, which could cause interference.

The International Civil Aviation Organization (ICAO) has established guidelines for the use of mid-band spectrum to ensure that it does not interfere with radio altimeters. The guidelines require mid-band spectrum users to conduct tests to measure the impact of their operations on radio altimeters and take measures to reduce interference if necessary.

The coexistence of mid-band spectrum and radio altimeters is critical to ensure the safety of aircraft during takeoff and landing. The guidelines and testing procedures established by the ICAO help to ensure that mid-band spectrum and radio altimeters can coexist without causing interference.