Multi-antenna Transmission and Reception in NR

Introduction

Multi-antenna transmission and reception in 5G New Radio (NR) technology is one of the key technologies that enables higher data rates, improved network capacity, and coverage. It also plays a critical role in ensuring reliable and efficient communication in various use cases such as enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC). This article discusses the technical aspects of multi-antenna transmission and reception in NR.

Background

The basic principle of multi-antenna transmission and reception is to use multiple antennas at the transmitter and receiver sides to exploit spatial diversity, which can be leveraged to improve the quality and reliability of wireless communication. In NR, multi-antenna transmission and reception is achieved through various techniques, such as multiple-input-multiple-output (MIMO), beamforming, and massive MIMO. These techniques differ in terms of the number of antennas used, the type of antennas used, and the signal processing algorithms employed.

MIMO

MIMO is a technique that uses multiple antennas at both the transmitter and receiver sides to increase the capacity and reliability of wireless communication. In MIMO, the same data is transmitted simultaneously from multiple antennas, but each signal experiences a different path due to the propagation environment, resulting in a unique channel response. The receiver can then process these signals to extract the transmitted data. The number of antennas used at both the transmitter and receiver sides determines the order of MIMO, such as 2x2, 4x4, or 8x8 MIMO. The higher the order of MIMO, the greater the spatial diversity and the higher the capacity and reliability of wireless communication.

Beamforming

Beamforming is a technique that uses directional antennas at the transmitter and receiver sides to focus the radio waves in a particular direction. This technique can be used to increase the signal-to-noise ratio (SNR) and reduce interference in a particular direction, which improves the overall quality and reliability of wireless communication. Beamforming can be implemented in two ways: analog beamforming and digital beamforming.

Analog beamforming uses a network of phase shifters to adjust the phase of the radio waves transmitted from each antenna, which creates constructive interference in a particular direction. Analog beamforming is a simple and low-cost technique, but it has limited flexibility and can only create a fixed beam in a particular direction.

Digital beamforming, on the other hand, uses a digital signal processing algorithm to adjust the phase and amplitude of the radio waves transmitted from each antenna, which creates a dynamic beam that can be steered in any direction. Digital beamforming is a more complex and expensive technique, but it offers greater flexibility and can create a dynamic beam that tracks the user's location and movement.

Massive MIMO

Massive MIMO is a technique that uses a large number of antennas at the transmitter and receiver sides to exploit spatial diversity and improve the capacity and reliability of wireless communication. In massive MIMO, hundreds or even thousands of antennas are used at the base station to communicate with multiple users simultaneously. The base station can then use advanced signal processing algorithms to separate the signals from each user, which enables high-capacity and reliable communication.

Massive MIMO also has the ability to reduce interference and improve the energy efficiency of wireless communication. Since massive MIMO uses a large number of antennas, the power of each antenna can be reduced, which reduces the overall power consumption of the system.

Implementation in NR

Multi-antenna transmission and reception is implemented in NR through various techniques such as MIMO, beamforming, and massive MIMO. These techniques are standardized in 3GPP release 15, which specifies the physical layer (PHY) and medium access control (MAC) layer protocols for NR.

In terms of MIMO, NR supports up to 8x8 MIMO, which can be used in both downlink and uplink transmissions. In the downlink, the base station can use multiple antennas to transmit data to a single user, which improves the signal quality and reliability. In the uplink, the user can use multiple antennas to transmit data to the base station, which improves the signal quality and reduces interference.

Beamforming is also an important technique in NR, which is used to improve the coverage and capacity of wireless communication. NR supports both analog and digital beamforming, which can be used in both downlink and uplink transmissions. In the downlink, the base station can use beamforming to focus the radio waves in the direction of the user, which improves the signal quality and reduces interference. In the uplink, the user can use beamforming to focus the radio waves in the direction of the base station, which improves the signal quality and reduces interference.

Finally, massive MIMO is another important technique in NR, which is used to increase the capacity and reliability of wireless communication. NR supports massive MIMO with up to 64 antennas at the base station, which can be used to communicate with multiple users simultaneously. The base station can use advanced signal processing algorithms to separate the signals from each user, which enables high-capacity and reliable communication.

Conclusion

Multi-antenna transmission and reception in NR is a critical technology that enables higher data rates, improved network capacity, and coverage. It plays a key role in ensuring reliable and efficient communication in various use cases such as eMBB, URLLC, and mMTC. NR supports various techniques such as MIMO, beamforming, and massive MIMO, which differ in terms of the number of antennas used, the type of antennas used, and the signal processing algorithms employed. These techniques enable NR to provide high-quality and reliable wireless communication in a wide range of scenarios.