How 5G-Advanced takes radio network performance to the next level
Six months ago, Nokia’s Chief Technology and Strategy Officer, Nishant Batra, laid out our ambitious vision for 5G-Advanced, focusing on what we are calling “the four E’s”: experience, expansion, extension and operational excellence. Since then, this vision has been moving towards reality, starting with 3GPP’s approval in December of the main RAN feature set for 5G-Advanced in Release 18, as outlined by my colleague Antti Toskala. Now, 3GPP has taken a second step, by approving the set of radio performance features to complete the overall RAN package for Release 18.
Often, these radio performance features are somewhat hidden behind the scenes of the main RAN features, but that makes them no less important. So, let’s explore them and see how they contribute to the realization of the full 5G-Advanced vision.
The radio frequency (RF) performance of 5G-Advanced equipment (network and device) is fundamental to the network’s ability to deliver its expected experience, as well as expanding the coverage and providing excellence in operation. Release 18 will therefore incorporate several new requirements for better RF performance of 5G-Advanced equipment.
Let’s suppose that the receiver and transmitter performance of 5G-Advanced devices will improve as implementation knowhow develops. Then, in due time, the receiver and transmitter performance of 5G-Advanced devices should significantly exceed the minimum required levels for the first 5G devices. If the network can know about the RF performance of each 5G-Advanced device, it can take this into account when configuring features such as carrier aggregation and thereby translate the improved technical performance directly into a visible improvement in experience for the user. This will also provide an incentive to device manufacturers to raise the RF performance of their devices!
For example, if the network is aware that a device’s receiver sensitivity is enhanced in certain scenarios, it may be able to configure carrier aggregation for that device, giving dramatically higher downlink data rates, without worrying that the gains will be eroded by effects such as harmonics from uplink transmissions. Similar considerations apply to the transmitters, so we expect network awareness of device performance to be extended in the future to ensure that uplink data rates can also benefit from increased configuration of carrier aggregation, without concerns of degradation due to effects such as intermodulation distortion.
Further RF enhancements in Release 18 focus on defining minimum performance levels for devices with larger numbers of antennas, up to eight receive antennas for the downlink and four transmit antennas for the uplink. These are particularly likely to be used by devices for fixed wireless access.
5G broke new ground for mobile communication systems by extending the range of operating frequencies to encompass mmWave, known in the jargon as “Frequency Range 2” (FR2). mmWave frequencies have unique RF properties that require special handling in the devices. In particular, mmWave signals tend to be more directional than lower mobile communication frequencies, and this directionality can be exploited by means of beamforming. In order for beamforming to work well, is it is important that a device matches the uplink transmission beams with the downlink reception beams – a feature known as beam correspondence. If a device performs beam correspondence accurately right from the start, the process of connecting to the network and transmitting small data packets will be noticeably accelerated. This will be particularly valuable for transmission of reports from monitoring devices and sensors. Led by Nokia’s cutting-edge research, Release 18 will set minimum standards for these important aspects of beam correspondence for mmWave operation, as well as defining the expected performance of devices with multiple antenna panels oriented in different directions to receive multiple beams simultaneously.
RRM and demodulation requirements
To achieve better user experience, 5G-Advanced devices must also be capable of reacting more quickly when a data burst commences, making faster use of the wide bandwidths available at mmWave frequencies by speeding up measurements and reducing activation delays for new cells. New Radio Resource Management (RRM) performance requirements will be introduced in Release 18 to ensure that network operators can get the most out of all their spectrum, in both mmWave and lower bands.
Apart from RF and RRM requirements, demodulation performance requirements specify how well the devices can process and decode the data they receive, depending on the prevailing radio conditions. What network operators really want to know is the application layer throughput they can expect from a device under given conditions, and new requirements will be introduced in Release 18 to make this throughput directly measurable.
One particularly important scenario for which new demodulation requirements will be introduced in 5G-Advanced is multi-user MIMO, where the signal that a user receives may be subject to interference from a signal directed to another user. In such a case, it is important that devices are able to mitigate sufficiently the effect of the interference in order to avoid it degrading the achievable throughput. New multi-user MIMO demodulation requirements are planned for this scenario, setting minimum performance levels.
An important area of extension for 5G-Advanced is railway communication. Currently dependent on 2G-based systems (e.g., GSM-R), critical communications for railway operation and signaling are about to leapfrog direct to 5G-Advanced to take advantage of the ultra-reliable, low latency and high data rate quality of service that it supports. 5G-Advanced will facilitate automatic train control and protection, together with real-time video, which will open new possibilities in remote operation of railway networks. Nokia, already a global leader in GSM-R systems, is playing a leading role in 3GPP to adapt 5G-Advanced to operate in spectrum bandwidths smaller than 5 MHz. This is needed to migrate from GSM-R to 5G-Advanced within the dedicated spectrum that is set aside for railway operation. The necessary adaptations will be minimal, avoiding impacts on device hardware so that devices for railways can build easily on the established 5G ecosystem of products.
But it is not enough for the rail operators to be able to use 5G-Advanced; the passengers, too, need to benefit from the full 5G-Advanced experience, even under the challenging conditions of high-speed travel. To support the needs of large numbers of passengers using high data rate services simultaneously, Release 18 will also extend the performance requirements for devices with high mobility.
From vision to reality
Improved RF, RRM and demodulation performance in 5G-Advanced devices will be a key enabler for the improved user experience for exciting new applications such as mobile XR. Additionally, the extension of 5G-Advanced into new domains, such as critical communications for railway operation, will be enabled by careful adaptations of 5G at the radio level. And many more hi-tech enhancements will be hidden under the skin of 5G-Advanced: users may not be directly aware of them, but their lives will most certainly be impacted by them.