Shulou(Shulou.com)11/24 Report--

In the information age, we rely more and more on mobile phones for work, travel, shopping and entertainment. Especially when away from home, once the mobile phone shows that the battery is low, the document gentleman's heart hangs up, always feeling lack of sense of security.

While the large bandwidth and multi-antenna features of 5G improve the speed experience, it also leads to a significant increase in the power consumption of baseband chips and RF, which makes the power consumption of 5G mobile phones faster, often before the end of the day, but there is little power left.

The easiest way to improve the battery life of a 5G phone is, of course, to increase its battery capacity, but before a breakthrough in battery technology, the phone will be bigger and heavier, a departure from the goal of being thin and portable.

As the saying goes, in addition to increasing battery capacity to improve the battery life of mobile phones, how will 5G break the game on the issue of terminal power saving?

On the one hand, mobile phone manufacturers start with reducing the power consumption of mobile phone screen: automatically adjusting the screen refresh rate and "dark mode", on the other hand, it is to turn on intelligent network selection. The so-called intelligent network choice is to switch between 5G and 4G at any time according to the needs of users, so as to ensure the battery life of the phone. For example:

The above power-saving strategies are essentially: when there is no high-traffic service, such as just checking text messages, automatically turn off the 5G network and use the 4G network to transmit data, thus making the phone more power-efficient.

But not using 5G network to save power for 5G terminals is certainly not the best solution. After all, I bought a more expensive 5G package and bought a more expensive 5G mobile phone. As a result, I was told: let's use 4G! It's not appropriate.

What are we going to do?

In fact, terminal power saving can not only start from the terminal itself, but also the optimization of network configuration on the base station side is also effective.

UAI power saving scheme UAI (UE Assistance Information, user equipment auxiliary information), that is, terminal auxiliary information. Reporting UAI is an accurate and effective method for base stations to obtain terminal requirements.

UAI power saving scheme: in order to reduce its own energy consumption, the terminal reports the expected network configuration to the base station to help the base station better understand the actual situation of each terminal. The base station will adjust the resource allocation according to the recommendations of the terminal in order to help the terminal save power.

UAI is introduced in 3GPP R15 for terminal overheat protection. The significant increase in power consumption of the 5G system makes the terminal easy to overheat. When the terminal detects its own overheating, it will actively report the overheating auxiliary information to the base station, and the base station will adjust the terminal configuration (for example, reducing the bandwidth) according to the auxiliary information to avoid the terminal overheating problem.

In order to further reduce terminal power consumption, 3GPP R16 adds UAI based on energy saving, which is used to assist terminal energy saving. In the process of terminal operation, due to the small amount of business or limited terminal power, we want to save the terminal power as much as possible by reducing the configuration, so report the energy-saving auxiliary information to the base station, and the base station makes targeted adjustments to reduce the terminal energy consumption. The specific process is as follows:

The base station sends the UE capability query message to the terminal.

The terminal replies to the base station, telling it which energy-saving capabilities it supports.

The base station configures different energy-saving configurations for the terminal through the RRC (Radio Resource Control) reconfiguration message.

When the traffic is small or the terminal power is limited, the terminal reports the UAI to the base station and carries the recommended energy-saving configuration.

The base station is adjusted according to the recommended configuration of the terminal to save energy for the terminal.

When energy saving is no longer needed, the terminal reports the UAI to the base station and informs the base station to restore the configuration.

The base station sends a RRC reconfiguration message to restore the terminal configuration and improve the terminal service rate.

What are the energy-saving UAI? How to save energy? In the UAI reported by the terminal to the base station, there is the following information related to the terminal energy consumption.

Overheating auxiliary information: maximum aggregate bandwidth, maximum number of auxiliary carriers, maximum number of MIMO layers.

Energy-saving auxiliary information: DRX (Discontinuous Reception, discontinuous reception) configuration, maximum aggregate bandwidth, maximum number of auxiliary carriers, maximum number of MIMO layers, minimum cross-slot scheduling interval, RRC status.

The energy saving mechanisms of UAI information are as follows:

01. DRX discontinuous reception, that is, the terminal periodically detects and receives PDCCH to reduce the wake-up time of the terminal.

02. The maximum aggregate bandwidth is configured with small bandwidth energy saving BWP (Bandwidth Part, partial bandwidth). When the traffic is small, switch to the smaller bandwidth BWP. Compared with the fixed working in 100MHz large bandwidth, switching to small bandwidth BWP, the sampling frequency is reduced, and the terminal power consumption is also reduced.

03. In the scenario of carrier aggregation with the maximum number of auxiliary carriers, Pcell (main cell) and Scell (secondary cell) can send data to the terminal at the same time to improve the data transmission rate, but when there is no data transmission in Scell, the terminal should continue to monitor, resulting in increased terminal power consumption. Therefore, when the traffic is low, part of the subcarrier can be deactivated to reduce the terminal power consumption.

04. The maximum number of MIMO layers adjusts the number of MIMO antennas to temporarily close the antenna panels that do not need to be used and reduce the number of antennas receiving data.

05. The minimum cross-slot scheduling interval means that the control channel PDCCH and the traffic channel PDSCH are not scheduled in the same time slot. After receiving the PDCCH control signal, the terminal does not decode the service data in the PDSCH immediately, but decodes it after the indicated scheduling interval, so as to save the decoding power consumption when there is no data transmission.

06. The RRC status indicates the energy saving state that the terminal expects to enter. According to the energy saving status reported by the terminal, the base station decides whether to release the terminal to RRC_INACTIVE state or RRC_IDLE state according to its own strategy.

There are three kinds of RRC states in 5G NR terminals: CONNECTED, IDLE and INACTIVE.

CONNECTED: connection mode, the connection is established between the terminal and the base station, the base station and the core network, and the data can be transmitted at any time, but the terminal power consumption is high.

IDLE: in the idle state, the connection between the terminal and the base station, the base station and the core network is cut off, the terminal power consumption is low, but the time delay of switching to the connected state is high.

INACTIVE: deactivated, the connection between the terminal and the base station is cut off, the connection between the base station and the core network is retained, the terminal power consumption is low, if a service arrives, it can be quickly transferred to the connected state.

Conclusion besides UAI,3GPP, many other terminal energy-saving schemes are provided, such as DRX adaptation, maximum MIMO layer adaptation and so on. However, these schemes are initiated actively by the base station side. The advantage of UAI is that the terminal provides its desired energy-saving configuration to the base station, which can be more in line with the actual situation of the terminal, so as to achieve the purpose of energy saving more effectively.

Therefore, with the gradual implementation of UAI energy-saving technology, mobile phones can report energy-saving UAI according to their own business and power consumption, and the base station can adjust the resource allocation for mobile phones to save power according to the energy-saving needs of each phone, and we no longer have to worry about 5G phones consuming more electricity.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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