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

I don't know if everyone, like the document master, was told to bring a three-piece set: keys, wallets and ID cards when they were young.

Now, people can take the same thing with them when they go out: mobile phones. If you want to add one more thing, it must be portable battery.

In the 5G era, we have a 5G smartphone, which can surf the Internet, check information, navigate, work, collect payments, shop, watch videos, play games and chat anytime and anywhere. It can be said that "the mobile phone is in hand, I have the world".

But so many high-speed applications also mean that the phone's battery is running! After going out, the biggest fear is that before people get home, the power of the mobile phone will be gone.

Whether the mobile phone saves power has become an important factor affecting the user experience and whether the 5G service is enabled or not. In order to improve the battery life of 5G mobile phones, the industry starts from application, operating system, screen, chip, larger capacity battery and so on.

As the maker of the 5G standard, 3GPP naturally also developed a series of features to enable 5G terminal devices (including 5G mobile phones) to save energy and power.

So, in the frozen version of R15~R17, what features does 3GPP provide for 5G terminal power savings? Mr. documentation will come one by one for you.

In R15 version, there is no special work item for terminal power saving, but it already has the characteristics related to terminal power saving: discontinuous reception (DRX) and partial bandwidth adaptation.

Although the mobile phone is fun, you don't play with it all the time, but stop from time to time to give your eyes a rest and give your phone a "rest". Therefore, in practical application, our terminal has data transmission for a period of time, and there is no data transmission for the next period of time. So is it feasible for the terminal to take a nap from time to time and not to be in a "highly focused" state of work all the time? With this in mind, 3GPP designed the discontinuous reception feature.

Discontinuous reception (Discontinuous Reception,DRX): the terminal is divided into DRX cycles, in which there are awakening periods and dormant periods. When the awakening period comes, the terminal wakes up to check whether it has its own task; at the end of the awakening period, if it does not receive new data transmission instructions, it goes to sleep. Because the terminal is no longer in the wake-up state all the time, the power consumption is reduced.

Partial bandwidth (Bandwidth Part,BWP) refers to the division of some small bandwidths on the basis of full bandwidth.

Partial bandwidth adaptation: when the amount of data is large, the terminal works on the large BWP bandwidth; when the amount of data is small, the terminal switches to the small BWP bandwidth. When working on a small bandwidth, the amount of data processed by the terminal is greatly reduced, which can play the role of power saving.

Give an example.

After the terminal is connected to the network, multiple BWP can be configured, such as BWP1, BWP2 and BWP3 in the figure below. With the change of time, the business handled by the terminal is changing, and the BWP of the terminal will be switched adaptively, thus saving power.

What is the power-saving effect of BWP adaptation?

Compared with 20 MHz and 100 MHz, the power-saving effects evaluated by different manufacturers are different, but they all have a power-saving effect of 20% to 30%. The document thinks the power-saving effect is quite good!

R16 version, began to pay attention to power saving, specially set up a work item "UE Power Saving" to study terminal power saving technology, from many aspects to study terminal power saving. This feature saves some, that technology saves some, all aspects add up, the power-saving effect is greatly improved.

In the R15 version, the terminal wakes up whenever it comes to the DRX wake-up period, with or without data transmission. If the terminal does not have to wake up even when there is no data transmission, wouldn't it be possible to further save energy? Therefore, in the R16 version, the DRX adaptive (also known as WUS,Wake-up Signaling) feature was introduced.

DRX adaptation: before the arrival of each DRX cycle, send a WUS signal to the terminal to tell the terminal in advance whether it needs to wake up in the next awakening period. If the WUS indicates that there is no need to wake up, the terminal remains dormant during the DRX wake-up period. This further reduces the time it takes for the terminal to wake up, thus further saving power.

Cross-slot scheduling: downlink PDCCH and PDSCH are not scheduled in the same time slot. After receiving the PDCCH control signal, the terminal decodes the service data in the PDSCH after a certain interval, instead of decoding immediately.

For the terminal, it means that the work can be done slowly, and there is no need to cache the PDSCH if you are not in a hurry. The terminal can selectively turn off some radio frequency and baseband modules, so as to achieve the effect of power saving.

MIMO technology can greatly improve the efficiency of data transmission, but it also brings more power consumption.

Maximum MIMO layer adaptation means that the maximum number of MIMO layers can be adjusted dynamically. In other words, in some cases, the terminal can turn off part of the receiver and reduce the power consumption of the terminal.

Combined with the characteristic of partial bandwidth adaptation, when the terminal works on a smaller BWP, the number of uplink and downlink can be reduced because of the low requirement for the amount of data. In this case, the power-saving effect is more powerful.

The 5G NR terminal has three RRC (Radio Resource Control) states: connected, idle, and inactive.

Connection: a connection has been established between the terminal and the base station, the base station and the core network, which can transmit data at any time, but the terminal power consumption is high.

Idle: 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 it can not do business, and the delay of switching to the connected state is high.

Inactive: 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.

If the terminal needs to process a small amount of data, or does not need to send data, it actively asks to exit the connection state and enter the inactive state or idle state, which will certainly reduce power consumption and save power.

In the auxiliary carrier scenario, when there are multiple active carriers, the main cell (Pcell) and the auxiliary cell (Scell) can send data to the terminal at the same time to improve the data transmission rate.

But if there is no data transmission in the auxiliary district, and the terminal should continue to monitor, it is useless work.

Therefore, the sleep characteristic of the sub-cell is designed: if a sub-cell has no data, it will enter the sleep, thus reducing the power consumption.

RRM (Radio Resource Management, Radio Resource Management) measurement is mainly used for cell reselection. In theory, the terminal needs high-frequency RRM measurement in the connected state, but it is not necessary to maintain high-frequency RRM measurement in idle or inactive state, which is a complete waste of energy consumption.

Idle state and inactive state reduce RRM measurement: when the terminal is in idle or inactive state, reduce the frequency of RRM measurement, not so dense, the terminal can achieve the effect of power saving.

During the operation of the terminal, it may be due to small traffic or limited terminal power, so we want to save the terminal power as much as possible by reducing the configuration, so we report the energy saving auxiliary information (UE Assistance Information,UAI) to the base station. The base station makes targeted adjustments according to the information reported by the terminal to reduce the energy consumption of the terminal. 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.

Based on the R16 version, the R17 version pays more attention to energy saving and electricity saving, and sets up a special work item "UE Power Saveing Enhancements" to further enhance the terminal power saving technology.

In each paging cycle, the terminal needs to monitor whether there is a paging to itself when its own paging time (Paging Occasion,PO) arrives. Terminals belonging to the same paging time are assigned to the same group. When the time span is one or more PO, the network side uses a downlink control message to wake up one or more groups of terminals in advance to listen for the paging message.

Comparing a terminal to a worker means that every worker has a schedule to take care of the task. As soon as the time is up, I will go to the playground to listen to the roll call, take the task when it is called, and go back to rest before it is called. For workers who have the same schedule, they will be assigned to the same group, and as soon as the time is up, the whole group of workers will be informed to attend the roll call. For those workers who ran to the playground on time but didn't get the task, isn't this a wasted trip? If someone can find out the news well, wouldn't it be better for the workers with the task to go to the playground to get the job, and the workers without the task to have a good rest? According to this idea, a feature is designed: paging early wake-up indication (Early Paging Indication,EPI).

Before the terminal's PO arrives, the EPI indication informs the terminal whether there is a page for the terminal in the upcoming PO. If so, the idle terminal will wake up and establish a connection with the network side; if not, the terminal does not have to wake up, thus saving power.

In addition to informing whether there is a paging to the terminal, the EPI can also carry the subpacket information and further divide the terminal into a subgroup according to the paging rate, so as to avoid frequent awakening of the subgroup terminal with low paging rate.

Compared with the basic paging process, EPI can save energy by 17% to 34%. If EPI has additional subgroup information, you can save an additional 10% of your energy.

TRS,Tracking Reference Signal, track the reference signal. CSI-RS,Channel State Information Reference Signal, channel state information reference signal.

According to the traditional process, idle and inactive terminals need to monitor Paging before receiving SSB messages to select the appropriate beam, and then map to PO to monitor paging according to the SSB beam mapping relationship. The whole process of monitoring the reception of paging messages lasts for a long time, so that the terminal will be awakened for a long time and consume more power.

With the TRS / CSI-RS feature, the base station sends a bitmap through DCI or Paging DCI to tell the terminal whether there is a resource set of valid TRS / CSI-RS reference signals currently configured. The terminal obtains the reference signal to decode the paging message according to TRS / CSI-RS, no longer listens to the Pageing message, and shortens the time for the terminal to be awakened, thus achieving the purpose of power saving.

SSSG (Search Space Set Group) refers to the search space collection group. The network groups different SS search spaces, and the monitoring density of different groups is different.

Enhanced SSSG Switching: dynamically adjusts the search space collection group of the terminal according to the amount of data of the terminal. When the amount of terminal data is large, the terminal switches to the group with high PDCCH snooping density; when the terminal data is small, the terminal switches to the group with low PDCCH snooping density, so as to reduce the PDCCH snooping density of the terminal. If the total number of terminal monitoring is reduced, it will naturally save more electricity.

PDCCH Skipping: skip some PDCCH demodulation.

When there is no data transmission, the network side will notify the terminal, do not carry out PDCCH monitoring, and then carry out PDCCH monitoring when there is data transmission. The network side uses RRC configuration to tell the terminal how long the PDCCH demodulation should be skipped.

With the rapid development of modern communication technology, where there is demand, there are a lot of manpower to overcome difficult problems and meet the demand. In places we can not see, various power-saving technologies are quietly upgrading, and the power-saving effect of mobile phones will become more and more powerful. Science and technology are still making continuous progress, and Mr. documentation is looking forward to the future with you!

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

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