WO2021073709A1

WO2021073709A1 - Optimizing of signaling for estimating a quality of a channel

Info

Publication number: WO2021073709A1
Application number: PCT/EP2019/077750
Authority: WO
Inventors: Silvio MANDELLI; Jafar MOHAMMADI; Thorsten Wild
Original assignee: Nokia Technologies Oy
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2021-04-22

Abstract

It is provided a method, comprising detecting at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal; determining a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal based on the at least one of the movement state, the orientation state, and the predicted traffic; informing the base station on the sounding demand.

Description

Optimizing of signaling for estimating a quality of a channel

Field of the invention

The present invention relates to optimizing of signaling for estimating a quality of a channel. For example, it may be related to optimizing transmission of at least one of SRS, CQI, PMI, and Rl.

Abbreviations

3GPP 3^rd Generation Partnership Project

3G / 4G / 5G 3^rd / 4^th / 5^th Generation

AP Access Point

CQI Channel Quality Indicator

CSI Channel State Information

CSI-RS Channel State information - Reference Signal gNB next Generation Node B

GNSS Global Navigation Satellite System

GPS Global Positioning System

HCMI Highly Compressed Movement Information

IEEE Institute of Electrical and Electronics Engineers

IMU Inertial Measurement Unit

KaLi Kinetic and Localization information

KNN K- nearest neighbors

KPI Key Performance indicators

LAN Local Area Network

LTE Long Term Evolution

MIMO Multi-input Multi-output

MTC Machine-type Communication

NR New Radio

PMI Precoding Matrix Indicator

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

QoS Quality of Service

Rl Rank Indicator

RNN Recurrent Neural Network SD Sounding Demand

SRS Sounding Reference Signal

TDD Time Division Duplex

TR Technical Report

TS Technical Specification

UE User Equipment

UL Uplink

URLLC Ultra-reliable low latency communication

WiFi Wireless Fidelity

WLAN Wireless Local Area Network

Background of the invention

Precoding/Beamforming in massive MIMO has become an enabling technology for next generations of cellular systems. To benefit from the advantages of precoding/beamforming and Massive MIMO, accurate channel state information (CSI) is required at the transmit side (e.g. to mitigate inter-user interference in multiuser (MU)-MIMO transmission and, thus, to achieve high spectral efficiency). To follow the channel’s rapid fluctuations an up-to-date CSI is recommendable. Therefore, the UE periodically sounds the channel in the uplink (exploiting reciprocity in a TDD system). The interval of this sounding reference signal depends on the channel statistics and is adjusted usually by the base station (gNB in the 3GPP NR case). An accurate up-to-date CSI increases the overall performance; however, it requires frequent SRS transmissions that increase overhead and may impose a limit to system capacity to support many UEs with many antennas.

Another way to obtain CSI (e.g. for MIMO) is to transmit one or more channel state information reference signals (CSI-RS) over the downlink, and the UE periodically sends back channel quality indicator (CQI) and, if applicable, precoding matrix indicator (PMI) and/or rank indicator (Rl).

The periodicity in which UE transmits SRS is an important factor. If it is transmitted rarely, then the CSI information may be outdated. On the other hand, too frequent transmissions waste sounding resources and drain the battery on the UE. Finding the optimal periods of transmission of SRS in the statistical sense requires accurate modelling of the channel. Most of the research that has been done on finding optimal intervals for SRS updates rely on simple statistical models for the channel [2] In [1] the authors showed that the use of outdated CSI information can still achieve a certain throughput. On an attempt to reduce the overhead of CSI feedback a compression technique was investigated by Xie et al. [2]

One of the papers that directly considered the overhead of SRS is [3]. They have concluded that implicit sounding could, in certain conditions, outperform explicit sounding. However, implicit sounding requires huge computation burden. The standardized sounding in IEEE 802.11ac, LTE, and the proposed ones for 5G are explicit [6] [7]. Therefore, the problem narrows down to designing the compression methods for CSI feedback and the optimal interval designing. Theoretical and practical results focus on the statistics of the channel to find the frequency of required updates. For instance, [4] assumed the Rayleigh block-fading channel. In [5] extensive experimental analysis has been carried out to show the sensitivity of several types of wireless channels to long or short intervals of SRS updates. They have further proposed a heuristic method that dynamically changes the SRS intervals based on the Doppler spectrum profile estimated from the CSI feedback at the gNB.

The methods above either rely purely on statistical characteristics of the wireless channel or propose methods based on the previous observations of channel and control the intervals of SRS dynamically.

References:

[1] A. Adhikary, H. C. Papadopoulos, S. A. Ramprashad, and G. Caire, "Multi-user MIMO with outdated CSI: training, feedback and scheduling," in 49th Annual Allerton Conference on Communication,

[2] X. Xie, X. Zhang, and K. Sundaresan, "Adaptive feedback compression for MIMO networks," in Proc. of the 19th Annual International Conference on Mobile Computing & Networking, Miami, USA, 2013, pp. 477-488.

[3] E. Perahia and R. Stacey, Next generation wireless LANs: 802.11 n and 802.11 ac: Cambridge University Press, 2013.

[4] L. Zhang, L. Song, M. Ma, and B. Jiao, "On the Minimum Differential Feedback for Time- Correlated MIMO Rayleigh Block-Fading Channels," IEEE Trans on Commun., vol. 60, pp. 411-420, 2012

[5] X. Ma, J. Wang, V. Marojevic, J. H. Reed, and Q. Gao, “Dynamic sounding for multi-user MIMO in wireless Ians,” pp. 135-144, 2017.

[6] 3gpp TS 38.211 [7] 3gpp TS 38.213

[8]: https://stackoverflow.com/questions/14574879/how-to-detect-movement-of-an-android- device

[9]: https://developer.android.com/guide/topics/sensors/sensors_motion

Summary of the invention

It is an object of the present invention to improve the prior art.

According to a first aspect of the invention, there is provided an apparatus, comprising means for detecting configured to detect at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal; means for determining configured to determine a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal based on the at least one of the movement state, the orientation state, and the predicted traffic; means for informing configured to inform the base station on the sounding demand.

According to a second aspect of the invention, there is provided an apparatus, comprising means for monitoring configured to monitor if a base station receives an indication of a sounding demand from a terminal; means for determining configured to determine a sounding period based on the sounding demand if the base station receives the indication of the sounding demand; means for instructing configured to instruct at least one of the terminal and the base station to transmit a sounding signal for estimating a quality of a channel between the base station and the terminal periodically with the determined sounding period.

According to a third aspect of the invention, there is provided an apparatus, comprising means for monitoring configured to monitor if a base station receives an indication of a sounding demand from a terminal; means for estimating configured to estimate at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand if the base station receives the indication of the sounding demand.

According to a fourth aspect of the invention, there is provided a method, comprising detecting at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal; determining a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal based on the at least one of the movement state, the orientation state, and the predicted traffic; informing the base station on the sounding demand.

According to a fifth aspect of the invention, there is provided a method, comprising monitoring if a base station receives an indication of a sounding demand from a terminal; determining a sounding period based on the sounding demand if the base station receives the indication of the sounding demand; instructing at least one of the terminal and the base station to transmit a sounding signal for estimating a quality of a channel between the base station and the terminal periodically with the determined sounding period.

According to a sixth aspect of the invention, there is provided a method, comprising monitoring if a base station receives an indication of a sounding demand from a terminal; estimating at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand if the base station receives the indication of the sounding demand.

Each of the methods of the fourth to sixth aspects may be a method of optimizing signaling for estimating a quality of a channel.

According to a seventh aspect of the invention, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any of the fourth to sixth aspects. The computer program product may be embodied as a computer-readable medium or directly loadable into a computer.

According to some embodiments of the invention, at least one of the following advantages may be achieved:

• frequency of transmissions for estimating a channel quality is optimized;

• Waste of transmission resources maybe avoided;

• More efficient use of radio resources may be achieved;

• Battery consumption at UE may be reduced;

• No need for additional hardware;

• Hardly any latency of movement state determination;

• High reliability. It is to be understood that any of the above modifications can be applied singly or in combination to the respective aspects to which they refer, unless they are explicitly stated as excluding alternatives.

Brief description of the drawings

Further details, features, objects, and advantages are apparent from the following detailed description of the preferred embodiments of the present invention which is to be taken in conjunction with the appended drawings, wherein:

Fig. 1 shows a signaling scheme (message flow) according to some example embodiments of the invention;

Fig. 2 illustrates an example of a classifier using RNN that makes decisions on the KaLi values according to some example embodiments of the invention;

Fig. 3 shows an apparatus according to an example embodiment of the invention;

Fig. 4 shows a method according to an example embodiment of the invention;

Fig. 5 shows an apparatus according to an example embodiment of the invention;

Fig. 6 shows a method according to an example embodiment of the invention;

Fig. 7 shows an apparatus according to an example embodiment of the invention;

Fig. 8 shows a method according to an example embodiment of the invention; and Fig. 9 shows an apparatus according to an example embodiment of the invention.

Detailed description of certain embodiments

Herein below, certain embodiments of the present invention are described in detail with reference to the accompanying drawings, wherein the features of the embodiments can be freely combined with each other unless otherwise described. However, it is to be expressly understood that the description of certain embodiments is given by way of example only, and that it is by no way intended to be understood as limiting the invention to the disclosed details.

Moreover, it is to be understood that the apparatus is configured to perform the corresponding method, although in some cases only the apparatus or only the method are described.

Users usually do not move that much on long time intervals, e.g. during working office hours, during sleep, or at home. Thus they do not need high periodicity of CSI updates during that time. When such a user suddenly starts to move, the CSI update rate should be increased to sustain the spectral efficiency and avoid block errors. In addition, avoiding block errors is especially desirable to increase performance of ultra-reliable low latency communication (URLLC) which is one of the important 5G and beyond use cases.

In order to determine the frequency of SRS transmissions, relying solely on the statistics of the channel (as in the prior art), one cannot capture the user’s sudden movement. It also does not reflect the long unchanged status of the channel that happens when the UE’s location is substantially static. None of the methods of the above cited prior art use the information available locally at the UE side to determine SRS allocation.

According to some example embodiments of the invention, the SRS allocation (in particular: the frequency of SRS transmission) is optimized by UE direct cooperation. Namely, the UE actively supports the gNB to make proper signalling allocation.

Namely, according to some example embodiments of the invention, a UE may actively compute its “Sounding Demand” (SD), and share it with its connected gNB. This procedure requires a new signalling from the UE to the gNB that contains this SD information. Preferably, the new signalling is standardized, e.g. by 3GPP. The gNB exploits the information that UE has sent as an input in an enhanced algorithm that computes an optimized frequency of SRS transmission and frequency resources dedication for SRS. The algorithm may use the same input as conventional algorithms and additionally the SD information for determining the frequency of SRS transmission and the RF frequency resources for SRS.

Fig. 1 shows a message exchange according to some example embodiments of the invention. The UE determines SD and signals the determined SD to gNB. Based on an enhanced algorithm using SD as one of potentially plural inputs, gNB determines the frequency of SRS transmission (the inverse value is also known as “SRS period”). It may also determine the SRS frequency allocation by this algorithm.

Then, gNB informs UE on the sounding configuration, i.e. SRS-Config and SRS-Resource, which include the SRS period. In addition, gNB may configure UE with an SD update period (e.g. “SD-ConfigureUpdatePeriod”), in which the UE shall update the SD information. Then, based on these parameters, channel estimation is performed as usual.

The UE updates the SD information according to at least one of the following events: • lapse of the SD update period, if the same is provided by gNB;

• lapse of a predefined update period; and

• triggered by event, e.g. a sudden move of the UE.

Then, gNB acts as described above on the updated SD information.

In some example embodiments, the UE computes the SD locally based on the available information at the UE, for instance IMU/GPS sensors and data traffic demand. Algorithms based on sensor fusion or machine learning can predict/estimate the current/next appropriate SD such that given an accuracy level the SRS periodicity is minimized. The algorithms may be proprietary or standardized.

A main benefit of some example embodiments of the invention is the reduction of unnecessary SRS occasions required per user, reducing overhead in NR systems, where high amount of UEs will be active, some of them with many antennas. This allows to properly handle more UEs in the same cell and improve UE’s battery life.

A further benefit of some example embodiments of the invention, compared to state of the art techniques to reduce SRS allocation that do not relying on active support by UE, is that the system is able to cope with a case of a suddenly moving nomadic user which helps to keep up the reliability of the system e.g. in an URLLC case.

More details on the implementation, signalling and practical examples will be given below.

In a wireless network (e.g. a cellular system with gNB and UE (or a WLAN with AP and MS)), the total throughput may be improved by reducing the amount of required signalling. In current systems, the interval of SRS update is determined by the gNB (AP) based on the observation of the previous channel estimates or statistical model of the channel. Some example embodiments of this invention enhance this process because they consider the dynamic changes of the channel and do not rely only on observed channel estimates of the past.

Building blocks of such example embodiments are recapped below (see also Fig. 1 ):

• Determining SD at the UE side,

• Defining SD Information from gNB to UE; may be performed through standard signaling • gNB updates SRS allocation, supported by the SD Information sent by the UE. In this paragraph, we also address the gains in reliability and timing offered by the solution and why those cannot be achieved with current solutions.

• Optional: the gNB may require/set a certain periodicity of SD Information update from the UE; it may be performed through standard signaling.

Determining SD at UE side

Some example embodiments of the invention may be applied preferably to mobile devices that are not always actively sending data, like a mobile phone.

Our proposition to determine SD relies on two main effects to forecast the amount of SRS needed for a specific UE, (i) its movement, and (ii) its data transmission profile (but also other information available in the UE may influence this SD).

To make it clear, we take the approach to the extreme:

If we assume to know that the channel is static, one doesn’t require much efforts to keep track of a static channel.

If we assume that the UE will not transmit for the time being, there is no need of carefully tracking the channel.

These two extremes explain how the UE can support gNB by properly signalling situations where UL channel estimation could be relaxed.

For instance, if a UE is left on a table for 1-2 hours (typical), accelerometers can easily detect that the phone is static (and in a flat position). If the UE signals a corresponding information to the gNB, gNB may reduce frequency of SRS transmissions for the UE accordingly, because the channel to the phone basically static (and typically does not require much throughput). The SRS bandwidth may be reduced as well. Then, as soon as the UE is moved again, the UE may quickly signal to the gNB the need of resuming SRS transmission with the usual SRS period necessary to track the channel of a moving phone.

As this little example illustrate, this invention will result in less frequent and resourcedemanding SRS transmissions, which in turn increases the battery life of the UE and the capability of NR systems to either support more UEs or achieving better CSI for the UEs that really need it. In general, local algorithms (i.e. running locally in the UE) may be used to determine this SD Information. They may rely on e.g.

Local UE sensors, like IMUs. Note that this will come at zero additional battery consumption, as accelerometers and magnetometers typically are always active on a cell phone.

UL traffic profile (actual or predicted usage),

Other local information (GNSS such as GPS, Galileo, etc...). As an example, unlocking the screen is a clear indicator that a mobile is about to be used, and data transmission may be triggered.

For instance, to just detect if a phone is static, one may simply use accelerometers information, that are present in all state-of-the-art smartphones, and work by thresholding them, as suggested also in online forums [8], while all information about Android can be found e.g. in [9]. The idea is to understand if the phone is static by measuring no variations in accelerometers, and then rotate the 3D coordinates to align the z-axis with gravity, to understand phone’s orientation (its “orientation state”).

Then one can detect movements, by just monitoring accelerometers, and defining a threshold of variation. If the threshold is exceeded, movement is happening.

The same idea may be applied for determining if the speed of a UE has changed substantially. If the UE moves slowly (e.g. pedestrian), less frequent SRS transmissions are required than in a case where the UE is moving fast (e.g. in a train). Thresholding may be used to detect relevant changes of the speed.

More complicated algorithms may be used to build a classifier with KNN, random forests and/or deep neural networks, where inputs are local sensor information and actual/predicted traffic, and output is the UL traffic demand for the next few seconds.

Independent from the detailed technique used to get this SD information, the UE may then transmit the SD signal to the gNB, e.g. through signalling (preferably standardized signalling) or as a payload.

Fig. 2 shows an example of a classifier that makes decisions on the KaLi values. In this example, the KaLi values are buffered traffic, GPS coordinates, accelerometer values, magnetometer values, gyroscope values, and other local information. In general, all or only a subset of these values may be used. The classifier’s task is to select an SD according to the input data KaLi. If we choose only 1 bit to represent SD, then the output is either “0” or “1”. However, the SD can take any finite number of classes. The choice of the classifier highly depends on the application, input data, channel, and complexity versus accuracy requirements.

Signalling SD from UE to gNB

Once SD has been estimated, the UE may transmit it to gNB. The transmission may be immediately after the estimation of SD (e.g. in case of a triggered transmission of SD) or some time later (e.g. in case of a periodical update of the SD). SD may be embedded in the UL signalling. For instance, SD may reside in the PUCCH if the UE has no data to transmit, as it may be the case when the UE is static. On the other hand, SD may be located also in the PUSCH in case there is data transmission. E.g. SD may be attached to the (PMI+) CQI report. In principle, SD may also be included in some payload instead of signalling.

As described above, SD may be conveyed to gNB in one of different ways. It may be contained in (an) additional field(s). This one or more additional fields may contain at least one of the following

• SD-isStatic\ 1 bit field (0 -> UE is static, hence it is advised to reduce SRS frequency, 1 -> not static)

• SD-suggestedPeriodicityAndOffset-p\ field containing the suggested time periodicity for SRS transmissions. Note the similarity between this and the signal used by the gNB to configure SRS period, namely SRS-periodicityAndOffset-p message in section 6.4.1.4.4 of 3GPP TS 38.211.

• (optionally) SD -SuggestedConfig and SD-Suggested Resource : potential additional information about suggested configuration of SRS from the UE to the gNB. As for the field before, this field will contain information from the UE that will help the gNB to determine its corresponding SRS-Config and SRS-Resource messages (see section 6.4.1.4 of 3GPP TS 38.211 ).

• SD-UpdatePeriod\ Actual SD Update Period (it can be changed actively by the gNB, if necessary, by a proper SD-ConfigureUpdatePeriod message from the gNB to the UE).

SD Information may be updated periodically from UE to gNB, but also triggered ad-hoc if the situation requires it, e.g. if a phone is starting to move after much time in a static condition. These triggered updates are recommended to quickly reflect a switch off the UE from an inactive to an active condition.

SRS Allocation in the gNB, aided by UE’s SD.

The gNB computes the SRS allocation with internal algorithms, exploiting SD in addition to other information available, and signals it to the UE. A simple algorithm for this purpose according to some example embodiments of the invention may be based on solving an optimization problem where the objective is to keep the quality of the CSI above a certain threshold while, minimizing the need for SRS. One, can use the SD in conjunction to the above classical method as in the following. If the SD is one bit only, then “0” indicates no activity. The SRS algorithm should reduce the updates requirements drastically. The level of this reduction is learned via its effect on the performance for each channel. If the SD reports “1”, which indicates non-static case, the SRS update follows the state-of-the-art scheme. More complex algorithms are feasible for some example embodiments of the invention.

We comment on the potentially achievable gains, compared to a system not supported by SD sent by the UE:

In what follows, we present the benefits of SD sharing more precisely. Let T_t be the total transmission time, of which the total time that the sounding signal takes up is T_s :=

where d is the total number of SRS signals required and t_{(S i)} is the time required for each SRS symbol. The gNB can control over the d throughout any given transmission period T_t. This could be periodic or aperiodic.

We propose a signalling strategy that uses SD to increase the temporal efficiency, defined by

T — T p = — — -. The information from SD helps to decreases d by limiting the unnecessary updates

^Tt when the channel is static for longer periods of time. In the following, we present a numerical example on those values. Assume that the periodic updates are at 10ms (note that it can be as low as 2ms for LTE). If for a long period of time the UE is not moving (say 1000 seconds), the UE must transmit about 100,000 SRS updates. However, according to some example embodiments of the invention, the UE notifies the gNB that it is in the static mode. Therefore, less frequent or no updates are necessary. Thus, the UE could end up updating with, e.g. 500 ms periods. This results in only 2000 SRS transmissions. Note that some example embodiments of the invention may not (or even cannot) deteriorate the overall system performance. However, the way that gND uses the SD determines the performance. Some example embodiments of the invention provide an additional information for the gNB to make appropriate decisions on the update intervals.

Thinking about the benefits of the invention, one can detect if the phone is static with IMUs with almost 100% confidence and signal it in real time (hence no latency/reliability issue). The physical sensors, available at nearly any smartphone nowadays, capture the tiniest movement of the UE and therefore provide a very accurate indicator on the change of the channel. On the other hand, with state-of-the-art techniques, one must estimate the movement state of the UE from previous channel measurements, that may be noisy and allow to roughly estimate the speed, with some delay due to the need of taking multiple measurements to have an history.

Due to the latency and relatively low reliability of prior art methods, prior art solutions do not allow an aggressive reduction of SRS allocation for users that are static. Our solution brings enhanced confidence and fast information to the gNB, to trigger a proper increase/decrease of the frequency of SRS transmission at the right times, and allows a safe reduction of allocation when the terminal knows that it is static/not transmitting.

In some example embodiments, gNB may exploit SD signals even for URLLC targets (applications). However, even if SD signals are not exploited for URLLC targets to reduce their SRS allocation, they can still benefit from some example embodiments of the invention, because it is probable that services with more relaxed QoS may accept to reduce their SRS, given the opportunity of getting back SRS just at the time when they need it.

Optional: the gNB may require/set a certain periodicity of SD Information update from the UE (e.g. through (standardized) signalling)

Another signal may be defined from the gNB to the UE in order to determine the periodicity of this SD Information signal transmitted by the UE. This can help to regulate such SD transmission, to tune the tradeoff between overhead and reaction time of the system.

This period may be communicated with an ad-hoc field (e.g. “SD-ConfigureUpdatePeriod”) in a message from the gNB to the UE. For example, the period may be measured in number of subframes. Fig. 3 shows an apparatus according to an embodiment of the invention. The apparatus may be a terminal such as a UE, a MTC device, a MS etc., or an element thereof. Fig. 4 shows a method according to an embodiment of the invention. The apparatus according to Fig. 3 may perform the method of Fig. 4 but is not limited to this method. The method of Fig. 4 may be performed by the apparatus of Fig. 3 but is not limited to being performed by this apparatus.

The apparatus comprises means for detecting 10, means for determining 20, and means for informing 30. Each of the means for detecting 10, means for determining 20, and means for informing 30 may be a detecting means, determining means, and informing means, respectively. Each of the means for detecting 10, means for determining 20, and means for informing 30 may be a detector, determiner, and informer, respectively. Each of the means for detecting 10, means for determining 20, and means for informing 30 may be a detecting processor, determining processor, and informing processor, respectively.

The means for detecting 10 detects at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal (S10). Examples movement states are “being (nearly) static”, or “being moved”, or “being moved with a speed in a certain speed range”, or “being moved in a certain direction range”, etc., or a combination thereof.

Based on the at least one of the movement state, the orientation state, and the predicted traffic of S10, the means for determining 20 determines a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal (S20). For example, the signal may be one or more of a SRS, a CQI, a PMI, a Rl, and a CSI-RS.

The means for informing 30 informs the base station on the sounding demand (S30).

Fig. 5 shows an apparatus according to an embodiment of the invention. The apparatus may be a base station such as a gNB, eNB, AP, etc., or an element thereof. Fig. 6 shows a method according to an embodiment of the invention. The apparatus according to Fig. 5 may perform the method of Fig. 6 but is not limited to this method. The method of Fig. 6 may be performed by the apparatus of Fig. 5 but is not limited to being performed by this apparatus.

The apparatus comprises means for monitoring 110, means for determining 120, and means for instructing 130. Each of the means for monitoring 110, means for determining 120, and means for instructing 130 may be a monitoring means, determining means, and instructing means, respectively. Each of the means for monitoring 110, means for determining 120, and means for instructing 130 may be a monitor, determiner, and instructor, respectively. Each of the means for monitoring 110, means for determining 120, and means for instructing 130 may be a monitoring processor, determining processor, and instructing processor, respectively.

The means for monitoring 110 monitors if a base station receives an indication of a sounding demand from a terminal (S110).

If the base station receives the indication of the sounding demand (S110 = yes), the means for determining 120 determines a sounding period based on the sounding demand indicated by the indication of the sounding demand (S120).

The means for instructing 130 instructs at least one of the terminal and the base station to transmit a sounding signal for estimating a quality of a channel between the base station and the terminal periodically with the determined sounding period (S130). For example, the signal may be one or more of a SRS, a CQI, a PMI, a Rl, and a CSI-RS.

Fig. 7 shows an apparatus according to an embodiment of the invention. The apparatus may be a base station such as a gNB, eNB, AP, etc., or an element thereof. Fig. 8 shows a method according to an embodiment of the invention. The apparatus according to Fig. 7 may perform the method of Fig. 8 but is not limited to this method. The method of Fig. 8 may be performed by the apparatus of Fig. 7 but is not limited to being performed by this apparatus.

The apparatus comprises means for monitoring 210 and means for estimating 220. The means for monitoring 210 and means for estimating 220 may be a monitoring means and estimating means, respectively. The means for monitoring 210 and means for estimating 220 may be a monitor and estimator, respectively. The means for monitoring 210 and means for estimating 220 may be a monitoring processor and estimating processor, respectively.

The means for monitoring 210 monitors if a base station receives an indication of a sounding demand from a terminal (S210).

If the base station receives the indication of the sounding demand (S210 = yes), the means for estimating 220 estimates at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand (S220). Fig. 9 shows an apparatus according to an embodiment of the invention. The apparatus comprises at least one processor 810, at least one memory 820 including computer program code, and the at least one processor 810, with the at least one memory 820 and the computer program code, being arranged to cause the apparatus to at least perform at least one of the methods according to Figs. 4, 6, and 8 and related description.

Some example embodiments of the invention are described with respect to transmission of SRS. However, the invention is not limited to SRS. For example, it may be applied to other signals (e.g. pilot symbols) which are used to estimate the channel quality between UE and gNB, such as CQI, PMI, Rl (transmitted by UE), and/or CSI-RS (transmitted by gNB). Note that e.g. type II CSI in 3GPP NR consumes a large number of bits (e.g. several hundred) to report a PMI. Due to some example embodiments of the invention, feedback signalling overhead could be considerably reduced.

Embodiments of the invention are described for 3GPP networks such as 3G networks, 4G networks, 5G networks. However, the invention is not restricted to 3GPP networks and may be employed in other wireless networks such as WLAN or WiFi, too. For example, in WLAN or WiFi, the roles of UE and gNB are provided by MS and AP, respectively.

One piece of information may be transmitted in one or plural messages from one entity to another entity. Each of these messages may comprise further (different) pieces of information.

Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and/or protocols and/or methods may be different, as long as they provide a corresponding functionality.

If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they perform different functions. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware. It does not necessarily mean that they are based on different software. That is, each of the entities described in the present description may be based on different software, or some or all of the entities may be based on the same software. Each of the entities described in the present description may be embodied in the cloud. According to the above description, it should thus be apparent that example embodiments of the present invention provide, for example, a terminal such as a UE or a MS or a component thereof, an apparatus embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s). According to the above description, it should thus be apparent that example embodiments of the present invention provide, for example, a base station such as a gNB, eNB, or AP, or a component thereof, an apparatus embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s).

Implementations of any of the above described blocks, apparatuses, systems, techniques or methods include, as non-limiting examples, implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

It is to be understood that what is described above is what is presently considered the preferred embodiments of the present invention. However, it should be noted that the description of the preferred embodiments is given by way of example only and that various modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

Claims:

1. Apparatus, comprising means for detecting configured to detect at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal; means for determining configured to determine a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal based on the at least one of the movement state, the orientation state, and the predicted traffic; means for informing configured to inform the base station on the sounding demand.

2. The apparatus according to claim 1 , further comprising means for checking configured to check if at least one of the movement state and the orientation state changes by more than a respective predetermined threshold; means for triggering configured to trigger the means for determining to determine the sounding demand and the means for informing to inform on the sounding demand if at least one of the movement state and the orientation state changes by more than the respective predetermined threshold.

3. The apparatus according to any of claims 1 and 2, wherein the means for informing is configured to inform the base station on the sounding demand periodically with a time period.

4. The apparatus according to claim 3, wherein the time period is predefined.

5. The apparatus according to claim 3, further comprising means for monitoring configured to monitor if an indication of the time period is received from the base station; wherein the means for informing is configured to inform the base station periodically on the sounding demand with the time period indicated by the base station.

6. The apparatus according to any of claims 1 to 5, wherein the means for detecting comprises at least one of an inertial measurement unit of the terminal, a GNSS receiver of the terminal, and a module for performing a radio based positioning technique.

7. The apparatus according to any of claims 1 to 6, wherein the means for detecting comprises a detector of a traffic buffered in the terminal.

8. Apparatus, comprising means for monitoring configured to monitor if a base station receives an indication of a sounding demand from a terminal; means for determining configured to determine a sounding period based on the sounding demand if the base station receives the indication of the sounding demand; means for instructing configured to instruct at least one of the terminal and the base station to transmit a sounding signal for estimating a quality of a channel between the base station and the terminal periodically with the determined sounding period.

9. The apparatus according to claim 8, wherein at least one of the means for instructing is configured to instruct the terminal, and the sounding signal is at least one of a sounding reference signal, a channel quality indicator, a precoding matrix indicator, and a rank indicator; and the means for instructing is configured to instruct the base station, and the sounding signal is a channel state information reference signal.

10. The apparatus according to any of claims 8 and 9, further comprising means for setting configured to set a time period based on the sounding demand; wherein the means for instructing is configured to instruct the terminal to update the indication of the sounding demand with the set time period.

11. The apparatus according to any of claims 8 to 10, wherein the means for determining is configured to determine a frequency allocation of the sounding signal based on the sounding demand.

12. The apparatus according to any of claims 8 to 11 , further comprising means for estimating configured to estimate at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand.

13. Apparatus, comprising means for monitoring configured to monitor if a base station receives an indication of a sounding demand from a terminal; means for estimating configured to estimate at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand if the base station receives the indication of the sounding demand.

14. Method, comprising detecting at least one of a movement state of a terminal, an orientation state of the terminal, and a predicted traffic of the terminal; determining a sounding demand to transmit a signal for estimating a quality of a channel between a base station and the terminal based on the at least one of the movement state, the orientation state, and the predicted traffic; informing the base station on the sounding demand.

15. The method according to claim 14, further comprising checking if at least one of the movement state and the orientation state changes by more than a respective predetermined threshold; triggering to determine the sounding demand and to inform on the sounding demand if at least one of the movement state and the orientation state changes by more than the respective predetermined threshold.

16. The method according to any of claims 14 and 15, further comprising informing the base station on the sounding demand periodically with a time period.

17. The method according to claim 16, wherein the time period is predefined.

18. The method according to claim 16, further comprising monitoring if an indication of the time period is received from the base station; informing the base station periodically on the sounding demand with the time period indicated by the base station.

19. The method according to any of claims 14 to 18, wherein the at least one of the movement state of the terminal and the orientation state of the terminal is detected byat least one of an inertial measurement unit of the terminal, a GNSS receiver of the terminal, and a module for performing a radio based positioning technique.

20. The method according to any of claims 14 to 19, wherein the predicted traffic of the terminal is detected by a detector of a traffic buffered in the terminal.

21. Method, comprising monitoring if a base station receives an indication of a sounding demand from a terminal; determining a sounding period based on the sounding demand if the base station receives the indication of the sounding demand; instructing at least one of the terminal and the base station to transmit a sounding signal for estimating a quality of a channel between the base station and the terminal periodically with the determined sounding period.

22. The method according to claim 21 , wherein at least one of the terminal is instructed to transmit the sounding signal, and the sounding signal is at least one of a sounding reference signal, a channel quality indicator, a precoding matrix indicator, and a rank indicator; and the base station terminal is instructed to transmit the sounding signal, and the sounding signal is a channel state information reference signal.

23. The method according to any of claims 21 and 22, further comprising setting a time period based on the sounding demand instructing the terminal to update the indication of the sounding demand with the set time period.

24. The method according to any of claims 21 to 23, further comprising determining a frequency allocation of the sounding signal based on the sounding demand.

25. The method according to any of claims 21 to 24, further comprising estimating at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand.

26. Method, comprising monitoring if a base station receives an indication of a sounding demand from a terminal; estimating at least one of a speed of the terminal and a future traffic from the terminal based on the sounding demand if the base station receives the indication of the sounding demand.

27. A computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any of claims 14 to 26.

28. The computer program product according to claim 27, embodied as a computer-readable medium or directly loadable into a computer.