WO2016120454A1

WO2016120454A1 - Methods and devices for reporting filtering information of channel status information

Info

Publication number: WO2016120454A1
Application number: PCT/EP2016/051937
Authority: WO
Inventors: Fredrik Nordström; Maomao Chen
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-01-30
Filing date: 2016-01-29
Publication date: 2016-08-04

Abstract

The disclosure relates to methods and devices for Channel State Information, CSI, reporting. More particularly, the disclosure pertains to a wireless device filtering CSI for a dynamic channel and to the wireless device reporting filtering information defining the CSI filtering to a network node and to the network node using the reported filtering information. This disclosure proposes method performed in a second wireless node (20) that is configured to transmit data to a first wireless node (10) over a dynamic wireless channel. The method comprises receiving (S11), from the first wireless node (10), filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel, transmitting (S12a) data to the first wireless node over the dynamic wireless channel, and receiving (S12b), from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter. According to the disclosure the transmission (S12a) of data to the first wireless node and/or the reception (S12b) of CSI from the first wireless node, is based on the received filter information.

Description

Methods and devices for Reporting Filtering Information of Channel Status Information TECHNICAL FIELD

The present disclosure relates to methods and devices for Channel State Information, CSI, reporting. More particularly, the disclosure pertains to a wireless device filtering CSI for a dynamic channel and to the wireless device reporting filtering information defining the CSI filtering to a network node and to the network node using the reported filtering information.

BACKGROUND

The 3rd Generation Partnership Project, 3GPP, is responsible for the standardization of the Universal Mobile Telecommunication System, UMTS, and Long Term Evolution, LTE. The 3GPP work on LTE is also referred to as Evolved Universal Terrestrial Access Network, E-UTRAN. LTE is a technology for realizing high-speed packet-based communication that can reach high data rates both in the downlink and in the uplink. In order to support high data rates, LTE allows for a system bandwidth of 20 MHz, or up to 100 MHz when carrier aggregation is employed. LTE is also able to operate in different frequency bands and can operate in at least Frequency Division Duplex, FDD and Time Division Duplex, TDD, modes.

The Channel State Information, CSI, refers to known channel properties of a communication link. This information describes how a signal propagates from the transmitter to the receiver and represents the combined effect of, for example, scattering, fading, and power decay with distance. The CSI makes it possible to adapt transmissions to current channel conditions, which is crucial for achieving reliable communication with high data rates in multi-antenna systems. Feeding back CSI to a transmitter in order for a transmitting network node or eNodeB to optimally utilize sparse radio spectrum for future transmissions is well established prior art. Hereby the eNodeB can select the optimal Modulation and Coding Scheme, MCS, rank and precoding matrix for a packet such that it, with certain likelihood, is correctly received at the receiver after passing through the medium, while still utilizing sparse radio resources efficiently.

A User Equipment, UE, that is moving with some speed in relation to an access point such as a base station, is exposed to highly varying channel conditions. Since CSI feed-back typically requires processing, and transmission from the UE to the eNodeB and then further processing at the eNodeB, a delay is introduced between the instant of CSI measurement and the instant when the data transmission based on said CSI actually takes place at the eNodeB. During that time, channel conditions may have changed substantially thereby rendering the CSI obsolete, in turn resulting in the eNodeB using a suboptimal MCS for its transmissions. The 3GPP standard TS 36.101 version 12.5.0 has partly taken UE speeds up to 300 km/h into account for the data demodulation part, but not for the CSI reporting. With increase deployment of high speed train lines, increased number of UE users, and increased usage of bandwidth per user, dominating operators are requesting improved UE performance and support for speeds exceeding 300 km/h. Future high speed trains are expected to travel at speeds above 500km/h, e.g. the Superconducting Magnetic Levitation train (SCMaglev) to be deployed in Japan starting the next decade, and where train sets have reached 580 km/h in speed tests already a decade ago.

However, all the 3GPP requirements for CSI from 3GPP TS 36.101 version 12.5.0 are under the assumption of either static or very low speed (e.g. 3km/h). The minimum delay in 3GPP LTE between measuring the channel quality and the time UE reports CSI is 4ms, on top of that there will be delay in the eNodeB for processing and transmit according to the reported CSI. Hence, there is a need for improved methods for CSI reporting.

SUMMARY

An object of the present disclosure is to provide a method of predicting CSI which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination. In particular, it is an object of the present disclosure to provide an improved way of mitigating the effects of the time difference between the moment of performing CQJ measurement and its time of use when the channel is changing rapidly. This object is obtained by a method performed in a second wireless node that is configured to transmit data to a first wireless node over a dynamic wireless channel. The method comprises receiving, from the first wireless node, filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel. The method further comprises, transmitting data to the first wireless node over the dynamic wireless channel, and receiving, from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter. In accordance with the proposed methods, the transmission of data to the first wireless node and/or the reception of CSI is based on the received filter information.

Thereby the behavior of the first wireless node, being e.g. a UE, is unified and known to the second wireless being e.g. a network node. The second wireless node can utilize radio resources more efficiently, while taking into consideration the time domain filtering information of reported CSI from one or more UEs.

According to some aspects, the second wireless node adjusts its own filtering when receiving CSI, based on the filter information. Thereby, the network node can apply additional filtering only if it's necessary to optimize the system throughput, when under high speed scenarios. Double filtering may thus be avoided.

According to some aspects, the second wireless node schedules, the same rank, precoder and/or MCS during a certain time, based on the filter information. By adapting link adaptation the UE and system performance loss can be minimized. According to some aspects, the second wireless node forwards the information to other wireless nodes. The receiving wireless node, e.g. another network node, may then use the received information for one or more radio tasks. For example a RNC may adapt or modify one or more UEs (first, second or third UEs) with the correlation information provided by the UEs.

The method of any of the preceding claims, wherein the second wireless node adjusts CSI reporting or processing rate, based on the filter information. The second wireless node, such as a network node, can adapt its CSI reporting rate by taking into account the channel variation, i.e. how much the channel varies in time. Hence, reduced signaling overhead is achieved in the system since unnecessary reporting is avoided.

According to some aspects, the disclosure further relates to a method performed in a first wireless node that is configured for receiving data from a second wireless node over a dynamic wireless channel. The method comprises obtaining filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel, and transmitting the filter information to the second wireless node. According to some aspects, the disclosure further relates to a first wireless node configured for receiving data from a second wireless node over a dynamic channel. The first wireless node comprises radio circuitry adapted to receive a radio signal transmitted over the dynamic wireless channel and processing circuitry adapted to obtain filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, of the dynamic channel, and to transmit the filter information to the second wireless node.

According to some aspects, the disclosure further relates to second wireless node configured to transmit data to a first wireless node over a dynamic wireless channel. The second wireless node comprises radio circuitry adapted to transmit and receive radio signals over the dynamic wireless channel and processing circuitry adapted to receive, from the first wireless node, filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel. The radio circuitry is further adapted to cause the second radio network node to transmit data to the first wireless node over the dynamic wireless channel, and to receive, from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter. In accordance with the proposed methods, the transmission of data to the first wireless node and/or the reception of CSI, is based on the received filter information.

According to some aspects, the disclosure further relates to a computer program comprising computer program code which, when executed in a first wireless node, causes the first wireless node to execute the methods according to any of the embodiments described above and below.

According to some aspects, the disclosure further relates to a computer program comprising computer program code which, when executed in a second wireless node, causes the second wireless node to execute the methods according to any of the embodiments described above and below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments. Figure 1 shows a high speed train scenario;

Figure 2 illustrates a first and a second wireless node moving in relation to each other;

Figure 3 is a flowchart illustrating embodiments of method steps in a second wireless node; Figure 4a is a flowchart illustrating embodiments of method steps in a first wireless node; Figure 4b illustrates Doppler spread spectrum;

Figure 5 is an example node configuration of a second wireless node, according to some of the example embodiments;

Figure 6 is an example node configuration of a first wireless node, according to some of the example embodiments;

Figure 7 illustrates a plot of simulated data throughput with and without a UE time domain filter under different UE speeds;

Figure 8 illustrates a plot of simulated data throughput for a UE applying different filter lengths;

Figure 9 illustrates a wireless network comprising a more detailed view of network node and wireless device, in accordance with a particular embodiment.

DESCRIPTION

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatuses and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

For better understanding of the proposed technique CSI reporting and high speed scenarios and problems related thereto, will now be described and discussed.

High speed scenarios

Apart from the relatively shortened time for detecting suitable neighbor cells for handover or cell reselection, high speed may also lead to significant Doppler shifts of the received signal. The Doppler shift forces the UE to increase its demodulation frequency when moving towards the cell, and decrease it when moving away from the cell, relative to the carrier frequency used in the network. The magnitude of the Doppler shift depends on the relative velocity of the UE towards the transmitting antenna. Hence, with transceivers close to the track, i.e., a small angle between the trajectory of the UE and the line between the UE and the transmitting antenna, a substantial part of the UE velocity will transfer into a Doppler shift. Moreover, there will be an abrupt change of sign of the Doppler shift when the UE passes the transmitting antenna and the smaller the angle, the more abrupt the change is.

The Doppler shift can be expressed as:

where c is the speed of light and v is the relative velocity of the UE towards the transmitting antenna. With an angle a and a UE velocity v_UE the relative velocity v, towards the transmitting antenna giving rise to Doppler shift is, v = v_UE cos a.

Each radio propagation path may have its own Doppler shift, depending on how the waves travel between the transmitting antenna and the UE. In case of line-of-sight there is one dominant path, whereas in e.g. urban areas there is generally scatter (reflections) due to buildings to which the UE has a relative velocity, giving rise to multiple paths for the signal to propagate to the UE, each with a different Doppler shift. Since the received signal (in general) is the superposition of those paths, it gives rise to delay spread which degrades the receiver performance by spread out the signal in the time domain. The Doppler shift and the delay spread will cause inter-carrier interference and maybe also inter-symbol interference.

The scenario is illustrated in Figure 1, where the UE is on a high speed train, connected to and moving away from cell A.2 and quickly needs to detect cell B.l towards which it is moving. According to the standard 3GPP Technical specification, TS, 36.213 version 12.1.0, the cell site can be as close as 2 meters from the tracks, mainly motivated by that the radio access network would typically be integrated with the high-speed railway infrastructure.

In the high speed train scenario illustrated in Figure 1 the train may travel at speeds up to 500km/h and the UE is handed over to a new cell, or has to reselect a cell to camp on, frequently. The angle a determines the Doppler shift encountered by the UE when receiving signals transmitted in Cell B.l. CSI reporting in LTE The uplink feedback for support, also referred to as channel status or channel status information, CSI, of downlink data transmission consists of the Rl, Rank indicator, the Precoding Matrix Indicator, PMI, and the Channel Quality Indicator, CQJ. The Rl indicates the number of layers, which can be accommodated by the current spatial channel experienced at the UE. It was observed in the LTE evaluation that the frequency-selective Rl reporting did not provide significant performance benefit, and therefore only one wideband Rl is reported for the whole bandwidth. On the contrary, the reporting of PMI and CQJ can be either wideband or frequency-selective.

The PMI is calculated conditioned on the associated Rl, and the CQI is calculated conditioned on the associated Rl and PMI. For Rl = 1, only one CQI is reported for each reporting unit in frequency, which could be either wideband or sub band in the case of frequency-selective report. For Rl > 1, for closed-loop spatial multiplexing one CQI is reported for each code word as different code words experience different layers, while for the open-loop spatial multiplexing only one CQI is reported as each code word experiences all layers. The PMI indicates the preferred precoding candidate for the corresponding frequency unit, for example, a particular sub band or the whole frequency bandwidth, and is selected from the possible precoding candidates according to the Rl. The PMI is only reported for closed-loop spatial multiplexing.

The CQI indicates the combination of the maximum information data size and the modulation scheme among QPSK, 16QAM, 64QAM, and 256QAM which can provide block error rate not exceeding 0.1 assuming that the reported rank and the reported precoding matrix are applied in the time-frequency resource. With this definition of CQI, PMI, and Rl, the UE can report the maximum data size that it can receive and demodulate, taking into account its receiver ability.

In case of the frequency-selective PMI/CQI reporting, the UE reports a PMI/CQI for each sub band. For the non-frequency-selective wideband PMI/CQI reporting, the UE reports a single wideband PMI/CQI corresponding to the whole bandwidth. In the frequency-selective reporting mode, the sub band CQI is reported as a differential value with respect to the wideband CQI in order to reduce the signaling overhead. When the frequency-selective CQI reporting is configured, the sub band CQIs as well as the wideband CQI is reported, and the wideband CQI serves as the baseline for recovering the downlink channel condition in the whole band. The frequency-selective report naturally results in large signaling overhead. In the cases where the uplink overhead is a limiting factor, the eNodeB can also configure non-frequency- selective CQJ/PMI reports. To cope with various channel conditions and various antenna configurations while keeping the signaling overhead at appropriate level, various feedback modes are specified concerning on the frequency selectivity of the CQJ and the PMI reports. The physical channels that can be used for the uplink feedback signaling are Physical Uplink Control Channel (PUCCH) and Physical Uplink Shared Channel (PUSCH).

The following are the definitions of CQJ and CSI reference resource as defined in 3GPP TS 36.213 version 12.1.0. Based on an unrestricted observation interval in time and frequency, the UE shall derive for each CQJ value reported in uplink sub frame n the highest CQI index between 1 and 15 which satisfies the following condition or CQI index 0 if CQI index 1 does not satisfy the condition:

A single PDSCH transport block with a combination of modulation scheme and transport block size corresponding to the CQI index, and occupying a group of downlink physical resource blocks termed the CSI reference resource, could be received with a transport block error probability not exceeding 0.1.

The CSI reference resource for a serving cell is defined as follows:

In the frequency domain, the CSI reference resource is defined by the group of downlink physical resource blocks corresponding to the band to which the derived CQI value relates. In the time domain:

For a UE configured in transmission mode 1-9 or transmission mode 10 with a single configured CSI process for the serving cell, the CSI reference resource is defined by a single downlink sub frame n-n_CQi__ref, where for periodic CSI reporting n_CQi__ref is the smallest value greater than or equal to 4, such that it corresponds to a valid downlink sub frame; where for aperiodic CSI reporting n_CQi__ref is such that the reference resource is in the same valid downlink sub frame as the corresponding CSI request in an uplink DCI format; where for aperiodic CSI reporting n_CQi__ref is equal to 4 and downlink sub frame n-n_CQi__ref corresponds to a valid downlink sub frame, where downlink sub frame n-n_CQi__ref is received after the sub frame with the corresponding CSI request in a Random Access Response Grant. For a UE configured in transmission mode 10 with multiple configured CSI processes for the serving cell, the CSI reference resource for a given CSI process is defined by a single downlink sub frame n-ncQi ref, where for FDD and periodic or aperiodic CSI reporting n_CQi__ref is the smallest value greater than or equal to 5, such that it corresponds to a valid downlink sub frame, and for aperiodic CSI reporting the corresponding CSI request is in an uplink DCI format; where for FDD and aperiodic CSI reporting n_CQi__ref is equal to 5 and downlink sub frame n-n_CQi_ref corresponds to a valid downlink sub frame, where downlink sub frame n- ncQi_ref is received after the sub frame with the corresponding CSI request in a Random Access Response Grant; - where for TDD, and 2 or 3 configured CSI processes, and periodic or aperiodic CSI reporting, n_CQi__ref is the smallest value greater than or equal to 4, such that it corresponds to a valid downlink sub frame, and for aperiodic CSI reporting the corresponding CSI request is in an uplink DCI format; where for TDD, and 2 or 3 configured CSI processes, and aperiodic CSI reporting, n_CQi__ref is equal to 4 and downlink sub frame n-n_CQi__ref corresponds to a valid downlink sub frame, where downlink sub frame n-n_CQi__ref is received after the sub frame with the corresponding CSI request in a Random Access Response Grant; where for TDD, and 4 configured CSI processes, and periodic or aperiodic CSI reporting, ncQi_ref is the smallest value greater than or equal to 5, such that it corresponds to a valid downlink sub frame, and for aperiodic CSI reporting the corresponding CSI request is in an uplink DCI format; where for TDD, and 4 configured CSI processes, and aperiodic CSI reporting, n_CQi__ref is equal to 5 and downlink sub frame n-n_CQi__ref corresponds to a valid downlink sub frame, where downlink sub frame n-n_CQi__ref is received after the sub frame with corresponding CSI request in a Random Access Response Grant.

In the above summary from the 3GPP technical specification, the reported CSI should be derived based on only one Downlink, DL, sub frame in time domain. However, from UE side, with higher speed the channel experienced at the UE changes fast, and with delayed feedback the CSI reported from UE side which includes CQJ, PMI, Rl based on one DL sub frame will be out of date.

Further, all the existing 3GPP requirements for CSI from 3GPP TS 36.101 version 12.5.0, are under the assumption of either static or very low speed (e.g. 3km/h). The minimum delay in 3GPP LTE between measuring the channel quality and the time UE reports CSI is 4ms, on top of that there will be delay in the eNodeB for processing and transmit according to the reported CSI.

CSI Filtering in UE

The disclosure is based on that, when under high speed, from UE side it may bring benefit to apply filtering over multiple sub frames on the channel status information, CSI instead of from one sub frame. Seen from UE side, with higher speed of travel, the channel experienced at the UE changes fast, and with delayed feedback the CSI reported from UE, which includes CQJ, PMI, Rl based on one DL sub frame will be out of date. Under some speed scenarios, filtering in time domain at the UE side can increase UE or user throughput as shown in Figure 7 and Figure 8. If the UE speed is beyond 3m/s = 10.8km/h there is clear benefit to apply some filtering at UE side to get more stable CQJ reporting.

Seen from the UE side, when under higher speed, it is beneficial at to apply certain filtering on reported CSI for a higher throughput rather than only deriving it from one Downlink, DL, sub frame.

CSI filtering on the UE side has been proposed e.g. in European Patent Publication EP 1 212 839 Bl, in which document a mobile station can estimate the signal to interference noise ratio and wherein the estimate is filtered with a filter tailored based on the fading environment. Similarly, European Patent Publication EP 1 520 360 Al proposes that channel quality reports from a mobile station to a base station are averaged over a period over time. The period is dependent on the speed with which the mobile station is moving. This type of UE behavior, filtering the CSI reports, is however against definition from specification 3GPP 36.213 version 12.1.0 and therefore unknown at the network node side. If different UEs with different speeds applied with different filtering in the time domain of the channel status while network is without knowledge of this filtering, the network would still assume all the UL feedback of the channel status reported by the UE are still based on the specification parameter of one downlink sub frame. Thus, the network operation will not be optimal from a system level point of view. An example could be that the network node may apply another filtering on top of the filtered channel status reported by the UE, which will give a longer filtering time than network expects. Hence, degradation in system throughput due to a worse link adaptation from the network side will occur in such a situation.

Hence, without the knowledge of the filter information, the network node still considers the reported channel status feedback from one sub frame and may apply additional filtering which decrease the system performance. A solution is therefore proposed herein, wherein the wireless devices may, if appropriate, apply filtering and report the filtering parameters to the network. Such filtering parameters are usable not only for the receiving network node to use when calculating its own filters, but it may also be used to further optimize system performance, as will be discussed below.

It should be noted that although terminology from 3GPP LTE is used herein to explain the example embodiments, this should not be seen as limiting the scope of the example embodiments to only the aforementioned system. Other wireless systems, including Wi-Fi, WCDMA, HSPA, WiMax, UMB and GSM, and future radio access systems may also benefit from the example embodiments disclosed herein. Hence the technique may be implemented in any wireless nodes reporting CSI.

Therefore, the following terminology is introduced: The first wireless node is a device receiving data from a second wireless node. The first wireless node is then reporting CSI to the second wireless node. In the examples below the first wireless node is a wireless device, such as a UE, and the second wireless node is a network node, such as an eNodeB.

Note that terminology such as NodeB or eNodeB and UE should be considering non-limiting and does in particular not imply a certain hierarchical relation between the two; in general "NodeB" could be considered as the second wireless node and "UE" as the first wireless node, and these two devices communicate with each other over some radio channel. Herein, we also focus on wireless transmissions in the downlink, but the invention is equally applicable in the uplink. In some embodiments the non-limiting term user equipment, UE, is used and it refers to any type of wireless device communicating with a radio network node in a cellular or mobile communication system. Examples of UE are target device, device to device, D2D, UE, machine type UE or UE capable of machine to machine, M2M, communication, PDA, Tablet, mobile terminals, smart phone, laptop embedded equipped, LEE, laptop mounted equipment, LME, USB dongles etc.

The embodiments are applicable to single carrier as well as to multicarrier, MC, or carrier aggregation, CA, operation of the UE in conjunction with UL feedbacks consisting of channel status estimated from UE side. The term carrier aggregation, CA, is also called (e.g. interchangeably called) "multi-carrier system", "multi-cell operation", "multi-carrier operation", "multi-carrier" transmission and/or reception. This disclosure presents methods to overcome or mitigate the effects of the delay from the instant of measuring channel data in the UE to the instant where said channel data is used for Modulation and Coding Scheme, MCS, Rank Indicator, Rl and Precoding Matrix, PMI selection in the eNodeB. This is accomplished by introducing filtering CSI in a wireless node reporting the CSI and by providing information about the filtering to the wireless node receiving the CSI.

In the proposed solution, a UE, or first wireless node, not only determines the current status of its filtering of the channel status, but also transmits information about the filtering to the second wireless node (e.g. serving eNode B or base station, BS), or second wireless node. The second wireless node then, based on the received information, performs one or more radio operational tasks leading to more efficient use of radio resources and enhanced system performance. In other words, the second wireless node or network node that is receiving or obtaining the information about the filtering information of channel status from the first wireless node may use the said information for performing one or more radio operational or radio resource management tasks as described below. For example the second wireless node can, based on one or more criteria, such as interference or spectrum spread, decide if the CSI, with the applied filter and filter length in in first node, reported by the first wireless node, is accurate or not and then apply additional filter if it's not enough or subtract less filtered channel status to be used for radio resource management.

The network node can also adapt link adaptation thereby minimizing the UE and system performance loss. The certain time is e.g. equal to the filter length. For example under certain higher speed the first wireless node may schedule the same length of resource in time domain to the first wireless node as the reported filter length reported by the first wireless node. This is because the channel status is filtered with such time period and hence it's natural to use the same Modulation and Coding Scheme, MCS, precoder, rank within the same resource unit.

Figure 2 illustrates a mobile telecommunication system where the proposed methods may be implemented. The system in Figure 2 comprises a first wireless node, here a UE 10, and a second wireless node, here an eNodeB 20, that are communicating with each other over a dynamic radio channel H, here denoted H(n) for sample n in time. Hence, the network node or eNodeB 20 transmits data to a UE 10 and the UE reports CSI to the eNodeB 20. In the examples herein the first wireless node is a User Equipment, UE, and the second wireless node is an eNodeB. However, the technique is applicable in other scenarios as well as mentioned above e.g. in D2D communication wherein both wireless nodes would be UEs. For simplicity, the system of Figure 2 only comprises one network node and one wireless device. This would of course not be the case in a real implementation.

According to some aspect the transmitter-receiver can be described by a matrix H. Then, each element in the J-by-K matrix H describes the instantaneous channel from one transmitter antenna port k to a respective receiver antenna j. Channel State Information is typically reported for each channel layer h_k of H, where H = [h ... h_K]. When estimating CSI for a channel layer, the channel layer k will in this disclosure be referred to as the processed layer. In a MIMO system a channel layer e.g. corresponds to one of the k transmitter antenna ports. The proposed methods are performed in the first and second wireless nodes, here the wireless device 10 and the network node 20, for example in the system of Figure 2. The methods will now be described in more detail referring to Figures 3 and 4. It should be appreciated that the example operations of Figure 3 and 4 may be performed simultaneously for any number of wireless devices and network nodes in the wireless communications network. Example Node Operation of the Second Wireless Node

A method executed in a second wireless node 20, e.g. a network node or an eNodeB, that is configured to transmit data to a first wireless node 10 over a dynamic wireless channel, will now be described with reference to Figure 3. The method may be executed at any time when the second wireless node has data to send to the first wireless node over a rapidly varying channel.

It should be appreciated that Figure 3 comprises some operations which are illustrated with a solid border and some operations which are illustrated with a dashed border. The operations which are comprised in a solid border are operations which are comprised in the broader example embodiment. The operations which are comprised in a dashed border are example embodiments which may be comprised in, or a part of, or are further operations which may be taken in addition to the operations of the solid border example embodiments. It should be appreciated that the operations need not be performed in order. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any suitable order and in any combination.

In the first step, the second wireless node receives Sll, from the first wireless node 10, filter information defining a filter that is (or will be) used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel. The second wireless node transmits S12a data to the first wireless node over the dynamic wireless channel, and receives S12b, from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter. In accordance with the proposed methods, the transmission S12a of data to the first wireless node and/or the reception S12b of CSI, is based on the received filter information. Based on implies that the transmission and/or reception is adapted to take into account the effects of the filter. That is, the second wireless node uses S12 the received information when transmitting data to the first wireless node. Or stated differently, a second wireless node that is transmitting data to a first wireless node receives information about CSI filtering performed in the first wireless node. In this way filtering may be performed on the UE side without risking that system performance is affected. The filtering information describing filtering applied to or in connection with CSI estimation. In other words, the filtering defined the filters used in the first wireless device or at least enables the second wireless device to (at least to some extent) determine which filters were applied. The filtering information of channel status information is e.g. the time period filtering length that the first wireless node uses to do filtering , the filtered element the first wireless node uses filter to and/or the filtering type the first wireless node applies . Examples of filtered elements are Modulation and Coding Scheme, MCS, Signal to Noise Ratio, SNR, Signal to I nterference and Noise Ratio, SI NR, Rank I ndicator, Rl, Precoder Matrix I ndex, PM I, or functions thereof.

The filter information e.g. defines one filter g out of a set of pre-defined filters 9i_> 9_2>— ' 9F that ^{a re} known to the second wireless node. The second wireless node uses the filter information for radio operational or radio resource management tasks. When the second wireless node is transmitting data to the first wireless node, knowing if and how the CSI is filtered in the first wireless node is very useful when utilizing the CSI for different purposes. Thereby, the first wireless node or UE behavior is unified and known to the second wireless node or network node.

The different examples of radio operational or radio resource management tasks using the filtering information will now be described in more detail:

Adapting scheduling

According to some aspects, the method comprises scheduling the sa me rank, precoder and/or Modulation and Coding Scheme, MCS, during a certain time period. The reason for doing this is that if the second node knows that the reported CSI is based on filtering of several samples in time and hence will change slower than without filtering, then some pre-decsion of rank, precoder and/or MCS can be used. Thereby, the network node can utilize radio resources more efficiently while taking into consideration the time domain filtering information from reported CSI from one or more UEs. This because the network node can adapt its own filtering parameters and in that way get the filtering length that is most optimal for the actual scenario (velocity). The network node can also adapt, e.g. increase the period between, the reported CSI and hence use less uplink radio resources. The time between CSI reports can e.g. be the length of the filter applied in the UE. The network node can adapt link adaptation thereby minimizing the UE and system performance loss. The certain time is e.g. equal to the filter length. For example under certain higher speed the first wireless node may schedule the same length of resource in time domain to the first wireless node as the reported filter length reported by the first wireless node because the channel status is filtered with such time period it's natural to use the same Modulation and Coding Scheme, MCS, precoder, rank within the same resource unit.

According to some aspects, the method comprises prescheduling data to be sent from the second wireless node to the first wireless node based on the filter information. Because the MCS, Rank and Precoder are fixed during a certain time it is possible to preschedule the time and frequency to use. Information about the pre-scheduling may be used by other nodes in the network. Doing this may be effective in several scenarios such as for interference mitigation or coordinated multi point (CoMP) operation or coordination. Transmitting information to other network nodes in other cells

The second wireless node may also signal or forward the received information to other wireless nodes. For example, the second wireless node may send it to a third wireless node (such as by Node B to radio network controller (RNC) over lub interface in HSPA) and/or to even a fourth wireless node (e.g. neighboring network node or base station such as by serving eNodeB to neighboring eNodeB over X2 interface in LTE) etc. The receiving wireless nodes may use the received information for one or more radio tasks. For example the RNC may adapt or modify one or more UEs (first, second or third UEs) with the correlation information provided by the UEs. The signaled filtering length can be used by the other wireless nodes, such as other network nodes, for simplifying handover between network nodes, e.g. by presetting other network node CSI filtering parameters.

Adapting CSI filtering in second wireless node

According to some aspects, the method comprises the second wireless node adjusting its own filtering based on the information. In other words, the network node can, based on one or more criteria, first decide if the CSI, with the applied filter and filter length in in first node, reported by the first wireless node, is accurate or not and then apply additional filter if it's not enough or subtract less filtered channel status to be used for radio resource management.

The second wireless node can choose not to do any filtering with the knowledge from UE side (first wireless node). The second wireless node can also apply additional filtering with the knowledge from UE side if it's necessary to optimize the system throughput when under high speed scenarios. Adapting CSI reporting rate

CSI reporting rate means the rate by which CSI is reported by the first wireless node. According to some aspects, the method comprises adjusting CSI reporting or processing rate based on the filter information. In LTE, the network node schedules the resource blocks. Hence, if the second network node is a eNodeB, the adjusting typically means to request the first wireless device to change the CSI reporting rate. E.g. CSI reporting rate may be changed from every sub frame to every 10th sub frame. Today rate in LTE depends on the report mode. The second wireless node may choose to actively ignore some CSI values transmitted by the first wireless node knowing that the CSI will be changing slowly due to the filtering. The current LTE standard for CSI reporting is optimized for low mobility scenarios only. Future enhancement of LTE may include high mobility CSI reporting enhancements.

Example Node Operation of First Wireless Node

A proposed method executed in a first wireless node 10, e.g. an LTE user equipment as in Figure 1, that is configured for receiving data from a second wireless node, e.g. the eNodeB in Figure 1, over a dynamic channel, will now be described with reference to Figure 4a. One typical example is a mobile phone on a high speed train.

It should be appreciated that Figure 4a shows some operations which are illustrated with a solid border and some operations which are illustrated with a dashed border. The operations which are comprised in a solid border are operations, which are comprised in the broader example embodiment. The operations which are comprised in a dashed border are example embodiments which may be comprised in, or a part of, or are further operations which may be taken in addition to the operations of the solid border example embodiments. It should be appreciated that the operations need not be performed in order. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any suitable order and in any combination.

In a first step SI the first wireless node 10 determines a filter to be used for filtering CSI transmitted from the first wireless node to the second wireless node. The filter may be determined in the UE based on several factors. However, the determination may be made in several ways which is outside the scope of the broadest embodiment of this disclosure. The obtaining typically implies reading filter data from a data storage such as a memory. Obtaining may imply calculating the filter information on the fly based on filter parameters. As discussed above, CSI is periodically or aperiodically transmitted from the first wireless node to the second wireless node. Rate or occasion is typically defined in standard. The filter information provides information about filtering of CSI, performed in the first wireless node before the CSI is transmitted to the second wireless node. The CSI defines the channel from the second wireless node to the first wireless node.

According to some aspects the CSI comprises at least one of the following CSI elements: Modulation and Coding Scheme, MCS, Signal to Noise Ratio, SNR, Signal to Interference and Noise Ratio, SINR, Channel Quality Index, CQI, Rank Indicator, Rl, Precoder Matrix Index, PMI, or functions thereof. In step SI the first wireless node uses one or more criteria to determine the filter properties used for filtering CSI. Criteria that may be used for determining the filter will be exemplified below. According to some aspects, the UE selects time period or filtering length used for filtering CSI reported by the first wireless node.

According to some aspects the determining SI comprises selecting a filter g out of a set of pre- defined filters g_l,g_2,...,g_F that are stored in the first wireless node 10. If the pre-defined filters are known by the wireless node receiving the CSI, then the filter information is e.g. an index that is sent to the wireless node receiving the CSI.

According to some aspects the determining SI is based on channel properties of the dynamic wireless channel between the first wireless node 10 and a second wireless node 20. An example is a Doppler frequency f_max defining the Doppler spectrum spread, see Figure 4b, of a dynamic wireless channel H between the first wireless node 10 and a second wireless node 20.

The following criteria for selecting filters could be considered as examples:

• Based on channel properties such as signal strength, interference, estimated maximum Doppler spread apply a constant coefficient to the maximum Doppler shift to calculate the time unit/filter length.

• UE speeds can also be used as criteria.

• A priori known data such as, but not limited to, carrier frequency, channel estimate sampling period and also system properties and requirements. The first wireless node may use any combination of the criteria mentioned above to decide the time unit used for filtering.

Hence, the first wireless node could determine the filter type from the implementation of the receiver where the filter type can be considered as one or more of the followings filter type examples:

Averaging in time domain

The first wireless node could compute the statistical characteristics of the certain elements over time unit. The main statistical characteristics can be average and variance.

The following examples where the elements are taken as CSI can be used as a statistical calculation of averaging in time domain:

yL_ csi(i)

Average CSI(n) =CSIavg(n) = ^1-1 , where L is the filter length.

Standard deviation(n) =CSIstd(n)=

The UE can store the followin quantities

and the statistical quantities above mentioned becomes

Average CQI(n) = A(n) and Standard deviation(n) = V⁵(ⁿ) ^" (^A(ⁿ))

If the average length is over whole connected time the terms A(n+1) and B(n+1) can be derived at time n+1 for example as follows

A(n) * n + CSI(n + 1)

A(n+1) =

n + 1

_{B(n+1) =} g(^ ₊ (CS/( + l))²

n + l

Other examples

IIR/AR filter with filter coeffic

CSI(n + 1) = a(k)CSI(n - k) + CSI(n + 1)

k=0

MA filter with filter coefficients CSI(n + 1) = ^ b(k)CSI(n + 1 - k)

ARMA filter with filter coefficients

L L

CSI(n + 1) = - ^ a(k)CSI(n - k) + ^ b(k)CSI(n + 1 - k)

k=0 k=0

The filter coefficients are e.g. determined based on the channel properties. How to determine the filter properties is outside the scope of this disclosure. The filter type and coefficient may store in the memory of the first wireless node where the information can be obtained directly from the memory. The above given is not limiting by filtering, but can also be applied to interpolation and prediction.

The proposed method comprises the step of obtaining S2 filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic channel and transmitting S3 the filter information to the second wireless node 20. Stated differently, a first wireless node determines the filtering information of channel status by the first wireless node and indicates the associated information to a first wireless node and/or to a second wireless node. Filter information is information that is defining or identifying the filter, or at least some filter properties such as filter length. The term filter herein also comprises interpolation and prediction filters.

In the obtaining step S2 the first wireless node uses one or more criteria to determine filtering information of channel status from the first wireless node. The information can contain the following elements:

The time period the first wireless node uses to do filtering

The filtered element the first wireless node uses filter to

The filtering type the first wireless node applies

The channel status will further be defined below.

In the transmitting step S3, the first wireless node transmits the filter information e.g. information defining the value of the filter information parameter for each carrier. Filter (or filtering) information may be piggy backed on data. Piggybacking practically means that instead of sending an acknowledgement in an individual frame it is piggy-backed on a data frame. Thus, filter data may be transmitted in sub frames where there are other uplink transmissions (e.g. Physical Shared Channel, PUSCH, in LTE). Filter information may also be transmitted in a control channel (e.g. Physical Control Channel, in LTE PUCCH). Transmitting the filter information on the control channel may require modifications of the present PUCCH due to size. The aspects related to the reporting of the said information are described below:

Reporting mechanisms

In one aspect of this embodiment the first wireless node may report the said filtering information proactively or autonomously whenever the first wireless node determines any change in the value of filtering information parameter, or periodically or whenever the first wireless node sends uplink feedback information (e.g. HARQ. feedback, measurement report etc.).

In another aspect of this embodiment the first wireless node may report the said information upon receiving a request from the first or the second wireless node to transmit the said information related to the value of filtering information parameter. In yet another aspect of this embodiment the first wireless node may be requested by the first or the second wireless node to report the said information only if there is any change in the value of the filtering information parameter for per carrier, with respect to the previously determined value of the parameter for per carrier. In another aspect of this embodiment the first wireless node may only report the said information when the estimated maximum Doppler shift is beyond certain threshold. This is due to the fact the filtering information will be only useful when the speed of first wireless node is above a certain level so the reported channel status is outdated with feedback delay.

The first wireless node may report the said information by using any of the following mechanisms: - In a first type of reporting mechanism, the first wireless node may transmit the said information in a higher layer signaling such as via RRC message to the first wireless node or to the second wireless node. Such information may also be reported in a MAC message.

- In a second type of reporting mechanism, the first wireless node may also use the unused bits or code words or fields or control space or bit pattern or bit combinations (also known as spared, reserved, redundant bits or code words or control space or bit pattern or bit combinations etc.) for indicating the information related to the determined parameter for per carrier to the first or the second wireless node. Typically using this mechanism the first wireless node sends the determined information to the second wireless node (e.g. to the serving base station). The unused bits herein means any set of available bits in an uplink control channel that are not used for indicating the UE about any of uplink transmission parameters e.g. are not used for indicating uplink feedback information such as CSI related information or combined with uplink data and sent by uplink data channel.

Validity of reported information

The information about the value of the filtering information for per carrier reported by the first wireless node to the first or the second wireless nodes may be considered valid by the first and the second wireless nodes for certain time period or time unit. Examples of time unit are sub frame, TTI, time slot, frames etc. This may be determined based on one or more predefined rule and/or indication from the first wireless node. Examples of such rules or indications for determining the validity of the said information are: - I nformation is valid only in time unit in which the information is received at the network node;

Last received information remains valid until the reception of the new information at the network node;

I nformation is valid for L number of time units starting from a reference time, T, where T can be time when the information is received, a reference time unit (e.g. SFN = 0) etc.

I nformation received in certain time unit (e.g. sub frame n) is valid or applicable for sub frame n+m, where m is 1 or more integer value.

According to some aspects the method further comprises adjusting (S6) the CSI reporting rate based on the determined filter. When CSI is filtered before transmission, the first wireless node may transmit the CSI less often, because the CSI value will change very slowly or maybe not at all between two sub frames. This is typically controlled by the second wireless node, which informs the first wireless node about the new rate.

Obtaining filtering length

According to some aspects, the filter information transmitted to the second wireless node comprises time period for the filtering or a filtering length. The information about the value of filtering length for per carrier reported by the first wireless node to the first or the second wireless nodes can be taken as relative time units such as number of DL sub frames, TTI, time slot, frames, etc. Alternative of value of the filtering length can be taken as absolute time unit such as ms, s, etc. The filtering length is above noted as L. Obtaining filtering type applied from the first wireless node

The first wireless node could obtain or determine the filter type from the implementation of the receiver where such information can be stored in the memory of first wireless node. Hence, according to some aspects the reported filter information defines a filter type used by the first wireless node. The metrics or properties used for determining the filter in step SI above are all derived from the channel and interference. For example, expressed as the signal-to-noise-and-interference ratio (SINR):

SINR = |H|²/s² for a Single-input-single-output (SISO) channel. The Shannon capacity C for a SISO channel with bandwidth BW is

C = BW x log₂ (l + SINR)

The information of filtering type may contain the filter type and the filter coefficients. Above CSI(n) is used in the equations, CSI(n) could be replaced with the metric representing the filtering type.

The value representing filtering type, may contain indexes of a look-up table of different filter types and coefficients to be reported from the first wireless node. And filtering type may include more than one type of filtering used from the first wireless node. Filter type may include if it is an interpolation or prediction filter or information whether it is a MR or FIR filter.

According to some aspects, the methods further comprises the first wireless node applying S4 the filter on one or more CSI values, and transmits S5 the one or more filtered CSI values to the second wireless node 20. Current LTE standard for CSI reporting is optimized for low mobility scenarios. Future enhancement of LTE may include high mobility CSI reporting enhancements. Obtaining the filtered element the first wireless node uses filter to

According to some aspects the filter information defines a CSI element (or elements) to which the filter is applied. The information of the filtered element may contain the filtered elements which reflect the channel status. The examples of such elements can be estimated channel estimation, mutual information, Symbol information, Shannon capacity, Channel power, SINR, CQI, PMI, Rl, etc.

Example Node Configuration of Second wireless node

Figure 5 illustrates an example of a second wireless node 20 which may incorporate some of the example node operation embodiments discussed above. The second wireless node is e.g. a network node such as a base station or eNodeB. As shown in Figure 5, the second wireless node 20 may comprise a radio circuitry 21 configured to receive and transmit any form of communications or control signals within a network. It should be appreciated that the radio circuitry 11 may be comprised as any number of transceiving, receiving, and/or transmitting units or circuitry. It should further be appreciated that the radio circuitry 21 may be in the form of any input/output communications port known in the art. The radio circuitry 11 may comprise RF circuitry and baseband processing circuitry (not shown).

If the second wireless node is an eNodeB, then the second wireless node typically further comprises a network communication. The network communication interface 23 configured for communication with other network nodes. This communication is often wired e.g. using fiber. However, it may as well be wireless. The connection between network nodes is generally referred to as the backhaul.

The second wireless node 20 may further comprise at least one memory unit or circuitry 24 that may be in communication with the radio circuitry 21. The memory 24 may be configured to store received or transmitted data and/or executable program instructions. The memory 24 may also be configured to store any form of beam-forming information, reference signals, and/or feedback data or information. The memory 24 may be any suitable type of computer readable memory and may be of volatile and/or non-volatile type. According to some aspects, the disclosure relates to a computer program comprising computer program code which, when executed in a first wireless node, causes the first wireless node to execute any aspect of the example node operations described above. The second wireless node 20 may further comprise further processing circuitry 22 which may be configured to cause the second wireless node to receive, from the first wireless node, filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel. The second wireless node is further configured to cause second wireless node to transmit data to the first wireless node over the dynamic wireless channel, and to receive, from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter. In accordance with the proposed methods, the processing circuitry is adapted to transmit data to the first wireless node and/or the receive CSI, based on the received filter information. The processing circuitry 22 may be any suitable type of computation unit, e.g. a microprocessor, digital signal processor (DSP), field programmable gate array (FPGA), or application specific integrated circuit (ASIC) or any other form of circuitry. It should be appreciated that the processing circuitry need not be provided as a single unit but may be provided as any number of units or circuitry. The processing circuitry is further adapted to execute all aspects of the methods in a second wireless node described above.

According to some aspects the processing circuitry comprises modules configured to perform the methods described above. Hence, according to some aspects, the processing circuitry 22 comprises a receiver module 221 configured to receive, from a first wireless node 10, filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic channel. The processing circuitry 22 further comprises a module 222 configured to use the received information when transmitting data to the first wireless node.

Example Node Configuration of First Wireless Node

Figure 6 illustrates an example of a first wireless node 10 which may incorporate some of the example node operation embodiments discussed above. As shown in Figure 6, the first wireless node 10 may comprise a radio circuitry 11 configured to receive and transmit any form of communications or control signals within a network. It should be appreciated that the radio circuitry 11 may be comprised as any number of transceiving, receiving, and/or transmitting units or circuitry. It should further be appreciated that the radio circuitry 11 may be in the form of any input/output communications port known in the art. The radio circuitry 11 may comprise RF circuitry and baseband processing circuitry (not shown). The first wireless node 10 may further comprise at least one memory unit or circuitry 13 that may be in communication with the radio circuitry 11. The memory 13 may be configured to store received or transmitted data and/or executable program instructions. The memory 13 may also be configured to store any form of beam-forming information, reference signals, and/or feedback data or information. The memory 13 may be any suitable type of computer readable memory and may be of volatile and/or non-volatile type.

According to some aspects, the disclosure relates to a computer program comprising computer program code which, when executed in a first wireless node, causes the first wireless node to execute any aspect of the example node operations described above. The first wireless node 10 may further comprise further processing circuitry 12 which may be configured to cause the first wireless node to obtain filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, corresponding to the dynamic channel, and to transmit the filter information to the second wireless node 20.

The processing circuitry 12 may be any suitable type of computation unit, e.g. a microprocessor, digital signal processor (DSP), field programmable gate array (FPGA), or application specific integrated circuit (ASIC) or any other form of circuitry. It should be appreciated that the processing circuitry need not be provided as a single unit but may be provided as any number of units or circuitry. The processing circuitry is further adapted to execute all aspects of the methods in a second wireless node described above. According to some aspects the processing circuitry comprises modules configured to perform the methods described above. Hence, according to some aspects, the processing circuitry 12 comprises an obtainer 121 configured to obtain filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, corresponding to the dynamic channel, and a transmitter module 122 configured for transmitting the filter information to the second wireless node 20.

According to some aspects, the disclosure relates to a computer program comprising computer program code which, when executed in a first wireless node, causes the first wireless node to execute the methods according to any of the embodiments described below and above. Figure 9 illustrates a wireless network comprising a more detailed view of network node 200 and wireless device (WD) 210, in accordance with a particular embodiment. For simplicity, Figure 9 only depicts network 220, network nodes 200 and 200a, and WD 210. Network node 200 comprises processor 202, storage 203, interface 201, and antenna 201a. Similarly, WD 210 comprises processor 212, storage 213, interface 211 and antenna 211a. These components may work together in order to provide network node and/or wireless device functionality. In different embodiments, the wireless network may comprise any number of wired or wireless networks, network nodes, base stations, controllers, wireless devices, relay stations, and/or any other components that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections.

Network 220 may comprise one or more IP networks; public switched telephone networks (PSTNs), packet data networks, optical networks, wide area networks (WANs), local area networks (LANs), wireless local area networks (WLANs), wired networks, wireless networks, metropolitan area networks, and other networks to enable communication between devices. Network node 200 comprises processor 202, storage 203, interface 201, and antenna 201a. These components are depicted as single boxes located within a single larger box. In practice however, a network node may comprises multiple different physical components that make up a single illustrated component (e.g., interface 201 may comprise terminals for coupling wires for a wired connection and a radio transceiver for a wireless connection). Similarly, network node 200 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, a BTS component and a BSC component, etc.), which may each have their own respective processor, storage, and interface components. In certain scenarios in which network node 200 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeB's. In such a scenario, each unique NodeB and BSC pair, may be a separate network node. In some embodiments, network node 200 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate storage 203 for the different RATs) and some components may be reused (e.g., the same antenna 201amay be shared by the RATs). Processor 202 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 200 components, such as storage 203, network node 200 functionality. For example, processor 202 may execute instructions stored in storage 203. Such functionality may include providing various wireless features discussed herein to a wireless devices, such as WD 210, including any of the features or benefits disclosed herein.

Storage 203 may comprise any form of volatile or non-volatile computer readable memory including, without limitation, persistent storage, solid state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), removable media, or any other suitable local or remote memory component. Storage 203 may store any suitable instructions, data or information, including software and encoded logic, utilized by network node 200. Storage 203 may be used to store any calculations made by processor 202 and/or any data received via interface 201.

Network node 200 also comprises interface 201 which may be used in the wired or wireless communication of signaling and/or data between network node 200, network 220, and/or WD 210. For example, interface 201 may perform any formatting, coding, or translating that may be needed to allow network node 200 to send and receive data from network 220 over a wired connection. Interface 201 may also include a radio transmitter and/or receiver that may be coupled to or a part of antenna 201a. The radio may receive digital data that is to be sent out to other network nodes or WDs via a wireless connection. The radio may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters. The radio signal may then be transmitted via antenna 201a to the appropriate recipient (e.g., WD 210).

Antenna 201a may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In some embodiments, antenna 201a may comprise one or more omnidirectional, sector or panel antennas operable to transmit/receive radio signals between, for example, 2 GHz and 66 GHz. An omni-directional antenna may be used to transmit/receive radio signals in any direction, a sector antenna may be used to transmit/receive radio signals from devices within a particular area, and a panel antenna may be a line of sight antenna used to transmit/receive radio signals in a relatively straight line.

WD 210 may be any type of wireless endpoint, mobile station, mobile phone, wireless local loop phone, smartphone, user equipment, desktop computer, PDA, cell phone, tablet, laptop, VoIP phone or handset, which is able to wirelessly send and receive data and/or signals to and from a network node, such as network node 200 and/or other WDs. WD 210 comprises processor 212, storage 213, interface 211, and antenna 211a. Like network node 200, the components of WD 210 are depicted as single boxes located within a single larger box, however in practice a wireless device may comprises multiple different physical components that make up a single illustrated component (e.g., storage 213 may comprise multiple discrete microchips, each microchip representing a portion of the total storage capacity).

Processor 212 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in combination with other WD 210 components, such as storage 213, WD 210 functionality. Such functionality may include providing various wireless features discussed herein, including any of the features or benefits disclosed herein.

Storage 213 may be any form of volatile or non-volatile memory including, without limitation, persistent storage, solid state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), removable media, or any other suitable local or remote memory component. Storage 213 may store any suitable data, instructions, or information, including software and encoded logic, utilized by WD 210. Storage 213 may be used to store any calculations made by processor 212 and/or any data received via interface 211.

Interface 211 may be used in the wireless communication of signaling and/or data between WD 210 and network node 200. For example, interface 211 may perform any formatting, coding, or translating that may be needed to allow WD 210 to send and receive data from network node 200 over a wireless connection. Interface 211 may also include a radio transmitter and/or receiver that may be coupled to or a part of antenna 211a. The radio may receive digital data that is to be sent out to network node 201 via a wireless connection. The radio may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters. The radio signal may then be transmitted via antenna 211a to network node 200.

Antenna 211a may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In some embodiments, antenna 211a may comprise one or more omnidirectional, sector or panel antennas operable to transmit/receive radio signals between 2 GHz and 66 GHz. For simplicity, antenna 211a may be considered a part of interface 211 to the extent that a wireless signal is being used.

In some embodiments, the components described above may be used to implement one or more functional modules used in reporting filtering information of channel status. The functional modules may comprise software, computer programs, sub-routines, libraries, source code, or any other form of executable instructions that are run by, for example, a processor. In general terms, each functional module may be implemented in hardware and/or in software. Preferably, one or more or all functional modules may be implemented by processors 212 and/or 202, possibly in cooperation with storage 213 and/or 203. Processors 212 and/or 202 and storage 213 and/or 203 may thus be arranged to allow processors 212 and/or 202 to fetch instructions from storage 213 and/or 203 and execute the fetched instructions to allow the respective functional module to perform any features or functions disclosed herein. The modules may further be configured to perform other functions or steps not explicitly described herein but which would be within the knowledge of a person skilled in the art.

Certain aspects of the inventive concept have mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, embodiments other than the ones disclosed above are equally possible and within the scope of the inventive concept. Similarly, while a number of different combinations have been discussed, all possible combinations have not been disclosed. One skilled in the art would appreciate that other combinations exist and are within the scope of the inventive concept. Moreover, as is understood by the skilled person, the herein disclosed embodiments are as such applicable also to other standards and communication systems and any feature from a particular figure disclosed in connection with other features may be applicable to any other figure and or combined with different features. Aspects of the disclosure are described with reference to the drawings, e.g., block diagrams and/or flowcharts. It is understood that several entities in the drawings, e.g., blocks of the block diagrams, and also combinations of entities in the drawings, can be implemented by computer program instructions, which instructions can be stored in a computer-readable memory, and also loaded onto a computer or other programmable data processing apparatus. Such computer program instructions can be provided to a processor of a general purpose computer, a special purpose computer and/or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.

In some implementations and according to some aspects of the disclosure, the functions or steps noted in the blocks can occur out of the order noted in the operational illustrations. For example, two blocks shown in succession can in fact be executed substantially concurrently or the blocks can sometimes be executed in the reverse order, depending upon the functionality/acts involved. Also, the functions or steps noted in the blocks can according to some aspects of the disclosure be executed continuously in a loop.

In the drawings and specification, there have been disclosed exemplary aspects of the disclosure. However, many variations and modifications can be made to these aspects without substantially departing from the principles of the present disclosure. Thus, the disclosure should be regarded as illustrative rather than restrictive, and not as being limited to the particular aspects discussed above. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other. It should be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the embodiments, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

The various example embodiments described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program modules may include routines, programs, objects, components, data structures, etc. that performs particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

ABBREVIATIONS

MIMO Multiple input multiple output

HSDPA High Speed Downlink Packet Access

LTE Long term evolution HARQ Hybrid automatic repeat request

CRC Cyclic redundancy check

NACK non-acknowledgement

ACK acknowledgement

UE User Equipment

ecu Channel quality information

TTI Transmit Time Interval

PUCCH Physical uplink control channel

PUSCH Physical uplink data channel

PMI Precoder Matrix Index

Rl Rank Indication

CSI Channel Status Information eNodeB Evolved or enhanced Node B

Claims

A method performed in a second wireless node (20) that is configured to transmit data to a first wireless node (10) over a dynamic wireless channel, the method comprising:

receiving (Sll), from the first wireless node (10), filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel,

transmitting (S12a) data to the first wireless node over the dynamic wireless channel, and

receiving (S12b), from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter,

wherein the transmission (S12a) of data to the first wireless node and/or the reception (S12b) of CSI from the first wireless node, is based on the received filter information.

The method of claim 1, wherein the second wireless node adjusts its own filtering when receiving (S12b) CSI, based on the filter information.

The method of any of the preceding claims, wherein the second wireless node schedules, the same rank, precoder and/or MCS during a certain time, based on the filter information, when transmitting (S12a) data to the first wireless node.

The method of any of the preceding claims, wherein the second wireless node forwards the information to other wireless nodes.

The method of any of the preceding claims, wherein the second wireless node adjusts CSI reporting or processing rate, based on the filter information, when transmitting (S12a) data to the first wireless node.

The method of any of the preceding claims, wherein the filter information comprises a time period for the filtering or a filter length.

The method of any of the preceding claims, wherein the CSI comprises at least one of the following CSI elements: Modulation and Coding Scheme, MCS, Signal to Noise Ratio, SNR, Signal to Interference plus Noise Ratio, SINR, Rank Indicator, Rl, Precoder Matrix Index, PMI, or functions thereof.

The method of any of the preceding claims, wherein the filter information defines one or more CSI element to which the filter is applied.

The method of any of the preceding claims, wherein the filter information defines a filter type.

The method of any of claim 9, wherein the filter information defines one filter g out of a set of pre-defined filters g_lt g₂, ... , g_F , that are known to the second wireless node.

A computer program comprising computer program code which, when executed in a second wireless node, causes the second wireless node to execute the methods according to any of claims 1-10.

A second wireless node (20) configured to transmit data to a first wireless (10) node over a dynamic wireless channel, the second wireless node (20) comprising:

radio circuitry (21) adapted to transmit and receive radio signals over the dynamic wireless channel and

processing circuitry (22) adapted:

• to receive, from the first wireless node (10), filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel,

• to transmit data to the first wireless node over the dynamic wireless channel, and

• to receive, from the first wireless node, CSI corresponding to the transmission, wherein the CSI is filtered with the filter, wherein the processing circuitry is adapted to transmit data to the first wireless node and/or the receive CSI, based on the received filter information.

13. The second wireless node of the claim 12, wherein the second wireless node is a network node.

A method performed in a first wireless node (10) that is configured for receiving data from a second wireless node over a dynamic wireless channel, the method comprising:

obtaining (S2) filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, describing the dynamic wireless channel, and

transmitting (S3) the filter information to the second wireless node (20).

The method of claim 14, further comprising:

determining (SI) a filter to be used for filtering CSI transmitted from the first wireless node to the second wireless node

applying (S4) the filter on one or more CSI values, and

transmitting (S5) the one or more filtered CSI values to the second wireless node (20).

The method of any of claim 13 or 14, wherein the determining (SI) comprises selecting a filter g out of a set of pre-defined filters g₁, g₂,—, g_F ^{tnat a re} stored in the first wireless node (10).

The method of any of the preceding claims 14-16, wherein the method further comprises:

adjusting (S6) CSI reporting rate based on the determined filter. 18. A computer program comprising computer program code which, when executed in a first wireless node, causes the first wireless node to execute the methods according to any of the claims 14-17.

A first wireless node (10) configured for receiving data from a second wireless node (20) over a dynamic wireless channel, the first wireless node comprising:

radio circuitry (11) adapted to receive a radio signal transmitted over the dynamic wireless channel and processing circuitry (12) adapted to:

• obtain filter information defining a filter that is used in the first wireless node, for filtering Channel State Information, CSI, corresponding to the dynamic wireless channel, and

• transmit the filter information to the second wireless node (20).

20. The first wireless node of claim 19, wherein the first wireless node is a User Equipment, UE.