WO2019048050A1

WO2019048050A1 - Indicating phase tracking reference signal pattern

Info

Publication number: WO2019048050A1
Application number: PCT/EP2017/072531
Authority: WO
Inventors: Sergei Semenov; Neng Wang; Wenquan HU; Chaitanya TUMULA; Bengt Lindoff; Thanos DIMITRIOU
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-09-07
Filing date: 2017-09-07
Publication date: 2019-03-14

Abstract

Additional indication, such as signaling, may be used for allowing a client device to assist a network access device in the selection of an appropriate PTRS pattern for wireless communication. The client device may request the network access device to provide a certain PTRS pattern. For example, the client device sends a request on a particular PTRS pattern, taking into account channel conditions and the estimated PN model. An indicator set having indicators is used to signal the certain PTRS pattern. If the current radio channel conditions and estimated PN coefficients show that estimation of more PN coefficients can improve the performance, the client device sends a request to provide a PTRS pattern with higher burst length.

Description

INDICATING PHASE TRACKING REFERENCE SIGNAL PATTERN

TECHNICAL FIELD

[0001 ] The present application relates to the field of wireless radio communications, and more particularly to indicating a phase tracking reference signal, PTRS, pattern for wireless radio communication.

BACKGROUND

[0002] Phase noise, PN, is inherently present in oscillators, and its effect is equivalent to a random phase modulation of the carrier of wireless communications. In general, PN is present at both a client device and a network access device of a wireless communication system, each having both a transmitter and a receiver.

[0003] It is a well-known fact that uncompensated PN with a high carrier frequency may seriously degrade the performance of multi-carrier based wireless communication such as cyclic-prefix orthogonal frequency division modulation, CP- OFDM, based transmission. Phase tracking reference signals, PTRS, may be used in new radio, NR, to assist PN estimation and compensation. However, the current PTRS patterns signaling only comprises a set of unharmonized features. It does not use resources for signaling in an optimal way.

SUMMARY

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0005] It is an object to provide to improve PTRS pattern signaling. The object is achieved by the features of the independent claims. Further implementation forms are provided in the dependent claims, the description and the figures.

[0006] According to a first aspect, a client device is configured to: provide an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern to a network access device, wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length; and obtain, from the network access device, information about a PTRS pattern scheduled for a downlink transmission. The client device may assist the network access device in the choice of the appropriate PTRS pattern. The appropriate PTRS pattern may be based on client device characteristics, network access device characteristics, radio channel conditions and phase noise, PN, model. The usage of the resource for the PTRS signaling may be improved. Based on the assistance, system performance may be improved for the NR. According to an embodiment, the PTRS burst length may be defined as a number of consecutive resource elements in the frequency dimension carrying PTRSs belonging to the same PTRS port.

[0007] In a further implementation form of the first aspect, the uplink indicator set further comprises a static part and a dynamic part; and the PTRS burst length associated with the localized PTRS pattern is configured to be indicated using the static part or the dynamic part. The static part may be related to predetermined or static characteristics, while the dynamic part may depend on current downlink radio channel characteristic or estimated PN. Either one of the parts may convey the burst length information.

[0008] In a further implementation form of the first aspect, the static part of the uplink indicator set further comprises information about at least one of client device capability and client device radio frequency, RF, characteristics, wherein the client device capability indicates whether the client device can benefit from an inter carrier interference, ICI, compensation using the localized PTRS pattern. Client device capabilities can be indicated to the network access device for the choice of the appropriate PTRS pattern for the client device. The client device can indicate the ICI compensation capabilities to the network access device.

[0009] In a further implementation form of the first aspect, the client device RF characteristics comprise a bitmap indicating an association between receiving antennas of the client device and phase locked-loops, PLLs of the client device. The client device can use the bitmap to indicate the association to the network access device. The network access device may receive the association and take the association into account for selecting and scheduling the PTRS pattern.

[001 0] In a further implementation form of the first aspect, the dynamic part of the uplink indicator set further comprises information about whether the client device prefers the localized or the distributed PTRS pattern. The client device can indicate the preferred PTRS pattern to the network access device. Consequently, better system performance may be achieved.

[001 1 ] In a further implementation form of the first aspect, the dynamic part of the uplink indicator set further comprises information about preferred radio resources for the localized PTRS, in case the client device prefers the localized PTRS pattern. The client device can indicate the preferred radio resource using the dynamic part.

[001 2] In a further implementation form of the first aspect, the preferred radio resources for the localized PTRS pattern are configured to be indicated using an offset of a PTRS subcarrier in a scheduled bandwidth. The applicable radio resource may be designated by the offset value. Consequently, the offset value may be used in downlink, DL to improve the performance of the system.

[001 3] In a further implementation form of the first aspect, the client device is configured to signal the static part or the dynamic part using radio resource control, RRC, medium access control, control element, MAC-CE, or uplink control information, UCI. Standardized communication protocols may be used to communicate the static or the dynamic parts.

[001 4] In a further implementation form of the first aspect, the obtained information about the scheduled PTRS pattern comprises at least one of information about network access device radio frequency, RF, characteristics, and information of whether the localized or the distributed PRTS pattern is scheduled. The network access device can indicate the RF characteristics to the client device. Also, the network access device can indicate whether the localized or the distributed PTRS pattern is scheduled. This may improve the system performance.

[001 5] In a further implementation form of the first aspect, the client device is further configured to obtain further information about the burst length of the scheduled localized PTRS pattern and radio resources for the scheduled localized PTRS pattern, in case the localized PTRS pattern is scheduled. Appropriate burst length for the scheduled PTRS pattern can be effectively utilized in the system.

[001 6] In a further implementation form of the first aspect, the client device is further configured to obtain a downlink indicator set corresponding to the scheduled PTRS pattern, wherein the client device is configured to obtain the dynamic part of the downlink indicator set implicitly using predefined thresholds based on channel characteristics, wherein the channel characteristics include both the radio channel conditions and phase noise model. The client device may obtain the downlink indicator set implicitly based on predefined communication.

[001 7] According to a second aspect, a network access device is configured to: obtain, from a client device, an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern, wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length; based on the received uplink indicator set, determine the PTRS pattern; convey, to the client device, a downlink indicator set comprising information about the determined PTRS pattern; and schedule the determined PTRS pattern. The network access device can select an appropriate PTRS pattern and indicate the scheduled PTRS pattern to the client device. This can be based on the client device's indication for an appropriate PTRS pattern. For example, the appropriate PTRS pattern may be based on client device characteristics and channel characteristics. The usage of the resource for the PTRS signaling may be improved. Based on the appropriate PTRS pattern, system performance may be improved.

[001 8] In a further implementation form of the second aspect, the downlink indicator set contains a static part and a dynamic part; and the PTRS burst length associated with the scheduled localized PTRS pattern is configured to be indicated using the static part or the dynamic part. The static part may be related to predetermined or static characteristics, while the dynamic part may depend on current downlink radio channel characteristic or estimated PN. Either one of the parts may convey the burst length information. [001 9] In a further implementation form of the second aspect, the static part of the downlink indicator set comprises information about the network access device RF characteristics, wherein the network access device RF characteristics comprise a number of PTRS ports of the network access device assigned to a particular client device; and/or a bitmap associating the PTRS ports and the PLLs of the network access device. The network access device radio features can be directly coupled and indicated to the client device for utilization in the DL.

[0020] In a further implementation form of the second aspect, the dynamic part of the downlink indicator set is configured to indicate whether the localized or distributed PTRS pattern is scheduled. The network access device indicates the scheduled PTRS pattern to the client device. Consequently, better system performance may be achieved.

[0021 ] In a further implementation form of the second aspect, the dynamic part of the downlink indicator set further comprises information about radio resources allocated for the scheduled localized PTRS, in case the localized PTRS pattern is scheduled. The localized PTRS may be susceptive to a frequency-selective fading. Therefore, the possibility to allocate different radio resources for localized PTRS improves the PTRS quality.

[0022] In a further implementation form of the second aspect, the network access device is further configured to indicate an offset of a PTRS subcarrier in a scheduled bandwidth. A value of the offset of the PTRS subcarrier can be explicitly indicated to the client device.

[0023] In a further implementation form of the second aspect, the network access device is configured to signal at least one of the static part and the dynamic part of the downlink indicator set using radio resource control, RRC, medium access control, control element, MAC-CE, or downlink control information, DCI. Standardized communication protocols can convey the static and the dynamic part. There may be no need to define additional protocols.

[0024] In a further implementation form of the second aspect, the obtained uplink indicator set comprises information about client device radio frequency, RF, characteristics, and information of whether the localized or the distributed PTRS pattern is to be used. The network access device is further configured to obtain further information about the burst length of the preferred localized PTRS pattern and preferred radio resources for the localized PTRS pattern, in case the localized PTRS pattern is preferred by the client device. The network access device can indicate the RF characteristics of the network access device to the client device. This may improve the system performance.

[0025] In a further implementation form of the second aspect, the network access device is further configured to obtain further information about the burst length of the preferred localized PTRS pattern and preferred radio resources for the localized PTRS pattern, in case the localized PTRS pattern is preferred by the client device. The preferred localized PTRS pattern may be enhanced by further details for burst length and for the radio resources.

[0026] In a further implementation form of the second aspect, the network access device is further configured to obtain the dynamic part of the uplink indicator set implicitly using predefined thresholds based on channel characteristics. The network access device can implicitly determine the dynamic part of the UL indicator set without a need for signaling, for example from predefined communications.

[0027] According to a third aspect, a method comprises: providing, to a network access device, an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern, wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length; and obtaining, from the network access device, information about the PTRS pattern scheduled for a downlink transmission.

[0028] According to a fourth aspect, a method comprises: obtaining, from a client device, an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern, wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, at least one indicator indicates a PTRS burst length; based on the received uplink indicator set, determining the PTRS pattern; conveying a downlink indicator set comprising information about the determined PTRS pattern; and scheduling the determined PTRS pattern. [0029] According to a fifth aspect, a computer program is provided, comprising program code configured to perform a method according to the third or fourth aspect when the computer program is executed on a computer.

[0030] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0031 ] The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein:

[0032] FIG. 1 illustrates a schematic representation of a block diagram of a client device configured to indicate a PTRS pattern according to an embodiment;

[0033] FIG. 2 illustrates a schematic representation of a block diagram of a network access device configured to indicate a scheduled PTRS pattern according to an embodiment;

[0034] FIG. 3 illustrates a schematic representation of distributed PTRS patterns according to an embodiment;

[0035] FIG. 4 illustrates a schematic representation of localized PTRS patterns according to an embodiment;

[0036] FIG. 5 illustrates a flowchart of a method of indicating a PTRS pattern for downlink, DL, according to an embodiment;

[0037] FIG. 6 illustrates a flowchart of a method of indicating a PTRS pattern for uplink, UL, according to an embodiment; and

[0038] FIG. 7 illustrates a schematic representation of a signaling diagram for indicating a PTRS pattern between a client device and a network access device according to an embodiment.

[0039] Like references are used to designate like parts in the accompanying drawings. DETAILED DESCRIPTION

[0040] The detailed description provided below in connection with the appended drawings is intended as a description of the embodiments and is not intended to represent the only forms in which the embodiment may be constructed or utilized. However, the same or equivalent functions and structures may be accomplished by different embodiments.

[0041 ] Additional indication, such as signaling, may be used for allowing a client device 100 to assist a network access device 200 in the selection of an appropriate PTRS pattern for wireless communication. The client device 100 may request the network access device 200 to provide a certain PTRS pattern. For example, the client device 100 sends a request on a particular PTRS pattern, taking into account radio channel conditions and the estimated PN model. An indicator set having indicators, which may be alternatively referred to as parameters, is used to signal the certain PTRS pattern. If the current radio channel conditions and estimated PN coefficients show that the estimation of more PN coefficients can improve the performance, the client device 100 sends a request to provide a PTRS pattern with a higher burst length.

[0042] According to an embodiment, a client device 100 transmits, to the network access device 200, an uplink (UL) indicator set. The uplink indicator set includes one or more indicators related to a localized or distributed phase tracking reference signal, PTRS, pattern. The UL indicator set may be split into a static and a dynamic part. The dynamic part of the UL indicator set may also be conveyed implicitly, for example by utilizing predetermined rules specified in a standard specification. That means, instead of explicitly receiving the information, the network access device 200 may obtain the part of information about requested PTRS pattern implicitly. When the PTRS pattern is the localized PTRS pattern, the client device 100 can indicate a PTRS burst length to the network access device 200 directly. Furthermore, the client device 100 receives, from the network access device 200, information about a PTRS pattern scheduled for a downlink transmission. The scheduled PTRS pattern may be based on the uplink indicator set, i.e., the network access device 200 may take the uplink indication into account when deciding an appropriate PTRS pattern to be scheduled for the client device 100. [0043] According to another embodiment, a network access device 200 receives, from a client device 100, the uplink indicator set. The uplink indicator set includes one or more indicators related to a localized or distributed phase tracking reference signal, PT S, pattern. When the PTRS pattern is the localized PTRS pattern, the network access device 200 can indicate a PTRS burst length to the client device 100 explicitly. Furthermore, based on the received uplink indicator set, the network access device 200 determines the PTRS pattern. This may be directly based on the UL indicator set. However, the network access device 200 may also override the request sent in UL indicator set. The network access device 200 conveys, to the client device 100, a DL indicator set which has information about the determined PTRS pattern. The network access device 200 schedules the determined PTRS pattern for DL transmission. The DL indicator set may be split into a static and a dynamic part. The dynamic part of the DL indicator set may also be conveyed implicitly, for example by utilizing predetermined rules in a standard specification. That means, instead of direct reception, the client device 100 may obtain the part of information about scheduled PTRS pattern implicitly.

[0044] Signaling operations and features allow the client device 100 to assist the network access device 200 in the choice of the appropriate PTRS pattern. Furthermore, the network access device 200 can indicate the scheduled PTRS pattern to the client device 100, which in turn can provide system performance improvement for the wireless communication, such as the new radio, NR, system. The usage of resources for PTRS signaling may be improved. A more effective way to choose the PTRS pattern with the assistance of the client device 100 can be achieved.

[0045] Fig. 1 schematically shows a client device 100 such as user equipment

UE, which may comprise a processor 101, a receiver 102 and a transmitter 103. Consequently, the client device 100 may be configured to perform the operations and functions of the embodiments. Furthermore Fig. 2 shows schematically a network access device 200, such as a general NodeB, gNB, in a wireless communication system. The network access device 200 comprises a processor 201, a receiver 202 and a transmitter 203. The network access device 200 may be accordingly configured to perform the operations and functions of the embodiments. [0046] The client device 100 may be any of a User Equipment (UE) in Long

Term Evolution (LTE) or New Radio (NR), mobile station (MS), wireless terminal or mobile terminal which is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UE may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice or data via a radio access network with another entity, such as another receiver or a server. The UE can be a Station (STA) which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).

[0047] The network access device 200 may be a transmission or reception point,

TRP, or a 5G base station gNodeB, gNB. The network access device 200 may be a base station, a (radio) network node or an access node or an access point or a base station, e.g., a Radio Base Station (RBS), which in some networks may be referred to as a transmitter, "eNB", "eNodeB", "NodeB" or "B node", depending on the technology and terminology used. The radio network nodes may be of different classes such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network node can be a Station (STA) which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).

[0048] According to an embodiment, an UL indicator set is transmitted from the client device 100 to network access device 200 in the UL. The indicator set having indicators indicates a certain PTRS pattern which the network access device 200 can use in the downlink, DL, transmission. The indicator set may comprise, for example, two parts: a static part and a dynamic part. As an example, the static part indicates whether the client device 100 can benefit from a localized PTRS pattern. Additionally, the static part may provide the network access device 200 some initial information about client device radio frequency, RF, characteristics, for example a bitmap showing an association between the client device receive antennas and PLLs. The static part and the dynamic part may be related to the PN mitigation performance of the client device 100. The dynamic part may indicate, for example, whether the client device 100 prefers a localized or a distributed PTRS pattern. The dynamic part may further indicate a localized PTRS burst length. The dynamic part may further indicate preferred radio resources of the localized PTRS, for example, an offset of a PTRS subcarriers in a scheduled bandwidth, BW. Preferably, the localized PTRS burst length can be included in the static part rather than in the dynamic part.

[0049] The dynamic part of the indicator set may for instance be dependent on current DL radio channel characteristics, SINR, and/or on the estimated PN model.

[0050] The UL indicator set may be transmitted as messages on LI (UCI), L2 (medium access control, control element, MAC-CE), or L3 (radio resource control, RRC). According to another embodiment, the dynamic part of UL indicator set can be provided to the network access device 200 implicitly, for example by utilizing predetermined rules specified in a standard specification.

[0051 ] The network access device 200, on the other hand, may notify the client device 100 about the scheduled PTRS pattern by signaling a DL indicator set having indicators. These indicators may include initial information about network access device 200 RF characteristics, for example the number of PTRS ports. Alternatively or additionally, the indicators comprise a bitmap showing the association between PTRS ports and PLLs in the network access device transmitter 203. Alternatively or additionally, the indicators may also show whether the PTRS pattern is distributed or localized. In case the PTRS pattern is localized, a length of a localized burst and radio resources used for PTRS may be indicated.

[0052] The DL indicator set may comprise a static and a dynamic part. For example, the static part may comprise a number of PTRS ports. Alternatively or additionally, it may comprise a bitmap showing the association between PTRS ports and PLLs in the network access device transmitter 203. Additionally, other information can be considered as dynamic. Preferably, the localized PTRS burst length can be included in the static part rather than in the dynamic part.

[0053] The DL indicator set may be transmitted as messages on LI (DO), L2 (MAC-CE), or L3 (RRC). According to another embodiment, the dynamic part of DL indicator set can be provided to the client device 100 implicitly, for example by utilizing predetermined rules specified in a standard specification.

[0054] According to an embodiment, first signaling in the UL indicator set may provide the network access device 200 information on whether the client device 100 can benefit from the localized PTRS. Additionally, the first signaling may provide information about the RF part of the client device receiver 102 to the network access device 200.

[0055] If the UL indicator set received at the network access device 200 indicates that the receiver 102 of the client device 100 cannot benefit from getting localized PTRS patterns, the network access device 200 sends only distributed PTRS patterns. An example of distributed PTRS patterns is illustrated in FIG. 3.

[0056] Another (static) parameter reported as part of the UL indicator set from the client device 100 to the network access device 200 may reflect a bitmap showing an association between the receive antennas and PLLs of the client device 100. If each RX antenna is connected to an independent PLL, then PN at each antenna is independent and may be estimated separately for each antenna. However, if some RX antennas are connected to the same PLL, then they experience the same realization of the PN process. In this case it is possible to combine the observations from different RX antennas to estimate the PN. Therefore, it is possible to decrease the density of the PTRS pattern to achieve a satisfactory PN compensation performance. If the client device 100 receives more PTRS resources, the client device 100 may do a better PN compensation but in poor radio channel conditions this may not result in a performance improvement. However, one would waste resources in this case. Hence in the case of more than one antenna connected to the same PLL at the client device 100, the network access device 200 can use PTRS patterns with lower density than for client devices where each antenna is connected to an independent PLL.

[0057] Part (e.g. a static part) of the UL indicator set may be reported, for example, as part of the UE category signaled by the client device 100 to the network access device 200. For example, the following two parameters or at least one of them can be added to the UE category definition: [0058] 1) One bit showing whether the client device 100 can benefit from localized PTRS or not.

[0059] 2) Bitmap showing an association between client device 100 receive antennas and PLLs.

[0060] If the client device receiver 102 cannot benefit from localized PTRS, the network access device 200 provides only distributed PTRS patterns since they provide more frequency diversity.

[0061 ] Referring to FIG. 3, a schematic representation of distributed PTRS patterns 310, 310', 310" having different densities according to an embodiment is illustrated. In the examples shown in Fig. 3 and Fig. 4 consecutive is always to be understand as consecutive in frequency dimension. For this example let us assume that a block 300 is defined as 12 consecutive REs in frequency dimension. The 12 REs may be spread over two consecutive resource blocks RB or may form one resource block RB. In the PTRS pattern 310 each block 300 comprises four resource elements REs 301, 302, 303, and 304 carrying the PTRS set for the PTRS for PTRS ports 1, 2, 3, and 4 correspondingly and 8 REs for data 305. In this example the same density is used for all PTRS ports. Hence, in the PTRS pattern 310 a density of the pattern is 1 PTRS per PTRS port per resource block, RB (comprising 12 REs). Compared to this in the PTRS pattern 310' only every second block 300 comprises such PTRS set. Hence the density of the pattern 310' is 1 PTRS per PTRS port per two RBs effectively increasing the achievable data rate. In the PTRS pattern 310" the density of the pattern is 1 PTRS per PTRS port per four RBs. Further increasing the achievable data rate.

[0062] In this non-limiting example, the burst length (in frequency dimension) for the distributed PTRS pattern is always equal to 1 , and it remains the same, although the pattern and the density changes. Furthermore in this example PTRSs corresponding to neighboring PTRS ports occupy consecutive REs. However, in further embodiments the PTRSs corresponding to neighboring PTRS ports may not occupy consecutive REs.

[0063] A common phase error, CPE, may occur in the new radio NR. For example, parts of the signal may be CPE corrupted. The CPE can cause common phase rotation of all subcarrier data inside one OFDM symbol. A special PTRS pattern may be used in the NR to assist PN estimation or compensation. As shown in FIG. 3, PTRS patterns can have different frequency densities (FD) such as: 1 PTRS set (comprising at least one PTRS) in every RB, 1 PTRS set in every 2 RBs or 1 PTRS set in every 4 RBs. These distributed PTRS patterns can be used for CPE estimation or compensation.

[0064] If the client device 100 can benefit from the localized PTRS pattern, then the localized PTRS patterns could be used. FIG. 4 illustrates a schematic representation of localized PTRS patterns 320, 320', 320" according to an embodiment. Examples of localized PTRS patterns 320, 320', 320" are shown with a frequency density 1 PTRS per PTRS port per RB. In pattern 320, a localization burst length (defining the number of consecutive PTRS for a given PTRS port in a PTRS burst, and a PTRS burst, in turn, is defined as a chunk of consecutive REs in frequency dimension assigned to PTRSs of a particular PTRS port) 306 is 3. Consequently, there are three consecutive REs forming a respective PTRS burst 401, 402, 403, 404 for each PTRS port. In pattern 320', a localization burst length 306' is 5, i.e., there are five consecutive REs forming a respective PTRS burst for each PTRS port. In pattern 320", a localization burst length 306" is 7, i.e., there are seven consecutive REs forming a respective PTRS burst for each PTRS port. It should be noted that the numerical values of FIG. 4 may vary depending on the capabilities of the client device 100. For example, the burst length may be 1 1 instead of 7 as shown in FIG. 4. Furthermore, as with the distributed PTRS pattern, PTRS bursts for neighboring PTRS ports may not necessarily occupy neighboring REs. Hence, contrary to the example shown in Fig. 4 PTRS bursts belonging to different PTRS ports may be divided by REs e.g. carrying data. Nevertheless REs belonging to the same PTRS burst shall always be consecutive.

[0065] The inter-carrier interference, ICI, may also occur for the NR. ICI is the inter-carrier interference that every subcarrier causes to each other due to frequency spreading by PN. As discussed, a certain PTRS pattern may be used in the NR to assist PN estimation or compensation. However, if the ICI caused by the PN is not negligible, the compensation of CPE still might not be enough to provide a maximum throughput with a high SNR.

[0066] The distributed PTRS pattern can also be used to estimate not only CPE but a part of inter-carrier interference, ICI, as well. However, one needs much less localized PTRS patterns than distributed PTRS patterns to estimate the same number of PN coefficients corresponding to the ICI. Consequently, with an equal number of PTRS patterns, one can estimate more PN coefficients using a localized PTRS pattern when compared to a distributed PTRS pattern.

[0067] Consequently, if the client device 100 has an advanced receiver 102 capable of ICI estimation and compensation, a localized PTRS pattern could be more useful than distributed pattern. Hence, in such case the client device 100 could be configured to indicate in the UL indicator set that it prefers a localized PTRS pattern over a distributed PTRS pattern. Alternatively or additionally the network access device 200 may already from the UE capability information derive that the client device 100 would benefit from a localized PTRS without getting such information explicitly from the client device 100. Accordingly the network access device 200 may schedule a localized PTRS pattern instead of a distributed PTRS pattern for the client device 100.

[0068] As already mentioned above, the client device 100 is configured to assist the network access device 200 in the choice of the respective PTRS pattern. That means the client device 100 can for example indicate to the network access device 200 to send a certain particular PTRS pattern. For this, the client device 100 may send a request on a particular PTRS pattern, taking into account radio channel conditions and the estimated PN model. Hence, the client device 100 may dynamically adapt its preference for PTRS patterns. As an example, if the current radio channel conditions and estimated PN coefficients provide evidence that estimation of more PN coefficients could improve the performance, the client device 100 may send a request to the network access device 200 to provide a PTRS pattern with a higher localization burst length than a current one. This may improve the wireless communication performance.

[0069] Consequently, the set of respective PTRS patterns 310...320" from which the network access device 200 can choose can be defined. One parameter that may be used to define this set is the localization burst length as explained in conjunction to Fig. 4. Meaningful values for the burst length parameter can be odd values in the range, for example, from 3 to 13, allowing estimation from 2 to 7 PN coefficients. Another parameter that may be used to define the set of PTRS patterns 310...320" is the set of preferable radio resources such as mentioned resource elements REs that can be used for the localized PTRS pattern. The preferred radio resources could for example, be signaled using an offset from of a PTRS subcarrier in a scheduled bandwidth. Using such an offset avoids resource intense explicit signaling of the preferred radio resources.

[0070] Furthermore, the client device 100 may explicitly request for a certain density of the PTRS pattern 310...320" in frequency and/or time.

[0071 ] The mentioned indicators relating the preference of the PTRS pattern can be conveyed by the client device 100 to the network access device 200, for example via UCI, RRC or MAC-CE.

[0072] According to another embodiment, the indicators comprising the dynamic part of the UL indicator set may be provided implicitly with the help of some predefined rules. For example when the corresponding indicators are chosen in accordance with the radio channel conditions and PN model. Hence, for a certain radio channel condition (e.g. reported by the client device 100 or measured by the network access device 200) and PN model the network access device 200 can be configured to choose a certain PTRS pattern without relying on explicit dynamic information from the client device 100.

[0073] In turn, the network access device 200 may provide the client device 100 with information about the scheduled PTRS pattern using mentioned DL indicator set. The indicators in such DL indicator set may comprise a number of PTRS ports, a bitmap showing the association between PTRS ports and PLLs in the network access device 200 transmission, TX, distributed or localized pattern, localization burst length, or an offset of a PTRS subcarrier in a scheduled bandwidth. Furthermore, also the DL indicator set can be split into a static part (comprising non-changing information related to the network access device 200) and a dynamic part (comprising changing information). The burst length can be included in the static part or in the dynamic part.

[0074] The DL indicator set can be conveyed from the network access device

200 to the client device 100 by explicit signaling, for example via DCI, MAC-CE, and/or RRC.

[0075] Alternatively indicators comprising the dynamic part of the DL indicator set are implicitly obtained by the client device 100, for example, via predetermined rules specified in standard specification. For example, a certain amount, value or table (e.g. an SINR measurement or a PN model parameter available in the client device 100) may implicitly indicate a certain indicator value for the PTRS pattern and its further attributes.

[0076] The embodied flow charts for parameters exchange in DL and UL are represented in FIG. 5 and FIG. 6. An embodied information exchange between the client device 100 UE and the network access device 200 is represented in FIG. 7. The client device 100 of FIG. 1 and the network access device 200 of FIG. 2 may be configured to perform the operations and functions described in the embodiments of FIGs. 5-7. The client device 100 and the network access device 200 are configured to apply the PTRS patterns 310...320" and select the appropriate pattern with parameters when signaling and configuring UL and/or DL.

[0077] FIG. 5 illustrates a flowchart of a method of indicating a PTRS pattern for downlink, DL, according to an embodiment. The embodiment of FIG. 5 illustrates the DL communication from the network access device 200 to the client device 100. In this example operation 501 relates to the static part of the DL information. Operations 502 and 504 relate to the dynamic part of the DL information.

[0078] In operation 500 the DL flow begins. For example, the network access device 200 starts to transmit to the client device 100.

[0079] In operation 501, the client device 100 receives the DL and obtains indicators corresponding to the DL indicator set static part. Said indicators in said static part comprise a number of PTRS ports of the network access device 200. Furthermore, said indicators comprise the network access device 200 RF characteristics, such as a bitmap showing an association between the PTRS ports and PLLs in the network access device 200 TX.

[0080] In operation 502, the client device 100 receives the DL communication further and obtains corresponding to the DL indicator set dynamic part. These may include information indicating whether a distributed or a localized PTRS pattern is scheduled. Furthermore, a PTRS density in frequency dimension may be indicated. Additionally, a PTRS density in time dimension may also be indicated. The static part of the DL indicator set is typically sent with a much a lower frequency than the dynamic part of the DL indicator set. E.g. the static part can be sent once when the client device 100 registers with the network access device 200. The dynamic part may be sent much more frequently or even periodically.

[0081 ] In operation 503 the client device 100 determines based on the received DL indicator set whether the localized PTRS pattern is scheduled. In case the localized PTRS pattern is scheduled, the process proceeds to operation 504, in which the client device 100 obtains localized PTRS pattern information. Such information may include a localized PTRS burst length. Furthermore, radio resources used for the localized PTRS, for example an offset in the scheduled BW, may be indicated. The process proceeds to operation 505. Also, in case the distributed PTRS pattern is scheduled, the process proceeds to operation 505.

[0082] In operation 505, the network access device 200 sends the PTRS pattern which is defined by the indicators of operations 501, 502, 503, and 504. In other words, the network access device 200 transmits the configured PTRS pattern in the DL.

[0083] In operation 506, the client device 100 receives the PTRS pattern. The client device 100 can estimate phase noise, PN. The operation of estimating relates to the used PTRS pattern and to the radio channel conditions. Consequently, the client device 100 can update the PN model.

[0084] In operation 507, the client device 100 decides on a preferable PTRS pattern. For example, based on the channel condition, such as SINR, and the PN model, the client device 100 can decide which PTRS pattern is preferable. Especially the client device 100 can decide if another PTRS pattern is preferred over the currently used one and can accordingly signal a new preferred PTRS pattern as described in conjunction with Fig. 6. The process may terminate at operation 508. It should be noted that the process may be ongoing, for example starting anew, or another process may be continued. It should be mentioned again that operation 501 can be performed with a lower frequency than the remaining operations (e.g. only once when the client device 100 registers to the network access device 200).

[0085] FIG. 6 illustrates a flowchart of a method of indicating a PTRS pattern for

UL according to an embodiment. The embodiment of FIG. 6 illustrates the UL communication from the client device 100 to the network access device 200. Operation 601 may relate to the static part of the UL information. Operations 602 and 604 may relate to the dynamic part of the UL information.

[0086] In operation 600 the UL flow begins. For example, the client device 100 starts to transmit to the network access device 200.

[0087] In operation 601, the client device provides static indicators of the UL indicator set. For example, the client device 100 sends information on whether the client device 100 can benefit from the localized PTRS pattern. Furthermore, the client device 100 may send information about client device RF characteristics, for example, a bitmap showing an association between client device RX antennas and PLLs in the client device RX.

[0088] In operation 602, the client device 100 provides dynamic indicators of the

UL indicator set. For example, the client device 100 sends information on a distributed or a localized PTRS pattern that the client device 100 prefers to receive. Furthermore, the client device 100 may send information on a preferable PTRS density in frequency dimension. The client device 100 may also send information on a preferable PTRS density in time dimension. As with the DL, the static part of the UL indicator set is typically send with a much lower frequency than the dynamic part of the UL indicator set. E.g. the static part can be sent once when the client device 100 registers with the network access device 200. The dynamic part may be sent much more frequently or even periodically.

[0089] In operation 603, the client device 100 determines whether the localized PTRS pattern is preferred by the client device 100. In case the client device 100 prefers the localized PTRS pattern, the process proceeds to operation 604, in which the client device 100 may provide localized PTRS pattern information to the network access device 200. This may include a preferable localized PTRS burst length. Furthermore, a preferable radio resource for the localized PTRS pattern may be indicated. The preferable radio resource can be indicated using for example, an offset in the system BW or an offset when compared to a currently scheduled PTRS pattern It should be mentioned that it may be also possible that the client device 100 simply indicates to the network access device 200 that it prefers localized PRTS patterns without providing further detailed information on the localized PTRS pattern. The preference of the localized PTRS pattern may be indicated in the static part of the UL indicator set (e.g. when the client device 100 always prefers localized PTRS patterns) or in the dynamic part (e.g. when the client device 100 switches between preference of localized and distributed PTRS patterns depending on a current channel condition or PN model).

[0090] The process proceeds to operation 605. Also, in case the client device 100 prefers the distributed PTRS pattern, the process proceeds to operation 605.

[0091 ] In operation 605, the network access device 200 obtains the UL indicator set. The network access device 200 may select the PTRS pattern based on the obtained indicators in the UL indicator set. For example, the network access device 200 receives the indicators of operations 601, 602 and 604. The network access device 200 can now take them into account when selecting the appropriate PTRS pattern for DL transmission.

[0092] The process ends at operation 606. The process may be ongoing, for example starting anew, and operation 606 may not be final, terminating the operations completely.

[0093] .It should be mentioned again that operation 601 can be performed with a lower frequency than the remaining operations (e.g. only once when the client device 100 registers to the network access device 200).

[0094] FIG. 7 illustrates a schematic representation of a signaling diagram of indicating a PTRS pattern between a client device 100 and a network access device 200 according to an embodiment. Arrows in FIG. 7 illustrate the direction of the communication. For example, an arrow to the right represents communication from the client device 100 to the network access device 200. An arrow to the left represents communication from the network access device 200 to the client device 100.

[0095] In operation 700 the client device 100 signals information on whether the client device 100 benefits from a localized PTRS, for example via RRC or UCI to the network access device 200. Operation 700 may partly correspond to operation 601.

[0096] In operation 701 the client device 100 signals client device RF characteristics such as a bitmap showing the association between client device RX antennas and PLLs in client device RX, for example via RRC or UCI. Operation 701 may partly correspond to operation 602. [0097] In operation 703 the network access device 200 signals the number of PTRS ports to the client device 100. Operation 703 may partly correspond to respective parts of operation 501.

[0098] In operation 705 the network access device 200 signals a bitmap showing the association between PTRS ports and PLLs in the network access device 200, for example via RRC, MAC-CE or DCI to the client device 100. Operation 705 may partly correspond to respective parts of operation 501.

[0099] In operation 706 the client device 100 signals either as static or dynamic part information on which PTRS pattern the client device prefers to receive. The preferred PTRS pattern may be a distributed or localized PTRS pattern to the network access device 200. Operation 705 may partly correspond to respective parts of operation 602.

[001 00] In operation 707 the client device 100 signals preferable PTRS density in frequency dimension to the network access device 200. Operation 707 may partly correspond to respective parts of operation 602.

[001 01 ] In operation 708 the client device 100 signals preferable PTRS density in time dimension to the network access device 200. Operation 708 may partly correspond to respective parts of operation 602.

[001 02] In operation 709 the client device 100 signals a preferable localized PTRS burst length to the network access device 200. The burst length may be sent in case the preference of the localized pattern was signaled in operation 706. The burst length may be signaled explicitly via UCI, MAC-CE, RRC, or implicitly as a bias to a fixed table using UCI or RRC or MAC-CE. Operation 709 may partly correspond to respective parts of operation 604.

[001 03] In operation 710 the client device 100 signals preferable radio resources for a localized PTRS pattern to the network access device 200. The radio resources may, for example, be an offset in a scheduled BW. Operation 710 may be signaled and sent in case preference of the localized pattern was signaled in operation 706. The preferable radio resources may be signaled explicitly via UCI or RRC, or implicitly as a bias to a fixed table using UCI or RRC. Operation 710 may partly correspond to respective parts of operation 604. [001 04] In operation 71 1 the network access device 200 signals which PTRS pattern is scheduled to the client device 100. The information signaled in operation 71 1 may indicate that a distributed or a localized PTRS is scheduled by the network access device 200. Operation 71 1 may partly correspond to respective pars of operation 502.

[001 05] In operation 712 the network access device 200 signals a PTRS density in frequency dimension to the client device 100. Operation 713 signals a density in time. Operations 712 and 713 may correspond to respective parts of operation 502.

[001 06] In operation 714 the network access device 200 signals a localized PTRS burst length to the client device 100. The Network access device 200 may send the localized PTS burst length in case the localized pattern was signaled in operation 71 1. The network access device 200 may signal the burst length explicitly via DCI, RRC, or MAC-CE to the client device 100. Operation 714 may correspond to respective parts of operation 504.

[001 07] In operation 715 the network access device 200 signals radio resources that are used for the localized PTRS to the client device 100. The radio resources may be an offset in the scheduled BW. The network access device 200 may send the radio resource in case the localized PTRS pattern was signaled in operation 71 1. The information in operation 715 may be signaled explicitly via DCI or RRC or MAC-CE, or implicitly as a bias to a fixed table using DCI or RRC or MAC-CE.

[001 08] The functionality described herein can be performed, at least in part, by one or more computer program product components such as software components. According to an embodiment, the network access device 200 and/or the client device 100 comprise the processor 101, 201 configured by the program code when executed to execute the embodiments of the operations and functionality described. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field- programmable Gate Arrays (FPGAs), Program-specific Integrated Circuits (ASICs), Program-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs). [001 09] Any range or device value given herein may be extended or altered without losing the effect sought. Also any embodiment may be combined with another embodiment unless explicitly disallowed.

[001 1 0] Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[001 1 1 ] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items. The term 'and/or' may be used to indicate that one or more of the cases it connects may occur. Both, or more, connected cases may occur, or only either one of the connected cases may occur.

[001 1 2] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

[001 1 3] The term 'comprising' is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[001 1 4] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. A client device (100), configured to:

provide an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern to a network access device (200),

wherein the PTRS pattern is a localized PTRS pattern (320,320'320") or a distributed PTRS pattern (310,310', 310"),

when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length (306,306',306"); and

obtain, from the network access device (200), information about a PTRS pattern scheduled for a downlink transmission.

2. The client device of claim 1, wherein the uplink indicator set further comprises a static part and a dynamic part; and

the PTRS burst length associated with the localized PTRS pattern is configured to be indicated using the static part or the dynamic part.

3. The client device of claim 2, wherein the static part of the uplink indicator set further comprises information about at least one of a client device capability and client device radio frequency, RF, characteristics,

wherein the client device capability indicates whether the client device can benefit from an inter carrier interference, ICI, compensation using the localized PTRS pattern.

4. The client device of claim 3, wherein the client device RF characteristics comprise a bitmap indicating an association between receiving antennas of the client device and phase locked-loops, PLLs, of the client device.

5. The client device of any of claims 2-4, wherein the dynamic part of the uplink indicator set further comprises information about whether the client device prefers the localized or the distributed PTRS pattern.

6. The client device of claim 5, wherein the dynamic part of the uplink indicator set further comprises information about preferred radio resources for the localized PTRS, in case the client device prefers the localized PTRS pattern.

7. The client device of claim 6, wherein the preferred radio resources for the localized PTRS pattern are configured to be indicated using an offset of a PTRS subcarrier in a scheduled bandwidth.

8. The client device of any preceding claim, configured to signal the static part or the dynamic part using radio resource control, RRC, medium access control, control element, MAC-CE, or uplink control information, UCI.

9. The client device of any preceding claim, wherein the obtained information about the scheduled PTRS pattern comprises at least one of information about network access device radio frequency, RF, characteristics, and information of whether the localized or the distributed PRTS pattern is scheduled.

10. The client device of claim 9, wherein the client device is further configured to obtain further information about the burst length of the scheduled localized PTRS pattern and radio resources for the scheduled localized PTRS pattern, in case the localized PTRS pattern is scheduled.

1 1. The client device of any preceding claim, wherein the client device is further configured to obtain a downlink indicator set corresponding to the scheduled PTRS pattern, wherein the client device is configured to obtain the dynamic part of the downlink indicator set implicitly using predefined thresholds based on channel characteristics, wherein the channel characteristics include both radio channel conditions and a phase noise model.

12. A network access device (200), configured to: obtain, from a client device (100), an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern, wherein the PTRS pattern is a localized PTRS pattern (320,320',320") or a distributed PTRS pattern (310,310',310"), and when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length (306,306',306");

based on the received uplink indicator set, determine the PTRS pattern;

convey, to the client device (100), a downlink indicator set comprising information about the determined PTRS pattern; and

schedule the determined PTRS pattern.

13. The network access device of claim 12, wherein the downlink indicator set contains a static part and a dynamic part; and

the PTRS burst length associated with the scheduled localized PTRS pattern is configured to be indicated using the static part or the dynamic part.

14. The network access device of claim 13, wherein the static part of the downlink indicator set comprises information about the network access device RF characteristics,

wherein the network access device RF characteristics comprise a number of PTRS ports of the network access device assigned to a particular client device; and/or a bitmap associating the PTRS ports and the PLLs of a network access device.

15. The network access device of any of claims 13 or 14, wherein the dynamic part of the downlink indicator set is configured to indicate whether the localized or the distributed PTRS pattern is scheduled.

16. The network access device of any of claims 13-15, wherein the dynamic part of the downlink indicator set further comprises information about radio resources allocated for the scheduled localized PTRS, in case the localized PTRS pattern is scheduled.

17. The network access device of any of claims 13-16, wherein the network access device is further configured to indicate an offset of a PTRS subcarrier in a scheduled bandwidth.

18. The network access device of any of claims 13-17, configured to signal at least one of the static part and the dynamic part of the downlink indicator set using radio resource control, RRC, medium access control, control element, MAC-CE, or downlink control information, DCI.

19. The network access device of any preceding claim 12-18, wherein the obtained uplink indicator set comprises information about client device radio frequency, RF, characteristics, and information of whether the localized or the distributed PTRS pattern is to be used.

20. The network access device of claim 19, wherein the network access device is further configured to obtain further information about the burst length of the preferred localized PTRS pattern and preferred radio resources for the localized PTRS pattern, in case the localized PTRS pattern is preferred by the client device.

21. The network access device of any preceding claim 12-20, further configured to obtain the dynamic part of the uplink indicator set implicitly using predefined thresholds based on channel characteristics.

22. A method, comprising

providing (601,602,604), to a network access device, an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern,

wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, the at least one indicator indicates at least a PTRS burst length; and obtaining (605), from the network access device, information about the PTRS pattern scheduled for a downlink transmission.

23. A method, comprising:

obtaining (501,502,504), from a client device, an uplink indicator set comprising at least one indicator related to a phase tracking reference signal, PTRS, pattern, wherein the PTRS pattern is a localized PTRS pattern or a distributed PTRS pattern, and when the PTRS pattern is the localized PTRS pattern, at least one indicator indicates a PTRS burst length;

based on the received uplink indicator set, determining (503) the PTRS pattern; conveying (505) a downlink indicator set comprising information about the determined PTRS pattern; and

scheduling (507) the determined PTRS pattern.

24. A computer program comprising program code configured to perform a method according to claim 22 or 23 when the computer program is executed on a computer.