WO2018206113A1

WO2018206113A1 - Indication of beams for wireless communication

Info

Publication number: WO2018206113A1
Application number: PCT/EP2017/061377
Authority: WO
Inventors: Petteri KELA; Kari Juhani LEPPANEN
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-05-11
Filing date: 2017-05-11
Publication date: 2018-11-15
Anticipated expiration: 2019-11-11

Abstract

It is an object to provide an indication of beams for wireless communication. According to a first aspect, a user equipment comprises: a receiver configured to receive beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code in a geographical area; a processor configured to: based on the BRSs, calculate receive filters for each BRS so as to establish a receive filter for each spatial beam; and determine spatial beam indexes based on the time, frequency or code of the BRSs configured for the user equipment. Flexible spatial beam indication may be provided from a network to the UE with reduced or minimal signaling. The UE can select adequate receive filters for receiving or transmitting subsequent transmissions. A network device, a method and a computer program are described.

Description

INDICATION OF BEAMS FOR WIRELESS COMMUNICATION

TECHNICAL FIELD

[0001 ] The present application relates to the field of wireless radio communications, and more particularly to indication of spatial beams.

BACKGROUND

[0002] In advanced wireless radio communications, such as the fifth generation, 5G, system, one central base station, gNB, may be controlling several transmission or reception points, TRPs. Each TRP may form several spatial beams which are used for transmitting or receiving data to or from several user equipments, UEs, simultaneously using a certain time, frequency and code.

[0003] Usually it has been assumed that each TRP has n pieces of static beams, from which the best combination is selected for the serving UEs. This may require knowledge about the best static beams for each UE and mobility handling between beams and TRPs. In order to synchronize the beams used between the network and the UE, group based beam management is being proposed. However, it has not been disclosed how transmission, Tx, or reception, Rx, beam selection for control and shared channels could be operated on a transmission time interval, TTI, basis allowing dynamic scheduling also in a beam space.

[0004] In both downlink, DL, and uplink, UL, based beam selection solutions, optimal scheduling and precoding decisions can be made in the network. Hence, it might happen that the beam that had the strongest signal for a specific UE is not the one the gNB or TRP has chosen for transmitting or receiving data stream for the UE. In such a situation, a multi-antenna UE may optimize its antenna weights for the reception or transmission using a wrong assumption about the serving beam.

SUMMARY

[0005] 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.

[0006] It is an object to provide an indication of beams for wireless communication. 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.

[0007] According to a first aspect, a user equipment comprises: a receiver configured to receive beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code in a geographical area; a processor configured to: based on the BRSs, calculate receive filters for each BRS so as to establish a receive filter for each spatial beam; and determine spatial beam indexes based on the time, frequency or code of the BRSs configured for the user equipment. A flexible spatial beam indication may be provided from a network to the UE with reduced or minimal signaling. The UE can select adequate receive filters for receiving or transmitting subsequent transmissions.

[0008] In a further implementation form of the user equipment aspect, the processor is configured to determine the spatial beam indexes from an order of the time, frequency or code of the BRSs. The user equipment may determine the spatial beam indexes from a certain order of the time, frequency or code. The order may be detected and indexing is based on the detected order. [0009] In a further implementation form of the user equipment aspect, the processor is configured to determine the spatial beam indexes from instances of the time, frequency or code of the BRSs occurring with periodicity. Certain instances occurring with periodicity may be determined for indexing.

[001 0] In a further implementation form of the user equipment aspect, the processor is configured to determine the spatial beam indexes from a mapping table. The mapping table may map indexes to a certain time, frequency or code. The mapping table may be provided by predetermined specifications, etc.

[001 1 ] In a further implementation form of the user equipment aspect, the spatial beam indexes are mapped to predetermined times, frequencies or codes of the BRSs. A certain predetermined piece of time, frequency or code sequence may be agreed to be an index or a pointer to a function in order to determine the index.

[001 2] In a further implementation form of the user equipment aspect, the processor is configured to determine the spatial beam indexes based on modulo calculation so that a certain time, frequency or code of the BRSs establishes a first one of the spatial beam indexes, and another certain time, frequency or code of the BRSs establishes a second one of the spatial beam indexes. The UE may use modulo calculation for determining the indexes in a simple way.

[001 3] In a further implementation form of the user equipment aspect, the receive filters comprise antenna weights for multiple antennas of the user equipment, and the processor is configured to calculate the antenna weights for each spatial beam. The user equipment may determine appropriate antenna filters so that the corresponding receive beams are determined appropriately.

[001 4] In a further implementation form of the user equipment aspect, the receiver is further configured to receive at least one of the spatial beam indexes within downlink control information, DCI; and the processor is further configured to determine the receive filters based on the at least one of the spatial beam indexes. The spatial beam, which is to be used in subsequent communication with the network, may be received in the DCI. The indexing remains synchronized between the network and the UE, and the used spatial beam may be determined accordingly.

[001 5] In a further implementation form of the user equipment aspect, the DCI further includes at least one of downlink or uplink allocation for the spatial beams. The used spatial beam may be given in the DL or UL allocation. The used spatial beam may be communicated by the appropriate spatial beam index from the network to the UE.

[001 6] In a further implementation form of the user equipment aspect, the at least one of the spatial beam indexes refers to a transmission beam used by a serving transmission reception point, TRP, for sending downlink transmission; or the at least one of the spatial beam indexes refers to a reception beam used by a serving transmission reception point, TRP, for receiving uplink transmission. Both DL and UL can be covered.

[001 7] In a further implementation form of the user equipment aspect, the receiver is further configured to receive an index change command indicating a change in the spatial beam indexes. Generally any time, even without the DCI and allocation, the spatial beam index may be given by the command.

[001 8] In a further implementation form of the user equipment aspect, the indexing change command is included in downlink control information, DCI. Conveniently, the command may be included in the DCI.

[001 9] In a further implementation form of the user equipment aspect, the indexing change command is included in a medium access control, MAC, control element, CE. The MAC CE may also be used for conveying the indexing change command.

[0020] According to a second aspect, a network device for wireless radio communication comprises: a transmitter configured to transmit beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code to a geographical area; a processor configured to: determine spatial beam indexes at least for one user equipment based on an order of the time, frequency or code of the BRS assigned to be measured by the user equipment. The network device transmits the BRSs having a certain indexing. The UE receiving the BRSs determines the indexing based on the same principle. Consequently, the network and the user equipment remain synchronized with respect to the indexing without a need for sending any specific message.

[0021 ] According to a third aspect, a method comprises: receiving beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code in a geographical area; calculating receive filters for each BRS so as to establish a receive filter for each spatial beam; and determining spatial beam indexes based on the time, frequency or code of the BRSs configured for the user equipment.

[0022] According to a fourth aspect, a computer program is provided, comprising program code configured to perform a method according to the third aspect when the computer program is executed on a computer.

[0023] 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

[0024] The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein:

[0025] FIG. 1 illustrates a schematic representation of a block diagram of a UE configured for determining spatial beam indexes based on a resource element of a beam specific reference signal according to an embodiment;

[0026] FIG. 2 illustrates a schematic representation of a block diagram of a network device configured to determine spatial beam indexes for the UE according to an embodiment;

[0027] FIG. 3 illustrates a schematic representation of a system comprising UEs, TRPs, and gNB;

[0028] FIG. 4 illustrates a schematic representation of TRPs and a UE configured to calculate receive filters for each spatial beam based on spatial beam indexing, according to an embodiment;

[0029] FIG. 5 illustrates a schematic representation of beam specific reference signal, BRS, resource elements that can be used for determining spatial beam indexes, according to an embodiment;

[0030] FIG. 6 illustrates a schematic representation of a signaling diagram between UE and TRP for determining spatial beam indexes based on resource elements of BRSs, and further for using one of the indexes for UE spatial beam allocation, according to an embodiment;

[0031 ] FIG. 7 illustrates a schematic representation of a signaling diagram between UE and network in order to determine spatial beam indexes based on resource elements of BRSs, according to an embodiment;

[0032] FIG. 8 illustrates a schematic representation of a signaling diagram between UE and network in order to send one of spatial beam indexes within downlink or uplink allocation, according to an embodiment;

[0033] FIG. 9 illustrates a schematic representation of a signaling diagram between UE and TRP in order to send one of spatial beam indexes within a beam change command, according to an embodiment;

[0034] FIG. 10 illustrates an example of downlink control information, DCI, comprising a spatial beam index, according to an embodiment;

[0035] FIG. 11 illustrates an example of a beam change command comprising a spatial beam index, according to an embodiment; [0036] FIG. 12 illustrates an example of a beam change command incorporated in medium access control, MAC, comprising a spatial beam index, according to an embodiment;

[0037] FIG. 13 illustrates a flowchart showing a method of determining spatial beam indexes, according to an embodiment; and

[0038] FIG. 14 illustrates a flowchart showing a method of configuring spatial beam indexes, 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 ] According to an embodiment, a user equipment, UE, can obtain spatial beam indexes, for example from an order of physical resources used for sending beam reference signals, BRSs. The UE receives the BRSs. Each BRS corresponds to a spatial beam that can transmit data using a certain time, frequency and code in a geographical area. The UE measures the BRSs according to a previously given configuration. Based on the measured BRSs, the UE calculates receive filters for each BRS so as to establish a receive filter for each spatial beam. The receive filter may be alternatively referred to as a receive beam, Rx beam. Furthermore, the UE determines spatial beam indexes based on the physical resources of the BRSs that are configured for the UE. The UE is able to determine the indexing for the spatial beams based on the physical resources of the BRSs. Consequently, the UE can be synchronized with a network device transmitting the spatial beams to the UE with respect to the indexing of the spatial beams. The BRSs may be used for determining the indexing. [0042] An embodiment allows flexible spatial beam indication from a network to the UE with reduced signaling. The UE can choose adequate receive filters, such as UE antenna weights or the best UE beam for receiving or transmitting subsequent transmissions.

[0043] The physical resources of the BRSs, which are used for determining the spatial beam indexes, may be the time, frequency or code of the BRSs. The physical resources of the BRS may be alternatively referred to as a BRS resource element. According to an embodiment, the physical resources used for indexing can, for example, be subframe numbers, OFDM symbol numbers, subcarrier numbers, resource element numbers, etc.

[0044] According to an embodiment, a network device, such as a

TRP or gNB, can transmit BRSs so that each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code to a geographical area. Furthermore, the network device determines spatial beam indexes at least for one UE based on an order of the physical resources of the BRS. The physical resources are assigned to be measured by the UE.

[0045] The network device can indicate to the UE which downlink reference signal resources (e.g. the physical resources of the BRSs) the UE shall use for selecting optimal spatial beams and calculating the receive filter such as the antenna weights. The UE can monitor beam BRSs and preselect the optimal beam for each TRP beam in advance. The UE determines indexing for the spatial beams. Then, when the network indicates which spatial beam it shall use, the UE can select adequate receive filters that have optimal properties for the spatial beams that the network has selected for serving the UE. Because indexing is determined based on the BRSs, and the network is configured to use the same indexing for BRS transmission, spatial beam indexing can be synchronized between the UE and the network without any specific synchronization messaging. [0046] In 5G, it should be possible to indicate, for example in downlink control information, DCI, which spatial beam(s) is(are) selected by the network for serving the UE. This information can be given efficiently with a spatial beam index. Because the total number of separate beams can be high in a 5G network, the index can show which physical resource of the BRS the UE may measure in order to select spatial beams and receive filters, for example to select spatial beams and dynamically determine antenna weights. Consequently, the UE can determine which BRS to use for receive filter calculation or which static beams to select based on the index provided by the network.

[0047] Indexing can be based on mapping tables, certain instances of the physical resources of the BRSs, periodicity of the physical resources of the BRSs, etc.

[0048] The spatial beam index can be given together with each DCI including DL or UL allocation. In this case the UE can select the appropriate spatial beam and the corresponding receive filter for the spatial beam with the index. Alternatively, the spatial beam index can be given with a separate beam indicator command, in which case the given beam indicator is used until changed by the command.

[0049] FIGs 1 and 2 schematically show a UE 100, such as a wireless device, in a wireless communication system. The UE 100 comprises a processor 101, a receiver 102 and a transmitter 103. The wireless communication system also comprises a network device 200, such as a TRP or gNB, which may also comprise a processor 202, a receiver 203 and a transmitter 204.

[0050] The UE 100 may be any of a User Equipment (UE) in Long

Term Evolution (LTE), 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 100 may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs 100 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 100 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).

[0051 ] The network device 200 may be a transmission or reception point, TRP or a 5G base station, gNB. The network 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 802.11 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).

[0052] FIG. 3 illustrates a schematic representation of a wireless system comprising UEs 100_1 - 100_5, TRPs 201_1 - 201_3, and a gNB 200. The TRP 200 can from several spatial beams used for transmitting or receiving data to or from several UEs 100 simultaneously using time, frequency and codes. The arrows in FIG. 3 represent transmissions or receptions of spatial beams between the UE 100 and the TRP 200.

[0053] FIG. 4 illustrates a schematic representation of TRPs

201_1,201_2 and a UE 100 configured to determine receive filters 110 for each spatial beam 210 based on spatial beam indexing 111 according to an embodiment. The UE 100 selects a receive filter(s) 110 for each spatial beam 210. In the embodiment of FIG. 4, the UE 100 has three different receive filters 110_1 - 110_3. Receive filter 110_1 is selected for spatial beam 210_1. Receive filter 110_2 is selected for spatial beams 210_2 and 210_3. Receive filter 110_3 is selected from spatial beams 210_4, 210_5, and 210_6. Spatial beam indexes 1 11 may be conveniently utilized for selecting appropriate receive filters 110 for the spatial beams 210. As discussed above, the receive filter may be alternatively referred to as Rx beam.

[0054] Spatial beams 210, which are pointing towards the same geographical area, are likely to use separate physical time, frequency or code resources for BRSs. For example in FIG. 4 there are six spatial beams 210_1-210_6 using different time, frequency or code resources for BRSs. It should be noted that the same reference signal resources may then be reused by other spatial beams pointing towards different geographical areas. The UE 100 can reliably detect spatial beams 210 that can be separated in time and/or frequency and/or code. Hence, these six illustrated spatial beams 210 could belong to one beam group. The physical resources used for the BRSs of the spatial beams 210 for indexing can be associated to certain physical resources: for example, to subframe numbers, OFDM symbol numbers within a subframe, subcarrier numbers and/or resource element numbers. Modulo calculation can be used in the UE 100 for determining a spatial beam index 11 1 from the physical resource element used for BRSs and vice versa. Therefore, the network device 200 can indicate the used spatial beams 210 with indexing 111 for UEs 100, and the UE 100 may determine these indexes 111 from the physical resources of the BRSs.

[0055] The index 11 1 can be given for a control and shared channel, which increases the degrees of freedom in multi-TRP 201 or multi-beam 210 scheduling.

[0056] FIG. 5 illustrates a schematic representation of beam specific reference signal, BRS, resource elements 113 that can be used for determining spatial beam indexes 111 according to an embodiment. Physical resources 113 are shown in FIG. 5 with respect to time t denoted by the x-axis and frequency f denoted by the y-axis. A first configured BRS resource element 113_1 is shown. A code of the first configured BRS resource element 113_1 can be obtained with a root index j. A second configured BRS resource element 113_2 is shown. A code of the second configured BRS resource element 113_2 can be obtained with a root index j+k.

[0057] Indexing of spatial beams 210 is based on a different resource element index and/or code, for example the code root index, which is used for different BRSs such as the 1st and 2nd BRS shown. The resource element 113 may be a certain time, frequency or code instance within the utilized time and frequency grid. Hence, unambiguous beam indexing 111 should be obtainable when time, frequency and/or code resources of BRSs are known by both of the network device 200,201 and the UE 100.

[0058] Indexing may be based on specified rules on how to determine the used resources from the provided index. The UE 100 can be configured to measure certain instances of time, frequency and/or code of the BRSs reoccurring with some periodicity. For example, the index may refer to a reference signal sent on the nth time/frequency/code resource. If n BRSs reoccur with a periodicity of p, then index 1 refers to the first reference signal, for example in time, frequency or code domain(s), within the period and n refers to the last reference signal within the period, respectively. Furthermore, if index n is given in DCI, then n can relate, for example, to certain subframe, subcarrier, OFDM symbol or resource element numbers.

[0059] According to another embodiment, indexing can be based, for example, on mapping tables. The mapping tables may, for example, be provided in the 5G specification. A mapping table can map spatial beam indexes 111 to certain time, frequency and/or code resources 113.

[0060] FIG. 6 illustrates a schematic representation of a signaling diagram between a UE 100 and a TRP 201 for determining spatial beam indexes 111 based on resource elements 113 of BRSs, and further for allocating one 112 of the indexes to the UE, according to an embodiment. It should be noted that also multiple indexes may be allocated, although allocation of one 112 of the indexes is described.

[0061 ] The TRP 201 transmits BRSs to the UE 100 by signals 303.

This may be based on a general beam reporting configuration. Furthermore, the TRP 201 may be configured to index a physical resource 113 of BRSs with spatial beam indexes 111. The UE 100 receives the signals 303. The UE 100 can determine the indexes 111 based on the physical resources 113 of the BRSs. For example, a sequence 4, 5, 6 of the physical resource 113 is repeated in the signal 303. The UE 100 may determine receive filters 110. The UE 100 can also determine the spatial beam indexes 111 1, 2, 3 for the receive filters 110 as illustrated by bold arrows in FIG. 6. The UE 100 obtains the indexing from the physical resources 113 of the BRSs. The UE 100 may determine that index 1 corresponds to spatial beam 210_1, index 2 corresponds to another spatial beam 210_2 and index 3 corresponds to another spatial beam 210_3. The TRP 201 transmits UL or DL allocation signaling 306. An index 112 having a value 2 has been incorporated into the allocation signaling 306. The allocation also contains the spatial beam 210 the network allocates to the UE 100 for use. The UE 100 receives the allocation and also determines the index in operation 112. The UE 100 can now determine appropriate receive filters 110 based on the index 112, which may be optimized based on the BRSs. The UE 100 and the network are also synchronized with respect to the indexing of the spatial beams 210. This may be achieved without specific synchronization messaging.

[0062] It should be noted that also multiple indexes 112 may be allocated, although allocation of one 112 of the indexes is described. Multiple indexes 112 may be incorporated within the allocation signaling 306. UE 100 may now determine appropriate receive filters 110 based on the multiple indexes 112.

[0063] FIG. 7 illustrates a schematic representation of a signaling diagram between a UE 100 and a network device 200,201 in order to determine spatial beam indexes 111 based on resource elements 113 of BRSs according to an embodiment.

[0064] The network provides the UE 100 with a spatial beam reporting configuration 300. The configuration 300 may be a general procedure for setting up the spatial beam based wireless communication. The signalling 300 may relate to several beams and includes content 302. The content 302 of the configuration 300 may include a BRS measurement start time and/or frequency and/or code. The content 302 may also include an amount of the measured time and/or frequency and/or code instances. Furthermore, the content 302 of the configuration 300 may include periodicity of the measured BRS.

[0065] The UE 100 measures BRSs according to the configuration

300 in operation 301. The UE 100 measures first BRSs 303_1 to the nth BRS 303_n, wherein the number of BRS is based on the configuration 300. The BRSs 303 contain the physical resources 113.

[0066] The UE 100 determines the spatial beam indexes 111 based on the physical resource 113 of the BRSs in operation 304. This may be performed according to the embodiments as described above.

[0067] FIG. 8 illustrates a schematic representation of a signaling diagram between a UE 100 and a network device 200,201 in order to send one of spatial beam indexes within DL or UL allocation 306 according to an embodiment. According to an embodiment, multiple spatial beam indexes may be incorporated within the DL or UL allocation.

[0068] The allocation 306 comprises content 305 which has DL or UL allocation. This may allocate the used spatial beam from the network 200,201 to the UE 100. Furthermore, the allocation content 305 includes a spatial beam index, which refers to the beam that is used in the upcoming transmission. The spatial beam index refers to the allocated spatial beam, for example as illustrated by reference 112 in FIG. 6. The DL or UL allocation 306 is given with downlink control information, DCI, on a DL control channel. The UE 100 determines the spatial beam 210 that the index 112 in DCI is referring to. This may be based on the indexing as performed in operation 304. Based on the determined index 112, the UE 100 prepares a receive filter 110.

[0069] When the UE 100 is active, it monitors a control channel. Within the control channel, dedicated UL or DL allocations are given to UEs 100 with the DCI. The DCI includes, for example, information about precoding information, hybrid automatic retransmission request, HARQ, process, modulation/coding, time and/or frequency resources used for transmission. Additionally, it should include a beam index 112, which can be used for calculating the receive filter 110, for example for selecting adequate antenna weights at the UE 100 or a UE 100 Rx beam for the reception.

[0070] FIG. 9 illustrates a schematic representation of a signaling diagram between a UE 100 and the network device 200, 201 in order to send one of spatial beam indexes 111 within a beam change command according to an embodiment. The beam change command 308 can be signaled from the network 200, 201 to the UE 100. The content 309 of the beam change command may include a new index for the changed spatial beam 210. The index may be given in the DCI or within a medium access control, MAC, control element, CE. The beam index change command can be specified for UL or DL. This may allow the network to use different beams for UL and DL. Upon reception of the beam index change command 308, the UE 100 considers the indicated spatial beam, which is indicated by the new index, for further transmission and reception in operation 310.

[0071 ] Instead of embedding the spatial beam index 112 within DCI including DL or UL allocations, separate DCI can be introduced for indicating a new beam index for the UE 100. This may be indicated to a control and/or shared channel. According to another embodiment, a MAC control element, CE, may be used for sending the new spatial beam index to the UE 100. Then, with the specified MAC CE, a new spatial beam configuration for control and/or shared channels can be indicated to the MAC layer directly.

[0072] FIG. 10 illustrates an example of downlink control information, DCI, 400 comprising a spatial beam index 112 according to an embodiment. FIG. 10 illustrates an example of DCI 400 including the spatial beam index 112, where the bit length depends on the maximum beams. The DCI 400 is illustrated with data allocation including the beam index 112. The bit field length of the index 112 depends on the amount of BRSs assigned for a UE 100 to measure. For example, if the UE 100 is assigned to measure n BRSs, then the spatial beam index field 112 can be packed within [log2(n)J + 1 bits.

[0073] FIG. 11 illustrates an example of a beam change command

401 comprising a spatial beam index 112_1 according to an embodiment. In case of the beam change command being incorporated into DCI, the new beam index 112_1 can be simply indicated to the UE 100.

[0074] FIG. 12 illustrates an example of a beam change command

402 incorporated in medium access control, MAC, comprising a spatial beam index 112_2 according to an embodiment. A special bit string in the logical channel id, LCID, field of the MAC Header can also be used for indicating the change command of the spatial beam index 112_2, which is to be included in the MAC control element structure.

[0075] FIG. 13 illustrates a flowchart showing a method of determining spatial beam indexes, according to an embodiment. In FIG. 13, spatial beam indexes are determined from the order of the physical resources, which are used for sending the beam reference signals, BRSs. Physical resources, which are used for indexing can be, for example, subframe numbers, PFDM symbol numbers, subcarrier numbers, resource element numbers, etc.

[0076] In operation 500, BRSs are received. The BRSs may be received based on the BRS configuration. They may be received at the UE. BRSs comprise physical resources, such as time and/or frequency and/or code. The UE can detect these physical resources from the BRSs. Furthermore, the UE may detect the order of the physical resources, or a certain instance or instances, periodicity, or predetermined physical resources, etc.

[0077] In operation 510, receive filters are determined. The receive filters may be determined based on the BRSs. For example, each BRS has a corresponding receive filter at the UE so determined. The receive filters may be based on antenna weights for multiple antennas of the UE 100. Alternatively, the receive filters may be referred to as spatial reception beams. The receive filter is determined so that it is optimized with respect to the spatial transmission beam of the BRS.

[0078] In operation 520, spatial beam indexes are determined. The detected physical resources of the BRSs are indexed. Each physical resource meeting the indexing criteria is indexed at the UE. Thereby, spatial beams become indexed at the UE, because the indexed physical resource corresponds to the respective spatial beam. Indexing may be based on a monotonic function or another predetermined indexing system.

[0079] Optionally in operation 530, the spatial beam indexes are sent within DCI including DL or UL allocation. In case of the DL allocation, a beam index refers to a spatial transmission beam, which is used by serving TRP(s) for sending a corresponding downlink shared channel data transmission. In case of the UL allocation, the beam index refers to the reception, Rx, beam used by serving TRP(s) for receiving a corresponding uplink shared channel data transmission.

[0080] Optionally in operation 540, a spatial beam index change command is sent.

[0081 ] The spatial beam index change command may be sent within

DCI that is dedicated for indicating transmission and/or reception beam changes at TRP(s). Upon receiving such DCI, the UE will change the used transmission and/or reception beams (the receive filters) and use them until change is triggered by a new change command or other procedure. [0082] The spatial beam index change command may alternatively be sent within a MAC CE. Upon receiving a MAC CE with the beam change command, the UE may: MAC instruct a physical layer to change transmission or reception beams; MAC perform certain procedures, for example flushing HARQ processes, stopping or resetting a certain subset of MAC timers.

[0083] Operation 540 may follow operation 530, or be directly or otherwise obtained after operation 520 without the necessity of operation 530.

[0084] FIG. 14 illustrates a flowchart showing a method of configuring spatial beam indexes, according to an embodiment. In operation 550, the spatial beam indexes are determined at the transmission of the BRSs. For example, the network device determines that certain physical resources of the BRS, which are to be provided to a UE, are indexed. The indexing process uses a similar indexing determination so that the indexing remains the same at the network device and at the UE. In operation 560, the network device may transmit BRSs. The BRSs are transmitted to the UE, and they contain the physical resources to be indexed at the UE, respectively.

[0085] 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 device 100 and/or another device 200 comprise a processor 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091 ] 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 user equipment (100), comprising:

a receiver (102) configured to receive beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam (210) configured to transmit data using a certain time, frequency and code in a geographical area;

a processor (101) configured to:

based on the BRSs, calculate receive filters (110) for each BRS so as to establish a receive filter for each spatial beam; and

determine spatial beam indexes (111) based on the time, frequency or code (113) of the BRSs configured for the user equipment.

2. The user equipment of claim 1, wherein the processor is configured to determine the spatial beam indexes from an order of the time, frequency or code of the BRSs.

3. The user equipment of any preceding claim, wherein the processor is configured to determine the spatial beam indexes from instances of the time, frequency or code of the BRSs occurring with periodicity.

4. The user equipment of any preceding claim, wherein the processor is configured to determine the spatial beam indexes from a mapping table.

5. The user equipment of claim 4, wherein the spatial beam indexes are mapped to predetermined times, frequencies or codes of the BRSs.

6. The user equipment of any preceding claim, wherein the processor is configured to determine the spatial beam indexes based on modulo calculation so that a certain time, frequency or code (113_1) of the BRSs establishes a first one of the spatial beam indexes, and another certain time, frequency or code (113_2) of the BRSs establishes a second one of the spatial beam indexes.

7. The user equipment of any preceding claim, wherein the receive filters comprise antenna weights for multiple antennas of the user equipment, and the processor is configured to calculate the antenna weights for each spatial beam.

8. The user equipment of any preceding claim, wherein the receiver is further configured to receive at least one (112) of the spatial beam indexes within downlink control information, DCI; and

the processer is further configured to determine the receive filters based on the at least one of the spatial beam indexes.

9. The user equipment of claim 8, wherein the DCI further includes at least one of downlink or uplink allocation for the spatial beams.

10. The user equipment of claim 9, wherein the at least one of the spatial beam indexes refers to a transmission beam used by a serving transmission reception point, TRP, (201) for sending downlink transmission; or

wherein the at least one of the spatial beam indexes refers to a reception beam used by a serving transmission reception point, TRP, (201) for receiving uplink transmission.

11. The user equipment of any preceding claim, wherein the receiver is further configured to receive an index change command indicating a change in the spatial beam indexes.

12. The user equipment of claim 11, wherein the indexing change command is included in downlink control information, DCI.

13. The user equipment of claim 11, wherein the indexing change command is included in a medium access control, MAC, control element, CE.

14. A network device (200,201) for wireless radio communication, comprising:

a transmitter (204) configured to transmit beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam (210) configured to transmit data using a certain time, frequency and code to a geographical area;

a processor (202) configured to:

determine spatial beam indexes (111) at least for one user equipment (100) based on an order of the time, frequency or code (113) of the BRS assigned to be measured by the user equipment.

15. A method, comprising:

receiving (500) beam specific reference signals, BRSs, wherein each BRS corresponds to a spatial beam configured to transmit data using a certain time, frequency and code in a geographical area;

calculating (510) receive filters for each BRS so as to establish a receive filter for each spatial beam; and

determining (520) spatial beam indexes based on the time, frequency or code of the BRSs configured for the user equipment.

16. A computer program comprising program code configured to perform a method according to claim 15 when the computer program is executed on a computer.