METHOD FOR MAPPING ODD NUMBER OF UL SRS ANTENNA PORTS CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of FI application No. 20245525, filed April 26, 2024. The content of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD
[0002] Various example embodiments generally relate to the field of wireless communication. Some example embodiments relate to mapping odd number of uplink (UL) sounding reference signal (SRS) antenna ports. BACKGROUND
[0003] To address uplink and/or downlink coverage issue for new 6G frequency bands (e.g., 6.425- 7.125 GHz and 7-24 GHz), a use of larger antenna arrays, e.g., compared to 5G, with increased number of antennas elements and ports at transmission and reception side are required. The use of large antenna arrays can enable enhanced coverage and spectrum efficiency in both uplink and downlink.
[0004] Currently, new radio (NR) can support up to 24 antenna ports for demodulation reference signal (DMRS) and up to 8 antenna ports for UL SRS resource with different usages, i.e. codebook and antenna-
switching, which may prevent efficient utilization of larger antenna arrays for coverage and spectral efficient enhancement purposes at a user equipment. 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] Example embodiments of the present disclosure enable a UE (user equipment) to determine SRS antenna port mapping for UL SRS resource configured with odd-number of antenna ports. Further
example embodiments are provided in the dependent claims, the description, and the drawings. [0007] According to a first aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one
processor, cause the apparatus at least to: obtain information related to mapping of an odd number of sounding reference signal, SRS, antenna ports to one or more frequency resource elements of an SRS resource; and transmit the sounding reference signal resource based on the obtained information.
[0008] According to a second aspect, a method is disclosed. The method may comprise: obtaining information related to mapping of an odd number of sounding reference signal, SRS, antenna ports to one or more frequency resource elements of an SRS resource; and transmitting the sounding reference signal resource based on the obtained information.
[0009] According to a third aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one
processor, cause the apparatus at least to: obtain resource specific information related to a resource element associated with a highest number of sounding reference signal, SRS, antenna ports among an odd number of SRS antenna ports configured for an SRS resource; and transmit the sounding reference signal resource based on the obtained information.
[0010] According to a fourth aspect, a method is disclosed. The method may comprise: obtaining resource specific information related to a resource element associated with a highest number of sounding reference signal, SRS, antenna ports among an odd number of SRS antenna ports configured for an SRS resource; and transmitting the sounding reference signal resource based on the obtained information.
[0011] According to a fifth aspect, an apparatus is disclosed. The apparatus may comprise means for performing the method according to the second or the fourth aspect, or any example embodiment(s) thereof, as provided in the description and/or the claims. [0012] According to a sixth aspect, a computer program, a computer program product, or a (non- transitory) computer-readable medium is disclosed. The computer program, computer program product, or (non-transitory) computer-readable medium may comprise instructions, which when executed by an
apparatus, cause the apparatus at least to perform the method according to the second or the fourth aspect, or any example embodiment(s) thereof, as provided in the description and/or the claims. [0013] Example embodiments of the present disclosure can thus provide apparatuses, methods, computer programs, computer program products, or computer readable media for improving various aspects of antenna port mapping. Any example embodiment may be combined with one or more other example embodiments. These and other aspects of the present disclosure will be apparent from the
example embodiment(s) described below. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.
DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:
[0015] FIG.1 illustrates an example of a communication network; [0016] FIG. 2 illustrates an example of an apparatus configured to practice one or more example embodiments;
[0017] FIG.3 illustrates an example of UL SRS resource configuration with three SRS antenna ports for codebook and antenna switching usages;
[0018] FIG.4 illustrates another example of UL SRS resource configuration with three SRS antenna ports for codebook and antenna switching usages;
[0019] FIG.5 illustrates an example of UL SRS resource configuration with five SRS antenna ports for codebook and antenna switching usages;
[0020] FIG. 6 illustrates another example of UL SRS resource configuration with five SRS antenna ports for codebook and antenna switching usages;
[0021] FIG. 7 illustrates an example of a method for mapping an odd number of UL SRS antenna ports; and
[0022] FIG.8 illustrates another example of a method for mapping an odd number of UL SRS antenna ports.
[0023] Like references are used to designate like parts in the accompanying drawings. DETAILED DESCRIPTION
[0024] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.
[0025] Increased peak data rate for UL could play a significant role in short-range applications such as home entertainment, video surveillance/monitoring in industrial, healthcare and/or safety applications, integrated access and backhaul (IAB), XR (Extended Reality), and other applications where power/form- factor/cost of devices are not as stringent as in traditional handheld devices.
[0026] Larger antenna arrays, in terms of physical antenna elements and logical antenna ports compared to 5G, can be used in 6G to enable enhanced uplink coverage and spectral efficiency with new
and existing frequency bands. New radio (NR) provides support for even number of UL SRS antenna ports (up to 8 antenna ports). However, it is targeted to provide support also for odd number (e.g., 3TX, three transmission) antenna ports for UL SRS with non-coherent codebooks. Hence, there is a need for a method for a UE to determine antenna port mapping and association with cyclic-shift values as well as frequency resource elements of certain SRS comb-type with antenna ports being phase incoherence with each other.
[0027] To enable robust and reliable UL CSI (channel state information) acquisition at an access node (e.g., gNB) for scheduled/configured multi-antenna PUSCH (physical uplink shared channel) transmission with phase and/or amplitude incoherence between antenna ports, it is important that the network can estimate UL CSI by using UL SRS antenna ports reliably independent of the UE implementation specific phase and/or amplitude incoherence between different UE TX (transmission) antenna ports. UL SRS antenna ports may refer to antenna ports for transmission of UL SRS.
[0028] An objective is to provide an antenna port mapping method for odd number of UL SRS antenna ports with phase and/amplitude non-coherency, for example, for NR and 6G usages.
[0029] According to an example embodiment, antenna port mapping method between cyclic-shift offset values, antenna ports and/or frequency domain resources for a single UL SRS resource with odd number (e.g.3, 5 or higher) of TX antenna ports with phase and/or amplitude non-coherency/partially- coherency/full-coherency for different comb-types is provided. The method may comprise obtaining, by an apparatus for a terminal device, information related to a resource element associated with a highest
amount of UL SRS antenna ports among an odd number of TX antenna ports, and transmitting an SRS using the information.
[0030] FIG.1 illustrates an example of a communication network. Communication network 100 may comprise one or more access nodes, such as access node 104. Access node(s) may be part of a radio access network (RAN) configured to enable a device, represented throughout the description by UE 102, to access communication services provided by core network. In connection with communication network
100, access node(s) 104 and core network may be collectively referred to as the ‘network’. UE 102 may comprise a user device, a terminal apparatus, a terminal device, a mobile device, or the like. UE 102 may be configured to communicate with access node(s) 104 over a radio interface, which may be also referred to as an air interface. Access nodes 104 may be also referred to as network devices. A terminal device may refer any device capable of sending and/or receiving information over a communications channel.
[0031] The radio interface may be configured for example based on the 5G NR (New Radio) standard defined by the 3
rd Generation Partnership Project (3GPP), or any future standard or technology (e.g.,
6G). Access node 104 may comprise, for example, a 5
th generation access node (gNB). Transmission by an access node to UE 102 may be called downlink (DL) transmission. Transmission by UE 102 to an access node may be called uplink (UL) transmission. UE 102 may be therefore configured to operate as a transmitter for uplink transmissions and as a receiver for downlink transmissions. Access node 104 may be configured to operate as a receiver for uplink transmissions and as a transmitter for downlink transmissions. Communication network 100 may comprise a wireless communication network or a mobile communication network, such as for example a cellular communication network.
[0032] Communication network 100 may comprise other network function(s) or network device(s) in addition, or alternative to, those illustrated in FIG.1. A network device may be configured to implement functionality of one or more network functions. Even though some embodiments have been described in the context of 5G, it is appreciated that embodiments of the present disclosure are not limited to this example network. Example embodiments may be therefore applied in any present or future communication networks.
[0033] In at least some of the example embodiments, UE 102 may provide access node 104 capability information comprising an odd number of antenna ports (i.e., number of antenna ports of UE 102 is an odd integer). The capability information may further comprise coherence information related to antenna
port groups associated to antenna port(s) of uplink, UL, PUSCH and/or UL SRS. Coherence information comprised in the capability information may comprise phase and/or amplitude coherence capability information. The phase and/or amplitude coherence capability information may be, for example, a full coherence capability, a partial coherence capability or a non-coherence capability. This may be performed via, for example, semi-static signaling such as radio resource control, RRC, message.
[0034] In other words, UE 102 may indicate to RAN (comprising e.g., 6G gNB’s), via, for example, semi-static signaling, such as radio resource control, RRC message, UL TX antenna port configuration for PUSCH and/or UL SRS. This indication may comprise number of antenna ports, which, in relation to the disclosure, may be an odd number such as 3,5,7 etc. Moreover, UE 102 may indicate via, for example,
semi-static signaling phase and/or amplitude coherence capability information associated with antenna port groups associated with antenna port(s). Alternatively, the amplitude coherence capability information may be directly associated with antenna port(s).
[0035] For example, UE 102 may indicate access node 104, that number of antenna ports is an odd- number, and the related coherency of, for example, phase, is non-coherent. [0036] Based on the capability information, access node 104 may determine an SRS resource configuration for UE 102 and provide it to UE 102. For example, access node 104 may transmit an SRS resource information element comprising the determined configuration to the UE 102. Information related
to the SRS resource configuration may be used by the UE 102 for determining a SRS resource specific
antenna port mapping, which may enable to minimize inter-antenna port interference due to, for example, UE implementation specific non-coherent SRS antenna ports in the presence of frequency selectivity of
a radio channel. The information may comprise at least one of a number of antenna ports, a number of consecutive OFDM symbols (^symbSRS), a starting position in the time domain (l0), and/or a starting position in the frequency domain (k0) configured for the SRS. The starting position in time domain may be given, for example, by ^0=^symbslot−1−^offset where the offset ^offset∈ {0,1,…,13} counts symbols backwards from the end of the slot and is given by a field indicating starting position contained in a higher
layer parameter for resource mapping and ^offset≥^symbSRS−1. Each antenna port ^^ may be associated with a cyclic shift ^^ and a number of cyclic shifts ^ cs,^ cs,^ SRS , where ^
SRS ∈ {0,1, … , nSRScs, max − 1} is contained in a higher layer parameter for the transmission comb. A transmission comb is a distributed comb-shaped transmission with equally-spaced outputs allocated over the entire bandwidth. The maximum number of cyclic shifts ^
cs,^,^^^ S
RS may depend on the comb-type (^TC). For example, for ^
cs,^,^^^= ^ cs,^,^^^= ^ cs,^,^^^ 6. The maximum number of cyclic
cyclic shift value may refer to actual phase shift values in phase domain. Cyclic offset may refer to an offset value which can have values from 0 to the maximum cyclic length depending on the SRS comb-type. A cyclic offset value may
be used to compute actual phase shift values in phase domain. Cyclic shift offset may correspond to the parameter ^
cs,^ S
RS representing the amount of cyclic shift applied to a signal.
[0037] Configured SRS parameters may further comprise, for example, a comb offset hopping pattern with repetition. The parameter can be set to either ‘[per-symbol]’ or ‘[per-R-repetition]’ subject to UE capability. When the parameter is set to ‘[per-symbol]’, the comb offset hopping pattern is determined by the symbol index, and the comb offset hopping pattern is determined by the symbol index of the first symbol of the repetition when the parameter is set to ‘[per-R-repetition]’.
[0038] Configured SRS parameters may further comprise, for example, cyclic shift hopping for an SRS resource in an SRS resource set with the usage configured for antenna switching, subject to UE capabilities. In cyclic shift hopping, the cyclic shift may be updated at every symbol. For the cyclic shift hopping, a UE can be configured with a subset of cyclic shifts, where the cyclic shift hopping is performed only across the cyclic shifts configured in the subset.
[0039] UE 102 may be configured to transmit an SRS to access node 104 based on the received SRS resource configuration. Sounding reference signal refers to uplink reference signal employed by UE for uplink channel sounding, including channel quality estimation and synchronization.
[0040] In other words, RAN, e.g., access node 104 may provide UE 102 with a UL SRS resource configuration with one or more UL SRS resource with a specific comb-type (e.g., comb-2/4/8 or higher)
with odd number of antenna ports. Based on the UL SRS resource configuration, UE 102 may determine the SRS resource specific mapping. In one example, access node 104 may configure a single SRS resource with the odd number of SRS antenna ports for the UE 102.
[0041] In an implementation form of the disclosure, one or more UL SRS resources may be configured with odd number of TX antenna ports. The TX antenna ports configured for UL SRS resource may be also referred to as SRS antenna ports or UL SRS antenna ports. For example, the configuration may comprise ^SRS =
{ SRS A
P 3,5,7,9,11}, wherein ^AP is the number of TX antenna ports available for SRS. [0042] In other words, an SRS resource set may comprise one or more UL SRS resources, wherein each of the one or more UL SRS resources may be configured with an odd number of TX antenna ports. An SRS resource may refer to a collection of resource elements that are used for transmission of SRS. The resource elements can span multiple physical resource blocks (PRBs) in the frequency domain and N (e.g., 1 or more) consecutive symbol(s) within a slot in the time domain.
[0043] The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. SRS resources, and associated resource elements, may be comb-type specific. A comb-type may indicate a
number of subcarriers in each symbol period carrying an SRS. For example, a comb-type of comb-2 means that every second subcarrier of a given symbol carries the sounding reference signal. Each SRS resource may contain one or more SRS antenna ports with a comb-N (N being an integer) pattern and
span specific symbols and PRBs. Antenna ports, and associated resource elements, may be assigned a comb offset where no frequency staggering of the resource elements inside the SRS resource may be allowed. A comb offset may refer to a difference between a first subcarrier of a comb pattern and a reference subcarrier. A comb offset may indicate a shift of where the comb spacing starts, e.g., a starting RE for an SRS.
[0044] In one example, UE 102 may be configured to determine one or more UL SRS cyclic shift offsets for the one or more UL SRS resources configured with an odd number of TX antenna ports. [0045] For example, UE 102 may be configured to determine, based on the SRS resource configuration, a cyclic shift αi, for an antenna port pi, wherein pi may be 1000+i (e.g., pi = {1000, 1001, 1003… etc.}). The cyclic shift may be determined as follows: cs,^ ^
^ ^
wherein ^
cs,max is the maximum number of cyclic shifts and ^
cs,^ is a cyclic shift offset
associated with different comb types, K
T
C.
[0046] In an implementation form of the disclosure, the cyclic shift offset value associated with different comb types, ^
cs,^ SRS , may be determined as follows:
= or
wherein = or
wherein
[0047] In each of Eq.2.1, Eq.2.2 and Eq.2.3, the ceil() is the smallest integer function. I.e., rounding up to the nearest integer. The ceil() – function is used to obtain an integer value cyclic shift offsets and obtain a phase value for each of the odd number of TX antenna ports. It will be noted that, by applying Eq.’s 2.1-2.3, for some TX antenna port numbers, such as 7 and 9, consecutive antenna port indices do not provide equidistance phase-shift values in phase domain.
[0048] In at least some of the disclosed embodiments, a user equipment (e.g., UE 102) may determine equidistance and/or non-equidistance phase-shift values and/or equidistance and/or non-equidistance cyclic shift offset values for an UL SRS resource with odd number of TX antenna ports available for SRS. The determining the equidistance and non-equidistance phase-shift values and/or the equidistance and
non-equidistance cyclic shift offset values for an UL SRS resource may comprise applying Eq.2.1 or 2.2 or 2.3 depending on the configured SRS antenna ports and corresponding comb-type.
[0049] In one example, UE 102 may be configured to determine a frequency-domain starting position for one or more antenna ports of a UL SRS resource with odd number of TX antenna ports.
[0050] For example, a three antenna port (3-AP) SRS resource with KTC= 4 and associated with three uncoherent antenna port groups, where number of antenna ports per group is three, may be configured.
UE 102 may then determine the frequency-domain starting position, ^ (^ ^
^) , defined by: ^
(^^) ^^(^^) FH R where ^
o F f
H
f
set is frequency resource hopping, if applicable. ^
RPFS
is the frequency resource element offset associated with partial frequency sounding, if ^
^(^ cs,max ^ ^), for the 3-AP SRS resource with K
TC= 4, ^
SRS = 12 can be calculated by using single resource specific comb offset ^^TC configured by a network as: ^ ^ ^SRS ^
cs,max
[0051] Similarly, for a 5-AP SRS resource ^ cs,max ^ (^^)
In case ^
^(^^) is determined for a 3-AP SRS resource with K
cs,max TC= 2 with ^
SRS ^^ (^^) may calculated as:
^
^ )mod ^ , if ^SRS =
3, ^̅ = 1000 and ^ cs,max ^^ ^^ AP ^ SRS = ^^/4)mod ^^^, if ^SRS A
P = 3, ^^̅ = 1001 and ^ = ^^/4)mod ^^^, if ^SRS A
P = 3, ^^̅ = 1002 and ^SRS =
and for a 5-AP SRS resource with K
cs,max TC= 2 with ^
^^ (^^) may be calculated
^
^^)mod ^^^, if ^SRS A
P = 5, ^^̅ = {1001, 1003} and ^ = /4)mod ^^^, if ^SRS A
P = 5, ^^̅ = {1000,1002,1004} and ^SRS =
[0052] In one example, UE 102 may be configured to detect an indication indicating a comb offset value corresponding to a resource element associated with a highest number of SRS antenna ports
among an odd number of SRS antenna ports configured for an SRS resource. For example, when a number of potential comb-offset values of the SRS resource is smaller than the configured odd number
of TX SRS antenna ports, UE 102 may be implicitly indicated to use a configured single comb offset value, ^
^ TC, as an anchor resource element offset (e.g., a first resource element), which encapsulates the highest number of SRS antenna ports with respect to other resource elements of the SRS resource. UE
102 may be further configured to assign rest of the SRS antenna ports evenly with other resource elements of the SRS resource.
[0053] When a resource specific frequency domain anchor offset is not configured, UE 102 may be indicated implicitly that a maximum frequency domain comb offset value or a smallest frequency domain comb offset value is associated with the highest number of UL SRS antenna ports among the total (odd) number of UL SRS antenna ports by evenly distributing UL SRS antenna ports across possible frequency
comb offset values. [0054] For example, the SRS resource may be configured with a comb-2, ^^TC = 0 with three SRS antenna ports. UE 102 is implicitly indicated to apply for the configured comb offset value two first antenna ports (e.g., port 1000 and 1001) and for other resource element(s), the remaining antenna port(s) (e.g.,
port 1002). In other words, UE 102 may determine that the smallest frequency domain comb offset is associated with the highest number of antenna ports, e.g., 2 out of 3. Then, the antenna ports 1000 and 1001 are associated with frequency domain resource element offset 0, and the antenna port 1002 is
associated with resource element 0+1. Alternatively, the value ^^TC in addition to the frequency domain comb offset can also implicitly indicate the frequency domain anchor offset based on which UE 102 determines how antenna ports are assigned in frequency domain.
[0055] Alternatively, UE 102 may be implicitly indicated with an anchor resource element offset that is associated with a maximum comb offset value. Each comb-type may be associated with a pre-set maximum comb offset value. For example, for comb-2, comb-4, comb-7, this value of maximum comb offset is 1,3,7, respectively. UE 102 may then determine the comb offset corresponding to the resource element with the highest number of SRS antenna ports among the odd number of SRS antenna ports based on the maximum comb offset value.
[0056] In one example, UE 102 may be indicated either implicitly or explicitly the anchor resource element offset, which may be associated with a highest number of TX antenna ports out of odd number of TX antenna ports with respect to the rest of SRS resource elements. For example, UE 102 may determine cyclic-shift offset values and/or corresponding phase offset values associated with antenna
ports of the anchor resource element offset such that difference between cyclic-shift offset values and/or phase offset values is as large as possible. This may enable a robust channel estimation associated with antenna ports.
[0057] When the number of potential comb-offset values of a SRS resource is smaller than a configured odd number of SRS antenna ports, UE 102 may be also explicitly indicated which comb offset to use to determine the resource element associated with the highest number of SRS antenna ports
among the number of SRS antenna ports. For example, the SRS resource configuration may comprise an additional information element dedicated for the purpose, comprising a comb offset value for the
anchor resource element offset, e.g., ^^TC-Odd-TX, to be used. The dedicated comb offset value ^^TC-Odd-TX may be used as the anchor resource element offset which may encapsulate a highest number of antenna
ports with respect to the rest of SRS resource elements of the SRS resource. In an implementation form, when the SRS resource is not configured with the ^^TC-Odd-TX, the UE 102 may determine the resource element with the highest number of SRS antenna ports based on the configured single comb-offset value or the maximum comb offset value.
[0058] In one example, when UE 102 is configured with UL SRS resource with different comb-types and comb-offset values, cyclic-shift offset sets can be shared such that consecutive antenna port indices
do not share consecutive cyclic shift offset values and/or cyclic shift phase offsets. [0059] In one example, when UL SRS resource is configured with odd number of SRS antenna ports with K
cs,max TC= 2 , ^
SRS = 8 and ^SRS A
P = 9, and UE 102 has determined cyclic shift offset values and SRS corresponding phase offsets as described in this disclosure with ^
AP = 5, UE 102 can re-use these cyclic-shift offset values separately for both comb offset values such that the total number of SRS antenna port is equal to 9.
[0060] For example, for comb-offset 0: first 4 different cyclic shift offset values can be assigned for first 4 antenna ports. i.e. antenna port indices 1-4, and for comb offset 1: first 5 different cyclic shift offset values can be assigned for antenna port indices from 5-9. The same principle can be applied also for th ^
cs,max SRS = SRS KTC= 8 wi
6 and ^AP = 7,9,11. [0061] FIG.2 illustrates an example of an apparatus 200 configured to practice one or more example embodiments. Apparatus 200 may comprise a device such as UE 102, a terminal device, or access node 104, an access point, a base station, a radio network node, or a split portion thereof (e.g., a central or distributed unit of an access node), a network device, a terminal device, or in general any apparatus
configured to implement functionality described herein. Apparatus 200 may comprise at least one processor 202. The at least one processor 202 may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal
processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.
[0062] Apparatus 200 may further comprise at least one memory 204. The memory 204 may be configured to store, for example, computer program code or the like, for example operating system
software and application software. Memory 204 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination thereof. For example, the memory may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM),
EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). Memory 204 is provided as an example of a (non-transitory) computer readable medium. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).
[0063] Apparatus 200 may further comprise a communication interface 208 configured to enable apparatus 200 to transmit and/or receive information. Communication interface 208 may comprise an external communication interface, such as for example a radio interface between UE 102 and access node 104, or a communication interface between a central unit and distributed unit(s) of an access node (e.g., an Fs-U and/or Fs-C interface). Communication interface 208 may comprise one or more radio
transmitters or receivers, which may be coupled to one or more antennas or apparatus 200, or be configured to be coupled to one or more antennas external to apparatus 200.
[0064] Apparatus 200 may further comprise other components and/or functions such as a user interface (not shown) comprising at least one input device and/or at least one output device. The input device may take various forms such a keyboard, a touch screen, or one or more embedded control buttons. The output device may for example comprise a display, a speaker, or the like.
[0065] When apparatus 200 is configured to implement some functionality, some component and/or components of apparatus 200, such as for example the at least one processor 202 and/or the at least one memory 204, may be configured to implement this functionality. Furthermore, when the at least one
processor 202 is configured to implement some functionality, this functionality may be implemented using program code 206 comprised, for example, in the at least one memory 204. [0066] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an example embodiment,
apparatus 200 comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code 206, when executed, to execute the embodiments of the operations and
functionality described herein. Program code 206 is provided as an example of instructions which, when executed by the at least one processor 202, cause performance of apparatus 200.
[0067] 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), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system- on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), graphics processing units (GPUs), or the like.
[0068] Apparatus 200 may be configured to perform, or cause performance of, method(s) described herein or comprise means for performing method(s) described herein. In one example, the means comprises the at least one processor 202, the at least one memory 204 including instructions (e.g.,
program code 206) configured to, when executed by the at least one processor 202, cause apparatus 200 to perform the method(s). In general, computer program instructions may be executed on means providing generic processing functions. Such means may be embedded for example in a personal computer, a smart phone, a network device, or the like. The method(s) may be thus computer-
implemented, for example, based on algorithm(s) executable by the generic processing functions, an example of which is the at least one processor 202. The means may comprise transmission or reception means, for example one or more radio transmitters or receivers, which may be coupled or be configured
to be coupled to one or more antennas. Apparatus 200 may comprise, for example, a network device, for example, an access node, an access point, a base station, or a central/distributed unit thereof. Although apparatus 200 is illustrated as a single device, it is appreciated that, wherever applicable, functions of apparatus 200 may be distributed to a plurality of devices. [0069] Examples of different UL SRS resource configurations are described below, in reference to accompanying drawings Fig. 3, Fig. 4, Fig. 5 and Fig. 6. The different example UL SRS resource configurations may be applied in example embodiments, such as apparatus 200 or a related method
performed by, for example apparatus 200. A UL SRS resource configuration may be abbreviated as UL SRS RC. It will be noted that the examples of UL SRS RC’s given in reference to FIG.3 to FIG. 6 may imply only one OFDM symbol occupying a resource element (e.g., subcarrier frequency) however, example embodiments may be applied with more than one OFDM symbol per resource element. A UL SRS RC may be, for example, obtained by apparatus 200 and transmitted by an access node. A UL SRS RC may be based on information about antenna groups obtained by a network via capability signalling associated with PUSCH and/or SRS, where UE indicates the number of antenna groups and their corresponding coherency type (e.g., non-coherent/partially coherent/fully coherent).
[0070] FIG.3 illustrates an example UL SRS RC 300 in accordance with example embodiments. UL SRS RC 300 comprises three SRS antenna ports for codebook and antenna switching usages with three non-coherent antenna port groups. UL SRS resource configuration 300 may be referred to as UL SRS RC 300. UL SRS RC 300 may be applied for codebook and antenna-switching applications. [0071] UL SRS RC 300 comprises three SRS resource elements, REs (e.g., a subcarrier): a first RE 302, a second RE 304 and a third RE 304. ^SRS A
P = 3 and port 1000 is associated with first RE 302, port 1001 is associated with second RE 304 and port 1002 is associated with third RE 306.
[0072] UL SRS RC 300 further comprises a comb type 4 i.e., KTC = 4. [0073] UL SRS RC 300 further comprises a maximum cyclic shift value of 12. In other words, ^ cs,max S
RS = 12.
[0074] The cyclic shift in UL SRS 300 associated with port 1000 is zero i.e., ^^^^^ = 0. The cyclic shift in UL SRS 300 associated with port 1001 is four i.e., ^^^^^ = 4 and the cyclic shift associated with port 1002 is eight i.e., ^^^^^ = 8. [0075] UL SRS RC 300 further comprises a comb offset value of zero i.e., ^^TC= 0. [0076] FIG. 4 illustrates an example UL SRS RC 400 in accordance with example embodiment. UL SRS RC 400 may comprise three SRS antenna ports for codebook and antenna switching usages with three non-coherent antenna port groups.
[0077] UL SRS RC 400 comprises two SRS resource elements, a fourth RE 402, and a fifth RE 404. SRS ^
AP = 3 and port 1000 and port 1001 are associated with fourth RE 402, and port 1002 is associated with fifth RE 404.
[0078] UL SRS RC 400 further comprises a comb type 2 i.e., KTC = 2. [0079] UL SRS RC 400 further comprises a maximum cyclic-shift value of 8. In other words, ^ cs,max =
8.
[0080] The cyclic shift in UL SRS RC 400 associated with port 1000 is zero i.e., ^^^^^ = 0. The cyclic shift in UL SRS RC 400 associated with port 1001 is four i.e., ^^^^^ = 4 and the cyclic shift associated with port 1002 is eight i.e., ^^^^^ = 8. [0081] UL SRS RC 400 further comprises a comb-offset value of zero i.e., ^^TC= 0. [0082] FIG. 5 illustrates an example UL SRS RC 500 in accordance with example embodiments. UL SRS RC 500 may comprise five SRS antenna ports for codebook and antenna switching usages with three non-coherent antenna port groups.
[0083] UL SRS RC 500 comprises four SRS resource elements, a sixth RE 502, a seventh RE 504, SRS an eight RE 506 and a ninth RE 508. ^
AP = 5 and port 1000 is associated with sixth RE 502. Port
1001 is associated with seventh RE 504. Port 1002 is associated with eight RE 506 and port 1003 and port 1004 are associated with ninth RE 508. In other words, the ninth RE 508 is a resource element associated with the highest number of antenna ports among the odd number of antenna ports.
[0084] UL SRS RC 500 further comprises a comb type 4 i.e., KTC = 4. [0085] UL SRS RC 500 further comprises a maximum cyclic-shift value of 12. In other words, ^ cs,max S
RS = 12.
[0086] The cyclic shift in UL SRS RC 500 associated with port 1000 is zero i.e., ^^^^^ = 0. The cyclic shift in UL SRS RC 500 associated with port 1001 is three i.e., ^^^^^ = 3, the cyclic shift associated with port 1002 is five i.e., ^^^^^ = 5, the cyclic shift associated with port 1003 is seven i.e., ^^^^^ = 7 and the cyclic shift associated with port 1004 is ten i.e., ^^^^^ = 10. [0087] UL SRS RC 500 further comprises a comb offset value of zero i.e., ^^TC= 0. [0088] FIG. 6 illustrates an example UL SRS RC 600 in accordance with example embodiments. UL SRS RC 600 may comprise five SRS antenna ports for codebook and antenna switching usages with three non-coherent antenna port groups.
[0089] UL SRS RC 600 comprises two SRS resource elements, a tenth RE 602 and an eleventh RE SRS 604. In other words, ^
AP = 5 and ports 1001, 1003 are associated with tenth RE 602. Ports 1000, 1002 and 1004 are associated with eleventh RE 604. Hence, the eleventh RE 604 is a resource element associated with the highest number of antenna ports among the odd number of antenna ports.
[0090] UL SRS RC 600 further comprises a comb-type 2 i.e., KTC = 2. [0091] UL SRS RC 600 further comprises a maximum cyclic shift value of 8. In other words, ^ cs,max =
8.
[0092] The cyclic shift in UL SRS RC 600 associated with port 1001 is two i.e., ^^^^^ = 2. The cyclic shift in UL SRS RC 600 associated with port 1003 is five i.e., ^^^^^ = 5. The cyclic shift associated with port 1000 is zero i.e., ^^^^^ = 0, the cyclic shift associated with port 1002 is four i.e., ^^^^^ = 4 and the cyclic shift associated with port 1004 is seven i.e., ^^^^^ = 7. [0093] UL SRS RC 500 further comprises a comb offset value of zero i.e., ^^TC= 0. [0094] FIG.7 illustrates an example of a method 700 for mapping odd number of UL SRS antenna ports, according to Example embodiment 1 of method 700. Method 700 may be performed by a terminal device, e.g., UE 102, or by a control apparatus configured to control the functioning thereof, when
installed therein. The control apparatus may comprise, for example, the apparatus 200. [0095] At operation 702, the method may comprise obtaining information related to mapping of an odd number of SRS antenna ports to one or more frequency resource elements of an SRS resource.
[0096] At operation 704, the method may comprise transmitting the SRS resource based on the obtained information. The obtained information may comprise, for example, an implicit or an explicit indication for mapping of one or more resource elements to one or more SRS antenna ports. The obtained information may further comprise an indication for mapping one or more SRS antenna ports with cyclic shift values.
[0097] The method 700 may be performed, for example, according to any of the following example embodiments:
[0098] Example embodiment 2: Method 700 according to Example embodiment 1, wherein the obtained information comprises at least one of: the odd number of SRS antenna ports; a comb-type; or an indication of a comb offset value to be used for mapping the odd number of SRS antenna ports to one or more frequency resource element of the SRS resource.
[0099] Example embodiment 3: Method 700 according to Example embodiment 2, wherein the indication is based on a number of potential comb offset values being smaller than the odd number of SRS antenna ports and one or more configuration parameters of the SRS resource
[0100] Example embodiment 4: Method 700 according to any of Example embodiments 2 or 3, wherein the indication is based on a single comb offset value configured for the SRS resource.
[0101] Example embodiment 5: Method 700 according to Example embodiment 4, wherein the single comb offset value is a resource specific comb offset value configured for the odd number of SRS antenna ports.
[0102] Example embodiment 6: Method 700 according to any of Example embodiments 2 to 5, wherein the indication is based on a comb-type of the SRS resource, and the method further comprises determining the comb offset value to be used for the mapping based on a maximum comb offset value associated with the comb-type of the SRS resource.
[0103] Example embodiment 7: Method 700 according to any of Example embodiments 2 to 6, wherein the method comprises determining a frequency resource element associated with a highest number of antenna ports among the odd number of SRS antenna ports with respect to other frequency resource elements of the SRS resource based on the indicated comb offset value.
[0104] Example embodiment 8: Method 700 according to Example embodiment 7, wherein the method comprises determining at least one of cyclic offset values or corresponding phase offset values associated with the antenna ports of the frequency resource element associated with the highest number of antenna ports based on a difference between the at least one of cyclic offset values or corresponding phase offset values; and transmitting the SRS resource based on at least one the determined cyclic offset values or the corresponding phase offset values.
[0105] Example embodiment 9: Method 700 according to any of Example embodiments 7 or 8, wherein the method comprises assigning remaining SRS antenna ports of the odd number of SRS antenna ports not associated with the frequency resource element associated with the highest number of SRS antenna ports evenly with other frequency resource elements of the SRS resource.
[0106] Example embodiment 10: Method 700 according to any of Example embodiments 1 to 9, wherein the frequency resource elements comprise at least one of: cyclic shift, cyclic shift offset values, phase shift values or frequency-domain starting position.
[0107] Example embodiment 11: Method 700 according to any of Example embodiments 1 to 10, wherein the method comprises transmitting, to an access node, capability information of the terminal device related to at least one of the odd number of antenna ports and coherency information associated
with antenna port groups with one or more SRS antenna ports; and receiving, from the access node, a configuration of the SRS resource with the odd number of SRS antenna ports.
[0108] Example embodiment 12: Method 700 according to Example embodiment 11, wherein the method comprises determining, based on the received SRS resource configuration, cyclic shifts for the odd number of SRS antenna ports based on a maximum number of cyclic shifts and a cyclic shift offset value for different comb-types, wherein the cyclic shift offset values are calculated to comprise an integer value; and wherein the SRS resource is further transmitted based on the determined cyclic shifts.
[0109] Example embodiment 13: Method 700 according to Example embodiment 12, wherein the method comprises determining at least one of equidistance or non-equidistance phase shift values for the SRS resource with the odd number of antenna ports based on the calculated cyclic shift values and a comb-type of the SRS resource; and wherein the SRS resource is transmitted based on the determined at least one of equidistance or non-equidistance phase-shift values.
[0110] Example embodiment 14: Method 700 according to any of Example embodiments 1 to 13, wherein the method comprises determining one or more frequency-domain starting positions for antenna ports associated with the SRS resource with the odd number of SRS antenna ports based on at least one of a frequency resource element offset associated with frequency hopping, a frequency resource element
offset associated with partial frequency sounding, a comb-type or comb-offset value; and wherein the SRS resource is transmitted based on the determined one or more frequency-domain starting positions.
[0111] Example embodiment 15: Method 700 according to any of Example embodiments 1 to 14, wherein the SRS resource is associated with different comb-types and comb-offset values, and wherein the apparatus is further caused to determine cyclic offset values for the odd number of antenna ports based on one or more sets of cyclic offset values such that consecutive antenna port indices do not share at least one of consecutive cyclic shift offset values or consecutive cyclic shift phase values; and wherein the SRS resource is further transmitted based on the determined cyclic shift offset values.
[0112] FIG. 8 illustrates an example of a method 800 for mapping odd number of UL SRS antenna ports, according to Example embodiment 1 of Method 800. Method 800 may be performed by a terminal device, e.g., UE 102, or by a control apparatus configured to control the functioning thereof, when
installed therein. The control apparatus may comprise, for example, the apparatus 200. [0113] At operation 802, the method may comprise obtaining resource specific information related to a resource element associated with a highest number of sounding reference signal, SRS, antenna ports among an odd number of SRS antenna ports configured for an SRS resource.
[0114] At operation 804, the method may comprise transmitting the sounding reference signal resource based on the obtained information. The obtained information may comprise, for example, an implicit or an explicit indication of a comb offset corresponding to the resource element associated with the highest number of SRS antenna ports among the odd number of SRS antenna ports with respect to other resource elements of the SRS resource. The resource elements may comprise, for example, comb-
type specific frequency domain resources. In one example, the resource elements may comprise at least one of the following: cyclic shift(s), cyclic shift offset values, phase shift values or frequency-domain starting position(s).
[0115] The method 800 may be performed, for example, according to any of the following example embodiments:
[0116] Example embodiment 2: Method 800 according to Example embodiment 1, wherein the obtained information comprises an indication indicating a comb offset value corresponding to the resource element associated with the highest number of SRS antenna ports.
[0117] Example embodiment 3: Method 800 according to Example embodiment 2, wherein the indication is based on a number of potential comb offset values being smaller than the odd number of
SRS antenna ports and configuration parameters for the SRS resource. The configuration parameters for the SRS resource may comprise, for example, a comb offset value or a comb-type. In one example, the comb offset value may be indicated with an additional information element dedicated for the odd number of SRS antenna elements.
[0118] Example embodiment 4: Method 800 according to Example embodiment 2 or 3, wherein the indication comprises a single comb offset value configured for the SRS resource; and the comb offset value corresponding to the resource element associated with the highest number of SRS antenna ports is obtained based on the single comb offset value configured for the SRS resource.
[0119] Example embodiment 5: Method 800 according to any of Example embodiments 2 to 3, wherein the indication comprises a dedicated comb offset value configured for the odd number of SRS antenna ports; and the comb offset value corresponding to the resource element associated with the highest
number of SRS antenna ports is obtained based on the dedicated comb offset value configured for the odd number of SRS antenna ports.
[0120] Example embodiment 6: Method 800 according to any of Example embodiments 2 or 3, wherein the indication indicates to use a maximum comb offset value associated with the SRS resource; and the comb offset value corresponding to the resource element associated with the highest number of SRS antenna ports is obtained based on the maximum comb offset value associated with the SRS resource.
[0121] Example embodiment 7: Method 800 according to any of Example embodiments 1 to 6, wherein the method comprises assigning remaining SRS antenna ports of the odd number of SRS antenna ports not associated with the resource element associated with the highest number of SRS antenna ports evenly with other resource elements of the SRS resource.
[0122] Example embodiment 8: Method 800 according to any of example embodiments 1 to 7, wherein the method comprises determining at least one of cyclic shift offset values or corresponding phase offset values associated with the SRS antenna ports of the resource element based on a difference between the at least one cyclic shift offset values or corresponding phase offset values; and wherein the SRS resource is transmitted based on the determined at least one of cyclic shift offset values or corresponding phase offset values.
[0123] Example embodiment 9: Method 800 according to any of example embodiments 1 to 8, wherein the method comprises transmitting, to an access node, capability information of the terminal device related to at least one of odd number of antenna ports or coherency information associated with antenna port groups with one or more SRS antenna ports; and receiving, from the access node, the configuration of the SRS resource with the odd number of SRS antenna ports.
[0124] Example embodiment 10: Method 800 according to Example embodiment 9, wherein the method further comprises determining, based on the received SRS resource configuration, cyclic shifts for the odd number of SRS antenna ports based on a maximum number of cyclic shifts and a cyclic shift offset value for different comb-types, wherein the cyclic shift offset values are calculated to comprise an
integer value; and wherein the SRS resource is transmitted based on the determined cyclic shifts. [0125] Example embodiment 11: Method 800 according to Example embodiment 10, wherein the method comprises determining at least one of equidistance or non-equidistance phase shift values for the SRS resource with the odd number of antenna ports based on the calculated cyclic shift values and a comb-type of the SRS resource; and wherein the SRS resource is further transmitted based on the determined at least one of equidistance or non-equidistance phase-shift values.
[0126] Example embodiment 12: Method 800 according to any of Example embodiments 1 to 11, wherein the method comprises determining one or more frequency-domain starting positions for antenna ports associated with the SRS resource configuration with the odd number of SRS antenna ports based
on at least one of a frequency resource element offset associated with frequency hopping, a frequency resource element offset associated with partial frequency sounding, a comb-type or comb offset value;
and wherein the SRS resource is transmitted based on the determined one or more frequency-domain starting positions.
[0127] Example embodiment 13: Method 800 according to any of Example embodiments 1 to 12, wherein the SRS resource is associated with different comb-types and comb offset values, and wherein the method comprises determining cyclic offset values for the odd number of antenna ports based on one or more sets of cyclic offset values such that consecutive antenna port indices do not share at least one
of consecutive cyclic shift offset values or consecutive cyclic shift phase values; and wherein the SRS resource is transmitted based on the determined cyclic shift offset values.
[0128] Further features of the methods directly result for example from functionality of UE 102, or access node(s) 104, as described throughout the description, claims, and drawings, and are therefore not repeated here. An apparatus, for example a device such as UE 102, or an access node, may be configured to perform or cause performance of any aspect of the method(s) described herein. Further, a
computer program, a computer program product, or a (non-transitory) computer-readable medium may comprise instructions for causing, when executed by an apparatus, the apparatus to perform any aspect of the method(s) described herein. Further, an apparatus may comprise means for performing any aspect of the method(s) described herein. According to an example embodiment, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one
processor, cause the apparatus at least to perform any aspect of the method(s). [0129] 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. [0130] 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.
[0131] 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.
[0132] The steps or operations 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 scope of the subject matter described herein. Aspects of any of
the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought. [0133] 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.
[0134] As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.
[0135] Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.
[0136] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.
[0137] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.
[0138] 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 scope of this specification.