WO2025201699A1 - Wireless measurement - Google Patents

Abstract

According to an example aspect of the present invention, there is provided an apparatus, such as a user equipment, configured to receive first configuration information indicative of a measurement to be performed on a carrier, receive a measurement signal transmitted over the carrier, and perform the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

Description

WIRELESS MEASUREMENT

FIELD

[0001] The present disclosure relates to wireless communication, such as wireless communication in cellular networks.

BACKGROUND

[0002] In cellular communication networks user equipments, UEs, roam in a coverage area of the network and attach themselves to cells of the network.

[0003] To obtain dependable communication with a network, a UE may perform measurements of signals transmitted by cells of the network, for example using time and frequency resources, so that handover decisions, for example, may be informed by relevant and up-to-date data.

[0004] The signals measured by the UEs may be transmitted in a synchronization signal block, SSB, for example.

SUMMARY

[0005] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0006] According to a first aspect of the present disclosure, there is provided an apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to receive first configuration information indicative of a measurement to be performed on a carrier, receive a measurement signal transmitted over the carrier, and perform the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

[0007] According to a second aspect of the present disclosure, there is provided an apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to repeatedly broadcast, over an air interface, a sequence of synchronization signal blocks, SSBs, and transmit, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one- to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

[0008] According to a third aspect of the present disclosure, there is provided a method comprising receiving first configuration information indicative of a measurement to be performed on a carrier, receiving a measurement signal transmitted over the carrier, and performing the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

[0009] According to a fourth aspect of the present disclosure, there is provided a method, comprising repeatedly broadcasting, over an air interface, a sequence of synchronization signal blocks, SSBs, and transmitting, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

[0010] According to a fifth aspect of the present disclosure, there is provided an apparatus comprising means for receiving first configuration information indicative of a measurement to be performed on a carrier, means for receiving a measurement signal transmitted over the carrier, and means for performing the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

[0011] According to a sixth aspect of the present disclosure, there is provided an apparatus comprising means for repeatedly broadcasting, over an air interface, a sequence of synchronization signal blocks, SSBs, and means for transmitting, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

[0012] According to a seventh aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least receive first configuration information indicative of a measurement to be performed on a carrier, receive a measurement signal transmitted over the carrier, and perform the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

[0013] According to an eighth aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least repeatedly broadcast, over an air interface, a sequence of synchronization signal blocks, SSBs, and transmit, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one- to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention; [0015] FIGURE 2A illustrates signal timing in accordance with at least some embodiments of the present invention;

[0016] FIGURE 2B illustrates signal timing in accordance with at least some embodiments of the present invention;

[0017] FIGURE 2C illustrates signal timing in accordance with at least some embodiments of the present invention;

[0018] FIGURE 2D is a flow diagram of UE behavior in accordance with at least some embodiments of the present invention;

[0019] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0020] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention, and

[0021] FIGURES 5 and 6 are flow graphs of methods in accordance with at least some embodiments of the present invention.

EMBODIMENTS

[0022] Mechanisms are herein disclosed to provide, in a cellular communication network, synchronization signal blocks, SSBs and additionally measurement signals which are usable in performing a measurement by a UE, for example for mobility purposes. The measurement signal may be a replica of a constituent part of the SSB. The measurement performed using the measurement signal may serve a similar purpose as a measurement performed using an SSB, such as mobility management, wherefore providing the measurement signal, periodically or aperiodically, enables providing the SSB less frequently while maintaining flexibility in the system. In detail, measurement gaps may be configured in UEs to enable performing measurements of the measurement signals, rather than, or in addition to, the SSBs, so that the measurement gaps configured in plural UEs do not cluster in time to occur at more or less at the same time to coincide with SSBs. This provides the beneficial technical effect that scheduling may be conducted in a more versatile manner in e.g. neighbouring cells, and an effective utilization rate of the network is enhanced. A UE cannot be scheduled when it’s in a measurement gap, wherefore it is suboptimal if a significant fraction of UEs are in a measurement gap at the same time, as it leads to a reduced effective utilization rate of the network.

[0023] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. This system includes base stations 130, 135 in communication with UEs, such as UE 110. A radio link connects base station 130 with UE 110. The radio link may be bidirectional, comprising an uplink, UL, to convey information from UE 110 toward base station 130, and a downlink, DL, to convey information from the base station 130 toward UE 110. A cellular communication system may comprise hundreds or thousands of base stations, of which only two are illustrated in FIGURE 1 for the sake of clarity of the illustration. The base stations may be distributed in that they comprise a centralized unit, CU, and one or more distributed unit, DU. A base station is an example of a base node. In general terms, the base station and the UE are both apparatuses.

[0024] Base station 130 is further coupled communicatively with core network node 140, which may comprise, for example, a mobility management entity, MME, or access and mobility management function, AMF. The core network node 140 may be coupled with further core network nodes, and with a network 150, which may comprise the Internet or a corporate network, for example. The system may communicate with further networks via network 150. Examples of the further core network nodes, which are not illustrated in FIGURE 1 for the sake of clarity, include gateways and subscriber information repositories. Core network nodes may be virtualized in the sense that they may run as software modules on computing substrates, such that more than one virtualized network node may run on a same computing substrate. The network may be configured to function in accordance with a suitable cellular standard such as long term evolution, LTE, fifth generation, 5G, which is also known as New Radio, NR, or sixth generation, 6G standards as defined by the the 3^rd generation partnership project, 3GPP. To obtain interoperation, UEs attaching to the network are configured to support a same standard as the network.

[0025] Base station 130 controls and operates, in the example of FIGURE 1, cells 130A and 130B, of which UE 110 is in the situation illustrated in FIGURE 1 attached with cell 130A, and base station 135 controls and operates, in the example of FIGURE 1, cells 135A and 135B. The number of cells, or beams, may be in excess of what is illustrated in FIGURE 1. It is also possible that a base station has a single cell or beam. While illustrated as sector-shaped, cells of a same base station may be omnidirectional and operate on different frequencies, for example. A mobility event may comprise a switch from one beam to another beam of the same cell, or a switch from one cell to another cell. To support mobility procedures, UEs, including UE 110, are configured to conduct mobility measurements to measure signal strengths of adjacent beams and/or cells, and report results of these measurements to the network, which may then take a decision concerning a mobility event, such as a beam change or a cell switch.

[0026] Cells, such as cells 130A, 130B, 135A and 135B are configured to transmit synchronization signals, such as primary synchronization signal, PSS, and secondary synchronization signal, SSS, to enable synchronization of UEs to the frame structure of the cells, for example in connection with initial attach or mobility procedures.

[0027] In 5G, for example, cells are configured to provides a synchronization signal block, SSB, which comprises a PSS, SSS, and a physical broadcast channel, PBCH. The PBCH of 5G includes a demodulation reference signal, DMRS, for PBCH demodulation. The SSB may be provided, in 5G, using a contiguous resource block of four OFDM symbols in the time domain and 20 physical resource blocks, PRBs, in the frequency domain, wherein each PRB in 5G amounts to twelve subcarriers. In 5G, the PSS is an m-sequence and the SSS is a gold sequence, which is obtained from two m-sequences of equal length using an exclusive-OR operation. The PSS and SSS of 5G are transmitted using binary phase-shift keying, BPSK, while the PBCH of 5G is transmitted using quadrature phase shift keying, QPSK. The PSS is used for acquiring time and frequency synchronization with the cell, while the SSS is used for more precise frequency synchronization, and the PBCH is used in frame and half-frame synchronization and to convey a DMRS, used for slot timing. The PBCH may also be used to convey configuration information the UE may use in accessing the cell, such as an antenna configuration, for example. Further, a physical cell identifier, PCI, is encoded into the PSS and SSS. In detail, the PCI, N^¹¹, may be defined by N^¹¹ = -sequence which depends on 1V_ID and hence there are three possible m-sequences that may be used as the PSS in 5G. SSS is a gold-sequence which depends, at least in 5G, on both and N^ .

[0028] A UE will occasionally need to perform mobility measurements on different radio-access technologies, RATs, than the one on which it is attached, or on a different frequency than the one it is currently using. To enable such measurements the UE may be provided with a measurement gap so the UE can switch to the other RAT, or tune to the other frequency, perform the measurement, and then return to the original RAT or frequency before the measurement gap ends. A typical measurement gap length in LTE is 6 milliseconds, ms, enabling a 5 ms measurement time and radio re-tuning time of 0.5 ms at the beginning and the end of the measurement gap but within the actual measurement gap. The measurement gap may repeat with a given time periodicity, for example every 40 ms or 80 ms. In LTE, PSS and SSS may be transmitted once every 5 ms, for example. NR also uses gap-assisted measurements, including intra-frequency gap-assisted measurements in addition to inter-frequency and inter-RAT gap-assisted measurements. In NR measurement gaps may be used in intra-frequency measurements when the measurements are conducted outside the UE’s active bandwidth part, BWP.

[0029] 3GPP has defined different measurement gap lengths of 1.5, 3, 3.5, 4, 5.5, and 6 ms with different measurement gap repetition time periodicities of 20, 40, 80, and 160 ms. A time periodicity of x milliseconds means that the event takes place at fixed intervals, every x milliseconds. Examples of configurable measurement gap patterns are provided in the following table.

[0030] For example in NR, the assumed radio re-tuning time is 0.5 ms for measurement gaps in frequency range 1, FR1, range and 0.25 ms for frequency range 2, FR2. For example, a gap length of 4 ms for FR1 measurements would allow 3 ms for actual cell detection and measurements and a gap length of 3.5 ms for FR2 would allow 3 ms for actual measurements. During the measurement gaps the measurements are performed on, for example, SSBs of the neighbour cells. The network provides the UE with a measurement configuration of candidate target cells to measure. For NR carriers this configuration includes e.g. the timing of neighbour cell SSBs using SS/PBCH block measurement timing configuration, SMTC. Alternatively to including the SMTC, the measurement configuration may more simply be arranged by the network to coincide with the SMTC in the time domain. In general the measurement configuration informs the UE which carrier frequency to measure, and when to measure it.

[0031] The network configures the UE measurement gap and the timing configuration of the cell to be measured such that the UE can measure SSBs within the SMTC or other timing window during the measurement gap. The network may configure the SMTC duration to be sufficiently long to accommodate all SSBs that are being transmitted, and provide a measurement gap pattern to UEs which ensures that the SMTC, or other SSB transmission window, of the measured target(s) are fully within the measurement gap. The UE may thus receive both a measurement configuration and a measurement gap configuration. Both of these configurations may be arranged by the network to coincide with the measurement signal time periodicity in a cell that is to be measured by the UE.

[0032] For SSB based intra-frequency measurements, the network may configure measurement gaps if any of the UE configured BWPs do not contain the frequency domain resources of the SSB associated to the initial DL BWP. For SSB based inter-frequency measurements, the network may configure measurement gaps if the UE supports per-FR measurement gaps and if the carrier frequency to be measured is in same frequency range as any of the serving cells and UE has indicated that it needs measurement gaps. In this case the measurement gaps may be configured to only apply for a specific FR. The network may also configure gaps for SSB based inter-frequency measurements if the UE supports per-UE measurement gaps and the UE has indicated that it needs gaps to perform the measurements. In this case, the target measurement object can be configured on any frequency range, FR1 or FR2, and the gap configured by the network applies to all FR’s.

[0033] Inter-RAT measurements in NR are limited to E-UTRA. For a UE configured with E-UTRA inter-RAT measurements, a measurement gap configuration is most likely to be provided from the network when the UE only supports per-UE measurement gaps, or when the UE supports per-FR measurement gaps and at least one of the NR serving cells is in FR1. Cell measurements in NR, for example SS-RSRP (reference signal received power) and SS-RSSQ (reference signal received quality), are performed using the SSS.

[0034] In LTE, PSS and SSS, and cell-specific reference signal, CRS, used for cell detection and measurements, are transmitted continuously and repeated every 5 ms with CRS in every slot. In NR, an SSB burst comprising PSS, SSS and PBCH may be transmitted less frequently. However, if the carrier/cell is assumed to be detected for UE initial access the SSB must be repeated, in NR, once every 20 ms. Otherwise, NR supports SSB transmission time periodicity of 5, 10, 20, 40, 80 and 160ms. In NR beamforming is supported for the SSB and depending on the carrier frequency range there can be up to 4, 8 or 64 SSBs transmitted in the SSB burst, also known as an SSB sequence. This is shown in the table below:

[0035] This SSB design can cause some problems on network implementation complexity. While it enables relaxing the time periodicity of always-on signals in NR, in particular that of the SSB, to facilitate network energy savings, on the other hand network implementation complexity and measurement gap scheduling restrictions are incurred.

5 [0036] Network implementation complexity stems from the fact that the measurement gaps and the target cells to be measured within a measurement gap need to be synchronized, as discussed above. A basic assumption may be that an SSB is provided once every 20 ms, or indeed longer, and thus the network will no longer be able to allocate measurement gaps evenly in time, as was the case in LTE, since they need to align in time with SSB 10 transmissions. When many UEs need to share the same measurement gaps, significant scheduling restrictions at the base station are incurred as no traffic can be scheduled from/to those UE during the measurement gaps. This is illustrated in FIGURE 2A.

[0037] FIGURE 2A illustrates signal timing in accordance with at least some embodiments of the present invention. Time axes 201 and 202 correspond to two LTE cells 15 and time axes 203 and 204 correspond to two NR cells. The LTE cells transmit synchronization signal blocks 210 comprising PSS, SSS and CRS every 5 ms. The NR cells transmit NR SSBs 220 at a 20ms periodicity. As can be seen, in NR measurement gaps cannot be allocated as evenly in time as in LTE. If all UEs are allocated with the same gap pattern, the network cannot schedule any UEs during that time since they are all measuring, 20 which leads to inefficient network operation. The problem may become even more pronounced in 6G, as it is envisioned that SSB transmission in 6G may be less frequent than in NR. Furthermore the issue of less frequent SSB transmission (e.g. compared to NR) may limit the measurement occasions in which the UEs are able to perform intra-cell measurements (e.g. for beam management, beam switching) or inter-cell measurements for handover/cell switch/mobility purposes.

[0038] To alleviate this problem, a measurement signal may be transmitted in addition to an SSB for cell detection and measurement. Such a measurement signal that has at least some of the following characteristics: firstly, its characteristics include a characteristic equivalent to a characteristic of a signal used for cell measurement, such as SSS within SSB. The measurement signal may be a replica of the SSS, for example. Secondly, the measurement signal may encode same information bits, or may be generated based on same information, as are used to generate one or more parts of the SSB. For example, the measurement signal may encode, or be generated based on, the sequence identity or sequence parameters used in generating the SSS. Thirdly, the measurement signal may have a configurable time periodicity. This time periodicity may be equal to or higher than a corresponding SSB periodicity, in other words, the measurement signal may be transmitted as often as the SSB, or more often than the associated SSB. The time periodicity of the measurement signal may be a fraction of associated SSB periodicity, such that the SSB time period is divided by N, where N = { 1,2, 3, 4,...}. In some embodiments, all three of the characteristics mentioned above are present in the measurement signal. The measurement signal may be associated with an SSB in that the measurement signal has a same sequence, sequence identity or sequence parameter of an SSS comprised in the corresponding SSB with which the measurement signal is associated.

[0039] A time repetition type of a measurement signal resource may be periodic, semi- persistent or aperiodic. When periodic, the period may be constant, such as 5 or 10 ms, for example. When aperiodic, the measurement signal may be triggered without repetition as a response to a condition being fulfilled, or to a set of conditions each being fulfilled. The aperiodic measurement signal may be provided as a single transmission as a response to the condition(s) being fulfilled.

[0040] The measurement signal time periodicity may be cell- and/or carrier frequency-specific. In any case, the measurement signal time periodicity may be signaled to the UE or implicitly determined by the UE, for example from a known measurement signal for the carrier frequency. The measurement signal time periodicity may be linked to an additional configurable time offset with respect to the SSB transmission occasion(s). One way of informing the UE of measurement signal time periodicity is to configure the UE to perform a measurement at this time periodicity.

[0041] For resource allocation for measurement signal transmission, there are several options. Firstly, the measurement signal may be located on a common resource block grid while the SSB’s frequency domain location is according to the synchronization raster. The measurement signal may be located in frequency domain, for example, by maximizing frequency domain overlap with the associated SSB. A benefit of this is that the measurements conducted using the measurement signal will then approximate well measurements conducted using the SSB. In a second option, the measurement signal and the SSB are located on the same center carrier frequency, for example as defined by the synchronization raster or a specific raster implicitly or explicitly defined for the measurement signal. In a third option, the measurement signal is located on frequency resources according to a configurable frequency domain offset with respect to the SSB, such as with respect to SSB center frequency or another SSB reference point in frequency domain. There may be more than one measurement signal allocated on a carrier according to the first option or in accordance with a separate configuration. Furthermore, the measurement signal and the associated SSB (or the SSS of the SSB) may occupy same number of PRBs (physical resource blocks or subcarriers), and/or occupy same bandwidth.

[0042] The measurement signal may be associated with another reference signal or the SSB. For example, there may be as many different measurement signals as there are different SSBs, for a one-to-one mapping between SSBs and measurement signals, that is, each transmitted measurement signal has a corresponding SSB, or SSB type, that is transmitted. A measurement signal sequence may be associated one-to-one with a sequence of SSBs. Alternatively, the set of one or more SSBs may have an associated measurement signal transmitted, that is, it may be configurable whether the measurement signal corresponding to specific SSB or a set of SSB is transmitted or not.

[0043] The network may be configured to abstain from measurement signal transmission if it would be allocated in the same half-frame as a corresponding SSB. The measurement signal would be unnecessary in that case, since providing the measurement signal in such a half-frame would not materially enhance the flexibility at which measurement gaps can be configured. When the measurement signal is transmitted, it may be located in the same slot and in the same symbol as the SSS of the corresponding SSB in the 5m half-frame where the measurement signal is allocated. In other words, the measurement signal may be in a same location in a half-frame as the SSB is in the halfframes where an SSB is transmitted.

[0044] The network is configured to allocate time and frequency resources for transmission of measurement signals explicitly, that is, via common and/or dedicated signaling, or implicitly, for example based on a known reference measurement signal. The measurement signal symbol locations or mapping to transmission occasions may be broadcasted, for example in system information or based on known offsets, such as encoded by the measurement signal sequence itself.

[0045] FIGURE 2B illustrates signal timing in accordance with at least some embodiments of the present invention. This figure shows a principle for measurement signal allocation by having the same slot and symbol position as the associated SSB in a respective half-frame. Time periodicity for measurement signal transmission may be 5, 10 or 20 ms in the example. The half-frame could be the same as for the SSB burst in respective radio frame or different half-frame. If different, then measurement signals can be allocated also in the same radio frame as SSB burst.

[0046] Frame sequence 230 comprises, in this example, frames zero through 15. The frames marked with a cross, X, are ones in which an SSS is transmitted from the network. Slot sequence 240 represents slots of frame 0 from frame sequence 230. Again, the slots in which SSS is transmitted are marked with a cross, X. Symbol sequence 250 represents the symbols of slot 0 of slot sequence 240. Here symbols where SSS is transmitted are marked with the cross. Further, an SSB comprising the SSS, PSS and PBCH is provided twice in this slot, first SSB #0 in symbols 2 - 5 and then SSB #1 in symbols 8 - 11. In other words, sequences 230, 240 and 250 represent a case when an SSB is sent.

[0047] Slot sequence 260 represents slots where the measurement signal is sent. Here slots with the measurement signal are marked with the cross. In symbol sequence 270, representing symbols of slot 0 of slot sequence 260, the measurement signal 280 is sent in symbols 4 and 10, corresponding to the symbols in which the SSS is sent in symbol sequence 250. Measurement signal 280 in symbol 4 is associated with and corresponds to SSB #0 and measurement signal 280 in symbol 10 is associated with and corresponds to SSB #1. In other words, UEs can find the measurement signal in this example case in the same symbols as where the SSS is sent in case SSB is transmitted. Indeed, the measurement signal may be a replica of the SSS, possibly on the same or different frequency resources, thus enabling its use for same purposes as the SSS in SSB. Further, the SSB is not sent in a slot where the measurement signal is sent.

[0048] FIGURE 2C illustrates signal timing in accordance with at least some embodiments of the present invention. Here sequences 230, 240 and 250 are the same ones as sequences 230, 240 and 250 in FIGURE 2B. In the resource allocation example FIGURE 2C the measurement signals are allocated in a compact manner. In detail, in this example symbols sequence 295 of slot 0 of slot sequence 290 comprises eight measurement signals {a, b, c, d, e, f, g, h] which correspond to eight SSBs (of which only two are shown in slot 250), respectively. As in the case of FIGURE 2B, each one of these measurement signals is sent in a single symbol. Again, no SSB is sent in a slot where a measurement signal is sent.

[0049] The allocation scheme of FIGURE 2C may be beneficial from a network energy saving point of view. Also, a maximum number of measurement signals per slot may be defined, for example four. In such a case in the FIGURE 2C allocation mechanism, there may be two consecutive DL slots where measurement signals are allocated assuming eight SSBs and corresponding MSSs. These slots could be slots 0 and 1 of slot sequence 290, for example.

[0050] FIGURE 2D is a flow diagram of UE behavior in accordance with at least some embodiments of the present invention. The process begins in phase 2100, where the UE receives a configuration of measurement signals, either from system information broadcasted in a cell, or from dedicated signaling. An example of dedicated signaling is radio resource control, RRC, signaling. The measurement signal configuration comprises an indication of when and on what resources the measurement signal(s) will be transmitted.

[0051] In phase 2110, the UE determines an association between each measurement signal and a corresponding SSB. This association may comprise that the measurement signal has a same sequence, sequence identity or sequence parameter of an SSS comprised in the corresponding SSB with which the measurement signal is associated Subsequently, in phase 2120, the UE determines time and frequency resources that will be used to convey the measurement signal. In phase 2130, which may take place before or after phase 2120, the UE determines time and frequency synchronization for measurement signal reception, based on information concerning the associated SSB. Finally in phase 2140, using the time and frequency synchronization, the UE measures an SSB and at least one occasion of a measurement signal associated with the SSB.

[0052] Overall, the measurement signal as herein described alleviates network implementation complexity by not requiring as stringent synchronization as in NR networks. Further, the measurement signal reduces scheduling restrictions as UEs can be configured to have different measurement gaps in time domain, and finally, the measurement signal can be switched on and off by the network. Furthermore, the measurement signal improves network energy efficiency since it may be more flexibly (or in more flexible manner configured) transmitted (that is, aperiodically, in a semi-persistent manner, or even periodically) and switched off when desired. Additionally such a signal may improve the UE energy efficiency (that is, reduce the power consumption) since the UEs may schedule their measurements for different purposes (e.g. beam management / mobility measurements) in more flexible a manner.

[0053] In general, a UE may be configured to receive first configuration information indicative of a measurement to be performed on a carrier, receive (or detect) a measurement signal transmitted over the carrier, and perform the measurement based on the received (or detected) measurement signal and according to the first configuration information. The measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and the measurement signal is transmitted by the network in a slot that does not comprise the SSB. The first configuration information may identify time and frequency resources of e.g. a neighboring cell that the UE is to measure. The measurement may be a mobility measurement. The measurement signal may comprise a part or segment of the SSB, but the measurement signal is not a repetition of the entire associated SSB. The measurement signal may comprise a proper subset of signals comprised in the SSB, that is, the measurement signal may comprise one of the signals in the SSB or some of the signals in the SSB, but not all of the signals in the SSB. Thus, the slot where the measurement signal is transmitted does not comprise the SSB, although the measurement signal may be a replica of a part of an SSB.

[0054] The measurement signal being associated with the SSB may comprise that the measurement signal is generated based on a binary sequence, the binary sequence being based on one or more of at least one first parameter used to generate the SSS, such as NJ_D (2 or 1V_ID , or at least one second parameter used to generate a demodulation reference signal, DMRS, of the PBCH. Examples of the second parameter are a cell identity and an SSB index.

[0055] In general, a base station is configured to repeatedly broadcast, over an air interface, a sequence SSBs, referred to above as SSB burst. The base station further transmits, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

[0056] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 300, which may comprise, for example, a mobile communication device such as UE 110 or, in applicable parts, a base station of FIGURE 1. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. When processor 310 comprises more than one processor, device 300 may be a distributed device wherein processing of tasks takes place in more than one physical unit. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. A processing core or processor may be, or may comprise, at least one qubit. Processor 310 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise at least one field- programmable gate array, FPGA. Processor 310, optionally together with memory and computer instructions, may be means for performing method steps in device 300, such as receiving, detecting, performing, broadcasting or transmitting. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0057] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. 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 analogue and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analogue 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 UE or base station, 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.

[0058] This definition of circuitry applies to all uses of this term in this application, including in any claims. 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.

[0059] Device 300 may comprise memory 320. Memory 320 may comprise randomaccess memory and/or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may be a computer readable medium. Memory 320 may comprise solid- state, magnetic, optical and/or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part external to device 300 but accessible to device 300. Memory 320 may be transitory or non-transitory. The term “non-transitory”, as used herein, is a limitation of the medium itself (that is, tangible, not a signal) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM). [0060] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and/or receiver 340 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, 5G, long term evolution, LTE, IS-95, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0061] Device 300 may comprise a near-field communication, NFC, transceiver 350. NFC transceiver 350 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0062] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker or a microphone. A user may be able to operate device 300 via UI 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 or on a cloud accessible via transmitter 330 and receiver 340, or via NFC transceiver 350, and/or to play games.

[0063] Device 300 may comprise or be arranged to accept a user identity module 370. User identity module 370 may comprise, for example, a subscriber identity module, SIM, card installable in device 300. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and/or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0064] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0065] Device 300 may comprise further devices not illustrated in FIGURE 3. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the frontfacing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some embodiments, device 300 lacks at least one device described above. For example, some devices 300 may lack a NFC transceiver 350 and/or user identity module 370.

[0066] Processor 310, memory 320, transmitter 330, receiver 340, NFC transceiver 350, UI 360 and/or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0067] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, base station 130 110, in the centre, UE 110, and on the right, base station 135, all of FIGURE 1. Time advances from the top toward the bottom.

[0068] During phase 410, UE 110 is attached in a cell controlled by base station 130 with an active protocol connection thereto. In phase 420, base station 130 configures UE 110 with a measurement configuration and a measurement gap configuration, which correspond to measurement signal transmission time periodicity from base station 135. This time periodicity is configured into base stations 130, 135 by the core network, for example. [0069] During measurement gaps 450, UE 110 measures the measurement signal transmitted by base station 135 in phases 430, 440. As is evident from the figure, gaps 450 coincide with the measurement signal transmissions 430, 440. In phase 460, UE 110 reports results of the measurement to base station 130. Base station 130 may use the information reported in phase 460 in making a handover decision, for example, wherein UE 110 is triggered to handover to a cell controlled by base station 135.

[0070] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in UE 110, for example, or in a control device configured to control the functioning thereof, when installed therein.

[0071] Phase 510 comprises receiving first configuration information indicative of a measurement to be performed on a carrier. Phase 520 comprises receiving a measurement signal transmitted over the carrier. Phase 530 comprises performing the measurement based on the received measurement signal and according to the first configuration information. The measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and the measurement signal is transmitted in a slot that does not comprise the SSB.

[0072] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in base station 135, for example, or in a control device configured to control the functioning thereof, when installed therein.

[0073] Phase 610 comprises repeatedly broadcasting, over an air interface, a sequence of synchronization signal blocks, SSBs. Phase 620 comprises transmitting, over the air interface, a sequence of measurement signals for measurement by terminal devices. The sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

[0074] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0075] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0076] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0077] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0078] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0079] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

[0080] 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.

INDUSTRIAL APPLICABILITY

[0081] At least some embodiments of the present invention find industrial application in running wireless communication networks.

ACRONYMS LIST

3 GPP 3^rd generation partnership project

5G fifth generation (5G)

6G sixth generation

BWP bandwidth part

DL downlink

DMRS demodulation reference signal

E-UTRA evolved UMTS terrestrial radio access

FR frequency range

LTE long term evolution (4G)

NR new radio

PBCH physical broadcast channel

PSS primary synchronization signal

SCS subcarrier spacing

SSB synchronization signal block

SMTC SS/PBCH block measurement timing configuration

SSS secondary synchronization signal

UE user equipment UL uplink

REFERENCE SIGNS LIST

Claims

CLAIMS:

1. An apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:

- receive first configuration information indicative of a measurement to be performed on a carrier;

- receive a measurement signal transmitted over the carrier; and

- perform the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

2. The apparatus according to claim 1, wherein the SSB comprises a primary synchronization signal, PSS, a secondary synchronization signal, SSS, and a physical broadcast channel, PBCH.

3. The apparatus according to claim 2, wherein the measurement signal being associated with the SSB comprises that the measurement signal is generated based on a binary sequence, and wherein the binary sequence is based on one or more of:

- at least one first parameter used to generate the SSS; or

- at least one second parameter used to generate a demodulation reference signal, DMRS, of the PBCH.

4. The apparatus according to claim 2 or 3, wherein the measurement signal is a replica of the SSS.

5. The apparatus according to any of claims 1 to 4, wherein the measurement signal is transmitted with a first time periodicity that is equal to or lower than a second time periodicity with which the SSB is repeatedly broadcasted.

6. The apparatus according to claim 5, wherein the first time periodicity is a fraction of the second time periodicity.

7. The apparatus according to any of claim 1 to 6, further caused to receive second configuration information indicative of a measurement gap, and to perform the receiving of the measurement signal during the measurement gap.

8. The apparatus according to claim 7, wherein at least one of the first configuration information and the second configuration information is based on timing information of the measurement signal.

9. The apparatus according to any of claims 1 to 8, wherein the measurement is one of

- an inter-radio access technology measurement;

- an inter-frequency measurement; or

- an intra-frequency measurement.

10. The apparatus according to any of claims 1 to 9, wherein the apparatus is further caused to perform the receiving of the measurement signal on same frequency resources as the SSB, or on different frequency resources than the SSB.

11. The apparatus according to any of claims 1 to 10, wherein the measurement is a mobility measurement, and wherein the apparatus is further caused to report to a network a result of the mobility measurement.

12. The apparatus according to claim 11, wherein the apparatus is further caused to receive the SSB and to use the received measurement signal in performing the mobility measurement.

13. An apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:

- repeatedly broadcast, over an air interface, a sequence of synchronization signal blocks, SSBs; and - transmit, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.

14. The apparatus according to claim 13, wherein each SSB of the sequence of SSBs comprises a primary synchronization signal, PSS, a secondary synchronization signal, SSS, and a physical broadcast channel, PBCH.

15. The apparatus according to claim 14, wherein the apparatus is further caused to generate each measurement signal of the sequence of measurement signals based on a binary sequence, and wherein the binary sequence is based on one or more of:

- at least one first parameter used to generate an SSS of an SSB associated with the measurement signal; or

- at least one second parameter used to generate a demodulation reference signal, DMRS, of a PBCH of an SSB associated with the measurement signal.

16. The apparatus according to claim 14 or 15, wherein the sequence of measurement signals are replicas of SSSs of the sequence of SSBs.

17. The apparatus according to any of claims 13 to 16, wherein the apparatus is further caused to perform the transmission of the sequence of measurement signals with a first time periodicity that is equal to or lower than a second time periodicity with which the sequence of SSBs is repeatedly broadcasted.

18. The apparatus according to claim 17, wherein the first time periodicity is a fraction of the second time periodicity.

19. The apparatus according to any of claims 13 to 18, wherein the apparatus is further caused to perform the transmitting of the sequence of measurement signals on same frequency resources as the broadcasting of the sequence of SSBs, or on different frequency resources than the broadcasting of the sequence of SSBs.

20. A method comprising:

- receiving first configuration information indicative of a measurement to be performed on a carrier;

- receiving a measurement signal transmitted over the carrier; and

- performing the measurement based on the received measurement signal and according to the first configuration information, wherein the measurement signal is associated with a synchronization signal block, SSB, that is repeatedly broadcasted over the carrier, and wherein the measurement signal is transmitted in a slot that does not comprise the SSB.

21. A method, comprising:

- repeatedly broadcasting, over an air interface, a sequence of synchronization signal blocks, SSBs; and

- transmitting, over the air interface, a sequence of measurement signals for measurement by terminal devices, wherein the sequence of measurement signals is in one-to-one association with the sequence of SSBs, and wherein the sequence of measurement signals is transmitted in one or more slots that do not comprise the SSBs.