Superimposed pilot signals

Abstract

According to an example aspect of the present invention, there is provided an apparatus configured to transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals, receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network, and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

Description

PILOT SIGNALSFIELD

[0001] The present disclosure relates to wireless communications, such as cellular communications.BACKGROUND

[0002] To enable successful communication between a user equipment, UE, and a network, the UE synchronizes with the network in terms of time and frequency. For example, a synchronization signal block may be broadcasted by base stations of a radio-access network to enable UEs to obtain an initial time and frequency synchronization to facilitate a connection attempt, for example by a random access process. Time synchronization errors may occur due to mismatches in sampling frequency between the transmitter and receiver, or a time offset due to a transmission delay. To achieve time synchronization, time offset, TO, is estimated in the time-domain, for example before fast-Fourier transform, FFT, of the received signal if such is used.

[0003] Lack of frequency synchronization may be due to the errors of the receive and transmit-side oscillators which cause a frequency offset, FO, and this manifests as a linear phase offset that may lead to inter-carrier interference. To estimate the TO and FO, the receiver may measure synchronization signals, for example cell specific synchronization signals.SUMMARY

[0004] 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.

[0005] 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, from a network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, determine whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals, and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmit to the network an indication of a synchronization update failure.

[0006] 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 transmit, to a user equipment, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, receive, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmit, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.

[0007] According to a third aspect of the present disclosure, there is provided a method comprising receiving, from a network and in an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, determining whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals; and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmitting to the network an indication of a synchronization update failure.

[0008] According to a fourth aspect of the present disclosure, there is provided a method comprising transmitting, to a user equipment and from an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, receiving, from the user equipment, an indicationof a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmitting, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.

[0009] According to a fifth aspect of the present disclosure, there is provided an apparatus comprising means for receiving, from a network and in an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, determining whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals; and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmitting to the network an indication of a synchronization update failure.

[0010] According to a sixth aspect of the present disclosure, there is provided an apparatus comprising means for transmitting, to a user equipment and from an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, receiving, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmitting, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.

[0011] 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, from a network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, determine whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals, and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmit to the network an indication of a synchronization update failure.

[0012] 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 leasttransmit, to a user equipment, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration, receive, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmit, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.

[0013] According to a ninth 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 transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals, receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network, and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

[0014] According to a tenth 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, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals, determine and transmit to the user equipment a first pilot configuration, and transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

[0015] According to an eleventh aspect of the present disclosure, there is provided a method comprising transmitting, to a network and from an apparatus, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals, receiving, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network, and updating a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

[0016] According to a twelfth aspect of the present disclosure, there is provided a method, comprising receiving, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals, determining and transmitting to the user equipment a first pilot configuration, and transmitting to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

[0017] According to a thirteenth aspect of the present disclosure, there is provided an apparatus comprising means for transmitting, to a network and from an apparatus, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals, receiving, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network, and updating a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

[0018] According to a fourteenth aspect of the present disclosure, there is provided an apparatus comprising means for receiving, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals, determining and transmitting to the user equipment a first pilot configuration, and transmitting to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

[0019] According to a fifteenth 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 transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals, receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network, and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

[0020] According to a sixteenth 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, from a user equipment, a message indicating that the user equipment supportswireless transmissions comprising superimposed pilot signals, determine and transmit to the user equipment a first pilot configuration, and transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention;

[0022] FIGURE 2A illustrates regular pilot use;

[0023] FIGURE 2B illustrates superimposed pilot use;

[0024] FIGURE 2C illustrates superimposed pilot use;

[0025] FIGURE 2D illustrates superimposed pilot use;

[0026] FIGURE 2E illustrates an example neural receiver in accordance with at least some embodiments of the present invention;

[0027] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0028] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention;

[0029] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention;

[0030] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention;

[0031] FIGURE 7 is a flow graph of a method in accordance with at least some embodiments of the present invention;

[0032] FIGURE 8 is a flow graph of a method in accordance with at least some embodiments of the present invention, and

[0033] FIGURE 9 is a flow graph of a method in accordance with at least some embodiments of the present invention.EMBODIMENTS

[0034] Disclosed herein are methods to use superimposed pilots in synchronization of a UE to the network. Thus the superimposed pilots may perform two roles, namely support reception in terms of channel estimation or equalisation, and also maintaining synchronization in terms of updating the TO and / or FO. In some embodiments, this enables omission of tracking reference signals sent from the base station, separate from the superimposed pilots, as the tracking reference signals, TRS would otherwise be used to maintain synchronization. In case of errors in updating the TO and / or FO using the superimposed pilots, the network may respond by increasing the pilot-to-data power ratio in superimposed pilots, include the superimposed pilots in more resource elements of a transmission, add TRS to the superimposed pilots, or switch to non-superimposed pilot symbols and use of TRS for synchronization.

[0035] 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.

[0036] Base station 130 is further coupled communicatively with core network node 140, which may comprise, for example, an evolved packet core, EPC, comprising a mobility management entity, MME, a home subscriber server, HSS, etc, or a 5G core network comprising an access and mobility management function, AMF, a 5G unified data repository, UDR, a call session management function, SMF, etc. The core network node 140 may be coupled with further core network nodes, and with a network 150, which maycomprise 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 physical 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 3rdgeneration partnership project, 3GPP. To obtain interoperation, UEs attaching to the network are configured to support a same standard as the network.

[0037] Base station 130 controls, 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, in the example of FIGURE 1, cells 135A and 135B. The number of cells and / 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.

[0038] Base stations, BS, such as base stations 130 and 135, are configured to transmit various kinds of information to UEs. In addition to payload, such as the content of voice and video calls, application data and transferred user files, base stations transmit various kinds of configuration information to control the functioning of UEs in their cells. This configuration information includes grants to use air interface resources for UL and DL, for example. Cell specific synchronization signals, provided in a synchronization signal block, may comprise primary and secondary synchronization signals, PSS and SSS, which may be defined as gold sequences. In time synchronization, when the time offset, TO, is larger than a cyclic prefix, CP, length, the receiver may end up misaligning of the FFT window which causes inter-symbol, ISI, and intercarrier, ICI, interference. Conversely, if the time offset is smaller than the CP duration, the receiver experiences a phase offset.

[0039] By a pilot symbol, it is meant a reference symbol, known to the receiver, generated based on a pilot constellation and / or a pilot sequence. By a data symbol, it is meant symbols unknown to the receiver, generated based on a data constellation and a data sequence that is to be transmitted to the receiver. By a superimposed, SI, symbol, it is meant a superimposition of pilot and data symbols, that is, a pilot symbol is laid over a data symbol at a power ratio. By a superimposed pilot, SIP, symbol, it is meant a pilot part of an SI symbol. By a superimposed data, SID, symbol, it is meant a data part of an SI symbol. By a SIP transmission, it is meant transmitting pilot and data over the same resource elements, and by a SIP configuration, it is meant configuration information for transmitting or receiving in SIP transmission. In general, a pilot configuration which configures use of superimposed pilots is a SIP configuration. In the present disclosure, superimposed pilot signals, which comprise superimposed pilot symbols, are referred to as superimposed pilots.

[0040] When using superimposed pilots, a transmission where an OFDM symbol consists of N modulation symbols, each modulation symbol n being either an SI symbol or a data symbol:

[0041] where xdis a data symbol, xpis a pilot symbol, adis a power scaling parameter for the data part of the SP symbol, apis a power scaling parameter for the pilot part of the SP symbol, Sssc-spis the set of RE indices occupied by SP symbols, and Sdis the set of RE indices occupied by pure data symbols. This transmission from the base station may be used by the UE to jointly perform synchronization and data detection.

[0042] To ensure accurate channel estimation, which is paramount to successful data reception, 5G and earlier systems rely on the use pilot signals which are separate from the data transmission and are ideally orthogonalized among users. The pilot signals may be demodulation reference signals, DMRS, for example. This approach is called a regular pilot, RP, approach. Although the regular pilot approach allows the receiver to estimate the channel accurately, it has two drawbacks. Firstly, when the number of users exceeds the number of pilot sequences and different users are being configured with the same pilot sequence, pilot contamination arises. Secondly, pilot insertion leads to a reduction of spectral efficiency since a portion of the time-frequency resources is allocated to pilot transmission.

[0043] To address these challenges, two approaches are proposed in the literature, namely pilotless transmission and superimposed pilot transmission. In the pilotless transmission scheme, all transmission power and resource elements are allocated to data transmission, resulting in higher spectral efficiency than the RP scheme. However, pilotless transmission presents challenges for receiver algorithms to obtain the channel state in the absence of pilots. In superimposed pilot transmission scheme, data is transmitted in all available resource elements, REs, as in pilotless transmission. However, some power in either all or only some of the REs is also allocated to the known pilot signal components to assist channel estimation at the receiver. In practice, the proportion of overall power dedicated to pilots in a superimposed pilot-based transmission may be smaller than or similar to that in the RP scheme, for example about 5%. Gains in communication efficiency may be obtained in the superimposed pilot scheme, compared to the RP scheme, depending on characteristics of the wireless channel and the signal-to-noise, SNR, regime that is used. Also in the superimposed pilot scheme the pilot signal may be a DMRS.

[0044] FIGURE 2A illustrates regular pilot use. On the vertical axis is time, denoted as orthogonal frequency division multiplexing, OFDM, symbol durations and the vertical axis is a frequency axis where frequency is denoted in terms of subcarriers of the OFDM transmission. A square resource element is the time duration of one OFDM symbol on a single subcarrier, and pilot REs are arranged in the overall transmission as illustrated to arrive at one example of the RP transmission scheme.

[0045] FIGURE 2B illustrates superimposed pilot use. The axes are similar as in FIGURE 2A. Here all the REs of the transmission are used to convey the superimposed pilot signals, the power ratio between pilot and data symbols being configurable by the network to respond to, for example, fading in the channel or changes in a speed at which the UE moves in the coverage area of the network.

[0046] FIGURE 2C illustrates superimposed pilot use. The axes are similar as in FIGURE 2 A. In the case of FIGURE 2C, superimposed pilots signals are present in some, but not all, of the REs of the transmission, as illustrated. Here too, as in FIGURE 2B, using the superimposed pilots enables sending data in all REs. The power ratio between pilot and data symbols is configurable by the network, as in FIGURE 2B. The subset of REs which carry the superimposed pilots may also be configurable by the network, to respond to different channel conditions or application data requirements, for example. When thenetwork reconfigures the set of REs to carry the superimposed pilots as being all the REs of the transmission, the system will switch from the case of FIGURE 2C to that of FIGURE 2B. The network may also switch the system from the case of FIGURE 2B to that of FIGURE 2C by reconfiguring the set of REs to carry the superimposed pilots.

[0047] FIGURE 2D illustrates superimposed pilot use. The axes are similar as in FIGURE 2A. The case of FIGURE 2D is one where some REs carry superimposed pilots while other REs only carry data, and further some REs carry TRS and no data, to facilitate updating of frequency and time synchronization. In the case of FIGURE 2D, synchronization updating may be based on both the superimposed pilots and the TRS.

[0048] FIGURE 2E illustrates an example neural receiver in accordance with at least some embodiments of the present invention. Transmitters using deep learning that leam a new UE-specific constellation shaped to maximize the link performance have been popularized in the last years in both academia and industry.

[0049] Since 6G is expected to natively support machine learning, deep waveform learning and deep constellation learning have been proposed for use in physical layer features that make the 6G design depart from the OFDM-based design of 5G. To facilitate synchronization using superimposed pilot signals, the UE may use a neural receiver to estimate the time and frequency synchronization offsets. The downlink signal is received, distorted by the wireless channel, and demodulated using OFDM or discrete Fourier transform-spread OFDM, DFT-S-OFDM, processing and provided to a resource element demapping phase. The received signals obtained from resource de-mapping, and the pilot sequence based on a received configuration from the base station, are fed to the neural receiver along with the data and pilot constellation, and the neural receiver may be configured to responsively output not only estimated downlink data bits but also estimated time and frequency synchronization offsets, TO and FO. FIGURE 2E is a block diagram of such a UE receiver. The neural receiver itself may be based on different architectures, for example it may be based on convolutional neural networks, CNNs, residual neural networks, ResNets, or transformers.

[0050] To optimize the trainable parameters of the neural receiver with respect to both synchronization and data detection objectives, a loss function comprising a summation of two terms is proposed: firstly a mean squared error, MSE, function of the true and estimatedsynchronization offsets, and secondly the cross entropy, CE, function over the transmitted and estimated bits. An example of such a loss function £ is

[0051] where T 0 and FO denote the true time and frequency synchronization offset, respectively and eT 0 and eFO the estimated values for these. Here, b^ and b^ denote the transmitted bit and the transmitter and receiver, respectively. To control the impact of synchronization terms, pTand pFare used as normalization factors for the MSE terms of time and frequency offsets, respectively. Also, CE is the cross entropy between the transmitted bit and estimated bit at the receiver, averaged over all the data resource elements in the resource grid D and all the B bits in each symbol.

[0052] During a data collection phase, the UE may obtain accurate estimates of TO and FO based on a synchronization signal block broadcast by the base station. Alternatively, the UE may define a set of possible TO and FO values and search over all the TO and FO combinations to find the true values. The accurate estimate of TO and FO of the first approach or found TO and FO by the second approach can be used as labels for synchronization outputs during training phase. Training or fine-tuning may be performed after the data collection phase. The training may be conducted in the UE or in a cloud environment, where training using cloud requires data sharing from a UE, or plural UEs, to the cloud environment. After training, model sharing may be done from the cloud environment to the UE.

[0053] Furthermore, to obtain the ground truth valuesat the UE, the base station and the UE may coordinate to use a pseudo-random generator for bit generation, and the base station may configure a seed value for generating synthetic bits. For label collection based on simulation data, if the UE decides to deploy a previously trained neural receiver based on simulation data, label collection is simple as the true values of all the parameters are available in simulators. Training data for initializing a neural receiver may be generated using a link-level simulator which simulates data modulation and transmission in the transmitter end, effects of the radio channel, and data demodulation and reception by a receiver. In a simulator, transmitted bits may be stored and used for training as true labels.Further, in a simulator when the synchronization offset is considered, the exact value of the offset is known and can be stored as labels.

[0054] In 5G systems, a UE must synchronize to the base station prior to establishing data communications with the base station. This initial synchronization is a separate procedure that consists of the base station broadcasting a synchronization signal block, comprising primary synchronization signal PSS and secondary synchronization signal SSS. The UE uses the signals of the synchronization signal block to obtain a cell identifier and obtain initial estimates of the TO and FO.

[0055] Once the TO and FO estimates are available, the UE compensates for these offsets while receiving and transmitting data signals. The synchronization is updated periodically, in 5G, using TRS to ensure that the UE remains synchronized to the network. If synchronization update using TRS fails and synchronization using the synchronization signal block has to be performed again, the procedure becomes spectrally inefficient for the UE, as the UE must interrupt its data traffic to switch to the bandwidth part where the synchronization signal block is allocated.

[0056] Procedures are herein disclosed in which superimposed pilot symbols are used to maintain time and frequency synchronization while simultaneously receiving data signals. This enables avoiding forcing the UE to interrupt its data link to switch BWPs and perform SSB measurement and, optionally also allowing the network to abstain from sending TRS. Optionally, a neural receiver is used to perform the updating of the synchronization based on the superimposed pilot symbols.

[0057] The UE may inform the base station whether it supports superimposed pilot symbol-based synchronization. The UE may also communicate to the base station a preference or requirement concerning use of superimposed pilots, for example in terms of a minimum or preferred set of requirements for simultaneous synchronization and communications support. For example, this set of requirements may comprise a minimum bandwidth, and a minimum ratio for pilot to data power per symbol consisting of a pilot symbol superimposed onto a data symbol, where the pilot to data symbol power ratio may be configurable. This ratio may be expressed as rP min= — .'ad

[0058] The set of minimum requirements may further comprise a minimum ratio between the pilot density and data density, assuming that the data transmission may becomposed of a combination of pure data symbols and superimposed symbols. This density thus determines how large a proportion of the REs of the transmission carry superimposed pilots. This density may be expressed as rD minThe indication of support and,optionally, also the preference or requirement concerning use of superimposed pilots, may be communicated during a random access process, as part of UE capability information exchange, or using RRC signaling, for example.

[0059] The base station determines a pilot configuration for the superimposed pilot use, and sends this pilot configuration to the UE which supports use of superimposed pilots. The pilot configuration may comprise, for example, the values for one or more of ap(n), xp(n), ad(n), xd(n), n E SjSC, xd(k), k E Sdand defining the sets Sjsc, Sd. In some embodiments, all of these parameters are comprised in the pilot configuration. If one or more of these parameters are set in network-wide configuration or an industry standard, then the base station need not include it, or them, in the pilot configuration.

[0060] The base station may also request the UE for feedback regarding the outcome of the superimposed pilot-based synchronization updating. The base station may use this feedback to adjust the pilot configuration for a subsequent transmission. The feedback may be conveyed as part of an enhanced channel quality indicator, CQI, feedback and may be defined as a first binary indicator T-failure for the success of the time synchronization and a second binary indicator F-failure for the success of the frequency synchronization. In another embodiment, the UE may provide as the feedback indications as to the values of TO and FO as determined using the superimposed pilots. For example, the UE may communicate to the base station a TO index a, and FO index b, where a =, where Ts and fs are the sampling time and subcarrier spacing of the system, yt and yf are the time and frequency sampling coefficients, and eTO and eFO are the estimated TO and FO respectively.

[0061] As noted above, the UE may use a neural receiver to process the transmission for simultaneous communication and synchronization. The neural receiver may jointly estimate TO and FO (that is, compute eTO, eFO or directly a and b) using the superimposed pilots and derive T-failure and F-failure, and compensate for eTO, eFO, or directly for a and b, while decoding the data part of the transmission. The UE may send an enhanced CQI feedback where it includes T-failure and F-failure, a and b or eTO and eFO. In otherembodiments, an analytical process is used instead of a neural receiver to obtain the data and pilot symbols from the REs with superimposed data and pilot symbols.

[0062] Synchronization based on superimposed pilot signals may comprise updating of an initial synchronization performed using a synchronization signal block, or an independent synchronization only from the received superimposed pilot signals, for example for high mobility UEs. The UE may perform the updating of the synchronization at each slot, or every n slots, with n being an integer such as 2, 5 or 10, for example. In case the UE cannot perform the synchronization updating properly or if the UE detects degradation in synchronization updating performance, the UE may inform the base station of the problem. In response to such an error report, the base station may update the pilot configuration based on the received T-failure and / or F-failure or other feedback by at least one of the following: changing the pilot sequence of superimposed pilots (e.g., by changing the seed of a pseudorandom sequence generator), increasing the ratio pilot vs data power, increasing the ratio pilot vs data density in time and / or frequency, increasing the use of TRS, and increasing the bandwidth. The updated pilot configuration may be provided to the UE and used in subsequent transmissions. This error reporting process will be discussed in more detail in connection with FIGURE 4.

[0063] 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, base station 130 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 andcomputer instructions, may be means for performing method steps in device 300, such as receiving, determining and transmitting. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0064] 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 memoiy(ies) that work together to cause an apparatus, such as a user equipment 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.

[0065] 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.

[0066] 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 processor310 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).

[0067] 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, 6G, IS-95, wireless local area network, WLAN, Ethernet and / or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, a base station, and on the right, a UE. Time advances from the top toward the bottom.

[0075] In phase 410, the UE, having completed initial synchronization as to time and frequency using the broadcasted synchronization signal block, provides to the base stationan indication that the UE supports using superimposed pilots for updating synchronization, in other words, simultaneous synchronization and communication. This message, which may be part of a random access process as part of UE capability information exchange, or RRC signaling, for example, may also comprise the preferred or required set of parameters for simultaneous synchronization and communications support. This message may be conveyed without using superimposed pilots.

[0076] Responsive to the message of phase 410, the base station determines a first pilot configuration indicating use of superimposed pilots, and this configuration is provided to the UE in phase 420. The first pilot configuration may be based at least in part on the preferred or required set of parameters of the UE in embodiments where the UE provides these to the base station. Subsequently, in phase 430 a first transmission is performed to the UE comprising first superimposed pilots, the first superimposed pilots being based on the first pilot configuration. In phase 440 the UE computes the FO and TO based on the first superimposed pilots to update synchronization of the UE with the base station, and attempts to decode the data of the first transmission. As described above, a neural receiver or an analytical approach may be employed by the UE to accomplish this. In phase 440, the superimposed pilots are used for both synchronization updating and reception in channel estimation or equalization.

[0077] In case the update of the synchronization fails in phase 440, the UE indicates this to the base station in phase 450. This message may include the T-failure and / or F-failure bits described herein above, for example. Responsively, the base station determines a second pilot configuration, as described above, to, for example, therein increase the pilot to data power ratio, increase the bandwidth, and / or increase the number of REs which carry superimposed pilots in the transmission. The second pilot configuration is provided to the UE in phase 460 and a second transmission comprising second superimposed pilots is sent to the UE in phase 470. The second superimposed pilots are in accordance with the second pilot configuration. Phases 450 and / or 460 may be communicated using pilots which are not superimposed with data, that is, dedicating some REs of the transmission to pilots only.

[0078] Following phase 470 the UE repeats the operations of phase 440 to attempt simultaneous update of the frequency and / or time synchronization and communication. If the attempt fails, the UE may indicate this to the base station, which may responsively switchto using the RP approach. In some embodiments, the base station is configured to switch to the RP approach after the first failure indication 450 from the UE.

[0079] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, a base station, and on the right, a UE. Time advances from the top toward the bottom.

[0080] Phases 510, 520, 540 and 550 correspond to phases 410, 420, 430 and 440, respectively. In phase 530, the base station requests the UE to provide feedback concerning how the updating of the synchronization based on the superimposed pilots succeeds. This is feedback which is provided also in case the updating of the synchronization does not fail, as in the example of FIGURE 4. Phases 520 and 530 may take place in either order, and, in some embodiments, they are combined into a single message.

[0081] Following the joint synchronization updating and decoding of data in phase 550, wherein the superimposed pilots are used for both synchronization updating and reception in channel estimation or equalization, a feedback message is provided to the base station in phase 560. The feedback may be transmitted as a CQI data structure, for example. The feedback comprises an indication of the estimated TO and FO, for example as real values. These indications may be provided in terms of variables a and b as:

[0082] The base station may use the feedback of phase 560 to adjust the pilot configuration for the next transmission. For example, if the estimated offsets deviate from estimates available to the base station from observing the UE’s transmission, the base station may define the updated pilot configuration with a higher pilot to data power ratio for superimposed REs, a larger subset of REs with superimposed pilots, increase the use of TRS, or increase the bandwidth, compared to the pilot configuration most recently used.

[0083] 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 by a user equipment, for example, or by a control device configured to control the functioning thereof, when installed therein.

[0084] Phase 610 comprises receiving, from a network and by an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration. Phase 620 comprises determining whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals. Phase 630 comprises, responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmitting to the network an indication of a synchronization update failure.

[0085] FIGURE 7 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 by a base station, for example, or by a control device configured to control the functioning thereof, when installed therein.

[0086] Phase 710 comprises transmitting, to a user equipment and from an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration. Phase 720 comprises receiving, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals. Phase 730 comprises transmitting, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.

[0087] FIGURE 8 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 by a user equipment, for example, or by a control device configured to control the functioning thereof, when installed therein.

[0088] Phase 810 comprises transmitting, to a network and from an apparatus, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals. Phase 820 comprises receiving, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network. Phase 830 comprises updating a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals. The method may further comprise using the first superimposed pilot signals in channel estimation when receiving data of the firsttransmission. Such use of the first superimposed pilot signals amounts to simultaneous synchronization and communication.

[0089] FIGURE 9 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 by a base station, for example, or by a control device configured to control the functioning thereof, when installed therein.

[0090] Phase 910 comprises receiving, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals. Phase 920 comprises determining and transmitting to the user equipment a first pilot configuration. Finally, phase 930 comprises transmitting to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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 depending 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.

[0097] As used herein, “at least one of the following: ” and “at least one of ” 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

[0098] At least some embodiments of the present invention find industrial application in cellular communication.ACRONYMS LISTCQI channel quality indicatorDMRS demodulation reference signalsFO frequency offsetRE resource elementTO time offset TRS tracking reference signalREFERENCE SIGNS LISTCITATION LISTY. Zhang, H. Zhao, W. Xia, F. Gao, L. Yang and H. Zhu, "Superimposed Pilot Transmission in Cell-Free Massive MIMO With Non-Ideal RF Responses," in IEEE Transactions on Vehicular Technology, vol. 71, no. 12, pp. 12856-12868, Dec. 2022, doi: 10.1109 / TVT.2022.3196411. https: / / ieeexpl0re.ieee.0rg / stamp / stamp.j sp?tp=&arnumber=9850397 TECHNICAL CLAUSES:Clause 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, from a network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; determine whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals; and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmit to the network an indication of a synchronization update failure.Clause 2. The apparatus according to Clause 1, further caused to: receive, from the network, a second pilot configuration after the transmission of the indication of the synchronization update failure, and to receive a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.Clause 3. The apparatus according to Clause 2, wherein the second pilot configuration indicates at least one of: a higher pilot to data power ratio for superimposed pilot signals; a higher proportion of resource elements comprising superimposed pilot signals; and an increased use of tracking reference signals compared to the first pilot configuration.Clause 4. The apparatus according to Clause 2, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 5. The apparatus according to any of Clauses 1 - 4, further caused to: responsive to updating the time and / or frequency synchronization based on the first superimposed pilot signals, provide, to the network, an indication of a time offset and / or a frequency offset obtained based on the first superimposed pilot signals.Clause 6. The apparatus according to Clause 5, further caused to:perform the providing of the indication of the time offset and / or the frequency offset if the network has requested the apparatus to provide the indication of the time offset and / or the frequency offset.Clause 7. The apparatus according to any of Clauses 1 - 6, further caused to: transmit the indication of synchronization update failure to the network without using superimposed pilot signals.Clause 8. The apparatus according to any of Clauses 1 - 7, further caused to: determine whether the time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals by using, at least in part, an artificial neural network.Clause 9. The apparatus according to any of Clauses 1 - 8, further caused to update the time and / or frequency synchronization based on the first superimposed pilot signals responsive to the determination indicating the time and / or frequency synchronization can be updated based on the first superimposed pilot signals.Clause 10. The apparatus according to Clause 9, further caused to decode data of the first transmission using the first superimposed pilot signals for channel estimation.Clause 11. 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: transmit, to a user equipment, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; receive, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmit, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.Clause 12. The apparatus according to Clause 11, wherein the second pilot configuration indicates at least one of:-a higher pilot to data power ratio for superimposed pilot signals;-a higher proportion of resource elements comprising superimposed pilot signals; and-an increased use of tracking reference signals compared to the first pilot configuration.Clause 13. The apparatus according to Clause 11, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 14. The apparatus according to any of Clauses 11 - 13, further caused to receive from the user equipment an indication of a time offset and / or a frequency offset obtained by the user equipment based on the first superimposed pilot signals.Clause 15. The apparatus according to Clause 14, further caused to request the user equipment to send the indication of the time offset and / or the frequency offset.Clause 16. The apparatus according to any of Clauses 11 - 15, wherein the indication of synchronization update failure does not use superimposed pilot signals.Clause 17. A method comprising: receiving, from a network and in an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; determining whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals; and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmitting to the network an indication of a synchronization update failure.Clause 18. The method according to Clause 17, further comprising: receiving, from the network, a second pilot configuration after the transmission of the indication of the synchronization update failure, and receiving a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.Clause 19. The method according to Clause 18, wherein the second pilot configuration indicates at least one of a higher pilot to data power ratio for superimposed pilot signals; a higher proportion of resource elements comprising superimposed pilot signals; and an increased use of tracking reference signals compared to the first pilot configuration.Clause 20. The method according to Clause 18, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 21. The method according to any of Clauses 17 - 20, further comprising: responsive to updating the time and / or frequency synchronization based on the first superimposed pilot signals, providing, to the network, an indication of a time offset and / or a frequency offset obtained based on the first superimposed pilot signals.Clause 22. The method according to Clause 21, further comprising: performing the providing of the indication of the time offset and / or the frequency offset if the network has requested the apparatus to provide the indication of the time offset and / or the frequency offset.Clause 23. The method according to any of Clauses 17 - 22, further comprising: transmitting the indication of synchronization update failure to the network without using superimposed pilot signals.Clause 24. The method according to any of Clauses 17 - 23, further comprising: determining whether the time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals by using, at least in part, an artificial neural network.Clause 25. The method according to any of Clauses 17 - 24, further comprising updating the time and / or frequency synchronization based on the first superimposed pilot signals responsive to the determination indicating the time and / or frequency synchronization can be updated based on the first superimposed pilot signals.Clause 26. The method according to Clause 25, further comprising decoding data of the first transmission using the first superimposed pilot signals for channel estimationClause 27. A method comprising: transmitting, to a user equipment and from an apparatus, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; receiving, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmitting, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.Clause 28. The method according to Clause 27, wherein the second pilot configuration indicates at least one of:-a higher pilot to data power ratio for superimposed pilot signals;-a higher proportion of resource elements comprising superimposed pilot signals; and -an increased use of tracking reference signals compared to the first pilot configuration.Clause 29. The method according to Clause 27, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 30. The method according to any of Clauses 27 - 29, further comprising receiving from the user equipment an indication of a time offset and / or a frequency offset obtained by the user equipment based on the first superimposed pilot signals.Clause 31. The method according to Clause 30, further comprising requesting the user equipment to send the indication of the time offset and / or the frequency offset.Clause 32. The method according to any of Clauses 27 - 31, wherein the indication of synchronization update failure does not use superimposed pilot signals.Clause 33. 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, from a network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; determine whether time and / or frequency synchronization of the apparatus with the network can be updated based on the first superimposed pilot signals; and responsive to the determination that the time and / or frequency synchronization cannot be updated based on the first superimposed pilot signals, transmit to the network an indication of a synchronization update failure.Clause 34. 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: transmit, to a user equipment, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration; receive, from the user equipment, an indication of a failure to update time and / or frequency synchronization using the first superimposed pilot signals, and transmit, to the user equipment, a second pilot configuration and a second transmission comprising second superimposed pilot signals, the second superimposed pilot signals being based on the second pilot configuration.Clause 35. 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: transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals; receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.Clause 36. The apparatus according to Clause 35, further caused to obtain an initial time and / or frequency synchronization with the network based on a synchronization signal block broadcasted by the network.Clause 37. The apparatus according to Clause 35 or 36, further caused to: transmit the message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals without using superimposed pilot signals.Clause 38. The apparatus according to any of Clauses 35 - 37, wherein the first pilot configuration indicates a pilot to data power ratio for superimposed pilot signals and a set of resource elements comprising superimposed pilot signals.Clause 39. The apparatus according to Clause 38, wherein the first pilot configuration further indicates whether tracking reference signals are to be provided for transmissions.Clause 40. The apparatus according to any of Clauses 35 - 39, further caused to: receive, from the network, and responsive to an indication that the apparatus has failed to update the time and / or frequency synchronization of the apparatus with the network using the first superimposed pilot signals, a second pilot configuration.Clause 41. The apparatus according to Clause 40, wherein the second pilot configuration indicates at least one of: a higher pilot to data power ratio for superimposed pilot signals; a higher proportion of resource elements comprising superimposed pilot signals, and an increased use of tracking reference signals compared to the first pilot configuration.Clause 42. The apparatus according to any of Clauses 35 - 41, further caused to: perform the updating of the time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals by using, at least in part, an artificial neural network.Clause 43. The apparatus according to any of Clauses 35 - 42, further caused to:indicate, to the network, a requirement or preference of the apparatus for a pilot configuration in terms of a preferred bandwidth, a minimum pilot to data power ratio for superimposed pilot signals, and a minimum pilot to data density for superimposed pilot signals.Clause 44. The apparatus according to any of Clauses 35 - 43, further caused to decode data of the first transmission using the first superimposed pilot signals for channel estimation, equalisation or data reception.Clause 45. 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, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals;- determine and transmit to the user equipment a first pilot configuration, and- transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.Clause 46. The apparatus according to Clause 45, further caused to receive from the user equipment an indication that the user equipment has failed to update a time and / or frequency synchronization of the user equipment with the apparatus using the first superimposed pilot signals, and to responsively transmit, to the user equipment, a second pilot configuration.Clause 47. The apparatus according to Clause 46, wherein the second pilot configuration indicates at least one of:-a higher pilot to data power ratio for superimposed pilot signals,-a higher proportion of resource elements comprising superimposed pilot signals and -an increased use of tracking reference signals compared to the first pilot configuration.Clause 48. The apparatus according to Clause 46, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 49. The apparatus according to any of Clauses 45 - 48, wherein the message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals does not use superimposed pilot signals.Clause 50. The apparatus according to any of Clauses 45 - 49, further caused to receive, from the user equipment, a requirement or preference of the user equipment for a pilot configuration in terms of a minimum bandwidth, a minimum pilot to data power ratio for superimposed pilot signals and a minimum pilot to data density for superimposed pilot signals.Clause 51. A method comprising: transmitting, to a network and from an apparatus, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals; receiving, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and updating a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.Clause 52. The method according to Clause 51 further comprising obtaining an initial time and / or frequency synchronization with the network based on a synchronization signal block broadcasted by the network.Clause 53. The method according to Clause 51 or 52, further comprising: transmitting the message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals without using superimposed pilot signals.Clause 54. The method according to any of Clauses 51 - 53, wherein the first pilot configuration indicates a pilot to data power ratio for superimposed pilot signals and a set of resource elements comprising superimposed pilot signals.Clause 55. The method according to Clause 54, wherein the first pilot configuration further indicates whether tracking reference signals are to be provided for transmissions.Clause 56. The method according to any of Clauses 51 - 55, further comprising: receiving, from the network, and responsive to an indication that the apparatus has failed to update the time and / or frequency synchronization of the apparatus with the network using the first superimposed pilot signals, a second pilot configuration.Clause 57. The method according to Clause 56, wherein the second pilot configuration indicates at least one of: a higher pilot to data power ratio for superimposed pilot signals; a higher proportion of resource elements comprising superimposed pilot signals, and an increased use of tracking reference signals compared to the first pilot configuration.Clause 58. The method according to any of Clauses 51 - 57, further comprising: performing the updating of the time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals by using, at least in part, an artificial neural network.Clause 59. The method according to any of Clauses 51 - 58, further comprising: indicating, to the network, a requirement or preference of the apparatus for a pilot configuration in terms of a minimum bandwidth, a minimum pilot to data power ratio for superimposed pilot signals, and a minimum pilot to data density for superimposed pilot signals.Clause 60. The method according to any of Clauses 51 - 59, further comprising decoding data of the first transmission using the first superimposed pilot signals for channel estimation, equalisation or data reception.Clause 61. A method, comprising: receiving, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals; determining and transmitting to the user equipment a first pilot configuration, and transmitting to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.Clause 62. The method according to Clause 61, further comprising receiving from the user equipment an indication that the user equipment has failed to update a time and / or frequency synchronization of the user equipment with the apparatus using the first superimposed pilot signals, and responsively transmitting, to the user equipment, a second pilot configuration.Clause 63. The method according to Clause 62, wherein the second pilot configuration indicates at least one of:-a higher pilot to data power ratio for superimposed pilot signals,-a higher proportion of resource elements comprising superimposed pilot signals and -an increased use of tracking reference signals compared to the first pilot configuration.Clause 64. The method according to Clause 62, wherein the second pilot configuration indicates use of pilot signals which are not superimposed with data.Clause 65. The method according to any of Clauses 61 - 64, wherein the message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals does not use superimposed pilot signals.Clause 66. The method according to any of Clauses 61 - 65, further comprising receiving, from the user equipment, a requirement or preference of the user equipment for a pilot configuration in terms of a minimum bandwidth, a minimum pilot to data power ratio for superimposed pilot signals and a minimum pilot to data density for superimposed pilot signals.Clause 67. 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: transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals; receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.Clause 68. 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, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals; determine and transmit to the user equipment a first pilot configuration, and transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

Claims

37CLAIMS:

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: transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals; receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

2. The apparatus according to claim 1, further caused to obtain an initial time and / or frequency synchronization.

3. The apparatus according to claim 1 or 2, further caused to: transmit the message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals without using superimposed pilot signals.

4. The apparatus according to any of claims 1 - 3, wherein the first pilot configuration indicates a pilot to data power ratio for superimposed pilot signals and a set of resource elements comprising superimposed pilot signals.

5. The apparatus according to claim 4, wherein the first pilot configuration further indicates whether tracking reference signals are to be provided for transmissions.

6. The apparatus according to any of claims 1 - 5, further caused to: receive, from the network, and responsive to an indication that the apparatus has failed to update the time and / or frequency synchronization of the apparatus with the network using the first superimposed pilot signals, a second pilot configuration.

387. The apparatus according to claim 6, wherein the second pilot configuration indicates at least one of: a higher pilot to data power ratio for superimposed pilot signals; a higher proportion of resource elements comprising superimposed pilot signals, and an increased use of tracking reference signals compared to the first pilot configuration.

8. The apparatus according to any of claims 1 - 7, further caused to: perform the updating of the time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals by using, at least in part, an artificial neural network.

9. The apparatus according to any of claims 1 - 8, further caused to: indicate, to the network, a requirement or preference of the apparatus for a pilot configuration in terms of a preferred bandwidth, a minimum pilot to data power ratio for superimposed pilot signals, and a minimum pilot to data density for superimposed pilot signals.

10. The apparatus according to any of claims 1 - 9, further caused to decode data of the first transmission using the first superimposed pilot signals for channel estimation, equalisation or data reception.

11. 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, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals;- determine and transmit to the user equipment a first pilot configuration, and- transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

12. A method comprising: transmitting, to a network and from an apparatus, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals;receiving, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and updating a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

13. A method, comprising: receiving, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals; determining and transmitting to the user equipment a first pilot configuration, and transmitting to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

14. 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: transmit, to a network, a message indicating that the apparatus supports wireless transmissions comprising superimposed pilot signals; receive, from the network, a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on a first pilot configuration received from the network; and update a time and / or frequency synchronization of the apparatus with the network based on the first superimposed pilot signals.

15. 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, from a user equipment, a message indicating that the user equipment supports wireless transmissions comprising superimposed pilot signals; determine and transmit to the user equipment a first pilot configuration, and transmit to the user equipment a first transmission comprising first superimposed pilot signals, the first superimposed pilot signals being based on the first pilot configuration.

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