Apparatus and method for scell communication

Abstract

User equipment (UE) receives from a network apparatus providing the UE with a serving cell, configuration information including uplink (UL) channel resources for communication with a secondary cell (S

Description

Title of the Invention APPARATUS AND METHODS FOR SCELL COMMUNICATION Field of the Invention Various example embodiments relates to apparatus and methods for Secondary Cell (SCell) synchronisation. Background to the Invention To reduce network energy consumption, it is known to provide for SCell operation, including for both intra-band and inter-band Carrier Aggregation (CA) in co-located and non co-located cells, without the continuous broadcasting of a synchronisation signal, i.e. the Synchronization Signal Block (SSB). In such circumstances, User Equipment (UE) will measure an SSB transmitted by a nearby Primary Cell (PCell) or another SCell for synchronisation with an SSB-less SCell. Summary of the Invention According to a first example embodiment, apparatus comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs; and transmit an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell . The configuration information may be based on timing information, itself determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. The instructions may further cause the apparatus to: receive from the network apparatus adjustment information for the timing, frequency and / or power of communications between the UE and the SCell. In respect of frequency, this may be related to a scenario with inter-band non-contiguous carriers, whereby PCell and SCell use different frequency band f_l and f_2, and thus lead to a frequency offset. The instructions may further cause the apparatus to, based on the adjustment information, at least one of: adjusting the timing of receiving from a signal from the SCell, adjusting the timing of transmitting a signal to the SCell, and adjusting the power of transmitting a signal to the SCell. Where this is the case, the instructions may further cause the apparatus to: based on the adjustment information, receive from the SCell a tracking reference signal, and synchronize with the SCell based on the tracking reference signal. The instructions further cause the apparatus to: receive from the network apparatus notification of activation of the SCell, wherein the adjusting is done after receiving the notification. According to a second example embodiment, apparatus for a network apparatus comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: transmit a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE, wherein the request includes timing information determined at least in part based on a location of the UE in relation to a location of the SCell and / or a location of another cell which provides the UE with a timing reference signal. The instructions may further cause the apparatus to: receive from the SCell the UL channel resources for the UE; and forward towards the UE the UL channel resources for the UE as part of configuration information. The instructions may further cause the apparatus to: receive from the SCell adjustment information for the timing, frequency and / or power of communications between the UE and the SCell; and transmit to the UE the adjustment information. The instructions further cause the apparatus to: transmit to the UE notification of activation of the SCell. According to a third example embodiment, apparatus for a secondary cell, SCell, comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive a request from a network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell is not transmitting a timing reference signal to the UE does not transmit synchronization signal blocks, SSBs, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. The instructions may further cause the apparatus to: determine UL channel resources for the UE using the timing information; and transmit to the network apparatus the determined UL channel resources for the UE. The instructions may further cause the apparatus to: receive an uplink signal from the UE, and determine from the timing of the uplink signal from the UE adjustment information for the timing, frequency and / or power of communications between the UE and the SCell. The instructions may further cause the apparatus to: transmit to the network apparatus the adjustment information. The instructions may further cause the apparatus to: apply a power adjustment for transmissions to the UE based on the adjustment information. The instructions may further cause the apparatus to: upon not receiving a signal from the UE within a predetermined time, initiate transmission of SSB signals. According to a fourth example embodiment, a method comprises: receiving from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs; and transmitting an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell. According to a fifth example embodiment, a method for a network comprises: transmitting a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. According to a sixth example embodiment, a method for an SCell comprises: receiving a request from network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell is not transmitting a timing reference signal to the UE does not transmit synchronization signal blocks, SSBs, wherein the request includes timing information determined at least in part based on the location of the UE 3 in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. The method may further comprise: determining UL channel resources for the UE using the timing information; and transmit to the network apparatus the determined UL channel resources for the UE. According to a seventh example embodiment, a non-transitory computer readable medium comprises program instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: receiving from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs; and transmitting an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell. According to an eighth example embodiment, a non-transitory computer readable medium comprises program instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: transmitting a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. According to a ninth example embodiment, a non-transitory computer readable medium comprises program instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: receiving a request from network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell is not transmitting a timing reference signal to the UE does not transmit synchronization signal blocks, SSBs, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. The instructions may cause the apparatus to further perform: determining UL channel resources for the UE using the timing information; and transmitting to the network apparatus (signal 8) the determined UL channel resources for the UE. According to a tenth example embodiment, a computer program is provided comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform: receiving from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs; and transmitting an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell. According to a eleventh example embodiment, a computer program is provided comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform: transmitting a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. According to a twelfth example embodiment, a computer program is provided comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform: receiving a request from network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell is not transmitting a timing reference signal to the UE does not transmit synchronization signal blocks, SSBs, wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal. The instructions may cause the apparatus to further perform: determining UL channel resources for the UE using the timing information; and transmitting to the network apparatus (signal 8) the determined UL channel resources for the UE. In all the above example embodiments, wherein the timing information is determined at least in part based on the location of the UE in relation to that of the SCell and that of another cell which provides the UE with a timing reference signal. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. Brief Description of the Drawings. Example embodiments will now be described with reference to the accompanying figures in which: Figures 1 and 2 illustrate SSB-less SCell communication; Figure 3 is a message sequence diagram illustrating an example embodiment of SSB-less SCell communication; Figures 4 and 5 illustrate the timing of UE, SCell and PCell signals; Figures 6 to 8 are flow diagrams illustrating examples methods of SSB-less SCell communication; and Figure 9 is a simplified block diagram illustrating a device that is suitable for implementing example embodiments of the present disclosure. Detailed Description of Embodiments The principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these example embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below. The terminology used herein to describe embodiments is not intended to limit the scope. The articles "a," "an," and "the" are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including," when used herein, specify the presence of stated features, items, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and / or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein. Carrier Aggregation (CA) allows UE to transmit and receive data on multiple component carriers (CCs) at the same time, enabling UE to utilize all available spectrum resources. For example, with 3GPP, in New Radio (NR), there can be up to 32 CCs aggregated for UE. Each of the CCs can belong to different technologies, e.g. Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD), can belong to different bands, and have different numerologies. The CCs in CA can be either co-located or non-co-located. UE first connects to a primary cell (PCell) which will serve as the primary component carrier for the UE. During or after the connection setup with the PCell, the PCell may configure eligible secondary carriers (SCells) for the UE. The PCell configures UE with all the necessary configurations for the SCells through Radio Resource Control (RRC) preparing the SCells for use when required. The configured SCells are activated based on activation methods for the UE. That could be either blind activation or buffer-based activation. Once an SCell is activated, UE can start to transmit and receive data from it. Dual Connectivity (DC) allows a UE to transmit and receive data on multiple component carriers from two cell groups (CG) via master node (MN) and secondary node (SN). With Evolved UMTS Terrestrial Radio Access (E-UTRA) Dual Connectivity (EN-DC), a UE can be connected to both Long-Term Evolution (LTE) E-UTRA and 5G NR nodes. The Core Network (CN) is either LTE Evolved Packet Core (EPC) or 5G Core. This was later expanded so that both cells can belong to 5G NR, in which case the CN is exclusively 5G Core. These various options came under the general term Multi-Radio Dual Connectivity (MR-DC). MR-DC is a generalization of Intra-E-UTRA Dual Connectivity. MR-DC can offer a UE more resources for higher throughput. More commonly, it helps operators improve mobility robustness and handovers in macro / micro-cell deployments. It can also aid in migrating networks from 4G to 5G. 5G-New Radio Dual Connectivity (NR-DC) is a 5G connectivity option where one 5G user equipment (UE) connects to the 5G network via both a MN (Master Node) and a SN (Secondary Node). The UE serving cells in MN define the Master Cell Group (MCG), whereas the UE serving cells in SN define the Secondary Cell Group (SCG). DC allows a UE to transmit and receive data on multiple component carriers from two cell groups via master gNodeB (MN) and secondary gNodeB (SN). With NR-DC, UE is connected to a Next Generation Node B (gNB) that acts as MN and one gNB that acts as SN. The MN is connected to 5G core network while the SN is connected to MN via the Xn interface. NR-DC can also be used when a UE is connected to two gNBDUs (Distributed Unit), one serving the MCG and the other serving the SCG, connected to the same gNB-CU (Centralized Unit)), acting both as a MN and as a SN. In the context of UE synchronisation with an SSB-less SCell, the inventors have recognised that UE reliance on an SSB transmitted by a nearby PCell or another SCell for synchronisation is at best an approximation. For some band combinations and non-co-located scenarios, a UE might not be able to use coarse time / frequency synchronization based on a nearby PCell or another SCell. Also, a UE may require a robust SSB type synchronisation signal and it can be difficult for the network or the UE to predict when such robust synchronisation signal is required, at least without some estimations or measurements. The inventors have further recognised the desirability of both network triggered and UE triggered on-demand-SSB solutions to allow an SSB-less SCell to be activated when required. Referring to figures 1 and 2, SSB-less SCell operation is illustrated with a nearby PCell providing a UE with a timing reference 20. There will be at least two sources of error. First, there is a timing alignment error (TAE) between the time bases of the PCell and the SCell which may depend on how they are connected to a common clock. Secondly, there is a propagation delay difference (PDD) which is a difference between how long it takes a signal to travel to the UE from the PCell compared to from the SCell. PDD will depend on channel conditions and the geometric disposition of PCell termination point (TP), SCell TP, and UE. A combined receive timing difference (RTD) can be defined as the sum of TAE and PDD. Similarly, a Power Imbalance (PI) can be defined as the difference in power loss on a PCell signal compared to that on a signal from the SCell, as observed at the UE. RTD and PI conditions are not generally reported from UE to the network, so it is hard for the network to know if / when these conditions can be met. In practice, when a UE is configured with an SSB-less SCell, it will blindly rely on an SSB transmitted by the PCell as an approximation for synchronisation, and monitor the Tracking Reference Signal (TRS) for the fine synchronization, i.e. in the hope that RTD and PI are not too big. If RTD and PI conditions are not satisfied, the UE cannot decode the TRS on the SSB-less SCell, leading to the failure of SSB-less SCell operations. In accordance with some aspects of the present invention, the inventors have appreciated that the PDD element of the RTD error can be mitigated by utilising a-priori 8 knowledge of the known geometric disposition of transceivers (e.g., PCell TP, SCell TP, and UE), especially in combination with UE positioning parameters (including delay on the link of PCell TP-UE pair). In other words, the RTD error can be mitigated by utilising timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of the PCell which provides the UE with a timing reference signal. The PCell as a timing reference is particularly convenient since when the UE is in an RRC-connected state with the PCell, the distance between PCell TP and UE (and also the location of the UE) can be readily determined. Assistance information which can be used to mitigate the RTD error can be determined by the network and signalled to the SSB-less SCell and / or UE to facilitate UE-SCell communication. Similarly, assistance information which better allows for the range between the UE and SSB-less SCell can be used to mitigate PI. Figure 3 is a message sequence diagram illustrating an example embodiment of SSB-less SCell communication. Step 1 - Location Preparation. A priori knowledge of the location of the PCell TP and the SCell TP is likely available, for example, pre-configured in Operations, Administrative and Maintenance (OAM) records for Open-RAN (O-RAN). If not, the network (PCell TP / gNB-Distributed Unit (DU), gNB-CU and SCell TP gNB-DU) can obtain and store the PCell TP and SCell TP locations and related parameters. Yet another option is to use any state-of-the-art positioning system to determine the PCell TP and SCell TP locations. Step 2 - Connection. UE connection with the PCell and the network can be readily established using standard RRC procedures. Step 3 - Location Request. In order to ensure the condition for SSB-less SCell operations for network energy saving, either the PCell or the Access &Mobility Management (AMF) function of gNB-CU initiates a request for location determination of the UE (having a priori knowledge of the location of the PCell TP and the SCell TP). This is done to locate the UE to obtain an estimate of propagation delay, which is used to check whether RTD and PI conditions can be met, and therefore to determine whether SSB-less SCell operation can be implemented. This requires the determination of the range between the PCell TP and the UE. Step 4 - Location Procedure. The location of UE is determined, for example, using standard positioning procedures of the type described in technical standard TS 38.305. Step 5 - Delay Determination. Using the determined location of the UE and the known geometric disposition of PCell TP and SCell TP, gNB-DU determines the distance between the UE and SCell TP and the corresponding propagation delay on a signal between the UE and the SCell. With the knowledge of the location of the UE with respect to the PCell TP and the location of the SCell TP with respect to the PCell TP, the range between the UE and the SCell TP can be calculated via triangulation. Step 6 - SCell Request. gNB-CU determines a need for uplink transmission from the UE to SCell. gNB-CU transmits a request to the SCell for the SCell to determine UL channel resources for the UE. The request includes assistance information including timing information (e.g. the propagation delay) determined by the network in step 5. Note, gNB-CU handles SCell activation and informs the gNB-CU with the PCell's MAC entity managing SCell operations Step 7 - UE Resource Determination. The SCell receives the request and determines UE UL channel resources using the timing information. This may include UL resources for at least one of a Physical Random Access Channel (PRACH), Sounding reference signals (SRS) and UL reference signals (RS), SCell's bandwidth parts (BWPs) and information elements (IE), optionally with parameters defining periodicity and start offset. The start offset may be calculated using the timing of the reference cell (e.g., PCell) and the timing information such as the propagation delay. This ensures that the UE's UL transmissions start at the required time (as discussed below with reference to figures 4 and 5) from the perspective of the SCell. In one example embodiment, the configuration for the PRACH preamble is different from those for legacy PRACH procedure such that when the network receives the PRACH preamble based on the specific configuration, the network would be able to recognize the received preamble and would not proceed with the normal RACH procedure but used the received preamble for calculation of the time adjustment. Step 8 - UE Resource. The SCell transmits a signal with the UE UL channel resources to the network. Step 9 - RRC Reconfig. The PCell provides the UE with the UE UL channel resources for the SCell as part of an RRC reconfiguration. Step 10 - UE-SCell UL Signalling (with timing correction). The UE transmits an UL signal to the SCell in the UE UL channel resources determined by SCell in step 7 using a timing reference from the PCell TP and the distance between the UE and PCell TP (i.e. adapting to ambiguity in the PCell TP timing reference). Step 11 - Adjustment Determination. The SCell measures the received UL signal from the UE and determines adjustment information which will compensate for a time difference and, optionally, power imbalance. For example, the SCell can use RACH preamble measurements, and then calculate the necessary timing adjustment as illustrated in Fig. 4. If the SCell fails to detect or receive the UL signal within a predetermined time period, the SCell may fall back to the legacy procedure and start transmitting SSB(s) to be detected by the UE and, thus, acquire the time synchronization with the SCell. Referring to fig. 4, the UE transmits the UL signal in step 10 to the SCell without prior synchronization to the SCell TP. This results in the signal arriving at the SCell with a time of arrival that can not be accurately predicted by the SCell, but where arrival in a time window is expected. Thus, the SCell TP receiver can detect the arrival of the signal from the UE in the expected window, and determine timing adjustment calculated from the arrival time of the UL signal (e.g., RACH preamble), propagation delay from UE to SCell TP, any delay introduced by a midhaul link between gNB-CU and SCell gNB-DU and any variation with respect to the reference PCell and SCell timing base. I.e. a coarse synchronisation. Also, it should be noted that gNB-CU and gNB-DU are generally deployed in close proximity. Specifically, in the RAN architecture, the gNB-DU and gNB-CU can be different chipsets on the same card or separate cards within a same rack. Consequently, the delay introduced by the 'midhaul' link between gNB-CU and gNB-DU pair may be negligible compared to the propagation delay over the air-interface, e.g., from UE to SCell TP. In an embodiment, power adjustment at SCell TP can be determined by using the distance between the UE and SCell TP pair if the UE transmit a given UL signal (e.g. UL preamble) with a known power. A power difference can then be calculated based on the received preamble power at the SCell TP and the known transmission power of the UE. The SCell TP may compensate for the power imbalance mismatch for subsequent UE-specific signals / channels. This compensation can be achieved through pre-emptive adjustments, such as power boosting or reduction, ensuring that the power imbalance remains within specified threshold. In summary, by following this power adjustments, the network ensures that the SCell TP provides a signal level that is comparable to the PCell TP, thereby mitigating power imbalance at UE. Step 12 - SCell provision to UE of adjustment information. The SCell provides the adjustment(s) such as time and power offsets to the gNB-CU, and the PCell configures UE with these adjustments for receiving subsequent SCell DL communications. This can be done using L2 or L3 signalling. Step 13 - UE Response. The UE acknowledges receipt of these adjustments to PCell. In one possible example embodiment, if no acknowledgement is received within a predetermined time period, PCell may retransmit the adjustment(s). Also, the UE may continue the UL signalling of step 10 if the UE does not receive the adjustment(s) within a predetermined time period. In one example embodiment, if the UE is configured in step 10 to transmit PRACH preamble before activation of the SCell, the UE may wait for the adjustment(s) within the Random Access Response (RAR) window. It may retransmit the preamble if it does not receive the time adjustments within the RAR window. If it does not receive the time adjustments after the RAR window expires, the UE may expect SSBs from the SCell. Step 14 - SCell Activation. The PCell transmits notification of the PCell's activation of the SCell to the UE. The gNB-DU handles SCell activation and informs the gNB-CU with the PCell's MAC entity managing SCell operations (not shown). Step 15 - UE Preparation. Upon receiving an indication for SCell activation, the UE compensates by pre-emptively applying the necessary adjustments (i.e., time offset) specified by the SCell. Note that the adjustment (i.e., time offset) is derived at SCell TP from UL signal / channel receptions, e.g., leveraging channel reciprocity. Step 16 - TRS. The SCell transmits TRS signals to the UE, enabling it to efficiently achieve fine synchronization with the SCell. Step 17 - SCell Power Adjustment. The SCell applies above determined power adjustments, ensuring that the specified power imbalance limits are met at the UE for subsequent UE-specific signals / channels. In an example embodiment, the UE may stop transmitting the UL signals / channels (signal 10): after it receives the time adjustments (step 12), after a predetermined time period expires or after it receives the SCell activation command indicating the fallback to an SCell legacy procedure. In an example embodiment, at step 15, the UE may apply the SCell TP indicated adjustment (provided in step 12) to compensate for the time offset of all its subsequent channels / signals. For example, an uplink frame transmission may take place the amount 12 of the timing adjustment before the reception of the first detected path (in time) of the corresponding downlink frame from the SCell (the SCell is downlink synchronized to the PCell). In other words, the downlink and uplink frames can be synchronized using the UL-DL timing relation and SCell TP indicated time offset adjustment Tta wherein: 5 Tta (applied at the UE) = (NTASCe" + NTAoffset) x Tc where, NTASCe" is additional time offset measured at SCell TP using the UL signal / channel such as RACH preamble, which is then indicated to the UE (in step 12), and the basic time unit is Tc wherein: Tc = l / (Afmax x Nfft) in ns. 10 where Afmax is subcarrier spacing and Nfftis FFT size. Finally, the fixed value of NTAoffset may apply the value of Table 7.1.2-2 in section 7.1.2 ofTS 38.133, reproduced below: Frequency range and band of cell used for uplink transmission NTAoffset (Unit: TC) FR1 FDD or TDD band with neither E-UTRA-NR nor NB-IoT-NR coexistence case 25600 (Note 1) FR1 FDD band with E-UTRA-NR and / or NB-IoT-NR coexistence case 0 (Note 1) FR1 TDD band with E-UTRA-NR and / or NB-IoT-NR coexistence case 39936 (Note 1) FR2 13792 Note 1: The UE identifies based on the information n-Ti mi ng Advanceoffset as specified in TS 38.331 [2]. If UE is not provided with the information n-Ti mi ng Advanceoffset, the default value of is set as 25600 for FR1 band. In case of multiple UL carriers in the same TAG, UE expects that the same value of n-Ti mi ng Advanceoffset is provided for all the UL carriers according to clause 4.2 in TS 38.213 [3] and the value 39936 of can also be provided for a FDD serving cell. Note 2: Void Table 7.1.2-2 in Section 7.1.2 of TS 38.133 Adjusting the time offset of an Nta value by a positive or a negative amount indicates advancing or delaying the timing by a corresponding amount, respectively. As mentioned above, the gNB-CU and the gNB-DU are generally deployed in close proximity and the delay introduced by the 'midhaul' link is minimal. In addition, the timing difference between PCell TP and SCell TP is very small, typically in the order of nanoseconds scale. Note that the UE begins transmission of UL signal / channel with the timing of reference cell (e.g. PCell TP). Hence, the RTD is mainly constrained by the arbitrary timing mismatch due to the propagation delay difference. For example, with reference to figure 4: Nta (applied at the UE) = NTA (applied at the PCell) + A. This indicates that UL signal such as PRACH preamble can be used estimate the total time offset and provide the required time adjustments factors to the UE to ensure the RTD limits. In any of the above described embodiments, the timing reference is that of the PCell with which the UE is registered. As an alternative, the timing reference could be from another cell (e.g. another SCell) which shares a common time base with the SSB-less SCell. Conceivably, the same could apply to, for DC, cells on secondary nodes, e.g. a Primary Secondary Cell (PSCell) or even an external timing base such as from a Global Navigation Satellite System (including Galileo, GPS or GLONASS). FIG. 6 is a flowchart of an example method for network apparatus according to some example embodiments of the present disclosure. The method comprising: in step 601, transmit a request to an SCell that does not transmit synchronization signal blocks to provide UL transmission resources for UE; in step 602, receive from the SCell the UL channel resources for the UE; and in step 603, forward towards the UE the UL channel resources for the UE as part of configuration information. FIG. 7 is a flowchart of an example method for an SCell according to some example embodiments of the present disclosure. The method comprising: in step 701, receive a request from network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell is not transmitting a timing reference signal to the UE; in step 702, determine UL channel resources for the UE using the timing information; and in step 703, transmit to the network apparatus the determined UL channel resources for the UE. FIG. 8 is a flowchart of an example method according to some example embodiments of the present disclosure. <method claim> Figure 9 is a simplified block diagram of a device 900 that is suitable for implementing example embodiments of the present disclosure. The device 900 can be implemented at or as a part of either UE apparatus or cell providing apparatus. As shown, the device 900 includes a processor 910, a memory 920 coupled to the processor 910, a communication module 930 coupled to the processor 910, and a communication interface (not shown) coupled to the communication module 930. The memory 920 stores at least a program 940. The communication module 930 is for bidirectional communications, for example, via multiple antennas. The communication interface may represent any interface that is necessary for communication. The program 940 is assumed to include program instructions that, when executed by the associated processor 910, enable the device 900 to operate in accordance with the example embodiments of the present disclosure, as discussed herein with reference to FIGS. 1-6. The example embodiments herein may be implemented by computer software executable by the processor 910 of the device 900, or by hardware, or by a combination of software and hardware. The processor 910 may be configured to implement various example embodiments of the present disclosure. The memory 720 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 720 is shown in the device 700, there may be several physically distinct memory modules in the device 700. The processor 710 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation." This definition of circuitry applies to all uses of this term in this application, including in any claims. 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. Generally, various example embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of example embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the methods of figures 5 and 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various example embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media. Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server. In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable media. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), Digital Versatile Disc (DVD), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. Various example embodiments of the techniques have been described. In addition to or as an alternative to the above, the following examples are described. The features described in any of the following examples may be utilized with any of the other examples described herein. Acronyms CA Carrier Aggregation CC Component Carrier CG Cell Group CN Core Network DC Dual Connectivity EPC Evolved Packet Core FR1 Frequency Range 1 FR2 Frequency Range 2 LTE Long Term Evolution MAC Medium Access Control MCG Master Cell Group MN Master Node NR New Radio PCell Primary Cell PSCell Primary Secondary Cell RRC Radio Resource Control SCell Secondary Cell SCG Secondary Cell Group SN Secondary Node TRS Timing Reference Signal UE User Equipment

Claims

1. Apparatus for UE comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:receive from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs,transmit an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell.

2. Apparatus according to claim 1 wherein the configuration information is based on timing information, itself determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal.

3. Apparatus according to claim 1 or claim 2, wherein the instructions further cause the apparatus to:receive from the network apparatus adjustment information for the timing, frequency and / or power of communications between the UE and the SCell.

4. Apparatus according to claim 3, wherein the instructions further cause the apparatus to:based on the adjustment information, at least one of:adjusting the timing of receiving from a signal from the SCell,adjusting the timing of transmitting a signal to the SCell, andadjusting the power of transmitting a signal to the SCell.

5. Apparatus according to claim 3, wherein the instructions further cause the apparatus to:based on the adjustment information, receiving from the SCell a tracking reference signal, andsynchronizing with the SCell based on the tracking reference signal.

6. Apparatus according to any of claims 3 to 5, wherein the instructions further cause the apparatus to:receive from the network apparatus notification of activation of the SCell, wherein the adjusting is done after receiving the notification.

7. Apparatus for a network apparatus, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:transmit a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE,wherein the request includes timing information determined at least in part based on a location of the UE in relation to a location of the SCell and / or a location of another cell which provides the UE with a timing reference signal.

8. Apparatus according to claim 7, wherein the instructions further cause the apparatus to:receive from the SCell the UL channel resources for the UE; andforward towards the UE the UL channel resources for the UE as part of configuration information.

9. Apparatus according to claim 7 or claim 8, wherein the instructions further cause the apparatus to:receive from the SCell adjustment information for the timing, frequency and / or power of communications between the UE and the SCell; andtransmit to the UE the adjustment information.

10. Apparatus according to any of claims 7 to 9, wherein the instructions further cause the apparatus to:transmit to the UE notification of activation of the SCell.

11. Apparatus for a secondary cell, SCell, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:receive a request from a network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell_does not transmit synchronization signal blocks, SSBs,wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal.

12. Apparatus according to claim 11, wherein the instructions further cause the apparatus to:determine UL channel resources for the UE using the timing information; andtransmit to the network apparatus the determined UL channel resources for the UE.

13. Apparatus according to claim 12, wherein the instructions further cause the apparatus to:receive an uplink signal from the UE, anddetermine from the timing of the uplink signal from the UE adjustment information for the timing, frequency and / or power of communications between the UE and the SCell.

14. Apparatus according to claim 13, wherein the instructions further cause the apparatus to:transmit to the network apparatus the adjustment information.

15. Apparatus according to claim 13 or claim 14, wherein the instructions further cause the apparatus to:apply a power adjustment for transmissions to the UE based on the adjustment information.

16. Apparatus according to claim 12, wherein the instructions further cause the apparatus to:upon not receiving a signal from the UE within a predetermined time, initiating transmission of SSB signals.

17. Apparatus according to any preceding claim, wherein the timing information is determined at least in part based on the location of the UE in relation to that of the SCell and that of another cell which provides the UE with a timing reference signal18. A method for UE comprising:receiving from a network apparatus providing the UE with a serving cell, configuration information including UL channel resources for communication with a secondary cell, SCell, that does not transmit synchronization signal blocks, SSBs; andtransmitting an uplink signal to the SCell, wherein the timing of the uplink signal is based on timing of the serving cell.

19. A method for a network comprising:transmitting a request to a secondary cell, SCell, that does not transmit synchronization signal blocks to provide UL transmission resources for UE,wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal.

20. A method for an SCell comprising:receiving a request from network apparatus to provide UE with UL channel resources for communication with the SCell when the SCell does not transmit synchronization signal blocks, SSBs,wherein the request includes timing information determined at least in part based on the location of the UE in relation to that of the SCell and / or that of another cell which provides the UE with a timing reference signal.

21. A method according to claim 20 further comprising:determining UL channel resources for the UE using the timing information; andtransmit to the network apparatus the determined UL channel resources for the UE.

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