WO2021214007A1

WO2021214007A1 - Determining timing advance

Info

Publication number: WO2021214007A1
Application number: PCT/EP2021/060147
Authority: WO
Inventors: Karri Ranta-Aho; Kari Pajukoski; Mark Cudak; Rapeepat Ratasuk; Arto Lehti; Oskari TERVO
Original assignee: Nokia Technologies Oy
Priority date: 2020-04-20
Filing date: 2021-04-20
Publication date: 2021-10-28
Also published as: FI20205398A1

Abstract

There is provided receiving a first message comprising information indicating a reference TA setting characteristic to a first access node, determining a reference TA setting characteristic to a second access node and determining a timing advance offset for the second access node, based on the reference TA setting characteristic to the first access node and the reference TA setting characteristic to the second access node. A second message comprising the determined timing advance offset is sent; or wherein the first message further comprises communications device specific TA information, a second access node TA for the communications device is determined based on the communications device specific TA information and the determined timing advance offset and a second message comprising the second access node TA of the communications device is sent.

Description

DETERMINING TIMING ADVANCE TECHNICAL FIELD

The present invention relates to determining timing advances for access nodes.

BACKGROUND

[0001] This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section. [0002] A so called timing advance (TA) is used at a communications device for advancing an uplink transmit timing relative to an observed downlink receive timing. The TA can be established by performing a random access procedure. The random access procedure may comprise the communications device sending to a base station (BTS) a Physical Random Access Channel (PRACH) preamble using a fixed timing relative to an observed downlink receive timing. However, the times when the communications device is allowed to transmit a PRACH preamble can be restricted. Therefore, using the random access procedure for establishing the timing advance is associated with a latency in having to wait for the PRACH occasion and go through the PRACH procedure before the communications device is able to establish the TA and communicate with the base station using the TA. Moreover, using the random access procedure for establishing the timing advance involves the base station searching preamble signatures over a time window which makes it a heavy process for the base station.

[0003] In a RACH-less handover of a communications device from one cell, i.e. a source cell, to another cell, a target cell, a target cell TA can be established without a random access procedure. However, determining the target cell TA without a random access procedure is challenging if the cells are located in different base stations that do not target for the same receive timing window or the base stations do not have the same TA for the same distance from the base stations, or differences in implementations of the base stations need to be considered in the TA. [0004] Differences in implementations of the base stations contribute to total receive timing and become increasingly important, when frequency bands above 52.6 GHz are supported. Also, increasing Orthogonal Frequency-Division Multiplexing (OFDM) subcarrier spacing leads to a shorter cyclic prefix which will require even better time alignment at reception. In such cases the base station internal delay compensation becomes even more crucial for establishing the TA to be used in the cell.

SUMMARY

[0005] The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0006] According to a first aspect there is provided an apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determine a reference timing advance setting characteristic to the second access node; determine a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

- send a communications device a second message comprising the determined timing advance offset, or

- wherein the first message further comprises communications device specific timing advance information, the apparatus is caused to: determine a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and send a communications device a second message comprising the second access node timing advance of the communications device. [0007] According to a second aspect there is provided an apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determine a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

[0008] According to a third aspect there is provided a method comprising: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

- sending a communications device a second message comprising the determined timing advance offset, or

- wherein the first message further comprises communications device specific timing advance information, determining a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and sending a communications device a second message comprising the second access node timing advance of the communications device.

[0009] According to a fourth aspect there is provided a method comprising: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

[0010] According to a fifth aspect there is provided a computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node , on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

[0011] According to a sixth aspect there is provided a computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node. [0012] At least some embodiments support determining a timing advance to be used in a target access node in connection with a handover form a source access node to the target access node .

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:

[0014] Fig. 1 shows a part of an exemplifying wireless communications access network in accordance with at least some embodiments of the present invention;

[0015] Fig. 2 shows a block diagram of an apparatus in accordance with at least some embodiments of the present invention;

[0016] Fig. 3 shows an apparatus in accordance with at least some embodiments of the present invention;

[0017] Fig. 4 shows an example of an arrangement for wireless communications comprising a plurality of apparatuses, networks and network elements;

[0018] Fig. 5, Fig. 6 illustrate examples of methods in accordance with at least some embodiments of the present invention;

[0019] Fig. 7 illustrates an example of a sequence in accordance with at least some embodiments of the present invention;

[0020] Fig. 8 illustrates an example of a block diagram of an apparatus in accordance with at least some embodiments of the present invention;

[0021] Fig. 9 illustrates an example of a sequence in accordance with at least some embodiments of the present invention; and

[0022] Fig. 10 illustrates an example of a sequence in accordance with at least some embodiments of the present invention.

DETAILED DESCRIPTON OF SOME EXAMPLE EMBODIMENTS

[0023] The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

[0024] In connection with providing a communications device with more than one access node, e.g. multiple access nodes, for communications, there is provided receiving a first message comprising information indicating a reference TA setting characteristic to a first access node, determining a reference TA setting characteristic to a second access node and determining a timing advance offset for the second access node, on the basis of the reference TA setting characteristic to the first access node and the reference TA setting characteristic to the second access node. A second message comprising the determined timing advance offset is sent; or wherein the first message further comprises communications device specific TA information, a second access node TA for the communications device is determined on the basis of the communications device specific TA information and the determined timing advance offset and a second message comprising the second access node TA of the communications device is sent. In this way determining a timing advance to be used in the second access node in connection with having multiple access nodes for communications with the communications device may be supported.

[0025] Examples of scenarios having multiple access nodes for communications with a communications device, comprise scenarios where the communications device may be connected to multiple cells over multiple wireless links and where the communications device may be connected to a single cell over multiple wireless links. It should be appreciated that the communications device may not necessarily be simultaneously connected to multiple access nodes, but coordination is needed for successful communications of the communications device via the access node. These scenarios may comprise at least a Coordinated multi-point (CoMP) operation, multiple transmission and reception points (multi-TRPs) operation, dual connectivity (DC) operation and handovers of the communications device between cells. In the following, at least some examples have been described with reference to a handover scenario. However, the examples may be implemented using applicable control messages in the other scenarios, where timing advances are used by the communications device.

[0026] Messages may be communicated in different scenarios for facilitating the determining of timing advances for access nodes. Examples of the messages comprise control messages such as Radio Resource Control (RRC) protocol messages, handover messages and secondary node addition messages. Examples of the RRC messages comprise RRC configuration request, RRC reconfiguration request, RRC reconfiguration complete, RRC configuration request response and RRC reconfiguration request response. Examples of the handover messages comprise handover request, handover response and handover command. Examples of the secondary node addition messages comprise secondary node addition request and secondary node addition request acknowledgement (ACK). Examples of the messages are described in connection with sequences for scenarios illustrated in Figs. 7, 9 and 10.

[0027] An example of timing advance is described in TS38.300 V15.7.0 section 9.2.3 in connection with 5G New Radio. According to the example, a timing advance is defined by Nta+Nta, offset. In this way an uplink transmit timing of a communications device starts Nta+Nta, offset before a corresponding downlink reference time. The Nta, offset is a fixed component for the difference between the uplink transmit timing and the downlink reference time and Nta is the component that an access node (base station) adjusts. The farther away the communications device is from the access node, the larger the Nta may set so that the relative receive time as seen in the network node remains within a set reception window. This may be procedurally achieved by constantly measuring the receive timing of each uplink at the access node, and if the timing deviates too far from a target, then the base station sends a timing advance adjustment command to adjust the Nta. The downlink reference time may be a reception time of downlink transmission at the communications device.

[0028] A reference TA setting characteristic to an access node refers to an internal delay contribution of the access node to a two-way propagation delay between a communications device and the access node. The internal delay contribution may be determined on the basis of a delay caused by Radio Frequency (RF) processing of the access node. The RF processing may comprise delays caused by an RF processing portion of the access node. The RF processing portion may comprise one or more RF parts between a baseband processing portion and the wireless medium. Examples of the RF parts comprise at least one or more from a group comprising: antennas, RF cabling, RF front end and power amplifiers. The reference TA setting may be referred to a zero-distance TA, which corresponds to the TA setting of a device that is placed very close to the base station antenna so that the over-the-air radio propagation delay between the device and the base station is negligible. It should be appreciated that the zero- distance TA may in practice be different than a zero TA setting due to practical base station implementation aspects.

[0029] A timing advance offset may be a difference between zero-distance TAs of two cells of different access nodes or from the same access node, e.g. in CoMP/Multi-TRP. In an example of handover scenario of a communications device, the cells may comprise a source cell and a target cell. In an example according to at least some embodiments, the handover may be a RACH-less handover.

[0030] An access node may be a radio access node, base station, access point, base transceiver station (BTS), (e/g)NodeB or a TRP. An example of TRP is an antenna array with one or more antenna elements available to the network located at a specific geographical location for a specific area. A base station, BTS, access point or (e/g)NodeB may comprise more than one, i.e. a plurality of TRPs, that are spatially separated for communications with a communications device over radio channels that are independent form each other. Independent radio channels may each be characterized by their radio channel properties for example pathloss and propagation delay.

[0031] A target cell TA may refer to TA used by a communications device for uplink transmit timing in a target cell. Similarly, a source cell TA may refer to TA used by a communications device for uplink transmit timing in a source cell. It should be appreciated that the source cell and target cells may be in any cells that the communications device is connected to for communications of user data and/or signaling. In different scenarios the source cell and target cell may be named differently. Therefore, they may be named also as a first cell and a second cell, or a first access node and a second access node. In some scenarios, the communications device may be first connected to one cell or access node, i.e. a first cell/a source cell/a primary cell/first access node, before the communications device is connected to one or more further cells/access node, i.e. second cells/target cells/secondary cells/second access nodes.

[0032] In an example in accordance with at least some embodiments, a target cell TA may be determined in accordance with the following calculation: TA2= TA1 - 2*OTD - T_0ff, where TA1 is the source cell TA, TA2 is the target cell TA, OTD is an observed time difference (OTD) as measured by the communications device and T_0ff is (zero-distance TA in the source cell - zero-distance TA in the target cell). It should be appreciate that the above calculation is one example of a calculation of the target cell TA and other corresponding calculations may be made depending on the implementation of the components of the calculation by steps, coefficients basic timing samples, or microseconds, for example. It should be appreciated that the sign of the OTD may depend on whether the source cell or the target cell is used as reference. [0033] A communications device specific TA information may comprise a source cell TA of a communications device and a downlink OTD between the source cell and a target cell. In an example a source cell TA of the communications device comprises Nta+Nta, offset. The source cell TA and the target cell TA may be also referred to a first access node TA and a second access node TA of the communications device for communications with corresponding access nodes. Examples of scenarios, where the communications device may communicate with more than one access nodes comprise a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation. [0034] An OTD defines a time difference between receive timings of transmissions. An OTD measurement performed by the communications device provides a downlink OTD. Accordingly, the downlink OTD defines a time difference between receive timings of downlink transmissions from the different BTSs, for example a source base transceiver station (BTS) and a target BTS in a handover. It should be appreciated that a BTS may also be referred to a base station (BS) or (e/g)NodeB.

[0035] In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on Long Term Evolution Advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet protocol multimedia subsystems (IMS) or any combination thereof.

[0036] Fig. 1 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Fig. 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Fig. 1.

[0037] The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties. [0038] The example of Fig. 1 shows a part of an exemplifying radio access network.

[0039] Fig. 1 shows user devices 100 and 102 configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) 104 providing the cell. The physical link from a user device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage. The access node provides access by way of communications of radio frequency (RF) signals and may be referred to a radio access node. It should be appreciated that the radio access network may comprise more than one access nodes, whereby a handover of a wireless connection of the user device from one cell of one access node, e.g. a source cell of a source access node, to another cell of another node, e.g. a target cell of a target access node, may be performed.

[0040] A communication system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point, access node or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), etc.

[0041] The user device (also called UE, user equipment, user terminal, terminal device, wireless device, communications device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station. [0042] The user device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (IoT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human- to-computer interaction. The user device may also utilize cloud. In some applications, a user device may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud. The user device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE) just to mention but a few names or apparatuses.

[0043] Various techniques described herein may also be applied to a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. [0044] Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in Fig. 1) may be implemented.

[0045] 5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being capable of being integrated with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0046] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0047] The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 112, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Fig. 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0048] Edge cloud may be brought into radio access network (RAN) by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 104) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 108).

[0049] It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all -IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR.) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

[0050] 5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway/maritime/aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite 106 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on ground relay node 104 or by a gNB located on-ground or in a satellite.

[0051] It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e/g)NodeBs or may be a Home(e/g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (e/g)NodeBs of Fig. 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e/g)NodeBs are required to provide such a network structure.

[0052] For fulfilling the need for improving the deployment and performance of communication systems, the concept of “plug-and-play” (e/g)NodeBs has been introduced. Typically, a network which is able to use “plug-and-play” (e/g)Node Bs, includes, in addition to Home (e/g)NodeBs (H(e/g)nodeBs), a home node B gateway, or HNB-GW (not shown in Fig. 1). A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNBs back to a core network.

[0053] The following describes in further detail suitable apparatus and possible mechanisms for implementing some embodiments. In this regard reference is first made to Fig. 2 which shows a schematic block diagram of an exemplary apparatus or electronic device 50 depicted in Fig. 3, which may incorporate a transmitter according to an embodiment of the invention. [0054] The electronic device 50 may for example be a communications device, wireless device, mobile terminal or user equipment of a wireless communication system. However, it would be appreciated that embodiments of the invention may be implemented within any electronic device or apparatus which may require transmission of radio frequency signals. [0055] The apparatus 50 may comprise a housing 30 for incorporating and protecting the device. The apparatus 50 further may comprise a display 32 in the form of a liquid crystal display. In other embodiments of the invention the display may be any suitable display technology suitable to display an image or video. The apparatus 50 may further comprise a keypad 34. In other embodiments of the invention any suitable data or user interface mechanism may be employed. For example the user interface may be implemented as a virtual keyboard or data entry system as part of a touch-sensitive display. The apparatus may comprise a microphone 36 or any suitable audio input which may be a digital or analogue signal input. The apparatus 50 may further comprise an audio output device which in embodiments of the invention may be any one of: an earpiece 38, speaker, or an analogue audio or digital audio output connection. The apparatus 50 may also comprise a battery 40 (or in other embodiments of the invention the device may be powered by any suitable mobile energy device such as solar cell, fuel cell or clockwork generator). The term battery discussed in connection with the embodiments may also be one of these mobile energy devices. Further, the apparatus 50 may comprise a combination of different kinds of energy devices, for example a rechargeable battery and a solar cell. The apparatus may further comprise an infrared port 41 for short range line of sight communication to other devices. In other embodiments the apparatus 50 may further comprise any suitable short range communication solution such as for example a Bluetooth wireless connection or a USB/firewire wired connection.

[0056] The apparatus 50 may comprise a controller 56 or processor for controlling the apparatus 50. The controller 56 may be connected to memory 58 which in embodiments of the invention may store both data and/or may also store instructions for implementation on the controller 56. The controller 56 may further be connected to codec circuitry 54 suitable for carrying out coding and decoding of audio and/or video data or assisting in coding and decoding carried out by the controller 56.

[0057] The apparatus 50 may further comprise a card reader 48 and a smart card 46, for example a universal integrated circuit card (UICC) reader and UICC for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.

[0058] The apparatus 50 may comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example for communication with a cellular communications network, a wireless communications system or a wireless local area network. The apparatus 50 may further comprise an antenna 59 connected to the radio interface circuitry 52 for transmitting radio frequency signals generated at the radio interface circuitry 52 to other apparatus(es) and for receiving radio frequency signals from other apparatus(es). [0059] In some embodiments of the invention, the apparatus 50 comprises a camera 42 capable of recording or detecting imaging.

[0060] With respect to Fig. 4, an example of a system within which embodiments of the present invention can be utilized is shown. The system 10 comprises multiple communication devices which can communicate through one or more networks. The system 10 may comprise any combination of wired and/or wireless networks including, but not limited to a wireless cellular telephone network (such as a GSM (2G, 3G, 4G, LTE, 5G), UMTS, CDMA network etc.), a wireless local area network (WLAN) such as defined by any of the IEEE 802.x standards, a Bluetooth personal area network, an Ethernet local area network, a token ring local area network, a wide area network, and the Internet.

[0061] For example, the system shown in Fig. 4 shows a mobile telephone network 11 and a representation of the internet 28. Connectivity to the internet 28 may include, but is not limited to, long range wireless connections, short range wireless connections, and various wired connections including, but not limited to, telephone lines, cable lines, power lines, and similar communication pathways.

[0062] The example communication devices shown in the system 10 may include, but are not limited to, an electronic device or apparatus 50, a combination of a personal digital assistant (PDA) and a mobile telephone 14, a PDA 16, an integrated messaging device (IMD) 18, a desktop computer 20, a notebook computer 22, a tablet computer. The apparatus 50 may be stationary or mobile when carried by an individual who is moving. The apparatus 50 may also be located in a mode of transport including, but not limited to, a car, a truck, a taxi, a bus, a train, a boat, an airplane, a bicycle, a motorcycle or any similar suitable mode of transport. [0063] Some or further apparatus may send and receive calls and messages and communicate with service providers through a wireless connection 25 to a base station 24. The base station 24 may be connected to a network server 26 that allows communication between the mobile telephone network 11 and the internet 28. The system may include additional communication devices and communication devices of various types.

[0064] The communication devices may communicate using various transmission technologies including, but not limited to, code division multiple access (CDMA), global systems for mobile communications (GSM), universal mobile telecommunications system (UMTS), time divisional multiple access (TDMA), frequency division multiple access (FDMA), transmission control protocol-internet protocol (TCP -IP), short messaging service (SMS), multimedia messaging service (MMS), email, instant messaging service (IMS), Bluetooth, IEEE 802.11, Long Term Evolution wireless communication technique (LTE), 5G and any similar wireless communication technology. Yet some other possible transmission technologies to be mentioned here are high-speed downlink packet access (HSDPA), high speed uplink packet access (HSUPA), LTE Advanced (LTE-A) carrier aggregation dual carrier, and all multi-carrier technologies. A communications device involved in implementing various embodiments of the present invention may communicate using various media including, but not limited to, radio, infrared, laser, cable connections, and any suitable connection. In the following some example implementations of apparatuses utilizing the present invention will be described in more detail.

[0065] In an example in accordance with at least some embodiments the communications of the communications devices may comprise uplink transmissions and/or downlink transmissions of data. The uplink transmissions may be performed from a wireless device to the wireless communication system, e.g. an access node, and the downlink transmissions may be performed from the wireless communication system, e.g. an access node, to the wireless device. The uplink transmissions may be performed on an uplink shared channel, e.g. a Physical Uplink Shared Channel (PUSCH). The PUSCH may be transmitted by the wireless device on the basis of a grant received on a downlink control channel, e.g. a Physical Downlink control Channel (PDCCH). The downlink transmissions may be performed on a downlink shared channel, e.g. a Physical Downlink Shared Channel (PDSCH). Release 15 specifications of the 3GPP may be referred to for examples PUSCH and PDSCH procedures.

[0066] The downlink and uplink transmissions may be organized into frames, e.g. a radio frame. In an example, each frame may be of 10 ms duration and divided into subframes of 1ms duration. Each subframe may be further divided into multiple Orthogonal Frequency Division- Multiplexing (OFDM) symbols. The OFDM symbols may be arranged to slots within each subframe. In an example, the radio frame may include 10 subframes. One subframe may include two consecutive slots of 14 symbols with 30kHz sub-carrier spacing. Accordingly, the radio frame may in total include 20 slots.

[0067] Referring to Fig. 5, there is provided a method for supporting determining a timing advance to be used by a communications device for communications with an access node, when the communications device already has established a timing advance for communications with another access node. The method may be performed by a radio access node or an apparatus forming a part of a radio access node. A radio access node may provide a target cell in a handover from a source cell to the target cell, whereby determining a timing advance to be used by the communications device in the target cell may be supported by the method. The method may be applied also to other scenarios, where a communications device may communicate with more than one access node, such as in CoMP/Multi-TRP and DC.

[0068] Phase 502 comprises receiving a first message comprising information indicating a reference TA setting characteristic to a first access node.

[0069] In an example, in phase 502, the first message is received by the target radio access node from a source radio access node providing the first access node and the first message includes information for preparing the target radio access node for a handover of the communications device to the target radio access node.

[0070] Phase 504 comprises determining a TA setting characteristic to the second access node.

[0071] Phase 506 comprises determining a timing advance offset for the second access node, on the basis of the TA setting characteristic to the first access node and the TA setting characteristic to the second access node.

[0072] Phase 508 comprises sending a communications device a second message comprising the determined timing advance offset, or wherein the first message further comprises communications device specific TA information, phase 508 comprises determining a second access node TA for the communications device on the basis of the communications device specific TA information and the determined timing advance offset and sending a communications device a second message comprising the second access node TA of the communications device. Accordingly, phase 508 supports determining the TA to be used in the second access node by two alternatives, where in the first alternative, the phase 508 provides the timing advance offset which can be used at another device, e.g. the communications device, for determining the TA to be used by the communications device in the second access node. In the latter alternative in phase 508, the TA to be used in the second access node may be determined at the radio access node and communicated to the communications device in the second message.

[0073] In an example, in phase 508, the second message is received by a source radio access node from a target radio access node and the second message includes information indicating whether a handover of the communications device is accepted by the target radio access node. [0074] In an example according to at least some embodiments, if the first access node and the second access node are not synchronized, phase 508 comprises determining a transmission time difference of the first access node and second access node and determining the second access node TA, where the transmission time difference between the first access node and second access node is compensated. In an example, a compensation factor is added to the second access node TA for compensating the transmission time differences between the first access node and second access node.

[0075] In an example according to at least some embodiments, in phase 508, the communications device specific TA information comprises a first access node TA of the communications device and a downlink observed time difference between the first access node and the second access node .

[0076] In an example according to at least some embodiments, in phase 508, the timing advance offset comprises a difference between a zero-distance TA of the first access node and the zero-distance TA of the second access node .

[0077] In an example according to at least some embodiments, one or more of the phases 502 to 508, at least the timing advance offset for the second access node, are performed in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

[0078] In an example, a TA setting characteristics to an access node, for example in phase 504 the TA setting characteristic to the second access node may be known a-priori since being characteristic to implementation of the base station that provides the access node. Therefore, it should be appreciated that the phase 504 may be performed quite a while before receiving a first message in phase 502 or execution of any remaining phases of the method. On the other hand, phase 504 may be considered to cover also reading the TA setting for a memory where it has been stored for use. Accordingly, the TA setting characteristic to the access node may be determined with a local looping where a receiver (Rx) of the base station measures a transmitter (Tx) of the base station directly. In a handover the reference TA of the first access node and the reference TA of the second access node are sent to the same place.

[0079] Referring to Fig. 6, there is provided a method for supporting determining a timing advance to be used by a communications device for communications with an access node, when the communications device already has established a timing advance for communications with another access node. The method may be performed by a communications device or an apparatus forming a part thereof.

[0080] Phase 602 comprises receiving a first message from a first access node for initiating communications of the communications device with a second access node, said first message comprising a timing advance offset for the second access node. In an example phase 602 comprises receiving a handover command for handover of the communications device from a source cell to a target cell, said handover command comprising a timing advance offset for the target cell.

[0081] Phase 604 comprises determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node. In an example phase 604 comprises determining a target cell TA for the communications device on the basis of a source cell TA of the communications device, the received timing advance offset for the target cell and a downlink observed time difference between the source cell and the target cell.

[0082] In an example according to at least some embodiments, in phase 602, the timing advance offset comprises a difference between a zero-distance TA of the first access node and the zero-distance TA of the second access node.

[0083] In an example according to at least some embodiments, phases 602 to 604, at least the second access node timing advance, is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

[0084] In an example according to at least some embodiments, phase 604 comprises communicating with the second access node using the determined second access node timing advance. In an example phase 604 comprises sending a handover confirmation to the second access node using the second access node TA.

[0085] In an example according to at least some embodiments, phase 603 comprises that the timing advance offset comprises a difference between a zero-distance TA of the first access node and the zero-distance TA of the second access node.

[0086] Fig. 7 illustrates a sequence in accordance with at least some embodiments of the present invention. The sequence is illustrated for a RACH-less handover of a communications device from a source cell of a source base station (SBTS) to a target cell of a target base station (TBTS). The sequence may be performed in connection with a method described with Fig. 5 and Fig. 6.

[0087] Phase 702 comprises the communications device (UE) establishing a connection with the SBTS. Therefore, the UE may have a timing advance for the SBTS. The communications device may perform observed time difference (OTD) measurements, when connected to the SBTS. An OTD measurement performed by the communications device provides a downlink OTD. The downlink OTD defines a time difference between receive timings of downlink transmissions from the SBTS and TBTS.

[0088] In an example according to at least some embodiments, phase 704 comprises reporting the OTD measurements to the SBTS. The OTD measurements may be reported for example, when a target cell TA is not determined at the communications device. In such a case the target cell TA may be determined at a network node, for example the TBTS, and communicated to the communications device included in a handover command. However, in an example according to at least some embodiments, phase 704 and reporting the OTD measurements may be omitted if the target cell TA is determined at the communications device. [0089] Phase 706 comprises the SBTS determining that a handover of the communications device is needed.

[0090] Phase 708 comprises the SBTS sending a handover request to the TBTS. In an example according to at least some embodiments, the handover request comprises information indicating a reference TA setting characteristic to the source cell. In an example according to at least some embodiments, the handover request further comprises communications device specific TA information.

[0091] Phase 710 comprises the TBTS accepting the handover request.

[0092] In an example in accordance with at least some embodiments, phase 712 comprises the TBTS determining a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell. Phase 714 comprises the TBTS sending a handover request response to the SBTS, the handover request response comprising the determined timing advance offset.

[0093] In an example in accordance with at least some embodiments, phase 712 comprises, wherein the handover request in phase 708 further comprises communications device specific TA information, the TBTS determining a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell, and the TBTS is caused to determine a target cell TA for the communications device on the basis of the communications device specific TA information and the determined timing advance offset. Phase 714 comprises the TBTS sending a handover request response to the SBTS, the handover request response comprising the target cell TA of the communications device.

[0094] Phase 716 comprises the SBTS sending a handover command to the communications device. The handover command is established on the basis of the handover request response received from the TBTS in phase 714. [0095] In an example according to at least some embodiments, in phase 716, the handover command comprises the timing advance offset determined at the TBTS and phase 718 comprises determining at the communications device a target cell TA on the basis of the timing advance offset received in the handover command. [0096] In an example according to at least some embodiments, in phase 716, the handover command comprises the target cell TA determined at the TBTS and phase 718 comprises determining at the communications device the target cell TA to be the target cell TA received in the handover command. [0097] Phase 720 comprises sending a handover confirmation to the TBTS using the target cell TA determined in phase 718. In this way the TBTS may learn that the communications device is configured for communications with the TBTS and the TBTS may determine that the handover procedure is completed.

[0098] Phase 722 comprises the communications device being connected with the TBTS and using the TA determined in phase 718 for uplink communications of user data. It should be appreciated that the communications device may receive from the TBTS one or more adjustments for adjusting the target cell TA determined in phase 718. In this way, the TA used by the communications device may be adapted to movement of the communications device to different distances from the TBTS. [0099] In an example according to at least some embodiments, phase 720 comprises the communications device initiating communications with the second access node using the second access node timing advance. In an example, the communications [0100] Fig. 8 illustrates an example of an apparatus in accordance with at least some embodiments of the present invention. The apparatus may be a radio access node or a communications device or a part of a radio access node or a communications device.

[0101] The apparatus comprises a processor 802 and a transceiver 804. The processor is operatively connected to the transceiver for controlling the transceiver. The apparatus may comprise a memory 806. The memory may be operatively connected to the processor. It should be appreciated that the memory may be a separate memory or included to the processor and/or the transceiver.

[0102] According to an embodiment, the processor is configured to control the transceiver and/or to perform one or more functionalities described with a method according to an embodiment.

[0103] Fig. 9 illustrates an example of a sequence in accordance with at least some embodiments of the present invention. The sequence describes determining a timing advance in connection with DC. Phase 902 comprises the UE establishing a connection with a primary BTS. Therefore, the UE may have a timing advance for the primary BTS. Phase 904 comprises the UE reporting OTD measurements performed by the UE to the primary BTS. The OTD measurements may be reported for example, when a target cell TA is not determined at the UE. In such a case the target cell TA may be determined at a network node, for example a secondary BTS, and communicated to the UE included in a message, for example an RRC reconfiguration message. However, in an example according to at least some embodiments, phase 904 and reporting the OTD measurements may be omitted if the target cell TA is determined at the UE. [0104] Phase 906 comprises the primary BTS determining to setup DC for the UE. In DC the UE is connected to more than one BTS that may be referred to a primary BTS and a secondary BTS. Accordingly, it should be appreciated that before the DC is established for the UE, the primary BTS may be simply referred to a BTS or a serving BTS.

[0105] Phase 908 comprises the primary BTS sending a secondary node addition request to a secondary BTS. In an example according to at least some embodiments, the secondary node addition request comprises information indicating a reference TA setting characteristic to a source cell. The source cell may be a cell of the primary BTS serving the UE. It should be appreciated that also other names for the source cell may be used. In an example according to at least some embodiments, the secondary node addition request comprises UE specific TA information.

[0106] Phase 910 comprises the secondary BTS accepting the secondary node addition request.

[0107] In an example in accordance with at least some embodiments, phase 912 comprises the secondary BTS determining a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell. The target cell may be a cell of the secondary BTS for connecting to the UE. It should be appreciated that also other names for the target cell may be used. Phase 914 comprises the secondary BTS sending a secondary node addition request acknowledgement (ACK) to the primary BTS, the secondary node addition ACK comprising the determined timing advance offset.

[0108] In an example in accordance with at least some embodiments, phase 912 comprises wherein the secondary node addition request in phase 908 further comprises UE specific TA information, the secondary BTS is caused to determine a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell, and to determine a target cell TA for the UE on the basis of the UE specific TA information and the determined timing advance offset. Phase 914 comprises the secondary BTS sending a secondary node addition ACK to the primary BTS, the secondary node addition ACK comprising the target cell TA of the UE.

[0109] Phase 916 comprises the primary BTS sending an RRC reconfiguration request to the UE. The RRC reconfiguration request is established on the basis of the secondary node addition ACK received from the secondary BTS in phase 914.

[0110] In an example according to at least some embodiments, in phase 916, the RRC reconfiguration request comprises the target cell TA determined at the secondary BTS and phase 918 comprises determining at the UE the target cell TA to be the target cell TA received in the RRC reconfiguration request.

[0111] In an example according to at least some embodiments, in phase 916, the RRC reconfiguration request comprises the timing advance offset determined at the secondary BTS. Phase 918 comprises determining at the UE a target cell TA on the basis of the timing advance offset received in the RRC reconfiguration request.

[0112] Phase 920 comprises the UE sending an RRC reconfiguration complete in response to the RRC reconfiguration request. In this way the primary BTS may learn that the UE is configured for DC operation.

[0113] Phase 922 comprises the UE being connected and communicating with the secondary BTS using the target cell TA determined in phase 918 and to the primary BTS using the source cell TA, for uplink communications of user data. It should be appreciated that the UE may receive from the secondary BTS one or more adjustments for adjusting the target cell TA determined in phase 918. In this way, the target cell TA used by the UE may be adapted to movement of the UE to different distances from the secondary BTS.

[0114] Fig. 10 illustrates an example of a sequence in accordance with at least some embodiments of the present invention. The sequence describes determining a timing advance in connection with a BTS comprising multiple transmission and reception points (TRPs), e.g. in connection CoMP/multi-TRP operation with UE. The TRPs may be connected to a central unit of the BTS. In the sequence, a BTS comprises two transmission and reception points: TRP#1 and TRP#2. However, it should be appreciated that the BTS may comprise more than two TRPs. The sequence supports determining a timing advance for a TRP#2 for UE connected to a TRP#1. Here the TRP#1 may provide source cell for the UE and the TRP#2 may provide a target cell for the UE. It should be appreciated that also other naming for the cells of the TRPs may be used. Phase 1002 comprises the UE establishing a connection with the TRP#1. Therefore, the UE may have a timing advance for the TRP#1. Phase 1004 comprises the UE reporting OTD measurements performed by the UE to the TRP#1. The OTD measurements may be reported for example, when a target cell TA is not determined at the UE. In such a case the target cell TA may be determined at a network node, for example the BTS, and communicated to the UE included in a message, for example an RRC reconfiguration message. However, in an example according to at least some embodiments, phase 1004 and reporting the OTD measurements may be omitted if the TRP#2 TA is determined at the UE.

[0115] Phase 1006 comprises the BTS determining to initiate multiple wireless links between the BTS and the UE. In other words, the BTS may determine to initiate CoMP/multi- TRP operation with the UE. Accordingly, it should be appreciated that before the CoMP/multi- TRP operation is configured for the UE, the UE may be connected to one cell that is provided by the TRP#1, which may be simply also referred to a TRP since there is only one TRP serving the UE. Phase 1008 comprises the BTS preparing the TRP#2.

[0116] In an example in accordance with at least some embodiments, phase 1010 comprises the BTS determining a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell and phase 1012 comprises sending an RRC reconfiguration request to the UE. The RRC reconfiguration request comprises the determined timing advance offset for the target cell.

[0117] In an example in accordance with at least some embodiments, phase 1010 comprises the BTS determining a timing advance offset for the target cell, on the basis of the TA setting characteristic to the source cell and the TA setting characteristic to the target cell, and the BTS is caused to determine a target cell TA for the UE on the basis of the UE specific TA information and the determined timing advance offset, and phase 1012 comprises sending an RRC reconfiguration request comprising the determined timing advance offset for the target cell to the UE. [0118] In an example in accordance with at least some embodiments, phase 1014 comprises determining at the UE the target cell TA on the basis of the timing advance offset received in the RRC reconfiguration request. Phase 1016 comprises the UE sending an RRC reconfiguration complete in response to the RRC reconfiguration request. In this way the BTS may learn that the UE is configured for CoMP/Multi-TRP operation. [0119] In an example according to at least some embodiments, in phase 1012, the RRC reconfiguration request comprises the target cell TA determined at the BTS and phase 1014 comprises determining at the UE the target cell TA to be the target cell TA received in the RRC reconfiguration request. [0120] Phase 1018 comprises the UE being connected and communicating with the TRP#2 using the target cell TA determined in phase 1018 and to the TRP#1 using the source cell TA, for uplink communications of user data. It should be appreciated that the UE may receive from the BTS, via the TRP#1 and TRP#2, one or more adjustments for adjusting the target cell TA determined in phase 1014. In this way, the target cell TA used by the UE may be adapted to movement of the UE to different distances from the TRP#2.

[0121] A memory may be a computer readable medium that may be non-transitory. The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture, as non-limiting examples. Examples

Examples 1 to 22:

1. An apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determine a reference timing advance setting characteristic to the second access node; determine a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and send a communications device a second message comprising the determined timing advance offset, or wherein the first message further comprises communications device specific timing advance information, the apparatus is caused to: determine a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and send a communications device a second message comprising the second access node timing advance of the communications device.

2. The apparatus according to claim 1, wherein the communications device specific timing advance information comprises a first access node timing advance of the communications device and a downlink observed time difference between the first access node and the second access node.

3. The apparatus according to example 1 or 2, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node.

4. The apparatus according to example 1, 2 or 3, wherein the apparatus is caused to: determine, if the fist access node and the second access node are not synchronized, a transmission time difference of the first access node and the second access node and determining the second access node timing advance, where the transmission time difference between the second access node and first access node is compensated.

5. The apparatus according to any of examples 1 to 4, wherein the timing advance offset for the second access node is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

6. An apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; determine a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node. The apparatus according to example 6, wherein the apparatus is caused to: communicating with the second access node using the determined second access node timing advance. The apparatus according to example 6 or 7, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node. The apparatus according to any of examples 6 to 8, wherein the second access node timing advance is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation. A method comprising: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and sending a communications device a second message comprising the determined timing advance offset, or wherein the first message further comprises communications device specific timing advance information, determining a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and sending a communications device a second message comprising the second access node timing advance of the communications device. 11. The method according to example 10, wherein the communications device specific timing advance information comprises a first access node timing advance of the communications device and a downlink observed time difference between the first access node and the second access node.

12. The method according to example 10 or 11, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node.

13. , The method according to any of examples 10 to 12, comprising: determining, if the fist access node and the second access node are not synchronized, a transmission time difference of the first access node and the second access node and determining the second access node timing advance, where the transmission time difference between the second access node and first access node is compensated.

14. The method according to any of examples 10 to 13, wherein the timing advance offset for the second access node is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

15. A method comprising: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

16. The method according to example 15, comprising: communicating with the second access node using the determined second access node timing advance. 17. The method according to example 15 or 16, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node.

18. The method according to any of examples 15 to 17, wherein the second access node timing advance is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

19. A computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node , on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and sending a communications device a second message comprising the determined timing advance offset, or wherein the first message further comprises communications device specific timing advance information, determining a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and sending a communications device a second message comprising the second access node timing advance of the communications device. 20. A computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

21. A non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node , on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and sending a communications device a second message comprising the determined timing advance offset, or wherein the first message further comprises communications device specific timing advance information, determining a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and sending a communications device a second message comprising the second access node timing advance of the communications device.

22. A non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

[0122] Embodiments may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "memory" or "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0123] Reference to, where relevant, "computer-readable storage medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single/multi-processor architectures and sequencers/parallel architectures, but also specialized circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices and other devices. References to computer readable program code means, computer program, computer instructions, program instructions, instructions, computer code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device as instructions for a processor or configured or configuration settings for a fixed function device, gate array, programmable logic device, etc.

[0124] Although the above examples describe embodiments of the invention operating within a wireless device or a gNB, it would be appreciated that the invention as described above may be implemented as a part of any apparatus comprising a circuitry in which radio frequency signals are transmitted and/or received. Thus, for example, embodiments of the invention may be implemented in a mobile phone, in a base station, in a computer such as a desktop computer or a tablet computer comprising radio frequency communication means (e.g. wireless local area network, cellular radio, etc.).

[0125] It should be appreciated that in the above description the term receiving, for example obtaining information, data, a grant, a message or a random access message a random access message, may in some examples comprise acquiring for example by receiving information, data, a grant, a message or a random access message. [0126] In general, the various embodiments of the invention may be implemented in hardware or special purpose circuits or any combination thereof. While various aspects of the invention may be illustrated and described as block diagrams or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods 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.

[0127] Embodiments of the inventions may be practiced in various components such as integrated circuit modules, field-programmable gate arrays (FPGA), application specific integrated circuits (ASIC), microcontrollers, microprocessors, a combination of such modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0128] Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication. [0129] As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analogue and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analogue and/or digital hardware circuit(s) with software/firmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. [0130] 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. [0131] The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.

Claims

1. An apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determine a reference timing advance setting characteristic to the second access node; determine a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

- wherein the first message further comprises communications device specific timing advance information, the apparatus is caused to: determine a second access node timing advance for the communications device on the basis of the communications device specific timing advance information and the determined timing advance offset; and send a communications device a second message comprising the second access node timing advance of the communications device.

3. The apparatus according to claim 1 or 2, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node.

4. The apparatus according to claim 1, 2 or 3, wherein the apparatus is caused to: determine, if the fist access node and the second access node are not synchronized, a transmission time difference of the first access node and the second access node and determining the second access node timing advance, where the transmission time difference between the second access node and first access node is compensated.

5. The apparatus according to any of claims 1 to 4, wherein the timing advance offset for the second access node is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

6. An apparatus comprising: one or more processors, and memory storing instructions that, when executed by the one or more processors, the apparatus is caused to: receive a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determine a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

7. The apparatus according to claim 6, wherein the apparatus is caused to: communicating with the second access node using the determined second access node timing advance.

8. The apparatus according to claim 6 or 7, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node.

9. The apparatus according to any of claims 6 to 8, wherein the second access node timing advance is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

10. A method comprising: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node, on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

11. The method according to claim 10, wherein the communications device specific timing advance information comprises a first access node timing advance of the communications device and a downlink observed time difference between the first access node and the second access node .

12. The method according to claim 10 or 11, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node .

13. , The method according to any of claims 10 to 12, comprising: determining, if the fist access node and the second access node are not synchronized, a transmission time difference of the first access node and the second access node and determining the second access node timing advance, where the transmission time difference between the second access node and first access node is compensated.

14. The method according to any of claims 10 to 13, wherein the timing advance offset for the second access node is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

15. A method comprising: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.

16. The method according to claim 15, comprising: communicating with the second access node using the determined second access node timing advance.

17. The method according to claim 15 or 16, wherein the timing advance offset comprises a difference between a zero-distance timing advance of the first access node and the zero-distance timing advance of the second access node .

18. The method according to any of claims 15 to 17, wherein the second access node timing advance is determined in connection with a RACH-less handover procedure, coordinated multi-point operation, multiple transmission and reception points operation or dual connectivity operation.

19. A computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message comprising information indicating a reference timing advance setting characteristic to a first access node; determining a reference timing advance setting characteristic to the second access node; determining a timing advance offset for the second access node , on the basis of the reference timing advance setting characteristic to the first access node and the reference timing advance setting characteristic to the second access node; and

20. A computer program comprising computer readable program code means adapted to perform at least the following: receiving a first message from a first access node for initiating communications of a communications device with a second access node, said first message comprising a timing advance offset for the second access node; and determining a second access node timing advance for the communications device on the basis of a first access node timing advance of the communications device, the received timing advance offset for the second access node and a downlink observed time difference between the first access node and the second access node.