Random access procedures

Abstract

According to an example aspect of the present invention, there is provided an apparatus configured to determine, based on respective signal strength measurements, that the apparatus is capable of connecting to a first and to a second transmission reception point, TRP, initiate a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and enter into the connected state with respect to the first and the second TRP.

Description

RANDOM ACCESS PROCEDURESFIELD

[0001] The present disclosure relates to random access processes in cellular communication systems.BACKGROUND

[0002] A user equipment, UE, of a cellular communication system establishes connectivity with a radio-access network, RAN, of the system to access services of the system, such as telephony and Internet connectivity. To enhance stability of the connection to the system and to increase available bandwidth, UEs may connect to more than one network node at the same time. Examples of such network nodes include base stations and transmission reception points, TRPs.SUMMARY

[0003] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0004] According to a first aspect of the present disclosure, there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to determine, based on respective signal strength measurements, that the apparatus is capable of connecting to a first and to a second transmission reception point, TRP, initiate a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connectingto the second TRP is provided to the first TRP, and enter into the connected state with respect to the first and the second TRP.

[0005] According to a second aspect of the present disclosure, there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to transmit, in a cell controlled by the apparatus, reference signals using a first transmission reception point, TRP, of the apparatus, perform a first random access process, using the first TRP, with a user equipment to transition the user equipment to a connected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP, and enter into the connected state with the user equipment with respect to the first TRP.

[0006] According to a third aspect of the present disclosure, there is provided an apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to transmit, in a cell, reference signals using a radio transceiver of the apparatus, the apparatus being a transmission reception point, TRP, exchange radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respect to the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus, and enter into the connected state with the user equipment.

[0007] According to a fourth aspect of the present disclosure, there is provided a method comprising determining, based on respective signal strength measurements, that an apparatus is capable of connecting to a first and to a second transmission reception point, TRP, initiating a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and entering into the connected state with respect to the first and the second TRP.

[0008] According to a fifth aspect of the present disclosure, there is provided a method, comprising transmitting, in a cell controlled by an apparatus, reference signals using a first transmission reception point, TRP, of the apparatus, performing a first random access process, using the first TRP, with a user equipment to transition the user equipment to aconnected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP, and entering into the connected state with the user equipment with respect to the first TRP.

[0009] According to a sixth aspect of the present disclosure, there is provided a method, comprising transmitting, in a cell, reference signals using a radio transceiver of an apparatus, the apparatus being a transmission reception point, TRP, exchanging radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respect to the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus, and entering into the connected state with the user equipment.

[0010] According to a seventh aspect of the present disclosure, there is provided an apparatus comprising means for determining, based on respective signal strength measurements, that an apparatus is capable of connecting to a first and to a second transmission reception point, TRP, initiating a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and entering into the connected state with respect to the first and the second TRP.

[0011] According to an eighth aspect of the present disclosure, there is provided an apparatus comprising means for transmitting, in a cell controlled by an apparatus, reference signals using a first transmission reception point, TRP, of the apparatus, performing a first random access process, using the first TRP, with a user equipment to transition the user equipment to a connected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP, and entering into the connected state with the user equipment with respect to the first TRP

[0012] According to a ninth aspect of the present disclosure, there is provided an apparatus comprising means for transmitting, in a cell, reference signals using a radio transceiver of an apparatus, the apparatus being a transmission reception point, TRP, exchanging radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respectto the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus, and entering into the connected state with the user equipment

[0013] According to a tenth aspect of the present disclosure, there is provided a non- transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least determine, based on respective signal strength measurements, that the apparatus is capable of connecting to a first and to a second transmission reception point, TRP, initiate a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and enter into the connected state with respect to the first and the second TRP.

[0014] According to an eleventh aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least transmit, in a cell controlled by the apparatus, reference signals using a first transmission reception point, TRP, of the apparatus, perform a first random access process, using the first TRP, with a user equipment to transition the user equipment to a connected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP, and enter into the connected state with the user equipment with respect to the first TRP.

[0015] According to a twelfth aspect of the present disclosure, there is provided a non- transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least transmit, in a cell, reference signals using a radio transceiver of the apparatus, the apparatus being a transmission reception point, TRP, exchange radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respect to the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus, and enter into the connected state with the user equipment.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention;

[0017] FIGURE 2A illustrates an example system in accordance with at least some embodiments of the present invention;

[0018] FIGURE 2B illustrates an example system in accordance with at least some embodiments of the present invention;

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

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

[0021] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention;

[0022] FIGURE 6 illustrates signalling in accordance with at least some embodiments of the present invention;

[0023] FIGURE 7 is a flow graph of a method in accordance with at least some embodiments of the present invention;

[0024] FIGURE 8 is a flow graph of a method in accordance with at least some embodiments of the present invention, and

[0025] FIGURE 9 is a flow graph of a method in accordance with at least some embodiments of the present invention.EMBODIMENTS

[0026] Disclosed herein are processes to establish multi-TRP, mTRP, sessions for UEs in a flexible manner. In detail, a UE may find itself in a position where it can initiate connectivity toward more than one TRP, and the UE may trigger random access processes.In these random access, RA, processes, the UE indicates to the network that it can connect also to another TRP than the one with which the RA process is being conducted. This indication that also another TRP is reachable for the UE is a request from the UE to establish an mTRP session. The network may use these indications in establishing an mTRP session, or the network may choose to ignore these indications in case the network decides against establishing an mTRP session. Thus the procedure enables the UE to request an mTRP session without incurring delays, and the network may choose to establish the requested mTRP session or to decline the request, implicitly or explicitly.

[0027] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. This system includes base stations 130, 135 in communication with UEs, such as UE 110. Two radio links connect base station 130 with UE 110. The radio links may be bidirectional, comprising an uplink, UL, to convey information from UE 110 toward base station 130, and a downlink, DL, to convey information from the base station 130 toward UE 110. A cellular communication system may comprise hundreds or thousands of base stations, of which only two are illustrated in FIGURE 1 for the sake of clarity of the illustration. The base stations may be distributed in that they comprise a centralized unit, CU, and one or more distributed unit, DU. A base station is an example of a base node. The DUs may be TRPs, such that base station 130 has plural TRPs and base station 135 has plural TRPs. In case a base station control plural cells, each cell may be furnished with plural TRPs. Physically the TRPs of cells controlled by a same base station may be the same physical units. TRPs of the same cell have a common synchronization signal / physical broadcast channel, SS / PBCH, block which is cell specific.

[0028] Base station 130 is further coupled communicatively with core network node 140, which may comprise, for example, an evolved packet core, EPC, mobility management entity, MME, a home subscriber server, HSS, a 5G unified data repository, UDR, a call session control function, CSCF, or a 5G access and mobility management function, AMF. The core network node 140 may be coupled with further core network nodes, and with a network 150, which may comprise the Internet or a corporate network, for example. The system may communicate with further networks via network 150. Examples of the further core network nodes, which are not illustrated in FIGURE 1 for the sake of clarity, include gateways and subscriber information repositories. Core network nodes may be virtualized in the sense that they may run as software modules on computing substrates, such that more than one virtualized network node may run on a same physical computing substrate. Thenetwork may be configured to function in accordance with a suitable cellular standard such as long term evolution, LTE, fifth generation, 5G, which is also known as New Radio, NR, or sixth generation, 6G standards as defined by the 3rdgeneration partnership project, 3GPP. To obtain interoperation, UEs attaching to the network are configured to support a same standard as the network.

[0029] Base station 130 controls, in the example of FIGURE 1 beams 130A and 130B, of which UE 110 is in the situation illustrated in FIGURE 1 reachable by both beams 130A and 130B, and base station 135 controls, in the example of FIGURE 1, beams 135A and 135B. The number of beams, may be in excess of what is illustrated in FIGURE 1. It is also possible that a base station has a single beam. In particular, the beams of FIGURE 1 may be beams of different TRPs, that is, beam 130A may be controlled by a first TRP of base station 130 and beam 130B may be controlled by a second TRP of base station 130. A mobility event may comprise a switch from one beam to another beam of the same cell, or a switch from one cell to another cell. To support mobility procedures, UEs, including UE 110, are configured to conduct mobility measurements to measure signal strengths of adjacent beams and / or cells, and report results of these measurements to the network, which may then take a decision concerning a mobility event, such as a beam change or a cell switch.

[0030] By a transmission point it is meant a set of geographically co-located transmit antennas, such as an antenna array for one cell or part of one cell. Transmission points may include base station antennas, remote radio heads, or a remote antenna of a base station, for example. One cell may include one or multiple transmission points. For a homogeneous deployment, each transmission point may correspond to one cell. By a reception point it is meant a set of geographically co-located receive antennas, such as an antenna array for one cell or part of one cell. Reception points may include base station antennas, remote radio heads or a remote antenna of a base station, for example. One cell may include one or multiple reception points. For a homogeneous deployment, each reception point may correspond to one cell. A transmission reception point, TRP, is a set of geographically colocated antennas supporting transmission point and reception point functionality.

[0031] Cells are configured to broadcast, for example via a system information block, SIB, such as SIB1, information identifying TRPs of the cell. The broadcast may be performed from each TRP of the cell, and the broadcast may identify either which TRPs of the cell are available for mTRP operation, or that all TRPs of the cell are available for mTRPoperation. Alternatively, the network in which the cell is comprised may be configured so that all TRPs support mTRP operation, in which case the information broadcasted by cells need not indicate this.

[0032] In mTRP operation, a serving cell may schedule the UE from two TRPs, providing better coverage, reliability and / or data rates for physical downlink shared channel, PDSCH, physical downlink control channel, PDCCH, physical uplink shared channel, PUSCH, and physical uplink control channel, PUCCH. There are two different operation modes to schedule mTRP PDSCH transmissions: single-DCI and multi-DCI. For both modes, control of uplink and downlink operation can be done by physical layer and medium access control, MAC, layer, within the configuration provided by the radio resource control, RRC, layer. In single-DCI mode, only one TRP is responsible for the transmission of control data, that is PDCCH, to the UE. As a result, the UE is scheduled by the same PDCCH containing a DCI for both, or all, TRPs of an mTRP session. On the other hand, in multi- DCI mode two, or all, TRPs of the mTRP session are responsible for the transmission of control data to the UE. As a result, the UE is then scheduled by independent DCIs from each TRP.

[0033] Further, there are two different operation modes for single DCI multi-TRP PDCCH, namely PDCCH repetition and system frame number, SFN, based PDCCH transmission. In both modes, the UE can receive two PDCCH transmissions, one from each TRP, carrying the same DCI. In PDCCH repetition mode, the network will transmit and the UE may receive the two PDCCH transmissions carrying the same DCI from two linked search spaces each associated with a different control resource set, CORESET. On the other hand, In SFN based PDCCH transmission mode, the network transmits and the UE may receive the two PDCCH transmissions carrying the same DCI from a single search space or CORESET using different transmission configuration indicator, TCI, states.

[0034] UEs may be in one of plural different RRC states with respect to the network. In detail, an idle state UE the UE has no RRC connection to the network and is not registered to any particular cell. In a connected state, the UE has an active RRC connection with the network, the cell to which the UE belongs to is known and a cell level temporary identity for the device, C-RNTI, is used to identify the UE in the network. In 5G networks, a further inactive state is defined, where the UE has a suspended RRC connection with the network. For example LTE does not have the inactive state. The UE may be in a connected stateseparately as it relates to individual TRPs in that the UE is in a connected state with respect to a specific TRP when an active RRC connection to the UE traverses this TRP. In mTRP sessions, the UE may have separate RRC connections to distinct TRPs at the same time, and thus be in the connected state with respect to both, or all, TRPs at the same time.

[0035] A UE seeking to transition from the idle state to a connected state may do so via a random access, RA, process. An RA process may be a two-step or a four-step process, depending on the used radio access technology and the situation. Before the UE starts a RA procedure, it first synchronizes to a downlink transmission of the network. The UE obtains time and frequency synchronization of the cell by decoding synchronization signal blocks, SS / PBCHs. The UE then measures the reference signal received power, RSRP, from the SS / PBCH blocks being transmitted by the cell. In case the RSRP of a beam transmitting SS / PBCH is higher than configured threshold, the UE may consider this beam as one the UE is capable of connecting to. A physical random access channel, PRACH, occasion to use for preamble transmission is determined based a mapping from SS / PBCH to PRACH occasions.

[0036] A four-step RA process is illustrated in Table 1 :Table 1 : four-step RA process

[0037] As a result of a RA process, whether a 4-step process according to Table 1 or a 2-step process, the UE will be in a connected state with respect to the network, NW. The2- step RA process is similar to a 4-step RA process described above, where msgl and msg3 are combined in a msgA and sent out without waiting for feedback from the UE. Similarly, the NW combines msg2 and msg4 into an msgB. In terms of an mTRP session, the UE will conduct a RA process with a TRP to transition to the connected state with respect to that TRP. To transition to the connected state with respect to another TRP as well, the UE in principle needs to perform a RA process with the other TRP as well. Concerning performing the RA process, as RA processes involve exchanging messages between the TRP and the UE, both the UE and the TRP participate in the RA process. From the point of view of the UE, it performs the RA process with the TRP, and from the point of view of the TRP, it performs the RA process with the UE. A RA process may be initiated by either the UE or the TRP, when the UE initiates the RA process, it does do by transmitting the RA preamble to the TRP.

[0038] For 6G, the network is expected to cater to a higher connection density, enhanced user experience, higher peak data throughput as well as lower latency. New bands in the 7-15GHz frequency range have been identified for 6G operation. The lower bands of this spectrum range will in all likelihood have similar characteristics as frequency range 1 of NR. As a result, the UEs as well as base stations of 6G are also envisaged to use architectures where transmission beams are associated with wide but directional antenna radiation patterns with high number of transmission beams especially at the network side. Network deployments for 6G are expected to use the same site grid as the existing 5G mid-band deployments as network operators will capitalize on the existing network infrastructure already in place in urban macro sites. Current RA processes enable a UE to be synchronized in the uplink to a single TRP. This means that during initial access, a m-TRP capable UE first performs random access to a single TRP and then in subsequent RRC signaling steps following the initial RA procedure connectivity is extended to another TRP. This involves additional RRC signaling overhead slowing down the start of mTRP operation.

[0039] With 6G being expected to cater to higher number of UEs which are foreseen to have advanced capabilities compared to UEs available today, site densification may happen in urban macro sites with more TRPs per site, creating opportunities for mTRP sessions. Taking all these factors into account, it is sought that the UE would be able to connect to multiple TRPs during an initial RA process due to which mTRP operation may start as soon as possible. Very fast access to network resources is a design driver for 6G.

[0040] Herein are described processes whereby a UE which can perform RA to plural TRPs during an initial RA process informs the network about which TRPs it can receive signals from. The network can respond to this information by starting a mTRP session as soon as possible after finishing the RA process.

[0041] Since 6G UEs are expected to have more advanced capabilities, the UE may be capable of mTRP operation, performing two RA processes partially or fully overlapped with each other, or in rapid succession, monitoring two type 1 common search space PDCCH channels, maintaining two TAs, and maintaining two separate power control loops at the same time. The two, or plural, TAs are maintained to the two, or plural, TRPs in an mTRP session, since the UEs distance from the TRPs is likely to differ, it being likelier that the UE is closer to one TRP than the UE being at the same distance from each TRP.

[0042] The cell broadcasts, in one or more system information blocks, information identifying TRPs which can be used for an mTRP session - unless the network is configured so that all TRPs may be used in mTRP. These TRPs may be of the cell itself, or at least one TRP of the cell and at least one TRP of a neighboring cell. The UE measures the RSRP of at least two TRPs identified in the broadcasted information as suitable for an mTRP session and deduces which ones it can use for mTRP operation from its present location.

[0043] When performing a RA process with one of these TRPs, the UE indicates, for example in msg3, that it is capable of communicating with another mTRP-suitable TRP as well. This indication may be a simple indication in msg3 that the UE can receive signals from at least two TRPs. Alternatively, the UE may include in the RA process an identity or identifier of the TRP with which the UE can communicate in addition to the one with which it is performing the RA process. Yet further, the indication may include a signal strength measurement of the other TRP in addition to its identity or identifier. The indication is a request for an mTRP session with the TRP with which the UE is performing the RA process, and the other TRP indicated as one with which the UE can communicate.

[0044] The cell with which the UE is performing the initial RA process may request the UE to provide additional information in subsequent RRC messages which are a part of the initial RA process. Examples of this additional information include the signal strength value of the other TRP in case it wasn’t sent earlier, and information of UE capabilities relevant to mTRP such as single or multi-DCI support and group-based beam reporting. As an alternative, the cell may also indicate if the UE needs to send subsequent messages aboutm-TRP operation to all the TRPs or to only one TRP. The request for additional information may be included in msg4, for example, and the additional information itself may be provided in msg5, for example.

[0045] The network can enable an mTRP session either via lower layer signaling such as DCI or MAC, or use RRC signaling. This procedure will enable a UE to receive from m- TRPs as soon as the first RA process is complete, thereby reducing the need for additional signaling after the first RA process for enabling the m-TRP operation, thus yielding a technical effect and benefit. In case the network chooses to deny the request for mTRP, it may simply not enable the mTRP session, amounting to an implicit denial. On the other hand the network may provide in indication, for example in DCI, MAC or RRC signalling, that mTRP will not be applied in case the mTRP request is denied.

[0046] FIGURE 2A illustrates an example system in accordance with at least some embodiments of the present invention. Like numbering denotes like structure as in FIGURE 1. In this example, UE 110 is in an mTRP session with two TRPs 215, 217 of a same cell, controlled by a base station which comprises CU 210 and TRPs 215, 217 as DUs. The UE is attached with beam 215 A of TRP 215 and beam 217B of TRP 217.

[0047] FIGURE 2B illustrates an example system in accordance with at least some embodiments of the present invention. Like numbering denotes like structure as in FIGURES 1 and 2A. In this example, UE 110 is in an mTRP session with two TRPs 215, 227 of two different cells. In detail, a first base station comprises CU 210 and TRP 215 as a DU, and a second base station comprises CU 220 and TRP 227 acting as DU. The UE is attached with beam 215 A of TRP 215 and beam 227B of TRP 227. Here CUs 210, 220 are connected with each other with an inter-base station interface 2Xn, over which information concerning the mTRP session may be exchanged.

[0048] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 300, which may comprise, for example, a mobile communication device such as UE 110 of FIGURE 1. In applicable parts, FIGURE 3 may also illustrate a TRP or a base station. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a singlecore processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. When processor 310 comprises morethan one processor, device 300 may be a distributed device wherein processing of tasks takes place in more than one physical unit. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. A processing core or processor may be, or may comprise, at least one qubit. Processor 310 may comprise at least one Qualcomm Snapdragon and / or Intel Atom processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise at least one field-programmable gate array, FPGA. Processor 310, optionally together with memory and computer instructions, may be means for performing method steps in device 300, such as determining, initiating, entering, transmitting and performing. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0049] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analogue and / or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analogue and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a UE, TRP or base station, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0050] 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.

[0051] Device 300 may comprise memory 320. Memory 320 may comprise randomaccess memory and / or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may be a computer readable medium. Memory 320 may comprise solid- state, magnetic, optical and / or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and / or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part external to device 300 but accessible to device 300. Memory 320 may be transitory or non-transitory. The term “non-transitory”, as used herein, is a limitation of the medium itself (that is, tangible, not a signal) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM).

[0052] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and / or receiver 340 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, 5G, long term evolution, LTE, IS-95, wireless local area network, WLAN, Ethernet and / or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0053] Device 300 may comprise a near-field communication, NFC, transceiver 350. NFC transceiver 350 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0054] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker or a microphone. A user may be able to operate device 300 via UI 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 oron a cloud accessible via transmitter 330 and receiver 340, or via NFC transceiver 350, and / or to play games.

[0055] Device 300 may comprise or be arranged to accept a user identity module 370. User identity module 370 may comprise, for example, a subscriber identity module, SIM, card installable in device 300. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and / or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0056] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0057] Device 300 may comprise further devices not illustrated in FIGURE 3. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the frontfacing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some embodiments, device 300 lacks at least one device described above. For example, some devices 300 may lack a NFC transceiver 350 and / or user identity module 370.

[0058] Processor 310, memory 320, transmitter 330, receiver 340, NFC transceiver 350, UI 360 and / or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300,to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0059] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left and centre, serving TRPs 1 and 2, and on the right, a UE. Time advances from the top toward the bottom.

[0060] In phases 410 and 420 the UE transmits RA preambles to TRPs 1 and 2, respectively. This takes place using respective RA occasions and the preamble need not be the same for the two TRPs, indeed there are in FIGURE 4 two distinct RA processes proceeding concurrently.

[0061] Phase 430 is a RA response from TRP1, namely msg2, comprising the TA to TRP1, UL grant for transmitting to TRP1 and a temporary C-RNTI, as described herein above. Phase 440 is a RA response, namely msg2, from TRP2 to the UE, comprising the TA to TRP2, an UL grant for transmitting to TRP2 and a temporary C-RNTI.

[0062] Phase 450 is an RRC connection setup request, namely msg3, from the UE to TRP1. This message comprises the indication that the UE is capable of connecting to TRP2 as well. Phase 460 is an RRC connection setup request, namely msg3, from the UE to TRP2. This message comprises the indication that the UE is capable of connecting to TRP1 as well. Thus both TRPs are informed of the opportunity for mTRP in an early phase. The indication may be an indication that the UE has a RSRP measurement result concerning the other TRP.

[0063] Phases 470 and 480 are contention resolution messages, namely msg4 messages, from TRP1 and TRP2, respectively. These messages may be addressed using the respective C-RNTIs and comprise UL grants for msg5 messages, and, optionally, requests for additional mTRP related information, such as indications whether the UE supports single or multi-DCI support or group-based beam reporting.

[0064] In phase 490 the UE sends a msg5 message comprising a HARQ acknowledgement to TRP1, and in phase 4100 the UE sends a msg5 to TRP2, comprising an RRC setup complete indication, which may comprise the additional information if such was requested in phase 470.

[0065] In phase 4110 the UE sends a msg5 message comprising a HARQ acknowledgement to TRP2, and in phase 4120 the UE sends a msg5 to TRP2, comprising an RRC setup complete indication, which may comprise the additional information if such was requested in phase 480.

[0066] In phases 4130 and 4140 TRP1 and TRP2, respectively, transmit to the UE RRC re-configuration messages, which the UE acknowledges with RRC reconfiguration complete messages to TRP1 and TRP2, respectively, in phases 4150 and 4160. As a result of the process of FIGURE 4, the UE is in the connected state with respect to both TRP1 and TRP2 and can exchange mTRP data with both TRPs.

[0067] It should be emphasized that the messages of FIGURE 4 need not take phase in specifically the order illustrated, rather, for example, the RA processes with TRP1 and TRP2 may overlap to a smaller degree than illustrated in FIGURE 4. For example, the UE may send message 420 only after receiving message 470 from TRP1. Indeed in some cases one of these RA processes may conclude before the other begins, however they should be conducted within a reasonable time of each other, in particular with respect to a speed at which the UE is moving, since the process only makes sense if the RSRP measurements conducted are still relevant for both TRPs, and thus the conclusion that both TRPs are reachable, is still valid. If the UE is stationary this time is long, whereas if the UE moves it is the shorter the faster is the UE speed.

[0068] Yet further, in some embodiments three TRPs are involved, rather than two, wherein the UE indicates in a RA process to a first TRP from among the three that it can communicate with the two others. The end result is that the UE is in the connected state with respect to all three TRPs.

[0069] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention. The process resembles that of FIGURE 4, and like numbering denotes like content as in FIGURE 4. Time advances from the top toward the bottom.

[0070] In detail, in the embodiment of FIGURE 5, the RRC setup complete, RRC reconfiguration and RRC reconfiguration complete phases are only performed with one TRP. The message sent to the single TRP has the corresponding information for both TRPs. Information about which TRP to send these messages to, may be transmitted to the UE inmsg4, for example. The HARQ ACK msg5 490, 4110 may be sent from the UE to both TRPs or may be sent to only one TRP.

[0071] In detail, in terms of FIGURE 5, the HARQ ACK is here sent in the msg5 stage to both TRPs in phases 490 and 4110 as in FIGURE 4. However the RRC setup complete message is sent only to TRP1 as phase 5100, such that this message comprises in its payload also the RRC setup complete message intended to TRP2. TRP1 provides the RRC setup complete message intended to TRP2 to TRP2 via a backhaul connection.

[0072] The RRC reconfiguration message is sent from TRP1 to UE in phase 5130, this message comprising as payload also the RRC reconfiguration message from TRP2, obtained in TRP1 over the backhaul connection. Finally, the RRC reconfiguration complete messages for both TRPs are sent from the UE in phase 5150 to TRP1, with TRP1 again forwarding the content intended to TRP2 to TRP2 via the backhaul connection. If the HARQ ACKs 490, 4110 are only sent to TRP1, TRP1 will forward the HARQ ACK message of TRP2 to TRP2.

[0073] FIGURE 6 illustrates signalling in accordance with at least some embodiments of the present invention. The process resembles that of FIGURE 4, and like numbering denotes like content as in FIGURE 4. Time advances from the top toward the bottom.

[0074] The embodiment of FIGURE 6 is a case where the TRPs TRP1 and TRP2 are part of a same timing advance group, TAG. The fact the TRPs are comprised in a same TAG may be communicated in the broadcasted SIB the UE can decode before starting a RA process. TRPs which are a part of the TAG are broadcast by the base station in a signaling block. The UE indicates, in this embodiment, in msg3, that is a RRC setup request, that it can receive from the other TRP as well and thus the UE requests the mTRP session including also TRP2. This procedure will require UE to only send and receive initial messages with one TRP prior to RRC reconfiguration.

[0075] Phase 610 is the transmission of the preamble, phase 520 the RA response message msg2 with TA, UL grant and temporary C-RNTI. Phase 630 is the RRC setup request, msg3, with the indication that also TRP2 is reachable from the UE, forming the request for mTRP with TRP1 and TRP2. Phase 640 is the msg4, where TRP1 may request additional information, and phases 650 and 660 the HARQ ACK and RRC setup complete, where the UE may provide any additional information if such is requested in phase 640. Phases 670 and 680 are the RRC reconfiguration message and the RRC reconfigurationcomplete message. Following phase 680, the UE is in the connected state with respect to both TRPs. As TRPs of a TAG are co-located, the same TA may be used for both of them.

[0076] FIGURE 7 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in UE 110, or in a control device configured to control the functioning thereof, when installed therein.

[0077] Phase 710 comprises determining, based on respective signal strength measurements, that an apparatus is capable of connecting to a first and to a second transmission reception point, TRP. Phase 720 comprises initiating a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP. Phase 730 comprises entering into the connected state with respect to the first and the second TRP. Phase 730 comprises completing the random access process with the first TRP. In phase 730 the apparatus is in the connected state with respect to the first and the second TRP at the same time.

[0078] FIGURE 8 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in a base station, or in a control device configured to control the functioning thereof, when installed therein.

[0079] Phase 810 comprises transmitting, in a cell controlled by an apparatus, reference signals using a first transmission reception point, TRP, of the apparatus. Phase 802 comprises performing a first random access process, using the first TRP, with a user equipment to transition the user equipment to a connected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP. Phase 830 comprises entering into the connected state with the user equipment with respect to the first TRP.

[0080] FIGURE 9 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in a TRP, or in a control device configured to control the functioning thereof, when installed therein.

[0081] Phase 910 comprises transmitting, in a cell, reference signals using a radio transceiver of an apparatus, the apparatus being a transmission reception point, TRP. Phase 920 comprises exchanging radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respect to the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus. Finally, phase 930 comprises entering into the connected state with the user equipment.

[0082] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0083] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0084] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0085] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., toprovide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0086] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0087] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

[0088] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.INDUSTRIAL APPLICABILITY

[0089] At least some embodiments of the present invention find industrial application in cellular networking.ACRONYMS LISTDCI downlink control informationHARQ hybrid automatic repeat requestMAC medium access control mTRP multiple transmission reception pointNW networkPDU packet data unitRRC radio resource controlTRP transmission reception point

Claims

CLAIMS:

1. An apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:- determine, based on respective signal strength measurements, that the apparatus is capable of connecting to a first and to a second transmission reception point, TRP;- initiate a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and- enter into the connected state with respect to the first and the second TRP.

2. The apparatus according to claim 1, further configured to initiate a second random access process to transition to a connected state with respect to the second TRP, wherein in the second random access process an indication that the apparatus is capable of connecting to the first TRP is provided to the second TRP.

3. The apparatus according to claim 2, wherein the apparatus is configured to initiate the second random access process before the first random access process ends.

4. The apparatus according to claim 3, wherein the apparatus is configured to initiate the second random access process before transmitting a radio resource control connection setup complete message of the first random access process.

5. The apparatus according to any of claims 2 - 3, wherein the apparatus is configured to include the indication that the apparatus is capable of connecting to the second TRP in a radio resource control connection setup request message of the first random access process, and to include the indication that the apparatus is capable of connecting to the first TRP in a radio resource control connection setup request message of the second random access process.

6. The apparatus according to any of claims 2 - 5, configured to transmit data of a radio resource control setup complete message of the second random access process in a radio resource control setup complete message of the first random access process.

7. The apparatus according to claim 6, configured to receive data of a radio resource control reconfiguration message of the second random access process in a radio resource control reconfiguration message of the first random access process and to transmit data of a radio resource control reconfiguration complete message of the second random access process in a radio resource control reconfiguration complete message of the first random access process.

8. The apparatus according to any of claims 1 - 7, wherein the indication that the apparatus is capable of connecting to the second TRP comprises an indication, in a message 3 of the first random access process, indicating the apparatus has a measurement result concerning the second TRP, and the apparatus is configured to send an indication the apparatus has a measurement result concerning the first TRP in a message 3 of the second random access process.

9. The apparatus according to claim 8, further configured to provide the measurement result concerning the second TRP in the first random access process and to provide the measurement result concerning the first TRP in the second random access process.

10. The apparatus according to claim 1, wherein responsive to the first and second TRPs being of a same timing advance group, the apparatus is configured to perform the entering into the connected state with respect to the first and the second TRP without performing a random access process with the second TRP.

11. The apparatus according to claim 10, further configured to send in a message 3 of the first random access process an indication the apparatus has a measurement result concerning the second TRP.

12. The apparatus according to claim 11, further configured to provide the measurement result concerning the second TRP in the first random access process.

13. The apparatus according to any of claims 1 - 12, further configured to receive from a cell where the first and the second TRP are comprised a broadcasted indication of TRPs suitable for multi-TRP use, the broadcasted indication comprising identities of the first and the second TRP.

14. An apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:- transmit, in a cell controlled by the apparatus, reference signals using a first transmission reception point, TRP, of the apparatus;- perform a first random access process, using the first TRP, with a user equipment to transition the user equipment to a connected state with respect to the first TRP, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the first TRP, and- enter into the connected state with the user equipment with respect to the first TRP.

15. The apparatus according to claim 14, wherein the apparatus comprises the second TRP and the apparatus is further configured to perform a second random access process, using the second TRP, with the user equipment to transition the user equipment to a connected state with respect to the second TRP, wherein in the second random access process an indication that the user equipment is capable of connecting to the first TRP is received in the second TRP, and the apparatus is configured to enter into the connected state with the user equipment with respect to the second TRP.

16. The apparatus according to claim 14, wherein the apparatus comprises the second TRP, the first and second TRPs being of a same timing advance group, and the apparatus is further configured to enter into the connected state with the user equipment with respect to the second TRP without performing a random access process with user equipment using the second TRP.

17. An apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:- transmit, in a cell, reference signals using a radio transceiver of the apparatus, the apparatus being a transmission reception point, TRP;- exchange radio messages of a first random access process, using the radio transceiver, with a user equipment whereby the user equipment transitions to a connected state with respect to the apparatus, wherein in the first random access process an indication that the user equipment is capable of connecting to a second TRP is received in the apparatus, and- enter into the connected state with the user equipment.

18. A method comprising:- determining, based on respective signal strength measurements, that an apparatus is capable of connecting to a first and to a second transmission reception point, TRP;- initiating a first random access process to transition to a connected state with respect to the first TRP, wherein in the first random access process an indication that the apparatus is capable of connecting to the second TRP is provided to the first TRP, and- entering into the connected state with respect to the first and the second TRP.

19. The method according to claim 18, further comprising initiating a second random access process to transition to a connected state with respect to the second TRP, wherein in the second random access process an indication that the apparatus is capable of connecting to the first TRP is provided to the second TRP.

20. The method according to claim 19, wherein the method comprises initiating the second random access process before the first random access process ends.

21. The method according to claim 20, wherein the method comprises initiating the second random access process before transmitting a radio resource control connection setup complete message of the first random access process.

22. The method according to any of claims 19 - 20, wherein the method comprises including the indication that the apparatus is capable of connecting to the second TRP in a radio resource control connection setup request message of the first random access process, andincluding the indication that the apparatus is capable of connecting to the first TRP in a radio resource control connection setup request message of the second random access process.

23. The method according to any of claims 19 - 21, comprising transmitting data of a radio resource control setup complete message of the second random access process in a radio resource control setup complete message of the first random access process.

24. The method according to claim 23, comprising receiving data of a radio resource control reconfiguration message of the second random access process in a radio resource control reconfiguration message of the first random access process and transmitting data of a radio resource control reconfiguration complete message of the second random access process in a radio resource control reconfiguration complete message of the first random access process.

25. The method according to any of claims 18 - 24, wherein the indication that the apparatus is capable of connecting to the second TRP comprises an indication, in a message 3 of the first random access process, indicating the apparatus has a measurement result concerning the second TRP, and the method comprises sending an indication the apparatus has a measurement result concerning the first TRP in a message 3 of the second random access process.

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