Patent Description:
In cellular or non-cellular wireless communication, carrier aggregation means combining two or more distinct carriers into one data channel to enhance data transmission capacity for the data channel. The carriers that are combined may be on a same frequency band or on different frequency bands. When on the same band, the carriers may be adjacent to each other in frequency, referred to as contiguous, or non-adjacent, which is referred to as non-contiguous. When the combined carriers are on the same frequency band, the carrier aggregation is intra-band carrier aggregation. On the other hand, when the combined carriers are on different frequency bands, the carrier aggregation is referred to as inter-band carrier aggregation.

<CIT> discloses actions for random access procedures in an LTE-system applying carrier aggregation, in particular to support network-initiated random access on secondary cells. A UE transmits a preamble on a random access channel to a radio base station on a secondary cell and receives or detects a random access response message from the base station including timing advance information for uplink transmission by the UE. The UE can determine the secondary cell that the control information in the random access response message refers to and transmits to the base station based on the timing advance information in the random access response message.

According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims.

In accordance with the present disclosure, an activation delay of carrier aggregation is reduced by conducting transmissions from a user equipment to potential secondary cells already during a connection establishment procedure of the user equipment, rather than waiting until the connection establishment procedure is complete. In other words, establishment of a connection to a primary cell and establishment of a carrier aggregation proceed simultaneously for a user equipment, resulting in an overall reduced delay in obtaining a functional carrier aggregation when starting from an idle or inactive mode. The transmissions from the user equipment may comprise at least one signal transmitted on at least one frequency of at least one candidate secondary cell. The candidate secondary cell frequencies may be on different frequency bands than a frequency band used in the connection establishment procedure, with a primary cell.

<FIG> illustrates an example system in accordance with at least some embodiments of the present invention. The system comprises user equipment, UE, <NUM>, which may comprise, for example, a smartphone, a mobile phone, a tablet computer, a laptop computer, a desktop computer, a machine-type communication node, an Internet of Things node, a sensor or a communication module for an automobile or aircraft.

UE <NUM> is in communication with base station <NUM>. Base station <NUM> may comprise a base station of a cellular or non-cellular wireless communication system. For example, concerning cellular technologies, a base station configured to operate in accordance with long term evolution, LTE, may be referred to as an eNB, while a base station configured to operate in accordance with fifth generation, <NUM>, also known as New Radio, NR, may be referred to as a gNB. On the other hand, concerning non-cellular technologies, for example in worldwide interoperability for microwave access, WiMAX, or wireless local area network, WLAN, a base station may be referred to as an access node. WLAN may be alternatively known as <NUM> or Wi-Fi. The term "base station" is employed in the present disclosure as a terminological choice, with no limitation to either cellular or non-cellular technologies.

Base station <NUM> may be comprised in an overall communication system, which also comprises a core network. A core network is not illustrated in <FIG>. Base station <NUM> is configured to control at least one cell, and in some embodiments, more than one cell. A carrier aggregation may be established using carriers of more than one cell, such that the cells may be controlled by one base station, or by plural base stations. <FIG> illustrates further base stations <NUM>, <NUM> and <NUM>, with which base station <NUM> is enabled to communicate. Such communication may take place over inter-base station links, such as the X2 interface, or via a core network or a base station controller node. The number of further base stations in <FIG> is merely illustrative and not limiting. Indeed, as carrier aggregation may be performed with carriers of cells controlled by one and the same base station, further base stations, such as further base stations <NUM>, <NUM> and <NUM>, overall are not indispensable for the functioning of the technology described herein. The set of base stations may be referred to, in general, as a radio access network. A cell where a primary carrier of a carrier aggregation is, is referred to as a primary cell, PCell. On the other hand, A cell where a secondary carrier of a carrier aggregation is, is referred to as a secondary cell, SCell. A carrier aggregation has a primary carrier and at least one secondary carrier.

UE <NUM> is able to communicate with base station <NUM> via wireless link <NUM>. Wireless link <NUM> is arranged in accordance with a same radio access technology, RAT, as UE <NUM> and base station <NUM>, to thereby obtain interoperability between these devices. Wireless link <NUM> may have an uplink for conveying information from UE <NUM> to base station <NUM>, and a downlink for conveying information from base station <NUM> to UE <NUM>.

UE <NUM> may be able to communicate with the further base stations as well, in detail, with further base station <NUM> via wireless link <NUM>, with further base station <NUM> via wireless link <NUM> and/or with further base station <NUM> via wireless link <NUM>. Wireless links <NUM>, <NUM> and <NUM> may likewise comprise uplinks for conveying information from the UE side toward the base station side, and downlinks for conveying information from the base station side toward the UE side.

UE <NUM> may be in idle mode or connected mode with regard to the network. In a connected mode, UE <NUM> has a radio resource control, RRC, connection with the network and is enabled to communicate information. In the idle mode, on the other hand, the UE is camped in a cell of the network, but it does not have an active connection, such as an RRC connection, and transmitting data to the network requires first a connection establishment procedure to build up a RRC connection for communication. In idle mode, the network can page the UE, since the network will know the whereabouts of UE <NUM> in the network coverage area. In another example, UE <NUM> could be in inactive state, which means that RRC connection between base station(s) and UE <NUM> is suspended, but the control-plane, C-plane, and user-plane, U-plane, connections are kept alive, in other words, from a core network point of view, the UE is still active. In this inactive state, a UE context is stored in both UE <NUM> and a radio access network, RAN, for example NG-RAN. UE connection may then be established using the Suspend and Resume procedure, for example. In this state, a RAN-based notification area may be configured by RRC layer.

In order to transition from an idle or inactive mode to a connected mode with carrier aggregation, a UE such as UE <NUM> must transition to the connected mode and to participate in establishment of the carrier aggregation. Overall, this may take some time, for example <NUM> milliseconds, which is a delay which a user may detect. Furthermore, where UE <NUM> is a machine-type node, a <NUM>-millisecond delay may be undesired. For example where a high-resolution video feed is to be provided, it may be more useful to obtain the video feed sooner from an event triggering its provision rather than later.

In another example, the present embodiments may apply not only to fast carrier aggregation activation, but also to speeding up other ways of aggregating resources from multiple cells, such as fast dual connectivity activation, multi-connectivity activation, new radio - new radio dual connectivity, NR-NR DC, activation, E-UTRA new radio dual connectivity, EN-DC, fast activation and alike. Carrier aggregation is used here as an example. Thus carrier aggregation, dual connectivity and multi-connectivity may be considered examples of resource aggregation. Multi-radio access technology dual connectivity may be referred to as MR-DC.

To reduce the delay in transitioning from the inactive or idle mode to connected mode with carrier aggregation, a few different approaches are possible. Firstly, an early measurement report may be transmitted. In this approach, a UE may report, during a connection establishment procedure, to the PCell, results of measurements it has conducted while in idle mode or inactive mode. Availability of such results may be indicated in a "msg5" message, for example, by which it is meant a radio resource connection, RRC, setup complete message. The PCell may then request the results to be provided after security activation. A potential problem with measurements conducted in idle mode or during inactive mode is that they may be partly or completely out of date by the time they're used. On the other hand, carrier aggregation may be configured blindly, without UE feedback. While fast, this procedure runs the risk of failure, as incorrect cells may be selected as secondary cells, SCells. Sounding reference signal, SRS, switching is possible in the LTE technology, which allows a UE to send SRS over SCells which normally have no uplink, for example if the UE supports only one UL in any band combination. However, this requires configuration of both carrier aggregation, CA, and SRS, and can therefore be used only after CA has been activated. The primary problem for every case is the same, namely, how to help the UE become setup with the correct SCells that enable CA in as fast manner as possible.

In accordance with technology described herein, UE <NUM> may transmit a signal in the uplink during a connection establishment procedure, that is, during the transitioning from idle or inactive mode to connected mode. Herein transmitting in the uplink means transmitting in the uplinks of potential wireless links to potential SCells. The network may allocate uplink resources to the UE, which the UE then uses to transmit the signal in at least one SCell candidate carrier frequency. The transmission is received by the candidate SCell(s) to determine an uplink signal quality. Additionally, the network may transmit channel state information - reference signal, CSI-RS, in the downlink direction which UE <NUM> may then measure and, optionally, send the results of this measurement in a measurement or channel state information report. The downlink transmission may take place more than once. It may take place also over the primary carrier. Based on this procedure, the network may determine which SCell(s), if any, to configure for the UE for carrier aggregation. In detail, SCells which have good signal quality towards the UE may be configured to participate in the carrier aggregation, since information may successfully be transmitted via them to and from the UE. The UL resources to transmit the signal may be activated based on broadcast or dedicated configuration and could be assigned already during a connection setup, implicitly or explicitly.

In some example embodiments, the UE may send SRS or SRS-like signal(s)) to the network , which in turn measures the SRS or SRS-like signal and decides based on that whether to configure SCell to that UE. In one example, the triggering of the SRS or SRS-like signal could be based on, for example, reception by UE of Msg2 (random access response) or reception of Msg4 (RRC connection setup message). In turn, the UE may transmit the SRS or SRS-like signal together with either Msg3 and/or Msg5, in case the transmission was triggered by reception of Msg2, or Msg5, in case the transmission was triggered by reception of Msg4 (RRC connection setup). The UE may be configured to send the SRS or SRS-like signal, for example, when transitioning to IDLE/INACTIVE or in, for example, Msg4.

In one example embodiment, additionally, the reception of SRS signal could trigger a base station to send, for example, CSI-RS (or CSI-RS like signals) that UE could measure and report. This could last for some time, and configuration may be given in, for example, RRCRelease or, for example, in Msg4 (RRC connection setup message).

The UE may be configured to obtain/receive an uplink transmission configuration comprising information on at least one secondary cell candidate frequency, to transmit a signal in the uplink in accordance with the uplink transmission configuration on the at least one secondary cell candidate frequency, during a connection establishment procedure which transitions the apparatus from an idle mode to a connected mode, and to receive a carrier aggregation configuration from a network. The uplink transmission configuration may be obtained during the connection establishment procedure, for example. The UE may be configured to transmit the signal in the uplink after receiving a random access response and before receiving a security activation message, the signal being other than a radio resource connection signalling message. The uplink transmission configuration may be obtained, by the UE, from at least one of the following: broadcast signalling, dedicated signalling and from determining the uplink transmission configuration from an identity of the apparatus.

The signal transmitted in the uplink may comprise, for example, at least one of the following: a sounding reference signal and a random access preamble. The UE may be configured to transmit the signal more than once. The number of times the UE transmits the signal may be selected in the UE in dependence of a type of traffic or type of application which requests the carrier aggregation. For example, a video telephony call may result in a larger number of times the signal is transmitted than a times system update. Increasing the number of times the signal is transmitted involves investing more energy in establishing the carrier aggregation early.

In another example, the uplink transmission is sent more than once according to an implicit (e.g. fixed) or explicit (i.e. configured) duration. In another example, when receiving at the UE a configuration for sending UL transmission according to a specific UL signal configuration given by the network, the UE may receive information for which cells UL transmission is allowed. The configuration may be received via broadcast or dedicated signalling, for example.

For example, the UE may be configured to obtain information identifying which cells allow transmission of the signal in the uplink during the connection establishment procedure. The UE may be configured to obtain, from broadcasted system information or in connection with a state transition from the connected mode to the idle or inactive mode, an indication that the signal is to be transmitted during the connection establishment procedure at least one of: responsive to receiving a Msg2 (e.g. random access response message), responsive to receiving a Msg4 (e.g. RRC connection setup message), in connection with transmitting at least one of Msg3 (e.g. RRC connection request message) and in connection with transmitting Msg5 (e.g. RRC connection setup complete message). The UE may be configured to receive at least one downlink signal after transmitting the signal in the uplink, and to report to the network a received signal strength of the at least one downlink signal, as measured by the UE.

In an example embodiment, the network indicates, for example via per-cell broadcast information or via pre-configured cell list in dedicated signalling, whether the UE is allowed to utilize the uplink configuration in a given cell. For example, UE <NUM> may know before sending the signal whether it is allowed to trigger the uplink transmission).

In another embodiment, the network sends a downlink signal to the UE after receiving the triggered UL signal transmission from the UE on a given carrier. The downlink signal may comprise, for example, at least of one of: CSI-RS signal, tracking reference signal, TRS, discovery reference signal, DRS, and a synchronization signal block, SSB, transmission. The downlink signal may be sent, for example: via the same carrier where the UL signal was sent, via the primary carrier and more than once according to implicit (e.g. fixed) or explicit (i.e. configured) duration.

<FIG> illustrates an example process in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, from the left to the right, UE <NUM>, primary cell PCell, and secondary cell(s) SCell. The PCell and SCell may be controlled by the same base station, or by different base stations. The SCell(s) may operate on a different frequency band than the PCell.

In phase <NUM>, the UE is informed that uplink transmissions to SCell(s) are allowed during a connection establishment procedure. This informing may take place over broadcasted information, for example broadcasted system information, for example. Traffic with UE <NUM> may be mobile originated or mobile terminated. For example, in optional phase <NUM>, UE <NUM> is paged to receive mobile terminated traffic). Where phase <NUM> is absent, UE <NUM> may itself determine it needs a connection with carrier aggregation. In phase <NUM>, UE <NUM> initiates the connection establishment procedure by transmitting a random access preamble. Phase <NUM> may be referred to as Msg1, corresponding to transmitting the random access preamble. The PCell responds to phase <NUM> by transmitting, in phase <NUM>, a random access response, which may comprise a grant of uplink resources. The message of phase <NUM> may be referred to as Msg2. The message of phase <NUM> may comprise an implicit or explicit trigger for the UE to transmit a signal in the uplink on at least one secondary cell candidate frequency. The UE may be informed concerning the at least one secondary cell candidate frequency in the message of phase <NUM>, for example, or in phase <NUM>. Therefore, in phase <NUM>, PCell may indicate to UE <NUM> that it may initiate the uplink signal towards candidate SCell(s).

In phase <NUM>, UE <NUM> transmits a radio resource control, RRC, setup request to the PCell, and, in embodiments where the message of phase <NUM> acts as the implicit or explicit trigger for the UE to transmit a signal in the uplink on the at least one secondary cell candidate frequency, UE <NUM> transmits this signal at phase <NUM>. Phases <NUM> and <NUM> may occur in either order. Where phase <NUM> takes place more than once, it may take place both before and after phase <NUM>. The message of phase <NUM> may be referred to as Msg3.

Where phase <NUM> takes place, the signal transmitted in the uplink in phase <NUM> is received by at least one SCell, and the SCell(s) and PCell may communicate to establish received signal strengths in the SCell(s) to help determine, which SCell(s) to include in the carrier aggregation. This takes place in phase <NUM>.

In phase <NUM>, the PCell issues a RRC setup message to the UE. This may be known as, for example, Msg4, and the UE responds, in phase <NUM>, with RRC setup complete. The message of phase <NUM> may comprise an implicit or explicit trigger for the UE to transmit a signal in the uplink on at least one secondary cell candidate frequency. In embodiments where this is the case, the UE may transmit the uplink signal in phase <NUM>, and it may be received in phase <NUM>, as described above in connection with phases <NUM> and <NUM>. In other words, UE <NUM> may transmit the signal in the uplink direction after either phase <NUM> or phase <NUM>, depending on the embodiment. In some embodiments, the UE sends the uplink signal after both phases <NUM> and <NUM>. The message of phase <NUM> may be referred to as, for example, Msg5, RRC setup complete.

Phase <NUM> comprises security activation. In some embodiments, this phase also comprises data radio bearer/signalling radio bearer configuration. Data may be transmitted in ciphered form in phase <NUM>, and in phase <NUM> the UE is configured for the carrier aggregation, such that the inclusion of at least one SCell into the carrier aggregation is determined based on processing the received signal strength of the uplink signal in phase <NUM> and/or <NUM>, as described herein above.

<FIG> illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device <NUM>, which may comprise, for example, a mobile communication device such as UE <NUM> of <FIG>, or, in applicable parts, base station <NUM>. Comprised in device <NUM> is processor <NUM>, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor <NUM> may comprise, in general, a control device. Processor <NUM> may comprise more than one processor. Processor <NUM> may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core designed by ARM Holdings or a Zen processing core produced by Advanced Micro Devices Corporation. Processor <NUM> may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor <NUM> may comprise at least one application-specific integrated circuit, ASIC. Processor <NUM> may comprise at least one field-programmable gate array, FPGA. Processor <NUM> may be means for performing method steps in device <NUM>. Processor <NUM> may be configured, at least in part by computer instructions, to perform actions.

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 analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (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.

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

Device <NUM> may comprise user interface, UI, <NUM>. UI <NUM> may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device <NUM> to vibrate, a speaker and a microphone. A user may be able to operate device <NUM> via UI <NUM>, 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 <NUM> or on a cloud accessible via transmitter <NUM> and receiver <NUM>, or via NFC transceiver <NUM>, and/or to play games.

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

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

Processor <NUM>, memory <NUM>, transmitter <NUM>, receiver <NUM>, NFC transceiver <NUM>, UI <NUM> and/or user identity module <NUM> may be interconnected by electrical leads internal to device <NUM> in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device <NUM>, 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.

<FIG> illustrates an example process in accordance with at least some embodiments of the present invention. The process of <FIG> resembles that of <FIG>, and indeed like numbering relates to like phases as in <FIG>. <FIG> illustrates an example of a process, where the candidate SCell(s) transmit signals in the downlink direction to determine received signal qualities also in the UE. This facilitates selection of SCells for the carrier aggregation, since radio channel conditions are known in both directions, and not only in the uplink.

The following differences exist in <FIG> with respect to <FIG>. Phase <NUM> and <NUM>, and/or phase <NUM> and <NUM>, comprise the SCell candidate(s) transmitting in the downlink and the UE <NUM> measuring a signal strength of this downlink transmission, respectively, as illustrated. Further, in phase <NUM> the UE informs the PCell of the received signal strength(s), and the PCell takes this information into account, phase <NUM>, when deciding on an SCell configuration for the carrier aggregation. The informing of phase <NUM> need not take place at exactly the place in the sequence as illustrated in <FIG>, rather, it may take place in general after phase <NUM> or <NUM>, whichever is present in the respective embodiment.

<FIG> 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 <NUM>, an auxiliary device or a personal computer, for example, or in a control device configured to control the functioning thereof, when installed therein.

Phase <NUM> comprises obtaining, in an apparatus, an uplink transmission configuration comprising information on at least one secondary cell candidate frequency. Phase <NUM> comprises transmitting a signal in the uplink in accordance with the uplink transmission configuration on the at least one secondary cell candidate frequency, during a connection establishment procedure which transitions the apparatus from an idle mode to a connected mode. Finally, phase <NUM> comprises receiving a resource aggregation configuration from a network.

<FIG> is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in base station <NUM>, an auxiliary device or a personal computer, for example, or in a control device configured to control the functioning thereof, when installed therein.

Phase <NUM> comprises providing to a user equipment an uplink transmission configuration comprising information on at least one secondary cell candidate frequency. Phase <NUM> comprises preparing, during a connection establishment procedure which transitions the user equipment from an idle mode to a connected mode, a resource aggregation configuration for the user equipment, based at least partly on information from candidate secondary cells which concerns a signal level at which the candidate secondary cells have received a signal transmitted in the uplink by the user equipment during the connection establishment procedure. Finally, phase <NUM> comprises providing the resource aggregation configuration to the user equipment.

At least some embodiments of the present invention find industrial application in in wireless communications.

Claim 1:
An apparatus (<NUM>) comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus (<NUM>) at least to:
- obtain (<NUM>) an uplink transmission configuration comprising information on at least one secondary cell candidate frequency;
- transmit (<NUM>, <NUM>) a signal in the uplink in accordance with the uplink transmission configuration on the at least one secondary cell candidate frequency, during a connection establishment procedure which transitions the apparatus (<NUM>) from an idle mode to a connected mode, after receiving (<NUM>) a random access response and before receiving (<NUM>) a security activation message, the signal being a sounding reference signal or a random access preamble; and
- receive (<NUM>), via a primary cell, a carrier aggregation configuration from a network,
wherein the carrier aggregation configuration configures the apparatus for carrier aggregation, such that inclusion of the at least one secondary cell into the carrier aggregation is based on processing (<NUM>, <NUM>) a signal strength at which the at least one secondary cell received the transmitted signal in the uplink.