Patent Description:
In wireless telecommunication, aggregating plural carriers together can be employed to obtain an aggregated carrier which employs a wider bandwidth than individual carriers. Thus an instantaneous data rate, for example, may be increased as a response to a determined need to transfer more information. Such aggregation may be referred to as carrier aggregation, CA.

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

According to a first aspect of the present disclosure, there is provided an apparatus 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 at least to process carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and use the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

According to a second aspect of the present disclosure, there is provided a method comprising processing carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and using the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

According to a third aspect of the present disclosure, there is provided an apparatus comprising means for processing carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and using the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

According to a fourth 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 process carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and use the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

According to a fifth aspect of the present disclosure, there is provided a computer program configured to cause a computer to perform at least the following, when run: processing carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and using the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

3GPP TDoc R4-<NUM> describes associating bandwidth classes with supported PA architecture and supported MIMO layers.

3GPP TDoc R4-<NUM> describes the support of bandwidth classes within the same fall back group.

3GPP TDoc R4-<NUM> describes a fallback group comprising multiple bandwidth classes.

In accordance with methods and processes disclosed herein, a more versatile carrier aggregation mechanism may be obtained with an efficient signalling process. In detail, fallback rules in carrier aggregation may be defined in a manner which supports more versatile fallback options and more efficient carrier aggregation capability signalling.

<FIG> illustrates an example system in accordance with at least some embodiments. In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR), also known as fifth generation (<NUM>), without restricting the embodiments to such an architecture, however. The embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

Examples of such other communication systems include microwave links and optical fibers, for example.

<FIG> shows user devices <NUM> and <NUM> configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) <NUM> providing the cell. The physical link from a user device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage. A communications system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signalling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of the communication system it is coupled to. The NodeB may also be referred to as a base station, BS, an access point or any other type of interfacing device including a relay station such as DU (distributed unit) part of IAB (integrated access and backhaul) node capable of operating in a wireless environment. The DU part may facilitate the gNB functionalities of the IAB node. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices, such as user equipments. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network <NUM> (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobility management entity (MME), etc..

The user device (also called UE, user equipment, user terminal, terminal device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, also including a relay node. An example of such scenario is MT (mobile termination) part of IAB node, which provides the backhaul connection for the IAB node.

The user device, or user equipment, typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device.

CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in physical objects at different locations.

Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in <FIG>) may be implemented inside these apparatuses, to enable the functioning thereof.

<NUM> enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. <NUM> mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. <NUM> is expected to have multiple radio interfaces, namely below <NUM>, cmWave and mmWave, and also being integrable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and <NUM> radio interface access comes from small cells by aggregation to the LTE. In other words, <NUM> is planned to support both inter-RAT operability (such as LTE-<NUM>) and inter-RI operability (inter-radio interface operability, such as below <NUM> - cmWave, below <NUM> - cmWave - mmWave). One of the concepts considered to be used in <NUM> networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility. <NUM> uses frequency range <NUM>, FR1, ranging from <NUM> to <NUM> and frequency range <NUM>, FR2, ranging from <NUM> to <NUM>.

Architecture in LTE networks is distributed in the radio and centralized in the core network.

Some other technology advancements, such as Big Data and all-IP, may change the way networks are being constructed and managed.

Each satellite <NUM> in the constellation may cover several satellite-enabled network entities that create on-ground cells.

The depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. A cellular radio system may be implemented as a multilayer network including several kinds of cells, such as macrocells, microcells and picocells, for example.

In unlicensed-band NR operation, a bandwidth part, BWP, may comprise plural sub-bands separated from each other by guard bands. The sub-bands may be, but need not be, <NUM> wide, for example. Operation on the BWP may proceed based on sub-band specific listen-before talk, LBT, operation. In LBT, a node desiring to use a spectrum resource will listen on the resource before using it, and only proceed to transmit on the resource in case the listening indicates the resource appears to be free, that is, not currently in use. Simultaneous use of the same resource by plural transmitters leads to interference and decreased quality of communication on the resource.

A bandwidth part, BWP, is a contiguous set of physical resource blocks, PRBs, on a given carrier. A carrier bandwidth may be <NUM>, <NUM> or <NUM>, for example. These PRBs are selected from a contiguous subset of the usable common resource blocks for a given numerology on a carrier. A BWP may be characterized by the following features: subcarrier spacing, SCS, sub-band number and sub-band bandwidth. SCS may take values such as <NUM>, <NUM> or <NUM>, for example. A carrier may comprise <NUM>, <NUM>, <NUM>, <NUM> or <NUM> sub-bands of <NUM>-MHz bandwidth, for example. A PRB may have <NUM> subcarriers, for example. Likewise, a normal scheduling unit in time (known as a slot) may be <NUM> or <NUM> OFDM symbols long. Furthermore, NR supports mini-slot based operation with the scheduling unit in time smaller than one slot, for example <NUM>, <NUM> or <NUM> OFDM symbols. In <NUM>, the PRB may be both <NUM> subcarriers wide and <NUM> OFDM symbols long, assuming normal cyclic prefix. A transmission bandwidth, TX BW, is a part of the spectrum on which a node actually transmits following the listening phase of LBT of a sub-band specific LBT process. The TX BW may be the entire bandwidth of BWP, or a portion thereof, in dependence of a result of the listening phase.

Carrier aggregation, CA, is a solution to increase in instantaneous datarate available to a user equipment, wherein multiple separate carriers, known as component carriers, CCs, are assigned to the user equipment. The datarate per user is increased the more component carriers are aggregated together. When the component carriers are adjacent to each other in frequency, the aggregation is referred to as contiguous carrier aggregation or intra-band contiguous carrier aggregation. When the component carriers are not adjacent, but on the same frequency band, the aggregation is referred to as intra-band non-contiguous carrier aggregation. In case the component carriers are on different frequency bands, the aggregation is referred to as inter-band carrier aggregation. In particular, in contiguous carrier aggregation, the component carriers form a contiguous block without carrier(s) that are separated in frequency.

A fallback process to a carrier aggregation configuration having fewer carriers may be invoked for various reasons, for example, in case interference on one of the component carriers degrades performance, or simply in case a smaller datarate has become sufficient due to changes in communication patterns. A fallback group is a group of carrier aggregation bandwidth classes for which it is mandatory for a UE to be able to fallback to lower order CA bandwidth class configuration. In other words, a UE needs to be able to reduce the number of component carriers aggregated together in the CA configuration it is using, to switch to another CA bandwidth class in the same fallback group with fewer components carriers.

A simple example carrier aggregation capability information is provided in the following table:.

Here the bandwidth classes are named A - F, and they are allocated into fallback groups <NUM>, <NUM> and <NUM>. For example, in case a UE is communicating using bandwidth class D, it may fall back to bandwidth class C as C is in the same fallback group and has fewer component carriers, CCs. Of note is that in the table above there is many-to-one mapping of bandwidth classes to fallback groups, namely, plural bandwidth classes are in each fallback group, and each bandwidth class is in only one fallback group.

In some situations, however, it would be beneficial for a UE to be able to fall back to a bandwidth class in a different fallback group. For example, as bandwidth classes in one fallback group have the same maximum supported component carrier bandwidth, in some situations it would be useful to switch to a bandwidth class with a smaller maximum component carrier bandwidth. In particular, using a smaller bandwidth could be useful in case a radio path used for communication deteriorates, or if a UE does not support all bandwidth classes with the larger maximum component carrier bandwidth due to, for example, limitation on supported aggregated channel bandwidth. Lack of support may occur as older UEs are kept in use as newer bandwidth classes are introduced, for example.

One manner of accomplishing this would be to define additional bandwidth classes in carrier aggregation capability information, such that these new additional bandwidth classes would be present in two or more different fallback groups, to enable selecting a bandwidth class to fall back on. While this would solve the problem of enabling more versatile fallback, signalling support for bandwidth classes would consume more resources, since the new bandwidth classes would need to be signalled from the UE to the network upon attachment to the network, for example, for each supported CA band in each supported CA band combination. Thus signalling support for bandwidth classes would consume more communication resources, such as energy and/or time. Consequently, it would be advantageous to enable a versatile fallback carrier aggregation mechanism which may be signalled using as few bits as possible.

<FIG> illustrates an example of carrier aggregation capability information. On the left are carrier aggregation bandwidth classes, in this example for new radio, NR, another term for <NUM> as standardized by the <NUM>rd generation partnership project, 3GPP. The aggregated channel bandwidth indicates the aggregate bandwidth of the component carriers aggregated together, the information of <FIG> relating to contiguous carrier aggregation.

In this example, maximum supported component carrier bandwidths for fallback groups <NUM>, <NUM>, <NUM> and <NUM> are <NUM>, <NUM>, <NUM> and <NUM>, respectively except for bandwidth class A. In the illustrated carrier aggregation capability information is mandatory for a UE to be able to fallback to lower order CA bandwidth class configuration within a fallback group. Likewise, it is not mandatory for a UE to be able to fallback to lower order CA bandwidth class configuration that belongs to a different fallback group unless unless the CA bandwidth class the UE is using is associated with the different fallback group. In <FIG>, bandwidth classes V, W, X and Y are associated with fallback group <NUM> and it is mandatory for a UE to be able to fallback from one of these to a same or lower order CA bandwidth class configuration, with the same or a lower number of contiguous CCs, within fallback group <NUM>.

As bandwidth class A only has one component carrier, it is not in fact genuinely a carrier aggregation bandwidth class since no carriers are aggregated when using it. The number of bandwidth classes in the figure is an example to which the present disclosure is not limited. It is present in <FIG> to provide an ultimate fall-back configuration to all the aggregated bandwidth classes. An important distinction is that the bandwidth classes listed under fallback group <NUM> have a maximum CC bandwidth of <NUM>, while those listed under fallback group <NUM> have a maximum CC bandwidth of <NUM>. The maximum is the supported CC bandwidth, for CA bandwidth class S, for example, there are <NUM> CCs, <NUM> CCs each with <NUM>, and the last CC with smaller or equal to <NUM>, thus aggregated channel bandwidth is <NUM> < BW ≤ <NUM>. It is mandatory for a UE to be able to fallback to lower order CA bandwidth class (that is, one with fewer CCs) configuration within a fallback group. In addition to this, bandwidth classes V, W, X and Y are capable of falling back to a bandwidth class in fallback group <NUM>. In other words, a proper subset (that is, a subset which does not comprise all the elements of the superset of all CA bandwidth classes) of the bandwidth classes is both comprised in a fallback group and, separately, associated with at least another one of the fallback groups. For example, the associated fallback group may have a smaller maximum CC bandwidth than the fallback group in which the proper subset of the bandwidth classes is comprised.

When falling back to a bandwidth class in the fallback group with which the proper subset is associated, the bandwidth class selected for fallback may have the same number of CCs, or a smaller number of CCs, as the bandwidth class in the proper subset from which the fallback originates. It is thus possible to maintain the number of CCs, but reduce at least one of their bandwidths, in the fallback process. Thus the aggregated bandwidth is reduced in the fallback process compared to the original bandwidth class. As can be seen from <FIG>, as the number of CCs in the bandwidth classes fallback group <NUM> is lower than in the proper subset, a fallback to any of the bandwidth classes in fallback group <NUM> is possible from any one of the bandwidth classes in the proper subset.

The newly defined bandwidth classes V, W, X and Y (note that the indices V, W, X, Y are used as examples and other indices may equally be used) can be mapped to those bandwidth class combinations as follows:.

Therefore, network operators can gradually migrate <NUM> CCs to <NUM> CCs, one-by-one, for example, in their CA configurations following spectrum acquisition and equipment (UE and base station) availability, for example from bandwidth class combination MA to LD to KE to JF to IR to HS to GT using bandwidth class V with the least overhead on RRC signalling. Other options require more radio resource control, RRC, signalling overhead to achieve the CA configurations considering migration of bandwidth classes.

Moreover, each of the newly defined bandwidth classes V, W, X and Y, which form the proper subset in the example of <FIG>, is mapped to fallback group <NUM>, where they are comprised, and fallback group <NUM>, with which they are associated. There is no need to define new bandwidth classes which belong to fallback group <NUM>, which has a smaller maximum supported CC bandwidth than fallback group <NUM>. This is feasible, since normally a UE supporting <NUM> CCs in one band in one band combination can also support <NUM> CCs in this band. Therefore, a UE supporting a bandwidth class which belongs to fallback group <NUM> in one band in one band combination can technically also support a bandwidth class which belongs to fallback group <NUM> with the same or a smaller number of contiguous CC in this band and band combination.

The same principle can also apply to fallback groups with other maximum supported CC bandwidths than <NUM> or <NUM>. For example, a UE supporting bandwidth class C which belongs to fallback group <NUM> (CC maximum width <NUM>) can technically also support bandwidth class D or E which belongs to fallback group <NUM> (CC maximum width <NUM>) with the same or a smaller number of contiguous CC, that is, the same or a lower number of contiguous CCs. In general, this versatility is achieved by mapping at least some bandwidth classes with plural CCs with more than one fallback group.

Consequently, to support for CA bandwidth class configurations consisting of CA bandwidth classes which belong to different fallback groups, new bandwidth classes only need to be defined in the fallback group with the largest maximum supported CC bandwidth among the fallback groups, with each of the new bandwidth class being mapped to at least one of the other fallback groups which have the same or smaller maximum supported CC bandwidths.

In practical terms, a user equipment may indicate its support for the proper subset of bandwidth classes, for example, by providing the following information elements to the network:.

The first one of the information elements above may be communicated using [log<NUM>(<NUM>)] = <NUM> bits, and the latter one using [log<NUM>(<NUM>)] = <NUM> bits.

<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 a UE or, in applicable parts, a base station node. 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 manufactured by ARM Holdings or a Zen processing core designed 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> such as processing and using. 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 analogue and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analogue and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or 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.

Memory <NUM> may comprise randomaccess memory and/or permanent memory.

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 signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, UE <NUM> of <FIG>, and on the right, a base station. Time advances from the top toward the bottom.

In phase <NUM>, the UE stores the carrier aggregation capability information of the user equipment. In phase <NUM>, which may take place in connection with an attachment, such as initial attachment, to a wireless communication network, the UE signals to the base station BS to indicate the carrier aggregation capability information, at least in part. In particular, the UE may indicate the proper subset of carrier aggregation bandwidth classes which are comprised in a first fallback group and associated with a second fallback group, wherein the second fallback group has a narrower maximum CC bandwidth than the first group, and the carrier aggregation capability information indicates the UE supports fallback from bandwidth classes in the proper subset to bandwidth classes in the second fallback group.

In phase <NUM>, the UE and the network may negotiate concerning establishing a carrier aggregation, CA, session, which may be based, at least in part, on the carrier aggregation capability information communicated in phase <NUM>.

<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 a user equipment or a base station, for example, or in a control device configured to control the functioning thereof, when installed therein.

Phase <NUM> comprises processing carrier aggregation capability information, the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class must be able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant, wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised. Phase <NUM> comprises using the carrier aggregation capability information to select a fallback carrier aggregation configuration, wherein the fallback group(s) associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth(s) than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.

When the proper subset is associated with more than one fallback group in which it is not comprised, the system, may choose, in the event of a fallback, from among the plural associated fallback groups, which one to use. This provides the technical benefit that a broader range of fallback options is available.

Claim 1:
An apparatus comprising:
- means for processing carrier aggregation capability information (<NUM>), the carrier aggregation capability information defining a plurality of carrier aggregation bandwidth classes, each carrier aggregation bandwidth class being associated with exactly one number of plural contiguous component carriers used when communicating using the respective carrier aggregation bandwidth class, each carrier aggregation bandwidth class being comprised in a fallback group, each fallback group comprising plural carrier aggregation bandwidth classes, the carrier aggregation capability information defining that a communication device using a specific carrier aggregation bandwidth class is able to fall back to using a carrier aggregation bandwidth class within the same fallback group with fewer component carriers than the specific carrier aggregation bandwidth class, wherein a maximum supported component carrier bandwidth within a fallback group is constant,
- characterised,
- wherein a proper subset of the carrier aggregation bandwidth classes is associated with at least one fallback group in which it is not comprised, and
- means for using the carrier aggregation capability information to select a fallback carrier aggregation configuration (<NUM>), wherein the at least one fallback group associated with the proper subset of the carrier aggregation bandwidth classes has lower maximum supported component carrier bandwidth than the fallback group in which the proper subset of the carrier aggregation bandwidth classes is comprised.