Patent ID: 12231877

EMBODIMENTS

FIG.1illustrates an example network scenario, comprising wireless terminal110and a plurality of wireless network nodes120,130and140.

Wireless terminal110may comprise, for example, a User Equipment, UE, a smartphone, a cellular phone, a Machine-to-Machine, M2M, node, machine-type communications node, an Internet of Things, IoT, node, a car telemetry unit, a laptop computer, a tablet computer or, indeed, any kind of suitable wireless user device or mobile station, i.e., a terminal.

Wireless terminal110may be attached, or connected to, wireless network node120over air interface for wireless communications. Wireless network node120may be considered for example as a serving base station (BS), of first wireless terminal110. In general, wireless terminal110and wireless network nodes120-140may be referred to as wireless nodes. For instance, wireless network node120may be referred to as a first wireless node, wireless terminal110may be referred to as a second wireless node, and wireless network node130as third wireless node.

Air interface between wireless terminal110and wireless network node120may be configured in accordance with a Radio Access Technology, RAT, which both first wireless terminal110and wireless network node120are configured to support. Air interface may comprise, e.g., one or more beams between first wireless terminal110and wireless network node120. Examples of cellular RATs include Long Term Evolution, LTE, New Radio, NR, which may also be known as fifth generation, 5G, and MulteFire. On the other hand, example of non-cellular RATs includes Wireless Local Area Network, WLAN.

In case of cellular RATs, wireless network node120-140may be referred to as a BS and wireless terminals may be referred to as UEs. For example, in the context of LTE, wireless node120-140may be referred to as eNB while in the context NR, wireless node120-140may be referred to as gNB. On the other hand, for example in the context of WLAN, wireless node120-140may be referred to as an access point. In any case, embodiments of the present invention are not restricted to any particular wireless technology. Instead, embodiments of the present invention may be exploited in any wireless communication system wherein it is desirable to perform secure communications.

Wireless network node120may be connected to other network nodes130,140, via wired or wireless connection125. Wireless network nodes120-140may be connected, directly or via at least one intermediate node, with core network (not shown inFIG.1), such as a Next Generation core network, Evolved Packet Core (EPC), or other network management element.

Wireless access network and/or core network may comprise various network functions. A network function in the present application may refer to an operational and/or physical entity. The network function may be a specific network node or element, or a specific function or set of functions carried out by one or more entities, such as virtual network elements. Examples of such network functions include a radio access or resource control or management function, mobility management or control function, session management or control function, interworking, data management or storage function, authentication function or a combination of one or more of these functions. Core network may be, in turn, coupled with another network, via which connectivity to further networks may be obtained, for example via a worldwide interconnection network.

A potential eavesdropper in the network, illustrated by terminal device112, may try to intercept and decode the data transmissions115between wireless terminal110and wireless network node120.

In general, evolution of wireless communications poses new challenges for privacy and security. The security mechanisms used at the moment are typically based on classical cryptography. Classical cryptography may not be suitable for IoT communications. IoT devices typically have limited resources, such as processing power, communication capabilities and battery, and thus the use of classical cryptography would often be unsuitable for IoT devices. As opposed to classical cryptography, wherein a security key is for example stored in a subscriber identity module (SIM) card or generated using a hash function stored in the SIM card, physical layer security (PLS) can be provided by applying physical layer measurable parameters in the secrecy key generation and protecting data with such a PLS key. Such physical, measurable variables may be referred to as statistics, quantities and attributes as well. Said physical, measurable variables may be estimated at both sides, at wireless terminal110and wireless network node120, independently.

For example, if channel H1is used by wireless terminal110and wireless network node120, which assumed to be known only at wireless terminal110and wireless network node120(as that can be measured by sending reference signals), the security can be improved. However, when data transmissions may take over a long period of time, channel predictions at the eavesdroppers becomes more feasible with the use of a larger set of related information and by using machine learning algorithms. For example, a demodulation reference signal (DMRS) may be sent for each data transmission instance, and channel estimations with DMRS may become a feasible option. With the larger set of information available and predicting location of the wireless terminal110, channel estimations can be predicted and estimated with greater accuracy. Also, the use of channel estimation is more or less applicable for time division duplex (TDD) schemes, where estimations at both sides should be more or less equal. Eavesdropper terminal112may thus be able to obtain much more information not only by network node120, but also from wireless terminal110.

Improvements are now provided for addressing these challenges, by providing a secret key establishment scheme, which may exploit measurements of channel between wireless terminal110and at least one further network node, such as third network node130and/or fourth network node140. For example, PLS encryption key may be generated based on measurement on channel H2based on communication117between the nodes110and130.

FIG.2illustrates a method for arranging secure communications between wireless nodes. The method may be applied by first wireless node or apparatus communicating with second wireless node, such as wireless network node120in communication with wireless terminal110or UE.

The method comprises transmitting200(from first wireless node) to a second wireless node timing information for controlling security key adoption and information indicative of third wireless node. A message to estimate a channel between second wireless node and third wireless node is transmitted210to third wireless node. The message may comprise information indicative of second wireless node and channel measurement resource information associated with second wireless node.

Block220comprises obtaining a security key generated on the basis of channel estimation information based on estimation of the channel by third wireless node. In some embodiments, block220comprises further steps of receiving from third wireless node channel estimation information based on estimation of the channel by third wireless node and generating the security key on the basis of the received channel estimation information. In an alternative embodiment, third wireless node is configured to generate the security key on the basis of the channel estimation information and block220comprises receiving the security key from third wireless node.

The security key is applied230for data transmission between first wireless node and second wireless node. Thus, the security key is used for encrypting the data and/or decrypting the data between first wireless node and second wireless node, i.e. as an encryption key and/or decryption key.

FIG.3illustrates a method for arranging secure communications between wireless nodes. The method may be applied by second wireless node or apparatus communicating with first wireless node, such as wireless terminal node110or UE in communication with wireless network node, such as first wireless network node120.

The method comprises receiving300, from first wireless node, timing information for security key adoption and information indicative of third wireless node. Block310comprises receiving channel measurement resource information associated with third wireless node.

A trigger message to estimate a channel between second wireless node and third wireless node is received320. Channel estimation information is generated330on the basis of estimation of the channel in response to the received trigger message and on the basis of the received channel measurement resource information. The channel estimation may be generated on the basis of measurements on a reference signal from third wireless node.

A security key is generated340on the basis of the channel estimation information. The security key is applied350, in accordance with the received timing information, for encrypted data transmission between first wireless node and second wireless node.

FIG.4illustrates a method for supporting security key generation for wireless nodes. The method may be applied by third wireless node, or apparatus or controller comprising or included in third wireless node, such as third wireless network node130.

The method comprises receiving400from first wireless node a message to estimate a channel between second wireless node and third wireless node. The message may comprise information indicative of second wireless node and channel measurement resource information associated with second wireless node. A reference signal is transmitted410, on the basis of the received channel measurement resource information, to second wireless node for directional or omnidirectional channel sensing to estimate the channel.

Channel estimation information is generated420on the basis of estimation of the channel in response to the received trigger message and on the basis of the received channel measurement resource information. For example, third wireless node may estimate the channel on the basis of a reference signal, such as a sounding reference signal, or a response message from second wireless node.

The channel estimation information is in some embodiments transmitted430to first wireless node for generating a security key for encrypting data between first wireless node and second wireless node. In some alternative embodiments, third wireless node generates440the security key and transmits450the security key to first wireless node.

It will be appreciated that various amendments may be performed and there may be further stages/blocks in the above disclosed method(s). It may be possible to perform at least some of the blocks in a different order. For example, in some embodiments the information of blocks300and310is received in a single message from first wireless node120, but in another embodiment the channel measurement information is received from third wireless node130. As another example, the trigger message may be transmitted and received from first wireless node to second wireless node110together with information in blocks300and310. In a still another example variation, the trigger message of block320is received from third wireless node, e.g. with or by the reference signal. Some further example embodiments are now illustrated, with reference to example nodes ofFIG.1and also with further references to 3GPP 5G system, without however limiting the disclosed features to such system.

In some embodiments, first wireless node120identifies, before block200, a set of secondary wireless nodes that can be used to estimate channel to second node, the set comprising third wireless node. First wireless node120may send information indicative of the set of secondary wireless nodes to second node, e.g. in block200.

First wireless node120may be configured to select, before block200, third wireless node130among secondary wireless nodes in the set. The selection may be indicated for both second wireless node and third wireless node. Such selection step may be entered before or after block200. Thus, block200or210may be entered in response to the selection.

Applied secondary wireless node may be identified or selected on the basis of location information of secondary wireless nodes and second wireless node, for example. The first wireless node may comprise a prediction algorithm, which may apply a machine learning model, configured to predict and/or select the applicable secondary node(s). In an embodiment, secondary wireless nodes are selected on the basis of radio channel measurement reporting from second wireless node. For example, initial or regular feedback from the UE on received signal quality, e.g. based on synchronization signal blocks (SSBs) reception. In a still another example embodiment, first wireless node configures UL reference signal transmission (or sweeping) to different directions and coordinates with other wireless nodes to learn the best secondary wireless nodes in terms of received channel quality.

The applied secondary wireless node may be selected within the set on the basis of random selection, such that an eavesdropper cannot predict it. In some other example embodiments, secondary wireless node may be selected within the set on the basis of channel quality and/or direction information of respective secondary wireless node. Thus, first wireless node may select secondary wireless node that is communicating (substantially) from a different direction than first wireless node. The applied secondary wireless node may be changed e.g. periodically and/or selected each time there is a need to generate a security key.

In another embodiment, a plurality of secondary wireless nodes is applied for generating or updating the security key between first wireless node120and the second wireless node110. Thus, in addition to transmitting a first channel measurement configuration associated with third wireless node130to the second wireless node and to third wireless node, first wireless node may transmit a second channel measurement configuration associated with a fourth wireless node to the second wireless node and fourth wireless node in the set of secondary wireless nodes. First wireless node may transmit an indication to at least some of the secondary wireless nodes in the set to perform channel estimation for second wireless node. First wireless node may transmit a specific indication to second wireless node to perform the channel estimation with the plurality of secondary wireless nodes. Channel estimation information may be received from the plurality of secondary wireless nodes and the security key may be generate on the basis of at least some of the received channel estimation information from the set of secondary wireless nodes.

In some embodiments, first wireless node120transmits channel measurement resource information associated with third wireless node130to the second wireless node110. This may be performed together with other information in block300or configured separately from block300. In another embodiment, third wireless node transmits channel measurement resource information to the second wireless node after block210.

The timing information for security key adoption may be a predefined parameter which may be configurable. The timing information may be dynamically determined on the basis of information of one or more of: backhaul latencies, propagation delays, and channel state information computation delays associated for performing the channel estimation between the second wireless node and third wireless node. This enables to ensure that second wireless node does not apply the security key too early. However, it will be appreciated that various other embodiments are also applicable for setting the encryption timing information to the second wireless node110. It is also to be noted that the security key may be generated (and then directly taken into use) based on the timing information.

The security key may be generated340,440based on the channel estimation information to encrypt a physical layer message in block230,350according to a PLS method. The security key may be provided to a PLS ciphering module comprised by node110,120and configured to encrypt and/or decrypt PLS encrypted messages.

It is to be appreciated that the present features may be applied in connection with a number of different PLS methods and PLS security keys. In some example embodiments, the security key is a scrambling sequence, where sequence is generated by a set of pre-defined steps, but at least some of the channel estimation information is used as input parameters to the steps to make that unique. In an embodiment, scrambling sequence generation can be initiated by components or parameters of the estimated channel between the second wireless node and third wireless node. For example, first wireless node120and the second wireless node110may be configured to obtain a long-term quantity among measurement information in the channel estimation information and adopt the quantity as a seed to a hash function to generate the security key.

Reference is made toFIG.5illustrating a signaling example according to some embodiments, with references to the example entities ofFIG.1. As indicated earlier, second wireless node110may be terminal node, such as UE and (first, third and fourth) wireless nodes120-140may be network nodes, such as base stations or gNBs, for example.

First wireless node120transmits a first channel measurement configuration (associated with third wireless node) to third wireless node130by message500and to the second wireless node110by message504. First wireless node120also transmits a second measurement configuration (associated with fourth wireless node) to the second wireless node110by message504and to fourth wireless node140by message502. It is to be noted that the configurations may be alternatively sent in separate messages to the second wireless node110.

In some embodiments, channel estimation may be performed using channel state information-reference signals (CSI-RS) from third wireless node130to the second wireless node110. CSI-RSs may be used by the second wireless node110to estimate a channel. Thus, the measurement configurations of messages500,502,504may comprise CSI-RS resource information.

In some embodiments, channel estimation may be performed at the secondary wireless node(s)130,140based on sounding reference signals (SRS) transmitted by the second wireless node110. Thus, the measurement configurations of messages500,502,504may comprise SRS resource information.

First wireless node120may be configured to transmit specific trigger messages to second wireless node110and the one or more secondary wireless nodes, i.e. at least third wireless node, to estimate the channel between the second wireless node and third wireless node. In the example ofFIG.5, first wireless node120selects third wireless node130to perform channel estimation information for security key generation purposes. Accordingly, a first trigger message506is transmitted to third wireless node130and a second trigger message510to second wireless node110to control estimation of the channel between nodes110and130.

In an embodiment, after the transmission of the first trigger message506to third wireless node, first wireless node120activates a timer and applies a waiting time period508before transmitting the second trigger message510. As long as second wireless node110is not receiving the first trigger message from first wireless node120, it does not have to measure the channel or transmit a reference signal for third wireless node130for security key generation purpose.

In some embodiments, first wireless node120transmits channel estimation timing information to secondary nodes, such as third wireless node130, for controlling timing of a reference signal from third wireless node to second wireless node for the estimation of the channel. This channel estimation timing information may be transmitted in the first trigger message506, for example. In accordance with the channel estimation timing information, third wireless node130initiates channel measurement and may transmit a reference signal514for estimating the channel by second wireless node110, such as a CSI-RS in accordance with the received CSI-RS resource information.

This enables to achieve appropriate timing of channel measurements by nodes110and130. In another embodiment, instead of or in addition to the waiting time period508, channel estimation timing information is included in the second trigger message510, on the basis of which second wireless node110initiates channel measurement, e.g. adapts to receive CSI-RS message in accordance with the received channel measurement resource information.

Second wireless node110generates channel measurement information based on the received reference signal514and generates518a security key based on the channel measurement information. Second wireless node110also transmits a reference signal516, such as a SRS, to third wireless node in accordance with the received first channel measurement configuration (504).

Third wireless node130receives the reference signal516and generates520channel measurement information based on the received reference signal516. Third wireless node130transmits the channel measurement information522to first wireless node110, which generates524a security key based on the received channel measurement information522. Messages526,528may then be transmitted between wireless nodes110,120by applying the generate security keys.

The message504to second wireless node110may comprise timing information for the security key adoption. In some embodiments, the timing information for security key adoption indicates a time interval512. Second wireless node may be configured to trigger a timer in response to the trigger message510and begin to use the security key (in block350) only after the time interval512has passed.

Above-illustrated features may be applied, for example, in networks operating in accordance with 3GPP standards, such as in 5G/NR networks. In case of 5G NR, the presently disclosed features may be implemented by extending CSI framework defined in NR. CSI-RS may be used for a different cell to transmit CSI-RS and UE can measure them by associating to SSBs of that cell.

At least some of the above-illustrated messages may be 5G RRC messages. Above-illustrated information between to/from first wireless node120may be added as new information element(s) in existing control message(s) and/or a new message type may be specified. 3GPP 5G RRC message(s) may be applied between gNB and UE. For example, the message504may comprise CSI-ResourceConfig element and SRS-ResourceSet element for the resource information and the second trigger message510may comprise a DCI field CSI Request and a DCI field SRS request, which may be modified for the present purpose and include further information or element(s). 3GPP 5G Xn interface message(s) may be applied between gNBs.

As also indicated in the bottom ofFIG.5as another option, above-illustrated features may be applied in connection with multiple transmission reception point (TRP) system comprising a primary TRP (which may operate as first wireless node120illustrated above) and a set of secondary TRPs (which may operate as third wireless node130and fourth wireless node140illustrated above). In such scenario, CSI-RS and SRS configurations may also be configured via RRC signaling to the UE and respective configurations being indicated to the secondary TRPs. The primary TRP may coordinate with the secondary TRPs when to transmit/receive CSI-RS and SRS. The primary TRP may also control the timing information for security key adoption to the UE such that it has enough time to measure the CSI, transmit SRS, generate a PLS key. For example, a secondary TRP1may transmit CSI-RS, measure SRS and estimate the CSI based on the measured SRS. Then, the TRP1feedbacks the estimated CSI to the primary TRP such that primary TRP can generate the PLS key. Once the PLS key is generated at both ends, the primary TRP and UE, the key is applied after the timing information for security key adoption. This procedure can further continue for another secondary TRP.

The present embodiments therefore facilitate a solution for physical layer encryption. More specifically, at least some embodiments provide a solution enable to further improve the security level, by making it more difficult for eavesdroppers to obtain information to obtain information to generate the security key.

By applying above-illustrated features, radio and power resources can be more optimally used, since secondary wireless nodes or TRPs may transmit the reference signals only upon need (at an appropriate time) to generate the security key, and UE does not measure them or transmit SRS unnecessarily. As data transmissions are not be carried with secondary wireless nodes or TRPs, the estimated channels are more secure to generate PLS keys and to provide the secrecy for the data transmissions between first or primary wireless node and second wireless node or UE.

An electronic device comprising electronic circuitries may be an apparatus for realizing at least some embodiments of the present invention. The apparatus may be or may be comprised in a computer, a laptop, a tablet computer, a cellular phone, a machine to machine (M2M) device (e.g. an IoT sensor device), a base station, an access point or network node device or any other apparatus provided with radio communication capability. In another embodiment, the apparatus carrying out the above-described functionalities is comprised in such a device, e.g. the apparatus may comprise a circuitry, such as a chip, a chipset, a microcontroller, or a combination of such circuitries in any one of the above-described devices.

FIG.6illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device600, which may comprise, for example, first wireless terminal node110, wireless network node120or130ofFIG.1, or device600may be configured to control the functioning thereof, possibly when installed therein. The apparatus may be configured to perform the method ofFIG.2,3, or4, or an embodiment thereof.

Comprised in device600is processor610, 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. Processor610may comprise, in general, a control device. Processor610may comprise more than one processor. Processor610may comprise at least one application-specific integrated circuit, ASIC. Processor610may comprise at least one field-programmable gate array, FPGA. Processor610may be means for performing method steps in device600. Processor610may 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.

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.

Device600may comprise memory620. Memory620may comprise random-access memory and/or permanent memory. Memory620may comprise at least one RAM chip. Memory620may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory620may be at least in part accessible to processor610. Memory620may be at least in part comprised in processor610. Memory620may be means for storing information. Memory620may comprise computer instructions that processor610is configured to execute. When computer instructions configured to cause processor610to perform certain actions are stored in memory620, and device600overall is configured to run under the direction of processor610using computer instructions from memory620, processor610and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory620may be at least in part comprised in processor610. Memory620may be at least in part external to device600but accessible to device600. The memory may store parameters affecting the operation of the device, such as some or all of the functions illustrated above in connection withFIGS.2to4.

Device600may comprise a transmitter630. Device600may comprise a receiver640. Transmitter630and receiver640may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter630may comprise more than one transmitter. Receiver640may comprise more than one receiver. Transmitter630and/or receiver640may be configured to operate in accordance with Global System for Mobile communication, GSM, Wideband Code Division Multiple Access, WCDMA, 5G/NR, Long Term Evolution, LTE, IS-95, Wireless Local Area Network, WLAN, and/or Ethernet standards, for example.

Device600may comprise a near-field communication, NFC, transceiver650. NFC transceiver650may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

Device600may comprise user interface, UI,660. UI660may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device600to vibrate, a speaker and a microphone. A user may be able to operate device600via UI660, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory620or on a cloud accessible via transmitter630and receiver640, or via NFC transceiver650, and/or to configured the operation of the device.

Device600may comprise or be arranged to accept a user identity module670. User identity module670may comprise, for example, a subscriber identity module, SIM, card installable in device600. A user identity module670may comprise information identifying a subscription of a user of device600. A user identity module670may comprise cryptographic information usable to verify the identity of a user of device600and/or to facilitate encryption of communicated information and billing of the user of device600for communication effected via device600.

Processor610may be furnished with a transmitter arranged to output information from processor610, via electrical leads internal to device600, to other devices comprised in device600. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory620for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor610may comprise a receiver arranged to receive information in processor610, via electrical leads internal to device600, from other devices comprised in device600. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver640for processing in processor610. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

Device600may comprise further devices not illustrated inFIG.6. For example, where device600comprises a smartphone, it may comprise at least one digital camera. Some devices600may 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. Device600may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device600. In some embodiments, device600lacks at least one device described above. For example, some devices600may lack a NFC transceiver650and/or user identity module670.

Processor610, memory620, transmitter630, receiver640, NFC transceiver650, UI660and/or user identity module670may be interconnected by electrical leads internal to device600in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device600, 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.

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.

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.

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.

In an exemplary embodiment, an apparatus, such as, for example, first wireless terminal110or wireless network node120,130, may comprise means for carrying out the embodiments described above and any combination thereof.

In an exemplary embodiment, a computer program may be configured to cause a method in accordance with the embodiments described above and any combination thereof. In an example embodiment, a computer program product, embodied on a non-transitory computer readable medium, may be configured to control a processor to perform a process comprising the embodiments described above and any combination thereof.

In an example embodiment, an apparatus, such as, for example, first wireless terminal110or wireless network node120,130, may comprise at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform the embodiments described above and any combination thereof.

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., to provide 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.

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.

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.