Enabling passive listening of data traffic

Abstract

Various example embodiments relate to enabling a terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to another device. A tethering device may comprise: means for receiving, from a terminal device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; and means for transmitting, to the terminal device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.

Description

ENABLING PASSIVE LISTENING OF DATA TRAFFICTECHNICAL FIELD

[0001] Various example embodiments generally relate to the field of data communication. Some example embodiments relate to enabling a terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to another device.BACKGROUND

[0002] Wireless tethering in a communication network enables a terminal device to communicate data with the communication network via a tethering device configured to relay data transmissions between the terminal device and an access node of the communication network. Wireless tethering may be implemented using any suitable communication protocol. For example, in case of cellular communication networks, both 3GPP (3rdGeneration Partnership Project) and non-3GPP protocols may be used. XR (extended Reality) may be used to provide new experiences for immersive media services, for example by means of augmented reality (AR), virtual reality (VR), or mixed reality (MR).SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] Example embodiments of the present disclosure improve various aspects of wireless tethering, enabling for example lower power consumption, lower device complexity, lower latency, and higher transmission capacity. This and other benefits may be achieved by the features of the independent claims. Further example embodiments are provided in the dependent claims, the description, and the drawings.

[0005] According to a first aspect, a tethering device is disclosed. The tethering device may comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the tethering device at least to: receive, from a terminal device, a request for the terminal device to operate as a listener to datatraffic transmitted by an access node of a communication network to the tethering device; and transmit, to the terminal device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.

[0006] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: establish a secure connection with the terminal device; and transmit the signalling information to the terminal device via the secure connection.

[0007] According to an example embodiment of the first aspect, the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: transmit, to the terminal device, an indication of successful switch of the terminal device to the passive listening mode.

[0008] According to an example embodiment of the first aspect, signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

[0009] According to an example embodiment of the first aspect, the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

[0010] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: receive the data traffic from the access node, wherein the data traffic comprises a plurality of data packets; and transmit, to the terminal device, at least one data packet of the data traffic.

[0011] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: receive, from the terminal device, a request for at least one data packet not successfully decoded by the terminal device; and transmit, based on the request, to the terminal device, the at least one data packet.

[0012] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to:receive, from the terminal device, information on link quality between the access node and the terminal device; and transmit, by the tethering device to the access node, link quality information comprising: a combination of information on link quality between the access node and the tethering device and the information on the link quality between the access node and the terminal device, or the information on the link quality between the access node and the terminal device.

[0013] According to an example embodiment of the first aspect, the information on the link quality between the access node and the terminal device comprises at least one of the following: data packet retransmission feedback information of the terminal device, channel state information of the terminal device indicative of a state of the radio channel between the access node and the terminal device, or reference signal received power at the terminal device.

[0014] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: combine the channel state information of the terminal device with channel state information of the tethering device indicative of a state of a radio channel between the access node and the tethering device; or combine the data packet retransmission feedback information of the terminal device with data packet retransmission feedback information of the tethering device based on transmitting, to the access node, a retransmission request for data packets not successfully decoded by both the terminal device and the tethering device and not transmitting a retransmission request for data packets successfully decoded by either the terminal device or the tethering device.

[0015] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: combine the channel state information of the terminal device with the channel state information of the tethering device based on selecting channel state information that is indicative of weakest or strongest radio channel conditions among the channel state information of the terminal device and the channel state information of the tethering device.

[0016] According to an example embodiment of the first aspect, the instructions are configured to, when executed by the at least one processor, cause the tethering device to: receive an indication of at least one requested physical downlink control channel parameter from the terminal device; and transmit the indication of the at least one requested physical downlink control channel parameter to the access node.

[0017] According to an example embodiment of the first aspect, the at least one requested physical downlink control channel parameter comprises an aggregation level of the physical downlink control channel.

[0018] According to an example embodiment of the first aspect, the data traffic comprises physical downlink control channel data and / or physical downlink shared channel data.

[0019] According to an example embodiment of the first aspect, the data traffic comprises extended reality data.

[0020] According to an example embodiment of the first aspect, the terminal device comprises a head-mountable device configured to render the extended reality data.

[0021] According to a second aspect, a terminal device is disclosed. The terminal device may comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the tethering device at least to: transmit, to a tethering device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; receive, from the tethering device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device; and receive the data traffic from the access node over the radio channel between the access node and the terminal device based on the signalling information.

[0022] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: establish a secure connection with the tethering device; and receive the signalling information from the tethering device via the secure connection.

[0023] According to an example embodiment of the second aspect, the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, and the instructions are configured to, when executed by the at least one processor, cause the terminal device to: receive, by the terminal device from the tethering device, an indication of successful switch of the terminal device to the passive listening mode; and initiate the reception of the data traffic from the access node over the radio channel between the access node and the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode.

[0024] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: power down uplink transmission circuitry of the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode, wherein the uplink transmission circuitry is meant for uplink transmission directly towards the access node.

[0025] According to an example embodiment of the second aspect, the signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

[0026] According to an example embodiment of the second aspect, the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

[0027] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: detect the data traffic from a signal transmitted by the access node using the at least one identifier of the tethering device, and / or decrypt the data traffic based on the at least one security key.

[0028] According to an example embodiment of the second aspect, the data traffic comprises a plurality of data packets, and the instructions are configured to, when executed by the at least one processor, cause the terminal device to: receive, from the tethering device, at least one data packet of the data traffic; combine data of the at least one data packet received from the tethering device with data of at least one data packet not successfully decoded by the terminal device from a direct radio connection to the access node.

[0029] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: transmit, to the tethering device, a request for at least one data packet of the data traffic not successfully decoded by the terminal device.

[0030] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: combine data of the at least one data packet not successfully decoded by the terminaldevice with data of the at least one data packet requested and received from the tethering device.

[0031] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: transmit, to the tethering device, information on link quality between the access node and the terminal device.

[0032] According to an example embodiment of the second aspect, the information on the link quality between the access node and the terminal device comprises at least one of the following: data packet retransmission feedback information of the terminal device, channel state information of the terminal device indicative of a state of the radio channel between the access node and the terminal device, reference signal received power at the terminal device.

[0033] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: transmit an indication of at least one requested physical downlink control channel parameter to the tethering device.

[0034] According to an example embodiment of the second aspect, the at least one requested physical downlink control channel parameter comprises an aggregation level of the physical downlink control channel.

[0035] According to an example embodiment of the second aspect, the data traffic comprises physical downlink control channel data and / or physical downlink shared channel data.

[0036] According to an example embodiment of the second aspect, the data traffic comprises extended reality data.

[0037] According to an example embodiment of the second aspect, the terminal device comprises a head-mountable device, and the instructions are configured to, when executed by the at least one processor, cause the head-mounted device to: render the extended reality data.

[0038] According to an example embodiment of the second aspect, the instructions are configured to, when executed by the at least one processor, cause the terminal device to: decode the data traffic without a subscription to the communication network.

[0039] According to a third aspect, a method is disclosed. The method may comprise: receiving, by a tethering device from a terminal device, a request for the terminal deviceto operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; and transmitting, by the tethering device to the terminal device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.

[0040] According to an example embodiment of the third aspect, the method comprises: establishing, by the tethering device, a secure connection with the terminal device; and transmitting, by the tethering device, the signalling information to the terminal device via the secure connection.

[0041] According to an example embodiment of the third aspect, the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, the method further comprising: transmitting, by the tethering device to the terminal device, an indication of successful switch of the terminal device to the passive listening mode.

[0042] According to an example embodiment of the third aspect, the signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

[0043] According to an example embodiment of the third aspect, the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

[0044] According to an example embodiment of the third aspect, the method comprises: receiving, by the tethering device, the data traffic from the access node, wherein the data traffic comprises a plurality of data packets; and transmitting, by the tethering device to the terminal device, at least one data packet of the data traffic.

[0045] According to an example embodiment of the third aspect, the method comprises: receiving, from the terminal device, a request for at least one data packet not successfully decoded by the terminal device; and transmitting, based on the request, to the terminal device, the at least one data packet.

[0046] According to an example embodiment of the third aspect, the method comprises: receiving, by the tethering device from the terminal device, information on link quality between the access node and the terminal device; and transmitting, by the tethering device to the access node, link quality information comprising: a combination of information on link quality between the access node and the tethering device and theinformation on the link quality between the access node and the terminal device, or the information on the link quality between the access node and the terminal device.

[0047] According to an example embodiment of the third aspect, the information on the link quality between the access node and the terminal device comprises at least one of the following: data packet retransmission feedback information of the terminal device, channel state information of the terminal device indicative of a state of the radio channel between the access node and the terminal device, or reference signal received power at the terminal device.

[0048] According to an example embodiment of the third aspect, the method comprises: combining, by the tethering device, the channel state information of the terminal device with channel state information of the tethering device indicative of a state of a radio channel between the access node and the tethering; or combining, by the tethering device, the data packet retransmission feedback information of the terminal device with data packet retransmission feedback information of the tethering device based on transmitting, to the access node, a retransmission request for data packets not successfully decoded by both the terminal device and the tethering device and not transmitting a retransmission request for data packets successfully decoded by either the terminal device or the tethering device.

[0049] According to an example embodiment of the third aspect, the method comprises: combining the channel state information of the terminal device with the channel state information of the tethering device based on selecting channel state information that is indicative of weakest or strongest radio channel conditions among the channel state information of the terminal device and the channel state information of the tethering device.

[0050] According to an example embodiment of the third aspect, the method comprises: receiving, by the tethering device, an indication of at least one requested physical downlink control channel parameter from the terminal device; and transmitting, by the tethering device, the indication of the at least one requested physical downlink control channel parameter to the access node.

[0051] According to an example embodiment of the third aspect, the at least one requested physical downlink control channel parameter comprises an aggregation level of the physical downlink control channel.

[0052] According to an example embodiment of the third aspect, the data traffic comprises physical downlink control channel data and / or physical downlink shared channel data.

[0053] According to an example embodiment of the third aspect, the data traffic comprises extended reality data.

[0054] According to an example embodiment of the third aspect, the terminal device comprises a head-mountable device configured to render the extended reality data.

[0055] According to a fourth aspect, a method is disclosed. The method may comprise: transmitting, by a terminal device to a tethering device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; receiving, by the terminal device from the tethering device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device; and receiving, by the terminal device, the data traffic from the access node over the radio channel between the access node and the terminal device based on the signalling information.

[0056] According to an example embodiment of the fourth aspect, the method comprises: establishing, by the terminal device, a secure connection with the tethering device; and receiving, by the terminal device, the signalling information from the tethering device via the secure connection.

[0057] According to an example embodiment of the fourth aspect, the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, the method further comprising: receiving, by the terminal device from the tethering device, an indication of successful switch of the terminal device to the passive listening mode; and initiating the reception of the data traffic from the access node over the radio channel between the access node and the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode.

[0058] According to an example embodiment of the fourth aspect, the method comprises: powering down uplink transmission circuitry of the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode, wherein the uplink transmission circuitry is meant for uplink transmission directly towards the access node.

[0059] According to an example embodiment of the fourth aspect, signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

[0060] According to an example embodiment of the fourth aspect, the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

[0061] According to an example embodiment of the fourth aspect, the method comprises: detecting the data traffic from a signal transmitted by the access node using the at least one identifier of the tethering device, and / or decrypting the data traffic based on the at least one security key.

[0062] According to an example embodiment of the fourth aspect, the data traffic comprises a plurality of data packets, the method further comprising: receiving, from the tethering device, at least one data packet of the data traffic; combining data of the at least one data packet received from the tethering device with data of at least one data packet not successfully decoded by the terminal device from a direct radio connection to the access node.

[0063] According to an example embodiment of the fourth aspect, the method comprises: transmitting, by the terminal device to the tethering device, a request for at least one data packet of the data traffic not successfully decoded by the terminal device.

[0064] According to an example embodiment of the fourth aspect, the method comprises: combining, by the terminal device, data of the at least one data packet not successfully decoded by the terminal device with data of the at least one data packet requested and received from the tethering device.

[0065] According to an example embodiment of the fourth aspect, the method comprises: transmitting, by the terminal device to the tethering device, information on link quality between the access node and the terminal device.

[0066] According to an example embodiment of the fourth aspect, the information on the link quality between the access node and the terminal device comprises at least one of the following: data packet retransmission feedback information of the terminal device, channel state information of the terminal device indicative of a state of the radio channel between the access node and the terminal device, or reference signal received power at the terminal device.

[0067] According to an example embodiment of the fourth aspect, the method comprises: transmitting, by the terminal device, an indication of at least one requested physical downlink control channel parameter to the tethering device.

[0068] According to an example embodiment of the fourth aspect, the at least one requested physical downlink control channel parameter comprises an aggregation level of the physical downlink control channel.

[0069] According to an example embodiment of the fourth aspect, the data traffic comprises physical downlink control channel data and / or physical downlink shared channel data.

[0070] According to an example embodiment of the fourth aspect, the data traffic comprises extended reality data.

[0071] According to an example embodiment of the fourth aspect, the terminal device comprises a head-mountable device, the method further comprising: rendering the extended reality data by the head-mountable device.

[0072] According to an example embodiment of the fourth aspect, the method comprises: decoding, by the terminal device, the data traffic without a subscription to the communication network.

[0073] According to a fifth aspect, an apparatus is disclosed. The apparatus may comprise means for performing a method according to the third or fourth aspect, or any example embodiment(s) thereof.

[0074] According to a sixth aspect, a computer program, a computer program product, or a (non-transitory) computer-readable medium is disclosed. The computer program, computer program product, or (non-transitory) computer-readable medium may comprise instructions, which when executed by an apparatus, cause the apparatus at least to perform the method according to the third or fourth aspect, or any example embodiment(s) thereof.

[0075] Example embodiments of the present disclosure can thus provide apparatuses, methods, computer programs, computer program products, or computer readable media for improving various aspects of wireless tethering. Any example embodiment may be combined with one or more other example embodiments. These and other aspects of the present disclosure will be apparent from the example embodiment(s) described below. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.DESCRIPTION OF THE DRAWINGS

[0076] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:

[0077] FIG. 1 illustrates an example of a communication network;

[0078] FIG. 2 illustrates an example of a device configured to practice one or more example embodiments;

[0079] FIG. 3 illustrates examples of communication between a terminal device, a tethering device, and an access node;

[0080] FIG. 4 illustrates an example of communication between an access node, a tethering device, and a terminal device configured to passively listen downlink data traffic;

[0081] FIG. 5 illustrates an example of signalling and operations for enabling a terminal device to listen to data traffic transmitted by an access node to a tethering device;

[0082] FIG. 6 illustrates an example of a data packet flow at an access node, a tethering device, and a terminal device;

[0083] FIG. 7 illustrates an example of a method for enabling a terminal device to receive data traffic transmitted by an access node to a tethering device; and

[0084] FIG. 8 illustrates an example of a method for receiving, by a terminal device, data traffic transmitted by an access node to a tethering device.

[0085] Like references are used to designate like parts in the accompanying drawings.DETAILED DESCRIPTION

[0086] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0087] FIG. 1 illustrates an example of a communication network. Communication network 100 may comprise one or more access nodes 122, 124, 126. Access node(s) 122, 124, 126 may be part of a radio access network 120 (RAN) configured to enable a tethering device 110 and a terminal device 112 to access communication services provided by core network 130. Terminal device 112 may be configured to be wirelessly connected to tethering device 110, in order to enable terminal device 112 to communicate with access node(s) 122, 124, 126 and core network 130 via tethering device 110. The connection between tethering device 110 and terminal device 112 may be implemented based on any suitable system or protocol, for example a 3rdGeneration Partnership (3 GPP) protocol or a non-3GPP protocol. Tethering device 110 and terminal device 112 may be also referred to as apparatus or user equipment (UE). Transmission by an access node to a UE may be called downlink (DL) transmission. Transmission by a UE to an access node may be called uplink (UL) transmission. In the example of 3GPP 5G specifications, the interface between a UE and an access node may be called the Uu interface.

[0088] A tethering device 110 may be referred to as a first terminal device, and a terminal device 112 may be referred to as a second terminal device.

[0089] In context of extended reality (XR) applications, terminal device 112 may be referred to as an XR device. XR provides new experiences for immersive media services. One device type enabling XR applications is XR glasses. The form factors of the devices might not significantly deviate from those of non-XR glasses, which may be referred to as normal eyeglasses. Small form factor results in less physical space for the various required components such as sensors, circuit boards, antennas, cameras, or batteries, for example when compared with smartphones. Such physical limitations may reduce the media processing and communication capabilities supported by AR / MR glass devices, in some cases requiring XR devices to offload certain processing functions to a tethered device and / or a server.

[0090] Wireless tethering of XR devices may be used for enhancing the XR experience. Examples of possible wireless tethering options are provided in the following table. The first column indicates the type of terminal device 112. The second column indicates examples of possible technologies for the connection between tethering device 110 and terminal device 112 (XR device). The third column indicates whether data communication circuitry, in this example the 5G Uu interface modem, is located at terminal device 112 or external to terminal device 112, for example at a puck, mobilephone, smartphone, or other external / remote device communicatively coupled to terminal device 112. The fourth column indicates whether the XR engine, which may be configured to process the received XR data, is located at terminal device 112, device external to terminal device 112, or split between terminal device and an external device. The fifth column indicates whether the power supply is internal or external to the terminal device 112. The sixth column indicates examples of maximum power available for consumption.

[0091] Terminal device 112 may be embodied as a head-mountable device, such as for example a headset, a head-mountable display (HMD), smart glasses, see-through glasses, or the like. The head-mountable device may be configured to render the XR data. Asnoted above, examples of terminal device 112 include both simple and smart VR / AR viewer devices. A smart VR viewer device may include sensors for tracking position and / or orientation of the device, a display, a wireless connection (e.g., a WiFi based or 5G sidelink based connection), at least some XR processing, and a power supply. An external device (e.g., a remote device) may be configured to perform remaining processing of the XR data. Also devices referred to as VR HMD standalone devices may be configured to operate as terminal device 112. For such devices, a cellular modem (e.g., 5G modem), the power supply, as well as (all) XR-related media processing may be integrated into a single device. Terminal device 112 may be also embodied as a hybrid XR device having a cellular modem and the ability to connect to the network both directly and via a tethered link.

[0092] Tethering device 110 and / or terminal device 112 may be configured to communicate with access node(s) 122, 124, 126 over a radio interface, which may be also referred to as an air interface. The radio interface may be configured for example based on the 5G NR (New Radio) standard defined by the 3rdGeneration Partnership Project (3GPP). Communication network 100 may therefore comprise a wireless communication network or a mobile communication network, such as for example a cellular communication network.

[0093] Core network 130 may be implemented with various network functions, including for example one or more user plane functions (UPF) and one or more access and mobility management functions (AMF). A UPF may be configured to handle user data part of a communication session. A UPF may thus provide an interconnect point between the radio access network and a data network configured to provide application services to tethering device 110 or terminal device 112 via core network 130 and RAN 120. For example, a UPF may be configured to handle encapsulation and decapsulation of user plane protocol(s), such as for example the GPRS (general packet radio service) tunnelling protocol for the user plane (GTP-U). An AMF may be configured to receive connection and session request related data from tethering device 110 (via an access node). An AMF may be configured to control connection and mobility management in the wireless communication network.

[0094] Communication network 100 may comprise other network function(s), network device(s), or protocol(s), in addition, or alternative to, those illustrated in FIG. 1. A network device may be configured to implement functionality of one or morenetwork functions. Even though some embodiments have been described in the context of 5G, it is appreciated that embodiments of the present disclosure are not limited to this example network. Example embodiments may be therefore applied in any present or future communication networks. A device may comprise, or be configured to implement, e.g. by means of software, one or more of the protocol layers described herein.

[0095] FIG. 2 illustrates an example of a device configured to practice one or more example embodiments. Device 200 may comprise a tethering device 110, a terminal device 112, an access node, an access point, base station, a radio network node, or a split portion thereof, or in general a device configured to implement functionality described herein. Device 200 may comprise at least one processor 202. The at least one processor 202 may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0096] Device 200 may further comprise at least one memory 204. The memory 204 may be configured to store, for example, computer program code or the like, for example operating system software and application software. Memory 204 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the memory may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). Memory 204 is provided as an example of a (non-transitory) computer readable medium. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0097] Device 200 may further comprise a communication interface 208 configured to enable device 200 to transmit and / or receive information. Communication interface 208 may comprise an external communication interface, such as for example a radio interface (e.g., Uu interface) between an access node and a UE and / or a tethering interface, e.g., a sidelink, between tethering device 110 and terminal device 112 . Communication interface 208 may comprise one or more radio transmitters or receivers,which may be coupled to one or more antennas or device 200, or be configured to be coupled to one or more antennas external to device 200.

[0098] Device 200 may further comprise other components and / or functions such as for example a user interface (not shown) comprising at least one input device and / or at least one output device. The input device may take various forms such a keyboard, a touch screen, or one or more embedded control buttons. The output device may for example comprise a display, a speaker, or the like.

[0099] When device 200 is configured to implement some functionality, some component and / or components of device 200, such as for example the at least one processor 202 and / or the at least one memory 204, may be configured to implement this functionality. Furthermore, when the at least one processor 202 is configured to implement some functionality, this functionality may be implemented using program code 206 comprised, for example, in the at least one memory 204.

[0100] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an example embodiment, device 200 comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code 206, when executed, to execute the embodiments of the operations and functionality described herein. Program code 206 is provided as an example of instructions which, when executed by the at least one processor 202, cause performance of device 200.

[0101] Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), graphics processing units (GPUs), or the like.

[0102] Device 200 may be configured to perform, or cause performance of, method(s) described herein or comprise means for performing method(s) described herein. In one example, the means comprises the at least one processor 202, the at least one memory 204 including instructions (e.g., program code 206) configured to, when executed by the at least one processor 202, cause apparatus 300 to perform the method(s). In general, computer program instructions may be executed on means providing generic processingfunctions. Such means may be embedded for example in a personal computer, a smart phone, a network device, or the like. The method(s) may be thus computer-implemented, for example based algorithm(s) executable by the generic processing functions, an example of which is the at least one processor 202. The means may comprise transmission or reception means, for example one or more radio transmitters or receivers, which may be coupled or be configured to be coupled to one or more antennas. Device 200 may comprise, for example, a network device, for example, an access node, an access point, a base station, or a central / distributed unit thereof. Although device 200 is illustrated as a single device, it is appreciated that, wherever applicable, functions of device 200 may be distributed to a plurality of devices.

[0103] FIG. 3 illustrates examples of communication between a terminal device, a tethering device, and an access node. In the example of FIG. 3(a), terminal device 112 is not capable of directly communicating with access node 122, for example due to lack of necessary data communication circuitry (e.g., a required cellular modem) or lack of subscription to communication network 100. Terminal device 112 may for example comprise a smart VR viewer device with wireless tethering. Terminal device 112 may be therefore configured to use subscription of tethering device 110 for communicating with access node 122. Terminal device 112 may be configured to exploit tethering device 110 for both uplink (UL) and downlink (DL) communication with access node 122 via the tethered communication link. In this example, terminal device 112 may leverage the processing power and cellular connectivity to a tethering device at the cost of dependency on the tethering device for providing the XR experience. Furthermore, the arrangement of FIG. 3(a) may cause an additional delay, e.g. a tethering delay, as part of total delay budget.

[0104] In the example of FIG. 3(b), terminal device 112 has no such dependency, because it has an integrated cellular modem and the ability to directly communicate with access node 122 (e.g., own subscription to communication network 100). Greater mobility may be therefore offered. Terminal device 112 may for example comprise a VR HMD standalone device. Due to limited space, such a device may have lower processing power, connectivity speed, and / or power, when for example compared to a smartphone. On the other hand, the direct connection enables to avoid the tethering delay. A direct connection may refer to a direct radio connection, where signals are communicated between antennas of the associated devices over an air interface, without involvement of any intermediary device. A direct radio connection may be a unidirectional radioconnection, for example a radio connection not involving any connection establishment procedure between the associated devices (e.g., terminal device 112 and access node 122).

[0105] Design aspects of terminal device 112 may include cost, weight, and power consumption (including device’s heating) of terminal device 112, when it is equipped with a cellular modem (cf. , FIG. 3(a)) or without it (cf. , FIG. 3(b)). In general, the cost, weight, and power consumption of tethering circuitry compared to a cellular modem may be much lower. Thus, a 5G equipped terminal device may be supplemented with tethering circuitry, in order to take advantage of the mobility offered by the 5G connection as well as leverage the superior capabilities of a smartphone. The hybrid XR device of FIG. 3(c) may be therefore configured with functionality of both FIG. 3(a) and FIG. 3(b). The arrangement of FIG. 3(c) may be referred to as a tethering group. Terminal device 112 may therefore have an integrated cellular modem and the ability to connect to the network both directly and via the tethered link. With such a device type there are multiple configurations, in which terminal device 112 can improve usage of available connectivity options, some of them being listed below as examples:

[0106] Configuration 1 : Terminal device 112 may have its own cellular subscription. Terminal device 112 may communicate with the network using a direct radio link. Terminal device 112 may additionally use the tethering link between terminal device 112 and tethering device 110 to enhance the XR experience in the uplink and downlink. Terminal device 112 may be still able to directly communicate with the access node 122.

[0107] Configuration 2: Terminal device 112 does not have its own cellular subscription. Terminal device 112 may use subscription of tethering device 110 for uplink and / or downlink communication with the network using the tethered link. Terminal device 112 may communicate with the network (access node 122) only via the tethering link.

[0108] Configuration 3: Terminal device 112 does not have its own cellular subscription. Terminal device 112 may use the subscription of tethering device 110 at least for uplink communication with the network using the tethered link. In addition, terminal device 112 may use its cellular modem for enhancing downlink communication with the network.

[0109] Any of the above configurations may be selected for a device equipped with both a cellular modem and tethering circuitry.[001 10] Considering a scenario where terminal device 112 of FIG. 3(a) is also equipped with a cellular modem, with Configuration 2 it might not be possible to make use of the additional link between terminal device 112 and access node 122 (the direct radio link) and therefore the cellular modem of terminal device 112 is not used. With Configuration 1 it is possible to benefit from the direct radio link, but this comes at the cost of additional complexity and power consumption in the uplink. Some challenges arise when combining functionality Configurations 1 and 2 to yield Configuration 3. For example, any direct communication with access node 122 may require subscription, in order to enable decoding of downlink data. On the other hand, uplink routing through tethering device 110 enables lower uplink power to be used at terminal device 112, or avoiding including uplink transmission circuitry (hardware) for the cellular modem entirely on terminal device 112.[001 1 1 ] Example embodiments of the present disclosure address some of the challenges of operation based on Configuration 3 by configuring terminal device 112 to operate as a passive listener of downlink data traffic transmitted by access node 122 to tethering device 110 without need to use a cellular subscription to the network at the terminal device 112, or without need for even having a cellular subscription to the network at terminal device 112, as will be further described with reference to FIG. 4 and FIG. 5. Uplink data traffic generated by terminal device 112 may be routed to access node 122 via the tethering device 110, similar to Configuration 2.[001 12] FIG. 4 illustrates an example of communication between an access node, a tethering device, and a terminal device configured to passively listen downlink data traffic. Tethering device 110 may be configured to access application services via RAN 120 comprising one or more access nodes, for example access node 122. Terminal device 112 may be configured to transmit uplink data traffic to access node 122 via tethering device 110. In other words, uplink data traffic from terminal device may be routed to access node 122 via the tethering link between terminal device 112 and tethering device 110. Terminal device 112 may be configured to receive downlink traffic from access node 122 via tethering device 110. In other words, downlink data traffic from access node 122 may be routed to terminal device 122 via the tethering link between tethering device 110 and terminal device 112. In other words, tethering device 110 may be configured to receive downlink data traffic from access node 122 via a direct radio link and to forward the received downlink data traffic from access node 122 to terminal device 112 via the tethering link between tethering device 110 and terminal device 112. The forwarding ofdata traffic from tethering device 110 and terminal device 112 may be on-demand based on an explicit request from terminal device 112. Terminal device 112 may be configured to receive the downlink data traffic transmitted by access node 122 to tethering device 110. The reception of DL data traffic by terminal device 112 transmitted by access node 122 to tethering device 110 may be referred to as passive listening by terminal device 112. In addition to that, tethering device 110 may be configured to transmit its own uplink data traffic to, and receive its own downlink data traffic from, access node 122.[001 1 3] Tethering device 110 may initially establish a secure connection with terminal device 112. Tethering device 110 may exchange, with terminal device 112, tethering support information, in order to enable terminal device 112 to perform passive listening of the downlink data traffic transmitted by access node 122 to tethering device 110. Passive listening may comprise detecting and decoding transmissions of access node 122 targeted to tethering device 110. Tethering support information transmitted by tethering device 110 to terminal device 112 may include, for example, identified s) of tethering device 110, e.g., a cell radio network temporary identifier (C-RNTI), security key(s)s, or other physical and / or higher layer configurations configured for downlink communication between access node 122 and tethering device 110, as will be further described below. If terminal device 112 is not able to decode at least part of the downlink data traffic, on-demand forwarding of missed downlink data packets to terminal device 110 may be provided by tethering device 110, as will be further described below. Decoding may include forward error correction (FEC) decoding and / or checking an error detection code such as for example a cyclic redundancy check (CRC) code.[001 14] FIG. 5 illustrates an example of signalling and operations for enabling a terminal device to listen to data traffic transmitted by an access node to a tethering device. Terminal device 112 may comprise a cellular modem, e.g., a cellular modem configured to operate based on a particular standard, or version or profile thereof. Operations described with reference to FIG. 5 enable terminal device 112 to operate as passive listener of downlink data traffic targeted to tethering device 110. Tethering device 110 may be authenticated with respect to core network 130 via the radio interface between tethering device 110 and access node 122 (e.g., Uu interface). Terminal device 112 may be configured to listen to the Uu interface for downlink transmissions. Terminal device 112 may be configured to exploit tethering device 110 for transmission of uplink data to access node 122. Even though certain aspects have been described in context of 3GPPnetworks, it is appreciated that similar functionality may be configured also in any non- 3 GPP system.[001 1 5] At operation 501, tethering device 110 may establish a connection with access node 122, or in general communication network 100. In the example of 3GPP 5G system, this operation may include connection establishment in the Uu interface. In general, tethering device 110 may establish a radio connection to access node 122.[001 16] At operation 502, a non-access stratum (NAS) procedure may be completed between tethering device 110 and core network 130.[001 1 7] At operation 503, terminal device 112 may connect to tethering device 110 using a tethering link. The tethering link may comprise any suitable communication link between tethering device 110 and terminal device 112, for example a sidelink interface such as a 3 GPP PC5 interface or a short-range wireless interface such as a WIFI interface or a Bluetooth interface. The tethering link may be provided as a personal internet-of- things (loT) network (PIN). Connecting to tethering device 110 may therefore comprise PC5 connection establishment, as illustrated by operation 504.[001 18] At operation 505, terminal device 112 may transmit a request for operating as a listener to data traffic transmitted by access node 122 to tethering device 110. The request may be, for example, transmitted as a device mode switch request. The request may be indicative of terminal device 112 requesting to enter a passive listening mode. The request may comprise a request for passive listening (PL) assistance information, for example as a particular value (e.g., ‘YES’) of a signalling field (e.g., a flag such as passive listening assistance info sharing), which may be included in the request or transmitted separately. The request may further comprise a request for a secure connection between terminal device 112 and tethering device 110, for example as a particular value (e.g., ‘YES’) of a signalling field (e.g., a flag such as secure mode), which may be included in the request or transmitted separately. The passive listening assistance information may comprise signalling information configured to enable terminal device 112 to receive, over a radio channel between access node 122 and terminal device 112, the data traffic transmitted by access node 122 to tethering device 110. This enables terminal device 112 to notify tethering device 110 that it wants to operate in the passive listening mode. It also enables terminal device 112 to inform tethering device 110 about the need for the assistance information for enabling operation in the passive listening mode. The passive listening assistance information may be generally referred to as signalling information or tethering support information.[001 19] Alternatively, terminal device 112 may be configured to enter the passive listening mode, in response to or based on receiving a request to enter the passive listening mode from tethering device 112. This enables tethering device 110 to instruct terminal device to initiate the passive listening of the downlink data traffic targeted to tethering device 110 without the terminal device 112 requesting the switch to the passive listening mode.

[0120] At operation 506, a secure connection may be established between terminal device 112 and tethering device 110. The secure connection established by the devices may comprise a secure communication channel, for example a communication channel protected by data encryption. Establishing the secure connection may comprise exchange of security data (e.g., encryption keys) between terminal device 112 and tethering device 110 and configuration of the security data at terminal device 112 and / or tethering device 110 for communication between the devices. For example, terminal device 112 may be configured to receive security data from tethering device 110 and configure its communication with tethering device 110 based on the received security data, or vice versa.

[0121] At operation 507, tethering device 110 may transmit the passive listening (PL) assistance information to terminal device 112, for example in a passive listening assistance information sharing request message, as illustrated in FIG. 5. The passive listening assistance information may comprise signalling information configured to enable terminal device 112 to receive the (downlink) data traffic transmitted by access node 122 and targeted (e.g., addressed) to tethering device 110. The passive listening assistance information may be transmitted as a container, for example on the secure communication channel established at operation 506.

[0122] The passive listening assistance information may be configured to enable reception of particular downlink channel(s), for example a physical downlink shared channel (PDSCH). The PDSCH may be shared with multiple devices (e.g., UEs). The PDSCH may include downlink data for multiple devices, for example tethering device 110 and at least one other device which is not terminal device 112. Tethering device 110 may be configured to extract data targeted to itself from the PDSCH based on identified s) of tethering device 110, for example C-RNTI. The passive listening assistance information may comprise the identified s) of tethering device 110, for example the C- RNTI. This provides the benefit of enabling terminal device 112 to detect and extract data targeted to tethering device 110 from the PDSCH when passively listening to the PDSCH.

[0123] Based on the passive listening assistance information (e.g., the identified s) of tethering device 110), terminal device 112 may receive downlink control channel data (e.g., data of a physical downlink control channel, PDCCH) targeted to tethering device 110. By decoding the downlink control channel data, terminal device 112 may obtain information (e.g., data reception / decoding parameters) for receiving / decoding the PDSCH data. The passive listening assistance information may comprise security key(s) configured to enable decryption of the data traffic targeted to tethering device 110. The security key(s) may for example comprise at least one of the following keys: XNASAint, wsenc. Xupint, iuPenc, where ‘int’ refers to an integrity protection key and ‘enc’ refers to an encryption key. These keys may be dedicated for protecting the NAS layer and user plane (UP) communication, respectively. Some security key(s), such as for example NAS keys xASAintand XNASenc, may be generated by core network 130 (e.g., by an AMF) and delivered to access node 122 and tethering device 110, which may forward the security key(s) to terminal device 112 over the tethering link. Some keys, such as for example user plane keys Xupint and Xupenc, may be generated by a UE, in this case tethering device 110, and provided to terminal device 112 over the tethering link.

[0124] The passive listening assistance information may comprise further physical and higher layer configurations for downlink communication between access node 122 and tethering device 110. In general, the passive listening assistance information may comprise (a subset of) information elements (IE) configured at tethering device 110 for establishing a connection between tethering device 110 and access node 122, examples of which include the identified s) of tethering device 110 and the security key(s). It is noted that all configuration information associated with the connection between access node 122 and tethering device 110 need not be included in the passive listening assistance information and therefore a subset of the IES configured at tethering device 110 for establishing the connection may be provided to terminal device 112. This provides the benefit of reducing the signalling overhead at the tethering link. Tethering device 110 may be configured to transmit the passive listening assistance information via the secure connection established at operation 506.

[0125] At operation 508, terminal device 112 may transmit, to tethering device 110, an acknowledgement of reception of the passive listening assistance information, for example as passive listening assistance information sharing response message. The passive listening assistance information sharing response message may include an indication of successful reception of the passive listening assistance information, forexample by a particular value (e.g., “success”) of an information field of the response message. This enables tethering device 110 to be informed about ability of terminal device 112 to enter the passive listening mode.

[0126] Tethering device 110 may be configured to switch terminal device 112 to the passive listening mode. This may be in response to or based on receiving the indication of successful reception of the passive listening assistance information from terminal device 112. Switching terminal device 112 to the passive listening mode may comprise terminating forwarding of downlink data packets to terminal device 112. Some data packets may be however still forwarded to terminal device 112 upon request, for example in case of unsuccessful reception of data packets at terminal device 112 directly from access node 122.

[0127] At operation 509, terminal device 112 may store the passive listening assistance information, e.g., content of the received passive listening assistance information container. Terminal device 112 may securely store the passive listening assistance information in a secure storage. Terminal device 112 may configure its data communication circuitry, e.g., its cellular modem, for receiving / decoding data traffic targeted to tethering device 110, for example from the PDSCH. The data traffic may comprise a plurality of data packets, e.g., a sequence of data packets.

[0128] At operation 510, tethering device 110 may transmit an indication of successful switch of terminal device 112 to the passive listening mode, for example as a device mode switch response message. This enables terminal device 112 to be informed that tethering device is configured to regard terminal device 112 as operating in the passive listening mode,. For example, tethering device 110 may be configured not to forward downlink data packets to terminal device 112 unless specifically requested by terminal device 112. Based on this indication terminal device 112 may however determine that tethering device 110 is still configured to relay uplink transmissions of terminal device 112 to access node 122.

[0129] At operation 511, terminal device 112 may initiate passive listening. In other words, terminal device 112 may activate the passive listening mode. This may be performed in response to or based on receiving the indication of the successful switch of terminal device 112 to the passive listening mode. Terminal device 112 may initiate reception of the data traffic from access node 122 over the radio channel, e.g. direct radio channel, between access node and terminal device 112 based on the passive listening assistance information. Note that terminal device 112 may be configured to decode thedata traffic without a subscription to the communication network, because interaction with the network is via tethering device 110. In at least some embodiments, the terminal device has the subscription to the communication network, but is configured to interact with the network via tethering device to save power, for example.[001 30] When entering the passive listening mode, terminal device 112 may initiate reception, e.g., detecting and decoding, of data traffic from access node 122. The data traffic may be targeted for tethering device 110. Terminal device 112 may therefore initiate operating as a listener, e.g. a passive listener, to data traffic between access node 122 and tethering device 110. The data traffic between access node 122 and tethering device 110 may comprise downlink data. The data traffic may be formatted as data packet(s). The data traffic may comprise PDCCH data and / or PDSCH data, or data of any other relevant physical or logical downlink channel. In context of extended reality (XR), the data may comprise XR data, such as for example three-dimensional video data or other visual or audible data configured to be output by a head-mountable device.[001 31 ] Based on the passive listening assistance information conveyed by tethering device 110 to terminal device 112, e.g., the C-RNTI, terminal device 112 may attempt to decode the downlink data traffic. Terminal device 112 may be configured to detect the data traffic from the signal transmitted by access node 122 using the identified s) of tethering device 110. Terminal device 112 may use the identified s) (e.g., C-RNTI) shared by tethering device 110 to identify data packets targeted to tethering device 110 and / or to unscramble them. Terminal device 112 may be configured to decode the downlink data based on the C-RNTI and / or security key(s) received from tethering device 110. For example, terminal device 112 may be configured to decrypt the data traffic, e.g., data packets, based on the security key(s) received from tethering device 110. Terminal device 112 may use the received key(s) (e.g., Kupenc, Kupint) for integrity check and decryption of user plane (UP) or control plane (CP) data packets.[001 32] Terminal device 112 may pass successfully decoded physical layer data to higher protocol layers, such as for example the medium access control (MAC) layer (MAC), radio link control (RLC) layer, or packet data convergence protocol (PDCP) layer for further processing by terminal device 112. Terminal device 112 may be configured to request missed or unsuccessfully received data packets from tethering device 110, as will be further described with reference to operation 512. For example, in case either PDCCH data or PDSCH data is not successfully decoded by terminal device, terminal device mayrequest tethering device 110 to forward the corresponding data packet(s) to terminal device 112.[001 33] Terminal device 112 may be further configured to power down its uplink transmission circuitry meant for uplink transmission directly towards access node 122 in the passive listening mode. Powering down the uplink transmission circuity may be performed in response to or based on terminal device 112 receiving the indication of the successful switch to the passive listening mode at operation 510. Powering down the uplink transmission circuitry may comprise switching off or otherwise reducing power consumption of the uplink transmission circuitry meant for uplink transmission directly towards access node 122. For example, the uplink transmission circuitry may be transitioned into a power-down mode, where ability of the uplink transmission circuitry to transmit data to access node 122 is disabled or restricted. This provides the benefit of reducing power consumption of terminal device 112, because the uplink transmissions are relayed via tethering device 110 and therefore the required transmission power is generally lower compared to transmitting to access node 122 directly. Uplink transmission circuitry meant for transmission to tethering device 110 might not be switched off. Transmission between terminal device 112 and tethering device 110 may be based on device to device, D2D, protocol, for example, Bluetooth, WiFi or sidelink communication. Communication between the terminal device and access node 122 may be implemented using a transceiver, for example, such as 5 G transceiver. UL circuitry of the transceiver may be powered down based on terminal device receiving the indication of the successful switch to the passive listening mode. DL circuitry of the transceiver is not switched off. Operations 512 and 513 relate to functionality of terminal device 112 and tethering device 110, when terminal device 112 detects a packet error. A packet error may be detected when a data packet is missed or when a data packet is erroneously decoded.[001 34] At operation 512, terminal device 112 may transmit a request for data packet(s) not successfully decoded by terminal device 112. The data traffic may again comprise the data traffic between access node 122 and tethering device 110, which is passively listened by terminal device 112. A data packet that is not successfully decoded may comprise a data packet which is missing or which is erroneously decoded. The request may comprise an indication (e.g., identifier(s)) of the requested data packet(s), for example sequence number(s) of the requested data packet(s). Alternatively, tethering device 112 may be configured to forward received data packets to terminal device 112 by default. Thisprovides the benefit of enabling terminal device 112 to combine data packets received by terminal device 112 over the direct radio connection with data packets received via tethering device 110. Terminal device 112 may be configured to transmit, to tethering device, an indication (e.g., identifier(s)) of data packet(s) that are not to be forwarded to terminal device 112 by tethering device 110. Terminal device 112 may be configured to transmit such indication for data packet(s) successfully decoded from the direct connection to access node 120.[001 35] At operation 513, tethering device 110 may transmit the requested data packet(s) to terminal device 112. The requested data packet(s) may be available at tethering device 110, if successfully received from access node 122 by tethering device 110. When terminal device 112 operates in the passive listening mode, tethering device 110 may be configured to store, e.g. temporarily store, data packet(s) received from access node 122 in a data buffer, which may be referred to as a tethering buffer. Tethering device 110 may be configured to retrieve respective data packet(s) from the tethering buffer upon request by terminal device 112.[001 36] Terminal device 112 may be configured to forward the data packet(s) requested and received from tethering device 110 to higher protocol layers as such. Diversity of reception is improved, because terminal device 112 may correctly receive a data packet, if the data packet is correctly received either by terminal device 112 itself or by tethering device 110. This mode of operation may be referred to as diversity combining.[001 37] Alternatively, terminal device 112 may be configured to combine data of the data packet(s) requested and received from tethering device 110 with corresponding data packets not successfully decoded, when received directly from access node 122. For this reason, tethering device 110 may be configured to store also erroneously received or decoded data packets in its tethering buffer for subsequent delivery to terminal device 112. This provides the benefit of improved diversity as the combination may enable terminal device 112 to restore data packets that were erroneously received by both terminal device 112 and tethering device 110. Combining may comprise soft combining, or any other combination method at any suitable protocol layer.[001 38] At operation 514, terminal device 112 may transmit passive listening assistance feedback to tethering device 110. For example, terminal device may transmit data packet retransmission feedback information of the terminal device to tethering device. For example, terminal device may indicate to tethering device whether the data packet has been successfully decoded at terminal device. For example, the passive listeningassistance feedback may comprise the data packet retransmission feedback information. Data packet retransmission feedback information may indicate whether the data packet has been successfully decoded at terminal device 112. For example, the passive listening assistance feedback may comprise information on radio link quality between access node 122 and terminal device 112. This link quality information (LQI) may comprise the data packet retransmission feedback information (e.g., hybrid automatic repeat request, HARQ, feedback) of terminal device 112, for example acknowledgements (ACK) of correctly decoded (PDSCH) data packets and / or negative acknowledgements (NACK) of erroneously decoded or missing (PDSCH) data packets. The link quality information may comprise channel state information (CSI) of terminal device 112, which may be indicative of the state of the radio channel between access node 122 and terminal device 112. The CSI may indicate a frequency response of the radio channel, for example during a certain time interval. The link quality information may comprise, for example, reference signal received power (RSRP). For example, terminal device 112 may be configured to measure the received signal strength based on reference signals transmitted by access node 122. The link quality information may, for example, comprise the reference signal received power (RSRP) of access node 122 as measured by terminal device 112. In other words, the received signal strength may comprise received signal strength, at terminal device 112, of reference signal(s) transmitted by access node 122, or, access node reference signal received power at the terminal device 112. The CSI and HARQ feedback may be generally referred to as uplink control information (UCI), in this example the UCI of terminal device 112.[001 39] Providing the link quality information as feedback to tethering device 110 enables tethering device 110 to take into account the link quality between access node 122 and terminal device 112 when communicating link quality information to access node 122. Therefore, access node 122 may be caused to configure transmission of the downlink data traffic such that link quality at terminal device 112 is improved, even if access node 122 were not aware of terminal device 112.

[0140] The passive listening assistance information may comprise an indication of requested PDCCH parameter(s), such as for example the aggregation level (AL) of the PDCCH, or in general a control channel. The aggregation level may comprise a minimum aggregation level to be used for control channel transmissions by access node 122. Aggregation level may indicate the amount of physical layer time and / or frequency resources for transmit the same information. Aggregation level may therefore indicate thelevel of robustness of the data transmission. For example, aggregation level may indicate the number of control channel elements (CCE) used to carry the control channel (e.g., PDCCH).

[0141] At operation 515, tethering device 110 may combine link quality information of terminal device 112 with link quality information of tethering device 110. Tethering device 110 may be configured to combine the CSI of terminal device 112 with CSI of tethering device 110. The CSI of tethering device 110 may be indicative of the state of the radio channel between access node 122 and tethering device 110. Tethering device 110 may perform the combining based on selecting the CSI which is indicative of the weakest radio channel conditions (e.g., in terms of fading) among the CSI of terminal device 112 and the CSI of tethering device 110. This results in access node 122 configuring transmission of the downlink data traffic such that it is more likely to be correctly decoded by both tethering device 110 and terminal device 112. Reporting the weakest CSI may be beneficial for example when reporting the requested aggregation level for PDCCH. Alternatively, tethering device 110 may perform the combining based on selecting the CSI which is indicative of the strongest radio channel conditions among the CSI of terminal device 112 and the CSI of tethering device 110. This may be beneficial for example when the reported CSI is used for modulation and coding scheme (MCS) selection.

[0142] Tethering device 110 may be configured to combine the data packet retransmission (e.g., HARQ) feedback information of terminal device 112 with data packet retransmission feedback information of tethering device 110. Tethering device 110 may be configured to combine the data packet retransmission feedback based on transmitting, to access node 122, a retransmission request for data packets that were not successfully decoded by both terminal device 112 and tethering device 110 (e.g., erroneously decoded by both devices) and not transmitting a retransmission request for data packets successfully decoded by either terminal device 112 or tethering device 110. Tethering device 110 may be therefore configured to transmit the retransmission request, in response to or based on determining that both devices failed to successfully decode the associated data packet. This reduces the number of retransmissions, because retransmission is not needed if either of the devices is able to successfully decode the data packet. If terminal device 112 is not able to successfully decode a data packet, that data packet may be provided to terminal device 112 by tethering device 110.

[0143] At operation 516, tethering device 110 may be configured to transmit the link quality information to access node 122. This enables access node 122 to take into account the link quality information of terminal device 112, possibly combined with link quality information of tethering device 110, when configuring transmission of the downlink data traffic to tethering device 110. This enables transmission of the data traffic to be configured such that it is more likely to be correctly decoded by terminal device 112, and / or such that spectral efficiency is improved, when passively listening to downlink data traffic targeted to tethering device 110.

[0144] Tethering device 110 may be configured to transmit an indication of the requested PDCCH parameter(s) to access node 122. This enables transmission of the PDCCH to be configured such that it is more likely to be correctly decoded by terminal device 112, when passively listening to downlink data traffic targeted to tethering device 110. The indication may not be necessarily transmitted in the same format as received from terminal device 112.

[0145] It is noted that even though certain sequence of operations is illustrated in FIG. 5, various modifications may be made to implement functionality described herein. Some of the operations may be omitted, combined, re-ordered, or the like. For example, terminal device 112 and tethering device 110 may be configured to operate with or without the packet error detection functionality (cf. operations 512, 513) or with or without provision of the link quality information and / or the PDCCH parameters. The indications, signalling information, parameters, or the like, may be alternatively transmitted or received in signals or messages different from FIG. 5. FIG. 5 is also not intended to provide an exhaustive description of operations of terminal device 112, tethering device 110, or access node 122, and therefore various other operations may be performed before, during, or after the operations of FIG. 5.

[0146] FIG. 6 illustrates an example of a data packet flow at an access node, a tethering device, and a terminal device. Communication network 100 may be operated based on a protocol stack comprising a plurality of protocol layers. The protocol stack may be arranged based on the open systems interconnection (OSI) model or a layer model of a particular standard. In one example, the protocol stack may comprise a service data adaptation protocol (SDAP) layer, which may receive data from an application layer for transmission. The SDAP layer may be configured to exchange data with the packet data convergence protocol (PDCP) layer. The PDCP layer may be responsible of generationof data bursts comprising one or more data packets, for example based on data obtained from the SDAP layer.

[0147] The PDCP layer may provide data to one or more instances of the radio link control (RLC) layer. For example, PDCP data may be transmitted on one or more RLC transmission legs. Each RLC instance may be associated with corresponding MAC instances of the MAC layer. The MAC layer may provide a mapping between logical channels of upper layer(s) and transport channels of the physical layer, handle multiplexing and demultiplexing of MAC service data units (SDU). Furthermore, the MAC layer may provide error correction functionality based on packet retransmissions, for example according to the hybrid automatic repeat request (HARQ) process. Physically separate transmission legs may be provided by the physical (PHY) layer, also known as Layer 1 (LI). Corresponding protocol stacks may be applied at access node 122, tethering device 110, and terminal device 112, as illustrated in FIG. 6.

[0148] Application data (cf., data traffic) may be provided by core network 130 to SDAP layer of access node 122 for transmission. Access node 122 may be configured to process the data on the PDCP, RLC, MAC, and PHY layers, in order to obtain the signal to be transmitted over the Uu interface to tethering device 110. Tethering device 110 may be configured to process the signal at least on the PHY layer. However, if passive listening is configured at terminal device 112, it is able to determine and extract the data traffic targeted to tethering device 110 from the signal. Terminal device 112 may process the signal on the PHY layer and pass the decoded data to higher protocol layers (e.g., MAC, RLC, PDCP, and / or SDAP). In case of extended reality (XR), the data may be provided to an XR function of terminal device 112, for example for rendering the XR data to a user. As noted above, the tethering link may be provided by any suitable technology, such as for example PC5, WiFi, Bluetooth (BT), or other wireless interface. The tethering link may be configured to deliver both uplink and downlink data. Downlink data may be however primarily delivered directly from access node 122 to terminal device 112.

[0149] Example embodiments of the present disclosure enhance wireless tethering functionality for various applications, such as for example delivery of XR data. The disclosed set of devices and configurations may take advantage of applying a cellular (e.g., 5G) modem at both tethering device 110 and terminal device 112. This may for example enable bringing in low cost XR devices in the market. The configurations may be useful for example when the quality of both the tethered link and the direct link are below a certain threshold, for example when selection or diversity combining gain can beachieved by enabling reception at both tethering device 110 and terminal device 112. This provides the benefit of increased reliability, robustness, and spectral efficiency in downlink reception. This may be useful for example in case of virtual reality (VR) applications, which may be associated with heavy downlink traffic.[001 50] FIG. 7 illustrates an example of a method 700 for enabling a terminal device to receive data traffic transmitted by an access node to a tethering device. The method 700 may be performed by a tethering device, e.g. device 110, or by a control device configured to control the functioning thereof, when installed therein.[001 51 ] At operation 701, the method may comprise receiving, by a tethering device from a terminal device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device. [001 52] At operation 702, the method may comprise transmitting, by the tethering device to the terminal device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.[001 53] FIG. 8 illustrates an example of a method 800 for receiving, by a terminal device, data traffic transmitted by an access node to a tethering device. The method 800 may be performed by a terminal device, e.g. device 112, or by a control device configured to control the functioning thereof, when installed therein.[001 54] At operation 801, the method may comprise transmitting, by a terminal device to a tethering device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device.[001 55] At operation 802, the method may comprise receiving, by the terminal device from the tethering device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.[001 56] At operation 803, the method may comprise receiving, by the terminal device, the data traffic from the access node over the radio channel between the access node and the terminal device based on the signalling information.[001 57] Further features of the methods directly result for example from functionality of tethering device 110, terminal device 112, and access node 122, as described throughout the description, claims, and drawings, and are therefore not repeated here. An apparatus may be configured to perform or cause performance of any aspect of themethod(s) described herein. Further, a computer program or a computer program product may comprise instructions for causing, when executed by an apparatus, the apparatus to perform any aspect of the method(s) described herein. Further, an apparatus may comprise means for performing any aspect of the method(s) described herein. According to an example embodiment, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform any aspect of the method(s).[001 58] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.[001 59] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0160] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0161] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[0162] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0163] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the listof two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0164] Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

[0165] 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.

[0166] 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.

[0167] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

CLAIMS1. A tethering device, comprising: means for receiving, from a terminal device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; and means for transmitting, to the terminal device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device.

2. The tethering device according to claim 1, further comprising: means for establishing a secure connection with the terminal device; and means for transmitting the signalling information to the terminal device via the secure connection.

3. The tethering device according to claim 1 or 2, wherein the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, the tethering device further comprising: means for transmitting, to the terminal device, an indication of successful switch of the terminal device to the passive listening mode.

4. The tethering device according to any of claims 1 to 3, wherein the signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

5. The tethering device according to claim 4, wherein the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

6. The tethering device according to any of claims 1 to 5, further comprising:means for receiving the data traffic from the access node, wherein the data traffic comprises a plurality of data packets; and means for transmitting, to the terminal device, at least one data packet of the data traffic.

7. The tethering device according to claim 6, further comprising: means for receiving, from the terminal device, a request for at least one data packet not successfully decoded by the terminal device; and means for transmitting, based on the request, to the terminal device, the at least one data packet.

8. The tethering device according to any of claims 1 to 7, further comprising: means for receiving, from the terminal device, information on link quality between the access node and the terminal device; and means for transmitting, to the access node, link quality information comprising: a combination of information on link quality between the access node and the tethering device and the information on the link quality between the access node and the terminal device, or the information on the link quality between the access node and the terminal device.

9. The tethering device according to claim 8, wherein the information on the link quality between the access node and the terminal device comprises at least one of the following: data packet retransmission feedback information of the terminal device, channel state information of the terminal device indicative of a state of the radio channel between the access node and the terminal device, or reference signal received power at the terminal device.

10. The tethering device according to claim 9, further comprising: means for combining the channel state information of the terminal device with channel state information of the tethering device indicative of a state of a radio channel between the access node and the tethering device; ormeans for combining the data packet retransmission feedback information of the terminal device with data packet retransmission feedback information of the tethering device based on transmitting, to the access node, a retransmission request for data packets not successfully decoded by both the terminal device and the tethering device and not transmitting a retransmission request for data packets successfully decoded by either the terminal device or the tethering device.

11. The tethering device according to claim 10, further comprising: means for combining the channel state information of the terminal device with the channel state information of the tethering device based on selecting channel state information that is indicative of weakest or strongest radio channel conditions among the channel state information of the terminal device and the channel state information of the tethering device.

12. A terminal device, comprising: means for transmitting, to a tethering device, a request for the terminal device to operate as a listener to data traffic transmitted by an access node of a communication network to the tethering device; means for receiving, from the tethering device, signalling information configured to enable reception of the data traffic by the terminal device over a radio channel between the access node and the terminal device; and means for receiving the data traffic from the access node over the radio channel between the access node and the terminal device based on the signalling information.

13. The terminal device according to claim 12, further comprising: means for establishing a secure connection with the tethering device; and means for receiving the signalling information from the tethering device via the secure connection.

14. The terminal device according to claim 12 or 13, wherein the request for the terminal device to operate as a listener to the data traffic comprises a request for the terminal device to enter a passive listening mode, the terminal device further comprising: means for receiving, from the tethering device, an indication of successful switch of the terminal device to the passive listening mode; andmeans for initiating the reception of the data traffic from the access node over the radio channel between the access node and the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode.

15. The terminal device according to claim 14, further comprising: means for powering down uplink transmission circuitry of the terminal device, in response to or based on receiving the indication of the successful switch of the terminal device to the passive listening mode, wherein the uplink transmission circuitry is meant for uplink transmission directly towards the access node.

16. The terminal device according to any of claims 12 to 15, wherein the signalling information comprises at least one of the following: at least one identifier of the tethering device, at least one security key configured to enable decryption of the data traffic by the terminal device, or a subset of information elements configured at the tethering device for establishing a connection between the tethering device and the access node.

17. The terminal device according to claim 16, wherein the at least one identifier of the tethering device comprises a cell radio network temporary identifier.

18. The terminal device according to claim 16 or 17, further comprising: means for detecting the data traffic from a signal transmitted by the access node using the at least one identifier of the tethering device, and / or means for decrypting the data traffic based on the at least one security key.

19. The terminal device according to any of claims 12 to 18, wherein the data traffic comprises a plurality of data packets, the terminal device further comprising: means for receiving, from the tethering device, at least one data packet of the data traffic; means for combining data of the at least one data packet received from the tethering device with data of at least one data packet not successfully decoded by the terminal device from a direct radio connection to the access node.

20. The terminal device according to claim 19, further comprising: means for transmitting, to the tethering device, a request for the at least one data packet of the data traffic not successfully decoded by the terminal device.

21. The terminal device according to any of claims 12 to 20, wherein the data traffic comprises extended reality data, and / or wherein the terminal device comprises a head-mountable device comprising means for rendering the extended reality data.

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