Switching between transmission modes

Abstract

A solution for switching between transmission modes is disclosed. An apparatus comprises a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to: receive (300) from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; begin (302) operating in one of the at least two radio link control modes; obtain (304) information on a condition for switching between the at least two radio link control modes and switch (304) to a further radio link control mode from the at least two radio link control modes.

Description

[0001] SWITCHING BETWEEN TRANSMISSION MODES

[0002] Field

[0003] The exemplary and non-limiting embodiments of the invention relate generally to apparatuses and methods in wireless communication networks.

[0004] Background

[0005] Wireless telecommunication systems are under constant development. There is a constant need for higher data rates and high quality of service. In wireless connections errors are bound to happen and retransmissions are needed. How to handle those errors while keeping the data rate experienced by users high is an important topic.

[0006] Summary

[0007] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key / critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later.

[0008] According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising: a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to: receive from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

[0009] According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising: a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to: transmit to a terminal device a configuration including at least two radio link control modes of operation for the terminal device and the apparatus; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

[0010] According to an aspect of the present invention, there is provided a method in an apparatus in a communication system comprising the steps of: receive from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

[0011] According to an aspect of the present invention, there is provided a method in an apparatus in a communication system comprising the steps of: transmit to a terminal device configuration including at least two radio link control modes of operation for the terminal device and the apparatus; begin operating in one of the at least two radio link control modes; obtain information on a one condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

[0012] According to an aspect of the present invention, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform at least the following: controlling reception from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; beginning operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switching to a further radio link control mode from the at least two radio link control modes.

[0013] According to an aspect of the present invention, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform at least the following: controlling transmission to a terminal device configuration including at least two radio link control modes of operation for the terminal device and the apparatus; beginning operating in one of the at least two radio link control modes; obtaining information on a condition for switching between the at least two radio link control modes; switching to a further radio link control mode from the at least two radio link control modes.

[0014] In an embodiment, there is provided there is provided an apparatus in a communication system, comprising means for receiving from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; means for beginning operating in one of the at least two radio link control modes; means for obtaining information on a condition for switching between the at least two radio link control modes and means for switching to a further radio link control mode from the at least two radio link control modes. In an embodiment, there is provided an apparatus in a communication system, comprising means for transmitting to a terminal device a configuration including at least two radio link control modes of operation for the terminal device and the apparatus; means for beginning operating in one of the at least two radio link control modes; means for obtaining information on a condition for switching between the at least two radio link control modes and means for switching to a further radio link control mode from the at least two radio link control modes.

[0015] One or more examples of implementations are set forth in more detail in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. The embodiments and / or examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0016] List of drawings

[0017] Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

[0018] Figures 1 and 2 illustrate examples of simplified system architecture of a communication system;

[0019] Figures 3A, 3B and 4 are flowcharts illustrating some embodiments;

[0020] Figure 5 is a signalling chart illustrating an example of an embodiment; and

[0021] Figures 6A, 6B and 6C illustrate simplified examples of apparatuses applying some embodiments.

[0022] Description of some embodiments

[0023] Fig. 1 shows devices 100 and 102. The devices 100 and 102 may, for example, be user devices or user terminals. The devices 100 and 102 are configured to be in a wireless connection on one or more communication channels with a node 104. The node 104 is further connected to a core network 106. In one example, the node 104 may be an access node, such as (eZg)NodeB, serving devices in a cell. In one example, the node 104 may be a non-3GPP access node. The physical link from a device to a (e / g)NodeB is called uplink or reverse link and the physical link from the (eZg)NodeB to the device is called downlink or forward link. It should be appreciated that (eZg)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage. A communications system typically comprises more than one (eZg)NodeB in which case the (eZg)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signalling purposes. The (eZg)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (eZg)NodeB includes or is coupled to transceivers. From the transceivers of the (eZg)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (eZg)NodeB is further connected to the core network 106 (CN or next generation core NGC).

[0024] The device (also called a subscriber unit, user device, user equipment (UE), user terminal, terminal device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station.

[0025] The device typically refers to a device ( e.g. a portable or non-portable computing device) that includes wireless mobile communication devices operating with or without an universal subscriber identification module (USIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop andZor touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction, e.g. to be used in smart power grids and connected vehicles. The device may also utilise cloud. In some applications, a device may comprise a user portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud. The device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities.

[0026] Various techniques described herein may also be applied to a cyberphysical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected information and communications technology, ICT, devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyberphysical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0027] Additionally, although the apparatuses have been depicted as single entities, different units, processors and / or memory units (not all shown in Fig. 1 ) may be implemented.

[0028] 5G or NR (New Radio) enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the Long Term Evolution, LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and / or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, extended or augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, e.g. below 6GHz or above 24 GHz, cm Wave and mmWave, and also being integrable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, 6 or above 24 GHz - cmWave and mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0029] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0030] The communication system is also able to communicate with other networks 112, such as a public switched telephone network, or a VoIP network, or the Internet, or a private network, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Fig. 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0031] The technology of Edge cloud may be brought into a radio access network (RAN) by utilizing network function virtualization (NFV) and software defined networking (SDN). Using the technology of edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at or close to a remote antenna site (in a distributed unit, DU 108) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 110).

[0032] It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

[0033] 5G may also utilize satellite communication 116 to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway / maritime / aeronautical communications. Satellite communication may utilise geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on- ground cells may be created through an on-ground relay node or by a gNB located on-ground or in a satellite.

[0034] It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (eZg)NodeBs, the device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (eZg)NodeBs or may be a Home(eZg)NodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (eZg)NodeBs of Fig. 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (eZg)NodeBs are required to provide such a network structure.

[0035] For fulfilling the need for improving the deployment and performance of communication systems, the concept of “plug-and-play” (eZg)NodeBs has been introduced. Typically, a network which is able to use “plug-and-play” (eZg)Node Bs, includes, in addition to Home (eZg)NodeBs (H(eZg)NodeBs), a home node B gateway, or HNB-GW (not shown in Fig. 1 ). A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNBs back to a core network.

[0036] Fig.2 illustrates an example of a communication system based on 5G network components. A terminal device or user equipment 100 communicating via a 5G network 202 with a data network 112. The user terminal 100 is connected to a Radio Access Network RAN node, such as (eZg)NodeB 206 which provides the user terminal a connection to the network 112 via one or more User Plane Functions 208. The user terminal 100 is further connected to Core Access and Mobility Management Function, AMF 210, which is a control plane core connector for (radio) access network and can be seen from this perspective as the 5G version of Mobility Management Entity, MME, in LTE. The 5G network further comprises Session Management Function, SMF 212, which is responsible for subscriber sessions, such as session establishment, modify and release, and a Policy Control Function 214 which is configured to govern network behavior by providing policy rules to control plane functions.

[0037] 6G networks are expected to adopt flexible decentralized and / or distributed computing systems and architecture and ubiquitous computing, with local spectrum licensing, spectrum sharing, infrastructure sharing, and intelligent automated management underpinned by mobile edge computing, artificial intelligence, short-packet communication, distributed ledgers and blockchain technologies. Key features of 6G will include intelligent connected management and control functions, programmability, integrated sensing and communication, reduction of energy footprint, trustworthy infrastructure, scalability and affordability. In addition to these, 6G is also targeting new use cases covering the integration of localization and sensing capabilities into system definition to unifying user experience across physical and digital worlds.

[0038] Extended Reality (XR) technology is one of the applications that has been under active study in mobile communications. The term XR covers different applications such as augmented reality (AR), virtual reality (VR) and mixed reality (MR), for example. In XR, the user may be presented an extended view of his / her surroundings, where visual and / or audible features are added on top. Also, the user may be virtually taken to another place, for example. The number of applications and possibilities to utilise XR is constantly increasing.

[0039] XR applications typically utilise a lot of bandwidth and are characterized by high data rate requirements and relatively small packet delay budget (PDB). As XR services are extremely capacity hungry, they typically need to operate at a block error rate (BLER) target at first transmission around 10’1and rely on hybrid automatic repeat request (HARQ) retransmissions to achieve a high spectral efficiency while fulfilling the application’s packet delay budget.

[0040] However, due to link adaptation inaccuracies, HARQ failures may still occur, for instance, after one or two HARQ retransmissions. This typically triggers a Radio Link Control Automatic Repeat Request (RLC ARQ) retransmission, which allows the selection of a more appropriate modulation and coding scheme (MCS) that better fits the signal to interference and noise ratio (SINR) conditions experienced at the receiver.

[0041] However, RLC ARQ retransmissions are triggered in the transmitter by status reports received from the receiver. This may cause delays which causes problems in view of the low packet delay budget of XR applications.

[0042] One possibility for tackle this problem in case of HARQ failure is to use fast retransmissions (within packet delay budget) of RLC Service Data Units (SDUs) and / or RLC SDUs segments. This may be possible by triggering retransmissions of “failed” RLC SDUs and / or RLC SDU segments at the transmitter side based on information received from medium access control (MAC) layer, for example in case a transmission block (TB) reaches the maximum number of HARQ retransmissions without being correctly received. However, the drawback is that this requires complex interactions between MAC and RLC in transmitting device to keep track of which RLC SDUs and / or RLC SDU segments are included in specific transport blocks. Also, the MAC at the transmitter side may not always be aware of the need for retransmissions - this may be the case if a negative acknowledgement feedback error occurs, where the receiver sends a NACK while it is detected as an ACK at the transmitter-side.

[0043] One suggested remedy is to use so-called blind retransmissions of RLC PDUs, where retransmissions are sent without any indication from the receiver. This solution of blind retransmission mechanism utilises on the combination of a retransmission timer, a separate retransmission queue, and MAC requesting a new transport block while the timer is running.

[0044] When an RLC SDU or SDU segment is for the first time included in a transmission block to be transmitted towards the gNB, the RLC SDU or SDU segment is also put in a retransmission queue. When MAC asks for another PDU from that same RLC entity, RLC first provides RLC SDUs and / or SDU segments from the retransmission queue and for which a retransmission timer is running. In other words, the RLC retransmissions are not triggered by a status report received at RLC, but by the MAC sublayer requesting a new PDU from RLC while the retransmission timer is running, i.e. after the retransmission timer is started and before it expires.

[0045] There are different alternatives when to start the retransmission timer (i.e., for when the retransmission queue becomes “active”):

[0046] In an option, the retransmission timer is started as soon as an RLC SDU or RLC SDU segment is put in the retransmission queue, i.e., when it is for the first time included in a PDU that is sent to MAC.

[0047] In another option, the start of the retransmission timer is delayed by using an additional delay timer. The delay timer is started when an RLC SDU or RLC SDU segment is for the first time included in a PDU that is sent to MAC, but the actual retransmission timer is started when the delay timer expires.

[0048] In yet another option, the retransmission timer is started for RLC SDUs and / or RLC SDU segments in the retransmission queue when the corresponding RLC transmission buffers are empty. In this case, new data arrival in the RLC transmission buffer may cause flushing of the retransmission buffer.

[0049] The purpose of this solution is to enable blind retransmissions of RLC SDUs and SDU segments in the same order as they were first transmitted and only if the retransmission queue is active (and it becomes active once there is nothing else left to transmit).

[0050] However, the suggested use of blind transmissions may trigger unnecessary retransmission of RLC data, which in turn may cause unnecessary delays, a decrease in the capacity, or introduce unnecessary interference.

[0051] In an embodiment of the present solution, the unnecessary retransmissions may be avoided by introducing more than one RLC mode which can be applied regarding RLC retransmissions. The modes may be changed based on the current need. For example, a mode based on blind retransmissions may only be entered when necessary.

[0052] A mode based on blind retransmissions may be denoted as enhanced acknowledged mode and a mode without blind retransmissions may be denoted as acknowledged mode or legacy mode.

[0053] The flowchart of Fig. 3A illustrates an embodiment. The flowchart illustrates an example of an embodiment applied at a network element apparatus. In an embodiment, the apparatus may be a terminal device or user equipment or a part of a terminal device or user equipment.

[0054] In step 300, the apparatus is configured to receive from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element.

[0055] In an embodiment, the configuration further includes at least one condition for switching between the at least two radio link control modes. The at least one condition may also be previously transmitted or included in specifications, for example. In an embodiment, the criteria may be specified in specifications, and the threshold used may be included in the configuration.

[0056] In step 302, the apparatus is configured to begin operating in one of the at least two radio link control modes;

[0057] In step 304, the apparatus is configured to obtain information on a condition from the at least one condition for switching between the at least two radio link control modes;

[0058] In step 306, the apparatus is configured to switch to a further radio link control mode from the at least two radio link control modes. In an embodiment, the configuration comprises the radio link control mode with which begin operating.

[0059] In an embodiment, the apparatus may detect the condition, or receive it in a message from a network element.

[0060] In an embodiment, the apparatus is configured to, after detecting the predetermined condition, transmit a message to the network element indicating that the apparatus switches to a further radio link control mode.

[0061] In an embodiment, the at least two radio link control modes are acknowledged mode and enhanced acknowledged mode. In an embodiment, the at least two radio link control modes are any of an RLC acknowledged mode and an RLC unacknowledged mode, and any of an enhanced RLC acknowledged mode, an enhanced RLC unacknowledged mode and an RLC unacknowledged mode, unacknowledged mode and enhanced unacknowledged mode.

[0062] In an embodiment, the at least one condition depends on the currently used radio link control mode. Thus, for example, a given condition of the at least one condition may be used when the apparatus operates in acknowledged mode, and another given condition of the at least one condition may be used when the apparatus operates in enhanced acknowledged mode.

[0063] The flowchart of Fig. 3B illustrates an embodiment. The flowchart illustrates an example of an embodiment applied at a network element apparatus. In an embodiment, the apparatus may be a gNB or a part of a gNB.

[0064] In step 310, the apparatus is configured to transmit to a terminal device configuration including at least two radio link control modes of operation for the terminal device and the apparatus.

[0065] In step 312, the apparatus is configured to begin operating in one of the at least two radio link control modes.

[0066] In step 314, the apparatus is configured to obtain information on at least one condition.

[0067] In step 316, the apparatus is configured to switch to a further radio link control mode from the at least two radio link control modes.

[0068] In an embodiment, the apparatus is configured to transmit, for example in the configuration, to a terminal device the radio link control mode with which to begin operating.

[0069] In an embodiment, the configuration further includes at least one condition for switching between the at least two radio link control modes. The at least one condition may also be previously transmitted or included in specifications, for example. In an embodiment, the apparatus is configured to receive from the terminal device a message to the network element indicating that the terminal device switches to a further radio link control mode. The apparatus may be configured to switch, based on the message, to communicating with the terminal device in further radio link control mode.

[0070] In an embodiment, the apparatus is configured to detect a predetermined condition to switch between the radio link control modes and switch to communicating with the terminal device in another radio link control mode. The apparatus may also transmit a message to the terminal device indicating that the terminal device should switch to further radio link control mode.

[0071] It may be noted that the proposed solution of applying different radio control modes is not limited to ARQ retransmissions, but it may be used in connection with other procedures as well.

[0072] The flowchart of Fig. 4 illustrates an embodiment. The flowchart illustrates an example of an embodiment applied at a terminal device. The terminal device has a configuration including in this example two radio link control modes of operation for the apparatus, the configuration further including at least two conditions for switching between the two radio link control modes.

[0073] In the beginning 400, the terminal device operates in a given radio link control mode, named here as Mode A.

[0074] The operation on Mode A continues, until the terminal device detects 402 a condition A from the at least one condition for switching between the two radio link control modes.

[0075] In such a case, the terminal device switches 404 to operate in another radio link control mode, named here as Mode B.

[0076] The operation on Mode B continues, until the terminal device detects 406 a condition B from the at least one conditions for switching between the two radio link control modes.

[0077] In such a case, the terminal device switches 408 to operate in the radio link control mode A.

[0078] The operation on Mode A continues, until the terminal device detects 402 a condition A from the at least one condition for switching between the two radio link control modes.

[0079] Thus, the terminal device may alternatively operate on either on Mode A or Mode B depending on conditions.

[0080] In an example, the Mode A may be a mode without blind retransmissions (acknowledged mode or legacy mode) and the Mode B may be based on blind retransmissions (enhanced acknowledged mode). In following, embodiments with two RLC modes are discussed in connection with automatic repeat request procedure. However, as one skilled in the art understands, the proposed solution may be used also in connection with other procedures and with more than two RLC modes.

[0081] In an embodiment, a terminal device may be configured with (for example) two RLC modes, a legacy mode without blind retransmissions and a mode that is implementing blind retransmission of RLC PDUs to handle retransmissions within a small packet delay budget.

[0082] In an embodiment, the mode with blind retransmission is only activated upon the determination of certain conditions at MAC. An example of such a condition might be when MAC reaches the maximum number of HARQ retransmissions without being able to transmit a transport block with correct reception at the receiver side, for example.

[0083] In a similar manner, the RLC mode may return to “legacy” upon determination of given conditions, which may be different conditions than above. An example of such a condition might be that MAC has operated for a time window without reaching the maximum number of HARQ retransmissions.

[0084] In an embodiment, a terminal device may receive from a network element an RLC configuration consisting of at least two RLC modes. A first mode (Mode A) may be RLC acknowledged mode (or unacknowledged mode) without blind RLC retransmissions, i.e., legacy mode. A second mode (Mode B) may be RLC acknowledged mode (or unacknowledged mode) with blind RLC retransmissions.

[0085] In an embodiment, the first mode is any of an RLC acknowledged mode and an RLC unacknowledged mode, and the second mode is any of an enhanced RLC acknowledged mode, an enhanced RLC unacknowledged mode and an RLC unacknowledged mode.

[0086] In an embodiment, the RLC configuration may also include the mode with which to start (e.g., Mode A or Mode B), and conditions and / or parameters such as thresholds for the terminal device to determine switching between the indicated RLC modes.

[0087] After receiving configuration, the terminal device starts operating with the initial mode configured in configuration. Upon detection at the terminal device that a condition indicated in the configuration is met, at least one of the following is performed:

[0088] - MAC indicates to RLC that a condition is met,

[0089] - RLC switches operation mode (from A to B, or vice versa), and - The terminal device indicates to the gNB that a condition is met and / or that the terminal device has switched RLC operation mode (from A to B, or vice versa).

[0090] Upon detection that a condition is met at the gNB, or upon receiving an indication from the terminal device that that a condition is met and that the terminal device has switched RLC operation mode (from A to B, or vice versa), at least one of the following is performed at the gNB:

[0091] - MAC indicates to RLC that that a condition is met,

[0092] - RLC switches operation mode (from A to B, or vice versa).

[0093] Fig. 5 is a signalling chart illustrating an embodiment. The chart illustrates an example of an embodiment applied at a network element such as a gNB 206 and a terminal device 100.

[0094] The gNB signals 500 uplink RLC configuration to the terminal device. The configuration comprises at least two RLC modes (e.g., Mode A and Mode B) and an initial mode with which the terminal device is to start. In this example Mode A may be the acknowledged mode and Mode B the enhanced acknowledged mode with retransmissions. The configuration may further comprise conditions for switching between the at least two RLC modes. In an embodiment, for switching from Mode A to Mode B, condition A is to be detected and for switching from Mode B to Mode A, condition B is to be detected. Examples of conditions are described below.

[0095] In 502, the terminal device and the gNB start operating RLC in initial mode. In this example, Mode A is the initial mode, which corresponds to legacy mode without blind retransmissions.

[0096] When operating in Mode A, the RLC receiver entity at the gNB sends RLC status PDUs 504 based on legacy operation.

[0097] Further, when operating in Mode A, the RLC transmitter entity at the terminal device retransmits 506 RLC SDUs and RLC SDU segments based on the RLC status PDUs it received from the gNB.

[0098] In 508, MAC at the terminal device detects that conditions to switch from Mode A to Mode B (enhanced acknowledged mode with blind retransmissions) are met. This could be one of the following:

[0099] - the average block error rate of first transmissions of transport blocks measured over a given first time window or a consecutive number of first transmissions of transport blocks is larger than a given first threshold value;

[0100] - the number of hybrid automatic repeat request HARQ retransmissions for at least one Transport Block / HARQ process reaches a given first value; - a radio link control Service Data Unit or a Service Data Unit segment that has been previously included in a Transport Block stays in the retransmission buffer for longer than a given first timer without being retransmitted or flushed.

[0101] In an embodiment, the terminal device transmits 510 to the gNB information that a condition has been met, so that gNB can also switch mode. This step is optional, as MAC at the gNB may also be able to detect that the conditions to switch from Mode A to Mode B are met, and hence RLC mode can synchronously switch from Mode A to Mode B without need for explicit signaling from the transmitter side (terminal device) to the receiver side (gNB). However, to handle potential errors, RLC mode switch indication from the terminal device to the gNB could be supported in any case. The indication could be conveyed using RRC, MAC or physical layer signaling, or could also be signaled using a special RLC control PDU.

[0102] In 512, the terminal device and gNB start operating RLC in Mode B with retransmissions.

[0103] In 514, the RLC transmitter entity in the terminal device starts blind retransmissions of RLC SDUs and / or RLC SDU segments. Here any known solution may be utilised. Since the terminal device is blindly retransmitting SDUs, the RLC receiver entity in the gNB may stop transmitting RLC status PDUs requesting retransmissions of RLC SDUs and / or RLC SDU segments. Such a behaviour may be configured by RRC and accompanied by a switch from a push window to a pull window at RLC (so that losses do not stall the window).

[0104] In an embodiment, when operating in Mode B (with blind retransmissions), the RLC receiver entity at the gNB may optionally still send 514 RLC status PDUs.

[0105] In 518, MAC in the terminal device detects that conditions to switch from Mode B to Mode A are met. This could be one of the following:

[0106] - the average block error rate of first transmissions of transport blocks measured over a given second time window or a consecutive number of first transmissions of transport blocks is smaller than a given second threshold value;

[0107] - a given second timer expires, where the second timer is started when RLC switches from the first mode to the second mode and is restarted when, for at least one TB / HARQ process, the number of HARQ retransmissions reaches a given second value. Such given second value could be different or the same as the given first value used in 508 when detecting the conditions to switch from Mode A to Mode B;

[0108] - after a given number of consecutive transport blocks are successfully transmitted within a given number of HARQ retransmissions. In an embodiment, the terminal device transmits 520 to the gNB information that a condition has been met, so that gNB can also switch mode. This step is optional, as MAC at the gNB can also detect that the conditions to switch from Mode B to Mode A are met, as above with the Mode A to Mode B change.

[0109] From now on, the operation is steps 522 to 526 continues in a similar manner as in steps 506 to 506 described above.

[0110] It may be noted, that the parameters mentioned above (a given first time window, a given first threshold value, a given first value, a given first timer, a given second time window, a given second threshold value, a given second timer, a given second value, a given number, for example) are just examples of the possible parameters configured to the terminal device to determine the switching between RLC modes. The gNB may also transmit other suitable parameters to the terminal device in the configuration information 500.

[0111] One of the advantages of the proposed solution as compared to prior art is that blind RLC retransmissions are only activated when certain conditions are met at MAC, which reduces the potential drawback of prior art schemes when RLC retransmissions are not needed.

[0112] In the above embodiments, the transmitter detects the condition for switching between modes at the MAC layer. However, other alternatives may also be based on the RLC or Packet Data Convergence Protocol (PDCP) layer at the receiver side detecting for instance sequence number (SN) gaps in the received sequence of PDUs and requesting the transmitter to switch modes.

[0113] In an embodiment, Mode A is legacy RLC unacknowledged mode. In such a case, the receiver entity at the gNB does not need to send RLC status PDUs when operating in Mode A. Synchronized operation between transmitter and receiver side may be less important to achieve in this option.

[0114] Above, embodiments have been described in the uplink direction. However, embodiments may be used as well in the downlink direction, from gNB to a terminal device, as one skilled in the art understands. In the downlink direction, the gNB is the transmitter and the terminal device the receiver. Thus, their roles are reversed with regard to the above-described embodiments.

[0115] Figs. 6A, 6B and 6C and illustrate embodiments. The figures illustrate simplified examples of apparatuses applying embodiments of the invention. It should be understood that the apparatuses are depicted herein as examples illustrating some embodiments. It is apparent to a person skilled in the art that the apparatuses may also comprise other functions and / or structures and not all described functions and structures are required. Although the apparatuses have been depicted as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[0116] Fig. 6A illustrates an example of an apparatus which may be a base station, gNB 206 or a part of base station or a gNB.

[0117] The apparatus 206 of the example includes a control circuitry 600 configured to control at least part of the operation of the apparatus.

[0118] The apparatus may comprise a memory 602 for storing data. Furthermore, the memory may store software 604 executable by the control circuitry 600. The memory may be integrated in the control circuitry.

[0119] The apparatus may comprise one or more interface circuitries 606. The interface circuitries are operationally connected to the control circuitry 600. An interface circuitry 606 may be a set of transceivers configured to communicate wirelessly with terminal devices or user equipment of a wireless communication network. The interface circuitry may be connected to an antenna arrangement (not shown). The apparatus may also comprise a connection to a transmitter instead of a transceiver. The apparatus may further comprise an interface 608 configured to communicate with other network elements such a core network or other corresponding apparatuses, or for example a user interface.

[0120] In an embodiment, the software 604 may comprise a computer program comprising program code means adapted to cause the control circuitry 600 of the apparatus to realise at least some of the embodiments described above.

[0121] In an embodiment, as shown in Fig. 6B, at least some of the functionalities of the apparatus of Fig. 6A may be shared between two physically separate devices, forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separated devices for executing at least some of the described processes. Thus, the apparatus of Fig. 6B, utilizing such shared architecture, may comprise a remote control unit RCU 610, such as a host computer or a server computer, operatively coupled (e.g. via a wireless or wired network) to a remote distributed unit RDU 612 located in the (e / g)NodeB. In an embodiment, at least some of the described processes may be performed by the RCU 610. In an embodiment, the execution of at least some of the described processes may be shared among the RDU 612 and the RCU 610.

[0122] In an embodiment, the RCU 610 may generate a virtual network through which the RCU 610 communicates with the RDU 612. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization may involve platform virtualization, often combined with resource virtualization. Network virtualization may be categorized as external virtual networking which combines many networks, or parts of networks, into the server computer or the host computer (e.g. to the RCU). External network virtualization is targeted to optimized network sharing. Another category is internal virtual networking which provides network-like functionality to the software containers on a single system. Virtual networking may also be used for testing the terminal device.

[0123] In an embodiment, the virtual network may provide flexible distribution of operations between the RDU and the RCU. In practice, any digital signal processing task may be performed in either the RDU or the RCU and the boundary where the responsibility is shifted between the RDU and the RCU may be selected according to implementation.

[0124] Fig. 6C illustrates an example of an apparatus which may be a terminal device 100, user equipment or a part of terminal device or user equipment.

[0125] The apparatus 100 of the example includes a control circuitry 630 configured to control at least part of the operation of the apparatus.

[0126] The apparatus may comprise a memory 632 for storing data. Furthermore, the memory may store software 634 executable by the control circuitry 630. The memory may be integrated in the control circuitry.

[0127] The apparatus may comprise one or more interface circuitries 636. The interface circuitries are operationally connected to the control circuitry 630. An interface circuitry 636 may be a set of transceivers configured to communicate wirelessly with network elements, base stations, gNBs or other terminal devices of a wireless communication network. The interface circuitry may be connected to an antenna arrangement (not shown). The apparatus may also comprise a user interface 638.

[0128] In an embodiment, the software 634 may comprise a computer program comprising program code means adapted to cause the control circuitry 630 of the apparatus to realise at least some of the embodiments described above.

[0129] The steps and related functions described in the above and attached figures are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps or within the steps. Some of the steps can also be left out or replaced with a corresponding step.

[0130] The apparatuses or controllers able to perform the above-described steps may be implemented as an electronic digital computer, processing system or a circuitry which may comprise a working memory (random access memory, RAM), a central processing unit (CPU), and a system clock. The CPU may comprise a set of registers, an arithmetic logic unit, and a controller. The processing system, controller or the circuitry is controlled by a sequence of program instructions transferred to the CPU from the RAM. The controller may contain a number of microinstructions for basic operations. The implementation of microinstructions may vary depending on the CPU design. The program instructions may be coded by a programming language, which may be a high-level programming language, such as C, Java, etc., or a low-level programming language, such as a machine language, or an assembler. The electronic digital computer may also have an operating system, which may provide system services to a computer program written with the program instructions.

[0131] As used in this application, the term ‘circuitry’ refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of circuits and software (and / or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s) / software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

[0132] This definition of ‘circuitry’ applies to all uses of this term in this application. As a further example, as used in this application, the term ‘circuitry’ would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and / or firmware. The term ‘circuitry’ would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

[0133] An embodiment provides a non-transitory computer program embodied on a distribution medium, comprising program instructions which, when loaded into an electronic apparatus, are configured to control the apparatus to execute the embodiments described above. 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).

[0134] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, and a software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst several computers.

[0135] The apparatus may also be implemented as one or more integrated circuits, such as application-specific integrated circuits ASIC. Other hardware embodiments are also feasible, such as a circuit built of separate logic components.

[0136] A hybrid of these different implementations is also feasible. When selecting the method of implementation, a person skilled in the art will consider the requirements set for the size and power consumption of the apparatus, the necessary processing capacity, production costs, and production volumes, for example. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

Claims1. An apparatus in a communication system, comprising: a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to: receive from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

2. The apparatus of claim 1 , the memory and the computer program code configured to, with the processor, cause the apparatus further to: receive from a network element the radio link control mode with which to begin operating and at least one condition for switching between the at least two radio link control modes.

3. The apparatus of claim 1 or 2, the memory and the computer program code configured to, with the processor, cause the apparatus further to: transmit a message to the network element indicating that the apparatus switches to further radio link control mode.

4. The apparatus of any preceding claim, wherein, if the current radio link mode is a first mode of the at least two radio link control modes, the at least one condition is one of- the average block error rate of first transmissions of transport blocks measured over a given first time window or a consecutive number of first transmissions of transport blocks is larger than a given first threshold value;- the number of hybrid automatic repeat request HARQ retransmissions for at least one Transport Block / HARQ process reaches a given first value;- a radio link control Service Data Unit or a Service Data Unit segment that has been previously included in a Transport Block stays in the retransmission buffer for longer than a given first timer without being retransmitted or flushed.

5. The apparatus of claim 4, wherein, if the current radio link mode is a second mode of the at least two radio link control modes, the at least one condition is one of- the average block error rate of first transmissions of transport blocks measured over a given second time window or a consecutive number of first transmissions of transport blocks is smaller than a given second threshold value;- a given second timer expires, where the second timer is started when RLC switches from the first mode to the second mode and is restarted when, for at least one TB / HARQ process, the number of HARQ retransmissions reaches the given first value or a given second value;- after a given number of consecutive transport blocks are successfully transmitted within a given number of HARQ retransmissions.

6. The apparatus of any preceding claim, wherein the at least one condition depends on the currently used radio link control mode.

7. The apparatus of any preceding claim, the memory and the computer program code configured to, with the processor, cause the apparatus further to: detect a condition for switching between the at least two radio link control modes.

8. The apparatus of any preceding claim, the memory and the computer program code configured to, with the processor, cause the apparatus further to: receive a message from a network element indicating that the apparatus should switch to further radio link control mode.

9. An apparatus in a communication system, comprising: a processor; and a memory including instructions, the instructions, when executed by the processor, cause the apparatus to: transmit to a terminal device a configuration including at least two radio link control modes of operation for the terminal device and the apparatus; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

10. The apparatus of claim 9, the memory and the computer program code configured to, with the processor, cause the apparatus further to:transmit to the terminal device at least one condition for switching between the at least two radio link control modes and the radio link control mode with which to begin operating.

11. The apparatus of claim 9 or 10, the memory and the computer program code configured to, with the processor, cause the apparatus further to: receive from the terminal device a message to the network element indicating that the terminal device switches to a further radio link control mode; switch, based on the message, to communicating with the terminal device in further radio link control mode.

12. The apparatus of claim 9 or 10, the memory and the computer program code configured to, with the processor, cause the apparatus further to: detect one of the at least one condition to switch between the radio link control modes; switch, based on the detection, to communicating with the terminal device in a further radio link control mode.

13. The apparatus of any preceding claim 12, the memory and the computer program code configured to, with the processor, cause the apparatus further to: transmit a message to the terminal device indicating that the terminal device should switch to further radio link control mode.

14. A method in an apparatus in a communication system comprising the steps of: receive from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; begin operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

15. The method of claim 14, further comprising: receive from a network element the radio link control mode with which to begin operating and at least one condition for switching between the at least two radio link control modes.

16. The method of any preceding claim 14 to 15, wherein, if the current radio link mode is a first mode of the at least two radio link control modes, the at least one condition is one of- the average block error rate of first transmissions of transport blocks measured over a given first time window or a consecutive number of first transmissions of transport blocks is larger than a given first threshold value;- the number of hybrid automatic repeat request HARQ retransmissions for at least one Transport Block / HARQ process reaches a given first value;- a radio link control Service Data Unit or a Service Data Unit segment that has been previously included in a Transport Block stays in the retransmission buffer for longer than a given first timer without being retransmitted or flushed.

17. The method of claim 15, wherein, if the current radio link mode is a second mode of the at least two radio link control modes, the at least one condition is one of- the average block error rate of first transmissions of transport blocks measured over a given second time window or a consecutive number of first transmissions of transport blocks is smaller than a given second threshold value;- a given second timer expires, where the second timer is started when RLC switches from the first mode to the second mode and is restarted when, for at least one TB / HARQ process, the number of HARQ retransmissions reaches the given first value or a given second value;- after a given number of consecutive transport blocks are successfully transmitted within a given number of HARQ retransmissions.

18. A method in an apparatus in a communication system, comprising: transmit to a terminal device configuration including at least two radio link control modes of operation for the terminal device and the apparatus; begin operating in one of the at least two radio link control modes; obtain information on a one condition for switching between the at least two radio link control modes; switch to a further radio link control mode from the at least two radio link control modes.

19. A computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform at least the following:controlling reception from a network element a configuration including at least two radio link control modes of operation for the apparatus and the network element; beginning operating in one of the at least two radio link control modes; obtain information on a condition for switching between the at least two radio link control modes; switching to a further radio link control mode from the at least two radio link control modes.

20. A computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform at least the following: controlling transmission to a terminal device configuration including at least two radio link control modes of operation for the terminal device and the apparatus; beginning operating in one of the at least two radio link control modes; obtaining information on a condition for switching between the at least two radio link control modes; switching to a further radio link control mode from the at least two radio link control modes.

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