WO2019141349A1

WO2019141349A1 - Communication system

Info

Publication number: WO2019141349A1
Application number: PCT/EP2018/051007
Authority: WO
Inventors: Vinh Van Phan; Ling Yu; Zexian Li; Peter Rost
Original assignee: Nokia Technologies Oy
Priority date: 2018-01-16
Filing date: 2018-01-16
Publication date: 2019-07-25

Abstract

The invention relates to a method comprising operating, by a first network element (804), in a first mode, in which, on successful completion of a radio-level procedure with a communication device (803), the first network element (804) sends an application-level message to a second network element (805) that maintains a service between the communication device (803)and the second network element (805).

Description

COMMUNICATION SYSTEM

Field of the Invention

[0001] This disclosure relates to methods and apparatuses, and in particular but not exclusively to a method and apparatus relating to maintaining a service provided to a communication device over a network.

Background

[0002] A communication system can be seen as a facility that enables communication between two or more devices such as user terminals, machine-like terminals, base stations and/or other nodes by providing carriers between the communication devices. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided include two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a wireless system at least a part of communications between at least two stations occurs over wireless interfaces. Examples of wireless systems include public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A local area wireless networking technology allowing devices to connect to a data network is known by the tradename Wi-Fi (or WiFi). Wi-Fi is often used synonymously with WLAN.

[0004] The wireless systems can be divided into cells, and are therefore often referred to as cellular systems. A user can access a communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (communication device) or user apparatus. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and/or receive communications on the carrier. [0005] A communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. An example of standardized communication system architectures is the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The LTE is being standardized by the 3rd Generation Partnership Project (3GPP). The LTE employs the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access. Further development of LTE is sometimes referred to as LTE Advanced (LTE-A). The various development stages of 3GPP specifications are referred to as releases. In this description 3GPP release versions are distinguished by acronym“Rel-nn”.

[0006] In addition to LTE evolution, 3GPP has initiated a study item targeting a new radio generation (5G) called new radio (NR). NR does not require backwards compatibility with LTE. Instead, it aims at tight interworking between the RAT (radio access technology) and LTE. An objective of a NR study item is to identify and develop technology components needed for new radio (NR) systems to use any spectrum band ranging at least up to 100 GHz. The aim may be to achieve a single technical framework addressing usage scenarios, requirements and deployment scenarios defined in, for example, TR 38.913. The new radio access technology may be forward compatible to allow specification in two separate phases (Phase I and Phase II).

Summary

According to a first aspect there is provided a method comprising: operating, by a first network element, in a first mode, in which, on successful completion of a radio-level procedure with a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element. The method may further comprise a first network element sending the application-level message to the second network element regardless of whether or not the first network element receives the application-level message from the communication device. The method may further comprise signalling to the communication device that the first network element is able to operate in the first mode.

The method may further comprise receiving from the communication device an indication that the communication device is operating in a second mode in which the communication device will not be sending the application-level message.

The method may further comprise transmitting to the communication device an instruction for the communication device to enter the second mode.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst operating in the first mode. Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element.

Said first mode may comprise, on failure of a radio-level procedure with a communication device, the network element does not send an application-level message to the second network element for maintaining a service between the communication device and the second network element unless the application-level message has been received from the communication device. According to a second aspect, there is provided a method comprising: operating, by a communication device, in a second mode, in which, on successful completion of a radio-level procedure with a first network element, a radio-level part of the communication device: abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

The method may further comprise receiving signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure with the communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

Operating the communication device in the second mode further may cause the radio- level part of the communication device to: send an acknowledgement to an application-level message received from an application-level part of the communication device.

The method may further comprise further comprise transmitting to the first network element an indication that the communication device will not be sending the application-level message.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode. Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element. The application level message may be a first type of message, and further comprising exiting from the first mode when no messages of the first type are transmitted by the communication device within a predetermined time period. The method may further comprise entering the second mode in response to a received instruction from the first network element.

The radio-level procedure may be a radio-level handshake procedure. According to a third aspect, there is provided an apparatus comprising means for operating, a first network element, in a first mode, in which, on successful completion of a radio-level procedure with a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element.

The apparatus may further comprise means for sending, by a first network element, the application-level message to the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

The apparatus may further comprise means for signalling to the communication device that the first network element is able to operate in the first mode.

The apparatus may further comprise means for receiving from the communication device an indication that the communication device is operating in a second mode in which the communication device will not be sending the application-level message.

The apparatus may further comprise means for transmitting to the communication device an instruction for the communication device to enter the second mode.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst operating in the first mode. Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted.

Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element. Said first mode may comprise, on failure of a radio-level procedure with a communication device, the network element does not send an application-level message to the second network element for maintaining a service between the communication device and the second network element unless the application-level message has been received from the communication device.

According to a fourth aspect, there is provided an apparatus comprising means for operating, a communication device, in a second mode, in which, on successful completion of a radio-level procedure with a first network element, a radio-level part of the communication device: abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

The apparatus may further comprise means for receiving signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure with the communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

Operating the communication device in the second mode further may cause the radio- level part of the communication device to: send an acknowledgement to an application-level message received from an application-level part of the communication device. The apparatus may further comprise means for transmitting to the first network element an indication that the communication device will not be sending the application-level message.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode. Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element.

The application level message may be a first type of message, and the apparatus may further comprise means for exiting from the first mode when no messages of the first type are transmitted by the communication device within a predetermined time period.

The apparatus may further comprise means for entering the second mode in response to an instruction received from the first network element.

The radio-level procedure may be a radio-level handshake procedure.

According to a fifth aspect, there is provided there is provided an apparatus comprising: at least one processor; and at least one memory comprising code that, when executed on the at least one processor, causes the at least one processor to perform the step of: operating, by a first network element, in a first mode, in which, on successful completion of a radio-level procedure with a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element.

The at least one processor may further perform the step of a first network element sending the application-level message to the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

The at least one processor may further perform the step of signalling to the communication device that the first network element is able to operate in the first mode.

The at least one processor may further perform the step of receiving from the communication device an indication that the communication device is operating in a second mode in which the communication device will not be sending the application- level message.

The at least one processor may further perform the step of transmitting to the communication device an instruction for the communication device to enter the second mode.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst operating in the first mode.

Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted.

According to a sixth aspect, there is provided there is provided an apparatus comprising: at least one processor; and at least one memory comprising code that, when executed on the at least one processor, causes the at least one processor to perform the step of: operating, by a communication device, in a second mode, in which, on successful completion of a radio-level procedure with a first network element, a radio-level part of the communication device: abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

The at least one processor may further perform the step of receiving signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure with the communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element regardless of whether or not the first network element receives the application-level message from the communication device. Operating the communication device in the second mode further may cause the radio- level part of the communication device to: send an acknowledgement to an application-level message received from an application-level part of the communication device. The at least one processor may further perform the step of transmitting to the first network element an indication that the communication device will not be sending the application-level message. Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode. Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element.

The application level message may be a first type of message, and the at least one processor may further perform the step exiting from the first mode when no messages of the first type are transmitted by the communication device within a predetermined time period.

The processor may perform the step of entering the second mode in response to an instruction received from the first network element.

The radio-level procedure may be a radio-level handshake procedure.

According to a seventh aspect, there is provided a computer program comprising computer code that, when executed on an apparatus, causes the apparatus to perform the step of: operating, by a first network element, in a first mode, in which, on successful completion of a radio-level procedure with a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element.

The apparatus may further perform the step of a first network element sending the application-level message to the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

The apparatus may further perform the step of signalling to the communication device that the first network element is able to operate in the first mode.

The apparatus may further perform the step of receiving from the communication device an indication that the communication device is operating in a second mode in which the communication device will not be sending the application-level message.

The apparatus may be further caused to send to the communication device and instruction to enter the second mode.

Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element.

Said first mode may comprise, on failure of a radio-level procedure with a communication device, the network element does not send an application-level message to the second network element for maintaining a service between the communication device and the second network element unless the application-level message has been received from the communication device.

According to an eighth aspect, there is provided a computer program comprising computer code that, when executed on an apparatus, causes the apparatus to perform the step of: operating, by a communication device, in a second mode, in which, on successful completion of a radio-level procedure with a first network element, a radio- level part of the communication device: abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

The apparatus may further perform the step of receiving signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure with the communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element regardless of whether or not the first network element receives the application-level message from the communication device. Operating the communication device in the second mode further may cause the radio- level part of the communication device to: send an acknowledgement to an application-level message received from an application-level part of the communication device. The apparatus may further perform the step of transmitting to the first network element an indication that the communication device will not be sending the application-level message.

Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode.

Said indication may be at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element. The application level message may be a first type of message, and the apparatus may further perform the step of exiting from the first mode when no messages of the first type are transmitted by the communication device within a predetermined time period.

The apparatus may be further caused to enter the second mode in response to an instruction received from the first network element.

The radio-level procedure may be a radio-level handshake procedure.

Figures

[0007] Some embodiments will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

[0008] Figure 1 shows a schematic example of a system where the invention may be implemented;

[0009] Figure 2 shows an example of a communication device;

[0010] Figure 3 illustrates protocol stacks of example devices;

[0011] Figures 4 and 5 illustrate a PROFIsafe architecture;

[0012] Figure 6 is a flow diagram for operations performed by an access point;

[0013] Figure 7 is a flow diagram for operations performed by a communication device;

[0014] Figures 8 to 10 illustrate potential message exchanges; and

[0015] Figure 11 illustrates protocol stacks of example devices.

Detailed description

[0016] In general, the following disclosure relates to mechanisms for saving network resources that are associated with transmitting data.

[0017] In particular, the following relates to a communication device that is configured to utilise a service provided by a network element (hereinafter called a service provider) over a network through an intermediary network element (such as a base station or other network node). The service between the communication device and the service provider is effectuated via application-level message exchange. For example, the service between the communication device and the service provider may be maintained via the transmission, from the communication device to the service provider, of periodic messages, such as“sign-of-life” or“heartbeat” messages or the like. The periodic messages may have a fixed size.

[0018] The intermediary network element is arranged to transfer such periodic messages from the communication device to the service provider. If a periodic message is not received by the service provider for longer than a threshold period of time, the service to the communication device is terminated.

[0019] Network resources may be saved in such a system by configuring the intermediary network element and the communication device to operate in respective (but complementary) modes in which, independently of receipt of the periodic messages from the communication device, the intermediary network element generates the periodic messages in the event that the radio-level connection between the intermediary network element and the communication device is still active. The intermediary network element may instruct the communication device to enter its complementary mode. The activity of the radio-level connection may be determined via, for example, a radio-level handshaking procedure between the communication device and the intermediary network element. From the activity of the radio-level connection, the intermediary network element is assured that the communication device is still able to communicate and receive the service. Thus accidental terminations and subsequent reestablishment procedures for the service are avoided. By skipping of the unnecessary periodic application level messages over reassured radio-level connection, network resources can be saved.

[0020] To complement these actions of the intermediary network element, the communication device may be configured to, when the intermediary network element is operating in the above-described mode, abstain from sending the periodic application-level messages to the intermediary network element. This may further save network resources between the communication device and the intermediary network element. The abstaining may be for a predetermined/threshold time duration to ensure that the communication device still wishes to subscribe to the service. The abstaining may be performed in response to receipt of an instruction from the intermediary network element to perform this abstaining.

[0021] The communication device may be further configured to, when the intermediary network element is operating in the above-described mode, generate the periodic messages at the application level and pass these periodic messages to the medium access control-level and/or radio-level for transmission to the first network element. The medium access control-level and/or radio-level may abstain from transmitting these periodic messages (as per the abstaining described above). To ensure that the application-level operations still work as expected, the medium access control-level and/or radio-level may generate (and send to the application-level) application-level acknowledgements for the periodic messages.

[0022] The above-described system has particular use in communications that require at least one of ultra-high reliability, ultra-high availability and ultra-low latency (such communications are collectively referred to as an“ultra-x” communication or ultra reliable low latency communications (URLLC). The following will thus discuss examples of the proposed system with reference to such ultra-x communication systems. However, it is understood that these discussed concepts are not limited to such ultra-x communication systems.

[0023] In the following, certain exemplifying embodiments are explained with reference to a wireless communication system serving devices adapted for wireless communication. Before explaining in detail embodiments, certain general principles of a communication system, a communication device and a control apparatus are briefly explained with reference to Figures 1 and 2 to assist in understanding the technology underlying the described invention.

[0024] In a wireless communication system 100, such as that shown in Figure 1 , wireless communication devices, for example, machine-type communications MTC devices 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving wireless infrastructure node or point. Such a node can be, for example, a base station or an eNodeB (eNB), or in a 5G system a Next Generation NodeB (gNB), or other wireless infrastructure node. These nodes will be generally referred to as base stations. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller. In Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as 5G or new radio, wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area.

[0025] In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 113 via gateway 112. A further gateway function may be provided to connect to another network.

[0026] The smaller base stations 116, 118 and 120 may also be connected to the network 113, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 116, 118 and 120 may be pico or femto level base stations or the like. In the example, stations 116 and 118 are connected via a gateway 111 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided.

[0027] A possible wireless communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as an endpoint device. An appropriate communication device may be provided by any device capable of sending and receiving radio signals.

[0028] A communication device may be for example a mobile device, that is, a device not fixed to a particular location, or it may be a stationary device. The communication device may need human interaction for communication, or may not need human interaction for communication.

[0029] The communication device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the wireless device.

[0030] A communication device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. Furthermore, a wireless communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories. The communication devices 102, 104, 105 may access the communication system based on various access techniques.

[0031] An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations of such systems are known as evolved or enhanced NodeBs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence/Radio Link Control/Medium Access Control/Physical layer protocol (PDCP/RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area.

[0032] Another example of a communications system is the 5G concept. Network architecture in 5G may be quite similar to that of the LTE-advanced. Changes to the network architecture may depend on the need to support various radio technologies and finer Quality of Service (QoS) support, and some on-demand requirements for e.g. QoS levels to support Quality of Experience (QoE) from a user point of view. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. 5G may use multiple input-multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[0033] The base stations/access points in 5G may be referred to as gNB.

[0034] The 5G system is planned to be introduced in the early 2020s, enabling expansion of International Mobile Telecommunications (IMT) that go beyond those of IMT-2000 and IMT-Advanced mobile broadband (MBB) service, and also enabling new services and use cases to be addressed. These new services are not only for human interaction, but also for a huge growth in machine-type communications (MTC) driven by, for example, factory automation and flexible process control. 5G ultra reliable and low-latency communications (URLLC) is one enabler to support these new services.

[0035] One requirement on URLLC currently being studied is how to ensure 99.999% reliability under the radio latency bound of 1 ms. Under this requirement, the maximum packet error probability must not be higher than 10⁵, where maximum allowable radio latency, including retransmissions is down to 1 ms.

[0036] While radio access is evolving through 3GPP, industrial networks are already using state-of-the-art ultra-reliable protocols and mechanisms, such as PROFIsafe, over existing communication networks.

[0037] PROFIsafe is a fail-safe communication protocol in production and process automation. PROFIsafe allows the delivery of updated and correct data (data integrity) to the intended destination (authenticity) just in time (timeliness). To do so, PROFIsafe includes several safety mechanisms, including the consecutive numbering of messages (sign-of-life), a time expectation for acknowledgement of messages (watch- dog), a codename between sender and receiver (F-Address) and data integrity checks (CRC = cyclic redundancy check). [0038] Using consecutive numbering, a receiver can determine whether or not it has received all of the messages completely and within the correct sequence. Using the watch-dog a receiver can determine whether a message has been received within a fault tolerance time, thus enabling the receiver to automatically initiate any necessary safety reactions on site, e.g. stoppage of movement. Using the F-Address a receiver can verify the authenticity and destination of a message. Finally, using the cyclic redundancy check (CRC) a receiver can determine whether a message is corrupted. More information about PROFIsafe can be found in“PROFIsafe System Description - Technology and Application”).

[0039] Figure 3 shows an example of conventional protocol stack of communication devices communicating over a communication link (e.g. radio link) using the PROFIsafe protocol. Each communication device includes an application layer (e.g. PROFIsafe layer), a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer and a physical (PFIY) layer. In this instance, one of the communication devices may be an access point/base station, whilst the other communication device may be a communication terminal accessing the network/a service via the access point/base station.

[0040] PROFIsafe may be used in Industrial Automation and Control (IAC) use cases. IAC use cases/systems may be associated with high risk processes, such as, for example, presses, saws, tooling machines, robots, conveying and packing systems, chemical processes, high pressure operations, off-shore technology, fire and gas sensing, burners, cable cars, etc. Therefore, services effected over communication links in conjunction with IAC systems need to be reassured using an ultra-x graded support.

[0041] It has been established that many IAC use cases require support for ultra-x communications for end-to-end communications. Flence, a corresponding serving radio access carrier or cell provided by a serving base station/access point of a serving network needs to be able to fulfil the supported ultra-x requirements to such a certain extent that a relevant communication device of an IAC system can be reassured that those ultra-x requirements are supported, and how. This should be signalled before the communication device initiates the service, or at least be obtained in a proactive manner. [0042] Such signalling allows for the communication device and associated IAC system of the communication device to determine whether to continue operating or not (i.e. if the service may be supported), and to adjust the communications operation mode properly for safety, efficiency and cost optimisations.

[0043] To enable and facilitate this in 5G networks, a so-called ultra-x graded carrier for a support of targeted IAC use cases has been proposed. The proposed ultra-x graded carrier, enforces frequent radio handshaking between a relevant communication device and a serving base station, as a part of radio connection monitoring configuration and control to ensure that the targeted key performance indicator (KPI) levels needed to fulfil the ultra-x requirements of the IAC system are being met.

[0044] Figures 4 and 5 illustrate two different aspects of IAC systems. The terminology used to refer to different elements in this system utilise language used in the PROFIsafe specifications.

[0045] Figure 4 illustrates a safety communication system architecture. The ultra-x communication requirement used in PROFIsafe for current IAC systems is referred to as the safety integrity level (SIL). An example SIL is SIL3, which is defined in PROFIsafe.

[0046] As depicted therein, Figure 4 shows an“F-host” 401 in communication with an Input/Output (I/O) Controller 402. The I/O Controller 402 is connected to a Decentralised Peripheral (DP)-Link 403 and a Remote I/O 404 over a PROFINET I/O link 405. The remote I/O comprises an I/O Device 406, an F-Device Input 407 and an F-Device Output 408. The DP-Link 403 is connected via PROFIBUS DP 409 to F- Devices 410, 411 and Process Automated (PA) Device 412. A PA Link 413 lies between the DP Link 403 and PA Device 412. An F Gateway 414 lies between the DP-Link 403 and F-Device 411.

[0047] Figure 5 illustrates safety functions and SIL3. As shown therein, an F-device 501 is comprised of multiple sensors 502. Each sensor 502 provides, via respective communication links 503, data to an F-Host 504, which performs logic operations thereon. In response to these logic operations, the F-Host 504 outputs instructions to an actuator 505, which performs an action associated with the IAC service.

[0048] To satisfy the ultra-x requirement of PROFIsafe, the communication links are allowed a mere 1 % contribution to the overall failure of the PROFIsafe system for transmission or communication connection on SIL3. (Sensors at the F-device may contribute to 35% of failure, logic operations at the F-host may contribute around 14% and actuators at the F-device may contribute approximately 50%). This means that the permissible probability of failures resulting from the communication links must not exceed 10-9/h in such a system to satisfy these requirements.

[0049] It is observed that there is a considerable portion of ultra-x graded data traffic in current applications of current IAC systems that is made of frequent periodic fixed small-size messages. For examples, each F-device of an IAC system needs to send a“sign-of-life” or“heart-beat” message as frequent as e.g. per 10ms to an F-host applying a“watch-dog” time interval for the IAC system during normal operation.

[0050] Thus, according to current specifications and assuming a watch-dog time interval of 30ms, an F-host send an acknowledgement to each alive F-device every 30ms from which the F-host receives at least one“sign-of-life” from individual F- devices within that watchdog time interval. The size of the sign-of-life messages (which may, e.g., comprise an F-device address, a packet sequence number and cyclic redundancy check (CRC) information) may be less than 20 octets.

[0051] Scheduling for a number of individual communication devices to transmit such frequent small packets in strict real time is rather resource consuming and inefficient for ultra-broadband radio access technologies because of an excessive protocol overhead. Scheduling is thus even more resource consuming when regardless of the additional requirements associated with ultra-x communications are considered. Therefore, the following, proposes a method to minimize radio resource consumption of a serving ultra-x graded carrier that may also simultaneously provide radio connections to individual F-devices having frequent small-packet traffic such as that used for automation safety in an associated IAC system.

[0052] It is also observed that the periodic, fixed small-size messaging service of the targeted applications (“sign-of-life” and“acknowledgement”) is more or less a frequent time-sensitive application-level handshaking. Flowever, as a proposed serving ultra-x graded carrier for 5G already enforces a frequent radio handshaking between a relevant communication device and a serving gNB for reassuring that the radio connection is up for the job of providing the required ultra-x service for the relevant communication device, the outcomes of a more frequent radio-level procedure, such as radio-level handshaking, may be utilized to provide for the radio communication needs of a less frequent application-level handshaking of the same communication device over the same radio connection. It should be noted that at least during normal operation which is expected to account for, e.g., 99.99% of the operating time of the targeted ultra-x graded IAC systems, the outcomes of the radio level handshaking and the application level handshaking should be the same or predictably in line with each other.

[0053] According to examples, a radio bearer is set up for individual communication devices as per the current operating radio network communication protocols. Then an implicit radio bearer mode (as described further below) is activated on the established radio bearer of a particular communication device for efficient support of the application. This process may be performed for a plurality of coexisting and collocating relevant communication devices, e.g., all F-devices of local IAC systems. In this mode, actual radio transmissions of certain application-level messages, e.g., frequent and small-size“sign-of-life” and/or“ack”, can be skipped; whilst other messages are transmitted as usual. In this regard, the implicit radio bearer service mode may be flexibly configured and controlled so as to be applied to certain frequent and small messages in any of the uplink and downlink directions, and not to other messages (including event based messages triggered by, e.g., once-off or some abnormal events on either application level or radio access level).

[0054] As an example, an IAC system of 100 F-devices is considered. Each F-Device is configured to send an ultra-x sensitive“sign-of-life” per 10ms to an F-host. Thus, there will be 10000 small-size ultra-x application messages to be sent in uplink per one second. If all, or even a portion, of those transmissions could be skipped from actual radio transmissions, considerable amount of radio resources could be saved.

[0055] The following thus proposes a mechanism in which a network element, such as an access point, may, on confirming that a radio-level connection is currently established and active between the network element and a communication device, independently generate application-level“keep-alive” messages (or other types of periodic messages) to send to a service provider currently providing a service to the communication device.

[0056] This mechanism is described with reference to the flow chart in Figure 6.

[0057] At 601 , the first network element (e.g. an access point) is configured to operate in a first mode. In the first mode, successful completion of a radio-level procedure between the first network element and a communication device may trigger the network element to send an application-level message to a second network element that maintains a service between the communication device and the second network element (e.g. a service provider). In the first mode, the first network element may be configured such that not every successfully completed radio-level procedure results in the application-level message being sent to the second network element.

[0058] The first mode may cause the first network element to send the application- level message to the second network element regardless of whether or not the first network element receives the application-level message from the communication device.

[0059] The first network element may be configured to signal to the communication device that the first network element is able to operate in the first mode. This may be performed in advance of entering the first mode.

[0060] The first network node may be configured to receive from the communication device an indication that the communication device will not be sending the application- level message. The first network node may be configured to abstain from entering the first mode until receipt of this indication from the communication device. The indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst operating in the first mode. The first network element may use the at least one parameter to set operating parameters of the first mode for communicating with the second network element. The indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application-level message for transmission to the second network element.

[0061] The first network node may be configured to transmit, to the communication device, an instruction to abstain from sending the application-level message. The above-mentioned indication may be received in response to this instruction. The indication may be explicit or implicit (such as being inferable through the subsequent operations of the communication device).

[0062] The first mode may further, on failure of a radio-level procedure with a communication device, cause the first network element to abstain from sending an application-level message to the second network element for maintaining a service between the communication device and the second network element. The abstaining may only last until a subsequent radio-level procedure with the communication device has been successfully completed. Alternatively or additionally, the abstaining may only last until a subsequent application-level message for maintaining the service has been received from the communication device for transmission to the second network element.

[0063] Corresponding operations for the communication device are described in relation to the flowchart of Figure 7.

[0064] At 701 , a communication device is configured to operate in a second mode. In the second mode, on successful completion of a radio-level procedure with a first network element, a radio-level part of the communication device abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

[0065] The communication device may be configured to receive signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure between the first network element and a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element (e.g. a service provider).

[0066] The communication device may be arranged to transmit to the first network element an indication that the communication device will not be sending the application-level message. Said indication may comprise at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode. Said indication may comprise at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application-level message for transmission to the second network element.

[0067] The communication device may be configured to receive, from the first network element, an instruction to enter the second mode. The above-mentioned indication may be transmitted in response to this instruction. The indication may be explicit or implicit (such as being inferable through the subsequent operations of the communication device).

[0068] The communication device may be further configured to, when the first network element is operating in the first mode, generate the application level messages and pass these application-level messages to the medium access control-level and/or radio-level of the communication device for transmission to the first network element. The medium access control-level and/or radio-level may abstain from transmitting these application-level messages (as per the abstaining described above). To ensure that the application-level operations still work as expected, the medium access control- level and/or radio-level may generate (and send to the application-level) application- level acknowledgements for the application-level messages.

[0069] For both of Figures 6 and 7, the application level message may be a first type of message (such as a“sign-of-life” message or other types of periodic messages), and each of the communication device and the first network element may be configured to exit from their respective modes when no messages of the first type are transmitted by the communication device to the first network node within a predetermined time period.. Exiting the first mode means that the first network element will only send the messages of the first type to the second network element on receipt from the communication device of a message of the first type. In other words, the application-level message is no longer generated independently of receipt of the application-level message from the communication device. Exiting the mode of the communication device means that the communication device will no longer abstain from sending the application-level messages received from the application-level of the communication device over the radio interface to the first network element.

[0070] For both of the above described systems, the radio-level procedure may be performed at least as frequently as the application-level messages that are supposed to be provided to the second network element/service provider. The term “handshaking procedure” is used herein to indicate, for example, an exchange of messages between the two entities performing the handshaking procedure.

[0071] The proposed method allows for a communication device to skip, or otherwise abstain from, actual transmissions of frequent small packets over the air from/to targeted individual F-devices. This may save a considerable amount of radio resources during normal operation of IAC systems being served by an ultra-x graded carrier.

[0072] The first and second modes may be referred to as implicit radio bearer (RB) service modes over the serving ultra-x graded carrier, as the existence of the radio bearer implicitly indicates that a service should be maintained.

[0073] However, that ultra-x requirements can be reassured on radio level does not mean that end-to-end application level handshaking is not needed. That is the end-to- end application level handshaking messages such as“sign-of-life” and corresponding acknowledge messages are also needed on top of radio level handshake procedure. Furthermore, the implicit radio bearer service mode does not mean there is no radio bearer established for data transmissions of the applications being served, such as PROFIsafe. The implicit RB mode is activated on an established RB of an individual communication device for efficient support of the application. That is the transmission of certain messages (e.g. frequent and small-sized messages, such as“sign-of-life” and/or“ack” messages) can be skipped, but other messages are transmitted as per their conventional configuration on the established RB.

[0074] To illustrate potential benefits of the invention, potential applications of the provided teachings of Figures 6 and 7 to the systems of Figures 4 and 5 are detailed below with reference to Figures 8 to 11.

[0075] Figure 8 illustrates communications between an application part 801 and a radio part 802 of a communication device 803 (e.g. an F-Device), communications between the radio part 802 of the communication device 803 and the access point 804 (depicted as an gNb in this example), and communications between the access point 804 and the application-level part of F-Host 805 over the network 806 separating the access point 804 and the F-host 805.

[0076] As shown in Figure 8, as a first step, the radio part 802 of the communication device 803 sets up a radio bearer suitable for an ultra-x graded communications session. The application part 801 of the communication device subsequently performs end-to-end service flow over the established radio bearer with the application-level part of the F-host 805.

[0077] The established radio bearer requires, according to the operating radio protocol between the communication device 803 and the access point 804, a radio-level handshaking procedure to be performed once per time period. This time period is indicated as 807. At 808, the application level part 801 of the communication device 803 indicates to the radio part 802 that a“sign-of-life” indication should be transmitted from the communication device 803 to the F-host 805. However, according to the present teachings, the radio part 802 of the communication device 803 does not in fact transmit this indication to the access point 804 for transmission to F-host 805. Instead, no transmission is made. However, the access point 804 generates this application- level“sign-of-life” message anyway for transmission to the F-host 805. The process is then repeated.

[0078] The F-host 805 may also be configured to provide an application-level acknowledgement of the received sign-of-life indications at 809. This acknowledgement may be transmitted after several sign-of-life indications have been transmitted by the access point 804 since the previous acknowledgement was transmitted by the F-host 805.

[0079] There are at least two potential ways in which the access point 804 may react to this acknowledgment. As a first example, the access point 804 may skip transmission of the received acknowledgement to the communication device, whilst the radio part 802 of the communication device 803 autonomously/independently generates an application-level acknowledgement for transmission to the application- level part 801 of the communication device 803. As a second example, the access point 804 may provide the received acknowledgment to the radio part 802 of the communication device 803, which then autonomously/independently generates an application-level acknowledgement for transmission to the application-level part 801 of the communication device 803. The radio part 802 of the communication device 803 may also transmit a radio-level acknowledgement for the received acknowledgment to the access point 804. The second option represents a configuration in which implicit RB mode is activated only in the uplink direction, and not in the downlink direction.

[0080] The message exchange at 810 provides an example of messages that may be exchanged in the event that the radio-level handshake procedure between the access point 804 and the communication device 803 fails. In this case, the radio-level part 802 of the communication device 803 does not abstain from transmitting the received

“sign-of-life” indication from the application level part 801 of the communication device to the access point 804. In this case, the access point 804 will only transmit the application-level sign-of-life message to the F-host 805 on receipt of this message from the communication device 803 (as the radio-level handshake procedure failed). The access point 804 may also transmit a radio-level acknowledgement of this received sign-of-life message to the radio-level part 802 of the communication device 803.

[0081] The message exchange at 811 provides an example of a message sequence when the application-level part wants to send a message to F-host 805 that is not a small, periodic message (such as a sign-of-life message).

[0082] In this case, subsequent to the radio-level handshaking protocol being successfully completed, the application-level part 801 of the communication device sends the other message to the radio-level part 802 of the communication device 803. The radio-level part 802 then sends this other message to the access point 804, which in turn sends it to the F-host 805 over network 806, and transmits a radio-level acknowledgment for this message back to the communication device 803.

[0083] Figure 9 also illustrates some potential configuration related signalling message exchanges between an access point 901 and a communication device 902 according to aspects of the present teachings.

[0084] As a first step, access point 901 is arranged to provide an ultra-x graded carrier to the communication device 902 for providing for served IAC users and systems. As a second step, this carrier is used to provide the user equipment with a radio bearer service for a PROFIsafe application on the commnication device 902.

[0085] At 903, the access point 901 indicates that it may support a first implicit radio bearer service mode, as described above. This ability is indicated to the communication device 902 via a transmitted message from the access point 901. The information comprising the ability may also comprise details of supported application level protocols such as PROFIsafe; ranges of related application level handshaking periodical time intervals such as from 10ms to 100ms; and related reassured ultra-x KPI levels. The ranges and KPI levels, if not explicitly configured, may be derived from the corresponding parameters configured for the radio level handshaking of the serving ultra-x graded carrier. The information indication can be signalled to the relevant communication device using either common control signalling (such as System Information Blocks in current 3GPP specifications) or dedicated control signalling (communication device specific scheduling). [0086] The access point 901 may also signal, via the same transmitted message or via a separate message, a request for information on the communication device’s capabilities and the application’s operating parameters for establishing this implicit service mode activation. This information request may be used to trigger the relevant communication device to indicate related communication device capability, provide necessary assistant information and/or request activation/deactivation of the implicit radio bearer service mode. The information request and/or the response to this information request from the communication device may comprise, for example, application-protocol related information and some active context thereof, for examples, PROFIsafe, PROFIsafe application level timing reference and further synchronizing information such as periodical time interval of the related handshaking messages like“sign-of-life” and“ack”.

[0087] Once this assistance information has been returned by the communication device 902, the access point 901 may determine to activate the implicit radio bearer service mode at 904. The determining step may be made in dependence on a plurality of factors. Example factors include assistance information from the communication device, reassured KPI levels and related radio level handshaking configurations, cell load states of the serving ultra-x graded carrier, etc.

[0088] If not explicitly configured before this time, this activation may be signalled as a request to the communication device 902, which may then respond in the negative or the positive.

[0089] The request may comprise information providing the communication device with control configuration to what extent the implicit radio bearer service mode is applied. For example, the request may specify that the implicit radio bearer service mode is applied to the normal and correct operation of the ongoing PROFIsafe, implying to cover the transactions of only minimal“sign-of-life” and“acknowledgement” messages, and timing to start the implicit radio bearer service mode.

[0090] The access point then expects to receive a response from the communication device. The response, if the communication device 902 responds in the positive, indicates that the implicit radio bearer service mode is activated at the communication device side and may further comprise initial active contexts thereof to assist the access point 901 in operations related to independently generating the sign-of-life indications for the F-host. These operations may include the ciphering and integrity protection context of the targeted application messages (if applied), the sequence number of the first application message after activating the implicit radio bearer service mode, etc. If the request is acceded to by the communication device 902, the devices 901 , 902 enter the implicit radio bearer service mode, and operation is, for example, as per Figure 8. If the request is not acceded to by the communication device 901 , 902, the devices do not enter the implicit radio bearer service mode (i.e. they continue operating as per the pre-established case).

[0091] Once the implicit radio bearer service mode has been activated, the access point 901 may, on behalf of the communication device, filter and terminate “acknowledgement” messages received from the network side, i.e., F-host, and generate and send the “sign-of-life” messages to the network side, i.e., F-host, periodically based on the positive outcomes of the radio level handshaking (as per Figure 8).

[0092] The access point 901 and/or the communication device 902 may terminate the implicit radio bearer service in a number of different ways. For example, the access point 901 may receive from the communication device 902 an indication, explicit message or a scheduling request from the communication device to stop the implicit radio bearer service mode. The explicit message may be an extensive status report message or a targeted message if the outcomes of the radio level handshaking is not adequate or negative. That is, whenever either the communication device 902 or the access point 901 determines that the radio level handshaking fails to provide the reassured KPI level needed for the service requirements of the ongoing application, i.e., PROFIsafe, the application messages can be sent explicitly as usual. As per the example of Figure 8, the usual explicit non-skipping radio bearer service is assumed for all non-targeted kinds of messages (other than “sign-of-life” and “ack”). The mechanism may also be configured such that that the implicit radio bearer service mode is applied for“sign-of-life” in uplink only and all the downlink traffic is served with explicit RB service as usual. In other words, the implicit radio bearer service mode may be applied in only one direction. Nevertheless, the implicit radio bearer service mode may be extended to keep the application layer protocol running smoothly without any break even when there may be some tolerable break on the radio connection (e.g., a failure in handshaking on the radio level).

[0093] A slightly different mechanism to that shown in Figure 8 is shown in Figure 10. [0094] Figure 10 illustrates communications between an application part 1001 and a radio part 1002 of a communication device 1003 (e.g. an F-Device), communications between the radio part 1002 of the communication device 1003 and the access point 804, and communications between the access point 1004 and the application-level part of F-Flost 1005 over the network 1006 separating the access point 1004 and the F-host 1005.

[0095] At 1007, the communication device 1003 and the access point 1004 successfully complete a radio-level handshake procedure. Then, an application-level part 1001 of the communication device 1003 sends a sign-of life message to the radio- part 1002 of the communication device, which is subsequently transmitted over the radio interface to the access point 1004. On receipt of this sign-of-life message, the access point 1004 transmits it over the network 1006 to the F-host 1005, and provides a radio-level acknowledgement for the received sign-of-life message to the communication device 1003. The F-host also acknowledges receipt of the sign-of-life message to the access point 1004 by transmitting an acknowledgement.. The access point 1004 passes this acknowledgement on to the application-level part 1001 of the communication device 1003. The radio-level part 1002 of the communication device 1003 sends a radio-level acknowledgment for this message from the access point 1004.

[0096] The operation illustrated in system of Figure 10 is substantially in accordance with the message exchange illustrated in Figure 8. Flowever, this operation differs in that the access point 1004 is arranged to consider the watchdog interval of a particular type of application-level message, and to only schedule resources for transmitting a single application-level message of that type to the F-host 1005 within a single watchdog interval. For example, if a“sign-of-life” message is transmitted every 10ms, and the watchdog interval is 30ms, the access point 1004 may schedule resources for transmitting only one“sign-of-life” message to the F-host 1005 in this 30ms time interval, saving resources by abstaining from transmitting the other two“sign-of-life” messages that would ordinarily also be transmitted within that time interval.

[0097] The usefulness of such a mechanism of Figure 10 is discussed in the context of a PROFIsafe system.

[0098] A case of a PROFIsafe application for an IAC system in which each of F- devices and the F-host have to have a handshake at least once per every 30m is considered. The PROFIsafe application at the F-device side sends a“sign-of-life” every 10ms and the F-host watch-dog sends an“acknowledgement” back for each and every received“sign-of-life” message within every 30ms. In this case, if the access point with an ultra-x graded carrier is able to reassure that at least 1 message can get though per 30ms in each direction then it should be more efficient, from a radio resource utilization perspective, to let the access point to decide to schedule for one or more out of the 3 consecutive per-10ms“sign-of-life” messages from the F-device to be related to the F-host, and to abstain from transmitting the remaining two messages within the watch-dog period of 30ms. The access point may explicitly or implicitly configure the F-device to skip transmitting the rest of the messages per the watch-dog period of 30ms, as per the examples discussed above in reference to Figure 9.

[0099] Figure 11 illustrates how the above described mechanisms may be dealt with by protocol stacks of the access point and of the communicating device when operating in a 5G system.

[00100] As shown in Figure 11 , there is provided a communication device 1101 having a physical layer, a media access control (MAC) layer, a radio link control (RLC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Service Data Adaptation Protocol (SDAP) layer and an application protocol layer.

[00101] Also provided is an access point 1102 having corresponding protocol layers/

Radio-level handshakes are performed at the MAC and physical layers. Information on the outcomes of the radio level handshakes are provided from each MAC layer to their respective SDAP layers. The respective SDAP layers exchange sign-of-life and acknowledgement information with their respective application protocol parts based on these received indications. In other words, the SDAP is a suitable layer to terminate and generate the targeted application messages (“sign-of-life” for uplink and“ack” for downlink), based on communication device assistance information and feedback of radio handshaking outcomes from the local MAC. The radio level handshaking can be based on either common or dedicated signals/channels such as: the Physical Random Access CFIannel, the uplink sounding signal, the Physical Uplink Control CFIannel, uplink grant-free or uplink grant based transmissions, the Primary or Secondary Synchronisation channels, the Broadcast Channel, Physical Downlink Control Channel, and/or more user specific multicast/broadcast/unicast transmissions for downlink.

[00102] As discussed above, it should be appreciated that PROFIsafe is merely one example of a system with which the present teachings may be used. Other embodiments may be used where periodic messages, such as sign-of-life information or similar, needs to be provided via a wireless link. It is understood that in the above- provided examples, specific examples of sign-of-life messages are merely examples, and may also be applied to other types of periodic application-level messages.

[00103] The required data processing apparatus and functions may be provided by means of one or more data processors. The described functions may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASystem InformationC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. One or more of the steps discussed in relation to Figures 6 and/or 7 may be performed by one or more processors in conjunction with one or more memories.

[00104] An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded or otherwise provided on an appropriate data processing apparatus. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[00105] It is noted that whilst embodiments have been described in relation to certain architectures, similar principles can be applied to other systems. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted that different combinations of different embodiments are possible. It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the spirit and scope of the present invention.

Claims

1 . A method comprising:

operating, by a first network element, in a first mode, in which, on successful completion of a radio-level procedure with a communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element.

2. A method as claimed in claim 1 , further comprising a first network element sending the application-level message to the second network element regardless of whether or not the first network element receives the application- level message from the communication device.

3. A method as claimed in any preceding claim, further comprising signalling to the communication device that the first network element is able to operate in the first mode.

4. A method as claimed in any preceding claim, further comprising receiving from the communication device an indication that the communication device is operating in a second mode in which the communication device will not be sending the application-level message.

5. A method as claimed in claim 4, further comprising transmitting to the communication device an instruction for the communication device to enter the second mode.

6. A method as claimed in any of claims 4 and 5, wherein said indication comprises at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst operating in the first mode.

7. A method as claimed in any of claims 4 to 6, wherein said indication is at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted.

8. A method as claimed in any of claims 4 to 7, wherein said indication comprises at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application-level message for transmission to the second network element.

9. A method as claimed in any preceding claim, wherein said first mode comprises, on failure of a radio-level procedure with a communication device, the network element does not send an application-level message to the second network element for maintaining a service between the communication device and the second network element unless the application-level message has been received from the communication device.

10. A method comprising:

operating, by a communication device, in a second mode, in which, on successful completion of a radio-level procedure with a first network element, a radio-level part of the communication device:

abstains from sending an application-level message to a second network element via the first network element that maintains a service between the communication device and the second network element.

11. A method as claimed in claim 10, further comprising receiving signalling from the first network element indicating that the first network element is able to operate in a first mode in which, on successful completion of a radio-level procedure with the communication device, the first network element sends an application-level message to a second network element that maintains a service between the communication device and the second network element regardless of whether or not the first network element receives the application- level message from the communication device.

12. A method as claimed in any of claim 10 to 11 , wherein operating the communication device in the second mode further causes the radio-level part of the communication device to:

send an acknowledgement to an application-level message received from an application-level part of the communication device.

13. A method as claimed in any of claims 10 to 12, further comprising transmitting to the first network element an indication that the communication device will not be sending the application-level message.

14. A method as claimed in claim 13, wherein said indication comprises at least one parameter that indicates how frequently the first network element should send application-level messages to the second network element whilst the communication device is operating in the second mode.

15. A method as claimed in any of claims 13 to 14, wherein said indication is at least one of: application protocol related information; active context of the communication devices; application level timing and synchronization information; ciphering and integrity protection context and a sequence number of the first message in the sequence of application-level messages being transmitted.

16. A method as claimed in any of claims 13 to 15, wherein said indication comprises at least one parameter that indicates how frequently the user equipment will send to the first network element at least one type of application- level message for transmission to the second network element.

17. A method as claimed in any of claims 10 to 16, wherein the application level message is a first type of message, and further comprising exiting from the first mode when no messages of the first type are transmitted by the communication device within a predetermined time period.

18. A method as claimed in any of claims 10 to 17, further comprising: entering the second mode in response to a received instruction from the first network element.

19. A method as claimed in any preceding claim, wherein the radio-level procedure is a radio-level handshake procedure.

20. An apparatus comprising:

at least one processor;

and at least one memory comprising code that, when executed on the at least one processor, causes the at least one processor to perform the steps of any of claims 1 to 9.

21.An apparatus comprising:

at least one processor;

and at least one memory comprising code that, when executed on the at least one processor, causes the at least one processor to perform the steps of any of claims 10 to 18.

22. A computer program comprising computer code that, when executed on an apparatus, causes the apparatus to perform the steps of any of claims 1 to 9.

23. A computer program comprising computer code that, when executed on an apparatus, causes the apparatus to perform the steps of any of claims 10 to 19.