WO2021008672A1

WO2021008672A1 - Apparatus, method and computer program for reliable transmission of commands

Info

Publication number: WO2021008672A1
Application number: PCT/EP2019/068861
Authority: WO
Inventors: Rakash SIVASIVA GANESAN
Original assignee: Nokia Solutions And Networks Gmbh & Co. Kg
Priority date: 2019-07-12
Filing date: 2019-07-12
Publication date: 2021-01-21

Abstract

There is provided an apparatus, said apparatus comprising means for receiving at least one message from at least one network entity at the apparatus via a first type radio link, providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determining whether to execute the at least one message based on the indication.

Description

Title

APPARATUS, METHOD AND COMPUTER PROGRAM FOR RELIABLE TRANSMISSION OF

COMMANDS

Field

The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to enabling synchronised message processing with high reliability and low overhead.

Background

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

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. 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. The 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. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP).

Summary

In a first aspect there is provided an apparatus, said apparatus comprising means for receiving at least one message from at least one network entity at the apparatus via a first type radio link, providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determining whether to execute the at least one message based on the indication.

Means for determining whether to execute the at least one message based on the indication may comprise means for receiving a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one message or the indication not to execute the at least one first message.

Means for determining whether to execute the at least one message based on the indication may comprise means for determining to execute the at least one first message if the indication is not received at the user device after a given time period.

The apparatus may comprise means for storing the at least one message in a first layer and on determining to execute the at least one first message, forwarding the at least one first message to a higher layer.

The first layer may be a service data adaptation protocol layer. The higher layer is an application layer. The first layer may be a medium access control layer. The higher layer may be a radio link control layer.

The apparatus may be a user device of a group of user devices. The at least one message may be one of a set of messages that the at least one network entity sends to each user device of the group of user devices.

The indication may comprise an indication of whether or not each of the group of user devices has received one of the set of message from the at least one network entity.

The feedback information may comprise an explicit acknowledgement/negative acknowledgment, ACK/NACK, message.

The feedback information may be implicit.

In a second aspect there is provided an apparatus, said apparatus comprising means for providing one of a set of messages to each user device of a group of user devices, via first type radio links, receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device, determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

The first type radio links may comprise a radio link common to each of the group of user devices.

Each first type radio link may have an independent value for reliability.

The second type radio links may comprise a radio link common to each of the group of user devices.

Each second type radio link may have an independent value for reliability.

The apparatus may comprise means for determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if so, providing the indication to each of the group of user devices to execute the one of the set of messages.

The apparatus may comprise means for determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if not, providing the indication to each of the group of user devices, to not execute the one of the set of messages.

The apparatus may comprise means for, if the feedback information indicates that the one of the set of message has not been received at each of the group of user devices, providing the one of the set of messages to at least one of the group of user devices again and receiving feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device.

The apparatus may comprise means for receiving from a network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the messages are addressed and a synchronised reliability value with which the messages are to be sent.

The apparatus may comprise means for providing an indication to the network entity of whether the set of messages was received by the group of user devices with the synchronised reliability value.

The network entity may be an application function or a core network function.

The set of messages may be transmitted by one or more protocol data unit sessions and the apparatus may comprise means for accessing and detecting the set of messages for the group of user devices carried by the one or more protocol data unit sessions and transmitting the set of messages to the group of user devices via the first type radio links.

The feedback information may be implicit.

In a third aspect there is provided a method comprising receiving at least one message from at least one network entity at an apparatus via a first type radio link, providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determining whether to execute the at least one message based on the indication.

Determining whether to execute the at least one message based on the indication may comprise receiving a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one message or the indication not to execute the at least one first message.

Determining whether to execute the at least one message based on the indication may comprise determining to execute the at least one first message if the indication is not received at the user device after a given time period.

The method may comprise storing the at least one message in a first layer and on determining to execute the at least one first message, forwarding the at least one first message to a higher layer.

The first layer may be a service data adaptation protocol layer. The higher layer is an application layer.

The first layer may be a medium access control layer. The higher layer may be a radio link control layer.

The feedback information may be implicit. In a fourth aspect there is provided a method comprising providing one of a set of messages to each user device of a group of user devices, via first type radio links, receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device, determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

Each first type radio link may have an independent value for reliability.

Each second type radio link may have an independent value for reliability.

The method may comprise determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if so, providing the indication to each of the group of user devices to execute the one of the set of messages.

The method may comprise determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if not, providing the indication to each of the group of user devices, to not execute the one of the set of messages.

The method may comprise, if the feedback information indicates that the one of the set of message has not been received at each of the group of user devices, providing the one of the set of messages to at least one of the group of user devices again and receiving feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device. The method may comprise receiving from a network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the messages are addressed and a synchronised reliability value with which the messages are to be sent.

The method may comprise providing an indication to the network entity of whether the set of messages was received by the group of user devices with the synchronised reliability value.

The network entity may be an application function or a core network function.

The set of messages may be transmitted by one or more protocol data unit sessions and the method may comprise accessing and detecting the set of messages for the group of user devices carried by the one or more protocol data unit sessions and transmitting the set of messages to the group of user devices via the first type radio links.

The feedback information may be implicit.

In a fifth aspect there is provided an apparatus comprising: at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: receive at least one message from at least one network entity at an apparatus via a first type radio link;

provide feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receive an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determine whether to execute the at least one message based on the indication.

The apparatus may be configured to receive a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one message or the indication not to execute the at least one first message.

The apparatus may be configured to determine to execute the at least one first message if the indication is not received at the user device after a given time period. The apparatus may be configured to store the at least one message in a first layer and on determining to execute the at least one first message, forward the at least one first message to a higher layer.

The feedback information may be implicit.

In a sixth aspect there is provided an apparatus comprising: at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: provide one of a set of messages to each user device of a group of user devices, via first type radio links, receive feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device, determine whether each user device of the group of user devices has received the one of the set of messages based on the feedback information and provide, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

The first type radio links may comprise a radio link common to each of the group of user devices. Each first type radio link may have an independent value for reliability.

Each second type radio link may have an independent value for reliability.

The apparatus may be configured to determine, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if so, provide the indication to each of the group of user devices to execute the one of the set of messages.

The apparatus may be configured to determine, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if not, provide the indication to each of the group of user devices, to not execute the one of the set of messages.

The apparatus may be configured to, if the feedback information indicates that the one of the set of message has not been received at each of the group of user devices, provide the one of the set of messages to at least one of the group of user devices again and receive feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device.

The apparatus may be configured to receive from a network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the messages are addressed and a synchronised reliability value with which the messages are to be sent.

The apparatus may be configured to provide an indication to the network entity of whether the set of messages was received by the group of user devices with the synchronised reliability value.

The network entity may be an application function or a core network function.

The set of messages may be transmitted by one or more protocol data unit sessions and the apparatus may comprise means for accessing and detecting the set of messages for the group of user devices carried by the one or more protocol data unit sessions and transmitting the set of messages to the group of user devices via the first type radio links. The feedback information may comprise an explicit acknowledgement/negative acknowledgment, ACK/NACK, message.

The feedback information may be implicit.

In a seventh aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following receiving at least one message from at least one network entity at an apparatus via a first type radio link, providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determining whether to execute the at least one message based on the indication.

The apparatus may be caused to perform storing the at least one message in a first layer and on determining to execute the at least one first message, forwarding the at least one first message to a higher layer.

The apparatus may be a user device of a group of user devices. The at least one message may be one of a set of messages that the at least one network entity sends to each user device of the group of user devices. The indication may comprise an indication of whether or not each of the group of user devices has received one of the set of message from the at least one network entity.

The feedback information may be implicit.

In an eighth aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following providing one of a set of messages to each user device of a group of user devices, via first type radio links, receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device, determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

Each first type radio link may have an independent value for reliability.

Each second type radio link may have an independent value for reliability.

The apparatus may be caused to perform determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if so, providing the indication to each of the group of user devices to execute the one of the set of messages.

The apparatus may be caused to perform determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if not, providing the indication to each of the group of user devices, to not execute the one of the set of messages.

The apparatus may be caused to perform, if the feedback information indicates that the one of the set of message has not been received at each of the group of user devices, providing the one of the set of messages to at least one of the group of user devices again and receiving feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device.

The apparatus may be caused to perform receiving from a network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the messages are addressed and a synchronised reliability value with which the messages are to be sent.

The apparatus may be caused to perform providing an indication to the network entity of whether the set of messages was received by the group of user devices with the synchronised reliability value.

The network entity may be an application function or a core network function.

The feedback information may be implicit.

In a ninth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the third or fourth aspect.

In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above. Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a base station and a plurality of communication devices;

Figure 2 shows a schematic diagram of an example mobile communication device;

Figure 3 shows a schematic diagram of an example control apparatus;

Figure 4 shows a perspective view of two AGVs cooperatively transporting an object;

Figure 5 shows a flowchart of a method according to an example embodiment;

Figure 6 shows a flowchart of a method according to an example embodiment;

Figure 7 shows a signalling flow for an example embodiment;

Figure 8 shows a signalling flow for an example embodiment;

Figure 9a shows a schematic diagram of feedback according to an example embodiment; Figure 9b shows a schematic diagram of feedback according to an example embodiment; Figure 9c shows a schematic diagram of feedback according to an example embodiment; Figure 9d shows a schematic diagram of feedback according to an example embodiment.

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in figure 1 , mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. 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 apparatuses. 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. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.

In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network.

The smaller base stations 1 16, 1 18 and 120 may also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 1 16, 1 18 and 120 may be pico or femto level base stations or the like. In the example, stations 1 16 and 1 18 are connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided. Smaller base stations 1 16, 118 and 120 may be part of a second network, for example WLAN and may be WLAN APs.

The communication devices 102, 104, 105 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on.

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 (LTE-A) employs a radio mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network known as the Evolved Packet Core (EPC). Base stations of such systems are known as evolved or enhanced Node Bs (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). A base station can provide coverage for an entire cell or similar radio service area. Core network elements include Mobility Management Entity (MME), Serving Gateway (S-GW) and Packet Gateway (P-GW).

An example of a suitable communications system is the 5G or NR concept. Network architecture in NR may be similar to that of LTE-advanced. Base stations of NR systems may be known as next generation Node Bs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer QoS support, and some on-demand requirements for e.g. QoS levels to support QoE of 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. NR may use multiple input - multiple output (Ml MO) 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.

Future networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into“building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. 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.

An example 5G core network (CN) comprises functional entities. The CN is connected to a UE via the radio access network (RAN). An UPF (User Plane Function) whose role is called PSA (PDU Session Anchor) may be responsible for forwarding frames back and forth between the DN (data network) and the tunnels established over the 5G towards the UE(s) exchanging traffic with the DN.

The UPF is controlled by an SMF (Session Management Function) that receives policies from a PCF (Policy Control Function). The CN may also include an AMF (Access & Mobility Function).

A possible mobile 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 user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

A mobile 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. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The mobile 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 mobile device.

Figure 3 shows an example of a control apparatus 300 for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, eNB or gNB, a relay node or a core network node such as an MME or S-GW or P-GW, or a core network function such as AMF/SMF, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head.

In the tactile industrial network, also known as Industrial loT (MoT) or Industry 4.0 networks, 3GPP technologies are applied in addition to wired time sensitive networking (TSN) in industrial environments to provide flexibility (in terms of mobility) and scalability (in terms of number of sensors or actuators).

High reliability is a key requirement in industrial communication. Highly reliable communication is relatively challenging in wireless communication system such as 5GS compared to the wired communication systems like TSN using ethernet cables. Channel characteristics such as fading, interference, blocking, etc. may make the wireless channel less reliable than the wired system. To enhance the reliability of wireless channels different processes, e.g., channel coding, adaptive modulation, and multiple redundant transmissions in time, frequency and spatial dimensions may be performed. In all these processes, high reliability is achieved through redundancy. Redundant transmission may lead to a reduction in system throughput. The higher the reliability requirement, the more redundant the transmitted data is and so less data is transmitted using the available bandwidth

Figure 4 shows an example use case of a tactile industrial network. Here, two automatic guided vehicles (AGVs) cooperatively transport a large heavy object which cannot be carried by a single AGV itself. In such scenarios with cooperative functioning of several devices, synchronized reliability (SR), defined as the probability that a set of message is received either at all the devices or at none of the devices, is more important than the reliability of individual devices. That is, if a command is send to all the AGVs, then it should either be successfully transmitted to all the AGVs or it should be transmitted to none of the AGVs. For example, a controller at the edge cloud sends a command to stop all the AGVs from moving ahead. If this command is successfully received at one of the two AGVs while the other AGV does not, then one AGV stops while the other continues to move. In this case, the object being carried is either distorted or broken. In order to avoid such incidents, it is necessary to achieve a very high SR.

To achieve high SR, a direct approach would be to achieve high group reliability (GR). GR is defined as the probability a message is transmitted to all the devices in the group. In the cooperative transport of goods use case, the messages for all the AGVs are put together as a single message and transmitted to all the AGVs. To achieve high GR, each of the individual communication links need to be highly reliable. If the reliability of individual links is 0.9999, then the GR is 0.9998. Hence, to achieve a specific GR, the reliability of the individual links should be higher than the GR and this increases with the increase in the number of devices in the group. Hence, increasing the reliability of each communication links leads to increase in the redundancy, reducing the throughput in the system. High GR may provide high SR. However, for high SR, it is not necessary to have a high GR and the associated amount of redundant transmission. The following may provide a method to achieve high SR with relatively low redundancy.

Figure 5 shows a flowchart of a method according to an example embodiment. The method may be performed at a network entity. The network entity may be, e.g., a gNB. The network entity may be an application function.

In a first step, S1 , the method comprises providing one of a set of messages to each user device of a group of user devices, via first type radio links.

In a second step, S2, the method comprises receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to the one user device has been received at the one user device.

In a third step, S3, the method comprises determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information

In a fourth step, S4, the method comprises providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

The first type radio links may comprise a radio link common to each of the group of user devices. The second type radio links may comprise a radio link common to each of the group of user devices

Alternatively, each first type radio link may be a separate radio link. Each first type radio link may have an independent value for reliability. Each second type radio link may be a separate radio link and each second type radio link may have an independent value for reliability.

The method may comprise determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of user devices and, if so, providing the indication to each of the group of user devices to execute the one of the set of messages. The method may comprise determining, based on the feedback information, whether one of the set of messages has been received at each of the group of user devices and, if not providing the indication to each of the group of user devices not to execute the one of the set of messages.

To achieve the required high reliability, the indication to execute or not to execute the one of the set of messages may be sent using as a single transmission or multiple transmission (e.g., first and re-transmission, multiple copies transmitted from the same or different gNBs, or any other suitable reliability enhancement transmission mechanism).

If the feedback information indicates that the one of the set of messages has not been received at each of the group of user devices, the method may comprise providing the one of the set of messages to at least one of the group of user devices again and receiving feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device.

A base station accesses data across different PDU sessions or channels or transport blocks and may apply the proposed method across them. That is, the set of messages may be transmitted by one or more protocol data unit sessions and the method may comprise accessing and detecting the set of messages for the group of user devices carried by the one or more protocol data unit sessions and transmitting the set of messages to the group of user devices via the first type radio links.

Figure 6 shows a flowchart of a method according to an example embodiment. The method may be performed at a user device.

In a first step, T1 , the method comprises receiving at least one message from at least one network entity at an apparatus via a first type radio link.

In a second step, T2, the method comprises providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus.

In a third step T3, the method comprises receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link. In a fourth step, T4, the method comprises determining whether to execute the at least one message based on the indication.

The at least one network entity from which the at least one message is received at the apparatus may be, e.g., a gNB when the method is applied in a 3GPP scenario. Alternatively, the network entity may be an application function.

The method may comprise storing the at least one message in a first layer and, on determining to execute the at least one first message, forwarding the at least one first message to a higher layer. The first layer may be a SDAP layer and the higher layer may be an application layer. Alternatively, the first layer may be a MAC layer and the higher layer may be an RLC layer.

The user device may be a device of an lloT network, for example an AGV. The feedback may be explicit or implicit. The feedback may comprise an ACK/NACK message. The NACK messages may be sent with a higher reliability than the ACK messages.

In an example embodiment, at least one base station transmits a set of messages to a group of devices with a link reliability much smaller than the required SR. The link reliability may be a function of the requirements provided by the network, e.g., delay budget, and the characteristics of the communication channel, e.g., propagation delay.

The base station collects implicit or explicit feedback from the group of devices about the successful reception of the messages. Depending on the time budget, the base station may re-transmit messages to one or more devices of the group and collect feedback again. Based on the feedback, the base station identifies if all the devices have successfully received the messages.

The base station then confirms, either implicitly or explicitly to the group of devices to use the message received before. This confirmation is transmitted with high redundancy at least as high as the SR requested by the network. The UE shall hold the packet at different layers, waiting for a confirmation message from the gNB before forwarding it to a higher layer

This method may ensure that the confirmation message (i.e. an indication to execute or not to execute a message) is received by all the AGVs while avoiding reducing throughput in the system. The messages are transmitted to the AGVs through less reliable links, e.g. 0.99. The AGVs provide implicit or explicit feedback to the transmitter.

Based on the feedback, the transmitter confirms to all the AGVs, either implicitly or explicitly, if the AGV can use the packets that were transmitted before. For this confirmation, high redundancy e.g. 0.9999 is used during the transmission, so the reliability of the confirmation message is as high as the expected SR.

The set of messages may not be properly received at one or more AGVs or the feedback from one or more AGVs may not be properly received. In any case, when the transmitter is not sure if the messages are received at all the AGVs, then it informs all the AGVs not to use the message sent before. However, when the transmitter confirms that the messages transmitted before can be used, then it is sure that all the AGVs have received the messages.

The set of messages may be transmitted with very low redundancy while the indication, or confirmation message, (which may be as small as a single bit) may be transmitted with very high redundancy.

The method as described with reference to Figure 5 may comprise receiving from a further network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the message are to be sent and a synchronised reliability value with which the messages are to be sent.

The reliability of the second type radio links is defined based on the synchronised reliability value. The reliability of the second type radio links is at least as reliable as the synchronized reliability value. Note that in the case where multiple transmissions (e.g., first transmission + one re-transmission) are used for the second type of reliability links, then the reliability of the second type radio link reliability is the effective reliability of the multiple transmission. The reliability value of the second type radio link may configured by the network. This may be part of the QoS frame work of 5GS. The application may request the All/None service (i.e. to apply the described method) with a specific reliability value. The reliability value for the first type radio link may be exposed or configured by the network. This may allow the application to control how often all the messages are transmitted and how often none of the messages are transmitted. If the reliability value for the first type radio link is not configured by the network, the gNB may transmit the messages as normal best effort traffic, in which case,“don’t execute” messages may be transmitted more frequently compared to the case when the messages are transmitted with relatively higher reliability e.g. as URLLC traffic.

For example, the network entity (e.g., base station) may receive, from a further network entity, a set of messages with a corresponding set of devices to which the messages are addressed, with the constraint that the messages are transmitted to either all the devices or none of the devices with a specific SR. The further network entity within the 5G system may be the AMF/SMF/PCF. Outside 3GPP network, this network entity may be the AF. In this case, the information goes through the SMF. E.g., the AF is informed by the gNB through the core network functionalities using a existing and/or new control plane procedure specified in 3GPP

When the SR is offered as TSC service by 5GS, the 5GS allows AF to mark or 5GS mark by itself a set of packets as belonging to a SR group. The SMF configures the gNB and the gNB configures the UE regarding the SR related information

The method may comprise providing an indication to the further network entity of whether the at least one first message was received by the group of user devices with the synchronised reliability value. That is, the base station may provide feedback to a second apparatus (e.g., to AMF/SMF/PCF or to AF through the AMF/SMF or PCF).

The method may be implemented in different layers of the communication system, e.g. Application layer, SDAP layer between gNB and UE or the MAC layer as part of the HARQ procedure. The available delay budget is a key factor deciding in which layer to implement the method.

In a Time Sensitive Communication (TSC) service of 5GS, there are different interfaces available for applications to support time sensitive wireless communication. The method provides an interface which allows the application to mark the same or different packet(s) addressed to different UEs as packets of a specific SR group. The sequence numbers of the packets are coordinated such that the 5GS can identify which set of packets among the sequence of packets are to be delivered simultaneously at a given time instant. One direct approach is to use the same sequence number for the set of packets to be delivered simultaneously.

Within 5GS, these set of packets may be transmitted on UE specific PDU sessions. The SMF indicates to the gNB the set of PDU sessions for which a given SR needs to be achieved. The gNB either re-uses the marking from the application or tags the packets of the SR group with a label. This label is used to indicate the lower layers e.g. to use the same priority, reliability levels etc. for the packets of the SR group.

In a first example embodiment, the method is implemented in the SDAP layer in the air- interface between gNB and UE.

Figure 7 shows an example signalling flow according to an example embodiment implemented in the SDAP layer.

In a first step the device connected to the UE (or the application running on the UE) triggers the UE to establish a connection with the application function. Initially, the UEs establish independent PDU sessions. Then the device communicates with the AF notifying it about the active connection established.

Now the AF sets the SR requirements at the PCF. The AF uses the IP addresses of the UEs as exposed by UPF (i.e., after NATing) to indicate the UEs that form the SR group. The PCF notifies the SMF regarding the policy change for the set of UEs. Then the SMF modifies the already established PDU sessions for UE1 and UE2 to update the SR related information. Namely, the SMF configures the gNB with the parameters needed to implement the proposed synchronized message transfer mechanism.

In this example, the proposed mechanism is implemented at the SDAP layer. The SMF informs gNB how the packets that belong to the same SR group are marked and how the sequence numbers of the packets are coordinated. The gNB configures the UE such that the UE holds the SDAP PDU till the UE receives an execute command and forwards the packet to the application layer only on reception of the execute command. If the UE receives a don’t execute command, then the packet is not forwarded to the application layer. The gNB shall indicate through SMF to the AF that the set of packets with a particular sequence number is delivered/not delivered to all the UEs. The method may be implemented on the application layer between the control application and the user device. In this case, the procedure is transparent to the 5GS system.

Figure 8 shows a signalling flow for an alternative example embodiment in which the method is implemented between the control application and the AGV.

In this signalling flow, two types of sessions are established between the control application and the application at the AGVs namely 1 ) a low reliability session for message transfer and for ACK and 2) a high reliability session for the NACK and execute/don’t execute messages.

There may be any suitable type of communication system including 5GS in between the control applications and the application at the AGVs. From the communication system perspective, the low and high reliability sessions are treated to be independent. The application at the controller and at the AGVs take care that the messages are either received at all the AGVs or none of the AGVs use the message information.

In the example implementation shown in Figure 7, the ACK/NACK and the Execute/Don’t Execute messages are explicitly transmitted. These messages may also be implicitly realized.

Figures 9a to 9d shows various example embodiments of how the user device may determine whether to execute the at least one message.

Determining whether to execute the at least one message based on the indication may comprise receiving a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one first message or the indication not to execute the at least one first message. That is, an explicit indication may be provided to the user device in a further message to execute or not execute the received message.

Figure 9a depicts the explicit feedback and execute/don’t execute realization, such as that depicted in Figure 7. In this example, the base station sends an explicit“Execute” or“Don’t Execute” message with high reliability based on the feedback. In Case 1 , there is successful transmission of a message to all of UE1 , UE2, UE3 and UE4. Each UE sends an ACK message and receives an explicit“Execute” message transmitted with a higher reliability than the initial transmission. In Case 2, transmission of the message to UE2 fails. UE2 does not send an ACK message and it is implicit that the message has not been successfully received at each of the user devices. The BS sends a“Don’t Execute” message with a higher reliability than the initial transmission. Figure 9b shows an explicit execute/don’t execute realisation, wherein the feedback is implicit. If, as shown in Case 1 , the BS does not receive a negative acknowledgment before a trigger time, it provides an explicit“Execute” message to each UE on the trigger. If the BS receives a NACK before the trigger, the BS sends a“Don’t Execute” message to each UE. This may save ACK signalling.

Determining whether to execute the at least one message based on the indication may comprise determining to execute the at least one message if the indication is not received at the user device after a given time period. That is, the indication to execute at least one first message may be implicit.

In the example shown in Figure 9c, the UE waits for N time slots and if no“don’t execute” command is received within the N time slots, then the user device executes the message (e.g., the user device forwards the message to the application layer at a pre-defined / specified time instant). In this example, the NACK feedback is implicit. That is, if the base station does not receive an ACK within a given time period, the base station assumes the message has not been successfully transmitted.

Figure 9d illustrates an example case where data arrives periodically. In this case, no explicit acknowledgment messages are sent and the“Execute” messages are implicit. If data does not arrive in time, then the UE sends a NACK message to the gNB. On receiving the NACK message, the gNB sends a don’t execute command to all the UEs to prevent them forwarding the packet to the application layer.

The options shown in Figures 9a, 9b, 9c and 9d involve different amounts of signalling overhead and may be chosen based on the traffic pattern. Also, the level of redundancy and hence, the reliability of the data, ack/nack and execute/don’t execute messages are trade offs between each other depending on the application requirements.

Methods as described with reference to the Figures above may ensure that messages received by the AGVs are used by them only after getting a confirmation from the transmitter that all the other AGVs have received their corresponding messages as well.

The method may be implemented in a user equipment as described with reference to Figure 2 or a control apparatus as described with reference to figure 3. An apparatus may comprise means for receiving at least one message from at least one network entity at the apparatus via a first type radio link, providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus, receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link and determining whether to execute the at least one message based on the indication.

Alternatively or in addition, an apparatus may comprise means for providing one of a set of messages to each user device of a group of user devices, via first type radio links, receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device, determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

It is noted that whilst embodiments have been described in relation to MoT networks, similar principles can be applied in relation to other networks and communication systems where high synchronized reliability is required. Therefore, although certain embodiments were described above by way of example with reference to certain example 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 herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

As used in this application, the term“circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable):

(i) a combination of analog and/or digital hardware circuit(s) with software/firmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.”

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus- readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory 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. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may 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.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1. An apparatus comprising means for:

receiving at least one message from at least one network entity at the apparatus via a first type radio link;

providing feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus;

receiving an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link; and

determining whether to execute the at least one message based on the indication.

2. An apparatus according to claim 1 , wherein means for determining whether to execute the at least one message based on the indication comprises means for receiving a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one message or the indication not to execute the at least one first message.

3. An apparatus according to claim 1 or claim 2, wherein means for determining whether to execute the at least one message based on the indication comprises means for determining to execute the at least one first message if the indication is not received at the user device after a given time period.

4. An apparatus according to any of claims 1 to 3, comprising means for storing the at least one message in a first layer; and

on determining to execute the at least one first message, forwarding the at least one first message to a higher layer.

5. An apparatus according to claim 4, wherein the first layer is a service data adaptation protocol layer and the higher layer is an application layer.

6. An apparatus according to claim 4, wherein the first layer is a medium access control layer and the higher layer is a radio link control layer.

7. An apparatus according to any of claims 1 to 6, wherein the apparatus is a user device of a group of user devices and the at least one message is one of a set of messages that the at least one network entity sends to each user device of the group of user devices.

8. An apparatus according to claim 7, wherein the indication comprises an indication of whether or not each of the group of user devices has received one of the set of message from the at least one network entity.

9. An apparatus, said apparatus comprising means for:

providing one of a set of messages to each user device of a group of user devices, via first type radio links;

receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device;

determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information; and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

10. An apparatus according to claim 9, wherein the first type radio links comprise a radio link common to each of the group of user devices.

11. An apparatus according to claim 9, wherein each first type radio link has an independent value for reliability.

12. An apparatus according to any of claims 9 to 11 , wherein the second type radio links comprise a radio link common to each of the group of user devices.

13. An apparatus according to any of claims 9 to 11 , wherein each second type radio link has an independent value for reliability.

14. An apparatus according to any of claims 9 to 13, comprising means for determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if so, providing the indication to each of the group of user devices to execute the one of the set of messages.

15. An apparatus according to any of claims 9 to 13, comprising means for determining, based on the feedback information, whether the one of the set of messages has been received at each of the group of devices and, if not, providing the indication to each of the group of user devices, to not execute the one of the set of messages.

16. An apparatus according to any of claims 9 to 15, comprising means for, if the feedback information indicates that the one of the set of message has not been received at each of the group of user devices, providing the one of the set of messages to at least one of the group of user devices again and receiving feedback information from the at least one user device indicating whether the one of the set of messages has been received at that user device.

17. An apparatus according to any of claims 9 to 16 comprising means for receiving from a network entity an indication of the set of messages, a set of user devices comprising the group of user devices to whom the messages are addressed and a synchronised reliability value with which the messages are to be sent.

18. An apparatus according to claim 17, comprising means for providing an indication to the network entity of whether the set of messages was received by the group of user devices with the synchronised reliability value.

19. An apparatus according to claim 17 or claim 18, wherein the network entity is an application function or a core network function.

20. An apparatus according to any of claims 9 to 19, wherein the set of messages is transmitted by one or more protocol data unit sessions and comprising means for accessing and detecting the set of messages for the group of user devices carried by the one or more protocol data unit sessions and transmitting the set of messages to the group of user devices via the first type radio links.

21. An apparatus according to any preceding claim, wherein the feedback information comprises an explicit acknowledgement/negative acknowledgment, ACK/NACK, message.

22. An apparatus according to any preceding claim, wherein the feedback information is implicit.

23. A method comprising:

receiving at least one message from at least one network entity at an apparatus via a first type radio link;

24. A method according to claim 23, wherein determining whether to execute the at least one message based on the indication comprises receiving a further message from the at least one network entity, wherein the further message comprises the indication to execute the at least one message or the indication not to execute the at least one first message.

25. A method according to claim 23 or claim 24, wherein determining whether to execute the at least one message based on the indication comprises determining to execute the at least one first message if the indication is not received at the user device after a given time period.

26. A method according to any of claims 23 to 25, wherein the apparatus is a user device of a group of user devices and the at least one message is one of a set of messages that the at least one network entity sends to each user device of the group of user devices.

27. A method according to claim 26, wherein the indication comprises an indication of whether or not each of the group of user devices has received one of the set of message from the at least one network entity.

28. A method comprising

receiving feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device; determining whether each user device of the group of user devices has received the one of the set of messages based on the feedback information; and providing, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

29. An apparatus comprising: at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive at least one message from at least one network entity at an apparatus via a first type radio link;

provide feedback to the at least one network entity indicating whether the at least one message has been received at the apparatus;

receive an indication at the apparatus from the at least one network entity, via a second type radio link, wherein the first type radio link has a lower reliability than a reliability of the second type radio link; and

determine whether to execute the at least one message based on the indication.

30. An apparatus comprising: at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to:

provide one of a set of messages to each user device of a group of user devices, via first type radio links;

receive feedback information from each user device of the group of user devices indicating whether the one of the set of messages sent to one user device has been received at the one user device;

determine whether each user device of the group of user devices has received the one of the set of messages based on the feedback information; and

provide, based on the determination, an indication to each of the group of user devices via second type radio links of whether to execute the one of the set of messages, wherein the first type radio links have a reliability less than a reliability of the second type radio links.

31. A computer readable medium comprising program instructions for causing an apparatus to perform at least the following:

32. A computer readable medium comprising program instructions for causing an apparatus to perform at least the following: