Method(s) for detecting a failure in a slot-based random access procedure of a wireless device in a communication network

Abstract

A method for detecting a failure in a slot-based random access procedure of a wireless device (14a, 14b, 14c; 14), preferably an ambient Internet of Things (IoT) device, in a communication network (10), the method (100) comprising: - Transmitting, by the wireless device (14a, 14b, 14c; 14), a first message of the random access procedure to a node (12) of the communication network (10), wherein the first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the communication network (10), preferably for requesting transmission resources from the node (12); and - Detecting, by the wireless device (14a, 14b, 14c; 14), a failure of the random access procedure, if no response to the first message is received by the wireless device (14a, 14b, 14c; 14), within a period represented by a defined number of slots.

Description

[0001] R. 416158

[0002] - 1 -

[0003] Specification

[0004] Title

[0005] Method(s) for detecting a failure in a slot-based random access procedure of a wireless device in a communication network

[0006] The invention concerns two corresponding methods for detecting a failure in a slot-based random access procedure of a wireless device, preferably an ambient Internet of Things (loT) device, in a communication network. Further, the invention concerns a wireless device, preferably an ambient loT device, a node, a computer program and a non-transitory computer readable medium.

[0007] Background

[0008] The state of the art in ambient loT devices, as currently studied by 3GPP, encompasses low-complexity, low-energy demanding wireless devices designed for various use-cases, such as inventory management, localization, and sensor data exchange within indoor and outdoor environments. These wireless devices are categorized into three main groups, each with different power consumption and transmission characteristics.

[0009] Type 1 devices have a peak power consumption of approximately 1 pW, comprise an energy storage, and have an initial sampling frequency offset (SFO) of up to 10X ppm. They do not have amplification in the device for either downlink (DL) or uplink (UL) transmission, and their UL transmission is based on backscattering an externally provided carrier wave.

[0010] Type 2a and Type 2b devices have peak power consumption of a few hundred pW, comprise an energy storage, and have an initial SFO of up to 10X ppm. Both types have amplification for DL and / or UL transmission, with Type 2a devices generating UL transmissions by backscattering externally provided carrier waves and Type 2b devices generating UL transmission internally. R. 416158

[0011] - 2 -

[0012] The ambient loT device may be configured to directly and bidirectionally communicate with a user equipment or a base station. The ambient loT device may also be configured to indirectly and bidirectionally communicate with a base station via at least one intermediate node, e.g., a user equipment (UE) or a reader or a relay.

[0013] The ambient loT device may also be configured for receiving downlink transmissions directly from a base station, and for receiving uplinks transmissions to the base station via at least one assisting node. The ambient loT device may alternatively be configured for receiving downlink transmission from the base stations via at least one assisting node, and for transmitting uplinks transmissions directly to the base station.

[0014] The random access procedure for these ambient loT devices may be based on a slotted ALOHA Medium Access (MAC) protocol, where devices access the channel only at the start of a time slot when triggered by the network. In the event of a collision, a resolution mechanism is required to address the simultaneous channel access by multiple ambient loT devices.

[0015] The random access procedure for ambient loT devices can be categorized based on the number of message exchanges and the approach to contention resolution: The procedure may be classified as two-step, three-step, or four-step, depending on the specific sequence of message exchanges involved in initiating and completing the random access process. Additionally, the procedure may be categorized as contention-based or contention-free, based on whether specific mechanisms are employed to mitigate contention and resolve collisions during channel access.

[0016] In conventional wireless networks with random access transmission, UEs transmit a random access preamble via the uplink random access channel. The network responds with a random access response. The U Es respond with a contention resolution identifier (CRID) to be identified by the network. The network then grants the channel to a specified UE based on resources and priority, while other UEs attempt to access the channel at a later random time. R. 416158

[0017] - 3 -

[0018] When an ambient loT device is triggered by the network or a reader, it initiates the random access procedure. During this process, messages exchanged between ambient loT devices and readers may be susceptible to loss due to collisions or poor channel conditions, highlighting the need for the detection of message failures and the implementation of a recovery procedure.

[0019] Disclosure of the invention

[0020] According to a first aspect, there is provided a method for detecting a failure in a slot-based random access procedure of a wireless device, preferably an ambient Internet of Things (loT) device, in a communication network.

[0021] The method according to the first aspect comprises:

[0022] Transmitting, by the wireless device, a first message of the random access procedure to a node of the communication network, wherein the first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the network, preferably for requesting transmission resources from the node; and

[0023] Detecting, by the wireless device, a failure of the random access procedure, if no response to the first message is received by the wireless device, within a period represented by a defined number of slots.

[0024] The method according to the first aspect can be understood as a method for wireless communications, specifically of operating the wireless device, preferably the ambient loT device, of the communication network.

[0025] According to a second aspect, there is provided a method for detecting a failure in a slot-based random access procedure of a wireless device, preferably an ambient Internet of Things (loT) device, in a communication network.

[0026] The method according to the second aspect comprises:

[0027] Receiving, by a node of the communication network, a first message of the random access procedure transmitted from the wireless device, wherein the first message comprises a random value and / or a device identification information for requesting access to a transmission medium R. 416158

[0028] - 4 - of the network, preferably for requesting transmission resources from the node;

[0029] Transmitting, by the node, a second message of the random access procedure in response to receiving the first message, wherein the second message comprises o the random value and / or the device identification information comprised by the first message and / or o a resource information about transmission resources allocated for the wireless device; and

[0030] Detecting, by the node, a failure of the random access procedure, if no response to the second message is received by the node within a period represented by a defined number of slots.

[0031] The method according to the second aspect can be understood as a method for communications, specifically of operating the node of the communication network.

[0032] According to a third aspect, there is provided a wireless device, preferably an ambient loT device, of a communication network. The wireless device is configured to execute the method according to the first aspect, or its embodiments.

[0033] According to a fourth aspect, there is provided a node, preferably a radio node, of a communication network. The node is configured to execute the method according to the second aspect, or its embodiments.

[0034] According to a fifth aspect, there is provided a computer program comprising machine-readable instructions to cause the wireless device as defined by the third aspect to execute the method according the first aspect, and / or its embodiments, and / or the node as defined by the fourth aspect to execute the method according the second aspect, and / or its embodiments.

[0035] According to a sixth aspect, there is provided a non-transitory computer readable medium having stored thereon the computer program as defined by the sixth aspect. R. 416158

[0036] - 5 -

[0037] The communication network may comprise a wireless network and a core network. The communication network may be configured as a cellular network, preferably according to 3GPP specifications, e.g., according to 3GPP release 18 or beyond, or as a wireless Local Area Network (LAN), preferably according to IEEE specifications. The communication network comprises at least the wireless device and the node.

[0038] The wireless device may be configured as a low-energy or low-power device. The wireless device may have a peak power consumption of less than 1 mW, preferably less than 500 pW, specifically less than 100 pW, according to an embodiment, less than 10 pW, e.g., approximately 1 pW.

[0039] The wireless device is preferably configured for energy harvesting, thus exploiting ambient energy sources, e.g., radio waves, thermal radiation, mechanical vibrations etc. as power supply. The wireless device may or may not comprise an energy storage, e.g., a battery.

[0040] Specifically, the wireless device is different from a Reduced Capability (Redcap) device, a narrow band loT (NB-loT) device, a device for enhanced machine-type communication (eMTC), e.g., due to its lower hardware complexity and / or lower costs, and / or smaller form factors. Additionally, a communication between the wireless device and the node may not be controlled by a Radio Resource Control (RRC) layer. Particularly, a Hybrid Automated Repeat Request (HARQ) procedure may not be deployed or deployable for the communication between the wireless device and the node.

[0041] The wireless device may be arranged on or part of an environmental sensor, e.g., deployed in smart buildings, industrial facilities, and urban infrastructure to enable environmental monitoring and control, a smart home device to enable remote monitoring and control of home environments for energy efficiency, security, and convenience, a wearable health and / or fitness tracker to enable personal health and fitness tracking, as well as remote patient monitoring in healthcare applications, R. 416158

[0042] - 6 - an asset tracking device to enable monitoring the location and status of assets, vehicles, and inventory in logistics, transportation, and supply chain management applications, an industrial loT sensor and / or actuator to enable monitoring and controlling machinery, equipment, and processes, a smart agriculture device to enable optimizing resource usage and improving crop yields, a smart city infrastructure unit to enable smart street lighting, traffic monitoring, waste management, public safety, and environmental monitoring.

[0043] The node of the communication network may be a radio or wireless node, or a core network node. The radio node may be a base station or a user equipment, e.g., configured as a reader for ambient loT devices, or a relay or an integrated access and backhaul (IAB).

[0044] The random access procedure preferably comprises at least the transmission of the first message of the random access procedure from the wireless device to the node and the transmission of the second message of the random access procedure from the node to the wireless device.

[0045] The first message may comprise or consist of the random access preamble. The random access preamble may comprise a random number and / or a device identification information.

[0046] The second message may comprise of consist of the random access response. The random access response may be an echo of the random number and / or the device identification information comprised by the random access preamble.

[0047] Messages of the random access procedure transmitted between the node and the wireless device, i.e., messages transmitted from the wireless device and received by the node and / or messages transmitted from the node and received by the wireless device, may either be transmitted directly, specifically, on the physical random access channel (PRACH), or indirectly via an intermediate or assisting node of the communication network. As an example, a message received by the wireless device may be transmitted from a core node of the R. 416158

[0048] - 7 - communication network via a radio node, e.g., a base station, of the communication network, to the wireless device, and vice versa.

[0049] The failure of the random access procedure may be a loss of one of the messages of the random access procedure of the wireless device. In a three or four step random access procedure, a first message of the random access procedure transmitted from the wireless device to the node and / or a second message of the random access procedure transmitted from the node to the wireless device and / or a third message of the random access procedure transmitted from the wireless device to the node may be lost. In a two step random access procedure, a first message of the random access procedure transmitted from the wireless device to the node and / or a second message of the random access procedure transmitted from the node to the wireless device may be lost. The failure of the random access procedure may also be a loss of a possible negative acknowledgement (NACK) transmitted in response to a failed transmission of the second message and / or the third message.

[0050] The detection of the failure of the random access procedure is based on not receiving an expected response message to a transmitted message of the random access procedure within a period represented by a defined number of slots. More precisely, the period corresponds to a duration a slot times multiplied with a natural number. The period may be one slot or N slots corresponding to one round of random access channel contention. The number N of slots defining a contention round of the random access procedure may be configured by the network or a reader node. The period may correspond to the number of slots of the current or next random channel access contention round. The period may be set by the node as a time or counter or duration of a scheduled time slot for receiving the third message.

[0051] The proposed solution effectively addresses the challenge of detecting failure of transmissions in a slot-based random access procedure of a wireless device. By allowing for a fast and efficient detection of failed transmissions, recovery steps may be initiated early, thereby preventing potential resource wastage and enhancing energy efficiency. This is especially beneficial for low-power or low- energy wireless devices, such as ambient loT devices, where resources must be managed meticulously. R. 416158

[0052] - 8 -

[0053] According to an embodiment of the first aspect, the method further comprises: Prior to transmitting the first message, receiving, by the node, a trigger message transmitted from the node or a further node of the communication network for triggering the random access procedure, wherein the first message is transmitted in response to receiving the trigger message.

[0054] Correspondingly, according to an embodiment of the second aspect, the method further comprises:

[0055] Prior to receiving the first message, transmitting, by the node, a trigger message to the wireless device for triggering the random access procedure.

[0056] The further node may be a core network node or a radio node, e.g., a base station or a user equipment. The trigger message may part of a paging message transmitted over a paging channel of the communication network. This allows for an efficient and coordinated initiation of the random access procedure, thus reducing collisions and contention with other devices attempting to access the network.

[0057] According to an embodiment of the first aspect, the method further comprises: Transmitting, by the wireless device, a further first message of the random access procedure to the node based on the detected failure, wherein the further first message comprises the random value or a further random value and / or the device identification information for requesting access to the transmission medium of the network, preferably for requesting transmission resources from the node.

[0058] In other words, for detecting a loss of the first message or the second message, a counter or timer may be set by the wireless device for receiving a response or feedback to the transmission of the first message, e.g., information about winning a contention for accessing the transmission medium, specifically the random value and / or the device identification information as comprised by the first message. If the timer or counter reaches a defined value corresponding to the defined number of slots, the further first message is transmitted. Here the defined number of slots may also be represented by a limited time window defined as a or multiple rounds of random channel access contentions. Preferably, the further first message is transmitted if no feedback or response is received within the time R. 416158

[0059] - 9 - window. I.e., the wireless device may be configured to wait for a limited time, e.g., for a set of slots defined as a round, and try again, or to immediately repeat the first message after a time window depending on a timer or counter reaches a threshold defined by a defined number of slots. A configuration for a number of slots to wait or a number of rounds to wait may be based on a configuration received from the network e.g., the core network, or a base station or a reader or configured by higher layers.

[0060] The transmission of the further first message may correspond to a retransmission of the first message or to a transmission with a new random value. Here, the further first message may additionally or alternatively comprise the device identification information. This enables proactive recovery from detected failures in the random access procedure, allowing the wireless device to adapt and potentially avoid the same collision or contention, thereby improving overall efficiency and reliability.

[0061] According to an embodiment of the first aspect, the method further comprises: Receiving, by the wireless device, a second message transmitted from the node in response to receiving the first message and / or the further first message, wherein the second message comprises o the random value and / or the device identification information comprised by the first and / or the further first message and / or o a resource information about transmission resources allocated for the wireless device.

[0062] The second message may the random access response. The second message may comprise an echo of the random number and / or the device identification information. The second message may additionally or alternatively indicate transmission resources of the network allocated for a transmission or a or multiple retransmission(s) of the wireless device. The resource information may indicate, e.g., a slot or a set of slots allocated for a transmission of the wireless device. Further, the second message may comprise control information. This allows for efficient signaling the wireless device to continue with step three of a three / four step random access procedure or to start with payload transmission in a two step random access procedure. R. 416158

[0063] - 10 -

[0064] According to an embodiment of the first aspect, the method further comprises: Transmitting, by the wireless device, in response to receiving the second message, a third message to the node, preferably using the allocated transmission resources, wherein the third message comprises a / the device identification information and / or data using the allocated transmission resources.

[0065] The third message may be a third message of the random access procedure, or a third message transmitted after successful completion of the random access procedure, i.e., after successfully accessing the transmission medium or channel. The third message preferably (only) comprises the device identification in case the first message does not comprise the device identification. The third message may also be a payload transmission. This allows the wireless device to effectively utilize the allocated transmission resources by transmitting data or device identification information.

[0066] According to an embodiment of the first aspect, the method further comprises: Receiving, by the wireless device, a further second message transmitted from the node, wherein the further second message comprises o the random value and / or the device identification information comprised by the first and / or the further first message, and / or o a resource information about the or alternative transmission resources allocated for the wireless device, and / or o a negative acknowledgment for not receiving a response to the second message within a further period represented by a further defined number of slots; and

[0067] Retransmitting, by the wireless device, the third message to the node in response to receiving the further second message, preferably using the resources indicated by the resource information of the further second message.

[0068] The further second message may be transmitted by the node in case no response to the second message is received by the node within the further period. The further period (the node is waiting for a response) may be different from or equal to the period (the wireless device is waiting for a response). Receiving the further second message by the wireless device can be understood as an implicit acknowledgement of the node for not receiving the third message. R. 416158

[0069] - 11 -

[0070] In case the further second message comprises the negative acknowledgement, the negative acknowledgement is explicit. This enables the wireless device to respond effectively to potential communication failures by retransmitting the third message, ensuring robustness and reliability in the random access procedure.

[0071] According to an embodiment of the second aspect, the method further comprises:

[0072] Receiving, by the node, a further first message of the random access procedure after transmission of the second message procedure, wherein the further first message comprises o the or a further random value and / or o the device identification information for requesting transmission resources from the node; and

[0073] Detecting, by the node, the failure of the random access procedure based on the receiving of the further first message.

[0074] Based on receiving a further first message, specifically instead of receiving a third message, a loss of the second message may be detected by the node. This represents an additional or alternative option to effectively detect a failure of the random access procedure.

[0075] According to an embodiment of the second aspect, the method further comprises:

[0076] Transmitting, by the node, a further second message of the random access procedure in response to the detected failure of the random access procedure, wherein the further second message comprises o the random value and / or the device identification information comprised by the first message, and / or o a resource information about the or alternative transmission resources allocated for the wireless device, and / or o a negative acknowledgment for not receiving a response to the second message within the period represented by the defined number of slots.

[0077] Preferably, in case of a loss of the second or third message, the node may be configured to repeat the same second message to let the selected wireless device start the transmission on the scheduled time slot. If the scheduled time R. 416158

[0078] - 12 - slot has already passed, then a new scheduling may be included in the further second message. Additionally or alternatively, the negative acknowledgement is transmitted to the wireless device. Successful transmission of the third message is crucial as it signifies that the wireless device has successfully gained access and has been identified within the random access procedure.

[0079] In a two step random access procedure, a response to the second message may be one or multiple messages comprising data or payload. Correspondingly, in a four step random access procedure, a response to the second message may be one or multiple messages comprising data or payload. Here, the one or multiple messages are transmitted, by the wireless device, to the node after successful completion of the random access procedure, i.e., after successfully accessing the channel.

[0080] If the one or multiple message(s) comprising data or payload are not received, by the node, in the corresponding slots allocated for the transmission(s), a failure will be detected by the node. Upon detection of the failure of the transmission of the one or multiple message(s) comprising data or payload, the detected failure may be indicated to the wireless device. For the indication of the detected failure, a message containing a negative acknowledgement may be transmitted from the node to the wireless device. Additionally, or alternatively, new transmission resources may be scheduled, by the node, for the wireless device, preferably for one or multiple retransmissions of the failed transmission(s) and / or for transmissions of further messages. According to an embodiment, the detected failure may be indicated, by the node, utilizing a single bit signaled to the wireless device.

[0081] In other words, it is proposed that if the third message is not received by the node within a round or the defined period using a timer or counter or on a scheduled time slot for the third message, a negative acknowledgment is sent by the node to the wireless device to trigger retransmission of the third message. Additionally or alternatively, a new scheduled time for the third message may be sent by the node. As a further alternative, the transmission of the second message may be repeated, optionally including all additional information already transmitted with the second message. This allows to implicitly or explicitly signal a loss of the second or third message to the wireless device. R. 416158

[0082] - 13 -

[0083] According to an embodiment of the second aspect, the method further comprises:

[0084] Detecting, by the node, a further failure of the random access procedure, if no response to the further second message is received by the node within a further period represented by a further defined number of slots; and

[0085] Retransmitting, by the node, the further second message, preferably with a specified periodicity and / or for a specified plurality of times.

[0086] Preferably, the further second message comprising the negative acknowledgement is retransmitted. In other words, in case a negative acknowledgement for not receiving a response to the second message is lost, retransmission of the third message is expected by the node, wherein reception of further messages from the node is awaited by the wireless device, e.g., containing control information as scheduling information for payload transmission. To get out of this situation, retransmission of the further second message comprising the NACK should be carried out several times in a specific period by the node. Additionally or alternatively, the wireless device may be configured to stay idle till control information for payload transmission is delivered.

[0087] The periodicity or specified plurality of retransmissions may depend on an upcoming traffic and / or access demand in the communication network, and / or a buffer status report from at least one other wireless device, and / or be fixed and different for specific type of wireless devices, e.g., ambient loT device categories type 1 , 2a, 2b, and / or be fixed for all types of wireless devices.

[0088] This allows to enhance the chances for the wireless device to successfully access the transmission medium.

[0089] According to an embodiment of the second aspect, the method further comprises:

[0090] Receiving, by the node, a third message transmitted from the wireless device, wherein the third message comprises a / the device identification R. 416158

[0091] - 14 - information and / or data transmitted from the wireless device using the allocated transmission resources.

[0092] This allows for successfully terminating the random access procedure.

[0093] According to an embodiment of the second aspect, the method further comprises:

[0094] Transmitting, by the node, in response to the detected failure and / or the detected further failure, a failure information to a further node of the communication network, wherein the failure information comprises the device identification information and, optionally, information about the detected failure and / or the detected further failure, e.g., a type or category of the failure.

[0095] The failure information may be transmitted to a node of a core network of the communication system.

[0096] In other words, due to blockage, low energy level, hardware impairments or any other reason, transmissions between the wireless device and the node may fail, specifically multiple times. The failure information is preferably used for reporting such a failure, e.g., a non-operational wireless device to the core network. The failure information may be comprised by a failure message transmitted via a wireless or wired channel of the communication network. The failure message may contain an identifier of the wireless device, and optionally, a type or category of the failure or impairment.

[0097] Preferably, based on the transmitted failure information, corresponding wireless devices are excluded from subsequent paging phases by other nodes, e.g., readers of wireless devices, of the communication network. The communication network, specifically the core network, may utilize the failure information for applications like “maintenance of ambient loT devices”. This allows to increase the efficiency of the random access procedure also for other nodes of the communication network by refraining from spending resources on non- operational wireless devices. Further, this allows to initiate proceedings to adapt channel conditions or device settings to avoid future failures of the random access procedure of the wireless device. R. 416158

[0098] - 15 -

[0099] According to an embodiment of the second aspect, the method further comprises:

[0100] Transmitting, by the node, in response to the detected failure and / or the detected further failure, o a trigger message to a further wireless device of the communication network for triggering the random access procedure of the further wireless device and / or o a second message of a random access procedure of a further wireless device to the further wireless device.

[0101] The second message may be transmitted to the further wireless device if a first message of the random access procedure of the further wireless device has already been received by the node. The further wireless device may have initially lost a contention for accessing the transmission medium against the wireless device.

[0102] In other words, independent from whether the random access procedure comprises the transmission of two, three or four messages, if a transmission of the message from the node to the wireless device fails for several times or rounds, instead of repeating transmission of the same second message multiple times, unfavorable channel conditions may be assumed by the node. In this case, another wireless device of the communication network may be selected by the node. In particular, the failed or lost message may be regenerated with new content for e.g., a new selected random value or identifier or new selected device ID to avoid wastage of resource such as energy consumption of competing wireless devices.

[0103] According to a further aspect of the invention, there is provided a (wireless) communication network comprising at least the wireless device and the node.

[0104] According to a further aspect of the invention, there is provided a method of operating the communication network. The method of operating the communication network comprises the steps of the method according to the first aspect, or its embodiments, and the steps of the method according to the second aspect, or its embodiments. R. 416158

[0105] - 16 -

[0106] The non-transitory computer readable medium is preferably configured to store the computer program to be executed by a processor of the first LAN element and / or the second LAN element and / or the communication network. The non- transitory computer readable media may include RAM, ROM, EEPROM, and any other non-volatile storage device.

[0107] Description of the figures

[0108] Exemplary embodiments of the present invention are depicted in the figures, which are not to be construed as limiting the claims, and are explained in greater detail below.

[0109] Fig. 1 schematically illustrates a communication network according to an embodiment of the invention; and

[0110] Fig. 2A,B schematically illustrate two methods according to embodiments of the invention.

[0111] Fig. 1 schematically illustrates a communication network 10 according to an aspect of the invention. The communication network 10 is configured as a cellular communication network 10, preferably according to 3GPP specifications. The communication network 10 may comprise a core network and a wireless network.

[0112] The communication network 10 comprises a radio node 12, configured as a user equipment 12, or a reader 12 for an ambient Internet of Things (loT) device, or a relay node acting as a reader, and a plurality of wireless devices 14a, 14b, 14c, preferably configured as ambient loT devices 14a, 14b, 14c, specifically according to 3GPP specifications. The wireless devices 14a, 14b, 14c are collectively represented by reference sign 14. The communication network 10 further comprises a radio node 16 configured as a base station 16.

[0113] For requesting access to a transmission medium of the communication network 10, the wireless devices 14 are configured to perform a method for initiating a preferably slot-based random access procedure. Here, the random access procedure may be based on a slotted ALOHA random access MAC protocol. I.e., the wireless devices 14 are configured to begin a transmission only at the R. 416158

[0114] - 17 - beginning of a slot. The length of the slot preferably equals the sum of a packet transmission time and a maximum propagation delay in the network to ensure that both transmission and reception of a data packet can be completed within one slot.

[0115] The random access procedure may be established between the respective wireless device 14a, 14b, 14c and the reader 12, or between the respective wireless device 14a, 14b, 14c and the base station 16. For the latter case, transmission between the wireless devices 14 and the base station 16 may be routed or relayed via the reader 12.

[0116] According to an alternative embodiment, the base station 16 may be configured as a reader for the wireless devices 14. Consequently, messages of the random access procedure are transmitted directly between the base station 16 and the wireless devices 14a, 14b, 14c (i.e., without routing them via the radio node 12).

[0117] The wireless devices 14 are configured for detecting a failure in the slot-based random access procedure of the respective wireless device 14 by performing the method according to the first aspect of the invention, and / or its embodiments, as further described in Fig. 2A.

[0118] The node 12 and / or the node 16 are configured for detecting a failure in the slotbased random access procedure of the wireless devices 14 by performing the method according to the second aspect of the invention, and / or its embodiments, as further described in Fig. 2B.

[0119] Fig. 2 schematically illustrates two methods according to embodiments of the invention.

[0120] Fig. 2A schematically illustrates a method 100 for detecting a failure in a slotbased random access procedure of a wireless device 14a, preferably an ambient Internet of Things (loT) device 14a, e.g., according to Fig. 1 , in a communication network according to the first aspect of the invention.

[0121] The method 100 comprises an optional step 110 of receiving, by the wireless device 14a, a trigger message transmitted from a node or a further node of the communication network for triggering the random access procedure. R. 416158

[0122] - 18 -

[0123] The method 100 comprises a step 120 of transmitting, by the wireless device 14a, a first message of the random access procedure to a node of the communication network. The first message is preferably transmitted in response to receiving the trigger message. The first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the network, preferably for requesting transmission resources from the node.

[0124] The method 100 comprises a step 130 of detecting, by the wireless device 14a, a failure of the random access procedure, if no response to the first message is received by the wireless device 14a, within a period represented by a defined number of slots.

[0125] The method 100 comprises an optional step 140 of transmitting, by the wireless device 14a, a further first message of the random access procedure to the node based on the detected failure. The further first message comprises the or a further random value and / or the device identification information for requesting access to a transmission medium of the network, preferably for requesting transmission resources from the node.

[0126] Fig. 2B schematically illustrates a method 200 for detecting a failure in a slotbased random access procedure of a wireless device, preferably an ambient Internet of Things (loT) device, in a communication network according to the second aspect of the invention.

[0127] The method 200 comprises an optional step 210 of transmitting, by a node 12 of the communication network, e.g., the reader 12 according to Fig. 1 , a trigger message to the wireless device for triggering the random access procedure.

[0128] The method 200 comprises a step 220 of receiving, by the node 12, a first message of the random access procedure transmitted from the wireless device. The first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the network, preferably for requesting transmission resources from the node 12. R. 416158

[0129] - 19 -

[0130] The method 200 comprises a step 230 of transmitting, by the node 12, a second message of the random access procedure in response to receiving the first message. The second message comprises the random value and / or the device identification information comprised by the first message and / or a resource information about transmission resources allocated for the wireless device

[0131] The method 200 comprises a step 240 of detecting, by the node 12, a failure of the random access procedure, if no response to the second message is received by the node within a period represented by a defined number of slots.

[0132] The method 200 comprises an optional step 250 of transmitting, by the node 12, a further second message of the random access procedure in response to the detected failure of the random access procedure. The further second message comprises the random value and / or the device identification information comprised by the first message, and / or a resource information about the or alternative transmission resources allocated for the wireless device, and / or a negative acknowledgment for not receiving a response to the second message within the period represented by the defined number of slots.

[0133] The method 200 comprises an optional step 260 of transmitting, by the node 12, in response to the detected failure, a failure information to a further node of the communication network. The failure information comprises the device identification information and, optionally, information about the detected failure and / or the detected further failure, e.g., a type or category of the failure.

[0134] The method 200 comprises an optional step 270 of transmitting, by the node 12, in response to the detected failure, a trigger message to a further wireless device of the communication network for triggering the random access procedure of the further wireless device.

Claims

R. 416158- 20 -Claims1 . A method (100) for detecting a failure in a slot-based random access procedure of a wireless device (14a, 14b, 14c; 14), preferably an ambient Internet of Things (loT) device, in a communication network (10), the method (100) comprising:Transmitting (120), by the wireless device (14a, 14b, 14c; 14), a first message of the random access procedure to a node (12) of the communication network (10), wherein the first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the communication network (10), preferably for requesting transmission resources from the node (12); andDetecting (130), by the wireless device (14a, 14b, 14c; 14), a failure of the random access procedure, if no response to the first message is received by the wireless device (14a, 14b, 14c; 14), within a period represented by a defined number of slots.

2. The method (100) according to claim 1 , further comprising:Prior to transmitting (120) the first message, receiving (110), by the node (12), a trigger message transmitted from the node (12) or a further node (16) of the communication network (10) for triggering the random access procedure, wherein the first message is transmitted in response to receiving (110) the trigger message.

3. The method (100) according to claim 1 or 2, further comprising:Transmitting (140), by the wireless device (14a, 14b, 14c; 14), a further first message of the random access procedure to the node (12) based on the detected failure, wherein the further first message comprises the or a further random value and / or the device identification information for requesting access to the transmission medium of the communication network (10), preferably for requesting transmission resources from the node (12).R. 416158- 21 -4. The method (100) according to one of the preceding claims, further comprising:Receiving, by the wireless device (14a, 14b, 14c; 14), a second message transmitted from the node (12) in response to receiving the first message and / or the further first message, wherein the second message comprises o the random value and / or the device identification information comprised by the first and / or the further first message and / or o a resource information about transmission resources allocated for the wireless device (14a, 14b, 14c; 14).

5. The method (100) according to claim 4, further comprising:Transmitting, by the wireless device (14a, 14b, 14c; 14), in response to receiving the second message, a third message to the node (12), preferably using the allocated transmission resources, wherein the third message comprises a / the device identification information and / or data using the allocated transmission resources.

6. The method (100) according to claim 5, further comprising:Receiving, by the wireless device (14a, 14b, 14c; 14), a further second message transmitted from the node (12), wherein the further second message comprises o the random value and / or the device identification information comprised by the first and / or the further first message, and / or o a resource information about the or alternative transmission resources allocated for the wireless device (14a, 14b, 14c; 14), and / or o a negative acknowledgment for not receiving a response to the second message within a further period represented by a further defined number of slots; andRetransmitting, by the wireless device (14a, 14b, 14c; 14), the third message to the node (12) in response to receiving the further second message.R. 416158- 22 -7. A method (200) for detecting a failure in a slot-based random access procedure of a wireless device (14a, 14b, 14c; 14), preferably an ambient Internet of Things (loT) device, in a communication network (10), the method (200) comprising:Receiving (220), by a node (12) of the communication network (10), a first message of the random access procedure transmitted from the wireless device (14a, 14b, 14c; 14), wherein the first message comprises a random value and / or a device identification information for requesting access to a transmission medium of the communication network (10), preferably for requesting transmission resources from the node (12);Transmitting (230), by the node (12), a second message of the random access procedure in response to receiving the first message, wherein the second message comprises o the random value and / or the device identification information comprised by the first message and / or o a resource information about transmission resources allocated for the wireless device (14a, 14b, 14c; 14); andDetecting (240), by the node (12), a failure of the random access procedure, if no response to the second message is received by the node (12) within a period represented by a defined number of slots.

8. The method (200) according to claim 7, further comprisingPrior to receiving (220) the first message, transmitting (210), by the node (12), a trigger message to the wireless device (14a, 14b, 14c; 14) for triggering the random access procedure.

9. The method (200) according to claim 7 or 8, further comprising:Receiving, by the node (12), a further first message of the random access procedure after transmission of the second message procedure, wherein the further first message comprises o the or a further random value and / or o the device identification information for requesting transmission resources from the node (12); andDetecting, by the node (12), the failure of the random access procedure based on the receiving of the further first message.R. 416158- 23 -10. The method (200) according to one of claims 7 to 9, further comprising:Transmitting (250), by the node (12), a further second message of the random access procedure in response to the detected failure of the random access procedure, wherein the further second message comprises o the random value and / or the device identification information comprised by the first message, and / or o a resource information about the or alternative transmission resources allocated for the wireless device (14a, 14b, 14c; 14), and / or o a negative acknowledgment for not receiving a response to the second message within the period represented by the defined number of slots.11 . The method (200) according to claim 10, further comprising:Detecting, by the node (12), a further failure of the random access procedure, if no response to the further second message is received by the node (12) within a further period represented by a further defined number of slots; and Retransmitting, by the node (12), the further second message, preferably with a specified periodicity and / or for a specified plurality of times.

12. The method (200) according to one of claims 7 to 11 , further comprising:Receiving, by the node (12), a third message transmitted from the wireless device (14a, 14b, 14c; 14), wherein the third message comprises a / the device identification information and / or data transmitted from the wireless device (14a, 14b, 14c; 14) using the allocated transmission resources.

13. The method (200) according to one of claims 7 to 12, further comprising:Transmitting (260), by the node (12), in response to the detected failure and / or the detected further failure, a failure information to a further node (16) of the communication network (10), wherein the failure information comprises the device identificationR. 416158- 24 - information and, optionally, information about the detected failure and / or the detected further failure, e.g., a type or category of the failure.

14. The method (200) according to one of claims 7 to 13, further comprising:Transmitting (270), by the node (12), in response to the detected failure and / or the detected further failure, o a trigger message to a further wireless device (14a, 14b, 14c; 14) of the communication network (10) for triggering the random access procedure of the further wireless device (14a, 14b, 14c; 14), and / or o a second message of a random access procedure of a further wireless device to the further wireless device.

15. A wireless device (14a, 14b, 14c; 14), preferably an ambient Internet of Things (loT) device, of a communication network (10) configured to execute the method (100) according to one of claims 1 to 6.

16. A node (12) of a communication network (10) configured to execute the method (200) according to one of claims 7 to 14.

17. A computer program comprising machine-readable instructions to cause the wireless device (14a, 14b, 14c; 14) according to claim 15 to execute the method (100) according to one of claims 1 to 6, and / or the node (12) according to claim 16 to execute the method (200) according to one of claims 7 to 14.

18. A non-transitory computer readable medium having stored thereon the computer program according to claim 17.

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