Resource selection for contention-based random access

Abstract

A random access method can include an IoT reader node transmitting a first access occasion trigger for triggering, within a first sub-frame of an access frame, an IoT random access procedure between the IoT reader node and an IoT device. The method can include the IoT reader node transmitting, responsive to detection of a failure of the IoT random access procedure, a second access occasion trigger for triggering, within a second subframe of the access frame, the IoT random access procedure between the IoT reader node and the IoT device.

Description

Title: RESOURCE SELECTION FOR CONTENTION-BASED RANDOM ACCESSTECHNICAL FIELD

[0001] The example and non-limiting embodiments relate generally to contention-based random access (CBRA) random access procedures and, more particularly, to systems, devices and methods for resource selection CBRA.BRIEF DESCRIPTION OF PRIOR DEVELOPMENTS

[0002] Internet of Things (loT) technology allows or enables a collection of devices to communicate with each other, with other Internet enabled devices and / or with the cloud therefore creating a network of interrelated devices. Applications of loT can include smart vehicles, smart homes, smart healthcare, smart factories or smart cities among others. Artificial Intelligence of Things (AIoT) can be viewed as a combination of the loT and artificial intelligence (Al) technologies. AIoT devices are intelligent and networked devices.

[0003] The current disclosure addresses random access for loT devices and / or AIoT devices. In particular, embodiments described in this disclosure improve contention-based random access (CBRA) processes in loT and / or AIoT systems.SUMMARY OF THE INVENTION

[0004] The following summary is merely intended to be an example. The summary is not intended to limit the scope of the claims.

[0005] In accordance with one aspect, an apparatus can include at least one processor and at least one memory storing instructions that, when executed by the at least one processor, can cause the apparatus to transmit a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the apparatus and a device. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the device to select a start time, within the first sub-frame, for the transmission of the first response message. The instructions, when executed by the at least one processor, can cause the apparatus totransmit, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

[0006] According to another aspect, an apparatus can include at least one processor and at least one memory storing instructions that, when executed by the at least one processor, can cause the apparatus to receive, from an Internet of things (loT) reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the apparatus. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message. The instructions, when executed by the at least one processor, can cause the apparatus to receive, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the apparatus.

[0007] According to another aspect, a method can include transmitting, by an Internet of things (loT) reader node, a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the loT reader node and an loT device. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the loT device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the loT device to select a start time, within the first sub-frame, for the transmission of the first response message. The method can include transmitting, by the loT reader node, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the loT device.

[0008] According to another aspect, a method can include receiving, by an Internet of things (loT) device from an loT reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the loT device. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmissionof a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message. The method can include receiving, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the loT device.

[0009] According to another aspect, an apparatus can include means for transmitting a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the apparatus and a device. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the device to select a start time, within the first sub-frame, for the transmission of the first response message. The can include means for transmitting, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

[0010] According to another aspect, an apparatus can include means for receiving, from an Internet of things (loT) reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the apparatus. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message. The apparatus can include means for receiving, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the apparatus.

[0011] According to another aspect, a non-transitory computer readable medium can include program instructions that, when executed by an apparatus, cause the apparatus to transmit a first access occasion trigger for triggering an Internet of things (loT) randomaccess procedure between the apparatus and a device. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the device to select a start time, within the first sub-frame, for the transmission of the first response message. The program instructions, when executed by the apparatus, can cause the apparatus to transmit, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

[0012] According to another aspect, a non-transitory computer readable medium can include program instructions that, when executed by an apparatus, cause the apparatus to receive, from an Internet of things (loT) reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the apparatus. The first access occasion trigger can include at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message. The program instructions, when executed by the at least one processor, can cause the apparatus to receive, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second subframe of the access frame, the loT random access procedure between the loT reader node and the apparatus.

[0013] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are provided in subject matter of the dependent claims.BRIEF DESCRIPTION OF DRAWINGS

[0014] The foregoing aspects and other features are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0015] FIG. 1 is a block diagram of one possible and non-limiting example system in which the example embodiments may be practiced;

[0016] FIGS. 2A and 2B are flow diagrams depicting a 3-step and 2-step random access procedures, respectively, according to some example embodiments of the current disclosure;

[0017] FIGS. 3A and 3B are diagrams depicting different schemes 300A and 300B for handling or scheduling follow-up random access attempts in the time-domain when a collision or a random access failure occurs, according to some example embodiments of the current disclosure;

[0018] FIGS. 4A and 4B illustrate simulated performance data for the schemes depicted in FIGS. 3A and 3B, according to some example embodiments of the present disclosure;

[0019] FIG. 5 illustrates a flowchart of a random access method implemented at a first apparatus, according to some example embodiments of the current disclosure;

[0020] FIG. 6 illustrates a flowchart of a random access method implemented at a second apparatus, according to some example embodiments of the present disclosure;

[0021] FIGS. 7 A and 7B are two diagrams illustrating two configuration schemes of access frames, according to some example embodiments of the present disclosure;

[0022] FIG. 8 is a signaling diagram depicting a CBRA process, according to some example embodiments of the present disclosure; and

[0023] FIG. 9 is a signaling diagram depict another CBRA process, according to some example embodiments of the present disclosure.DETAILED DESCRIPTION

[0024] The following abbreviations that may be found in the specification and / or the drawing figures are defined as follows:3 GPP third generation partnership project5G fifth generation5GC 5G core networkAMF access and mobility management functionCU central unitDU distributed unit eNB (or eNodeB) evolved Node B (e.g., an LTE base station)EN-DC E-UTRA-NR dual connectivity en-gNB or En-gNB node providing NR user plane and control plane protocol terminations towards the UE, and acting as secondary node in EN-DCE-UTRA evolved universal terrestrial radio access, i.e., the LTE radio access technology gNB (or gNodeB) base station for 5G / NR, i.e., a node providing NR user plane and control plane protocol terminations towards the LTE, and connected via the NG interface to the 5GCI / F interfaceLTE long term evolutionMAC medium access controlMME mobility management entity ng or NG next generation ng-eNB or NG-eNB next generation eNBNR new radioN / W or NW networkPDCP packet data convergence protocolPHY physical layerRAN radio access networkRel releaseRLC radio link controlRRH remote radio headRRC radio resource controlRU radio unitRx receiverSDAP service data adaptation protocolSGW serving gatewaySMF session management functionTS technical specificationTx transmitterUE user equipment (e.g., a wireless, typically mobile device)UPF user plane function

[0025] Turning to FIG. 1, this figure shows a block diagram of one possible and nonlimiting example in which the examples may be practiced. A user equipment (UE) 110, radio access network (RAN) node 170, and network element(s) 190 are illustrated. Examples of network equipment, network device, or a network entity might be understood to include, at least part of, a transmission reception point or a cell or a gNB or node for example. In the example of FIG. 1, the user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140, comprising one of or both parts 140- 1 and / or 140-2, which may be implemented in a number of ways. The module 140 may be implemented in hardware as module 140-1, such as being implemented as part of the one or more processors 120. The module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with RAN node 170 via a wireless link 111.

[0026] The RAN node 170 in this example is a base station that provides access by wireless devices such as the UE 110 to the wireless network 100. The RAN node 170 may be, for example, a base station for 5G, also called New Radio (NR). In 5G, the RAN node 170 may be a NG-RAN node, which is defined as either a gNB or a ng-eNB. A gNB is a node providing NR user plane and control plane protocol terminations towards the UE, andconnected via the NG interface to a 5GC (such as, for example, the network element(s) 190). The ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC. The NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DUs) (gNB-DUs), of which DU 195 is shown. Note that the DU may include or be coupled to and control a radio unit (RU). The gNB-CU is a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the Fl interface connected with the gNB-DU. The Fl interface is illustrated as reference 198, although reference 198 also illustrates a link between remote elements of the RAN node 170 and centralized elements of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB-CU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface 198 connected with the gNB-CU. Note that the DU 195 is considered to include the transceiver 160, e.g., as part of a RU, but some examples of this may have the transceiver 160 as part of a separate RU, e.g., under control of and connected to the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station, for LTE (long term evolution), or any other suitable base station or node.

[0027] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / W I / F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor(s) 152, memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memory / memories and processor(s), and / or other hardware, but these are not shown.

[0028] The RAN node 170 includes a module 150, comprising one of or both parts 150-1 and / or 150-2, which may be implemented in a number of ways. The module 150 may be implemented in hardware as module 150-1, such as being implemented as part of the one or more processors 152. The module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, themodule 150 may be implemented as module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the RAN node 170 to perform one or more of the operations as described herein. Note that the functionality of the module 150 may be distributed, such as being distributed between the DU 195 and the CU 196, or be implemented solely in the DU 195.

[0029] The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 may communicate using, e.g., link 176. The link 176 may be wired or wireless or both and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0030] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 for gNB implementation for 5G, with the other elements of the RAN node 170 possibly being physically in a different location from the RRH / DU, and the one or more buses 157 could be implemented in part as, for example, fiber optic cable or other suitable network connection to connect the other elements (e.g., a central unit (CU), gNB-CU) of the RAN node 170 to the RRH / DU 195. Reference 198 also indicates those suitable network link(s).

[0031] It is noted that description herein indicates that “cells” perform functions, but it should be clear that equipment which forms the cell will perform the functions. The cell makes up part of a base station. That is, there can be multiple cells per base station. For example, there could be three cells for a single carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single base station’s coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and a base station may use multiple carriers. So if there are three 120 degree cells per carrier and two carriers, then the base station has a total of 6 cells.

[0032] The wireless network 100 may include a network element or elements 190 that may include core network functionality, and which provides connectivity via a link or links 181with a further network, such as a telephone network and / or a data communications network (e.g., the Internet). Such core network functionality for 5G may include access and mobility management function(s) (AMF(S)) and / or user plane functions (UPF(s)) and / or session management function(s) (SMF(s)). Such core network functionality for LTE may include MME (Mobility Management Entity) / SGW (Serving Gateway) functionality. These are merely exemplary functions that may be supported by the network element(s) 190, and note that both 5G and LTE functions might be supported. The RAN node 170 is coupled via a link 131 to a network element 190. The link 131 may be implemented as, e.g., an NG interface for 5G, or an SI interface for LTE, or other suitable interface for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / W I / F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the network element 190 to perform one or more operations.

[0033] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.

[0034] The computer readable memories 125, 155, and 171 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, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processors 120, 152,and 175 may be means for performing functions, such as controlling the UE 110, RAN node 170, and other functions as described herein.

[0035] In general, the various embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, tablets, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.

[0036] Referring now to FIGS. 2A and 2B, flow diagrams depicting, respectively, a 3-step contention-based random access (CBRA) procedure 200A and a 2-step CBRA procedure 200B are shown, according to some example embodiments of the current disclosure. The Internet of things (loT) systems and / or artificial intelligence of things (AIoT) systems can employ or provide two types of random-access procedures, which are denoted as 3-step CBRA procedure 200 A and 2-step CBRA procedure 200B. An loT reader node 202 can transmit or broadcast an access round trigger to signal to one or more loT devices 204 an access round. The loT reader node 202 can also be referred to herein as reader node or AIoT reader node. The loT device 204 can be referred to herein as device or AIoT device.

[0037] The loT device 204 can be configured or programmed to connect and exchange data with other devices and systems over the Internet. The loT device 204 can include a sensor, an actuator, a gadget, an appliance, a machine and / or some other piece of hardware that is programmed for certain applications and can transmit data over the internet or other communication networks. The loT device 204 can include at least one transceiver for transmitting and / or receiving data, at least one memory for storing data and / or executable, and at least one processor for executing instructions to process data and / or make decisions.

[0038] The loT reader node 202 can be configured to establish connectivity between loT devices 204 and the Internet or a communication network associated with the loT reader 202, such as wireless network 100. The loT reader node 202 can include UE 110, RAN node 170 and / or network element 190. The loT reader node 202 can include at least onetransceiver for transmitting and / or receiving data, at least one memory for storing data and / or executable, and at least one processor for executing instructions to process data and / or make decisions.

[0039] After transmitting the access round trigger, the loT reader node can transmit an access occasion trigger to signal the start of an access occasion and / or trigger a random access procedure. An access round can include one or more access occasions to give access to one or more loT devices 204. Upon receiving the access occasion trigger, the loT device 204 can transmit an loT message, e.g., loT Msgl, including an identifier to the loT reader node 204. In some implementations, when multiple loT devices 204 are seeking access to the network, each loT device 204 can transmit a respective loT message, e.g., a respective loT Msgl, including a corresponding identifier. Responsive to the Msgl received from one or more loT devices, the loT reader 202 can transmit an acknowledgment message, e.g., loT Msg2, including an identifier, e.g., corresponding or equal to an identifier received in a Msgl from a corresponding loT device 204. Upon receiving the loT Msg2, each loT device 204 can check whether the identifier in the loT Msg2 is the same as the identifier the loT device 204 transmitted in its loT Msgl . If both identifiers are equal, the loT device 204 is granted access to the network. If the identifiers are different, the loT device 204 can detect or determine a failure of the random access procedure or a contention.

[0040] In the 3 -step CBRA procedure 200 A, the loT device 204 can transmit another loT message, e.g., loT Msg3, to the loT reader node 202, responsive to receiving the loT Msg2 from the loT reader node 202. The loT Msg3 can include a device identifier (ID) of the loT device and / or upper layer data. The transmission of the loT Msg3 is not part of the 2-step CBRA procedure 200B. Another difference between the 3 -step CBRA procedure 200 A and the 2-step CBRA procedure 200B, is that the identifier included in the loT Msgl, and the loT Msg2, is a random ID, whereas in the 2-step CBRA procedure 200B, the loT device 204 can include its device ID and / or upper layer data in the loT Msgl and the loT reader node 202 can include one of the device IDs received from one of the loT devices 204 in the loT Msg2.

[0041] The loT reader node 204 can repeat the exchange of loT messages with loT devices 204 described above in multiple access occasions within a an access round. Also, the whole process can be repeated using multiple rounds within an inventory session, e.g., until alltargeted loT devices 204 to be triggered access the communication network associated with the loT reader node 202.

[0042] When a collision or contention occurs, e.g., at least one loT device 204 fails to get access to the network, the loT reader node can generate and transmit a new access occasion trigger, or a new access round trigger, to provide additional opportunities for the at least one loT device 204 to access the network. However, in conditions of high contention it is expected that many collisions will occur and therefore the number of wasted resources will increase with the access load, and so will the latency experienced when collecting the measurements of individual loT devices 204.

[0043] It is to be noted that the collision can be detected at the loT device 204 and / or at the loT reader. Various scenarios for collision detection are described in further detail below. Embodiments described herein enable or allow reduction or decrease of the impact of collision in 3-step CBRA and / or 2-step CBRA. Reducing the impact of collision can include reducing latency and / or reducing resource wastage.

[0044] FIGS. 3A and 3B show two different schemes 300A and 300B for handling or scheduling follow-up random access attempts in the time-domain when a collision or a random access failure occurs, according to some example embodiments of the current disclosure. In FIGS, 3 A and 3B, first attempt resources can be viewed as resources used, or available for use, in connection with the first access occasion. Sub-sequent attempt resources can be viewed as resources used, or available for use, when a sub-sequent access occasion is triggered upon the detection of a collision or failure of the random access process. In other words, a first attempt can refer to a first access occasion whereas a subsequent attempt can refer to the sub-sequent access triggered upon the detection of the collision or failure of the random access process during the first access occasion.

[0045] In the scheme 300A, first attempt resources or the first access occasion can be arranged in a first access frame, e.g., Frame 1, whereas the subsequent attempt resources or the sub-sequent access occasion are arranged in another access frame, e.g., Frame 2, that is subsequent or after the first access frame. In other words, according to scheme 300A, if a contention occurs in a first access frame the sub-sequent attempt will take place in another access frame, e.g., a second access frame that is after the first access frame.

[0046] According to scheme 300B, the first access occasion or the first random access attempt can occur in a first part, portion or sub-frame, e.g., sub-frame 1.1, of an access frame and any subsequent random access attempt, e.g., due to a detected collision or failure of the first attempt, can occur within a second part, portion or sub-frame, e.g., sub-frame 1.2, of the same access frame. The scheme 300B allows for reduced or lower latency compared to scheme 300A. In particular, by scheduling subsequent attempts within the same access frame, an loT device 2004 that failed to get access in the first access occasion will wait less time, e.g. compared to scheme 300A, before having another random access opportunity to connect to or access the communication network associated with the loT reader node 204. Also, the approach depicted in scheme 300B enables or allows for increased system throughput, as discussed in further detail below in relation to FIGS. 4A and 4B.

[0047] An access frame can be viewed as a group of one or more resources, e.g., time resources or time-frequency resources, or a group of one or more time periods allocated or available for a group of one or more access occasions. The duration of the access frame can be expressed or defined as a number of access slots that are eligible for reader-to-device (R2D) and / or device-to-reader (D2R) communications. The access frame can correspond to the acceptable time to receive a reply from the loT device 204 if no collisions occurs. In some implementations, access frames can be device specific.

[0048] FIGS. 4A and 4B illustrate simulated performance data for the schemes depicted in FIGS. 3A and 3B, according to some example embodiments of the present disclosure. The parameter N1 represents the size of the first sub-frame, e.g., in terms of time slots, whereas the size of access frames is set to be N = 40 in the conducted simulations. The plots in FIG. 4A represent the probability of successfully completing the random access procedure, without experiencing a collision with another device transmission, within a single access frame as a function of the Nl. The dashed-line curve represents the probability of success for scheme 300 A, whereas the continuous-line curve represents the probability of success for scheme 300B. The probability of success for scheme 300A is constant since no partitioning of the access frame is adopted in scheme 300A. The probability of success for scheme 300B increases until it reaches a maximum, e.g., at Nl = 25 and then decreases. The simulation results in FIG. 4A are obtained for N = 40 and the expected number of loT devices attempting to access the loT reader node 202 is K = 15.

[0049] FIG. 4B depicts throughput plots for schemes 300A and 300B as a function of K. The dashed-line curve represents the throughput for scheme 300 A, whereas the continuous-line curve represents the throughput for scheme 300B. In determining the throughput for scheme 300B, N1 is determined or optimized for each K value, whereas N = 40. In other words, N1 is selected based on the expected number of devices K attempting to access the loT reader node 202. The plots in FIG. 4A depict an increase in throughput for scheme 300B compared to scheme 300 A. The throughput here represents the number of devices succeeding to access the loT reader node 202.

[0050] It is to be noted that optimal or adequate partitioning of the access frame, or determining at least the size N1 of the first sub-frame depends on the number of expected loT devices K attempting to access the loT reader node 202 within the access frame. In other words, knowledge of the expected number K of loT devices 204 attempting to access the loT reader node 202 or a reliable estimate of K can help achieve optimal, near optimal or adequate portioning of the access frame and / or optimal or adequate size of the first subframe.

[0051] FIG. 5 illustrates a flowchart of a method 500 implemented at a first apparatus, according to some example embodiments of the current disclosure. The method 500 can be implemented by the loT reader node 202. In brief overview, the method 500 can include the first apparatus, e.g., loT reader node 202, transmitting a first access trigger for triggering, within a first sub-frame of an access frame, a random access procedure between the first apparatus and an loT device 204 (STEP 502). The method 500 can include the first apparatus transmitting, responsive to detection of a failure of the random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the random access procedure (STEP 504).

[0052] FIG. 6 illustrates a flowchart of a method 600 implemented at a second apparatus, according to some example embodiments of the present disclosure. The method 600 can be implemented by the loT device 204. In brief overview, the method 600 can include the second apparatus, e.g., loT device 204, receiving from the loT reader node 202 a first access trigger for triggering, within a first sub-frame of an access frame, a random access procedure between the loT reader node 202 and the second apparatus (STEP 602). The method 600 can include the second apparatus receiving, responsive to detection of a failureof the random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the random access procedure (STEP 604).

[0053] The methods 500 and 600 are discussed in further detail below, e.g., in relation to FIGS. 7A - 9. The methods 500 and 600 relate to a modified or enhanced random access procedure from the perspective of the loT reader node 202 and the loT device 204.

[0054] The method 500 can include configuring access frames. Configuring access frames can include at least one of determining total duration of each frame, determining and / or allocating, for each access frame, the corresponding resources, determining the partitioning of each access frame, e.g., number and size(s) of sub-frames in each access frame, or determining the arrangement of sub-frames. The configuration of the access frames can be performed by the communication network 100 associated with the loT reader node 202 or a respective network element, e.g., network element 190, by the loT reader node 202 or by both. For instance, the communication network and / or the loT reader node 202 can determine a duration of at least one sub-frame, e.g., the first sub-frame and / or second sub-frame, of the access frame based on at least one of (i) the number or expected number K of loT devices 204 attempting to access the loT reader node 202 or that that will respond to the first access occasion trigger, (ii) the number or expected number of loT devices 204 concurrently attempting to access one or more other loT reader nodes 204 or that will respond to concurrent access occasion triggers transmitted by one or more other loT reader nodes 204, or (iii) a contention-based ratio. In some implementations, the loT reader node can determine the contention-based ratio using measurements indicative of the overall activity related to loT or AIoT transmissions in a given time period.

[0055] In some implementations, the loT reader node 202 can receive information indicative of access frame configuration from the network, configure the access frame(s) and / or transmit configuration of the access frame(s) in an access round trigger. In some implementations, the loT reader node 202 may not transmit configuration of the access frame(s) to loT devices 204.

[0056] Referring now to FIGS. 7A and 7B, two configuration schemes 700A and 700B of access frames are shown, according to some example embodiments of the present disclosure. According to the configuration scheme 700A, the communication network orthe loT reader node 202 can configure sub-frames of each access frame to be arranged or organized sequentially one after the other with no sub-frame from another access frame in between. For instance, each access frame can be defined by a single time period and the corresponding sub-frames can be arranged sequentially within the single time period

[0057] The configuration scheme 700B depicts an interleaved arrangement of sub-frames from different access frames. For instance, sub-frames of an access frame can be interleaved with one or more sub-frames of another access frame. For example, in FIG 7B, the first and second sub-frames 1.1 and 1.2 of a first frame, e.g., Frame 1, are separated by sub-frame 0.2 from Frame 0 and sub-frame 2.1 from Frame 2. Since the sub-sequent attempts can only occur after the collision is detected, then it is expected that there will be some time gap needed until the sub-sequent attempts can be triggered, e.g., to identify or find the next available resource(s). Therefore, the interleaving of the second partition or second sub-frame with one or more sub-frames of one or more other access frames would be more suitable

[0058] FIG. 8 is a signaling diagram depicting a CBRA process, according to some example embodiments of the present disclosure. The CBRA process 800 can be viewed as depicting an example implementation of method 500 and 600 performed by the loT reader node 202 and the loT device 204. It is to be noted that the method 500 and / or method 600 may not necessarily include all the steps in FIG. 800. In particular, each of the methods 500 and 600 may include a subset of the steps of the CBRA process 800.

[0059] In some implementations, the loT (or AIoT) reader node 202 can transmit or broadcast, e.g., at step 0, an access round trigger to signal the start of an access round to loT devices 204 interested or intending to access the loT reader node 202. TThe transmission of the access round trigger can be triggered by a session controller unit (SCU), e.g., a session controller unit of the communication network. The SCU can transmit a trigger signal to trigger the loT reader node 202 to transmit or broadcast the access round trigger.

[0060] At step 1, the loT reader node 202 can transmit or broadcast an access occasion trigger to signal the start of an access occasion to the loT device(s) 204. The access occasion trigger can be for triggering an loT random access procedure within a first sub-frame of an access frame. The access occasion trigger can be transmitted within or before the first subframe. In some implementations, the access occasion trigger can include at least one of (i) an indication of one or more resources of the first sub-frame from which the loT device 204can select at least one resource to transmit a response message, e.g., Msgl, (ii) a transmission trigger to trigger transmission of the response message, by the loT device 204, at a time instance within the first sub-frame of the access frame, or (iii) an indication for the loT device 204 to select a start time and / or at least one resource, within the first sub-frame, for the transmission of the response message, e.g., Msgl.

[0061] With regard to option (i), the loT reader node 202 can provide an indication of one or more time or time-frequency resources of the first sub-frame of the access frame, and the loT device 204 can select at least one of such resource(s) to transmit the response message, e.g., Msgl, back to the loT reader node. In option (ii), the access occasion trigger itself, a parameter within the access occasion trigger and / or the lack of the parameter within the access occasion trigger can trigger the loT device 204 to determine or identify the next available resource of the first sub-frame to transmit the response message, e.g., Msgl . Option (ii) can be viewed as implying that it is the loT reader node 202 that selects the resource inside the first sub-frame. According to option (iii), the access occasion trigger itself, a parameter within the access occasion trigger and / or the lack of the parameter within the access occasion trigger can trigger, can be interpreted as an indication for, the loT device 204 to select at least one resource of the first sub-frame and / or a start time within the first sub-frame for transmission of the response message.

[0062] At step 2, the loT device 204 can performs the transmission of the response message, e.g., Msgl, in the selected or identified random-access opportunity or resource(s) in the first sub-frame of the access frame. The response message, e.g., Msgl, can include or can be transmitted with an identifier (ID), e.g., a random ID. For instance, the loT device 204 can determine or generate the ID and insert the ID in the response message before sending to the loT reader node 202. The loT device 204 can transmit the response message according to the resource(s) selected and / or identified at step 1.

[0063] Ate step 3, and upon receiving the response message, e.g., Msgl, with the ID, the loT reader node 202 can respond or broadcast an acknowledgement message, e.g., Msg2. In some implementations, the acknowledgement message, e.g., Msg2, can be or can include an echo, copy or repetition of a Msgl received by the loT reader node 202. Sending an echo of the response message implies that the ID, e.g., random ID, associated with the responsemessage is transmitted back by the loT reader node 202 within or with the acknowledgement message.

[0064] It is to be noted that in case the loT reader node does not receive the response message, e.g., Msgl, within a defined time period, the loT reader node 202 can treat the nonreception of the response message as a failure of the random access procedure and the loT reader node 202 moves straight to step 6. In the words, failure to receive the response message, e.g., Msgl, within the defied time period implies detecting a failure of the random access procedure. The defined time period can be the first sub-frame of the access frame, a time slot of the first sub-frame associated with the transmission of the response message or another portion of the first sub-frame.

[0065] At step 4, the loT device 204 can, upon receiving the acknowledgement message, e.g., Msg2, compare the ID or random ID in the received acknowledgement message with the ID or random ID transmitted by the loT device 204 in the response message, e.g., Msgl. The loT device 204 can detect the presence of collision upon determining that the ID or random ID associated with the acknowledgement message, e.g., Msg2, does not match the ID or random ID transmitted by the loT device at step 2. The detection of collision can be viewed as a detection of a failure of the random access procedure. In some implementations, the loT device 204 can detect failure of the random access procedure if no acknowledgement message is received within a defined time period, e.g., within the first sub-frame or a portion thereof. For example, if the loT reader node 202 fails to receive a response message at step 2, e.g., due to interference, the loT reader node 202 will not transmit or broadcast any acknowledgement message.

[0066] At step 5, the loT device 204 can transmit an indication of the detected collision or failure of the random access procedure to the loT reader node 202. In some implementations, the loT device 204 can transmit the indication of collision or random access failure in Msg3. In some implementations, the indication can indicate that the loT device 204 detected a collision. In some implementations, the indication can indicate that the loT device detected the access occasion trigger but did not receive a valid acknowledgement message, e.g., valid Msg2.

[0067] At step 6, the loT reader node 202 can detect or determine a failure of the random access procedure based on either (i) the received indication in Msg3 or (ii) due to the absenceor no reception of a response message, e.g. Msgl, as discussed above in relation with step 2. In response to the detection of the failure of the random access procedure, the loT reader node 202 can decide to initiate another access occasion.

[0068] At step 7, the loT reader node 202 can decide to transmit another access occasion trigger to signal the start of a new access occasion and / or trigger the random access procedure in a second sub-frame of the access frame. In some implementations, the access occasion trigger can include at least one of (i) an indication of one or more resources of the second sub-frame from which the loT device 204 can select at least one resource to transmit a response message, e.g., Msgl, (ii) a transmission trigger to trigger transmission of the response message, by the loT device 204, at a time instance within the second sub-frame of the access frame, or (iii) an indication for the loT device 204 to select a start time and / or at least one resource, within the second sub-frame, for the transmission of the response message, e.g., Msgl. This step and the corresponding access occasion trigger can be similar to step 1 and the access occasion trigger of step 1, except that the new access occasion or random access procedure is now to be triggered in the second sub-frame of the same access frame. It is to be noted that the access occasion trigger can be transmitted within or before the second sub-frame.

[0069] At step 8, the loT device 204 can transmit a second response message, e.g., Msgl, in the random-access opportunity or resource of the second sub-frame selected and / or determined according to the received access occasion trigger. Similar to step 2, the response message can include or can be transmitted with an ID or random ID.

[0070] At step 9, the loT reader node, upon receiving the response message or Msgl with the ID or random ID payload, can provide, transmit or broadcast an acknowledgement message, e.g., Msg2. The acknowledgement message can be or can include a copy of the received response message and / or the corresponding ID or random ID. Similar to step 2, if the loT reader node 202 fails to receive a response message within a defined time period, the loT reader node 202 may return back to step 6 and trigger a new access occasion in a third sub-frame of the access frame or in another sub-frame of another access frame, e.g., if no more sub-frames are available in the original access frame.

[0071] The loT device 204 can detect that the ID or random ID of the acknowledgement message, e.g., Msg2, matches the ID or random ID that it sent in the second responsemessage, e.g., Msgl, and therefore proceeds with the transmission of its Device ID and or upper layer data in step 10. However, if the loT device 204 detects a collision or failure of random access procedure as discussed above in relation with step 3, the loT device 204 can proceed in step 10 to transmit an indication of the collision or failure.

[0072] FIG. 9 is a signaling diagram depict another CBRA process 900, according to some example embodiments of the present disclosure. The CBRA is similar to the CBRA process 800, except that in the case of a detected collision or failure of the random access procedure, no indication of the collision or failure is transmitted to the loT reader node. In other words, step 5 of the CBRA process 800 is omitted in the CBRA process 900 and no Msg3 is transmitted to the loT reader node 202. Also, with regard to the collision / failure detection at step 5 of the CBRA process 900, the loT reader node 202 can detect a collision or a failure of the random access procedure if no Msg 3 is received from the loT device 204 within a defined time period, e.g., second sub-frame or a portion thereof.

[0073] Steps 6 to 9 of the CBRA process can be viewed to be similar to steps 7 to 10 of the CBRA process 800. In FIGS. 8 and 9, N1 represents the size of the first sub-frame of the access frame and N2 represents the size of the second sub-frame of the same access frame. In other words, the rectangle denoted with N1 can represent the first sub-frame of the access frame or the access occasion performed within the first sub-frame. Similarly, the rectangle denoted with N2 can represent the second sub-frame of the access frame or the access occasion performed within the second sub-frame.

[0074] It is to be noted that while the CBRA processes 800 and 900 are described in relation with a 3 -step CBRA procedure 200 A, these processes or at least process 900 can be applicable to the 2-step CBRA procedure 200B. In such case, the ID transmitted in steps 2 and 3 as well steps 7 and 8 of the CBRA process 900 is the device ID of the loT device 204. In other words, Msgl and MSg2 will be similar to those described in FIG. 2B and there will be no Msg3 at step 9 of the CBRA process 900. According to such scenario, if the loT reader node 202 fails to receive Msgl at step 1 or step 7 for a defined time period, the loT reader node 202 can detect a failure of the random access procedure and trigger a new access occasion in another sub-frame of the same access frame.

[0075] In some implementations, the second access occasion trigger, e.g., transmitted at step 7 of CBRA process 800 or step 6 of CBRA process 900, can triggers the loT device 204to redundantly transmit the second response message, e.g., Msgl of step 8 in CBRA process 800 or step 7 in CBRA process 900, over multiple resource elements associated with different frequencies. For instance, the second access occasion trigger can include an indication of the frequency redundancy and / or multiple frequencies to be used of redundant transmission of Msgl. In some implementations, the loT device 204 can be configured to employ frequency redundancy in retransmission attempts. In other words, the following retransmission attempts may be associated with an increasingly large set of resource elements (REs) to create sufficient frequency diversity to detect the loT response or Msgl. For example, if the first transmission attempt is single tone, the second transmission attempt can be configured to be dual tone. The mapping from one tone to dual tone can pre-defined, signalled by the loT reader node 202 in the access occasion trigger or preconfigured in the loT devices 204. The loT reader node 202 can receive the second response, e.g., Msgl, over dual mode or over multiple frequencies.

[0076] In some implementations, the following re-transmission attempts may still occur within the same frame duration, but in a different set of REs. For example, the retransmission occasion k can be associated with a frequency offset fk, offset. In some implementations, the second access occasion trigger, e.g., transmitted at step 7 of CBRA process 800 or step 6 of CBRA process 900, can trigger the loT device 304 to transmit the second response message, e.g., Msgl, over a first resource element associated with a defined frequency offset relative to a second resource element over which the first response message, e.g., Msgl of step 2, is received. In some implementations the access occasion trigger transmitted after a detected failure can include an indication of the frequency offset. In some implementations, the frequency offset can be preconfigured in the loT device 204. The loT reader node 202 can receive the second response message, e.g., Msgl, according to the frequency offset.

[0077] It is to be noted that methods and processes described in the current disclosure can be implemented as computer executable instructions that can be stored in a non-transitory computer-readable medium, e.g., at least one memory. The computer-executable instructions can be executed by one or more processors or an apparatus including one or more processors.

[0078] The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0079] 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(iii) 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.”

[0080] 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.

[0081] It should be understood that the foregoing description is only illustrative. Various alternatives and modifications can be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination(s). In addition, features from different embodiments described above could be selectively combined into a new embodiment. Accordingly, the description is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Claims

24CLAIMSWhat is claimed is:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed with the at least one processor, cause the apparatus to perform: transmitting a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the apparatus and a device, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the device to select a start time, within the first sub-frame, for the transmission of the first response message; and transmitting, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

2. The apparatus of claim 1, wherein the instructions, when executed by the at least one processor, cause the apparatus to determine at least one of a duration of the first sub-frame or a duration of the second sub-frame according to at least one of: an expected number of devices that will respond to the first access occasion trigger; an expected number of devices that will respond to concurrent access occasion triggers transmitted by one or more other apparatuses; or a contention-based ratio determined by the apparatus.

3. The apparatus of claim 1 or 2, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform at least one of: receiving a configuration of the access frame from a network; configuring the access frame; or transmitting the configuration of the access frame in an access round trigger.

4. The apparatus of any of claims 1 to 3, wherein sub-frames of the access frame, including the first sub-frame and the second sub-frame, are arranged consecutively, orthe sub-frames of the access frame are interleaved with one or more sub-frames of another access frame.

5. The apparatus of any of claims 1 to 4, wherein the instructions, when executed by the at least one processor, cause the apparatus to detect the failure of the loT random access procedure responsive to not receiving the first response message within the first sub-frame.

6. The apparatus of any of claims 1 to 4, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: receiving, from the device, the first response message within the first sub-frame according to the first access occasion trigger, the first message including a first identifier; transmitting an acknowledgement message including a second identifier; and detecting the failure of the loT random access procedure responsive to not receiving a response to the acknowledgement message from the device within the first sub-frame.

7. The apparatus of any of claims 1 to 4, wherein the instructions, when executed by the at least one processor, cause the apparatus to receive an indication of the failure of the loT random access procedure from the device, the second access occasion trigger transmitted by the apparatus responsive to the indication of the failure of the loT random access procedure.

8. The apparatus of claim 7, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: receiving, from the device, the first response message within the first sub-frame according to the first access occasion trigger, the first message including a first identifier; transmitting an acknowledgement message including a second identifier; and receiving, from the device, the indication of the failure of the loT random access procedure responsive to at least one of (i) the second identifier being different from the first identifier or (ii) the device not receiving the acknowledgement message.

9. The apparatus of any of claims 1 to 8, wherein the second access occasion trigger includes at least one of:a transmission trigger to trigger transmission of a second response message, by the device to the apparatus, at a time instance within the second sub-frame; or an indication for the device to select a start time, within the second sub-frame, for the transmission of the second response message.

10. The apparatus of any of claims 1-9, wherein the instructions, when executed by the at least one processor, cause the apparatus to transmit, responsive to detection of a second failure of the loT random access procedure after transmission of the second access occasion trigger, a third access occasion trigger for triggering, within a third sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

11. The apparatus of claim 9, wherein the instructions, when executed by the at least one processor, cause the apparatus to detect a second failure of the loT random access procedure responsive to not receiving the second response message within the second time period.

12. The apparatus of claim 9, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: receiving, from the device, the second response message within the second sub-frame according to the second access occasion trigger, the second response message including a third identifier; and transmitting an acknowledgement message including a fourth identifier.

13. The apparatus of claim 12, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: receiving, from the device, an indication of a second failure of the loT random access procedure; and transmitting, responsive to the received indication of the second failure of the loT random access procedure a third access occasion trigger for triggering, within a third subframe of the access frame, the random access procedure between the apparatus and the device.

14. The apparatus of any of claims 1 to 13, wherein the second access occasion trigger triggers the device to redundantly transmit the second response message over multiple27 resource elements associated with different frequencies, and the instructions, when executed by the at least one processor, cause the apparatus to receive the second response message over the multiple resource elements.

15. The apparatus of any of claims 1 to 14, wherein the second access occasion trigger triggers the device to transmit the second response message over a first resource element associated with a defined frequency offset relative to a second resource element over which the first response message is received, and wherein the instructions, when executed by the at least one processor, cause the apparatus to receive the second response message over the first resource element.

16. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform: receiving, from an Internet of things (loT) reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the apparatus, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message; and receiving, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the apparatus.

17. The apparatus of claim 16, wherein sub-frames of the access frame, including the first sub-frame and the second sub-frame, are arranged consecutively, or the sub-frames of the access frame are interleaved with one or more sub-frames of another access frame.2818. The apparatus of claim 16 or 17, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: transmitting the first response message within the first sub-frame according to the first access occasion trigger, the first message including a first identifier; and receiving, from the loT reader node, an acknowledgement message including a second identifier; determining that the second identifier is different from the first identifier; and detecting the failure of the loT random access procedure responsive to determining that the second identifier is different from the first identifier.

19. The apparatus of claim 16 or 17, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: transmitting the first response message within the first sub-frame according to the first access occasion trigger, the first message including a first identifier; and detecting the failure of the loT random access procedure responsive to not receiving an acknowledgement message from the loT reader node within a defined time period after transmission of the first response message.

20. The apparatus of any of claims 16 to 19, wherein the instructions, when executed by the at least one processor, cause the apparatus to transmit an indication of the failure of the loT random access procedure to the loT reader node, the second access occasion trigger received by the apparatus responsive to transmission of the indication of the failure of the loT random access procedure.

21. The apparatus of any of claims 16 to 20, wherein the second access occasion trigger includes at least one of: a transmission trigger to trigger transmission of a second response message, by the apparatus to the loT reader node, at a time instance within the second sub-frame; or an indication for the apparatus to select a start time, within the second sub-frame, for the transmission of the second response message.

22. The apparatus of any of claims 16 to 21, wherein the instructions, when executed by the at least one processor, cause the apparatus to receive, responsive to detection of a second29 failure of the loT random access procedure after transmission of the second access occasion trigger, a third access occasion trigger for triggering, within a third sub-frame of the access frame, the loT random access procedure between the apparatus and the loT reader node.

23. The apparatus of claim 21, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: transmitting the second response message within the second sub-frame according to the second access occasion trigger, the second response message including a third identifier; receiving an acknowledgement message including a fourth identifier; determining that the fourth identifier is different from the third identifier; and detecting a second failure of the loT random access procedure responsive to determining that the fourth identifier is different from the third identifier.

24. The apparatus of claim 21, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: transmitting the second response message within the second sub-frame according to the second access occasion trigger, the second response message including a third identifier; and detecting a second failure of the loT random access procedure responsive to not receiving an acknowledgement message from the loT reader node after transmission of the second response message.

25. The apparatus of claim 23 or 24, wherein the instructions, when executed by the at least one processor, cause the apparatus to perform: transmitting, to the loT reader node, an indication of the second failure of the loT random access procedure; receiving, from the loT reader node, responsive to the indication of the second failure of the loT random access procedure, a third access occasion trigger for triggering, within a third sub-frame of the access frame, the random access procedure between the apparatus and the loT reader node.

26. The apparatus of any of claims 16 to 25, wherein the second access occasion trigger triggers the apparatus to one of:30 redundantly transmit the second response message over multiple resource elements associated with different frequencies, and the instructions, when executed by the at least one processor, cause the apparatus to transmit the second response message over the multiple resource elements; or transmit the second response message over a first resource element associated with a defined frequency offset relative to a second resource element over which the first response message is received, and wherein the instructions, when executed by the at least one processor, cause the apparatus to transmit the second response message over the first resource element.

27. A method comprising: transmitting, by an Internet of things (loT) reader node, a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the loT reader node and an loT device, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the loT device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the loT device to select a start time, within the first sub-frame, for the transmission of the first response message; and transmitting, by the loT reader node, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the loT device.

28. A method comprising: receiving, by an Internet of things (loT) device from an loT reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the loT device, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message; and31 receiving, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the loT device.

29. An apparatus comprising: means for transmitting a first access occasion trigger for triggering an Internet of things (loT) random access procedure between the apparatus and a device, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the device, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the device to select a start time, within the first subframe, for the transmission of the first response message; and means for transmitting, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the apparatus and the device.

30. An apparatus comprising: means for receiving, from an Internet of things (loT) reader node, a first access occasion trigger to trigger an loT random access procedure between the loT reader node and the apparatus, the first access occasion trigger includes at least one of (i) a transmission trigger to trigger transmission of a first response message, by the apparatus, at a time instance within a first sub-frame of an access frame, or (ii) an indication for the apparatus to select a start time, within the first sub-frame of the access frame, for the transmission of the first response message; and means for receiving, responsive to detection of a failure of the loT random access procedure, a second access occasion trigger for triggering, within a second sub-frame of the access frame, the loT random access procedure between the loT reader node and the apparatus.

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