Dedicated random access channel allocation

Abstract

Aspects and embodiments relate to methods for allocating dedicated random access channel usage to user equipment in a wireless communication network, and apparatuses configured to perform the methods. One aspect provides 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 at least: receive an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the apparatus, the timing offset is to be applied by the apparatus with respect to a transmission on a random access channel using a dedicated random access channel preamble identifier.

Description

Technical Field

[0001] Various example embodiments relate to methods for allocating dedicated random access channel usage to user equipment in a wireless communication network and apparatuses configured to perform these methods. Background Art

[0002] Wireless communication systems are subject to ongoing development and evolution.

[0003] As wireless communication systems develop and evolve, some adaptation of wireless communication devices, infrastructure, and signaling may be required to support mobility.

[0004] The fifth-generation technology standard (5G) for broadband cellular networks has proposed specifications that have been created to address a wide range of use cases. Such use cases include options to move the network away from voice or data-only networks of previous generations. The various use cases supported by a 5G-compatible network can lead to different ecosystems of devices supported by the network. Each type of device can have different capabilities.

[0005] To be able to effectively handle all use cases and different ranges of devices, it has been proposed that 5G standards supporting arrangements where the reason and / or type of the device attempting to access the network can be identified as early as possible may be helpful.

[0006] As one of the main uses of the random access channel (RACH), the RACH is an uplink (UL) physical channel by which a user equipment (UE) initiates access to the network. During the initial phase of access to the network, the network does not know the type of the UE attempting to access the network and the reason the UE may be attempting to access the network. The types of UEs that may attempt to access the network include, for example, energy harvesting devices, Internet of Things (IoT) devices, vehicular devices, fixed access devices, low-capability devices, etc. In addition, during the initial phase of access, the reason the UE is accessing the network may also be opaque to the network. Reasons for accessing the network can include, for example, a request from the UE to access a specific slice. The standard defines various triggers that enable the UE to initiate access to the base station. Such triggers are defined in Section 9.2.6 of TS 38.300. The proposed triggers are typically (e.g., via paging the UE or via a physical downlink control channel (PDCCH) command) associated with one of two things: a UE that needs access to communication towards the gNB or a gNB that indicates a request to the UE to perform a random access procedure.

[0007] Although the random access procedure provides an opportunity to exchange information between the UE and the network as early as possible during the connection process, RACH resources are limited, and there are many various options related to the UE type, access capabilities, and reasons for accessing the network.

[0008] Early knowledge of UE capabilities may lead to reduced network overhead and higher spectral efficiency.

[0009] There is a desire to provide methods that can support early knowledge of UE capabilities in a 5G communication network. Summary of the Invention

[0010] The scope of protection sought by various example embodiments of the present invention is set forth in the independent claims. Example embodiments and features (if any) described in this specification that do not fall within the scope of the independent claims should be construed as examples to assist in understanding the various embodiments of the present invention.

[0011] According to various but not necessarily all example embodiments, there is provided an apparatus including: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the apparatus, the timing offset to be applied by the apparatus regarding transmissions on a random access channel using the dedicated random access channel preamble identifier.

[0012] In some embodiments, the assigned timing offset is assigned on a per-device basis.

[0013] In some embodiments, the assigned timing offset assigned to the apparatus is different from the assigned timing offset assigned to another apparatus for use regarding the dedicated random access channel preamble identifier.

[0014] In some embodiments, the apparatus is configured to: determine one or more conditions associated with the use of the timing offset assigned to the apparatus, the timing offset to be applied by the apparatus regarding the dedicated random access channel preamble identifier; and evaluate whether the one or more conditions are satisfied before using the timing offset assigned to the apparatus, the timing offset to be applied by the apparatus regarding the dedicated random access channel preamble identifier.

[0015] In some embodiments, the one or more conditions include: an assessment by the apparatus of the apparatus's position in a cell of a wireless communication network.

[0016] In some embodiments, the position in the cell includes an indication of the distance between the apparatus and a serving cell network node.

[0017] In some embodiments, the one or more conditions include: a comparison between the assigned timing offset and an indication of the radio propagation delay between the apparatus and a transmission network node to which the apparatus will transmit the dedicated random access channel preamble identifier.

[0018] In some embodiments, if the device is determined to fail to meet at least one of one or more conditions, the device is configured to avoid using a dedicated random access preamble identifier for transmission on a random access channel.

[0019] In some embodiments, if the device is determined to fail to meet at least one of one or more conditions, the device is configured to initiate transmission on a random access channel using a contention-based random access preamble identifier.

[0020] In some embodiments, the device is configured to measure the received signal strength received at the device from a source cell and a neighboring cell; and determine the timing difference at the device between the source cell and the neighboring cell.

[0021] In some embodiments, the device is configured to report to the source cell the measured received signal strength received at the device from the source cell and the neighboring cell and the determined timing difference.

[0022] In some embodiments, the device is configured to implement the use of a dedicated random access channel preamble identifier by applying a timing offset assigned to the device.

[0023] In some embodiments, the device is configured to transmit a dedicated random access channel preamble identifier with the provided offset. This transmission may be received by the source cell, a neighboring cell, or a target neighboring cell.

[0024] In some embodiments, the device is configured to implement the use of a dedicated random access channel preamble identifier by applying a timing offset that is calculated as the sum of: the timing offset assigned to the device by a cell to which the dedicated random access channel preamble identifier will be transmitted; the timing difference determined at the device between the source cell and the cell to which the dedicated random access channel preamble identifier will be transmitted; and the timing advance applied by the source cell of the device.

[0025] In some embodiments, the device is configured to: the device is configured to receive a response to a transmission using a dedicated random access channel preamble identifier, the response including a relative additional timing offset to be applied by the device.

[0026] In some embodiments, in response to the received relative additional timing offset, the device is configured to establish a timing offset for the cell from which the response is received based on the sum of the timing offset employed in the transmission of the dedicated random access channel preamble identifier and the relative additional timing offset.

[0027] According to some embodiments, the device includes a user equipment of a wireless communication network.

[0028] According to various but not necessarily all example embodiments, a computer-implemented method is provided, including: receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to a device, the timing offset to be applied by the device with respect to a transmission on a random access channel using the dedicated random access channel preamble identifier.

[0029] In some embodiments, the assigned timing offset is assigned on a per-device basis.

[0030] In some embodiments, the assigned timing offset assigned to the device is different from the assigned timing offset assigned to another device for use with respect to the dedicated random access channel preamble identifier.

[0031] In some embodiments, the method includes: determining one or more conditions associated with the use of the timing offset assigned to the device, the timing offset to be applied by the device with respect to the dedicated random access channel preamble identifier; and evaluating whether the one or more conditions are satisfied before using the timing offset assigned to the device, the timing offset to be applied by the device with respect to the dedicated random access channel preamble identifier.

[0032] In some embodiments, the one or more conditions include: an assessment by the device of the device's position in a cell of a wireless communication network.

[0033] In some embodiments, the position in the cell includes an indication of the distance between the device and a serving cell network node.

[0034] In some embodiments, the one or more conditions include: a comparison between the assigned timing offset and an indication of the radio propagation delay between the device and a transmission network node, the device to transmit the dedicated random access channel preamble identifier to the network node.

[0035] In some embodiments, if it is determined that at least one of the one or more conditions is not satisfied, the method includes avoiding the use of the dedicated random access preamble identifier for transmission on the random access channel.

[0036] In some embodiments, if it is determined that at least one of the one or more conditions is not satisfied, the method includes initiating a transmission on the random access channel for use of a contention-based random access preamble identifier.

[0037] In some embodiments, the method includes: measuring the received signal strength received at the device from a source cell and neighboring cells; and determining the timing difference at the device between the source cell and the neighboring cells.

[0038] In some embodiments, the method includes: reporting to a source cell the measured received signal strengths received at the device from the source cell and neighboring cells, and the determined timing differences.

[0039] In some embodiments, the method includes: implementing the use of a dedicated random access channel preamble identifier by applying a timing offset assigned to the device.

[0040] In some embodiments, the method includes: transmitting a dedicated random access channel preamble identifier with the provided offset. The transmission may be received by the source cell, a neighboring cell, or a target neighboring cell.

[0041] In some embodiments, the method includes: implementing the use of a dedicated random access channel preamble identifier by applying a timing offset calculated as the sum of: a timing offset assigned to the device by a cell to which the dedicated random access channel preamble identifier is to be transmitted; a timing difference determined at the device between the source cell and the cell to which the dedicated random access channel preamble identifier is to be transmitted; and a timing advance applied by the source cell of the device.

[0042] In some embodiments, the method includes: receiving a response to a transmission using a dedicated random access channel preamble identifier, the response including a relative additional timing offset to be applied by the device.

[0043] In some embodiments, in response to the received relative additional timing offset, the method may include establishing a timing offset for the cell from which the response is received based on the sum of the timing offset employed in the transmission of the dedicated random access channel preamble identifier and the relative additional timing offset.

[0044] According to some embodiments, the method is performed by a user equipment of a wireless communication network.

[0045] According to various but not necessarily all example embodiments, a computer program product is provided that, when executed on a computer, is operable to perform the following steps: receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the device that is to be applied by the device for a transmission on a random access channel using the dedicated random access channel preamble identifier.

[0046] According to some embodiments, the computer program product further causes the computer to perform the following step: applying the timing offset for a transmission on a random access channel using the dedicated random access channel preamble identifier.

[0047] According to various but not necessarily all example embodiments, a non-transitory computer-readable medium is provided that includes program instructions stored thereon for at least performing the following: receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to a device, the timing offset to be applied by the device with respect to a transmission on a random access channel using the dedicated random access channel preamble identifier.

[0048] According to some embodiments, the instructions further cause the following steps: applying the timing offset with respect to a transmission on a random access channel using the dedicated random access channel preamble identifier.

[0049] According to various but not necessarily all example embodiments, a device is provided that includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the device to at least: determine that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening windows being offset in time from the start of the listening period; allocate a listening window to a candidate user equipment for use with respect to the dedicated random access channel preamble identifier; and provide an indication of a timing offset and the dedicated random access channel preamble identifier associated with the listening window allocated to the candidate user equipment.

[0050] In some embodiments, the device is configured to: receive an indication of a radio propagation time between the device and a candidate user equipment, and based on the received indication of the radio propagation time, determine whether the candidate user equipment is able to use the dedicated random access channel preamble identifier according to a listening period that has been divided into a plurality of listening windows.

[0051] According to some embodiments, the indication of the radio propagation time includes: an indication of a timing advance applied by the candidate user equipment in a source cell of the candidate user equipment, and an indication of a source-to-target cell timing difference.

[0052] According to some embodiments, the indication of the source-to-target cell timing difference includes measurements made by the candidate user equipment.

[0053] According to some embodiments, the device is configured to: allocate the same dedicated random access channel preamble identifier to more than one candidate user equipment, each candidate user equipment having a different timing offset.

[0054] According to some embodiments, the device is configured to: allocate the same dedicated random access channel preamble identifier to more than one candidate user equipment, each candidate user equipment having a different timing offset, and each candidate user equipment having a listening window of a different listening period.

[0055] According to some embodiments, the apparatus comprises a network node of a wireless communication network.

[0056] According to various but not necessarily all example embodiments, there is provided a computer-implemented method comprising: determining that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, a start of a listening window being offset in time from a start of the listening period; allocating the listening windows to candidate user equipments for use with respect to the dedicated random access channel preamble identifier; and providing the candidate user equipments with an indication of a timing offset associated with the listening time slots allocated to the candidate user equipments and the dedicated random access channel preamble identifier.

[0057] In some embodiments, the method comprises: receiving an indication of a radio propagation time between a receiving device and a candidate user equipment, and based on the received indication of the radio propagation time, determining whether the candidate user equipment is capable of using the dedicated random access channel preamble identifier according to a listening period that has been divided into a plurality of listening windows.

[0058] According to some embodiments, the indication of the radio propagation time comprises: an indication of a timing advance applied by the candidate user equipment in a source cell of the candidate user equipment, and an indication of a source-to-target cell timing difference.

[0059] According to some embodiments, the indication of the source-to-target cell timing difference comprises measurements made by the candidate user equipment.

[0060] According to some embodiments, the method comprises: allocating the same dedicated random access channel preamble identifier to more than one candidate user equipment, each candidate user equipment having a different timing offset.

[0061] According to some embodiments, the method comprises: allocating the same dedicated random access channel preamble identifier to more than one candidate user equipment, each candidate user equipment having a different timing offset, each candidate user equipment having listening windows of a different listening period.

[0062] According to some embodiments, the method is performed by a network node of a wireless communication network. According to some embodiments, the network node supports a source cell. According to some embodiments, the network node supports a target cell.

[0063] According to various but not necessarily all example embodiments, there is provided a computer program product that, when executed on a computer, is operable to perform the following steps: determining that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening window being offset in time from the start of the listening period; allocating the listening window to a candidate user equipment for use with respect to the dedicated random access channel preamble identifier; and providing the candidate user equipment with an indication of a timing offset associated with the listening time slot allocated to the candidate user equipment and the dedicated random access channel preamble identifier.

[0064] According to various but not necessarily all example embodiments, there is provided a non-transitory computer-readable medium including program instructions stored thereon for at least performing the following: determining that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening window being offset in time from the start of the listening period; allocating the listening window to a candidate user equipment for use with respect to the dedicated random access channel preamble identifier; and providing the candidate user equipment with an indication of a timing offset associated with the listening time slot allocated to the candidate user equipment and the dedicated random access channel preamble identifier.

[0065] Additional specific and preferred aspects are set forth in the appended independent and dependent claims. The features of the dependent claims may be appropriately combined with the features of the independent claims and in combinations other than those explicitly set forth in the claims.

[0066] Where an apparatus feature is described as being operable to provide a function, it should be understood that this includes the apparatus feature providing the function or being adapted or configured to provide the function. Description of the Drawings

[0067] Some example embodiments will now be described with reference to the drawings, in which:

[0068] Figure 1 An exemplary process for RACH overbooking for contention-free preambles is schematically shown;

[0069] Figure 2 A framework according to which RACH overbooking can be performed is schematically shown;

[0070] Figure 3 A flowchart for implementing RACH overbooking according to the framework discussed from the perspective of the UE is schematically shown;

[0071] Figure 4 is a signaling diagram showing the main signaling steps according to one implementation of the framework;

[0072] Figure 5 is a graphical representation of the gain achievable according to some implementations of the framework;

[0073] Figure 6 shows an apparatus in a communication system according to an example embodiment; and

[0074] Figure 7 shows a flowchart of steps in a method performed at a network node according to some example embodiments. DETAILED DESCRIPTION

[0075] Before discussing example embodiments in more detail, a general framework of a wireless communication network is first described, where an overview of the arrangement will be provided.

[0076] The concepts described can be implemented across a wide variety of telecommunication systems, network architectures, and communication standards. Aspects are generally described with reference to wireless communication systems. Such wireless communication systems typically include three interacting domains: a core network, a radio access network (RAN), and a user equipment (UE).

[0077] The RAN can be configured to implement any suitable wireless communication technology (or combination of technologies) to provide radio access to the UE. According to one example, the RAN can be configured to operate according to the Third Generation Partnership Project (3GPP) New Radio (NR) specification (commonly referred to as 5G).

[0078] When a user equipment (UE) moves through a wireless communication system, it can move through areas (cells) of wireless coverage supported by one or more radio access network nodes. The operating characteristics of the cells supported by network access nodes within a wireless communication network can vary. A wireless communication system can include various transmission and reception points (TRP). The UE and the network are typically configured such that they can continue to communicate effectively as the UE moves through the radio coverage area.

[0079] As mentioned above, the fifth generation technology standard (5G) for broadband cellular networks has proposed specifications that have been created to address a wide range of use cases. Such use cases include options to move the network away from voice or data - dedicated networks of previous generations. The various use cases supported by a 5G - compatible network can lead to different ecosystems of devices supported by the network. Each type of device can have different capabilities.

[0080] To be able to effectively handle all use cases and different ranges of devices, it has been proposed that 5G standards supporting arrangements where the reason and / or type of a device attempting to access the network can be identified as early as possible might be helpful. It is believed that early knowledge of UE capabilities can lead to reduced network overhead and higher spectral efficiency.

[0081] As one of the main uses of the Random Access Channel (RACH), the RACH is an uplink (UL) physical channel by which a User Equipment (UE) initiates access to the network. During the initial phase of access to the network, the network generally does not know the type of the UE attempting to access the network and the reason why the UE may be attempting to access the network.

[0082] The types of UEs that may attempt to access the network include, for example, energy harvesting devices, Internet of Things (IoT) devices, vehicular devices, fixed access devices, low-capability devices. The reasons for accessing the network can include, for example, requests from the UE to access a specific slice.

[0083] The standard defines various triggers that enable a UE to initiate access to a base station. Such triggers are defined in Section 9.2.6 of TS 38.300. The proposed triggers are generally associated (e.g., via paging the UE or via a Physical Downlink Control Channel (PDCCH) command) with one of two things: a UE that needs to access communication towards the gNB or a gNB that indicates to the UE a request to perform a random access procedure.

[0084] Although the random access procedure provides an opportunity to exchange information between the UE and the network as early as possible during the connection process, RACH resources are limited and there are many diverse options related to the following: UE type, ability and reason for accessing the network.

[0085] The process of using to exchange additional information between the UE and the network may have associated problems. For example, for the case where the UE is only establishing a link for a short connection, the exchange of UE capabilities or UE characteristics can further delay the time until the network can fully utilize the UE capabilities. Early knowledge of the UE's capabilities can allow the connection to be established, which can result in reduced overhead and higher spectral efficiency.

[0086] It is possible to obtain UE characteristic capabilities from a central entity (e.g., via the Access and Mobility Management Function AMF), but such an approach may not always provide the required information with an appropriate short delay. For example, such information may not be provided in time to support an intelligent decision on how to handle the transmission of messages related to the initial RRC connection establishment.

[0087] It is possible to provide or allocate separate (multiple) RACH resources, thus allowing differential treatment for each type of UE or use case, but this differential allocation results in a reduction in the pooling gain, for example, among the typically available 64 random access preambles. By pre-assigning random access preambles to a specific UE usage or specific UE capabilities, this results in a higher RACH collision probability.

[0088] It is possible to add additional RACH opportunities in the time domain / frequency domain, but such addition incurs additional overhead that needs to be semi-statically configured.

[0089] The described arrangement presents a way to increase RACH capacity in a way that can support providing "more" random access preambles, and to provide a mechanism to provide an early indication of UE capabilities and / or UE requests to the network without incurring excessive overhead or degradation of RACH channel performance.

[0090] Before discussing the example embodiments in more detail, an overview will first be provided.

[0091] A framework can provide a device, such as a user equipment, including:

[0092] An indication component for receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the device, which timing offset will be applied by the device for transmission on the random access channel using the dedicated random access channel preamble identifier.

[0093] The framework can further provide a device, such as a network node supporting a source cell or a target cell, including: a component for determining that a listening period associated with a dedicated random access channel preamble identifier will be divided into a plurality of listening windows, the start of the listening window being offset in time from the start of the listening period; a component for allocating a listening window to a candidate user equipment for use with the dedicated random access channel preamble identifier; and a component for providing to the candidate user equipment an indication of the timing offset and the dedicated random access channel preamble identifier associated with the listening window allocated to the candidate user equipment.

[0094] The framework can provide that the device includes circuitry or logic configured to perform the functions set forth herein.

[0095] It should be understood that there are two types of random access: contention-based random access and non-contention-based (dedicated) random access.

[0096] When a UE transmits a random access preamble, the UE transmits using a specific pattern, and this specific pattern is called a signature. In each cell, typically a total of 64 random access preamble signatures are available.

[0097] According to the dedicated random access procedure, the network is configured to frequently notify the UE via RRC signaling or via physical layer signaling (e.g., downlink control information (DCI)), whereby the UE is provided with a random access preamble index indicating when and which random access preamble signature to use. In accordance with this, the network operates to allocate dedicated preamble signatures so that UEs do not conflict.

[0098] The arrangement provides a framework for increasing the number of available dedicated random access preamble IDs in a cell by "overbooking" the dedicated random access preamble IDs assigned to UEs. By using such a framework to overbook dedicated random access preambles, a cell can, for example, be operated to configure fewer dedicated preambles and allow more contention-based preambles. Either way, the framework supports a mechanism by which the RACH capacity can be increased.

[0099] According to the overbooking framework, the network (e.g., a source cell or a target cell) can be configured to indicate an offset to be applied by a UE when performing a random access procedure towards the cell.

[0100] Figure 2 A framework according to which random access channel preamble overbooking can be performed is schematically shown.

[0101] Figure 2 On the left hand side, a typical random access procedure is shown, according to which a dedicated random access preamble ID 10 is within a cyclic shift (CS)-associated region 20 to which it belongs, fits, or is expected. Thus, for example, a receiving node in the network, such as at a base station serving the cell, can interpret such a random access preamble ID 10 (if the random access preamble ID 10 is received). The dedicated random access preamble is transmitted by a UE at known timing instances. To ensure that the cell receiver can receive the transmissions made by the UE as expected, each UE has an associated timing advance that takes into account the radio propagation delay caused by the distance between the UE and the source receiver. The farther the UE is from the cell receiver, the greater the timing advance (TA) applied by the UE.

[0102] The timing advance with respect to the random access procedure (which can help set the TA for the UE in a first instance) is shown as period 5.

[0103] Figure 2 On the right hand side, an example of RACH preamble "overbooking" according to the framework described herein is shown. In Figure 2In the example shown, two UEs are configured to share dedicated RACH preamble IDs 10a and 10b, and can use the same cyclic shift (CS) associated region 20a, as shown in the figure. In other words, the traditional single cyclic shift space is divided into multiple (in this case, two) listening windows 60a and 60b. By considering the possible delay spread 30 and also allowing for guard samples 40, the sampling periods 70a and 70b of each listening window are separated from the adjacent sampling periods of the listening window. Each UE can have a different determinable timing advance 5a and 5b. To indicate the appropriate TA to each UE, an overbooking framework may need to be considered, which has effectively divided the zero correlation zone into multiple listening time slots. In fact, an explicit timing advance must be indicated to the UE to be "overbooked" into the zero correlation zone, and each explicit timing advance includes a new listening window period.

[0104] In a numerical example, assume that RACH format 0 is configured with 24 reserved dedicated random access preambles.

[0105] The parameter zero correlation zone (ZCZ) (represented by 20 and 20a) is selected to enable a RACH cell range of 10 km, with an NCS configuration value = 10, resulting in: · 76 samples per cyclic shift (NCS) · 839 / 76 = 11 orthogonal signatures per root sequence.

[0106] Assume a delay spread of 5 μs (30) and 2.25 "guard" samples forming the guard period (40), and if it can be assumed that based on the cell topology and deployment scenario, since the measurement report sent by the UE is not greater than 2 km (13 μs), the UE compensates for the timing difference between the source cell and the target cell and the error in mobility, then: · Considering 2 km = 13.98 samples and a delay spread = 4.96 samples, according to the overbooking framework, one can have: · Floor(76 / (13.98 + 4.96 + 2.25)) = 3 UEs per ZCZ (i.e., per dedicated RACH preamble). · For a maximum relative difference of 1 km, the framework allows up to 5 UEs per dedicated RACH preamble · This means that instead of allocating 24 out of the 48 available possible RACH preambles to dedicated preambles, it may be possible to reserve 1 / 3 less (in the case of 2 km) or 1 / 5 less (in the case of 1 km), and the saved RACH preamble capacity can instead be used for contention-based RACH access to the network. Available gain

[0107] Assuming that 24 dedicated RACH preambles are available and the overbooking factor is 5, it is possible to increase the number of available contention-based RACH preambles for the cell by nearly 50%. By applying an overbooking factor of 2, it is possible to achieve a gain of nearly 30%. Figure 5 Graphically shows the gain available in the contention-based RACH preambles as the RACH overbooking factor is applied.

[0108] It should be understood that the time to prepare and execute a handover is relatively fast (less than 1 second). Thus, if the UE is considered capable of offsetting 2 km during the period between the last measurement report of the UE sent to the source cell and when the UE initiates a RACH procedure, this would imply that the UE would be moving at a speed of 7200 km / h (this scenario is only experienced for deployments such as non-terrestrial networks (NTN), where there are usually other means to control the initial access timing). Thus, in practice, the RACH can be "overbooked" by even more than the numerical examples set forth above, and the main factor(s) to consider in the context of whether to apply the RACH preamble overbooking technique according to the framework will be: the timing advance (TA) timing drift of the source cell, TA accuracy, and timing error. Example implementation: Network control method

[0109] According to an example implementation of the framework, the network can be configured to decide, based on various conditions now met, whether the RACH overbooked RACH preamble should be adopted by the UE in the use of the RACH overbooked RACH preambles for the RACH connected to the cell.

[0110] Figure 1 Schematically shows an exemplary process for RACH overbooking for contention-free random access preambles.

[0111] Figure 1 The scenario mapped is one of: The UE can be the subject of a handover between the source cell 100 and the target cell 200.

[0112] According to an example of the shown framework, the source unit 100 can be configured to perform the following steps:

[0113] S10: The source cell configures the UE to perform measurements for one or more neighboring cells. The measurements can include, for example, at least: reference signal received power (RSRP) and timing difference measurements.

[0114] S20: After receiving the measurement report from the UE, the source cell 100 can decide to trigger a handover related to the UE.

[0115] S30: The source cell 100 initiates a handover (HO) preparation request process to the target cell 200. The source cell is configured to include additional information, for example, the timing difference between the source cell and the target cell measured by the UE, and the current timing advance (TA) value of the UE at the source cell.

[0116] S40: After the handover preparation process to the target cell is successfully completed, the source cell is configured to forward a handover command to the UE.

[0117] According to an example of the shown framework, the target cell 200 may be configured to perform the following steps:

[0118] T10: The target cell 200 is configured to receive a handover preparation request and initiate an appropriate process. The handover preparation request includes the timing difference between the source cell 100 and the target cell 200 measured by the UE and the timing advance (TA) value of the UE applied in the source cell 100.

[0119] T20: The target cell 200 is configured to determine whether RACH overbooking according to the framework can be adopted for the UE.

[0120] The determination at the target cell may depend on: the measured timing difference between the source cell and the target cell, the timing advance applied by the UE in the source cell, and may additionally consider other possible correlation parameters, such as UE speed, which may be determined, for example, based on the handover preparation information shared by the source cell 100 and the target cell 200. The target cell is configured to decide whether to allocate a "prebooked" contention-free preamble to the UE based on the configured zero-correlation zone parameter of the cell and the potential UE timing error related to, for example, the subcarrier spacing of the target cell. More details about the determination process are provided below.

[0121] T30: If the target cell 200 decides to use a prebooked RACH preamble ID for the UE handover process based on the above-mentioned determination, it provides the ID of the allocated preamble and the explicit timing advance (TA) offset that the UE is to use for the RACH process to the UE according to the RACH overbooking framework.

[0122] T40: After detecting the allocated dedicated preamble ID, the target cell 200 is configured to transmit a random access response message including the relative TA value to be applied to the UE;

[0123] T50: The target cell may then be configured to continue and set the absolute TA value for the UE. The absolute TA value may be based on: the timing difference measured by the UE, the latest TA of the source cell, and the relative TA value sent via the random access request (RAR).

[0124] T60: If it is determined at T20 that RACH overbooking is not possible, the UE may be provided with a non-overbooked dedicated RACH preamble, or the UE is required to perform contention-based network access according to the standard 3GPP RACH procedure.

[0125] According to this framework, the evaluation or determination of whether an overbooked preamble can be allocated to the UE can be based on various factors. Depending on the implementation, as described above, those factors can include, in the case where the UE moves from a primary connection with one cell to a primary connection with another cell: the timing difference measured by the UE between the source cell and the target cell, the timing advance. Factors related to the overbooking framework also include: · Target cell zero correlation zone (ZCZ): This parameter sets the number of cyclic shifts for each root sequence and the length in samples for each cyclic shift. The cell range of the RACH can be determined via the ZCZ setting, since any detected preamble must fall within the samples of one of its determined cyclic shifts. · Although the framework assumes that network cells are synchronized, according to 3GPP specifications, there may be a timing alignment error of up to 3 μs between cells. In addition, other factors can be considered, such as UE timing error, UE TA adjustment accuracy, and UE mobility during the handover process. · It should be understood that the UE may not be able to perfectly determine the TA for the target cell based on the measurements performed and the TA applied in the source cell. However, if the error involved in determining the TA of the target cell is less than the RACH cell range of the target cell (based on the ZCZ of the target cell), then this framework may be used to overbook the RACH preamble ID.

[0126] In Figure 3 a flowchart for implementing RACH overbooking according to the framework discussed from the perspective of the UE is schematically shown.

[0127] Specifically, as Figure 3 shown, the UE 300 communicates with the source cell 100 and finally performs a handover to the target cell 200. The source cell 100 and the target cell 200 are configured to perform the steps of the flowchart according to Figure 1 According to one implementation, the UE 300 is configured to perform the following steps:

[0128] U10: The UE is configured to perform neighbor cell measurements. The measurement configuration includes at least the reference signal received power (RSRP) and the timing difference between the source cell and the measured cell.

[0129] U20: The UE is configured to send a measurement report related to the neighbor cell, which includes the neighbor cell RSRP and the timing difference, and potentially indicates that the UE is a candidate for handover to the neighbor cell.

[0130] U30: The UE is configured to receive a handover command from the source cell 100. The handover command includes an instruction to hand over to the target cell 200, which may correspond to the neighboring cell reported by the UE in step U20. According to the RACH overbooking framework, the handover command may include an explicit timing advance (TA) offset to be applied by the UE and a dedicated RACH preamble ID.

[0131] U50: The UE is configured to estimate an appropriate TA to be applied with respect to the target cell 200 based on the measured timing cell difference and the TA value of the source cell. Note that in some embodiments, the UE may not need to estimate the appropriate TA as the network may provide an absolute offset to be adopted within the explicit TA.

[0132] U60: The UE is configured to apply the explicit TA offset provided in the handover command.

[0133] U70: The UE is configured to initiate a RACH procedure using the provided dedicated RACH preamble ID and the TA value determined in U50 and U60.

[0134] U80: After receiving a random access response (RAR) message from the target cell 200, the UE is configured to determine or receive an indication of a new absolute TA. According to one implementation, the target cell 200 provides a relative TA (TA_RAR) in the RAR, and the UE may be configured to obtain the absolute TA based on TA_compensated + TA_RAR.

[0135] Figure 4 is a signaling diagram showing the signaling between the UE 300, the source cell 100, and the target cell 200 in support of handover events such as those described on a per-entity basis according to the RACH overbooking framework Figure 1 and Figure 3 between the UE 300, the source cell 100, and the target cell 200.

[0136] According to one implementation, the procedure applied between the source node 100, the UE 300, and the target node 200 may include the following steps:

[0137] C10: The source node 100 is configured to transmit a measurement configuration to the UE 300.

[0138] C20: The UE is configured to perform measurements as requested by the source node and transmit a measurement report to the source cell 100, including, for example, the measured timing offset to a potential target cell.

[0139] C30: If the handover parameters are satisfied at the UE with respect to the target cell, the source node 100 transmits a handover preparation request to the target node 200. The handover preparation request may include timing difference measurements and the current timing advance applied by the UE in the source cell.

[0140] C40: The target node determines whether the UE is a candidate for the use of the "overbooked" dedicated RACH based on the information provided to it.

[0141] C50: If the target node determines that RACH overbooking can be applied, the target node transmits a handover preparation response towards the UE via the source node. The handover preparation response includes a handover command for the UE, which includes an explicit timing advance offset to be applied and a dedicated RACH preamble ID.

[0142] C60: The source cell conveys the handover command to the UE. The handover command includes an explicit TA offset and the selected dedicated preamble ID.

[0143] C70: The UE compensates for the timing of the target node and applies the provided explicit TA offset. Note that in some embodiments, the UE may not need to perform this compensation because the network may provide an absolute offset to be employed with the dedicated preamble.

[0144] C80: The UE transmits a dedicated RACH preamble.

[0145] C90: The target node transmits a random access response to the UE that includes a relative timing offset.

[0146] C100: The UE sets the TA of the UE based on the relative timing offset, the measured timing difference between the source cell and the target cell, and the TA applied by the source node. Example implementation: UE control method

[0147] In an example implementation according to this framework, the network may be configured to decide whether an overbooked RACH preamble should be adopted by the UE based on various conditions that are currently satisfied.

[0148] In a second example implementation of the framework, the network may be configured to provide the UE with an explicit timing advance (TA) offset and a dedicated RACH preamble ID, and the UE may be configured to automatically decide whether to use the allocated dedicated "overbooked" RACH preamble or a contention-based RACH preamble when contacting the network based on meeting one or more specific conditions. In this case, the determination or evaluation of whether the UE should use the allocated "overbooked" RACH resources or a contention-based RACH may be based on one or more factors known or available to the UE. Such factors may include: knowledge of the UE location; the location of the source cell and / or target cell(s); the propagation delay and / or timing difference between the source cell and the target cell.

[0149] Whether the overbooking framework belongs to the category of network implementation or UE implementation may depend on the nature of the events supported by the dedicated RACH preamble ID. Those dedicated RACH preamble IDs allocated for cell change events may be natural candidates for the use of the overbooking framework as described above in a network implementation scenario. Those dedicated RACH preamble IDs allocated for use by the UE while remaining under the nominal control of a single cell (e.g., radio link failure, physical downlink control channel command, etc.) may be natural candidates for the use of the overbooking framework as described above in a UE implementation scenario.

[0150] An arrangement according to the described framework may be provided for increasing the number of preambles for a single RACH occasion, but generally retains the traditional RACH configuration and has little impact on the standard UE RACH procedure.

[0151] Although specific implementations of the framework have been described in detail, it should be understood that it is possible to stay within the described framework while adjusting various implementation details.

[0152] For example, as described above, the offset may be UE-related and may be exploited with respect to the use of dedicated RACH preambles. The offset may be applied to the UE in a conditional manner. For example, the UE may be configured to measure and report the timing difference between the source cell and the target cell, and an appropriate network node (i.e., the source cell or the target cell) may decide whether or not overbooking according to the framework can or should be applied based on the potential RACH timing offset difference.

[0153] According to the framework, the UE may be configured to perform a RACH procedure in which the RACH timing is adjusted in a manner that takes into account the following: source cell timing advance (TA); source-to-target cell timing difference; and the explicit timing advance (TA) offset provided by the source cell to the UE.

[0154] According to the framework, the target cell can be configured to provide a relative timing advance command (TAC) in response to a received RACH preamble from a UE.

[0155] According to the framework, the source cell or the target cell can be configured to simultaneously allocate the same dedicated RACH preamble ID to a plurality of UEs, each UE having a different explicit offset. The source cell or the target cell can be configured to allocate the same dedicated RACH preamble ID to such a plurality of UEs without changing the overall RACH configuration (e.g., zero correlation zone).

[0156] According to the framework, during the handover preparation process, the source cell can be configured to share the current TA value of the UE and the source-target cell timing difference measured by the UE with the target cell. According to some embodiments, instead of sharing the independent TA value and timing difference, a combined value is shared.

[0157] According to the framework, the source cell can be configured to indicate an offset to be applied by the UE when performing RACH, and the offset is to be applied conditionally. For example, the UE can be configured to make one or more measurements and make an autonomous determination of, for example, the location of the UE in the cell. The measurement can represent the timing offset to the serving cell (or (a) neighboring cell(s)) of the UE, and the UE can be configured to determine whether the offset can be applied based on the potential RACH timing offset difference, and thus determine whether the overbooking can be applied.

[0158] Figure 6 An apparatus in a communication system according to an example embodiment is shown; and Figure 7 A flowchart showing steps in a method performed at a network node according to some example embodiments is shown.

[0159] Specifically, Figure 6 A wireless communication network is shown, in which a transmission node 6000 is configured to communicate with a user equipment 6100. The transmission node may include a base station (e.g., gNB), and may support the source cell to which the UE 6100 is connected.

[0160] According to an example embodiment, the UE 6100 may include circuitry 6110 configured to receive an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the apparatus, the timing offset being applied by the UE for transmission on the random access channel using the dedicated random access channel preamble identifier.

[0161] A transmission node 6000 according to one embodiment may include: a circuitry 6010 configured to determine that a listening window associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening window being offset in time from the start of a listening period; a circuitry 6020 configured to allocate the listening windows to candidate user equipments for use with respect to the dedicated random access channel preamble identifier; and a circuitry 6030 configured to provide the candidate user equipments with an indication of a timing offset associated with the listening window allocated to the candidate user equipments and an indication of the dedicated random access channel preamble identifier.

[0162] Figure 7 Illustrated is a flowchart showing steps in a method performed at a network node according to some example embodiments as Figure 6 shown.

[0163] Specifically, the UE 6100 may be configured to:

[0164] 7110: Receive an indication of a dedicated random access channel preamble identifier and an indication of a timing offset allocated to the device, the timing offset to be applied by the device for transmissions on a random access channel using the dedicated random access channel preamble identifier.

[0165] The transmission network node 6000 may be configured to:

[0166] 7010: Determine that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening window being offset in time from the start of the listening period;

[0167] 7020: Allocate the listening windows to candidate user equipments for use with respect to the dedicated random access channel preamble identifier;

[0168] 7030: Be configured to provide the candidate user equipments with an indication of a timing offset associated with the listening window allocated to the candidate user equipments and an indication of the dedicated random access channel preamble identifier.

[0169] Those skilled in the art will readily appreciate that the steps of various above-mentioned methods can be performed by a programmed computer.In this article, some embodiments are also intended to encompass program storage devices, such as digital data storage media, which are machine or computer readable and encode machine executable or computer executable instruction programs, wherein the instructions perform some or all steps of the above-mentioned method.Program storage devices can be, for example, digital memories, magnetic storage media such as disks and tapes, hard drives, or optically readable digital data storage media.Embodiments are also intended to encompass computers programmed to perform the steps of the above-mentioned method.Term "non-transient" as used herein is a restriction to the medium itself (i.e., tangible, rather than signal), rather than a restriction to data storage persistence (e.g., RAM to ROM).

[0170] As used in this application, the term "circuitry" may refer to one, more, or all of the following: (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuitry) and (b) a combination of hardware circuitry and software such as (where applicable): (i) a combination of (one or more) analog and / or digital hardware circuits and software / firmware, and (ii) any portion of a hardware processor(s) with software (including a processor(s) that work together to enable a device such as a mobile phone or server to perform various functions) digital signal processor, software, and (one or more) memories) and (c) (one or more) hardware circuits and / or (one or more) processors, such as (one or more) microprocessors or portions of (one or more) microprocessors, which require software (e.g., firmware) for operation, but the software may not be present when the software is not required.

[0171] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to the particular claim element.

[0172] Although example embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

[0173] The features described in the foregoing specification may be used in combinations other than those explicitly described.

[0174] Although functions have been described with reference to certain features, these functions may be performed by other features, whether or not described.

[0175] Although features have been described with reference to certain embodiments, these features may also be present in other embodiments, whether or not described.

[0176] In the foregoing specification, although the present invention has endeavoured to emphasize those inventive features which it regards as particularly important, it is to be understood that the applicant claims protection for any patentable feature or combination of features mentioned above and / or shown in the accompanying drawings, whether or not particular emphasis has been placed thereon.

Claims

1. 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 at least: receive an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the apparatus, the timing offset to be applied by the apparatus with respect to a transmission on a random access channel using the dedicated random access channel preamble identifier.

2. The apparatus according to claim 1, wherein the apparatus is configured to: determine one or more conditions associated with the use of the timing offset assigned to the apparatus, the timing offset to be applied by the apparatus with respect to the dedicated random access channel preamble identifier; and evaluate whether the one or more conditions are met before using the timing offset assigned to the apparatus, the timing offset to be applied by the apparatus with respect to the dedicated random access channel preamble identifier.

3. The apparatus according to claim 2, wherein the one or more conditions include: An evaluation by the apparatus of the position of the apparatus in a cell of a wireless communication network.

4. The apparatus according to claim 2 or claim 3, wherein the one or more conditions include: A comparison between the assigned timing offset and an indication of a radio propagation delay between the apparatus and a transmission network node to which the apparatus will transmit the dedicated random access channel preamble identifier.

5. The apparatus according to claim 2, wherein when at least one of the one or more conditions is not met, the apparatus is configured to avoid using the dedicated random access preamble identifier for transmission on the random access channel.

6. The apparatus according to claim 5, wherein when at least one of the one or more conditions is not met, the apparatus is configured to initiate a transmission on the random access channel using a contention-based random access preamble identifier.

7. The apparatus according to any of the preceding claims, wherein the apparatus is configured to measure a received signal strength received at the apparatus from a source cell and a neighboring cell; and determine a timing difference at the apparatus between the source cell and the neighboring cell.

8. The apparatus according to claim 7, wherein the apparatus is configured to: report to the source cell the measured received signal strength received at the apparatus from the source cell and the neighboring cell and the determined timing difference.

9. The apparatus according to any of the preceding claims, wherein the apparatus is configured to: implement the use of the dedicated random access channel preamble identifier by applying the timing offset assigned to the apparatus.

10. The apparatus according to any of claims 1 to 9, wherein the apparatus is configured to implement the use of the dedicated random access channel preamble identifier by applying a timing offset calculated as the sum of: the timing offset assigned to the apparatus by a cell to which the dedicated random access channel preamble identifier will be transmitted; the determined timing difference at the apparatus between the source cell and the cell to which the dedicated random access channel preamble identifier will be transmitted; and Timing advance applied by the source cell of the device.

11. The apparatus according to any one of claims 1 to 10, wherein the apparatus is configured to receive a response to a transmission using the dedicated random access channel preamble identifier, the response including a relative additional timing offset to be applied by the apparatus.

12. The apparatus according to claim 11, wherein in response to the received relative additional timing offset, the apparatus is configured to establish a timing offset for the cell from which the response is received based on: the sum of the timing offset employed in the transmission of the dedicated random access channel preamble identifier and the relative additional timing offset.

13. A computer-implemented method, comprising: Receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the apparatus, the timing offset to be applied by the apparatus for a transmission on a random access channel using the dedicated random access channel preamble identifier.

14. 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 at least: Determine that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of a listening window being offset in time from the start of the listening period; Allocate the listening window to a candidate user equipment for use with respect to the dedicated random access channel preamble identifier; And Provide the candidate user equipment with an indication of the timing offset and the dedicated random access channel preamble identifier associated with the listening window allocated to the candidate user equipment.

15. The apparatus according to claim 14, wherein the apparatus is configured to: receive an indication of a radio propagation time between the apparatus and the candidate user equipment, and based on the received indication of the radio propagation time, determine whether the candidate user equipment can use the dedicated random access channel preamble identifier according to a listening period that has been divided into a plurality of listening windows.

16. The apparatus according to claim 15, wherein the indication of the radio propagation time comprises: An indication of the timing advance applied by the candidate user equipment in the source cell of the candidate user equipment, and an indication of a source-to-target cell timing difference.

17. The apparatus according to claim 16, wherein the indication of the source-to-target cell timing difference includes a measurement made by the candidate user equipment.

18. The apparatus according to any one of claims 14 to 17, wherein the apparatus is configured to allocate the same dedicated random access channel preamble identifier to more than one candidate user equipment, each candidate user equipment having a different timing offset.

19. A computer-implemented method, comprising: Determine that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of a listening window being offset in time from the start of the listening period; Allocate the listening window to a candidate user equipment for use with respect to the dedicated random access channel preamble identifier; And Provide an indication of the timing offset and the dedicated random access channel preamble identifier associated with the listening window assigned to the candidate user equipment to the candidate user equipment.

20. A computer program product, which when executed on a computer is operable to execute a method, the method comprising: Receiving an indication of a dedicated random access channel preamble identifier and an indication of a timing offset assigned to the device, the timing offset to be applied by the device regarding transmissions on the random access channel using the dedicated random access channel preamble identifier.

21. A computer program product, which when executed on a computer is operable to execute a method, the method comprising: Determining that a listening period associated with a dedicated random access channel preamble identifier is to be divided into a plurality of listening windows, the start of the listening windows being offset in time from the start of the listening period; Allocating the listening windows to a candidate user equipment for use regarding the dedicated random access channel preamble identifier; And Providing an indication of the timing offset and the dedicated random access channel preamble identifier associated with the listening window assigned to the candidate user equipment to the candidate user equipment.

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