Devices and methods for RACH preamble allocation in a mobile network

Abstract

A base station (110a) for communication with a plurality of user equipments, UEs (120a-n), is disclosed, wherein each UE (120a-n) is configured to communicate with the base station (110a) via a Random Access Channel, RACH, using a RACH preamble. The base station (110a) is configured to obtain for each of the plurality of UEs (120a-n) a UE path plan, wherein the UE path plan of each UE (120a-n) defines a planned motion path of the UE (120a-n) along a plurality of waypoints. Moreover, the base station (110a) is configured to allocate, based on the plurality of UE path plans, to one or more UEs of the plurality of UEs (120a-n) one or more RACH preambles from a set of available RACH preambles and to send an indication of the one or more allocated RACH preambles to the one or more UEs (120a-n) for allowing the one or more UEs (120a-n) to communicate with the base station (110a) using the one or more allocated RACH preambles.

Description

[0001] DEVICES AND METHODS FOR RACH PREAMBLE ALLOCATION IN A MOBILE NETWORK

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communication. More specifically, the present disclosure relates to devices and methods for Random Access Channel, RACH, preamble allocation in a mobile network.

[0004] BACKGROUND

[0005] Autonomous vehicles (A Vs) usually contain a navigating application for travelling through their 2D or 3D environments with varying levels of human assistance. AVs are manufactured and deployed at record numbers because they are characterized by maximum flexibility and mobility within their environment. The aforementioned flexibility and mobility is a consequence of the following capabilities of autonomous vehicles: path-planning, motion planning, poisture, orientation, displacement, flying, walking, driving, and the like.

[0006] Because of their flexibility and mobility, AVs rely on on-board wireless communication devices, usually in the form of a user equipment (UE), to perform the receiving and / or transmitting of many services, such as critical messages, audio / visual or audiovisual content, tele-operation instructions with varying levels of control over the vehicle, and the like. Many of these services are subject to strict requirements on the latency. The latency requirement for such critical services is characterized by the user-plane latency, referring to the time delay between the absolutely first user entity that sources the information to the user entity that is the final recipient.

[0007] The most important factor of the performance of wireless communication devices is the power of the signal received at the receiver. Since the transmitter has limited transmission power, the performance reduction of the communication is due to signal attenuation. Signal attenuation can be caused, for instance, by free-space propagation loss, destructive interference, destructive reflections and diffractions, dielectric properties of blocking objects and their size. The aforementioned causes depend on the location of a transmitting / receiving UE, and its communication partner. Due to the mobility of autonomous vehicles the signal attenuation varies with its spatial position in reference to its communication partner. Thus, the spatial position of the autonomous vehicle directly affects the latency of the communications and can even lead to a connectivity drop.

[0008] To address connectivity drops, communication devices, such as UEs, employ a random access channel (RACH) through which they can communicate at any time necessary, and is thus a method of communicating with very low latency. Communicating on RACH comes with a risk of colliding transmissions, a phenomenon where one or more devices use the communicating medium at the same time. A collision usually results in a total failure to transfer the intended information. To avoid a collision on the same medium, a UE can use a code that is orthogonal to the other UEs transmitting at the same time, hereinafter referred to as RACH preamble (or just as preamble). Only a limited number of RACH preambles exist and are thus a scarce resource. It is common to let the UE choose a preamble out of a set of preambles at random which insufficiently lowers the likelihood of collision.

[0009] Conventional solutions, that fully avoid collisions, allocate a dedicated preamble for some UE to use. Dedicating preambles is an inflexible and inefficient method as it can only support a very small number of UEs. This inflexibility is not compatible with the spatial mobility and flexibility of AVs especially in highly loaded scenarios with a number of AVs that exceed the number of preambles. SUMMARY

[0010] It is an objective of the present disclosure to provide improved devices and methods for efficiently allocating Random Access Channel, RACH, preambles to UEs, in particular vehicular UEs in a mobile network.

[0011] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0012] According to a first aspect a base station is provided for communication with a plurality of user equipments, UEs, wherein each UE is configured to communicate with the base station via a Random Access Channel, RACH, using a RACH preamble, for instance, in the case of a connectivity drop. The plurality of UEs may be vehicular UEs.

[0013] The base station according to the first aspect is configured to obtain for each of the plurality of UEs a UE path plan, wherein the path plan of each UE defines, i.e. is representative of a planned motion path of the UE along a plurality of waypoints. Moreover, the base station according to the first aspect is configured to allocate, based on the plurality of UE path plans, to one or more UEs of the plurality of UEs one or more RACH preambles from a finite set of available RACH preambles. The base station according to the first aspect is further configured to send an indication of the one or more allocated RACH preambles to the one or more UEs for allowing the respective UE to communicate with the base stations using the one or more allocated RACH preambles, for instance, in case of a connectivity drop. Thus, the base station according to the first aspect allows efficiently allocating RACH preambles to a plurality of UEs in a mobile network.

[0014] In a further possible implementation form, the base station is configured to receive the path plan of a UE from the respective UE, in response to a request from the base station.

[0015] In a further possible implementation form, the base station is further configured to obtain information about one or more spatial regions along the planned motion path of each UE with an increased connectivity drop likelihood and wherein the base station is configured to allocate the one or more RACH preambles from the finite set of available RACH preambles to one or more UEs of the plurality of UEs, based on the plurality of UE path plans and the information about the one or more spatial regions along the planned motion path of each UE with an increased connectivity drop likelihood. Thus, the base station can perform efficient utilization of preambles, by including information of the spatial regions with the highest connectivity drop likelihoods and allocating preambles to UEs that pass through spatial regions with the highest connectivity drop likelihoods.

[0016] In a further possible implementation form, the base station is configured to send in addition to the indication of the one or more allocated RACH preambles validity information to the one or more UEs, wherein the validity information defines a start waypoint and an end waypoint along the planned motion path of the UE, wherein the one or more allocated RACH preambles are usable, i.e. valid between the start waypoint and the end waypoint along the planned motion path of the UE. Thus, the preamble is efficiently exploited because it can be allocated to the UE only for the portions of the UE planned motion path that may necessitate preamble usage.

[0017] In a further possible implementation form, the path plan further defines for each of the plurality of waypoints an estimated time of arrival and a confidence value of the estimated time of arrival and wherein the base station is configured to allocate the one or more RACH preambles from the finite set of available RACH preambles to one or more UEs of the plurality of UEs, based on the confidence values of the estimated time of arrivals of the plurality of UEs at one or more of the plurality of waypoints located in the one or more spatial regions along the planned motion path of each UE with an increased connectivity drop likelihood. Thus, the base station enables an accurate calculation of the probability of the estimated time of arrival.

[0018] In a further possible implementation form, the base station is configured to not allocate one or more RACH preambles from the finite set of available RACH preambles to those UEs of the plurality of UEs having a confidence value of the estimated time of arrival of the respective UE at one or more of the plurality of way points located in the one or more spatial regions along the planned motion path of the respective UE with an increased connectivity drop likelihood that is smaller than a confidence value threshold. Thus, the base station allows for minimizing preamble collisions that can occur due to variations of the planned motion plans of UEs.

[0019] In a further possible implementation form, the confidence value is associated with a variance, in particular the inverse of the variance of a distribution of the estimated time of arrival of the respective UE at one or more of the plurality of waypoints.

[0020] In a further possible implementation form, in case a UE of the plurality of UEs has a confidence value of the estimated time of arrival of the respective UE at one or more of the plurality of waypoints located in the one or more spatial regions along the planned motion path of the respective UE with an increased connectivity drop likelihood that is smaller than the confidence value threshold, the base station is configured to request an updated path plan from the respective UE.

[0021] In a further possible implementation form, the base station is configured to provide information about the one or more RACH preambles allocated to the one or more UEs of the plurality of UEs to one or more further base stations.

[0022] In a further possible implementation form, the plurality of UEs comprise a plurality of autonomous vehicles.

[0023] According to a second aspect a method is provided for communication between a base station and a plurality of user equipments, UEs, wherein each UE is configured to communicate with the base station via a Random Access Channel, RACH, using a RACH preamble. The method according to the second aspect comprises the following steps: obtaining for each of the plurality of UEs a UE path plan, wherein the path plan of each UE is representative of, i.e. defines a planned motion path of the UE including a plurality of waypoints; allocating, based on the plurality of UE path plans, to one or more UEs of the plurality of UEs one or more RACH preambles from a finite set of available RACH preambles; and sending an indication of the one or more RACH preambles to the one or more UEs.

[0024] The method according to the second aspect can be performed by the base station according to the first aspect. Thus, further features of the method according to the second aspect result directly from the functionality of the base station according to the first aspect as well as its different implementation forms described above and below.

[0025] According to a third aspect a user equipment, UE, of a plurality of UEs for communication with a base station is provided, wherein each UE is configured to communicate with the base station via a Random Access Channel, RACH, using a RACH preamble, for instance, in the case of a connectivity drop. The UE according to the third aspect is configured to provide a UE path plan to the base station, wherein the UE path plan of the UE is representative of, i.e. defines a planned motion path of the UE including a plurality of waypoints. Moreover, the UE according to the third aspect is configured to receive from the base station an indication of one or more RACH preambles allocated from a [finite] set of available RACH preambles by the base station to the UE based on the UE path plan and one or more further UE path plans of one or more further UEs of the plurality of UEs. In a further possible implementation form, the UE is configured to provide the UE path plan to the base station, in response to a request from the base station.

[0026] In a further possible implementation form, the UE is configured to receive in addition to the indication of the one or more allocated RACH preambles validity information from the base station, wherein the validity information defines a start waypoint and an end waypoint along the planned motion path of the UE, wherein the one or more allocated RACH preambles are usable, i.e. valid between the start waypoint and the end waypoint along the planned motion path of the UE. Thus, the base station allows RACH preamble allocation for UEs with poor confidence of their planned motion plan by requesting more planned motion plan updates.

[0027] In a further possible implementation form, the UE path plan further defines for each of the plurality of waypoints an estimated time of arrival and a confidence value of the estimated time of arrival.

[0028] In a further possible implementation form, the confidence value is associated with a variance, in particular the inverse of the variance of a distribution of the estimated time of arrival of the UE at one or more of the plurality of waypoints.

[0029] In a further possible implementation form, the UE is an autonomous vehicle.

[0030] According to a fourth aspect a method of communication is provided between a user equipment, UE, of a plurality of UEs and a base station, wherein each UE is configured to communicate with the base station via a Random Access Channel, RACH, using a RACH preamble, for instance, in a case of a connectivity drop. The method according to the fourth aspect comprises the steps of: providing a UE path plan of the UE to the base station, wherein the UE path plan of the UE is representative of, i.e. defines a planned motion path of the UE including a plurality of waypoints; and receiving from the base station an indication of one or more RACH preambles allocated from a finite set of available RACH preambles by the base station to the UE based on the UE path plan and one or more further UE path plans of one or more further UEs of the plurality of UEs.

[0031] The method according to the fourth aspect can be performed by the UE according to the third aspect. Thus, further features of the method according to the fourth aspect result directly from the functionality of the UE according to the third aspect as well as its different implementation forms described above and below.

[0032] According to a fifth aspect, a computer program product is provided, comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method according to the second aspect, or the method according to the fourth aspect, when the program code is executed by the computer or the processor.

[0033] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which: Fig. 1 shows a schematic diagram illustrating a communication system including a base station according to an embodiment in communication with a plurality of UEs according to an embodiment;

[0036] Fig. 2 shows a signalling diagram illustrating the interaction between a base station according and a UE for allocating one or more RACEI preambles to the UE according to an embodiment;

[0037] Fig. 3 shows a signalling diagram illustrating the interaction between a base station and a UE for allocating one or more RACEI preambles to the UE according to a further embodiment;

[0038] Fig. 4 shows a signalling diagram illustrating the interaction between a base station, a UE and two further base stations for allocating one or more RACEI preambles to the UE according to an embodiment;

[0039] Fig. 5 shows a schematic diagram illustrating in further detail processing steps implemented by the base station according to an embodiment for allocating one or more RACH preambles to the UE according to an embodiment;

[0040] Fig. 6 shows a schematic diagram illustrating in further detail processing steps implemented by the base station according to an embodiment for processing UE path plans and allocating one or more RACEI preambles to the UE according to an embodiment;

[0041] Fig. 7 shows a flow diagram illustrating a method of operating a base station according to an embodiment; and

[0042] Fig. 8 shows a flow diagram illustrating a method of operating a user equipment according to an embodiment.

[0043] In the following, identical reference signs refer to identical or at least functionally equivalent features.

[0044] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0046] For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise. Figure 1 shows a schematic diagram illustrating a communication system 100 including a base station 110a according to an embodiment and a plurality of user equipments, UEs, 120a-n. In an embodiment, the base station 110a is configured to provide communication services, in particular network access for the plurality of UEs 120a-n and may be a base station or access point of a 3rd generation partnership project (3GPP) network, such as a 5G or 6G network, or of an IEEE 802.11 WiFi network. In an embodiment, the base station 110a is configured to provide communication services to the UEs 120a-n for downlink (BS to UE information flow), uplink (UE to BS information flow) and / or sidelink (UE to UE information flow) communication. As illustrated in figure 1, the plurality of UEs 120a-n may comprise one or more mobile, in particular vehicular UEs embedded into a respective vehicular system, such as an autonomous vehicle (AV). As used herein, an AV is understood to refer to a device that with some degree of human supervision, or no human supervision, can perform spatial navigation and transportation of itself and / or mounted objects. Examples of such AVs are cars, trucks, unmanned-aerial- vehicles (UAVs), robots, autonomously guided vehicles (A GV), and the like. The AVs considered herein may be configured to generate a path plan with some temporal duration. The AVs adhere to their path plan unless changes to such a path plan are required. In an embodiment, these vehicular UEs 120a-n are capable of V2X communication, i.e. configured to communicate with the infrastructure (i.e. the base station 110a and one or more further base stations) as well as other vehicular UEs. These UE to UE communications can occur directly (V2V) or through the base station 110 as a proxy (V2N2V).

[0047] As illustrated in figure 1 , the base station 110a may comprise a processing circuitry 111 and a communication interface 113, in particular a wireless communication interface 113, e.g. a transceiver 113 enabling communication in accordance with a 3GPP or the IEEE 802.11 framework of standards. The processing circuitry 111 of the base station 110a may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The base station 110a may further comprise a memory 115 configured to store executable program code which, when executed by the processing circuitry 111, causes the base station 110a to perform the functions and methods described herein.

[0048] Likewise, as indicated in figure 1, each of the UEs 120a-n may comprise a processing circuitry 121 and a communication interface 123, in particular a wireless communication interface 123, e.g. a transceiver 123 enabling communication in accordance with a 3GPP or IEEE 802.11 framework of standards. The processing circuitry 121 of each UE 120a-n may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. Each UE 120a-n may further comprise a memory 125 configured to store executable program code which, when executed by the processing circuitry 121, causes the UE 120a- n to perform the functions and methods described herein.

[0049] Each of the UEs 120a-n is configured to communicate with the base station 110a via a Random Access Channel, RACH, using a RACH preamble, for instance, in the case of a connectivity drop. As will be appreciated, a connectivity drop may be defined as an event marking the start of a period where the “usual” communication requirements cannot be satisfied. For instance, the communication latency of transmitted information exceeding a threshold may define connectivity drop event.

[0050] As will be described in more detail in the following under further reference to figures 2, 3 and 4, the base station 110a is configured to obtain for each of the plurality of UEs 120a-n a UE path plan, wherein the path plan of each UE 120a-n defines, i.e. is representative of a planned motion path of the UE 120a-n along a plurality of waypoints. In an embodiment, the UE path plan may define a sequence of valid spatial waypoints in a 2D or 3D environment that the mobile UE 120a follows along. In an embodiment, each waypoint may be associated with a specific estimated time of arrival (ETA). In an embodiment, the UE path plan may be generated by a navigation application implemented by the mobile UE 120a (or the AV the UE 120a is embedded in). In a further embodiment, the navigation application may be implemented by an application server within the mobile network configured to provide the UE path plan of the UE 120a to the base station 110a (either directly or indirectly via the UE 120a).

[0051] As will be described in more detail further below in the context of figures 5 and 6, the base station 110 is further configured to allocate, based on the plurality of UE path plans of the plurality of UEs 120a-n, to one or more UEs of the plurality of UEs 120a-n, for instance, to the UE 120a one or more RACH preambles from a finite set of available RACH preambles. As illustrated, for instance, in step 205 of figure 2, the base station 110a is further configured to send an indication of the one or more allocated RACH preambles to the one or more UEs, including the UE 120a, for allowing the respective UE, for instance, the UE 120a to communicate with the base station 110a using the one or more allocated RACH preambles, for instance, in case of a connectivity drop. The indication of the one or more allocated RACH preambles may comprise one or more references to RACH preambles already available at the UE 120s or the one or more RACH preambles.

[0052] As will be appreciated, the base station 110a is responsible for managing the sets and priorities of RACH preambles for the plurality of UEs 120a-n. The allocated RACH preambles may be organized in sets, out of which the UE 120a may select one to communicate over. As will be appreciated, when two UEs 120a-n select the same RACH preamble, a collision may happen forcing the UEs to retry a transmission and thus increase their latency. Embodiments disclosed herein allows addressing the issue of high collision rates of preambles when a large number of mobile UEs 120a-n (such as AVs 120a-n) go through areas with high signal attenuation.

[0053] In an embodiment, the base station 110a is configured to send in addition to the indication of the one or more allocated RACH preambles validity information to the one or more UEs, wherein the validity information defines a start waypoint and an end waypoint along the planned motion path of the respective UE 120a, wherein the one or more allocated RACH preambles are usable, i.e. valid between the start waypoint and the end waypoint along the planned motion path of the UE 120a. In other words, according to an embodiment, the base station 110a is configured to compute PPA pattems / schedules, including the indication of the one or more RACH preambles, for each UE 120a-n and to allocate preamble usage locations, that are expected to occur in the future. In addition to the UE path plans this can be based on several types of input that provide information regarding estimated / forecasted events relevant to the base station 110a, such as estimated UE locations, expected initial access, emergency event reports, and the like.

[0054] In an embodiment, the mobile UE 120a may appear within the spatial PPA management area of the base station 110a, for instance, by entering the spatial PPA management area of the base station 110a from the outside or by becoming active (i.e. power on) within the spatial PPA management area of the base station 110a. The registration procedure of the UE 120a may be initiated, for instance, according to one of the following embodiments.

[0055] In an embodiment, the UE 120a may be configured to report its PPA capabilities (for instance, whether the UE 120a is capable of RACH communication using a RACH preamble) directly to the base station 110a. In an embodiment, the base station 110a implementing, i.e. embedding the PPA entity 110a may prompt, i.e. trigger the UE 120a, for instance, by means of a request to report its UE path plan.

[0056] According to a further embodiment the UE 120a may be configured to proactively report its UE path plan to the base station 120a and to request PPA services from the base station 110a, in particular being provided with one or more RACH preambles. In this embodiment, the base station 110a is configured to respond to such a request, in particular by providing one or more RACH preambles to the UE 120a. If the UE 120a is guided by a navigation application operating in the mobile network, in a further embodiment the base station 110a may be configured to obtain the UE path plan of the UE 120a from the navigation application.

[0057] In case the UE 120a does not support a self-reported path plan, the base station 110a may obtain an estimated UE path plan of the UE 120a from a path-plan estimation entity within the network. In an embodiment, the base station 110a may be configured to allocate the one or more RACH preambles to the UE 120a, only if the accuracy of the estimated UE path plan of the UE 120a satisfies certain accuracy requirements.

[0058] According to an embodiment illustrated in figure 2, the base station 110a is configured to inform the UE 120a about one or more spatially constrained areas where it is eligible to use the one or more RACH preambles allocated to the UE 120a (see step 205 of figure 2). The allocation performed by the base station 110a in step 203 of figure 2 is referred to herein as preamble pre-allocation, PPA, because the one or more RACH preambles may be allocated by the base station 110a well in advance, i.e. before the UE 120a is entering the one or more spatially constrained areas. As illustrated in figure 2, in an embodiment, the allocation of the one or more RACH preambles in step 203 of figure 2 may be triggered by a request from the UE 120a in step 201 of figure 2. In an embodiment, the base station 110a may be configured to transmit in step 205 of figure 2 a start waypoint and / or an end waypoint along a path defined by the UE path plan, wherein the one or more RACH preambles may be used, i.e. are valid between the start waypoint and the end waypoint. In an embodiment, unless it is explicitly allowed by the base station 110a or other entities, the UE 120a is restricted to use the one or more allocated RACH preambles only inside of the area of eligibility.

[0059] According to a further embodiment illustrated in figure 3, the mobile UE 120a is able to provide further information for an improved spatial navigation within their respective 2D / 3D environment in the form of two additional information elements. This allows to determine the reliability of a UE path plan by the base station 110, which for allocating the one or more RACH preambles may require accurate UE path plan information. Thus, the procedure illustrated in figure 3 starts with a request 301 for a detailed path plan, to which the UE 120a produces a response message 303. As will be appreciated, in the context of embodiments disclosed herein reliability may be defined as a measure of likelihood that two or more allocated RACH preambles are allocated at the same time. The time importance aspect of overlapping preamble usage is irrespective of the spatial allocation of preambles. Hence, the additional information elements used according to embodiments disclosed herein allow for precise calculations of the overlapping preamble usage when performing PPA, i.e. the allocation of RACH preambles in step 305 of figure 3, leading to the final response with the allocated preambles in the pre-allocation report 307. More specifically, according to an embodiment, the UE path plan of the UE 120a may comprise one or more of the following two extra pieces of information, namely information about a quality class of the navigation application (i.e. the autonomous navigation entity navigating the UE 120a) and / or information about the statistical variance of the speed at one or more waypoints of the reported UE path plan. By identifying itself the navigating application may enable the base station 110a to set a statistical view for the UE mobility based on a combination of, for instance, the following factors: navigation application mobility capabilities, general environmental characteristics, behavior of traffic that shares the environment, the behavior of the navigation application with regards to its environment and traffic, and the like. If available at the UE 120a, the navigation application may transfer its statistical knowledge of the traffic conditions for the associated waypoints to the base station. The speed variance, for instance, may be reported in the following manners: for each waypoint, selected for only some waypoints, or one speed variance for all waypoints.

[0060] In an embodiment, the base station 110a may be configured to inform the UE 120a, if the accuracy of the obtained UE path plan of the UE 120a is not sufficient to satisfy the accuracy requirements necessary for the base station to allocate the one or more RACH preambles. In this case the base station 110a may request from the UE 120a or the navigation application a resubmission of the updated UE path plan. According to a further embodiment illustrated in figure 4, the base station 110a is configured to provide information associated with the allocation of the one or more RACH preambles to the UE 120a to one or more further base stations 110b,c illustrated in figure 4. In an embodiment, the one or more further base stations 110b,c may have overlapping or nonoverlapping management, i.e. coverage areas with the base station 110a that initiated the RACH preamble allocation process. In an embodiment, the base station 110a is configured to communicate the required spatio-temporal information of the allocated RACH preambles to the one or more further base stations 110b,c. More specifically, according to an embodiment, the currently active base station 110a performs the PPA, i.e. the allocation of RACH preambles in step 305 of figure 4 (as already described in the context of the embodiment shown in figure 3) and sends the pre-allocation report 307 back to the UE 120a. Moreover, the currently active base station 110a may forward a respective message 309b, c containing information from the messages 303 and 307 to the further base stations 110b, c. The one or more further base stations 110b, c may choose to keep the same PPA plan, in particular the same RACH preamble allocations (if the UE path plan concerns the base station 31 lb) or discard it (if the UE path plan does not concern the base station 311c), for instance, if the UE mobility is not relevant for their area.

[0061] The preamble management entity is responsible for managing the sets and priorities of preambles for the participating UEs. The preambles are organized in sets, out of which a UE can select one to communicate over. When two UEs select the same preamble, a collision happens forcing the UEs to retry a transmission and thus increase their latency.

[0062] In this scenario there is a set of K mobile UEs: UE1;UE2, ... UE;fwith a navigating application on board, present in the coverage area of the BS. While not limited to, the considered system has AVs in mind, in particular due to their communication latency requirements. AVs pre-compute their path-plan with ETA for each waypoint included, and can thus sometimes accurately report it to entities in the network through control channels made available by a BS. The AVs are partaking in chaotic traffic which means that reported path plan can become obsolete depending on many factors that the navigating application of the AV may be aware of.

[0063] The BS is the provider of wireless communication coverage. As a provider of coverage, the BS is responsible for the management of wireless radio resources, such as preambles. To better fulfill this task the BS is capable of spatial mapping the quality of service (QoS) across its coverage area. This capability aids the BS to better allocate resources when users find themselves in an area of poor QoS, such as predicting the likelihood of a connectivity drop. Each UE, being mobile, traverses the area where each part of the area is associated with some probability of drop. The probability of a dropped connection and its spatial location is a value calculated by an entity co-located with the BS and can share such information with other entities within the BS, such as the PPA.

[0064] Figure 5 shows a schematic diagram illustrating in further detail processing steps implemented by the base station 110a according to an embodiment for allocating one or more RACH preambles to the UEs 120a-n according to an embodiment. In this embodiment the base station 110a is a 3GPP RAN base station 110a. As already described above, each UE 120a-n transmits its UE path plan 503 to the base station 110a. The base station 110a, thus, obtains the UE path plan for each UE 120a-n and performs path plan extraction 511 that calculates the risk to allocating a RACH preamble to the UE 120a. Based on the locations from the path plan extraction the probability of a connectivity drop is determined in a further processing stage 515. In an embodiment, the PPA entity 110a implemented by the base station 110 may define a risk threshold value of Rt, where a risk higher than the threshold value may be harmful towards the system. If the UE 120a is selected for preamble allocation based on the calculated risk the process of allocation a RACH preamble for the UE 120a ensues in the processing stage 517. The final PPA allocation report is created in processing stage 519 and reported back to the UE 120a in stage 505 of figure 5. Depending on the risk of allocating resources for some waypoints, the PPA entity 110a implemented by the base station 110a may proceed according to an embodiment in the following way. If all waypoints have a risk smaller than the threshold, Rt< RtV i, the PPA-entity 110a implemented by the base station 110a may proceed to allocate dedicated resources, i.e. RACH preambles. If some waypoints have a risk higher than the threshold, Rt< Rt, i = I one of the following two options may be chosen: (i) a request for an updated UE path plan may be send to the respective UE 120a-n to be returned before the respective arrives at the first risky waypoint; or (ii) the PPA entity 110a implemented by the base station 110a may stop supporting the respective UE 120a-n. Likewise, if all waypoints of the UE path plan of a respective UE 120a-n have a risk higher than the threshold, the PPA entity 110a implemented by the base station 110a may stop supporting the respective UE 120a-n.

[0065] If a risk evaluation is not available, the PPA entity 110a implemented by the base station 110a may decide the eligibility based on direct calculations of internal estimations for the respective UE 120a-n. Once the eligibility has been established for all UEs 120a-n, their UE path plans may be sampled for probability of dropping (i.e. the likelihood of a connectivity drop) and segments of the UE path plan may be extracted. The segments are binned (categorized in a limited set of categories) according to their time period of occurrence and within each bin they are sorted from the highest likelihood of dropping to the lowest one. Then for each time period of occurrence, the limited number of available RACH preambles may be allocated by the PPA entity 110a implemented by the base station 110a from the highest likelihood of dropping first and so on.

[0066] If the number of RACH preambles runs out, the leftover UEs 120a-n (i.e. those UEs 120a-n that have not been allocated at least one RACH preamble yet) may be treated in the following way. In an embodiment, the PPA entity 110a implemented by the base station 110a may be configured to pre-allocate the same RACH preamble to multiple UEs 120a-n in a way that minimizes collision probability for all UEs 120a-n. If required, one RACH preamble from the set of pre-allocated RACH preambles may be chosen at random. The RACH preambles may be allocated in a lower priority group, where the RACH preambles are chosen at random and shared with other UEs.

[0067] Once the preambles have been associated with each path segment for each UE 120a, the PPA entity 110a implemented by the base station 110a proceeds to transmit the preamble area of eligibility report. The preamble area of eligibility report can be transmitted in the following way: indicating the starting and ending waypoints between which, the eligibility of the preamble and the indicator of which preamble is allocated for that segment. Such information may be exchanged for each segment allocated with a preamble.

[0068] Figure 6 shows a schematic diagram illustrating in further detail processing steps implemented by the base station 110a according to an embodiment for processing UE path plans and an enhanced UE path plan reporting from a respective UE 120a-n to the base station 110a. By means of the processing steps illustrated in figure 6 the base station 110a according to an embodiment is configured to request 601 and obtain statistically complete UE path plan information for each UE 120a-n in stage 603 of figure 6. From the input of the path plan information in this embodiment the base station 110a computes a mathematical probability distribution in stage 605 of figure 6, for the time of arrival for the waypoints of the UE 120a that is constructed with: shape that is derived from the navigation class id, locations derived from the estimated time of arrival, and distribution scale from the speed variance of the UE 120a. The distribution is then used to extract the spatial location for each waypoint, and to determine the risk of allocating the preamble in stage 607 of figure 6.

[0069] In an embodiment, each UE 120a-n may report its UE path plan by means of a UE path plan reporting mechanism 603 to the base station 110a, such as by means of the 3GPP compliant flight path information report. As will be appreciated, a flight path information report is only intended for UAVs and has many limitations for reporting accurate path plans. Therefore, additionally each UE 120a-n may inform the base station 110a about the navigation application identity and the speed variance per waypoint.

[0070] In an embodiment, the base station 110a may receive at least portions of the following information:

[0071] • An array of V elements, each element i is the spatial coordinates lltl2, lt... lNfor the waypoints that can be presented as point- like (a single point in the space closely representing the center of the respective UE 120a-n) or shape-like (a shape: ellipsoid, rectangle, circle, sphere etc., that represents the shape of the respective UE 120a-n as well as its error in location misestimation);

[0072] • An array of N the temporal coordinates indicating the time the respective UE 120a-n will reach each spatial coordinate i (this information may be omitted if spatial coordinates are sampled for regular time-periods, e.g. each second in the future);

[0073] • A code representative of the identity of the navigating application guiding the respective UE 120a-n. This identity may be used for determining a time management behavior of the respective UE 120a-n.

[0074] • An array of N numbers representative of the speed variance for at least one waypoint i. This represents the uncertainty to the UEs spatial location at a fixed time or its timing error of reaching a certain waypoint and, therefore, may be used as a measure of the accuracy of the timing information.

[0075] In an embodiment, the base station 110a receives the four pieces of information described above and constructs the following statistical view for the random variable of time

[0076] • Use the time horizon of the temporal coordinates to define the expected time i ,2, ... .Nneeded to reach a way point lt.

[0077] • Use the navigating application identity to extract the distribution of the likely temporal variations to the UE path plan ( . The distribution of delays may be assumed to be universal for all navigation applications of the same kind since they navigate their environment and traffic in a similar manner.

[0078] • Use the speed variance to extract the variance a1, a2, ... Tv °feach waypoint expectation Mi ,M2> ... M, of each way point lt.

[0079] Based on the function (jit, cr,- , x) for a random variable x a risk of choosing the waypoint expectation can be extracted by the base station 110a. An example of risk extraction is following risk function: where L(X, ) is a suitable loss function. In an embodiment, the loss may be the time difference with regards to the reported estimation. A linear example is g (x, M) = \fi — x | . The base station 110a may then use the spatial UE path plan and the associated risk to decide whether the calculated risk is tolerable or not.

[0080] According to a further embodiment, which is a variant of the embodiment shown in figure 5, the base station 110a may define as an alternative or in addition to the spatial restrictions of the one or more allocated RACH preambles temporal restrictions of the one or more allocated RACH preambles. In other words, in an embodiment the base station 110a may be configured to replace the spatially defined validity area of the one or more RACH preambles used in the embodiment of figure 5 with a temporal validity period of the one or more allocated RACH preambles. More specifically, in this embodiment instead of defining the waypoints between which the respective allocated RACH preamble is eligible, the base station may indicate in its message to the respective UE 120a-n the period in which the RACH preamble is eligible, i.e. the starting and ending timestamps. This embodiment contains benefits with regards to time-based channel attenuation connectivity drops. As will be appreciated, embodiments disclosed herein provide in particular the following advantages. The pre-allocation of one or more RACH preambles by the base station for a limited spatial or temporal eligibility allows increasing the RACH preamble re-use by being able to allocate them for a shorter period than conventionally possible and allowing for preamble allocation well in advance to periods in the future when a preamble will be actually required. By managing the RACH preamble pre-allocation the base station 110a according to an embodiment allows optimizing preamble pre-allocation to reduce preamble collision rates for forecasted events. The introduction of location indicators for starting and ending for RACH preamble eligibility enables a location based RACH preamble eligibility allowing for high precision location correlated preamble use.

[0081] Figure 7 shows a flow diagram illustrating a method 700 for communication between the base station 110a and the plurality of user UEs 120a-n. As already described above, each HE 120a-n is configured to communicate with the base station 110a via a RACH using a RACH preamble. The method 700 comprises a step 701 of obtaining for each of the plurality of UEs 120a-n a UE path plan, wherein the UE path plan of each UE 120a-n is representative of a planned motion path of the UE 120a-n along a plurality of waypoints. Moreover, the method 700 comprises a step 703 of allocating, based on the plurality of UE path plans, to one or more UEs of the plurality of UEs 120a-n one or more RACH preambles from a finite set of available RACH preambles. The method 700 further comprises a step 705 of sending an indication of the one or more RACH preambles to the one or more UEs for allowing the one or more UEs to communicate with the base station 110a using the one or more allocated RACH preambles.

[0082] The method 700 can be performed by the base station 110a. Thus, further features of the method 700 result directly from the functionality of the base station 110a as well as the different embodiments thereof described above and below.

[0083] Figure 8 shows a flow diagram illustrating a method 800 of communication between the UE 120a of the plurality of UEs 120a-n and the base station 110a. As already described above, each UE of the plurality of UEs 120a-n is configured to communicate with the base station 110a via a RACH using a RACH preamble, for instance, in the case of a connectivity drop. The method 800 comprises a step 801 of providing a UE path plan of the UE 120a to the base station 110a, wherein the UE path plan of the UE 120a is representative of, i.e. defines a planned motion path of the UE 120a along a plurality of waypoints. Moreover, the method 800 comprises a step 803 of receiving from the base station 110a an indication of one or more RACH preambles allocated from a set of available RACH preambles by the base station 110a to the UE 120a based on the UE path plan of the UE 120a and one or more further UE path plans of one or more further UEs of the plurality of UEs 120a-n.

[0084] The method 800 can be performed by any one of the UEs 120a-n, for instance, the UE 120a. Thus, further features of the method 800 result directly from the functionality of the UE 120a as well as the different embodiments thereof described above and below.

[0085] The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

[0086] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely a logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

[0087] In addition, functional units in the embodiments of the disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units may be integrated into one unit.

Claims

CLAIMS1. A base station (110a) for communication with a plurality of user equipments, UEs (120a-n), each UE (120a-n) being configured to communicate with the base station (110a) via a Random Access Channel, RACH, using a RACH preamble, wherein the base station (110a) is configured to: obtain for each of the plurality of UEs (120a-n) a UE path plan, wherein the UE path plan of each UE (120a-n) defines a planned motion path of the UE (120a-n) along a plurality of way points; allocate, based on the plurality of UE path plans, to one or more UEs of the plurality of UEs (120a-n) one or more RACH preambles from a set of available RACH preambles; and send an indication of the one or more allocated RACH preambles to the one or more UEs (120a-n) for allowing the one or more UEs (120a-n) to communicate with the base station (110a) using the one or more allocated RACH preambles.

2. The base station (110a) of claim 1, wherein the base station (110a) is configured to receive the UE path plan of a UE from the respective UE (120a-n), in response to a request from the base station (110a).

3. The base station (110a) of claim 1 or 2, wherein the base station (110a) is further configured to obtain information about one or more spatial regions along the planned motion path of each UE (120a-n) with an increased connectivity drop likelihood and wherein the base station (110a) is configured to allocate the one or more RACH preambles from the set of available RACH preambles to one or more UEs of the plurality of UEs (120a-n), based on the plurality of UE path plans and the information about the one or more spatial regions along the planned motion path of each UE with an increased connectivity drop likelihood.

4. The base station (110a) of claim 3, wherein the base station (110a) is configured to send in addition to the indication of the one or more allocated RACH preambles validity information to the one or more UEs (120a-n), wherein the validity information defines a start waypoint and an end waypoint along the planned motion path of the respective UE (120a- n), wherein the one or more allocated RACH preambles are usable between the start waypoint and the end waypoint.

5. The base station (110a) of claim 3 or 4, wherein the UE path plan further defines for each of the plurality of waypoints an estimated time of arrival and a confidence value of the estimated time of arrival and wherein the base station (110a) is configured to allocate the one or more RACH preambles from the set of available RACH preambles to one or more UEs of the plurality of UEs (120a-n), based on the confidence values of the estimated time of arrivals of the plurality of UEs (120a-n) at one or more of the plurality of waypoints located in the one or more spatial regions along the planned motion path of each UE with an increased connectivity drop likelihood.

6. The base station (110a) of claim 5, wherein the base station (110a) is configured to not allocate one or more RACH preambles from the set of available RACH preambles to those UEs of the plurality of UEs (120a-n) having a confidence value of the estimated time of arrival of the respective UE (120a-n) at one or more of the plurality of waypoints located in the one or more spatial regions along the planned motion path of the respective UE with an increased connectivity drop likelihood that is smaller than a confidence value threshold.

7. The base station (110a) of claim 6, wherein the confidence value is associated with a variance of a distribution of the estimated time of arrival of the respective UE (120a-n) at one or more of the plurality of way points.

8. The base station (110a) of claim 6 or 7, wherein, in case a UE of the plurality of UEs (120a-n) has a confidence value of the estimated time of arrival of the respective UE at one or more of the plurality of waypoints located in the one or more spatial regions along the planned motion path of the respective UE with an increased connectivity drop likelihood that is smaller than the confidence value threshold, the base station (110a) is configured to request an updated path plan from the respective UE (120a-n).

9. The base station (110a) of any one of the preceding claims, wherein the base station (110a) is configured to provide information about the one or more RACH preambles allocated to the one or more UEs of the plurality of UEs (120a-n) to one or more further base stations (110b, c).

10. The base station (110a) of any one of the preceding claims, wherein the plurality of UEs (120a-n) comprise a plurality of autonomous vehicles (120a-n).

11. A method (700) for communication between a base station (110a) and a plurality of user equipments, UEs (120a- n), each UE (120a-n) being configured to communicate with the base station (110a) via a Random Access Channel, RACH, using a RACH preamble, wherein the method (700) comprises: obtaining (701) for each of the plurality of UEs (120a-n) a UE path plan, wherein the UE path plan of each UE (120a-n) is representative of a planned motion path of the UE (120a-n) including a plurality of way points; allocating (703), based on the plurality of UE path plans, to one or more UEs of the plurality of UEs (120a-n) one or more RACH preambles from a set of available RACH preambles; and sending (705) an indication of the one or more RACH preambles to the one or more UEs.

12. A user equipment, UE (120a), of a plurality of UEs (120a-n) for communication with a base station (110a), each UE (120a-n) being configured to communicate with the base station via a Random Access Channel, RACH, using a RACH preamble, wherein the UE (120a) is configured to: provide a UE path plan to the base station (110a), wherein the UE path plan of the UE (120a) is representative of a planned motion path of the UE (120a) including a plurality of waypoints; and receive from the base station (110a) an indication of one or more RACH preambles allocated from a set of available RACH preambles by the base station (110a) to the UE (120a) based on the UE path plan and one or more further UE path plans of one or more further UEs of the plurality of UEs (120a-n).

13. The UE (120a) of claim 12, wherein the UE (120a) is configured to provide the UE path plan to the base station (110a), in response to a request from the base station (110a).

14. The UE (120a) of claim 12 or 13, wherein the UE (120a) is configured to receive in addition to the indication of the one or more allocated RACH preambles validity information from the base station (110a), wherein the validity informationdefines a start waypoint and an end waypoint along the planned motion path of the UE (120a), wherein the one or more allocated RACH preambles are usable between the start waypoint and the end waypoint.

15. The UE (120a) of claim 13 or 14, wherein the UE path plan further defines for each of the plurality of waypoints an estimated time of arrival and a confidence value of the estimated time of arrival of the UE (120a).

16. The UE ( 120a) of claim 15 , wherein the confidence value is associated with a variance of a distribution of the estimated time of arrival of the UE at one or more of the plurality of waypoints.

17. The UE (120a) of any one of claims 12 to 16, wherein the UE (120a) is an autonomous vehicle (120a).

18. A method (800) of communication between a user equipment, UE (120a), of a plurality of UEs (120a-n) and a base station (110a), each UE (120a-n) being configured to communicate with the base station (110a) via a Random Access Channel, RACH, using a RACH preamble, wherein the method (800) comprises: providing (801 ) a UE path plan of the UE (120a) to the base station (110a), wherein the UE path plan of the UE (120a) is representative of a planned motion path of the UE (120a) including a plurality of waypoints; and receiving (803) from the base station (110a) an indication of one or more RACH preambles allocated from a set of available RACH preambles by the base station (110a) to the UE (120a) based on the UE path plan and one or more further UE path plans of one or more further UEs of the plurality of UEs (120a-n).

19. A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (700) of claim 11 or the method (800) of claim 18 when the program code is executed by the computer or the processor.

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