PROACTIVE TIMING ADVANCE ACQUISITION FOR REDUCING HANDOVER INTERRUPTION DELAY

During a communication session with a serving radio access network node, a user equipment transmits coverage level reports corresponding to nodes neighboring the serving node as the user equipment moves. The serving node configures the user equipment with a timing advance gap period and suspends availability of resources for the communication session during the gap. The serving node may schedule the gap to coincide with a period with no traffic of the communication session to be communicated with the user equipment. During the gap, the user equipment transmits one or more configured timing advance preambles respectively corresponding to one or more neighboring nodes that, based on receiving the preambles, each prospectively determine one or more timing advance values with respect to the user equipment. After the gap, the user equipment resumes the communication session with the serving node and may use a prospectively determined timing advance during a later-instructed handover.

BACKGROUND

The ‘New Radio’ (NR) terminology that is associated with fifth generation mobile wireless communication systems (“5G”) refers to technical aspects used in wireless radio access networks (“RAN”) that comprise several quality of service classes (QoS), including ultrareliable and low latency communications (“URLLC”), enhanced mobile broadband (“eMBB”), and massive machine type communication (“mMTC”). The URLLC QoS class is associated with a stringent latency requirement (e.g., low latency or low signal/message delay) and a high reliability of radio performance, while conventional eMBB use cases may be associated with high-capacity wireless communications, which may permit less stringent latency requirements (e.g., higher latency than URLLC) and less reliable radio performance as compared to URLLC. Performance requirements for mMTC may be lower than for eMBB use cases. Some use case applications involving mobile devices or mobile user equipment such as smart phones, wireless tablets, smart watches, and the like, may impose on a given RAN resource loads, or demands, that vary. A RAN node may activate a network energy saving mode to reduce power consumption.

Handover is a procedure in cellular deployments that supports device mobility. However, for low-capability devices having a single receiver chain using conventional techniques, multiple handover control steps are performed before the handover procedure is complete and UE devices can resume transmitting or receiving useful payload of a communication session that was active before the handover. Conventional handover steps typically induce delay that may be referred to as handover interruption delay.

SUMMARY

In an example embodiment, a method may comprise establishing, by a first radio access network node comprising a processor, a communication session with a user equipment via a first connection between the first radio access network node and the user equipment. The method may further comprise receiving, by the first radio access network node from the user equipment, a first signal strength indication indicative of a first determined signal strength, corresponding to a second radio access network node, determined by the user equipment. The second radio access network node may be one of multiple nodes surrounding, or neighboring, the first radio access network node, which may be a serving radio access network node with respect to the user equipment.

The method may further comprise analyzing, by the first radio access network node, the first determined signal strength with respect to a first handover criterion resulting in an analyzed first determined signal strength. The first handover criterion may be a criterion used by the first radio access network node to determine whether a handover of the user equipment from being served by the first radio access network node to being served by a neighboring node (although a handover is not yet determined based on the first signal strength indication) may be likely to be determined based on the first signal strength indication. Based on the analyzed first determined signal strength being determined to satisfy the first handover criterion, transmitting, by the first radio access network node to the user equipment, a pre-handover measurement indication to be indicative to the user equipment to transmit to the second radio access network node a timing advance determination request message requesting determining, by the second radio access network node, a determined timing advance with respect to the user equipment. The method may further comprise receiving, by the first radio access network node from the user equipment, a second signal strength indication indicative of a second determined signal strength, corresponding to the second radio access network node, determined by the user equipment and analyzing, by the first radio access network node, the second determined signal strength with respect to a second handover criterion resulting in an analyzed second determined signal strength. Based on the analyzed second determined signal strength being determined to satisfy the second handover criterion, determining, by the first radio access network node, to handover the communication session to the second radio access network node. The method may further comprise transmitting, by the first radio access network node to the user equipment, a handover indication to be indicative to the user equipment to establish, using the determined timing advance, a second connection between the second radio access network node and the user equipment.

The pre-handover measurement indication may comprise a timing advance preamble, and the pre-handover measurement indication may be indicative to the user equipment to include the timing advance preamble in the timing advance determination request message. The timing advance preamble may be configured to correspond to the second radio access network node.

In an embodiment, the method may further comprise transmitting, by the first radio access network node to the second radio access network node, a timing advance preamble. The timing advance preamble may be transmitted in a timing advance acquisition configuration via a backhaul link/interface.

In an embodiment, the method may further comprise receiving, by the first radio access network node from the second radio access network node, the determined timing advance. The determined timing advance may be received from the second radio access network node via a backhaul link/interface.

The pre-handover measurement indication may be indicative to the user equipment that the first radio access network node is to receive, from the second radio access network node, the determined timing advance.

In an embodiment, the method may further comprise transmitting, by the first radio access network node, the determined timing advance to the user equipment via a downlink control channel information message. The downlink control channel information message may comprise resource scheduling information corresponding to the first radio access network node. The pre-handover measurement indication may comprise an identifier corresponding to the second radio access network node. The handover indication may comprise the determined timing advance, and the handover indication may be transmitted via a radio access control signal message.

The pre-handover measurement indication may be indicative to the user equipment that the user equipment is to receive, from the second radio access network node, the determined timing advance. The pre-handover measurement indication may be indicative to the user equipment that the user equipment is to transmit, to the first radio access network node, the determined timing advance.

The pre-handover measurement indication may be indicative of a timing advance determining time resource during which the user equipment is to transmit the timing advance determination request message. The timing advance determining time resource may comprise a timing advance gap period. The timing advance determining time resource may be scheduled by the first radio access network node to coincide with a period during which traffic corresponding to the communication session is not scheduled to be transmitted to, or received from, the user equipment. The pre-handover measurement indication may be indicative to the user equipment that the communication session via the first connection between the first radio access network node and the user equipment is to be halted during the timing advance determining time resource.

In an embodiment, the pre-handover measurement indication may be indicative to the user equipment that the first radio access network node is to receive, from the second radio access network node, the determined timing advance, and the pre-handover measurement indication may be indicative to the user equipment that the communication session via the first connection between the first radio access network node and the user equipment is to resume after the user equipment transmits the timing advance determination request message. The pre-handover measurement indication may be indicative to the user equipment that the user equipment is to immediately switch back to monitoring resources previously configured for the communication session after transmitting the timing advance determination request message without waiting to receive from the second radio access network node the determined timing advance.

In another example embodiment, a first radio access network node comprises a processor that may be configured to receive, from a user equipment, a timing advance preamble indicative of a request for a determination of a timing advance, corresponding to the first radio access network node with respect to the user equipment, and to determine the timing advance corresponding to the first radio access network node with respect to the user equipment. The timing advance may be used by the user equipment when conducting a handover from a second radio access network node, which may be currently serving the user equipment, to the first radio access network node, and the first radio access network node may determine the timing advance before the handover from the second radio access network node to the first radio access network node is initiated by the second radio access network node.

The processor may be further configured to receive, from the second radio access network node, the timing advance preamble; and responsive to receiving the timing advance preamble from the user equipment, analyze the timing advance preamble received from the user equipment with respect to the timing advance preamble received from the second radio access network node to result in an analyzed timing advance preamble. The first radio access network node may determine the timing advance responsive to the analyzed timing advance preamble being determined as being the same as the timing advance preamble received in the timing advance acquisition configuration.

In an embodiment, the processor may be further configured to transmit, to the user equipment, the timing advance. In another embodiment, the processor may be further configured to transmit, to the second radio access network node, the timing advance.

In another example embodiment, a non-transitory machine-readable medium may comprise executable instructions that, when executed by a processor of a first radio access network node, facilitate performance of operations, that may comprise establishing a communication session with a user equipment. The operation may further comprise transmitting, to a second radio access network node, a timing advance preamble to be indicative to the second radio access network node to determine a timing advance corresponding to the second radio access network node with respect to the user equipment upon receiving, from the user equipment, a timing advance determination request message comprising the timing advance preamble. The operations may further comprise transmitting, to the user equipment, a pre-handover measurement indication indicative to the user equipment to transmit to the second radio access network node the timing advance determination request message requesting, from the second radio access network node, the timing advance corresponding to the second radio access network node with respect to the user equipment.

In an embodiment, the pre-handover measurement indication may be indicative to the user equipment of a deactivated session resource period (e.g., a timing advance gap period), wherein the deactivated session resource period is to correspond to a period during which a resource used for the communication session is to be deactivated with respect to the user equipment, and wherein the pre-handover measurement indication is indicative to the user equipment to transmit to the second radio access network node the timing advance determination request message during the deactivated session resource period.

In an embodiment, the pre-handover measurement indication may be indicative to the user equipment that the first radio access network node is to receive, from the second radio access network node, the timing advance, and the pre-handover measurement indication may be indicative to the user equipment that the resource used for the communication session is to resume after an expiration of the deactivated session resource period.

In an embodiment, the pre-handover measurement indication may be indicative to the user equipment that the user equipment is to receive the timing advance from the second radio access network node.

In an embodiment, the pre-handover measurement indication may be indicative to the user equipment to transmit, to the first radio access network node, the timing advance after receiving the timing advance from the second radio access network node. The pre-handover measurement indication may be indicative to the user equipment that the communication session is to resume after transmission, by the user equipment to the first radio access network node, of the timing advance. In an embodiment, the user equipment may transmit the timing advance to the first radio access network node after receiving the timing advance from the second radio access network node.

DETAILED DESCRIPTION OF THE DRAWINGS

As a preliminary matter, it will be readily understood by those persons skilled in the art that the present embodiments are susceptible of broad utility and application. Many methods, embodiments, and adaptations of the present application other than those herein described as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the substance or scope of the various embodiments of the present application.

Accordingly, while the present application has been described herein in detail in relation to various embodiments, it is to be understood that this disclosure is illustrative of one or more concepts expressed by the various example embodiments and is made merely for the purposes of providing a full and enabling disclosure. The following disclosure is not intended nor is to be construed to limit the present application or otherwise exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present embodiments described herein being limited only by the claims appended hereto and the equivalents thereof.

The term “facilitate” as used herein is in the context of a system, device or component “facilitating” one or more actions or operations, in respect of the nature of complex computing environments in which multiple components and/or multiple devices can be involved in some computing operations. Non-limiting examples of actions that may or may not involve multiple components and/or multiple devices comprise transmitting or receiving data, establishing a connection between devices, determining intermediate results toward obtaining a result, etc. In this regard, a computing device or component can facilitate an operation by playing any part in accomplishing the operation. When operations of a component are described herein, it is thus to be understood that where the operations are described as facilitated by the component, the operations can be optionally completed with the cooperation of one or more other computing devices or components, such as, but not limited to, sensors, antennae, audio and/or visual output devices, other devices, etc.

Turning now to the figures,FIG.1illustrates an example of a wireless communication system100that supports blind decoding of PDCCH candidates or search spaces in accordance with one or more example embodiments of the present disclosure. The wireless communication system100may include one or more base stations105, one or more user equipment (“UE”) devices115, and core network130. In some examples, the wireless communication system100may comprise a long-range wireless communication network, that comprises, for example, a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communication system100may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof. As shown in the figure, examples of UEs115may include smart phones, automobiles or other vehicles, or drones or other aircraft. Another example of a UE may be a virtual reality appliance117, such as smart glasses, a virtual reality headset, an augmented reality headset, and other similar devices that may provide images, video, audio, touch sensation, taste, or smell sensation to a wearer. A UE, such as VR appliance117, may transmit or receive wireless signals with a RAN base station105via a long-range wireless link125, or the UE/VR appliance may receive or transmit wireless signals via a short-range wireless link137, which may comprise a wireless link with a UE device115, such as a Bluetooth link, a Wi-Fi link, and the like. A UE, such as appliance117, may simultaneously communicate via multiple wireless links, such as over a link125with a base station105and over a short-range wireless link. VR appliance117may also communicate with a wireless UE via a cable, or other wired connection. A RAN, or a component thereof, may be implemented by one or more computer components that may be described in reference toFIG.12.

Continuing with discussion ofFIG.1, base stations105may be dispersed throughout a geographic area to form the wireless communication system100and may be devices in different forms or having different capabilities. The base stations105and the UEs115may wirelessly communicate via one or more communication links125. Each base station105may provide a coverage area110over which UEs115and the base station105may establish one or more communication links125. Coverage area110may be an example of a geographic area over which a base station105and a UE115may support the communication of signals according to one or more radio access technologies.

Base stations105may communicate with the core network130, or with one another, or both. For example, base stations105may interface with core network130through one or more backhaul links120(e.g., via an S1, N2, N3, or other interface). Base stations105may communicate with one another over the backhaul links120(e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations105), or indirectly (e.g., via core network130), or both. In some examples, backhaul links120may comprise one or more wireless links.

One or more of base stations105described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (either of which may be referred to as a bNodeB or gNB), a Home NodeB, a Home eNodeB, or other suitable terminology.

In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (eg, an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by UEs115. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by UEs115via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology).

One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE115may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for a UE115may be restricted to one or more active BWPs.

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communication system100and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally, or alternatively, the smallest scheduling unit of the wireless communication system100may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs115with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs115with service subscriptions with the network provider or may provide restricted access to the UEs115having an association with the small cell (e.g., UEs115in a closed subscriber group (CSG), UEs115associated with users in a home or office). A base station105may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers.

In some examples, a UE115may also be able to communicate directly with other UEs115over a device-to-device (D2D) communication link135(e.g., using a peer-to-peer (P2P) or D2D protocol). Communication link135may comprise a sidelink communication link. One or more UEs115utilizing D2D communications, such as sidelink communication, may be within the geographic coverage area110of a base station105. Other UEs115in such a group may be outside the geographic coverage area110of a base station105or be otherwise unable to receive transmissions from a base station105. In some examples, groups of UEs115communicating via D2D communications may utilize a one-to-many (1:M) system in which a UE transmits to every other UE in the group. In some examples, a base station105facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs115without the involvement of a base station105.

In some systems, the D2D communication link135may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs115). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more RAN network nodes (e.g., base stations105) using vehicle-to-network (V2N) communications, or with both. InFIG.1, vehicle UE116is shown inside a RAN coverage area and vehicle UE118is shown outside the coverage area of the same RAN. Vehicle UE115wirelessly connected to the RAN may be a sidelink relay to in-RAN-coverage-range vehicle UE116or to out-of-RAN-coverage-range vehicle UE118.

The core network130may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. Core network130may be an evolved packet core (EPC) or 5G core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for UEs115that are served by the base stations105associated with core network130. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to IP services150for one or more network operators. IP services150may comprise access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service.

Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station105in a single beam direction (e.g., a direction associated with the receiving device, such as a UE115). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE115may receive one or more of the signals transmitted by a base station105in different directions and may report to the base station an indication of the signal that the UE115received with a highest signal quality or an otherwise acceptable signal quality.

Handover and mobility procedures facilitate service continuity over cellular networks. A handover may be implemented when a user equipment connected to a RAN (e.g., a RAN with which the UE has a currently established communication session, which may be referred to as a serving RAN or a source RAN) moves from coverage of a source RAN node to an adjacent RAN, which may be referred to herein as a target RAN. Moving from coverage of one RAN to coverage of another RAN may refer to a user equipment that is moving experiencing a decrease is signal strength with respect to a serving RAN while experiencing an increase in signal strength with respect to another RAN. A user equipment may be moving from coverage corresponding to a serving, or source, RAN while conducting an active network session with the serving RAN (e.g., while the UE is receiving or transmitting data). Thus, the source RAN node may trigger, initiate, implement, or otherwise cause a handover procedure such that the active and connected UE is handed over to being served by a target RAN, into the coverage of which the UE may be moving, and the communication session may resume via the target RAN to which the UE has been handed over.

Reduction of interruption delay related to handover is desirable to support seamless mobility and may be especially desirable for latency-critical applications running on, or being supported by, a user equipment device. A primary delay-contributing control step during handover according to conventional techniques is uplink timing advance (“TA”) acquisition. According to conventional techniques, timing advance acquisition typically includes a user equipment reading and blind-decoding basic system information blocks corresponding to a target RAN, subsequently transmitting an uplink preamble over determined access resources, and finally receiving a large configuration message (including uplink timing advance information) measured by the target RAN based responsive to receiving the transmitted preamble. Such timing advance acquisition according to conventional techniques comprises multiple instants of blind decoding and multiple transmission and reception operations by the user equipment, and typically leads to more than 20 millisecond of delay while a UE device acquires a timing advance to be used for a handover that has already been initiated.

During a handover process, according to existing techniques, a moving user equipment performs several radio procedures with respect to a target RAN node/cell before the UE can connect with the target RAN and be able to receive or transmit data with the target RAN. Radio procedures that a UE being handed over may perform include coverage and beam signal strength measurement, downlink synchronization, and acquisition of a timing advance, which may be used for synchronization in the uplink direction. TA acquisition typically causes about 15 millisecond to 20 millisecond of delay as previously mentioned. A primary contributor to handover delay results from during TA acquisition when a currently active communication session between a UE and serving RAN is halted for a UE that has a single radio transceiver chain because the radio circuitry of the UE is tuned to communicate with the target RAN, Such a deactivating, halting, stopping, etc. of a communication session may impose negative consequences with respect to latency and reliability for services that may have been using the communication session. A dual active protocol stack (“DAPS”) handover procedure, according to which a UE device having two different radio frequency radio chains can perform handover procedures with a target cell, such as acquiring a TA, while still receiving or transmitting traffic payload via an established and currently active communication session with a source RAN. However, a DAPS procedure is only useful for a multi-receiver device that can facilitate being connected to two RAN nodes at the same time. User equipment with at least two receiver chains can support simultaneous/dual-cell connections and can thus perform handover-completion steps with a target RAN while still receiving or transmitting traffic with a current serving RAN without experiencing significant handover interruption delay (e.g., in some cases, handover delay for a dual active UE may be almost 0 millisecond). However, for low-capability UE devices (e.g., a UE with a single receiver chain), handover interruption delay using conventional techniques typically causes perceptible disruption (e.g., by a user of a UE being handed over).

A handover procedure may be initiated upon occurrence of a triggering condition, which may be referred to as handover event. A handover criterion may be configured such that satisfaction of a handover criterion triggers a handover from a source cell to a target cell. An example of a handover criterion being satisfied may include a received coverage level (e.g., a signal strength of a reference signal received by a user equipment) corresponding to a serving cell falling below a configured coverage. Another example of a handover criterion being satisfied may include a received coverage level corresponding to an adjacent cell exceeding (e.g., being stronger, or higher) than a received coverage of the serving cell by an offset amount. Thus, user equipment devices typically are configured to regularly measure coverage levels from detected adjacent cells and report measured coverage levels to the RAN serving the UE to be used by the serving RAN to determine whether, or when, to hand over serving of the UE to a different RAN node.

Upon a serving RAN determining to handover a UE to a target RAN, using conventional techniques certain actions are typically performed, including the source/serving RAN transmitting a handover command to the UE and halting an established communication session between the source RAN and the UE. The source/serving RAN may then transmit a handover provisioning command to a target RAN via backhaul interface links to apprise the target RAN of the pending handover and to identify if there are any access restrictions corresponding to the target RAN/cell. The UE switches radio parameters from being tuned to communicate with the source RAN to being tuned to communication with the target RAN. Upon switching tuning of radio parameters, the UE typically performs actions before beginning communication via the target RAN. Actions that the UE typically performs during handover according to conventional techniques include measuring synchronization signal block (“SSB”) signal strength of the target RAN and determining a best available downlink beam and reading and decoding multiple available system information block (“SIB”) signal messages for determining access information corresponding to the target RAN. The UE then transmits an uplink preamble towards the target RAN for the target RAN to use in measuring a timing advance with respect to the UE. Finally, the UE reads and decodes an RRC configuration message received from the target RAN that typically includes a measured uplink timing advance as well as other access configuration information. The RRC configuration is typically a large file and is received over a long period (e.g., may causes a perceptible delay in traffic being communicated to or from the UE). Only after the UE has received the timing advance corresponding to the target RAN can the UE resume a communication session with the target RAN (now the current serving RAN), which session may have been halted by the previous serving RAN as part of the handover to the target RAN. During a handover according to existing techniques, a purpose of the UE determining a coverage level/signal strength and best available downlink beam, reading SIB messages, and transmitting a preamble is to obtain a timing advance corresponding to the target RAN to facilitate adjustment of the UE's control and/or data transmission timing to be aligned with the target RAN. However, the time required to perform those actions can takeover over 20 millisecond, a delay that may cause a violation of a critical latency budget corresponding to services or applications having a stringent Quality-of-Service.

Embodiments disclosed herein facilitate proactive/prospective timing advance acquisition. A current serving RAN and a potential target RAN may exchange configuration messages and messages comprising TA before a handover is initiated by a serving RAN, thus minimizing, or eliminating, communication session payload delivery delay due to acquiring uplink timing advance information during a handover period.

Embodiments disclosed herein facilitate reducing handover delay for user equipment having a single RF radio chain by TA acquisition being performed before a handover procedure is initiated. Using embodiments disclosed herein, a user equipment may acquire a TA of a target RAN before the handover is performed, thus avoiding delay that would otherwise be caused by TA acquisition performed during handover. To facilitate TA acquisition before a handover is initiated, a user equipment may be dynamically configured with TA acquisition timing resources, or TA time ‘gaps’, during which dynamic scheduling of traffic with the source RAN/cell is temporarily halted for devices to proactively participate in prospective measurement of one or more TA(s) corresponding to one or more potential target RAN nodes. Configured dynamic TA timing gaps can be scheduled, by a source RAN node's scheduler, such that a latency budget of ongoing payload transmission or reception is not violated, (e.g., a gap/period used for acquiring a TA corresponding to an adjacent cell is scheduled such that communication of payload of a current communication with the source RAN/cell is not impacted). A serving RAN may dynamically configure and schedule a TA acquisition timing gap for when there is an inter-packet-arrival-dormant period of a traffic flow corresponding to the UE that is larger than the scheduled TA acquisition timing gap. The TA acquisition timing gap may be referred to as a timing advance determining time resource. The TA acquisition timing gap may be referred to as a deactivated session resource period.

In an embodiment, a novel inter-cell coordination exchange procedure may be implemented to facilitate a serving RAN in receiving a proactively acquired, or prospectively acquired (e.g., acquired in anticipation of a handover but before a handover determination is made by a serving RAN or before the serving RAN initiates a handover), TA measurement of a user equipment device from an adjacent currently-non-serving RAN. By a potential target RAN transmitting a proactively/prospectively determined TA corresponding to a UE that may be handed over to the target RAN, a configured timing gap configured for a UE to cooperate with a potential target RAN in determining a TA and then the UE transmitting to the serving RAN is reduced because the UE can revert to the communication session with the serving RAN that was currently ongoing before being paused to determine the TA with the potential target RAN. A UE being served by a source RAN/cell may be configured with a timing gap long enough to transmit a novel uplink TA preamble towards one or more adjacent potential target RAN cells before reverting to the communication session with the current serving cell. Thus, the serving cell itself may obtain TA measurement results from the target cell(s), and accordingly, report the TA measurement(s) back to the configured UE devices. Accordingly, a serving RAN may transmit multiple TA measurement reports corresponding to multiple RAN nodes other than the serving RAN. As a result, when, and if, a user equipment device with respect to which one or more TA(s) has/have already been determined is configured for a handover, the UE may adopt a TA measurement corresponding to a target RAN and complete handover to a target RAN to which the TA corresponds without the typical delay of about 20 millisecond being used to obtain a TA during handover.

Using embodiments disclosed herein, novel RAN-to-RAN and RAN-to-UE signaling procedures facilitate user equipment devices acquiring a timing advance proactively/prospectively before a handover is initiated, thus eliminating delay caused by TA acquisition while communication with a serving RAN has been halted during handover. Adjacent RAN nodes may coordinate (e.g., share) via Xn/backhaul links a configured group of special preambles and resource occasions dedicated to proactive/prospective TA acquisition. Receiving by a source/serving RAN of a signal strength measurement report from an active UE device may be indicative of a received coverage level corresponding to the serving RAN being degraded and/or may be indicative that a received coverage level corresponding to one or more adjacent RAN nodes, which may be referred to as target RAN nodes or potential target RAN nodes (potential in the sense that the serving RAN may not have determined to hand over the UE to a given potential target RAN yet), is better than coverage corresponding to the currently serving/source RAN. Such indication may be analyzed by the serving RAN to determine that a received signal strength satisfies a first handover criterion, wherein satisfying the first handover criterion may trigger the serving RAN to transmit a measurement request message. A measurement request message may be referred to as a pre-handover measurement indication, to the user equipment to perform a proactive/prospective TA measurement corresponding to a potential target RAN.

Via the pre-handover measurement indication, the current serving RAN can dynamically configure the UE device with the TA acquisition preambles and transmission resources to be used to prospectively determine a TA corresponding to a potential target RAN with respect to the UE. The pre-handover measurement indication may comprise a frequency resource and a timing advance resource ‘gap’, or period, during which a UE is to switch radio parameters to be tuned to communicate with a potential target RAN and transmit a special TA preamble toward a target RAN. Thus, during a configured TA timing gap, a UE may switch radio parameters from being tuned to communicate with a serving/source RAN to being tuned to communicate with a potential target RAN and immediately transmit a configured TA preamble via a configured frequency resource during the TA timing gap. A TA preamble configuration transmitted from a serving/source RAN to a UE may comprise system information block information and synchronization signal block information corresponding to the potential target RAN, thus facilitating a UE in avoiding having to read system information blocks and synchronization signal blocks of a potential target RAN, since the UE has already been configured with the TA acquisition preamble and its respective transmission resources by the source RAN/cell. Accordingly, a UE does not have to read and decode SSB signals or SIB messages for purposes of transmitting a TA preamble because the UE already has been configured by a current serving RAN with a TA preamble and timing and frequency resources to be used by the UE to transmit a TA request message to a potential target RAN.

Because a UE may be configured with a TA preamble and corresponding timing gap and frequency resources to use to transmit the TA preamble, the configured timing gap during which the UE switches from a source RAN to a target RAN can be very short due to the UE performing minimal actions and not having to blindly decode SSB signals and SIB messages before switching back to the source RAN. Although the UE may switch from communication with a source RAN to communication with a target RAN during a TA gap, the TA gap may be reduced compared to the 20 millisecond delay typically used to obtain a TA while a UE is not connected with the source RAN during a handover according to conventional techniques. Furthermore, a scheduler at the serving RAN may schedule the TA gap to occur when there is no scheduled traffic to or from the UE such that even the smaller amount of time to determine a TA during a configured TA gap has minimal, or no, negative impact on ongoing traffic flows of a communication session between the UE and the source RAN.

Turning now toFIG.2, the figure illustrates environment200where a user equipment115is traveling direction215at position1. The user equipment115may be within signal range210A corresponding to serving ran105A and at the edge of signal range210C corresponding to radio access node105C. In position2, user equipment115may have moved outside of signal range210C and may now be located at the periphery, or edge, of range210A and also at the periphery of range210B corresponding to node105B. User equipment115may regularly report signal strength information205corresponding to radio access network nodes from which it can detect reference signals in a signal strength information message via a communication session201that may be established via an established radio connection between the user equipment and radio access node105A.

Serving radio access network node105A may determine to transmit a timing advance preamble220B to radio access node105B and a timing advance preamble220C to radio access node105C via Xn backhaul links203AB and in203AC, respectively. Preambles220B and220C may be transmitted to UE115in a timing advance acquisition configuration1200(described in reference toFIG.12). Upon determining that user equipment115is moving away from radio access node105A and toward radio access network node105B (e.g., the UE is moving in direction215), radio access network node105A may determine that a timing advance corresponding to radio access network105B should be determined with respect to the UE, even before radio access network node105A may determine to initiate a handover of the user equipment from radio access network node105A to radio access network node105B. The determination to instruct the user equipment115to cooperate with radio access network node105B to determine a timing advance corresponding to radio access network105B with respect to the user equipment may be based on a signal strength205B2being stronger than a signal strength205C2and also based on the signal strength205B2being stronger than a signal strength corresponding to the connection with RAN105A being used to carry communication session201. After a timing advance corresponding to radio access network node105B has been determined with respect to the user equipment, when user equipment115is at position3,105A radio access network node may determine to initiate a handover of user equipment115to radio access network node105B, for example, based on signal strength205B3being stronger than signal strengths205A3or205C3, and the user equipment may use the timing advance determined before radio access network node105A initiated the handover to facilitate the handover.

Different embodiments may facilitate a UE in obtaining a TA, which may be referred to as a TA measurement, or a TA report. In embodiment environment300shown inFIG.3A, a source RAN105A may transmit to UE115, moving in direction215, a pre-handover measurement indication message305. Pre-handover measurement indication message305may be transmitted via session201via first connection202. Pre-handover measurement indication message305may comprise a configuration120described in reference toFIG.12and may be indicative to the user equipment that the user equipment is to receive, from potential target radio access network node105B responsive to the UE transmitting a timing advance determination request message310, a TA corresponding to the potential target RAN during a configured TA gap325, as shown inFIG.3B. Timing advance determination request message310may request determining, by the potential target RAN, a determined timing advance with respect to UE115.

After transmitting a timing advance determination request message310to potential target RAN105B during TA gap325, UE115may wait, during the TA gap, to receive a TA316, or a determined TA, from potential target RAN105B in a TA message315from the potential target RAN105B responsive to the timing advance determination request message. TA message315received by the UE may comprise a measured uplink TA level, determined by the potential target RAN, in terms of milliseconds, subframes, or symbols, for example.

In another embodiment, in environment301shown inFIG.3C, instead of waiting to receive a TA message315from a potential target RAN, UE115may be configured, according to a pre-handover measurement indication306, to switch, tune, or otherwise adjust, radio parameters back to being adjusted to communicate with the source/serving RAN105A after transmitting a timing advance determination request message310instead of waiting to receive a determined TA316in a TA message315from the potential target RAN before switching back to radio parameters that facilitate communication with the source/serving RAN105A. The measured TA316may be transmitted to, and received by, source RAN105A, in a TA report message317. Source RAN105A may then transmit/report the TA316determined by potential target RAN105B to UE115in a TA message319as part of communication session201with the UE that may have been established before the UE transmitted the timing advance determination request message during TA gap335. TA message319may comprise a downlink control information comprising information according to format1300described in reference toFIG.13.

As can be seen inFIG.3BandFIG.3C, TA gap325is shown inFIG.3Bas being longer than TA gap335shown inFIG.3Cto illustrate a reduction in TA gap length that may result from configuring UE115to transmit a TA determining request message310and then switching back to resume communication with source RAN105A via communication session201instead of waiting to receive a TA316from RAN105B. The ‘X’ that illustrates a halting of communication session201is shown larger inFIG.3Bthan inFIG.3Cto indicate that session201is deactivated for a shorter period in the embodiment shown inFIG.3Cthan in the embodiment shown inFIG.3B. The embodiment shown inFIG.3Bthus implements a longer duration timing advance gap325than timing advance gap335shown inFIG.3C, but the embodiment shown inFIG.3Bdoes not use inter-RAN coordination via backhaul links. The embodiment shown inFIG.3Cmay facilitate a faster device switching time since source RAN105A receives the TA measurement report315from target RAN105B but uses inter-RAN messaging via backhaul links.

Regardless of which embodiment shown in eitherFIG.3BorFIG.3Cis used to deliver TA316to UE115to use during a handover, when serving RAN105A determines to initiate a handover of UE115to RAN105B, RAN105A transmits to UE115a handover indication330message as shown inFIG.3D. Handover indication message330may comprise TA message319(described in reference toFIG.3C) or the TA message may comprise the handover indication. Responsive to receiving handover indication330, UE115may transmit TA315to RAN105B via a handover initiation message340to perform a handover. Handover duration345is illustrated inFIG.3Dtaking much less time than either TA gap325shown inFIG.3Bor timing gap335shown inFIG.3C. Thus, connection202between RAN105A and UE115is deactivated and second connection342between RAN105B and UE115is almost immediately (e.g., imperceptible to a user of the UE) established with RAN105B as the UE's new serving RAN and the UE may resume, with RAN105B, communication session201that was previously being conducted with RAN105A via first connection202with minimal delay because TA acquisition during handover is avoided. It will be appreciated that RAN105A may schedule either TA gap325or335to occur during a dormant period during which no traffic is scheduled to be communicated between UE115and RAN105A such that session201is not impacted while the UE is cooperating with RAN105B in determining a TA316corresponding to RAN105B during a timing advance gap.

Turning now toFIG.12, the figure illustrates a proactive/prospective timing advance acquisition configuration1200. Via configuration1200, a source RAN may configure an active/connected user equipment device with proactive/prospective TA acquisition information, that may comprise a target RAN/cell identifier105indicative of a target cell RAN with which the UE is to cooperate to prospectively measure and report a TA. The target RAN/cell identifier105may be indicative of a RAN that is one of a group of RAN nodes, determined by a serving RAN node, based on being adjacent to, or a neighbor to, the source RAN/cell that a UE may be likely to report as providing a best signal strength. (An adjacent or neighbor RAN node may be referred to as a surrounding RAN node.) For each target RAN/cell indicated by an indication105, configuration1200may comprise a corresponding TA preamble220, or preamble identifier, that may comprise an index or explicit information of a special TA uplink preamble to be used to trigger prospective TA determination at a RAN105corresponding to the preamble identifier220in configuration1200. It will be appreciated that a neighbor RAN may have already received a preamble220from a serving RAN as described in reference toFIG.2.

Configuration1200may also comprise measurement gap information1215that may comprise timing and frequency resources via which a user equipment should transmit a corresponding TA preamble220towards the target RAN/cell. During the TA gap/timing period to be used to measure a TA corresponding to a RAN identified by a corresponding identifier105with respect to the UE, a currently established communication session between the UE and the serving RAN will be halted (e.g., a time gap is a period during which resources for the communication session are not to be scheduled for the UE by the serving RAN).

Configuration1200may comprise a TA acquisition mode indication1220to be indicative to a user equipment of a mode by which the user equipment is to receive a TA measured by a RAN identified by a corresponding identifier105. For example, TA acquisition mode indication1220may be indicative that a UE is to receive a TA from a target RAN105conducting a measurement of a TA (e.g., the embodiment shown inFIG.3B). In another example, a TA acquisition mode indication1220may be indicative to a UE that the source RAN/cell will receive a measured TA from a target RAN via backhaul interface link and that the source RAN will transmit the TA to the UE (e.g., the embodiment shown inFIG.3C). If the mode indicated in indication1220is for the serving RAN to transmit the TA to the UE, based on the mode indication, the UE may only transmit a configured TA preamble to a potential target RAN and may immediately switch back to the source RAN and resume an ongoing session therewith without waiting for the TA measurement report from the target RAN.

In case the TA acquisition mode indication1220indicates that the source RAN is to receive a TA measurement report from a target RAN, the source RAN may transmit a TA measurement report request to a target RAN after a corresponding TA measurement period/duration gap expires. The TA measurement report request may indicate a TA preamble identifier or index for which the TA measurement reporting is being requested. The target RAN may respond back with a measured proactive/prospective TA measurement level that corresponds to the signaled preamble identifier received from the source RAN. The source/serving RAN, after collecting a proactive/prospective TA measurement report from an adjacent cell, may transmit a measured/determined TA to a UE, via an RRC signaling message (e.g., message1300shown inFIG.13), that is to be handed over towards the target RAN to which the measured/determined TA corresponds. Message1300may comprise TA315B corresponding to RAN105B or TA315C corresponding to RAN105C (shown inFIG.1).

FIG.4illustrates a timing diagram of an example embodiment method400. At act405, WTRU115may compile and transmit a reference signal measurement report indicative of signal strengths corresponding to serving RAN105A and neighboring RAN nodes105B to the serving RAN node. At act410, UE/WTRU115may receive a proactive/prospective timing advance measurement request and TA configurations (e.g., configuration1200shown inFIG.12) from serving RAN105A. A TA configuration may comprise (1) one or more target cell identifiers for which the TA is to be measured, (2) one or more TA measurement gap(s) associated with each indicated target RAN identifier, (3) one or more random access preambles (“RACH”), or indexes corresponding thereto, to be used for prospective/proactive TA acquisition, and (4) TA acquisition mode indication (e.g., to indicate that either the serving RAN is to acquire a TA determined with respect to UE115from one or more target RAN(s), or that the UE is to acquire a TA using RRC signaling from a respective indicated target RAN).

For each target RAN indicated for TA measurement/determination, UE115may transmit, at act415, the indicated RACH preamble(s) via resource occasion(s), configured with respect to target RAN(s), during the configured TA measurement gap period(s). On condition of a configured mode indication indicating that UE115is to receive a determined TA from the potential target RAN(s) that determined the TA(s), at act420UE115may receive a TA(s) via radio RRC signaling from the target RAN(s) (e.g., from currently non-serving RANs). On condition of a configured mode indication being indicative that a target RAN is to transmit a TA determined with respect to UE115to the current serving RAN105A, RAN105B transmits, at act425, a TA determined with respect to UE115to RAN105A. At act430, UE115may receive a TA, corresponding to RAN105B and determined with respect to the UE, from current serving RAN105A via MAC CE signaling or control channel signaling.

FIG.5illustrates a timing diagram of an example embodiment500. At act505, serving RAN105A and potential target RAN105B determining and exchange prospective/proactive TA acquisition configurations, that may comprise RACH preambles220(described in reference toFIG.2), or RACH indications/indexes, via a backhaul link/Xn interface. A RACH preamble220, or indication thereof, may be specific to UE115and may be dedicated for proactive/prospective TA acquisition. A RACH preamble220, or indication thereof, may be specific to RAN105B and may be dedicated for proactive/prospective TA acquisition. At act510, serving RAN node105A receives reference signal measurement report(s) from UE115corresponding to serving RAN105A and corresponding to neighboring RANs, including RAN105B. On condition of a reported coverage level received from UE115corresponding to adjacent RAN105B exceeding, for example, a predefined coverage threshold, or, for example, being larger than a reported coverage level corresponding to RAN102A by a preconfigured amount, RAN node105A may transmit at act515a proactive/prospective TA measurement request that may comprise a configuration (e.g., configuration1200described in reference toFIG.12) to UE115. A TA measurement request or configuration may include (1) one or more target RAN identifiers, including RAN105B, for which a TA to be measured, (2) one or more TA measurement gap(s) associated with each indicated target RAN identifier, (3) RACH preamble, or RACH index, to be used for prospective/proactive TA acquisition, and (4) TA acquisition mode indication. At act520, UE115transmits a RACH corresponding, in the configuration received at act515to RAN105B, to RAN105B.

On condition of a configured TA acquisition mode indication indicative of RAN105A receiving a TA corresponding to RAN105B from RAN105B, at act525RAN node105A receives a measured TA from, for example, each of the configured target (adjacent) RANs indicated in the configuration received at act515, including a TA corresponding to RAN105B determined with respect to UE115B. At act530RAN node105A transmits to UE115the determined TA measurement corresponding to RAN105B received at act525as part of either a handover command (e.g., via RRC signaling), or via downlink control information (e.g., via DCI signaling).

FIG.6illustrates a flow diagram of an example embodiment method600. Method600begins at act605. At act610, an active mode user equipment may measure a signal strength of a reference signal and transmit at act615a value corresponding to the measured signal strength to a radio access network node serving the user equipment. At act620, the serving radio access network node may receive the signal strength value transmitted at act615and determine whether the signal strength value satisfies a first handover criterion. The first handover criterion may be used by the serving radio access network node to determine whether to request that the user equipment perform a prospective timing advance determination procedure before the serving radio access network node determines whether to hand over serving of the user equipment to another radio access network node. For example, if the signal strength value received at act615indicates that the radio access network node to which the received signal strength value corresponds is a stronger signal strength than a signal strength value, determined by the user equipment, that corresponds to the serving radio access network node itself, method600may advance to act625. If a determination is made that the first handover criterion is not met at act625, method600returns to act610.

Returning to description of act625, the serving radio access network node may transmit, via backhaul communication links, to surrounding, adjacent, or neighboring radio access network nodes a timing advance preambles, for example preambles220described in reference toFIG.2. The timing advance preambles may be special preambles respectively corresponding to the surrounding radio access network nodes. The timing advance preambles may be indicative to the one or more of the surrounding radio access network nodes that if a timing advance request is received from a user equipment that comprises a timing advance preamble corresponding to the respective radio access network node, the radio access network node is to perform, in cooperation with the user equipment, a determination of a timing advance corresponding to the radio access node with respect to the user equipment.

At act630, the serving radio access network node may transmit to the user equipment a timing advance measurement request message that may indicate one or more of the surrounding radio access network nodes with respect to one or more of which a timing advance is to be determined. The timing advance measurement request transmitted at act630to the user equipment may comprise a timing advance preamble corresponding to the one or more radio access network nodes. At act635, the serving radio access network node may suspend resources corresponding to a current communication session that is active with the user equipment. At act640, the user equipment may transmit one or more of the timing advance preambles transmitted at act630in the timing advance measurement request to one or more surrounding nodes corresponding to the preambles. The user equipment may transmit the one or more timing advance preambles during a timing advance gap during which resources corresponding to the current communication session that were suspended at act635remain suspended.

In an embodiment, upon transmitting the timing advance preambles to respective radio access network nodes at act640, the user equipment may resume the communication session with the serving radio access network node according to the resources that were suspended at act635and that remained suspended during the timing advance gap. Thus, the timing advance gap may be configured to be just long enough for the user equipment to transmit the timing advance preamble, or timing advance preambles, to the one or more surrounding radio access network nodes without waiting to receive back one or more timing advance values from the surrounding radio access network nodes to which the user equipment may have been instructed to transmit the preambles (via the timing advance measurement request transmitted to the user equipment at act630). Instead, at act645, the serving radio access network node may receive from the one or more surrounding radio access network nodes one or more determined timing advance(s) corresponding to the respective one or more surrounding nodes with respect to the user equipment.

However, in another embodiment, the timing advance measurement request transmitted to the user equipment at act630may have configured a timing advance gap of a long enough period (e.g., resources with a serving RAN being used for a current communication are suspended long enough) for the user equipment to not only transmit the one or more timing advance preambles to the corresponding surrounding radio access network nodes using different resources but also long enough for a determination of a timing advance corresponding to the one or more surrounding radio access network nodes to be determined and transmitted back to the user equipment. Accordingly, the surrounding radio access network nodes that determine the timing advance with respect to the user equipment may transmit corresponding timing advance values (e.g., corresponding to a given RAN with respect to the user equipment) to the user equipment during a configured timing advance gap.

At act650, the serving radio network node may determine whether a signal strength corresponding to the serving radio access network node or one of the surrounding radio access network nodes satisfies a second handover criterion. The second handover criterion may be used by the serving radio access network node to determine whether to initiate handover of the user equipment to one of the surrounding radio access network nodes corresponding to which a timing advance has already been determined. For example, if the user equipment has been moving during a period during which acts625through645were performed, and a signal strength corresponding to one of the surrounding radio access nodes is determined to be even stronger than a signal strength determination that was made at act620corresponding to the same surrounding node, a serving radio access network node may determine to hand over the user equipment to the surrounding radio access network node corresponding to the stronger signal strength. If a determination is made at act650that a most-recently-received signal strength does not satisfy a second hand over criterion method600may return to act650.

Continuing with description at act650, if a determination is made that a received signal strength corresponding to a surrounding radio access network node satisfies the second handover criterion, method600advances to act655. At act655, the serving radio access network node may transmit to the user equipment a handover request message that may comprise the timing advance received from the surrounding radio access network node at act645. If the surrounding radio access network node was configured to transmit the timing advance corresponding thereto to the user equipment, the handover request message transmitted to the user equipment at act655may not include the timing advance corresponding to the surrounding radio access network node to which the user equipment is to be handed over because the user equipment may have already received the timing advance from the surrounding radio access network node to which it is being handed over. At act660, the user equipment uses the timing advance, either received at act655or received directly from the surrounding radio access network node that transmitted the timing advance in response to receiving the timing advance preamble at act640, to perform handover to the surrounding radio access network node. At act665, the user equipment and the target surrounding radio access network node to which the user equipment was handed over begin operation via a connection therebetween of a communication session that had been active with the previous serving radio access network node via a connection between the previous serving radio access network node and the user equipment. Method600advances from act665to act670and ends.

Turning now toFIG.7, the figure illustrates an example embodiment method700comprising at block705establishing, by a first radio access network node comprising a processor, a communication session with a user equipment via a first connection between the first radio access network node and the user equipment; at block710receiving, by the first radio access network node from the user equipment, a first signal strength indication indicative of a first determined signal strength, corresponding to a second radio access network node, determined by the user equipment; at block715analyzing, by the first radio access network node, the first determined signal strength with respect to a first handover criterion resulting in an analyzed first determined signal strength; at block720based on the analyzed first determined signal strength being determined to satisfy the first handover criterion, transmitting, by the first radio access network node to the user equipment, a pre-handover measurement indication to be indicative to the user equipment to transmit to the second radio access network node a timing advance determination request message requesting determining, by the second radio access network node, a determined timing advance with respect to the user equipment; at block725receiving, by the first radio access network node from the user equipment, a second signal strength indication indicative of a second determined signal strength, corresponding to the second radio access network node, determined by the user equipment; at block730analyzing, by the first radio access network node, the second determined signal strength with respect to a second handover criterion resulting in an analyzed second determined signal strength; at block735based on the analyzed second determined signal strength being determined to satisfy the second handover criterion, determining, by the first radio access network node, to handover the communication session to the second radio access network node; and at block740transmitting, by the first radio access network node to the user equipment, a handover indication to be indicative to the user equipment to establish, using the determined timing advance, a second connection between the second radio access network node and the user equipment.

Turning now toFIG.8, the figure illustrates an example first radio access network node, comprising at block805a processor configured to receive, from a user equipment, a timing advance preamble indicative of a request for a determination of a timing advance, corresponding to the first radio access network node with respect to the user equipment; at block810determine the timing advance corresponding to the first radio access network node with respect to the user equipment; at block815wherein the timing advance is to be used by the user equipment when conducting a handover from a second radio access network node to the first radio access network node, and wherein the first radio access network node determines the timing advance before the handover from the second radio access network node to the first radio access network node is initiated by the second radio access network node; at block820receive, from the second radio access network node the timing advance preamble; at block825responsive to receiving the timing advance preamble from the user equipment, analyze the timing advance preamble received from the user equipment with respect to the timing advance preamble received in the timing advance acquisition configuration to result in an analyzed timing advance preamble; and at block830wherein the first radio access network node determines the timing advance responsive to the analyzed timing advance preamble being the same as the timing advance preamble received from the second radio access network node.

Turning now toFIG.9, the figure illustrates a non-transitory machine-readable medium900comprising at block905executable instructions that, when executed by a processor of a first radio access network node, facilitate performance of operations, comprising establishing a communication session with a user equipment; at block910transmitting, to a second radio access network node, a timing advance preamble to be indicative to the second radio access network node to determine a timing advance corresponding to the second radio access network node with respect to the user equipment upon receiving, from the user equipment, a timing advance determination request message comprising the timing advance preamble; at block915transmitting, to the user equipment, a pre-handover measurement indication indicative to the user equipment to transmit to the second radio access network node the timing advance determination request message requesting, from the second radio access network node, the timing advance corresponding to the second radio access network node with respect to the user equipment; and at block920wherein the pre-handover measurement indication is indicative to the user equipment of a deactivated session resource period, wherein the deactivated session resource period is to correspond to a period during which a resource used for the communication session is to be deactivated with respect to the user equipment, and wherein the pre-handover measurement indication is indicative to the user equipment to transmit to the second radio access network node the timing advance determination request message during the deactivated session resource period.

In order to provide additional context for various embodiments described herein,FIG.10and the following discussion are intended to provide a brief, general description of a suitable computing environment1000in which various embodiments of the embodiment described herein can be implemented. While embodiments have been described above in the general context of computer-executable instructions that can run on one or more computers, those skilled in the art will recognize that the embodiments can be also implemented in combination with other program modules and/or as a combination of hardware and software.

Turning now toFIG.11, the figure illustrates a block diagram of an example UE1160. UE1160may comprise a smart phone, a wireless tablet, a laptop computer with wireless capability, a wearable device, a machine device that may facilitate vehicle telematics, and the like. UE1160comprises a first processor1130, a second processor1132, and a shared memory1134. UE1160includes radio front end circuitry1162, which may be referred to herein as a transceiver, but is understood to typically include transceiver circuitry, separate filters, and separate antennas for facilitating transmission and receiving of signals over a wireless link, such as one or more wireless links125,135, or137shown inFIG.1. Furthermore, transceiver1162may comprise multiple sets of circuitry or may be tunable to accommodate different frequency ranges, different modulations schemes, or different communication protocols, to facilitate long-range wireless links such as links, device-to-device links, such as links135, and short-range wireless links, such as links137.

Continuing with description ofFIG.11, UE1160may also include a SIM1164, or a SIM profile, which may comprise information stored in a memory (memory34or a separate memory portion), for facilitating wireless communication with RAN105or core network130shown inFIG.1.FIG.11shows SIM1164as a single component in the shape of a conventional SIM card, but it will be appreciated that SIM1164may represent multiple SIM cards, multiple SIM profiles, or multiple eSIMs, some or all of which may be implemented in hardware or software. It will be appreciated that a SIM profile may comprise information such as security credentials (e.g., encryption keys, values that may be used to generate encryption keys, or shared values that are shared between SIM1164and another device, which may be a component of RAN105or core network130shown inFIG.1). A SIM profile1164may also comprise identifying information that is unique to the SIM, or SIM profile, such as, for example, an International Mobile Subscriber Identity (“IMSI”) or information that may make up an IMSI.

SIM1164is shown coupled to both the first processor portion1130and the second processor portion1132. Such an implementation may provide an advantage that first processor portion30may not need to request or receive information or data from SIM1164that second processor1132may request, thus eliminating the use of the first processor acting as a ‘go-between’ when the second processor uses information from the SIM in performing its functions and in executing applications. First processor1130, which may be a modem processor or baseband processor, is shown smaller than processor1132, which may be a more sophisticated application processor, to visually indicate the relative levels of sophistication (i.e., processing capability and performance) and corresponding relative levels of operating power consumption levels between the two processor portions. Keeping the second processor portion1132asleep/inactive/in a low power state when UE1160does not need it for executing applications and processing data related to an application provides an advantage of reducing power consumption when the UE only needs to use the first processor portion1130while in listening mode for monitoring routine configured bearer management and mobility management/maintenance procedures, or for monitoring search spaces that the UE has been configured to monitor while the second processor portion remains inactive/asleep.

UE1160may also include sensors1166, such as, for example, temperature sensors, accelerometers, gyroscopes, barometers, moisture sensors, and the like that may provide signals to the first processor1130or second processor1132. Output devices1168may comprise, for example, one or more visual displays (e.g., computer monitors, VR appliances, and the like), acoustic transducers, such as speakers or microphones, vibration components, and the like. Output devices1168may comprise software that interfaces with output devices, for example, visual displays, speakers, microphones, touch sensation devices, smell or taste devices, and the like, that are external to UE1160.

The following glossary of terms given in Table 1 may apply to one or more descriptions of embodiments disclosed herein.