WO2021253399A1

WO2021253399A1 - History based cell handover for small cells

Info

Publication number: WO2021253399A1
Application number: PCT/CN2020/097097
Authority: WO
Inventors: Li Tan; Chaofeng HUI; Meng Liu
Original assignee: Qualcomm Incorporated
Priority date: 2020-06-19
Filing date: 2020-06-19
Publication date: 2021-12-23

Abstract

In one aspect, a method of wireless communication includes receiving, by a network entity, a handover request message from a second network entity, the handover request message including cell history information for a user equipment (UE). The method also includes receiving, by the network entity, a measurement report message from the UE. The method includes determining, by the network entity, to perform a handover operation for the UE based on the cell history information and the measurement report message. The method further includes transmitting, by the network entity, a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information. Other aspects and features are also claimed and described.

Description

HISTORY BASED CELL HANDOVER FOR SMALL CELLS

TECHNICAL FIELD

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to cell handover operations. Certain embodiments of the technology discussed below can enable and provide enhanced cell attachment for mobile user devices.

INTRODUCTION

Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources.

A wireless communication network may include a number of base stations or node Bs that can support communication for a number of user equipments (UEs) . A UE may communicate with a base station via downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.

A base station may transmit data and control information on the downlink to a UE and/or may receive data and control information on the uplink from the UE. On the downlink, a transmission from the base station may encounter interference due to transmissions from neighbor base stations or from other wireless radio frequency (RF) transmitters. On the uplink, a transmission from the UE may encounter interference from uplink transmissions of other UEs communicating with the neighbor base stations or from other wireless RF transmitters. This interference may degrade performance on both the downlink and uplink.

As the demand for mobile broadband access continues to increase, the possibilities of interference and congested networks grows with more UEs accessing the long-range wireless communication networks and more short-range wireless systems being deployed in communities. Research and development continue to advance wireless technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.

BRIEF SUMMARY OF SOME EMBODIMENTS

The following summarizes some aspects of the present disclosure to provide a basic understanding of the discussed technology. This summary is not an extensive overview of all contemplated features of the disclosure and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.

In one aspect of the disclosure, a method of wireless communication includes transmitting, by a user equipment (UE) , a measurement report message to a first network entity; receiving, by the UE, a RRC connection reconfiguration message from the first network entity, the RRC connection reconfiguration message generated based on cell history information for the UE and the measurement report message; and transmitting, by the UE, a RRC connection reconfiguration complete message to a second network entity.

In an additional aspect of the disclosure, an apparatus configured for wireless communication is disclosed. The apparatus includes at least one processor, and a memory coupled to the processor. The processor is configured to transmit, by a user equipment (UE) , a measurement report message to a first network entity; receive, by the UE, a RRC connection reconfiguration message from the first network entity, the RRC connection reconfiguration message generated based on cell history information for the UE and the measurement report message; and transmit, by the UE, a RRC connection reconfiguration complete message to a second network entity.

In another aspect of the disclosure, a method of wireless communication includes receiving, by a network entity, a handover request message from a second network entity, the handover request message including cell history information for a user equipment (UE) ; receiving, by the network entity, a measurement report message from the UE; determining, by the network entity, to perform a handover operation for the UE based on the cell history information and the measurement report message; and transmitting, by the network entity, a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information.

In an additional aspect of the disclosure, an apparatus configured for wireless communication is disclosed. The apparatus includes at least one processor, and a memory coupled to the processor. The processor is configured to receive, by a network entity, a handover request message from a second network entity, the handover request message including cell history information for a user equipment (UE) ; receive, by the network entity, a measurement report message from the UE; determine, by the network entity, to perform a handover operation for the UE based on the cell history information and the measurement report message; and transmit, by the network entity, a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information.

Other aspects, features, and embodiments will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments in conjunction with the accompanying figures. While features may be discussed relative to certain embodiments and figures below, all embodiments can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments the exemplary embodiments can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the present disclosure may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

FIG. 1 is a block diagram illustrating details of a wireless communication system according to some embodiments of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of a base station and a UE configured according to some embodiments of the present disclosure.

FIG. 3A is an example diagram illustrating a mobile device moving through a number of cells and respective cell coverage areas.

FIG. 3B is an example diagram illustrating cell attachment times for the mobile device of FIG. 3A.

FIG. 3C is an example of a ladder diagram illustrating handover operations for the mobile device of FIG. 3A according to some embodiments of the present disclosure.

FIG. 4 is a block diagram illustrating an example of a wireless communications system (with a UE and base stations) with cell history based handover determination operations.

FIG. 5 is a diagram of an example of a ladder diagram of illustrating history based handover operations according to some embodiments of the present disclosure.

FIG. 6 is a flow diagram illustrating example blocks executed by a UE configured according to an aspect of the present disclosure.

FIG. 7 is a flow diagram illustrating example blocks executed by a base station configured according to an aspect of the present disclosure.

FIG. 8 is a block diagram conceptually illustrating a design of a UE configured to perform precoding information update operations according to some embodiments of the present disclosure.

FIG. 9 is a block diagram conceptually illustrating a design of a base station configured to perform precoding information update operations according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to limit the scope of the disclosure. Rather, the detailed description includes specific details for the purpose of providing a thorough understanding of the inventive subject matter. It will be apparent to those skilled in the art that these specific details are not required in every case and that, in some instances, well-known structures and components are shown in block diagram form for clarity of presentation.

This disclosure relates generally to providing or participating in communication as between two or more wireless devices in one or more wireless communications systems, also referred to as wireless communications networks. In various embodiments, the techniques and apparatus may be used for wireless communication networks such as code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, single-carrier FDMA (SC-FDMA) networks, LTE networks, GSM networks, 5 ^th Generation (5G) or new radio (NR) networks (sometimes referred to as “5G NR” networks/systems/devices) , as well as other communications networks. As described herein, the terms “networks” and “systems” may be used interchangeably.

A CDMA network, for example, may implement a radio technology such as universal terrestrial radio access (UTRA) , cdma2000, and the like. UTRA includes wideband-CDMA (W-CDMA) and low chip rate (LCR) . CDMA2000 covers IS-2000, IS-95, and IS-856 standards.

A TDMA network may, for example implement a radio technology such as GSM. 3GPP defines standards for the GSM EDGE (enhanced data rates for GSM evolution) radio access network (RAN) , also denoted as GERAN. GERAN is the radio component of GSM/EDGE, together with the network that joins the base stations (for example, the Ater and Abis interfaces) and the base station controllers (A interfaces, etc. ) . The radio access network represents a component of a GSM network, through which phone calls and packet data are routed from and to the public switched telephone network (PSTN) and Internet to and from subscriber handsets, also known as user terminals or user equipments (UEs) . A mobile phone operator's network may comprise one or more GERANs, which may be coupled with Universal Terrestrial Radio Access Networks (UTRANs) in the case of a UMTS/GSM network. An operator network may also include one or more LTE networks, and/or one or more other networks. The various different network types may use different radio access technologies (RATs) and radio access networks (RANs) .

An OFDMA network may implement a radio technology such as evolved UTRA (E-UTRA) , IEEE 802.11, IEEE 802.16, IEEE 802.20, flash-OFDM and the like. UTRA, E-UTRA, and Global System for Mobile Communications (GSM) are part of universal mobile telecommunication system (UMTS) . In particular, long term evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents provided from an organization named “3rd Generation Partnership Project” (3GPP) , and cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . These various radio technologies and standards are known or are being developed. For example, the 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations that aims to define a globally applicable third generation (3G) mobile phone specification. 3GPP long term evolution (LTE) is a 3GPP project which was aimed at improving the universal mobile telecommunications system (UMTS) mobile phone standard. The 3GPP may define specifications for the next generation of mobile networks, mobile systems, and mobile devices. The present disclosure is concerned with the evolution of wireless technologies from LTE, 4G, 5G, NR, and beyond with shared access to wireless spectrum between networks using a collection of new and different radio access technologies or radio air interfaces.

5G networks contemplate diverse deployments, diverse spectrum, and diverse services and devices that may be implemented using an OFDM-based unified, air interface. To achieve these goals, further enhancements to LTE and LTE-A are considered in addition to development of the new radio technology for 5G NR networks. The 5G NR will be capable of scaling to provide coverage (1) to a massive Internet of things (IoTs) with an ultra-high density (e.g., ～1M nodes/km ²) , ultra-low complexity (e.g., ～10s of bits/sec) , ultra-low energy (e.g., ～10+ years of battery life) , and deep coverage with the capability to reach challenging locations; (2) including mission-critical control with strong security to safeguard sensitive personal, financial, or classified information, ultra-high reliability (e.g., ～99.9999%reliability) , ultra-low latency (e.g., ～ 1 ms) , and users with wide ranges of mobility or lack thereof; and (3) with enhanced mobile broadband including extreme high capacity (e.g., ～ 10 Tbps/km ²) , extreme data rates (e.g., multi-Gbps rate, 100+ Mbps user experienced rates) , and deep awareness with advanced discovery and optimizations.

5G NR devices, networks, and systems may be implemented to use optimized OFDM-based waveform features. These features may include scalable numerology and transmission time intervals (TTIs) ; a common, flexible framework to efficiently multiplex services and features with a dynamic, low-latency time division duplex (TDD) /frequency division duplex (FDD) design; and advanced wireless technologies, such as massive multiple input, multiple output (MIMO) , robust millimeter wave (mmWave) transmissions, advanced channel coding, and device-centric mobility. Scalability of the numerology in 5G NR, with scaling of subcarrier spacing, may efficiently address operating diverse services across diverse spectrum and diverse deployments. For example, in various outdoor and macro coverage deployments of less than 3GHz FDD/TDD implementations, subcarrier spacing may occur with 15 kHz, for example over 1, 5, 10, 20 MHz, and the like bandwidth. For other various outdoor and small cell coverage deployments of TDD greater than 3 GHz, subcarrier spacing may occur with 30 kHz over 80/100 MHz bandwidth. For other various indoor wideband implementations, using a TDD over the unlicensed portion of the 5 GHz band, the subcarrier spacing may occur with 60 kHz over a 160 MHz bandwidth. Finally, for various deployments transmitting with mmWave components at a TDD of 28 GHz, subcarrier spacing may occur with 120 kHz over a 500 MHz bandwidth.

The scalable numerology of 5G NR facilitates scalable TTI for diverse latency and quality of service (QoS) requirements. For example, shorter TTI may be used for low latency and high reliability, while longer TTI may be used for higher spectral efficiency. The efficient multiplexing of long and short TTIs to allow transmissions to start on symbol boundaries. 5G NR also contemplates a self-contained integrated subframe design with uplink/downlink scheduling information, data, and acknowledgement in the same subframe. The self-contained integrated subframe supports communications in unlicensed or contention-based shared spectrum, adaptive uplink/downlink that may be flexibly configured on a per-cell basis to dynamically switch between uplink and downlink to meet the current traffic needs.

For clarity, certain aspects of the apparatus and techniques may be described below with reference to exemplary LTE implementations or in an LTE-centric way, and LTE terminology may be used as illustrative examples in portions of the description below; however, the description is not intended to be limited to LTE applications. Indeed, the present disclosure is concerned with shared access to wireless spectrum between networks using different radio access technologies or radio air interfaces, such as those of 5G NR.

Moreover, it should be understood that, in operation, wireless communication networks adapted according to the concepts herein may operate with any combination of licensed or unlicensed spectrum depending on loading and availability. Accordingly, it will be apparent to one of skill in the art that the systems, apparatus and methods described herein may be applied to other communications systems and applications than the particular examples provided.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and/or other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, etc. ) . While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregated, distributed, or OEM devices or systems incorporating one or more described aspects. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. It is intended that innovations described herein may be practiced in a wide variety of implementations, including both large/small devices, chip-level components, multi-component systems (e.g. RF-chain, communication interface, processor) , distributed arrangements, end-user devices, etc. of varying sizes, shapes, and constitution.

FIG. 1 shows wireless network 100 for communication according to some embodiments. Wireless network 100 may, for example, comprise a 5G wireless network. As appreciated by those skilled in the art, components appearing in FIG. 1 are likely to have related counterparts in other network arrangements including, for example, cellular-style network arrangements and non-cellular-style-network arrangements (e.g., device to device or peer to peer or ad hoc network arrangements, etc. ) .

Wireless network 100 illustrated in FIG. 1 includes a number of base stations 105 and other network entities. A base station may be a station that communicates with the UEs and may also be referred to as an evolved node B (eNB) , a next generation eNB (gNB) , an access point, and the like. Each base station 105 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to this particular geographic coverage area of a base station and/or a base station subsystem serving the coverage area, depending on the context in which the term is used. In implementations of wireless network 100 herein, base stations 105 may be associated with a same operator or different operators (e.g., wireless network 100 may comprise a plurality of operator wireless networks) , and may provide wireless communications using one or more of the same frequencies (e.g., one or more frequency bands in licensed spectrum, unlicensed spectrum, or a combination thereof) as a neighboring cell. In some examples, an individual base station 105 or UE 115 may be operated by more than one network operating entity. In other examples, each base station 105 and UE 115 may be operated by a single network operating entity.

A base station may provide communication coverage for a macro cell or a small cell, such as a pico cell or a femto cell, and/or other types of cell. A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a pico cell, would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a femto cell, would also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG) , UEs for users in the home, and the like) . A base station for a macro cell may be referred to as a macro base station. A base station for a small cell may be referred to as a small cell base station, a pico base station, a femto base station or a home base station. In the example shown in FIG. 1,

base stations

105d and 105e are regular macro base stations, while base stations 105a-105c are macro base stations enabled with one of 3 dimension (3D) , full dimension (FD) , or massive MIMO. Base stations 105a-105c take advantage of their higher dimension MIMO capabilities to exploit 3D beamforming in both elevation and azimuth beamforming to increase coverage and capacity. Base station 105f is a small cell base station which may be a home node or portable access point. A base station may support one or multiple (e.g., two, three, four, and the like) cells.

Wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing, and transmissions from different base stations may not be aligned in time. In some scenarios, networks may be enabled or configured to handle dynamic switching between synchronous or asynchronous operations.

UEs 115 are dispersed throughout the wireless network 100, and each UE may be stationary or mobile. It should be appreciated that, although a mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the 3rd Generation Partnership Project (3GPP) , such apparatus may also be referred to by those skilled in the art as a mobile station (MS) , a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT) , a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, a gaming device, an augmented reality device, vehicular component device/module, or some other suitable terminology. Within the present document, a “mobile” apparatus or UE need not necessarily have a capability to move, and may be stationary. Some non-limiting examples of a mobile apparatus, such as may comprise embodiments of one or more of UEs 115, include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a laptop, a personal computer (PC) , a notebook, a netbook, a smart book, a tablet, and a personal digital assistant (PDA) . A mobile apparatus may additionally be an “Internet of things” (IoT) or “Internet of everything” (IoE) device such as an automotive or other transportation vehicle, a satellite radio, a global positioning system (GPS) device, a logistics controller, a drone, a multi-copter, a quad-copter, a smart energy or security device, a solar panel or solar array, municipal lighting, water, or other infrastructure; industrial automation and enterprise devices; consumer and wearable devices, such as eyewear, a wearable camera, a smart watch, a health or fitness tracker, a mammal implantable device, gesture tracking device, medical device, a digital audio player (e.g., MP3 player) , a camera, a game console, etc. ; and digital home or smart home devices such as a home audio, video, and multimedia device, an appliance, a sensor, a vending machine, intelligent lighting, a home security system, a smart meter, etc. In one aspect, a UE may be a device that includes a Universal Integrated Circuit Card (UICC) . In another aspect, a UE may be a device that does not include a UICC. In some aspects, UEs that do not include UICCs may also be referred to as IoE devices. UEs 115a-115d of the embodiment illustrated in FIG. 1 are examples of mobile smart phone-type devices accessing wireless network 100 A UE may also be a machine specifically configured for connected communication, including machine type communication (MTC) , enhanced MTC (eMTC) , narrowband IoT (NB-IoT) and the like. UEs 115e-115k illustrated in FIG. 1 are examples of various machines configured for communication that access wireless network 100.

A mobile apparatus, such as UEs 115, may be able to communicate with any type of the base stations, whether macro base stations, pico base stations, femto base stations, relays, and the like. In FIG. 1, a lightning bolt (e.g., communication link) indicates wireless transmissions between a UE and a serving base station, which is a base station designated to serve the UE on the downlink and/or uplink, or desired transmission between base stations, and backhaul transmissions between base stations. UEs may operate as base stations or other network nodes in some scenarios. Backhaul communication between base stations of wireless network 100 may occur using wired and/or wireless communication links.

In operation at wireless network 100, base stations 105a-105c serve

UEs

115a and 115b using 3D beamforming and coordinated spatial techniques, such as coordinated multipoint (CoMP) or multi-connectivity. Macro base station 105d performs backhaul communications with base stations 105a-105c, as well as small cell, base station 105f. Macro base station 105d also transmits multicast services which are subscribed to and received by

UEs

115c and 115d. Such multicast services may include mobile television or stream video, or may include other services for providing community information, such as weather emergencies or alerts, such as Amber alerts or gray alerts.

Wireless network 100 of embodiments supports mission critical communications with ultra-reliable and redundant links for mission critical devices, such UE 115e, which is a drone. Redundant communication links with UE 115e include from

macro base stations

105d and 105e, as well as small cell base station 105f. Other machine type devices, such as UE 115f (thermometer) , UE 115g (smart meter) , and UE 115h (wearable device) may communicate through wireless network 100 either directly with base stations, such as small cell base station 105f, and macro base station 105e, or in multi-hop configurations by communicating with another user device which relays its information to the network, such as UE 115f communicating temperature measurement information to the smart meter, UE 115g, which is then reported to the network through small cell base station 105f. Wireless network 100 may also provide additional network efficiency through dynamic, low-latency TDD/FDD communications, such as in a vehicle-to-vehicle (V2V) mesh network between UEs 115i-115k communicating with macro base station 105e.

FIG. 2 shows a block diagram of a design of a base station 105 and a UE 115, which may be any of the base stations and one of the UEs in FIG. 1. For a restricted association scenario (as mentioned above) , base station 105 may be small cell base station 105f in FIG. 1, and UE 115 may be UE 115c or 115D operating in a service area of base station 105f, which in order to access small cell base station 105f, would be included in a list of accessible UEs for small cell base station 105f. Base station 105 may also be a base station of some other type. As shown in FIG. 2, base station 105 may be equipped with antennas 234a through 234t, and UE 115 may be equipped with antennas 252a through 252r for facilitating wireless communications.

At base station 105, transmit processor 220 may receive data from data source 212 and control information from controller/processor 240. The control information may be for the physical broadcast channel (PBCH) , physical control format indicator channel (PCFICH) , physical hybrid-ARQ (automatic repeat request) indicator channel (PHICH) , physical downlink control channel (PDCCH) , enhanced physical downlink control channel (EPDCCH) , MTC physical downlink control channel (MPDCCH) , etc. The data may be for the PDSCH, etc. Transmit processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. Transmit processor 220 may also generate reference symbols, e.g., for the primary synchronization signal (PSS) and secondary synchronization signal (SSS) , and cell-specific reference signal. Transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 232 may additionally or alternatively process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 232a through 232t may be transmitted via antennas 234a through 234t, respectively.

At UE 115, the antennas 252a through 252r may receive the downlink signals from base station 105 and may provide received signals to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. MIMO detector 256 may obtain received symbols from demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. Receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 115 to data sink 260, and provide decoded control information to controller/processor 280.

On the uplink, at UE 115, transmit processor 264 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from data source 262 and control information (e.g., for the physical uplink control channel (PUCCH) ) from controller/processor 280. Transmit processor 264 may also generate reference symbols for a reference signal. The symbols from transmit processor 264 may be precoded by TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for SC-FDM, etc. ) , and transmitted to base station 105. At base station 105, the uplink signals from UE 115 may be received by antennas 234, processed by demodulators 232, detected by MIMO detector 236 if applicable, and further processed by receive processor 238 to obtain decoded data and control information sent by UE 115. Processor 238 may provide the decoded data to data sink 239 and the decoded control information to controller/processor 240.

Controllers/

processors

240 and 280 may direct the operation at base station 105 and UE 115, respectively. Controller/processor 240 and/or other processors and modules at base station 105 and/or controller/processor 280 and/or other processors and modules at UE 115 may perform or direct the execution of various processes for the techniques described herein, such as to perform or direct the execution illustrated in FIGS. 6 and 7, and/or other processes for the techniques described herein.

Memories

242 and 282 may store data and program codes for base station 105 and UE 115, respectively. Scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

Wireless communications systems operated by different network operating entities (e.g., network operators) may share spectrum. In some instances, a network operating entity may be configured to use an entirety of a designated shared spectrum for at least a period of time before another network operating entity uses the entirety of the designated shared spectrum for a different period of time. Thus, in order to allow network operating entities use of the full designated shared spectrum, and in order to mitigate interfering communications between the different network operating entities, certain resources (e.g., time) may be partitioned and allocated to the different network operating entities for certain types of communication.

For example, a network operating entity may be allocated certain time resources reserved for exclusive communication by the network operating entity using the entirety of the shared spectrum. The network operating entity may also be allocated other time resources where the entity is given priority over other network operating entities to communicate using the shared spectrum. These time resources, prioritized for use by the network operating entity, may be utilized by other network operating entities on an opportunistic basis if the prioritized network operating entity does not utilize the resources. Additional time resources may be allocated for any network operator to use on an opportunistic basis.

Access to the shared spectrum and the arbitration of time resources among different network operating entities may be centrally controlled by a separate entity, autonomously determined by a predefined arbitration scheme, or dynamically determined based on interactions between wireless nodes of the network operators.

In some cases, UE 115 and base station 105 may operate in a shared radio frequency spectrum band, which may include licensed or unlicensed (e.g., contention-based) frequency spectrum. In an unlicensed frequency portion of the shared radio frequency spectrum band, UEs 115 or base stations 105 may traditionally perform a medium-sensing procedure to contend for access to the frequency spectrum. For example, UE 115 or base station 105 may perform a listen before talk (LBT) procedure such as a clear channel assessment (CCA) prior to communicating in order to determine whether the shared channel is available. A CCA may include an energy detection procedure to determine whether there are any other active transmissions. For example, a device may infer that a change in a received signal strength indicator (RSSI) of a power meter indicates that a channel is occupied. Specifically, signal power that is concentrated in a certain bandwidth and exceeds a predetermined noise floor may indicate another wireless transmitter. A CCA also may include detection of specific sequences that indicate use of the channel. For example, another device may transmit a specific preamble prior to transmitting a data sequence. In some cases, an LBT procedure may include a wireless node adjusting its own backoff window based on the amount of energy detected on a channel and/or the acknowledge/negative-acknowledge (ACK/NACK) feedback for its own transmitted packets as a proxy for collisions.

FIGS. 3A-3C illustrate examples of handover operations for a mobile device. FIG. 3A is an example diagram illustrating a mobile device (e.g., mobile UE) moving through a number of cells and respective cell coverage areas. FIG. 3B is an example diagram illustrating cell attachment times for the mobile device of FIG. 3A as it moves through cell coverage areas. FIG. 3C is an example of a ladder diagram illustrating handover operations for the mobile device of FIG. 3A according to some embodiments of the present disclosure.

Referring to FIG. 3A, the diagram illustrates a UE, such as a car or a user device on board a vehicle, moving through a plurality of cell coverage areas. The UE may be a fast moving UE and/or may be moving along cell boundaries. As the UE moves from cell to cell, the network may perform handover operations to provide the UE with the best or most suitable connection and to prevent connection losses, such as dropped calls. Conventionally, handover operations are based on reference signal received power (RSRP) and/or location. To illustrate, the UE may switch between cells based on which cell has a highest RSRP. The network may determine to initiate the switch based on RSRP information reported by the UE, as described further with reference to FIG. 3C.

In FIG. 3A, the diagram illustrates multiple small cells (e.g., micro cells) and one macro cell. For example, multiple small cells may be used in conjunction with a macro cell to provide better coverage and increase capacity and throughput. As illustrated in FIG. 3A, the respective coverage areas of the small cells overlap a portion of the macro cell coverage area and are distributed on an exterior of the macro cell coverage area. The small cells may be connected to and/or part of the macro cell. For example, the small cells may be part of the same base station or network entity. Alternatively, the small cells may be independent cells (e.g., individual base stations) and are part of the same network as the macro cell.

In some implementations, the small cells may provide relatively higher frequency service /shorter range service, such as mmwave service, and the macro cell may provide relatively lower frequency service, such as sub 6GHz service. In other implementations, both cells provide similar frequency service, such as mmwave service and/or sub 6GHz service.

During operation, a UE connects to the macro cell. For example, the UE initializes a communication link with the macro cell. The UE may be in a radio resource configuration (RRC) connected state with the macro cell. The network may begin to track cell attachment /cell history information. To illustrate, the network may start a timer to track cell attachment /stay duration and associate the cell identifier (e.g., PCI) of the macro cell to the timer or duration. The UE may begin to move, for example the UE may be a vehicle or may be riding on board a vehicle. In some implementations, the UE is a fast-moving UE, i.e., moving faster than a human walking (roughly greater than 5 mph) .

As illustrated in FIG. 3A, the UE leaves the macro cell service/coverage area and then travels across (i.e., horizontally in FIG. 3A) a plurality of coverage areas of a plurality of small cells. In the example of FIG. 3A, the UE spends different amounts of time in the different service/coverage areas. The service/coverage areas of FIG. 3A illustrate areas where the cell usually provides good signal strength. However, the cell can at times serve devices outside of the coverage area. An example cell attachment diagram for a portion of the UE movement of FIG. 3A is illustrated in FIG. 3B.

Referring to FIG. 3B, the diagram illustrates cell attachment times for the UE as the UE moves through three exemplary small cells as shown in FIG. 3A. As illustrated in FIG. 3B, the cell attachment times are illustrated along a horizontal (e.g., x axis) , with the most recent cell being on the left hand side and the first or oldest cell further towards the right. The diagram of FIG. 3B illustrates longer stay times by with wider or longer entries. In the example of FIG. 3B, the network stores history information for up to 16 of the previous cells, and the last five entries of the history information are blank. The cell attachment time (aka cell stay times) may be recorded and tracked by the UE. In FIG. 3B, the five most recent cell stay times are 2 seconds, 3 seconds, 4 seconds, 4 seconds, and 4 seconds.

Additionally, the network may transmit cell attachment time information from a serving cell /transferring cell to transferee cell. For example, the first small cell may send a UE history information element to a second small cell in. In some implementations, the UE history information (e.g., UE history information element) is included in a handover request message. The UE history information element indicates a cell ID for a past number of cells to which the UE was connected to and the corresponding attachment time. The network may clear the history information periodically or upon a trigger condition, such as upon a UE leaving an RRC connected state or upon the UE entering an RRC unconnected state or idle state.

Referring to FIG. 3C, the ladder diagram illustrates an example of a portion of a ladder diagram for the UE of FIG. 3A. To illustrate, the UE connects to a first small cell (e.g., smallcell_1) . In some implementations, the UE may connect to the small cell by a handover from another small cell or a macro cell. In other implementations, the UE connects to the small cell directly /independent of a handover. The UE then sends a measurement report message. For example, the UE may send a measurement report, such as a channel state feedback (CSF) report to the first small cell. The measurement report includes channel parameters, such as RSRP for the UE with respect to the first small cell. The measurement report may also include a second RSRP for the UE for another cell, such as for /with respect to a second small cell (e.g., smallcell_2) . The first small cell receives the measurement report message and extracts the RSRP or RSRPs. Based on the RSRP or RSRPs, the first small cell may decide to perform a handover operation, such as illustrated by steps 3-6. For example, the first small cell may compare the RSRPs to each other and/or to one or more thresholds.

The UE and network, first and second small cells) , perform conventional handover operations, such as illustrated by steps 3-6. For example, the first small cell transmits a handover request message to the second small cell and receives an acknowledgement message (e.g., a handover request acknowledgement message) . Responsive to receiving the acknowledgement message, the first small cell transmits a handover initiation message to the UE, such as a RRC connection reconfiguration message. Upon receiving the handover initiation message (e.g., RRC connection reconfiguration message) , the UE reconfigures its RRC connection to the second small cell and sends a handover RRC connection reconfiguration complete message to the second small cell.

Once connected to the second small cell, the UE may send a second measurement report message, such as a CSF report, to the second small cell. The second measurement report message includes channel parameters, such as RSRP for the UE from the second small cell. The measurement report may also include a second RSRP for the UE for another cell, such as a third small cell (e.g., smallcell_3) . The second small cell receives the measurement report message and extracts the RSRP or RSRPs. Based on the RSRP or RSRPs, the second small cell may decide to perform a handover operation, such as illustrated by steps 8-11.

However, the handover operation may fail, such as illustrated by step 12. With any handover operation, the handover process can fail at either the UE side or the network side. Such a problem may be exacerbated when using small cells and/or fast moving UEs. To illustrate, the smaller coverage areas, possible urban/dense settings, and movement speed may cause more frequent handovers when attached to a small cell than when attached to a macro cell and such handovers may have a higher failure rate due to blockage from density and/or the increased movement speed.

After a failure, the UE may determine to reconnect with a cell, such as the previous cell to which is was successfully connected. As illustrated in the example of FIG. 3C, the UE attempts to reconnect with the second small cell by sending a RRC connection reestablishment message. In the example of FIG. 3A, the UE may be getting even further from the second small cell by the time it reattaches /reestablishes connection. Additionally, the network may determine to attempt another handover from the second small cell to the third small cell. By such time, the UE may even be getting close to or entering a coverage area of a fourth small cell, and being prompted to switch again. Such frequency switching interrupts the flow of data messages and may cause some data to be missed or delayed.

Thus, the handover switching based on RSRP alone may lead to prioritizing throughput and frequent switching at the expense of reliability and connection stability. Additionally, such frequent switching increases network overhead (e.g., increased signaling) and reduces UE battery power.

However, cell attachment history information can be utilized by networks to reduce frequent cell switching under certain conditions. For example, when a UE is moving from small cell to small cell quickly, the UE can be handed over to a macro cell to reduce or prevent additional handover operations. The history information may be used in the alternative to conventional handover operation determinations. Alternatively, history information may be used in conjunction with conventional operations and/or metrics. To illustrate, history information and RSRP may be used to determine when to perform handover operations. By using history information, a network may determine to switch to a macro cell instead of another small cell. Thus, frequency small cell switching may be reduced. Accordingly, network overhead is reduced and radio link failures are reduced.

FIG. 4 illustrates an example of a wireless communications system 400 that supports cell history based handover in accordance with aspects of the present disclosure. In some examples, wireless communications system 400 may implement aspects of wireless communication system 100. For example, wireless communications system 400 may include UE 115, network entity 105, second network entity 405a, and third network entity 405b. Cell history based handover operations may increase reliability and reduce latency by reducing cell switching. This results in increased connection stability. Thus, network and device performance can be increased.

Network entity 105 and UE 115 UE 115 may be configured to communicate via frequency bands, such as FR1 having a frequency of 410 to 7125 MHz, FR2 having a frequency of 24250 to 52600 MHz for mm-Wave, and/or one or more other frequency bands. It is noted that sub-carrier spacing (SCS) may be equal to 15, 30, 60, or 120 kHz for some data channels. Network entity 105 and UE 115 may be configured to communicate via one or more component carriers (CCs) , such as representative first CC 481, second CC 482, third CC 483, and fourth CC 484. Although four CCs are shown, this is for illustration only, more or fewer than four CCs may be used. One or more CCs may be used to communicate control channel transmissions, data channel transmissions, and/or sidelink channel transmissions.

Such transmissions may include a Physical Downlink Control Channel (PDCCH) , a Physical Downlink Shared Channel (PDSCH) , a Physical Uplink Control Channel (PUCCH) , a Physical Uplink Shared Channel (PUSCH) , a Physical Sidelink Control Channel (PSCCH) , a Physical Sidelink Shared Channel (PSSCH) , or a Physical Sidelink Feedback Channel (PSFCH) . Such transmissions may be scheduled by aperiodic grants and/or periodic grants.

Each periodic grant may have a corresponding configuration, such as configuration parameters/settings. The periodic grant configuration may include configured grant (CG) configurations and settings. Additionally, or alternatively, one or more periodic grants (e.g., CGs thereof) may have or be assigned to a CC ID, such as intended CC ID.

Each CC may have a corresponding configuration, such as configuration parameters/settings. The configuration may include bandwidth, bandwidth part, HARQ process, TCI state, RS, control channel resources, data channel resources, or a combination thereof. Additionally, or alternatively, one or more CCs may have or be assigned to a Cell ID, a Bandwidth Part (BWP) ID, or both. The Cell ID may include a unique cell ID for the CC, a virtual Cell ID, or a particular Cell ID of a particular CC of the plurality of CCs. Additionally, or alternatively, one or more CCs may have or be assigned to a HARQ ID. Each CC may also have corresponding management functionalities, such as, beam management, BWP switching functionality, or both. In some implementations, two or more CCs are quasi co-located, such that the CCs have the same beam and/or same symbol.

In some implementations, control information may be communicated via network entity 105 and UE 115. For example, the control information may be communicated suing MAC-CE transmissions, RRC transmissions, DCI, transmissions, another transmission, or a combination thereof.

UE 115 can include a variety of components (e.g., structural, hardware components) used for carrying out one or more functions described herein. For example, these components can include processor 402, memory 404, transmitter 410, receiver 412, encoder, 413, decoder 414, measurement report manager 415, history information manager 416 and antennas 252a-r. Processor 402 may be configured to execute instructions stored at memory 404 to perform the operations described herein. In some implementations, processor 402 includes or corresponds to controller/processor 280, and memory 404 includes or corresponds to memory 282. Memory 404 may also be configured to store history information data 406, measurement report data 408, thresholds data 442, settings data 444, or a combination thereof, as further described herein.

The history information data 406 includes or corresponds to data associated with or corresponding to cell attachment /connection history information. For example, the history information 406 may include cell history information for a UE for a past number of cells or for a past period of time, such as information for a past 16 cells. In some implementations, the history information data 406 includes or corresponds to a UE history information element. The UE history information data 408 (e.g., UE history information element) may include a cell identifier (cell ID, e.g., physical cell identifier (PCI) ) and an attachment time for each cell. The UE history information may be arranged in sequence /order to indicate a most recent or current cell first and a first or earliest cell last. Thus, the history information can track the order of cell attachment.

The measurement report data 408 includes or corresponds to data associated with or corresponding to a UE measurement report. For example, the measurement report data 408 may include beam information, channel information, or both. To illustrate, the measurement report data 408 may include physical layer parameters and/or quality metrics, such as RSRP. The measurement report data 408 may include data for the current cell and for one or more surrounding cells in some implementations. For example, the measurement report data 508 may include all determined RSRPs or a subset of RSRPs, such as RSRPs which satisfy a threshold condition. The measurement report data 508 further includes history information, such as history information data 408 (e.g., UE history information element) . In some implementations, the measurement report data 408 includes or corresponds to a CSF or CSI report.

The thresholds data 442 include includes or corresponds to data associated with history based cell handover and corresponding determinations. The thresholds data 442 may include thresholds for sending the measurement report message, for including history information, for determining to perform a handover, to refrain from performing a handover, etc. The settings data 444 includes or corresponds to data associated with history based cell handover. The settings data 444 may include one or more type of history based cell handover modes and/or thresholds or conditions for selecting and/or implementing the history based cell handover modes.

Transmitter 410 is configured to transmit data to one or more other devices, and receiver 412 is configured to receive data from one or more other devices. For example, transmitter 410 may transmit data, and receiver 412 may receive data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, UE 115 may be configured to transmit and/or receive data via a direct device-to-device connection, a local area network (LAN) , a wide area network (WAN) , a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter 410 and receiver 412 may be replaced with a transceiver. Additionally, or alternatively, transmitter 410, receiver, 412, or both may include or correspond to one or more components of UE 115 described with reference to FIG. 2.

Encoder 413 and decoder 414 may be configured to encode and decode data for transmission. Measurement report manager 415 may be configured to determine and perform measurement report generation and transmission operations. For example, the measurement report manager 415 is configured to determine when to generate a measurement report and what to include in the measurement report. To illustrate, measurement report manager 415 may determine to send a CSF report responsive to downlink transmissions and may determine to include RSRP information in the CSF report. In other implementations, the measurement report manager 415 may determine to generate the CSF report based on the history information data 406, such as include or indicate a portion of history information data 406. In a particular implementation, the CSF report or other message includes an indicator of a fast moving UE /frequent handover UE which was generated based on the history information data 406.

History information manager 416 may be configured to store and update cell history information. For example, history information manager 416 is configured to determine and/or select a history information reporting type. To illustrate, history information manager 416 is configured to determine to use a history information element to report the history information data 406.

Network entity 105 includes processor 430, memory 432, transmitter 434, receiver 436, encoder 437, decoder 438, history based handover manager 439, history information manager 440, and antennas 234a-t. Processor 430 may be configured to execute instructions stores at memory 432 to perform the operations described herein. In some implementations, processor 430 includes or corresponds to controller/processor 240, and memory 432 includes or corresponds to memory 242. Memory 432 may be configured to store history information data 406, measurement report data 408, thresholds data 442, settings data 444, or a combination thereof, similar to the UE 115 and as further described herein.

Transmitter 434 is configured to transmit data to one or more other devices, and receiver 436 is configured to receive data from one or more other devices. For example, transmitter 434 may transmit data, and receiver 436 may receive data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, network entity 105 may be configured to transmit and/or receive data via a direct device-to-device connection, a local area network (LAN) , a wide area network (WAN) , a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter 434 and receiver 436 may be replaced with a transceiver. Additionally, or alternatively, transmitter 434, receiver, 436, or both may include or correspond to one or more components of network entity 105 described with reference to FIG. 2.

Encoder 437, and decoder 438 may include the same functionality as described with reference to encoder 413 and decoder 414, respectively. History based handover manager 439 may be configured to determine and perform history based UE handover operations. For example, the history based handover manager 439 is configured to determine whether to perform a handover operation for the UE based on received history information. To illustrate, the history based handover manager 439 may to perform a handover based on a history information element or indicator of a handover request message. In a particular example, the history based handover manager 439 may refrain from switching to another small cell or may switch to a macro cell based on the history information indicating that the UE is a fast moving UE and/or is experiencing frequent switching. History information manager 440 may include similar functionality to history information manager 416. For example, history information manager 440 may generate, transmit and update cell history information for UEs. In some implementations, only network entities (e.g., 105, 405a, 405b) generate, transmit, and update cell history information and UEs do not include a history information manager 416.

During operation of wireless communications system 400, network entity 105 may determine that UE 115 has history information reporting capability. For example, UE 115 may transmit a message 448 that includes a history information reporting indicator 490. Indicator 490 may indicate history information reporting capability or a particular type or mode of history information reporting. In some implementations, network entity 105 sends control information to indicate to UE 115 that history information reporting and/or a particular type of history information reporting is to be used. For example, in some implementations, message 448 (or another message, such as configuration transmission 450) is transmitted by the network entity 105. The configuration transmission 450 may include or indicate to use history information reporting or to adjust or implement a setting of a particular type of history information reporting.

Alternatively, the network entity 105 may not signal to the UE 115 to report history information. For example, the network entity 105 may track (e.g., generate and update) cell history information for the UE. As another example, the UE 115 may automatically report history information and the network entity 105 may implement history based cell handover without signaling to the UE 115.

During operation, devices of wireless communications system 400, perform cell history based handover. For example, a UE 115 may transmit a measurement report message 462 to a network entity, such as network entity 105 (e.g., first network entity) . The measurement report message 462 may be sent responsive to a transmission received from the network entity 105. Alternatively, the measurement report message 462 may be sent periodically by the UE 115 or in response to a UE determination.

After receiving the measurement report message 462, the network entity determines whether to perform a handover operation based on at least cell history information for the UE 115. For example, the network entity 105 determines whether to perform a handover operation to either a second network entity 405a or a third network entity 405b based on received or generated cell history information for the UE 115. For example, the network entity 105 receives cell history information for the UE 115 in a handover request from a previous cell (e.g., previous network entity) to which the UE 115 was attached. As another example, the network entity 105 generated the cell history information for the UE 115 responsive to attachment of the UE 115.

After determining to perform a handover operation for the UE 115 to the second network entity 405a, the network entity 105 and the second network entity 405a may exchange handover messages. For example, the

network entities

105, 405a may transmit handover request and acknowledgement messages as illustrated in FIG. 3C. This handover request may include the cell history information for the UE 115, and the second network entity 405a may be able to use such information when determining when to perform handover operations.

Responsive to the network entity 105 signaling the handover to the second network entity 405a, the second network entity 405a transmits a RRC reconfiguration message 464 to the UE 115. The UE 115 receives the RRC reconfiguration message 464 and reconfigures its settings to connect /attach to the second network entity 405a. The UE 115 transmits a RRC reconfiguration acknowledgement message 466 to the second network entity 405a responsive to receiving the RRC reconfiguration message 464. For example, the UE 115 may transmit a RRC reconfiguration acknowledgement message 466 to the second network entity 405a in response updating communication link settings based on the RRC reconfiguration message 464.

The UE 115 and second network entity 405a may perform data channel transmissions 468 after link establishment. For example, the network entity or entities transmit downlink data (e.g., DL symbols) and the UE 115 transmits uplink data (UL symbols) . Additionally, the UE 115 may send a second measurement report message (e.g., 462) to the second network entity 405a. Thus, the UE 115 and network entities may be able to perform history based cell handover determinations.

Accordingly, FIG. 4 describes enhanced history based cell handover determinations for small cells. Using history based cell handover determinations may enable improvement when operating in a network with small and macros cells and/or when traveling fast. Performing history based cell handover determinations enables reduced latency and increased reliability and thus, enhanced UE and network performance.

FIG. 5 illustrates an example ladder diagram 500 for history based cell handover determination operations. Referring to FIG. 5, FIG. 5 is a ladder diagram 500 of an example of cell history based cell handover for small cells. FIG. 5 depicts a UE 115 and three network entities, a first small cell 105a, a second small cell 105b, and a macro cell 105c.

FIG. 5 illustrates similar attachment and connection operations to FIG. 3C. For example, at 510, UE 115 connects to a first small cell and. at 515, reports measurement information. In the example of FIG. 5, the handover determination is based on cell history information. The first small cell may evaluate a history information based handover determination (e.g., a fast moving UE algorithm) responsive to receiving the measurement report message.

In the example of FIG. 5, the first small cell 105a determines to switch cells, i.e., perform a handover operation based at least in part on the cell history information. As an illustrative example, the first small cell 105a may determine that one or more of a last cell stay time, an average cell stay time, or a last N number of stay times does not meet a corresponding condition for a fast moving UE or frequent switching UE. Additionally, or alternatively, the UE 115 may determine that an RSRP of the macro cell 105c does not meet a corresponding RSRP threshold (e.g., -100 dBm) .

The first small cell 105a determines to switch the UE 115 to a second small cell 105b based on the fast moving algorithm and optionally, conventional operations, such as based on an RSRP of the second small cell 105b exceeding a threshold and/or an RSRP of the first small cell 105a. To illustrate, an RSRP of the second small cell 105b may be greater than an RSRP of the second small cell 105b and/or a difference between the RSRPs may be greater than a threshold.

Similar to FIG. 3C, the first small cell 105a performs a handover operation to switch the UE 115 to a second small cell 105b, such as illustrated by operations 3-6. For example, at 520, the first small cell 105a transmits a handover request message, which include cell history information for the UE 115, to the second small cell 105b and receives an acknowledgement message (e.g., a handover request acknowledgement message) at 525. Responsive to receiving the acknowledgement message, the first small cell 105a transmits a handover initiation message to the UE 115, such as a RRC connection reconfiguration message at 530. Upon receiving the handover initiation message (e.g., RRC connection reconfiguration message) , the UE 115 reconfigures its RRC connection to the second small cell 105b and sends a handover RRC connection reconfiguration complete message to the second small cell 105b at 535.

While the UE 115 is connected to the second small cell 105b, the UE 115 transmits a second measurement report message to the second small cell 105b at 540. At 545, the second small cell 105b may evaluate the fast moving UE algorithm responsive to receiving the second measurement report message. In the example of FIG. 5, the second small cell 105b determines to switch cell, i.e., perform a handover operation based at least in part on the cell history information. The cell history information which the second small cell 105b uses is “updated” cell history information as compared to the cell history information used by the first small cell 105a and now includes the history information for the first small cell 105a.

As an illustrative example, the second small cell 105b may determine that one or more of a last cell stay time, an average cell stay time, or a last N number of stay times meets a corresponding condition for a fast moving UE or a frequent switching UE. To illustrate, based on the stay time for a last N (e.g., 2, 3, 4, 5, 6, 8, etc. ) number of cells each satisfying a cell stay time threshold (e.g., 4 seconds, 6 seconds, 10 seconds, 20 seconds, etc. ) , the second small cell 105b determines to switch to a macro cell 105c.

In some implementations, the second small cell 105b may utilize RSRP as well. For example, the second small cell 105b may use an RSRP determination prior to or after the cell stay time determination. To illustrate, the second small cell 105b may compare an RSRP of the macro cell 105c to a threshold to determine if the macro cell 105c is able to serve the UE 115. Responsive to satisfying the RSRP condition, the second small cell 105b may perform handover operations to switch the UE 115 to the macro cell 105c to reduce or prevent frequent switching, such as frequency small cell to small cell switching.

After determining to perform a handover based on the cell history information, the second small cell 105b may perform handover operations which are similar to the handover operations of 3-6. To illustrate, at 550, the second small cell 105b transmits a handover request message, including cell history information, to the macro cell 105c and receives an acknowledgement message (e.g., a handover request acknowledgement message) at 555. Responsive to receiving the acknowledgement message, the second small cell 105b transmits a handover initiation message to the UE 115, such as a RRC connection reconfiguration message at 560. Upon receiving the handover initiation message (e.g., RRC connection reconfiguration message) , the UE 115 reconfigures its RRC connection to the macro cell 105c and sends a handover RRC connection reconfiguration complete message to the macro cell 105c at 565.

Optionally, the network and/or UE 115 may implement hysteresis after switching to the macro cell 105c to reduce or prevent switching back to a small cell for a period of time and/or until certain conditions are satisfied. For example, the hysteresis may include time /duration conditions, such as no switching to a small cell until 20 seconds have elapsed, and/or quality metric conditions, such as an RSRP of a small cell above a first threshold and/or a RSRP of the current /macro cell 105c below a second threshold.

In other implementations, device speed may be utilized in addition to, or in the alternative of history information. Device speed may also be used as a hysteresis condition. To illustrate, small cell handover operations may not be allowed until the UE’s speed is less than a threshold. Device speed may be determined by a sensor of the UE 115, e.g., accelerometer or based on changes in distance with one or more cells, such as by a TA value.

Thus, in the example in FIG. 5, the UE 115 and network entities employ cell history information based handover determination. That is, the network determines whether to perform a handover and/or the intended cell for the handover based on cell history information. Although the example of FIG. 5 illustrates the network generating and transmitting the cell history information, in other implementations, the UE 115 can generate and/or transmit the cell history information.

Additionally, or alternatively, one or more operations of FIGS. 3C, 4, and/or 5 may be added, removed, substituted in other implementations. For example, the operations of FIG. 3C may occur before the operations of FIG. 5 in some implementations. That is, multiple handover operations between small cells may occur before switching to a macro cell. As another example, the handover operations between the first and second small cells of FIG. 5 may be omitted, i.e., a transition straight to a macro cell may occur based on threshold values. As yet another example, FIG. 5 may represent a simplified flow of handover operations and other messages may be sent during such time.

FIG. 6 is a flow diagram illustrating example blocks executed by a UE configured according to an aspect of the present disclosure. The example blocks will also be described with respect to UE 115 as illustrated in FIG. 8. FIG. 8 is a block diagram illustrating UE 115 configured according to one aspect of the present disclosure. UE 115 includes the structure, hardware, and components as illustrated for UE 115 of FIG. 2. For example, UE 115 includes controller/processor 280, which operates to execute logic or computer instructions stored in memory 282, as well as controlling the components of UE 115 that provide the features and functionality of UE 115. UE 115, under control of controller/processor 280, transmits and receives signals via wireless radios 800a-r and antennas 252a-r. Wireless radios 800a-r includes various components and hardware, as illustrated in FIG. 2 for UE 115, including modulator/demodulators 254a-r, MIMO detector 256, receive processor 258, transmit processor 264, and TX MIMO processor 266. As illustrated in the example of FIG., memory 282 stores measurement report logic 802, handover logic 803, history information logic 804, hysteresis logic 805, thresholds data 806, and settings data 807.

At block 600, a wireless communication device, such as a UE, transmits a measurement report message to a first network entity. For example, the UE 115 transmits a CSF report, including RSRP values for a number of cells including the serving cell, as described with reference to FIGS. 4 and 5.

At block 601, the UE 115 receives a RRC connection reconfiguration message from the first network entity, the RRC connection reconfiguration message generated based on cell history information. For example, the UE 115 receives a RRC connection reconfiguration message from the small cell to which the UE is connected to, as described with reference to FIGS. 4 and 5. The RRC connection reconfiguration message was generated responsive to and based on determination by the small cell to perform a handover request which utilized cell history information

At block 602, the UE 115 transmits a RRC connection reconfiguration complete message to a second network entity. For example, the UE 115 reconfigures one or more settings or parameters to attach to a second cell, such as a macro cell, and transmits a RRC connection reconfiguration complete message to the second cell, as described with reference to FIGS. 4 and 5.

The UE 115 may execute additional blocks (or the UE 115 may be configured further perform additional operations) in other implementations. For example, the UE 115 may perform one or more operations described above. As another example, the UE 115 may perform and/or operate according to one or more aspects as described below.

In a first aspect, the measurement report includes RSRP information.

In a second aspect, alone or in combination with one or more of the above aspects, the cell history information corresponds to a UE history information element transmitted in a handover request message.

In a third aspect, alone or in combination with one or more of the above aspects, the cell history information indicates a cell ID and a stay time for each cell of a past number of cells to which the UE has been attached.

In a fourth aspect, alone or in combination with one or more of the above aspects, the UE 115 is in an RRC connected state.

In a fifth aspect, alone or in combination with one or more of the above aspects, the first network entity is a small cell, and the second network entity is a macro cell.

In a sixth aspect, alone or in combination with one or more of the above aspects, the

UE 115 determines a RSRP for the first network entity and determines to send the measurement report message based on the RSRP being less than a threshold.

In a seventh aspect, alone or in combination with one or more of the above aspects, the second network entity has a lower RSRP than the first network entity.

In an eighth aspect, alone or in combination with one or more of the above aspects, the second network entity has a RSRP greater than a RSRP threshold.

In a ninth aspect, alone or in combination with one or more of the above aspects, prior to transmitting the measurement report message, the UE transfers from a previous small cell to the first network entity based on a previous cell stay time being greater than a cell stay time threshold.

In a tenth aspect, alone or in combination with one or more of the above aspects, after to transmitting the RRC connection reconfiguration complete message, the UE stays attached to the second network entity while a RSRP of the second network entity is above a threshold.

In another aspect a UE may be configured to store history information, track cell switching, track UE speed, or a combination thereof. In such aspects, the UE may determine to perform a handover based on history information, cell switching frequency and/or speed and may transmit an handover request message or indicator to a network to initiate a handover from a small cell to a macro cell. For example, the UE 115 generates cell history information based on performing handover operations; generates measurement report information; determines to perform a handover operation based on the cell history information and the measurement report information; transmits a handover request message to the network; and receives a RRC connection reconfiguration message from the network.

Accordingly, a UE and a base station may perform cell history handover determination operations. By performing cell history handover determination operations, connection stability and reliability may be increased.

FIG. 7 is a flow diagram illustrating example blocks executed by wireless communication device configured according to another aspect of the present disclosure. The example blocks will also be described with respect to base station 105 (e.g., gNB) as illustrated in FIG. 9. FIG. 9 is a block diagram illustrating base station 105 configured according to one aspect of the present disclosure. Base station 105 includes the structure, hardware, and components as illustrated for base station 105 of FIG. 2. For example, base station 105 includes controller/processor 240, which operates to execute logic or computer instructions stored in memory 242, as well as controlling the components of base station 105 that provide the features and functionality of base station 105. Base station 105, under control of controller/processor 240, transmits and receives signals via wireless radios 901a-t and antennas 234a-t. Wireless radios 901a-t includes various components and hardware, as illustrated in FIG. 2 for base station 105, including modulator/demodulators 232a-t, MIMO detector 236, receive processor 238, transmit processor 220, and TX MIMO processor 230. As illustrated in the example of FIG. 9, memory 242 stores measurement report logic 902, handover logic 903, history information logic 904, hysteresis logic 905, thresholds data 906, and settings data 907. One of more of 902-907 may include or correspond to one of 802-807.

At block 700, a wireless communication device, such as a base station, receives a handover request message from a second network entity, the handover request message including cell history information for a from a user equipment (UE) . For example, the base station 105 is a small cell and receives a handover request message from another cell (e.g., a small cell) that includes a UE history information element, as described with reference to FIGS. 4 and 5.

At block 701, the base station 105 receives a measurement report message from the UE. For example, the base station 105 receives a CSF report that indicates one or more RSRP values for the UE with respect to the base station 105 and other surrounding cells, as described with reference to FIGS. 4 and 5.

At block 702, the base station 105 determines to perform a handover operation for the UE based on the cell history information and the measurement report message. For example, the base station 105 evaluates the cell stay time or times of the UE and an RSRP for a macro cell to determine to switch the UE to the macro cell, as described with reference to FIGS. 4 and 5. As an illustrative example, the base station 105 uses cell stay times for a past number of cells and compares the cell stay times to a threshold. After satisfying such a threshold, the base station 105 may confirm that a RSRP of the UE for the macro cell is greater than a threshold before transitioning the UE to the macro cell

At block 703, the base station 105 transmits a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information. For example, the base station 105 transmits a second handover request message to a macro cell that includes an updated UE history information element (i.e., updated as compared to the UE history information element that the base station 105 received as it now includes a cell stay time entry for the base station 105) , as described with reference to FIGS. 4 and 5.

The base station 105 may execute additional blocks (or the base station 105 may be configured further perform additional operations) in other implementations. For example, the base station 105 may perform one or more operations described above. As another example, the UE 115 may perform and/or operate according to one or more aspects as described below.

In a first aspect, the base station 105 (e.g., first network entity) receives a handover request acknowledgment message from the second network entity, and the base station 105 transmits a RRC connection reconfiguration message to the UE responsive to the handover request acknowledgment message.

In a second aspect, alone or in combination with one or more of the above aspects, the measurement report includes RSRP information.

In a third aspect, alone or in combination with one or more of the above aspects, the cell history information corresponds to a UE history information element.

In a fourth aspect, alone or in combination with one or more of the above aspects, the cell history information indicates a cell ID and a stay time for each cell of a past number of cells to which the UE has been attached.

In a fifth aspect, alone or in combination with one or more of the above aspects, the network entity is a first small cell, wherein the second network entity is a second small cell.

In a sixth aspect, alone or in combination with one or more of the above aspects, the third network entity is a macro cell.

In a seventh aspect, alone or in combination with one or more of the above aspects, the determination is based on a cell stay time for a number of past cells and based on an RSRP for the UE for the second network entity.

In an eighth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information includes: determining a number of cells to evaluate for stay time based on a cell number threshold; determining a stay time for each cell of the past number of cells based on the cell history information; comparing the stay time for each cell to a stay time threshold; and, responsive to determining that the stay time for each cell of the past number of cells is lower than the stay time threshold, determining to perform the handover operation.

In a ninth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information further includes: determining a first RSRP for the network entity for the UE; determining a second RSRP for the third network entity for the UE; comparing the first RSRP to the second RSRP; and responsive to determining that the first RSRP is higher than second RSRP, determining to perform the handover operation.

In a tenth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information includes: determining a RSRP for the third network entity for the UE; and comparing the RSRP to a macro cell RSRP threshold, wherein determining to perform the handover operation is further based on the RSRP exceeding the macro cell RSRP threshold.

In an eleventh aspect, alone or in combination with one or more of the above aspects, the number of cells correspond to a number of number of small cells.

In a twelfth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information includes: determining a number of cells to test for stay time based on a cell number threshold; determining an average stay time for the past number of cells; comparing the average stay time to a stay time threshold; and responsive to determining that the average stay time is lower than the stay time threshold, determining to perform the handover operation.

In a thirteenth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information includes: determining a last cell stay time for a last cell; comparing the last stay time for each to a last stay time threshold; and responsive to determining that the last cell stay time to is less than the last stay time threshold, determining to perform the handover operation.

In a fourteenth aspect, alone or in combination with one or more of the above aspects, determining to perform the handover operation for the UE based on the cell history information includes: determining a number of cells to test for stay time based on a cell number threshold; determining a stay time for each cell of the past number of cells; comparing the stay time for each to a stay time threshold; responsive to determining that the stay time for each cell of the past number of cells is greater than the stay time threshold, comparing a last cell stay time to a second stay time threshold; and, responsive to determining that stay cell stay time to is less than the second stay time threshold, determining to perform the handover operation.

In a fourteenth aspect, alone or in combination with one or more of the above aspects, prior to receiving the measurement report message: the base station 105 receives, from a previous small cell, a previous handover request message, transmits a previous handover request acknowledgment message to the previous small cell, and receives a previous RRC connection reconfiguration complete message from the UE.

In a fifteenth aspect, alone or in combination with one or more of the above aspects, the number of cells threshold is 4 cells.

In a sixteenth aspect, alone or in combination with one or more of the above aspects, the stay time on cell threshold is 10 seconds.

In a seventeenth aspect, alone or in combination with one or more of the above aspects, the macro cell RSRP threshold is -100 dBm,

In another aspect a separate base station (e.g., macro cell) may perform one or more of the following actions. For example, the base station 105 receives a handover request message from a second network entity for a particular user equipment (UE) , the handover request message generated based on cell history information for the UE; transmits a handover request acknowledgment message to the second network entity; and receives a RRC connection reconfiguration complete message from the UE.

In some such aspects, the handover request message includes the cell history information, such as updated cell history information. Additionally, or alternatively, the base station 105 (e.g., first network entity) is a macro cell, and the second network entity is a small cell.

In some such aspects, after to transmitting the RRC connection reconfiguration complete message: the base station 105 receives a second measurement report message, and the base station 105 determines not to perform a handover for the UE based on a RSRP value for the UE with respect to the network entity and indicated by the second measurement report message is above a threshold.

In another aspect a network as a whole (e.g., small cells, macro cells, RAN, core, etc. ) may perform one or more of the following actions. For example.

For example, a network generates cell history information for a user equipment (UE) based on performing handover operations; receives a measurement report message from the UE; determines to perform a handover operation for the UE based on the cell history information and the measurement report message; transmits a RRC connection reconfiguration message to the UE responsive to the handover request acknowledgment message; and receives a RRC connection reconfiguration complete message from the UE.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The functional blocks and modules described herein (e.g., the functional blocks and modules in FIG. 2) may comprise processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof. In addition, features discussed herein relating to history based handover determinations may be implemented via specialized processor circuitry, via executable instructions, and/or combinations thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps (e.g., the logical blocks in FIGS. 6 and 7) described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Skilled artisans will also readily recognize that the order or combination of components, methods, or interactions that are described herein are merely examples and that the components, methods, or interactions of the various aspects of the present disclosure may be combined or performed in ways other than those illustrated and described herein.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. Computer-readable storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, a connection may be properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL) , then the coaxial cable, fiber optic cable, twisted pair, or DSL, are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , hard disk, solid state disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

As used herein, including in the claims, the term “and/or, ” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of” indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) or any of these in any combination thereof.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

WHAT IS CLAIMED IS:

Claims

A method of wireless communication comprising:

transmitting, by a user equipment (UE) , a measurement report message to a first network entity;

receiving, by the UE, a radio resource configuration (RRC) connection reconfiguration message from the first network entity, the RRC connection reconfiguration message generated based on cell history information for the UE and the measurement report message; and

transmitting, by the UE, a RRC connection reconfiguration complete message to a second network entity.
The method of claim 1, wherein the measurement report message includes reference signal received power (RSRP) information.
The method of claim 1, wherein the cell history information corresponds to a UE history information element transmitted in a handover request message.
The method of claim 1, wherein the cell history information indicates a cell ID and a stay time for each cell of a past number of cells to which the UE has been attached.
The method of claim 1, wherein the UE is in an RRC connected state.
The method of claim 1, wherein the first network entity is a small cell, and wherein the second network entity is a macro cell.
An apparatus configured for wireless communication, the apparatus comprising:

at least one processor; and

a memory coupled to the processor, the processor is configured to:

transmit, by a user equipment (UE) , a measurement report message to a first network entity;

receive, by the UE, a RRC connection reconfiguration message from the first network entity, the RRC connection reconfiguration message generated based on cell history information for the UE and the measurement report message; and

transmit, by the UE, a RRC connection reconfiguration complete message to a second network entity.
The apparatus of claim 7, further comprising:

determining, by the UE, a reference signal received power (RSRP) for the first network entity

determining, by the UE, to send the measurement report message based on the RSRP being less than a threshold.
The apparatus of claim 7, wherein the second network entity has a lower RSRP than the first network entity.
The apparatus of claim 7, wherein the second network entity has a reference signal received power (RSRP) greater than a RSRP threshold.
The apparatus of claim 7, further comprising, prior to transmitting the measurement report message:

transferring, by the UE, from a previous small cell to the first network entity based on a previous cell stay time being greater than a cell stay time threshold.
The apparatus of claim 7, further comprising, after to transmitting the RRC connection reconfiguration complete message:

staying, by the UE, attached to the second network entity while a reference signal received power (RSRP) of the second network entity is above a threshold.
A method of wireless communication comprising:

receiving, by a network entity, a handover request message from a second network entity, the handover request message including cell history information for a user equipment (UE) ;

receiving, by the network entity, a measurement report message from the UE;

determining, by the network entity, to perform a handover operation for the UE based on the cell history information and the measurement report message; and

transmitting, by the network entity, a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information.
The method of claim 13, further comprising:

receiving, by the network entity, a handover request acknowledgment message from the second network entity; and

transmitting, by the network entity, a radio resource configuration (RRC) connection reconfiguration message to the UE responsive to the handover request acknowledgment message.
The method of claim 13, wherein the measurement report message includes reference signal received power (RSRP) information.
The method of claim 13, wherein the cell history information corresponds to a UE history information element.
The method of claim 13, wherein the cell history information indicates a cell ID and a stay time for each cell of a past number of cells to which the UE has been attached.
The method of claim 13, wherein the network entity is a first small cell, wherein the second network entity is a second small cell.
The method of claim 13, wherein the third network entity is a macro cell.
The method of claim 13, wherein determining to perform the handover operation is based on a cell stay time for a number of past cells and based on a reference signal received power (RSRP) for the UE for the second network entity.
The method of claim 13, wherein determining to perform the handover operation for the UE based on the cell history information includes:

determining a number of cells to evaluate for stay time based on a cell number threshold;

determining a stay time for each cell of a past number of cells based on the cell history information;

comparing the stay time for each cell to a stay time threshold; and

responsive to determining that the stay time for each cell of the past number of cells is lower than the stay time threshold, determining to perform the handover operation.
The method of claim 21, determining to perform the handover operation for the UE based on the cell history information further includes:

determining a first reference signal received power (RSRP) for the network entity for the UE;

determining a second RSRP for the third network entity for the UE;

comparing the first RSRP to the second RSRP; and

responsive to determining that the first RSRP is higher than second RSRP, determining to perform the handover operation.
An apparatus configured for wireless communication, the apparatus comprising:

at least one processor; and

a memory coupled to the processor, the processor is configured to:

receive, by a network entity, a handover request message from a second network entity, the handover request message including cell history information for a user equipment (UE) ;

receive, by the network entity, a measurement report message from the UE;

determine, by the network entity, to perform a handover operation for the UE based on the cell history information and the measurement report message; and

transmit, by the network entity, a second handover request message to a third network entity based on determining to perform the handover operation for the UE based on the cell history information.
The apparatus of claim 23, wherein determining to perform the handover operation for the UE based on the cell history information includes:

determining a reference signal received power (RSRP) for the third network entity for the UE; and

comparing the RSRP to a macro cell RSRP threshold, wherein determining to perform the handover operation is further based on the RSRP exceeding the macro cell RSRP threshold.
The apparatus of claim 23, wherein the past number of cells corresponds to a number of small cells to which the UE was attached.
The apparatus of claim 23, wherein determining to perform the handover operation for the UE based on the cell history information includes:

determining a number of cells to test for stay time based on a cell number threshold;

determining an average stay time for a past number of cells;

comparing the average stay time to a stay time threshold; and

responsive to determining that the average stay time is lower than the stay time threshold, determining to perform the handover operation.
The apparatus of claim 23, wherein determining to perform the handover operation for the UE based on the cell history information includes:

determining a last cell stay time for a last cell;

comparing the last cell stay time for each to a last stay time threshold; and

responsive to determining that the last cell stay time to is less than the last cell stay time threshold, determining to perform the handover operation.
The apparatus of claim 23, wherein determining to perform the handover operation for the UE based on the cell history information includes:

determining a number of cells to test for stay time based on a cell number threshold;

determining a stay time for each cell of a past number of cells;

comparing the stay time for each to a stay time threshold;

responsive to determining that the stay time for each cell of the past number of cells is greater than the stay time threshold, comparing a last cell stay time to a second stay time threshold; and

responsive to determining that last cell stay time to is less than the second stay time threshold, determining to perform the handover operation.
The apparatus of claim 23, further comprising, prior to receiving the measurement report message:

receiving, by the network entity from a previous small cell, a previous handover request message;

transmitting, by the network entity, a previous handover request acknowledgment message to the previous small cell; and

receiving, by the network entity, a previous radio resource configuration (RRC) connection reconfiguration complete message from the UE.
The apparatus of claim 23, wherein the UE is in a radio resource configuration (RRC) connected state.