WO2018018513A1

WO2018018513A1 - Method and apparatus for signal characteristics aided handover

Info

Publication number: WO2018018513A1
Application number: PCT/CN2016/092105
Authority: WO
Inventors: Gaoshan LI; Congchong Ru; Jie Mao; Jintao HOU; Xiaoyu Li; Tom Chin; Yongle WU
Original assignee: Qualcomm Incorporated
Priority date: 2016-07-28
Filing date: 2016-07-28
Publication date: 2018-02-01

Abstract

Techniques for reducing the occurrence of ping-pong handovers in wireless communications are described herein. An example method may include determining, by a user equipment (UE), at least a signal characteristic of one or more signals received from a serving cell. In an aspect, the method may include determining whether at least the signal characteristic indicates that the UE is within a region of a location underneath an antenna of a base station providing the serving cell. In another aspect, the method may include delaying, by the UE, a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region.

Description

[Title established by the ISA under Rule 37.2] METHOD AND APPARATUS FOR SIGNAL CHARACTERISTICS AIDED HANDOVER

BACKGROUND

Field

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to techniques for managing handovers using signal characteristics.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE) . LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP) . LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

Some issues in handover procedures for a user equipment (UE) may include, for example, call drops and/or big real-time transport protocol (RTP) package (s) loss, which may occur when the UE is located at the bottom or near the bottom of a base station’s (e.g., an eNB) antenna, especially when the UE is moving very fast (e.g., in a high-speed train or vehicle) . For example, in a typical high-speed train (HST) coverage, there may be about 15 dB signal degradation at the bottom of a base station’s (e.g., an eNB) antenna. At such location, at least one neighbor cell’s signal level may be higher than a current serving cell, and the UE may continuously handover between the at least one neighbor cell and the current serving cell as the UE moves into and outside of the location at the bottom or near the bottom of the base station antenna. In an example, this can be referred to as ping-pong handover between the serving cell and neighbor cell. In an aspect, RTP package (s) loss in HST scenario happens mostly for ping-pong handover, and can be, for example, nearly 50％. In voice and video communications, quality usually dictates whether the user experience is a good or bad one, and Mean Opinion Score (MOS) is a numerical method of expressing voice and video quality. In an aspect, big RTP package (s) loss may harm the MOS of a voice over IP (VoIP) service (e.g., a voice over LTE (VoLTE) call) during ping-pong handover.

Therefore, improvements during UE handovers may be desirable.

SUMMARY

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

According to an example, a method for managing handovers using at least a signal characteristic is provided. The method includes determining, by a user equipment (UE) , at least a signal characteristic of one or more signals received from a serving cell, determining whether at least the signal characteristic indicates that the UE is within a region of a location underneath an antenna of a base station providing the serving cell, and delaying, by the UE, a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region.

In another example an apparatus (e.g., a UE) for managing handovers using at least a signal characteristic is provided. The apparatus includes means for determining at least a signal characteristic of one or more signals received from a serving cell, means for determining whether at least the signal characteristic indicates that the apparatus is within a region of a location underneath an antenna of a base station providing the serving cell, and means for delaying a handover of the apparatus from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the apparatus is within the region.

In another example, an apparatus (e.g., a UE) for managing handovers using at least a signal characteristic is provided. The apparatus may include a memory configured to store instructions, and at least one processor coupled to the memory. The at least one processor and the memory are configured to determine at least a signal characteristic of one or more signals received from a serving cell, determine whether at least the signal characteristic indicates that the apparatus is within a region of a location underneath an antenna of a base station providing the serving cell, and delay a handover of the apparatus from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the apparatus is within the region.

In a further example, a computer-readable medium (e.g., a non-transitory computer-readable medium) associated with at least one processor storing computer executable code for managing handovers using at least a signal characteristic is provided. The computer-readable medium includes computer executable code to determine at least a signal characteristic of one or more signals received from a serving cell, determine whether at least the signal characteristic indicates that a user equipment (UE) is within a region of a location underneath an antenna of a base station providing the serving cell, and delay a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIGs. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DL frame structure, DL channels within the DL frame structure, an UL frame structure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of an evolved NodeB (eNB) and user equipment (UE) in an access network.

FIG. 4 is a diagram illustrating an example of relation between antenna patterns, RSSI and frequency error variation when a UE is moving along multiple base stations.

FIG. 5 is a flow diagram illustrating an example method of managing handovers using at least a signal characteristic.

FIG. 6 is a flowchart of an example algorithm to manage handovers using at least a signal characteristic and reduce the occurrence of a ping-pong handover.

FIG. 7 is a flowchart of an example algorithm to estimate power levels and an antenna bottom position of a base station.

FIG. 8 is a flowchart of an example algorithm to find peaks and troughs for estimating power levels and an antenna bottom position of a base station.

FIG. 9 is a flowchart of an example algorithm to estimate an antenna bottom position and timing of a base station.

FIG. 10 is a list of example parameter settings in high-speed wireless communications according to one or more of the presently described aspects.

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 represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs) , central processing units (CPUs) , application processors, digital signal processors (DSPs) , reduced instruction set computing (RISC) processors, systems on a chip (SoC) , baseband processors, field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more example embodiments, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

Described herein are various aspects related to reducing the possibility of occurrence of a ping-pong handover. In an aspect, a method, computer-readable medium, and/or apparatus are proposed to operate to avoid or delay a handover when a user equipment (UE) is located in a region underneath an antenna of a base station (also referred to herein as an antenna bottom) . The signal degradation duration under the antenna may be short, as such, avoiding handover at this location may reduce additional RTP packet (s) loss that may otherwise be introduced by a ping-pong handover. In another aspect, when the UE performs handover to a new cell, the UE may avoid a second possible ping-pong handover by avoiding camping on the previous cell when the UE is located in a region underneath a new antenna of the new cell.

In an aspect, the method may include using signal characteristics, for example, frequency error, frequency offset, timing offset, power level offset, reference signal received power (RSRP) drop rate, RSRP absolute level, relative RSRP drop amount, received signal strength indicator (RSSI) , RSSI absolute level, reference signal received quality (RSRQ) , RSRQ absolute level, signal-to-noise ratio (SNR) , signal to interference plus noise ratio (SINR) , RTP package loss rate, etc., to estimate a timing window that the UE is located within the region underneath a base station’s antenna. The signal characteristics include other characteristics and are not limited to those mentioned above.

In an aspect, when the UE moves fast (e.g., in a high-speed train or vehicle) , current handover procedure may be not quick enough to make the UE handover to a neighbor cell before the serving cell signal power/quality degrades below an acceptable level. In another aspect, when the UE handover to a neighbor cell with much higher signal power level than the old cell, there may be a SNR jump. If the UE can do the handover earlier, the average SNR of the current serving cell around the handover point may be improved.

In an aspect, a proposed method may include to handover to neighbor cell more quickly. For example, the handover may happen once one or more parameters of a neighbor cell signal achieve a threshold, where the threshold may be higher or lower than those configured (e.g., at the UE) for performing handover, sending measurement reports, etc..

In an aspect, the algorithms discussed herein may run or operate very fast, for example, about 10 millisecond per cycle (or per round, per algorithm, etc. ) .

FIG. 1 is a diagram illustrating an example of a wireless communications system and a wireless communications system 100. The wireless communications system 100 (also referred to as a wireless wide area network (WWAN) ) includes base stations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The base stations 102 may include macro cells (high power cellular base station) and/or small cells (low power cellular base station) . The macro cells include eNBs. The small cells include femtocells, picocells, and microcells.

The base stations 102 (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) ) interface with the EPC 160 through backhaul links 132 (e.g., S1 interface) . In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160) with each other over backhaul links 134 (e.g., X2 interface) . The backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102' may have a coverage area 110' that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved NodeBs (eNBs) (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) . The communication links 120 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 /UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL) . The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell) .

The wireless communications system 100 may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 /AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

The small cell 102' may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102' may employ LTE and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cell 102', employing LTE in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. LTE in an unlicensed spectrum may be referred to as LTE-unlicensed (LTE-U) , licensed assisted access (LAA) , or MuLTEfire.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service (PSS) , and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN) , and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The base station may also be referred to as a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , or some other suitable terminology. The eNB 106 provides an access point to the EPC 160 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a smart device, a wearable device, or any other similar functioning device. The UE 104 may also be referred to as a station, a mobile station, 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, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 and/or the base station 102 may be configured to manage handover to reduce the occurrence of ping-pong handovers and/or to handover to a neighbor cell more quickly, with the help of a handover management component 198. In an aspect, the handover management component 198 may include an antenna bottom estimate component 192, a cell evaluation component 194, and a delay and timing component 196, which are shown and described in detail in FIG. 4.

FIG. 2A is a diagram 200 illustrating an example of a DL frame structure in LTE. FIG. 2B is a diagram 230 illustrating an example of channels within the DL frame structure in LTE. FIG. 2C is a diagram 250 illustrating an example of an UL frame structure in LTE. FIG. 2D is a diagram 280 illustrating an example of channels within the UL frame structure in LTE. The concepts described herein may be used in an LTE configuration and/or using other wireless communication technologies, which may have a different frame structure and/or different channels. In LTE, a frame (10ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent the two time slots, each time slot including one or more time concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs) ) . The resource grid is divided into multiple resource elements (REs) . In LTE, for a normal cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols (for DL, OFDM symbols； for UL, SC-FDMA symbols) in the time domain, for a total of 84 REs. For an extended cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRS) (also sometimes called common RS) , UE-specific reference signals (UE-RS) , and channel state information reference signals (CSI-RS) . FIG. 2A illustrates CRS for

antenna ports

0, 1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively) , UE-RS for antenna port 5 (indicated as R₅) , and CSI-RS for antenna port 15 (indicated as R) . FIG. 2B illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol 0 of slot 0, and carries a control format indicator (CFI) that indicates whether the physical downlink control channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustrates a PDCCH that occupies 3 symbols) . The PDCCH carries downlink control information (DCI) within one or more control channel elements (CCEs) , each CCE including nine RE groups (REGs) , each REG including four consecutive REs in an OFDM symbol. A UE may be configured with a UE- specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subset including one RB pair) . The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK) /negative ACK (NACK) feedback based on the physical uplink shared channel (PUSCH) . The primary synchronization channel (PSCH) is within symbol 6 of slot 0 within

subframes

0 and 5 of a frame, and carries a primary synchronization signal (PSS) that is used by a UE to determine subframe timing and a physical layer identity. The secondary synchronization channel (SSCH) is within symbol 5 of slot 0 within

subframes

0 and 5 of a frame, and carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI) . Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) is within

symbols

0, 1, 2, 3 of slot 1 of subframe 0 of a frame, and carries a master information block (MIB) . The MIB provides a number of RBs in the DL system bandwidth, a PHICH configuration, and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs) , and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the eNB. The UE may additionally transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by an eNB for channel quality estimation to enable frequency-dependent scheduling on the UL. FIG. 2D illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth. The PUCCH carries uplink control information (UCI) , such as scheduling requests, a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a rank indicator (RI) , and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR) , a power headroom report (PHR) , and/or UCI.

FIG. 3 is a block diagram of an eNB 310 in communication with a UE 350 (or a UE 104 in FIG. 1) in an access network. In the DL, IP packets from the EPC 160 may be provided to a controller/processor 375. The controller/processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs) , RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release) , inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting； PDCP layer functionality associated with header compression /decompression, security (ciphering, deciphering, integrity protection, integrity verification) , and handover support functions； RLC layer functionality associated with the transfer of upper layer packet data units (PDUs) , error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs) , re-segmentation of RLC data PDUs, and reordering of RLC data PDUs； and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs) , demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 310 on the physical channel. The data and control signals are then provided to the controller/processor 359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

In an aspect, the controller/processor 359 and/or the memory 360 may be associated with or communicate with the handover management component 198 at UE 350 or UE 104 that managing handovers using at least a signal characteristic to reduce the occurrence of ping-pong handovers. In another aspect, the controller/processor 359 and/or the memory 360 may configured to perform part or all of the functions and features of the handover management component 198, and its sub-components, for example, the antenna bottom estimate component 192, the cell evaluation component 194, or the delay and timing component 196.

Similar to the functionality described in connection with the DL transmission by the eNB 310, the controller/processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting； PDCP layer functionality associated with header compression /decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ； RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs； and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by the eNB 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from the controller/processor 375 may be provided to the EPC 160. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

In an aspect, the controller/processor 375 and/or the memory 376 may be associated with or communicate with the handover management component 198 at eNB 310 or base station 102 (FIG. 1) that managing handovers using at least a signal characteristic to reduce the occurrence of ping-pong handovers. In another aspect, the controller/processor 375 and/or the memory 376 may configured to perform part or all of the functions and features of the handover management component 198, and its sub-components, for example, the antenna bottom estimate component 192, the cell evaluation component 194, or the delay and timing component 196.

FIG. 4 is a diagram illustrating an example of a relationship between antenna patterns, RSSI and frequency error variation when a UE (e.g., UE 104) is moving along multiple base stations (e.g., base stations 102) . In an aspect of a high-speed train (HST) coverage, there may be some signal degradation (e.g., about 15 dB) when the UE 104 is in a location within a region of the bottom of an antenna of one or more of the base stations 102. In this regard, the UE 104 may suffer from low signal power and/or data packets loss at this location, which may lead to call or data drops. At this location, at least one neighbor cell’s signal level sometimes may be higher than the current serving cell, e.g., as shown in blue circles in FIG. 4. Due to the variation in signal levels of the serving cell and neighbor cell, ping-pong handovers may occur as described. Ping-pong handovers may cause real-time transport protocol (RTP) package (s) loss (e.g., in HST scenarios) . In another aspect, big RTP package (s) loss may harm the Mean Opinion Score (MOS) of a voice over IP (VoIP) service (e.g., a voice over LTE (VoLTE) call) where ping-pong handover happens.

In an aspect, when the UE 104 is passing from the region underneath an antenna of a first base station (e.g., base station 102) , and moves outside of the region (e.g., the cross point of the green and orange lines) of two antenna (e.g., the antenna of the first base station and an antenna of a second base station (e.g., base station 102)) , a frequency tracking loop (FTL) shows that frequency error may change from positive bias to negative bias (as shown at the bottom of FIG. 4) . In an aspect, the UE 104 may keep moving toward a region underneath the antenna bottom of the second base station (e.g., base station 102) where highlighted by the second blue circle. Again, the frequency tracking loop (FTL) shows that frequency error may change from positive bias to negative bias.

In some aspects, the UE 104 and/or the base stations 102 may be configured to manage handover to reduce the occurrence of ping-pong handovers and/or to handover to a neighbor cell more quickly, with the assistance of a handover management component 198, as described in further detail below. In an aspect, the handover management component 198 may include an antenna bottom estimate component 192, a cell evaluation component 194, and a delay and timing component 196. For example, a processor of the UE 104 (e.g., a RX processor 359, controller\processor 359, TX processor 368, etc. ) may be configured to implement and/or execute one or more functions associated with the handover management component 198 or its subcomponents described further herein. In addition, for example, a memory of the UE 104 (e.g., memory 360) may store instructions or parameters for implementing and/or executing the handover management component 198 or its subcomponents described further herein. Moreover, in an example, UE 104 can include a transceiver (e.g., RX/TX 354) and/or one or more related RF components (e.g., a power amplifier, low-noise amplifier, one or more filters, etc. ) that can communicate signals via one or more antennas (e.g., antennas 352) in performing one or more functions described herein.

FIG. 5 is a flow diagram illustrating an example method 500 of managing handovers using at least a signal characteristic to reduce the occurrence of ping-pong handovers. The method 500 may be performed by a UE and/or an eNB (e.g., UE 104 or eNB 102) . At 502, the method 500 may include determining at least a signal characteristic of one or more signals received from a serving cell. For example, handover management component 198 of UE 104 may be configured to detect and/or determine one or more signal characteristics which may include at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a RTP package loss rate.

At 504, the method 500 may include determining whether at least the signal characteristic indicates that a UE (e.g., UE 104) is within a region of a location underneath an antenna of a base station (e.g., eNB 102) providing the serving cell. For example, antenna bottom estimate component 192 and/or cell evaluation component 194 may be configured to determine and/or estimate the UE’s current location based on one or more signal characteristics of the received signals from the serving cell and/or one or more neighbor cells.

At 506, the method 500 may include delaying a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region. For example, delay and timing component 196 may be configured to calculate the UE’s instant, filtered or average speeds, to determine a plurality of time thresholds (e.g., MaxBottomTimeThres, BottomTimeOutThres) , and to set a plurality of timers (e.g., MaxBottomTimer, BottomTimeoutTimer) for managing the UE’s handover.

FIG. 6 is a flowchart of an example algorithm, which is shown by method 600, to reduce or prevent (e.g., by a UE 104) the occurrence of a ping-pong handover. In an aspect, at block 602, the method 600 may include starting an evaluation. For example, this can include configuring the cell evaluation component 194 of the UE 104 to start with an evaluation of a current serving cell and/or at least a neighbor cell which the UE 104 may potentially handover to or camp on, where the evaluation may include measuring one or more signal characteristics of signals received from the cell (s) . In an aspect, at block 602, the method 600 may configure the cell evaluation component 194 to initiate a list of prohibit cells which may be set to “NULL. ” The prohibit list may include cells having one or more restricted handover conditions. For example, after a handover happens at the UE 104, the original source/serving cell may be marked as “Cell P” and included in the prohibit list. In an aspect, when the “Cell P” is evaluated by the cell evaluation component 194 as a neighbor cell and may potentially camp on as a new serving cell, more restricted handover condition (s) may be used to prevent ping-pong handover by setting and/or modifying one or more parameters/values (e.g., THoffset or TTTcoefficient) , in order to change or adjust the one or more triggering events and/or conditions for a handover to a neighbor cell

In an aspect, at block 604, the method 600 may include determining whether the current cell being evaluated is the last neighbor cell in a list of neighbor cells to be evaluated. For example, this can include configuring the cell evaluation component 194 of the UE 104 to determine whether a neighbor cell is the last neighbor cell on the list to do evaluation. For example, the UE 104 may monitor and/or detect a plurality of neighbor cells, and the neighbor cell list at the UE 104 may include one or more cells which the UE 104 may potentially camp on.

In an aspect, at block 606, the method 600 may include ending the evaluation if the current cell being evaluated is the last neighbor cell in the list. For example, this can include configuring the cell evaluation component 194 to end the evaluation on a condition that the cell evaluation component 194, at block 604, determines that the neighbor cell is the last neighbor cell in the list.

In an aspect, at block 608, the method 600 may include evaluating the neighbor cell N. This can include configuring the cell evaluation component 194 to proceed/continue to evaluate the neighbor cell N, where N is an index of the current neighbor cell being evaluated, on a condition that the cell evaluation component 194, at block 604, determines that the neighbor cell N is not the last neighbor cell in the list. For example, evaluating the neighbor cell N may include determining one or more signal characteristics of one or more signals associated with neighbor cell N (e.g., RSSI, RSRP, RSRQ, SNR, etc. of the one or more signals as received at UE 104) .

In an aspect, at block 610, the method 600 may include determining whether the UE 104 is within a region of a location underneath an antenna of a base station providing the serving cell. For example, at block 610, the antenna bottom estimate component 192 of the UE 104 can determine whether the UE 104 is within the region of the location underneath the antenna bottom of base station 102. In an aspect, the determination at block 610 may include one or more algorithms discussed herein, for example in FIGs. 7-9. In an example, antenna bottom estimate component 192 can determine whether one or more of the signal characteristics determined in evaluating the neighbor cell N (e.g., by cell evaluation component 194) indicate that the UE 104 is within the region. For example, as described further herein, this may include comparing one or more of the signal characteristics to one or more corresponding thresholds (e.g., over a period of time) .

In an aspect, at block 610, when the antenna bottom estimate component 192 determines that the UE 104 is not within the region of a location underneath the antenna of the base station 102 providing the serving cell, at block 612, the method 600 may include performing a fast measurement report evaluation (fastMREvaluuation) . For example, this can include configuring the handover management component 198 to proceed with a fast evaluation at the UE 104, which may trigger generating and/or transmitting at least a measurement report to facilitate to potentially handover from the current serving cell to the neighbor cell N (as the target cell) . In an example, the fastMREvaluation may use one or more parameters as configured for the UE 104 (e.g., by a base station or other network component) for performing handover. In another example, the fastMREvaluation may use one or more parameters modified to result in a faster handover (e.g., decreasing a signal threshold for a target cell to facilitate handover, reporting a higher parameter value for a signal power/quality, etc. ) . After the UE 104 sends the measurement report to the network (e.g., the current serving cell) , the handover management component 198 of the UE and/or the network may operate a handover quicker, as the network (e.g., the current serving cell) receives the measurement report triggered by the fast evaluation “FastMREvaluation. ”

In an aspect, at block 610, when the antenna bottom estimate component 192 determines that the UE 104 is within the region of a location underneath the antenna of the base station 102 providing the serving cell, at block 614, the method 600 may include performing a slow measurement report evaluation (slowMREvaluation) . This can include configuring the handover management component 198 to proceed with a slow evaluation at the UE 104 which may, for example, trigger at least a measurement report to facilitate to handover from the current serving cell to the neighbor cell N at a later point. For example, handover management component 198 in this regard may modify one or more parameters related to determining to send a measurement report (e.g., increase a threshold for a signal power/quality of a neighbor cell that causes sending the measurement report, increase a time-to-trigger the handover when the signal power/quality achieves the threshold, etc. ) . In another aspect, the method 600 may configure the handover management component 198 to determine one or more triggering events and/or conditions for sending the at least one measurement report to the network (e.g., base station 102 providing the serving cell) .

In an aspect, at block 614, the method 600 may include determining, setting up, adjusting, or modifying a plurality of parameters related to the above mentioned one or more triggering events and/or conditions. For example, the method 600 may configure the handover management component 198 to adjust or modify one or more parameters (e.g., threshold offset (THoffset) , time-to-trigger coefficient (TTTcoefficient) , etc. ) in order to change or adjust the one or more triggering events and/or conditions. The adjustment or modification of the one or more parameters may include increase or decrease at least one detection threshold (or trigger threshold) for at least a signal characteristic that causes the one or more triggering events and/or conditions. The at least one detection threshold (or trigger threshold) may include or be related, but not limited to: a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , a RTP package loss rate, or other parameters for indicating signal quality.

In an aspect, the one or more parameters may include a “THoffset” which is an additional offset set by the UE 104. In an aspect, the UE 104 may add this on a legacy measurement report threshold. For example, the network may configure an A3 measurement report EVENT (e.g., in LTE) as 3dB, such that when the neighbor cell N’s RSRP is 3dB larger than the serving cell’s RSRP, a measurement report may be triggered and the UE 104 may send the measurement report. After adjusting or modifying the one or more parameters with an additional THoffset (e.g., 1dB～6dB) , the UE 104 may delay sending the measurement report, and wait until the neighbor cell N’s RSRP is “3dB+Thoffset” larger than the serving cell’s RSRP, to send the measurement report.

In another aspect, the one or more parameters may include a “TTTcoefficient” (e.g., 2 or 3) which is a time-to-trigger coefficient set by the UE 104. In an aspect, the network may configure time-to-trigger (TTT) for measurement report evaluation. For example, TTT may be configured to be 1 second, a measurement report may be triggered and the UE 104 may send the measurement report when A3 measurement report EVENT is detected for 1 second. After adjusting or modifying the one or more parameters with extended time period (e.g., multiplying the TTTcoefficient on TTT) , the UE 104 may delay sending the measurement report, and wait until the A3 measurement report EVENT is fulfilled for TTT*TTTcoefficient, to send the measurement report.

In an aspect, after the UE 104 sends out the measurement report to the network (e.g., the current serving cell) , the handover management component 198 of the UE and/or the network may delay a handover, and the network (e.g., the current serving cell) receives the measurement report triggered by the slow evaluation “SlowMREvaluation” .

In an aspect, at block 616, the method 600 may include determining whether the list including cells having one or more restricted handover conditions is empty or not, and whether the neighbor cell N (e.g., the cell that UE 104 is currently evaluating) is on the list. In an aspect, the method 600 may configure the cell evaluation component 194 to determine whether the neighbor cell N is on the cell list with one or more restricted handover conditions.

In an aspect, when the method 600, at block 616, determines that the list including cells having one or more restricted handover conditions is empty, or that the list is not empty, but the neighbor cell N is not present on the cell list, the method 600, at block 618, may set the parameters to be less restrictive than in the alternative case. For example, this can include configuring the UE 104 with one or more parameters in a less restricted condition to trigger a measurement report. For example, the method 600 may configure the handover management component 198 and/or the delay and timing component 196 to adjust or modify one or more parameters (e.g., THoffset or TTTcoefficient) in order to change or adjust the one or more triggering events and/or conditions. For example, the network may configure a triggering event, condition, or threshold (e.g., an A3 measurement report EVENT) as 3dB, and the handover management component 198 and/or the delay and timing component 196 may be configured to add an addition THoffset (e.g., 3dB) to the triggering event, condition, or threshold. As such, the delay and timing component 196 of the UE 104 may delay sending the measurement report, and may refrain from sending the measurement report until the neighbor cell N’s RSRP is “3dB+Thoffset” larger than the serving cell’s RSRP.

In another example at block 618, the method 600 may configure the UE 104 with one or more parameters in a less restricted condition to trigger a measurement report. The network may configure a triggering event, condition, or threshold (e.g., an A3 measurement report EVENT) , for instance, a time-to-trigger (TTT) to be 1 second, and a measurement report may be triggered and the UE 104 may send the measurement report when the A3 measurement report EVENT is fulfilled for 1 second. In an aspect, the handover management component 198 and/or the delay and timing component 196 may be configured to set a time-to-trigger coefficient “TTTcoefficient” . After adjusting or modifying the one or more parameters with an extended time period (e.g., multiplying the TTTcoefficient on TTT) , the delay and timing component 196 of the UE 104 may delay sending the measurement report, and refrain from sending the measurement report until the A3 measurement report EVENT is fulfilled for TTT*TTTcoefficient, to send the measurement report. In an example, the TTTcoefficient is set to two (2) , and the new time threshold TTT*TTTcoefficient is double the original TTT setting.

In an aspect, when the method 600, at block 616, determines that the neighbor cell N is present on the cell list having one or more restricted handover conditions, the method 600, at block 620, may set the parameters to be more restrictive than in the alternative case. For example, this can include configuring the UE 104 with one or more parameters in a more restricted condition to trigger a measurement report. For example, the method 600 may configure the handover management component 198 and/or the delay and timing component 196 to adjust or modify one or more parameters (e.g., THoffset or TTTcoefficient) in order to change or adjust the one or more triggering events and/or conditions. For example, the network may configure a triggering event, condition, or threshold (e.g., an A3 measurement report EVENT) as 3dB, and the handover management component 198 and/or the delay and timing component 196 may be configured to add an additional THoffset (e.g., 3dB～6dB) to the triggering event, condition, or threshold. As such, the delay and timing component 196 of the UE 104 may delay sending the measurement report, and may refrain from sending the measurement report until the neighbor cell N’s RSRP is “3dB+THoffset” larger than the serving cell’s RSRP.

In another example at block 620, the method 600 may configure the UE 104 with one or more parameters in a more restricted condition to trigger a measurement report. The network may configure a triggering event, condition, or threshold (e.g., an A3 measurement report EVENT) , for instance, a time-to-trigger (TTT) to be 1 second, and a measurement report may be triggered and the UE 104 may send the measurement report when the A3 measurement report EVENT is fulfilled for 1 second. In an aspect, the handover management component 198 and/or the delay and timing component 196 may be configured to set a time-to-trigger coefficient “TTTcoefficient” . After adjusting or modifying the one or more parameters with an extended time period (e.g., multiplying the TTTcoefficient on TTT) , the delay and timing component 196 of the UE 104 may delay sending the measurement report, and may refrain from sending the measurement report until the A3 measurement report EVENT is fulfilled for TTT*TTTcoefficient, to send the measurement report. In an example, the TTTcoefficient is set to three (3) , and the new time threshold TTT*TTTcoefficient is triple the original TTT setting.

FIG. 7 is a flowchart of an example algorithm to determine whether a UE is within a region underneath an antenna of a base station 102 (e.g., as in block 610 of method 600 in FIG. 6) . The antenna bottom position may be, for example, a region of a location underneath an antenna of base station 102 that provides a serving cell to the UE 104. In some aspects, the example algorithm is shown by method 700, and may include the algorithms shown in FIG. 8 and/or in FIG. 9. In an aspect, at block 702, the method 700 may include measuring and/or determining at least a signal characteristic of one or more signals received from a serving cell and/or at least a neighbor cell. This may include configuring cell evaluation component 194 for measuring and/or determining at least the signal characteristic. The at least a signal characteristic may include frequency error, frequency offset, timing offset, power level offset, reference signal received power (RSRP) drop rate, RSRP absolute level, relative RSRP drop amount, received signal strength indicator (RSSI) , RSSI absolute level, reference signal received quality (RSRQ) , RSRQ absolute level, signal-to-noise ratio (SNR) , signal to interference plus noise ratio (SINR) , or RTP package loss rate.

In an aspect, at block 704, the method 700 may include introducing one or more filters that may smooth the measured or determined signal characteristic of one or more signals received at UE 104 (at block 702) and generate a more accurate bottom estimation shown, for example, in FIG. 9. This may include configuring the cell evaluation component 194 to introduce the one or more filters. At block 704, two example equations are introduced:

filterRsrp (i) ＝ α × rsrp (i) + (1-α) × filterRsrp (i-1) (1)

filterFreqErr (i) ＝ β × freqErr (i) + (1-β) × filterFreqErr (i-1) (2)

In an aspect, at block 706, the method 700 may include searching and determining at least a peak value and/or a trough value of filterFreqErr (i) , which is calculated based on the Equation (2) at block 704. For example, cell evaluation component 194 can search and determine at least the peak value and/or trough value. In an aspect, the UE 104 may put the peak and trough value (s) or result (s) into freqErrPeakTrough [N] circular vector (with hysteresis FREQERRHYST) , as described further herein with respect to FIG. 8.

In an aspect, at block 708, the method 700 may include calculating an average frequency error peak value, freqErrpeakAvg, and an average frequency error trough value, freqErrTroughAvg. For example, cell evaluation component 194 can calculate freqErrpeakAvg and freqErrTroughAvg, which may include averaging values in freqErrPeakTrough [N] (e.g., using a mean or median average of the values, etc. ) .

In an aspect, at block 710, the method 700 may include calculating an instant speed and/or a filtered speed value of movement of the UE 104. For example, cell evaluation component 194 can calculate the speed value based on the following example equations:

CurrentSpeed ＝ c /carrierFrequence× ( (freqErrpeakAvg –freqErrTroughAvg) /2) (3)

Speed ＝ δ × CurrentSpeed + (1-δ) × Speed (4)

In an aspect, at block 712, the method 700 may include calculating one or more thresholds used for bottom estimation according to speed. For example, cell evaluation component 194 can calculate the one or more threshold based on the following equations:

BottomTimeOutThres ＝ Round (BottomTimeOutDistance/speed*100) (5)

MaxBottomTimeThres＝Round (MaxBottomDistance/speed*100) (6)

rsrpSlopThres＝rsrpSlopPerMeter*speed/100 (7)

In an aspect, similar to block 706, at block 714, the method 700 may include searching and determining at least a peak value and/or a trough value of filterRsrp (i) . For example, cell evaluation component 194 can calculate the speed value, which can be calculated based on the Equation (1) at block 704. In an aspect, the UE 104 may put the peak and trough value (s) or result (s) into circular vector rsrpPeakTrough [N] , and may be determined or modified with a hysteresis for searching the peaks and troughs (e.g., RSRPHYST) .

In an aspect, at block 716, the method 700 may include estimating the “antenna bottom” or “Non-bottom” status, according to at least one of filterRsrp (i) , filterFreqErr (i) , rsrpPeakTrough [] , or freqErrPeak [] . For example, antenna bottom estimate component 192 can estimate the antenna bottom or non-bottom status, as further described with respect to FIG. 9.

In an aspect, at block 718, the method 700 may include returning a status of “BOTTOM” or “NonBOTTOM” , which can be based on the estimation at block 716.

FIG. 8 is a flowchart of an example of a method 800 to find peaks and troughs for estimating power levels and/or an antenna bottom position of a base station in accordance with aspects described herein. In an aspect, FIG. 8 shows an example of logics to find or search peaks and troughs for sequences which used for antenna bottom estimation in the method 700 (and in FIG. 7) , for example, at block 706 and/or block 714.

In an aspect, the method 800 may include a function F (i) (and optionally with hysteresis “HYST” ) to find or search peaks and/or troughs of at least a signal characteristic of the received signals. For example, at block 802, the method 800 may include determining the values related to the function F (i) . For example, this may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to determine the values related to the function F (i) .

At block 804, the method 800 may include determining whether F (i) is at its initial setting. For example, this may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to determine whether F (i) is at its initial setting (e.g., “I” is equal to zero (0) ) . If i＝0, the method 800 may proceed to block 806 to set the status to PEAK. Otherwise, the method 800 may proceed to block 808 to determine the current peak and trough status.

At block 806, the method 800 may include initializing a peak and trough status. For example, this may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to initialize the peak and trough status “peakTroughStatus” to PEAK, and make Peak ＝ F (0) .

At block 808, the method 800 may include determining whether the current peak and trough status is peak or trough. For example, this may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to determine whether the current peak and trough status “peakTroughStatus” is a PEAK or a Trough.

At block 810, if the at block 808 the method 800 determine that the current status is PEAK, the method 800 may determine whether the current value F (i) is larger than the peak value. For example, this may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to block 810 to determine whether the current value F (i) is bigger than the Peak value. If Yes, the method 800 may set the peak to the value of current F (i) , which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 814 and set Peak to the value of current F (i) ； if not, the method 800 may determine whether peak-F (i) is larger than a hysteresis value, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 812 and determine whether Peak-F (i) is larger than HYST. If not, the method 800 may return the circular buffer or peak and trough vector, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to block 826 to return the circular buffer or vector peakTrough [N] . Otherwise, if Yes, the current Peak value and its index may be pushed into the circular vector peakTrough [N] and the circular buffer index is moved to the next one. In addition, the method 800 may include setting a peak trough status to trough and trough to F(i) , which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to set “peakTroughStatus ＝Trough” and “Trough ＝ F (i) ” , and then, the method 800 may return the circular buffer or peak and trough vector, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 826 and return the circular buffer or vector peakTrough [N] .

At block 818, if at block 808 the method 800 determine that the current status is Trough, the method 800 may determine whether the current value F (i) is less than the trough value, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to block 818 to determine whether the current value F (i) is less than the Trough value. If Yes, the method 800 may include setting the trough value to a value of a current F(i) , which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 820 and set Trough to the value of current F (i) ； if not, the method 800 may determine whether F(i) -Trough is larger than a hysteresis, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 822 and determine whether F (i) -Trough is larger than HYST. If not, the method 800 may return the circular buffer or peak and trough vector, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to block 826 to return the circular buffer or vector peakTrough [N] . Otherwise, if Yes, the current trough value and its index may be pushed into the circular vector peakTrough [N] and the circular buffer index is moved to the next one. In addition, the method 800 may set a peak and trough status to peak and/or peak to F (i) , which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to set “peakTroughStatus ＝ PEAK” and “Peak ＝F(i) ” , and then, the method 800 may return the circular buffer or peak and trough vector, which may include configuring handover management component 198 or its sub-component antenna bottom estimate component 192 to proceed to 826 and return the circular buffer or vector peakTrough [N] .

In another aspect, the method 800 may setup a circular buffer or a circular peak and trough vector, which may include configuring handover management component 198 and/or other hardware or software components of the UE 104 to setup a circular buffer and/or a circular vector peakTrough [N] (e.g., at block 816 or block 824 in FIG. 8, or for block 912 in FIG. 9) , with the nearest or the latest history points (e.g., the nearest or the latest three or four points including peaks or troughs) which may be used for calculating a delta for at least a signal characteristic (e.g., RSRP delta) and timing delta (e.g., at block 914 in FIG. 9) . In an aspect, at block 816, at least a peak value and its index are pushed into the circular vector peakTrough [N] , and the method 800 moves the circular buffer index to the next one. Similarly, at block 824, at least a trough value and its index are pushed into the circular vector peakTrough [N] , and the method 800 moves the circular buffer index to the next one.

In an aspect, the UE 104 may record the nearest or the latest history points (e.g., the nearest or the latest three or four local points) . The points may be peaks or troughs of a signal characteristic of one or more signals received from a serving cell and/or at least a neighbor cell. The signal characteristic may include frequency error, frequency offset, timing offset, power level offset, reference signal received power (RSRP) drop rate, RSRP absolute level, relative RSRP drop amount, received signal strength indicator (RSSI) , RSSI absolute level, reference signal received quality (RSRQ) , RSRQ absolute level, signal-to-noise ratio (SNR) , signal to interference plus noise ratio (SINR) , RTP package loss rate, or RSRP slop. The UE 104 may repeat history points for a RSRP slop, or any other signal characteristic mentioned above, for current UE position calculation or estimation.

In an aspect, the method 800 may setup a circular buffer or vector, which may include configuring UE 104 to setup a circular buffer and/or a circular vector peakTrough [N] (e.g., at block 816 or block 824 in FIG. 8, or for block 912 in FIG. 9) , with the nearest or the latest history points (e.g., the nearest or the latest three or four points including peaks or troughs) which may be used for calculating a delta for at least a signal characteristic (e.g., RSRP delta) and timing delta (e.g., at block 914 in FIG. 9) . In an aspect, at block 816, at least a peak value and its index are pushed into the circular vector peakTrough [N] , and the method 800 moves the circular buffer index to the next one. Similarly, at block 824, at least a trough value and its index are pushed into the circular vector peakTrough [N] , and the method 800 moves the circular buffer index to the next one.

For example, the method 800 may determine a circular buffer, a peak value, a trough value, and/or a current RSRP, which may include configuring UE 104 to determine a circular buffer (e.g., rsrpPeakTrough [N] ) and determine or detect a peak value “P” of RSRP, a trough value “T” of RSRP, and a current RSRP value “C” . The method 800 may determine a first circular buffer status is [T1, P2, T2, C] , which means there are three previous peak and trough values, T1, P2, and T2, where C is the latest RSRP value, and has not yet been determined as a peak value P3. The method 800 may then determine a second circular buffer status is [P2, T2, P3, C] , where now the peak value P3 is found, and T1 was piped/moved out from the circular buffer. In an aspect, the UE 104 may calculate the RSRP delta and the timing delta from “C-P3” . In another aspect, if the result (s) shows that the bottom condition has not been met, the UE 104 may go to a previous item/point in the second circular buffer (e.g., T2) , calculate the RSRP delta and the timing delta from “C-T2” , and then determine whether the “BOTTOM” condition (s) (e.g., as shown in FIG. 9) has been met. The UE 104 may repeat this procedure until “BOTTOM” condition (s) has been met/fulfilled or the oldest item (e.g., P2) has been handled. In other words, for example, the UE 104 may loop all items/points in the circular buffer (e.g., rsrpPeakTrough [N] ) from the latest pointer backward to the oldest for all items/points, which has been shown, e.g., at block 912 and/or block 914 in FIG. 9.

FIG. 9 is a flowchart of an example method 900 to estimate the antenna “BOTTOM” or “NonBOTTOM” status. In an aspect, the method 900 may configure handover management component 198 or its sub-components to determine and/or perform one or more functions or features discussed herein.

In an aspect, the method 900 may determine and setup several timers which may include a MaxBottomTimer and/or a BottomTimeoutTimer. In another aspect, the method 900 may determine and setup several thresholds which may include a MaxBottomTimeThres and/or a BottomTimeOutThres. In some aspects, these timers and thresholds may be used for estimating the antenna “BOTTOM” or “NonBOTTOM” status, and may be used for the triggers for changing status. In an aspect, FIG. 9 shows an example of logic (s) used for antenna bottom estimation in the method 700 (and in FIG. 7) , for example, at block 716.

In an aspect, the method 900 may determine or estimate the maximum time duration a UE has a status indicating that it is within the region underneath the antenna (e.g., at the “BOTTOM” ) , which may include configuring the delay and timing component 196 to determine or estimate the maximum time duration the UE 104 stays at the “BOTTOM” . In an aspect, when a threshold (e.g., MaxBottomTimeThres or BottomTimeOutThresor) or a timer (e.g., MaxBottomTimer or BottomTimeoutTimer) expired, the UE 104 may still keep staying at “BOTTOM” , since the condition (s) for exiting “BOTTOM” status has not been met or fulfilled.

In an aspect, the method 900 may determine or estimate exit point (s) and/or at least one threshold where the UE 104 may exit the region, which may include configuring the delay and timing component 196 to determine or estimate exit point (s) and/or at least one threshold where the UE 104 may exit or jump out of the “BOTTOM” . In an aspect, the method 900 may configure the UE 104 to use at least a signal characteristic of one or more received signals to determine or estimate the exit point (s) and/or the at least one threshold. The signal characteristic may include, but not limited to, a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a RTP package loss rate.

FIG. 10 includes a list of example parameter settings in high-speed wireless communication systems according to one or more of the presently described aspects. In an aspect, the high-speed wireless communication systems may include or associated with an LTE wireless communication system. In an aspect, the example parameter settings may be used for managing a UE’s handovers in the LTE wireless communication system to prevent ping-pong handovers. For example, the example parameter settings may be used for showing frequency jump during ping-pong handover, FTL convergence, SNR from FTL, SNR drop during ping-pong handovers, in-band RSSI, RSSI pattern (s) within a region of a location underneath an antenna of a base station, or RSRP distribution during a ping-pong handover.

An apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of FIGs. 5-9. As such, each block in the aforementioned flowcharts of FIGs. 5-9 may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

In one configuration, as described supra, the processing system may include the TX Processor 368, the RX Processor 356, and the controller/processor 359. As such, in one configuration, at least one of the TX Processor 368, the RX Processor 356, or the controller/processor 359 may be configured to perform the functions or features recited by the aforementioned method 500, method 600, method 700, method 800, and/or method 900, or to perform each of the blocks of the algorithm in the aforementioned flowcharts of FIGs. 5-9.

In another configuration, the apparatus for wireless communication includes means for determining at least a signal characteristic of one or more signals received from a serving cell, determining whether at least the signal characteristic indicates that the apparatus is within a region of a location underneath an antenna of a base station providing the serving cell, and delaying a handover of the apparatus from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the apparatus is within the region. In an aspect, the signal characteristic, for example, may be a frequency error, a frequency offset, a timing offset, a power level offset, a reference a signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a RTP package loss rate. Alternatively, instead of delaying a handover, the apparatus for wireless communication may include means for performing a handover quicker or sooner based on determining that at least the signal characteristic indicates that the apparatus is not within a region of a location underneath an antenna of a base station. The aforementioned means may be one or more of the aforementioned components (e.g., the handover management component 198, the antenna bottom estimate component 192, the cell evaluation component 194, or the delay and timing component 196) of the apparatus and/or the processing system of the apparatus configured to perform the functions recited by the aforementioned means. As described supra, the processing system may include the TX Processor 368, the RX Processor 356, and the controller/processor 359. As such, in one configuration, the aforementioned means may be the TX Processor 368, the RX Processor 356, and the controller/processor 359 configured to perform the functions recited by the aforementioned means.

It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

Similarly, it is to be understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

As used in this application, the terms “component, ” “module, ” “system” and the like are intended to include a computer-related entity, such as but not limited to hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components can communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets, such as data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal.

Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a； b； c； a and b； a and c； b and c； and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, or of 35 U.S.C. §112 (f) , unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

Claims

A method of wireless communication, comprising:

determining, by a user equipment (UE) , at least a signal characteristic of one or more signals received from a serving cell；

determining whether at least the signal characteristic indicates that the UE is within a region of a location underneath an antenna of a base station providing the serving cell； and

delaying, by the UE, a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region.
The method of claim 1, wherein delaying the handover comprises:

determining, by the UE, at least one triggering condition for sending a measurement report to facilitate to handover； and

modifying, by the UE, one or more parameters related to the at least one triggering condition.
The method of claim 2, wherein modifying the one or more parameters comprises increasing at least one detection threshold for at least the signal characteristic that causes the at least one triggering condition.
The method of claim 3, wherein the at least one detection threshold for at least the signal characteristic comprises at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
The method of claim 2, wherein modifying the one or more parameters comprises increasing a time-to-trigger (TTT) sending of the measurement report by multiplying a time-to-trigger coefficient.
The method of claim 2, wherein modifying the one or more parameters is based on determining, by the UE, whether the target cell is in a list having one or more restricted handover conditions.
The method of claim 1, wherein determining whether at least the signal characteristic indicates that the UE is within the region comprises:

estimating, by the UE, a time period that the UE is within the region based on at least the signal characteristic； and

determining, by the UE, whether the time period achieves a time threshold.
The method of claim 7, further comprising:

estimating, by the UE, a speed of movement of the UE within the serving cell； and

calculating, by the UE and based on the speed, at least the time threshold.
The method of claim 1, wherein at least the signal characteristic is at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
An apparatus for wireless communication, comprising:

means for determining at least a signal characteristic of one or more signals received from a serving cell；

means for determining whether at least the signal characteristic indicates that the apparatus is within a region of a location underneath an antenna of a base station providing the serving cell； and

means for delaying a handover of the apparatus from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the apparatus is within the region.
The apparatus of claim 10, wherein the means for delaying the handover comprises:

means for determining at least one triggering condition for sending a measurement report to facilitate to handover； and

means for modifying one or more parameters related to the at least one triggering condition.
The apparatus of claim 11, wherein the means for modifying the one or more parameters comprises means for increasing at least one detection threshold for at least the signal characteristic that causes the at least one triggering condition.
The apparatus of claim 12, wherein the at least one detection threshold for at least the signal characteristic comprises at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
The apparatus of claim 11, wherein the mean for modifying the one or more parameters comprises means for increasing a time-to-trigger (TTT) sending of the measurement report by multiplying a time-to-trigger coefficient.
The apparatus of claim 11, wherein the means for modifying the one or more parameters is based on determining whether the target cell is in a list having one or more restricted handover conditions.
The apparatus of claim 10, wherein the means for determining whether at least the signal characteristic indicates that the apparatus is within the region comprises:

means for estimating a time period that the apparatus is within the region based on at least the signal characteristic； and

means for determining whether the time period achieves a time threshold.
The apparatus of claim 10, further comprising:

means for estimating a speed of movement of the apparatus within the serving cell； and

means for calculating at least the time threshold based on the speed.
The apparatus of claim 10, wherein at least the signal characteristic is at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
An apparatus for wireless communication, comprising:

a memory configured to store instructions； and

at least one processor coupled to the memory, the at least one processor and the memory are configured to execute the instructions to:

determine at least a signal characteristic of one or more signals received from a serving cell；

determine whether at least the signal characteristic indicates that the apparatus is within a region of a location underneath an antenna of a base station providing the serving cell； and

delay a handover of the apparatus from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the apparatus is within the region.
The apparatus of claim 19, wherein the at least one processor and the memory are further configured to execute the instructions to:

determine at least one triggering condition for sending a measurement report to facilitate to handover； and

modify one or more parameters related to the at least one triggering condition.
The apparatus of claim 20, wherein the at least one processor and the memory are further configured to execute the instructions to increase at least one detection threshold for at least the signal characteristic that causes the at least one triggering condition.
The apparatus of claim 21, wherein the at least one detection threshold for at least the signal characteristic comprises at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
The apparatus of claim 20, wherein the at least one processor and the memory are further configured to execute the instructions to increase a time-to-trigger (TTT) sending of the measurement report by multiplying a time-to-trigger coefficient.
The apparatus of claim 20, wherein the at least one processor and the memory are further configured to execute the instructions to modify the one or more parameters based on determining whether the target cell is in a list having one or more restricted handover conditions.
The apparatus of claim 19, wherein the at least one processor and the memory are further configured to execute the instructions to:

estimate a time period that the apparatus is within the region based on at least the signal characteristic； and

determine whether the time period achieves a time threshold.
The apparatus of claim 19, wherein the at least one processor and the memory are further configured to execute the instructions to:

estimate a speed of movement of the apparatus within the serving cell； and

calculate at least the time threshold based on the speed.
The apparatus of claim 19, wherein at least the signal characteristic is at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
A computer-readable medium storing computer executable code, comprising code to:

determine at least a signal characteristic of one or more signals received from a serving cell；

determine whether at least the signal characteristic indicates that a user equipment (UE) is within a region of a location underneath an antenna of a base station providing the serving cell； and

delay a handover of the UE from the serving cell to a target cell based on determining that at least the signal characteristic indicates that the UE is within the region.
The computer-readable medium of claim 28, further comprising code to:

determine at least one triggering condition for sending a measurement report to facilitate to handover； and

modify one or more parameters related to the at least one triggering condition.
The computer-readable medium of claim 29, further comprising code to increase at least one detection threshold for at least the signal characteristic that causes the at least one triggering condition.
The computer-readable medium of claim 30, wherein the at least one detection threshold for at least the signal characteristic comprises at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.
The computer-readable medium of claim 29, further comprising code to increase a time-to-trigger (TTT) sending of the measurement report by multiplying a time-to-trigger coefficient.
The computer-readable medium of claim 29, further comprising code to modify the one or more parameters based on determining whether the target cell is in a list having one or more restricted handover conditions.
The computer-readable medium of claim 28, further comprising code to:

estimate a time period that the UE is within the region based on at least the signal characteristic； and

determine whether the time period achieves a time threshold.
The computer-readable medium of claim 28, further comprising code to:

estimate a speed of movement of the UE within the serving cell； and

calculate at least the time threshold based on the speed.
The computer-readable medium of claim 28, wherein at least the signal characteristic is at least one of a frequency error, a frequency offset, a timing offset, a power level offset, a reference signal received power (RSRP) drop rate, a RSRP absolute level, a relative RSRP drop amount, a received signal strength indicator (RSSI) , a RSSI absolute level, a reference signal received quality (RSRQ) , a RSRQ absolute level, a signal-to-noise ratio (SNR) , a signal to interference plus noise ratio (SINR) , or a real-time transport protocol (RTP) package loss rate.