WO2013040743A1 - Method and apparatus for performing handover in communication system - Google Patents

Method and apparatus for performing handover in communication system Download PDF

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Publication number
WO2013040743A1
WO2013040743A1 PCT/CN2011/079828 CN2011079828W WO2013040743A1 WO 2013040743 A1 WO2013040743 A1 WO 2013040743A1 CN 2011079828 W CN2011079828 W CN 2011079828W WO 2013040743 A1 WO2013040743 A1 WO 2013040743A1
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Prior art keywords
base station
measurement report
handover
target base
transmitting power
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PCT/CN2011/079828
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French (fr)
Inventor
Lei Jiang
Ming Lei
Weidong Wang
Yinghai ZHANG
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Nec (China) Co., Ltd.
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Priority to PCT/CN2011/079828 priority Critical patent/WO2013040743A1/en
Publication of WO2013040743A1 publication Critical patent/WO2013040743A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/04—Reselecting a cell layer in multi-layered cells
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/34—Reselection control
    • H04W36/36—Reselection control by user or terminal equipment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

Embodiments of the disclosure provide a method and apparatus for performing handover in a communication system. The communication system at least comprises a source base station, a target base station and a user equipment (UE), the source base station manages a macrocell, the target base station manages a femtocell, and the UE is served by the source base station. The method may comprise steps of: responsive to requesting to handover the UE from the macrocell to the femtocell, receiving a measurement report from the source base station; and determining whether to perform the handover based on the measurement report.

Description

METHOD AND APPARATUS FOR PERFORMING
HANDOVER IN COMMUNICATION SYSTEM
FIELD OF THE INVENTION
[0001] Embodiments of the present invention generally relate to communication techniques. More particularly, embodiments of the present invention relate to a method and apparatus for performing handover in a communication system.
BACKGROUND OF THE INVENTION
[0002] 3 GPP LTE and LTE-Advanced, also known as the evolution standard of the great success of GSM/HSPA technology, is aiming at creating a new series of specifications for the new evolving radio-access technology. Though LTE and/or LTE-Advanced is promised to provide high speed data services, the problem of indoor coverage still have not a good solution. Femtocell is proposed to solve the problem. A femtocell, usually referred to as a small cell, is a low power and flexible deployed access point for satisfying the requirements of high data rate and signal quality (QoS), especially for an indoor user equipment (UE).
[0003] Active research has been developed on the femtocell, especially on handover procedures from a macrocell to a femtocell. During a handover, a base station (BS) managing the macrocell may be referred to as a source base station and a base station managing the femtocell may be referred to as a target base station. In a conventional case that a source base station is installed outdoors and a target base station is installed indoors, a UE may be served by the source base station outdoors and handovered from the macrocell to the femtocell when the UE moves from outdoors to indoors. The handover from the macrocell to the femtocell is also referred to as a femtocell inbound handover.
[0004] In a heterogeneous network comprising a femtocell and a macrocell, interference problem is quite complex, which has undesirable impact on handover between the femtocell and the macrocell. According to existing technology, the handover conventionally depends on the downlink signal quality, specifically, when the downlink signal quality is good enough, the handover will be performed. The downlink signal quality usually refers to a signal quality of downlink from the macrocell to the UE and/or a signal quality of downlink from the femtocell to the UE.
[0005] However, for a femtocell inbound handover, that is, handover from a macrocell to a femtocell, conventional solutions only considering downlink signal quality are not enough for at least following reasons. First, the conventional solutions omit uplink signals quality, that is, a signal quality of uplink from the UE to the target base station, so serious interference may increases failure rate of the handover. Next, it is difficult for the conventional solutions to identify an uplink transmitting signal of UE from interference signals, which has negative effect on signal detection and service quality after the handover.
[0006] In view of the foregoing problems, there is a need to consider the uplink signal quality during a femtocell inbound handover, so as to improve the effectiveness and anti-interference performance of handover.
SUMMARY OF THE INVENTION
[0007] The present invention proposes a solution which considers uplink signal quality during a femtocell inbound handover. Specifically, the present invention provides a method and apparatus for performing handover in a communication system, during which the signal quality of uplink from the UE to the target base station has been taken into account.
[0008] According to a first aspect of the present invention, embodiments of the invention provide a method for performing handover in a communication system, wherein the communication system at least comprises a source base station, a target base station and a user equipment (UE), the source base station manages a macrocell, the target base station manages a femtocell, and the UE is served by the source base station. The method may comprise steps of: responsive to requesting to handover the UE from the macrocell to the femtocell, receiving a measurement report from the source base station; and determining whether to perform the handover based on the measurement report.
[0009] According to a second aspect of the present invention, embodiments of the invention provide a method for performing handover in a communication system, wherein the communication system at least comprises a source base station, a target base station and a user equipment (UE), the source base station manages a macrocell, the target base station manages a femtocell, and the UE is served by the source base station. The method may comprise steps of: requesting the target base station to handover the UE from the macrocell to the femtocell; and transmitting a measurement report to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
[0010] According to a third aspect of the present invention, embodiments of the invention provide an apparatus for performing handover in a communication system, wherein the communication system at least comprises a source base station, a target base station and a user equipment (UE), the source base station manages a macrocell, the target base station manages a femtocell, and the UE is served by the source base station. The apparatus may comprise: receiving unit configured to, responsive to requesting to handover the UE from the macrocell to the femtocell, receive a measurement report from the source base station; and determining unit configured to determine whether to perform the handover based on the measurement report.
[0011] According to a fourth aspect of the present invention, embodiments of the invention provide an apparatus for performing handover in a communication system, wherein the communication system at least comprises a source base station, a target base station and a user equipment (UE), the source base station manages a macrocell, the target base station manages a femtocell, and the UE is served by the source base station. The apparatus may comprise: requesting unit configured to request the target base station to handover the UE from the macrocell to the femtocell; and transmitting unit configured to transmit a measurement report to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
[0012] The following benefits can be expected with the invention. By means of taking the uplink signal quality into account, the present invention has effectively improved the effectiveness and anti-interference performance of handover. Additionally, the present invention is based on 3 GPP LTE/LTE- Advanced standard and makes little change to the existing flow of handover procedures, so the present invention has the advantage of good compatibility.
[0013] Other features and advantages of the embodiments of the present invention will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Embodiments of the invention are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where
[0015] FIG. 1 illustrates a schematic diagram of a communication system applicable to embodiments of the present invention;
[0016] FIG. 2 illustrates schematic diagram of procedures for performing handover according to the prior art;
[0017] FIG. 3 illustrates a flow chart of a method for performing handover in a communication system according to an embodiment of the invention;
[0018] FIG. 4 illustrates a flow chart of a method for performing handover in a communication system according to another embodiment of the invention;
[0019] FIG. 5 illustrates a flow chart of a method for performing handover in a communication system according to a further embodiment of the invention;
[0020] FIG. 6 illustrates a block diagram of an apparatus for performing handover in a communication system according to an embodiment of the invention;
[0021] FIG. 7 illustrates a block diagram of an apparatus for performing handover in a communication system according to a further embodiment of the invention; and
[0022] FIG. 8 illustrates schematic diagram of procedures for performing handover according to an embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0023] Various embodiments of the present invention are described in detail with reference to the drawings. The flowcharts and block diagrams in the figures illustrate the apparatus, method, as well as architecture, functions and operations executable by a computer program product according to the embodiments of the present invention. In this regard, each block in the flowcharts or block may represent a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions. It should be noted that in some alternatives, functions indicated in blocks may occur in an order differing from the order as illustrated in the figures. For example, two blocks illustrated consecutively may be actually performed in parallel substantially or in an inverse order, which depends on related functions. It should also be noted that block diagrams and/or each block in the flowcharts and a combination of thereof may be implemented by a dedicated hardware-based system for performing specified functions/operations or by a combination of dedicated hardware and computer instructions.
[0024] In the disclosure, a user equipment (UE) may refer to a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), Mobile Station (MS), or an Access Terminal (AT), and some or all of the functions of the UE, the terminal, the MT, the SS, the PSS, the MS, or the AT may be included.
[0025] In the disclosure, a base station (BS) may refer to an Access Point (AP), a Radio Access Station (RAS), a node B (NodeB), an evolved NodeB (eNodeB), a Base Transceiver Station (BTS), or a Mobile Multihop Relay (MMR)-BS, and some or all of the functions of the BS, the AP, the RAS, the NodeB, the eNodeB, the BTS, or the MMR-BS may be included.
[0026] FIG. 1 illustrates a schematic diagram of a communication system applicable to embodiments of the present invention.
[0027] The communication environment of FIG. 1 illustrates a LTE system.
The system illustratively comprises a source base station (source BS) 110, a target base station (target BS) 120 and a user equipment (UE) 130. The source BS 110 manages a macrocell, and the target base station manages a femtocell. The UE 130 is served by the source BS 110.
[0028] According to embodiments of the present invention, the source base station may be a macro base station or any other applicable network node. The target base station may be a femto base station (sometimes called as home eNodeB, HeNB, etc.) which has small size, low-power, works in the licensed frequency bands, and connects to broadband Internet backhaul, or any other applicable network node.
[0029] Referring to FIG. 1, the source base station 110 and the target base station 120 coexist in a communication system. When the UE 130 seeks to connect to a femto base station located close to the macro base station or a femto base station located in a position where a high intensity signal is received from the macro base station, a handover from the macrocell to the femtocell (also called as femtocell inbound handover hereafter) will occur.
[0030] For better understanding, the following embodiments of the present disclosure are described under the LTE system, for example, in the communication environment of FIG.1. As can be appreciated by those skilled in the art, the present disclosure can be applicable to any other suitable communication environment, but not limited to the specific arrangement shown in FIG.1.
[0031] FIG. 2 illustrates schematic diagram of procedures for performing handover according to the prior art.
[0032] In a communication system, such as that shown in FIG .1 , according to existing specifications, the target BS detects an uplink signals transmitted from one or more UEs and sends a report including information about the uplink signals to the source base station. The source base station identifies the UE that has entered a coverage area of the target base station based on the report. Then the femtocell inbound handover may be performed according to the prior art as shown in FIG .2.
[0033] Referring to FIG. 2, at operations 211 and 212, UE measures downlink signals of both the source BS and the target BS. Then, at operation 213, the UE transmits a measurement report to the source BS. Based on the measurement report, the source BS sends a handover request to the target BS at operation 214. In response to the handover request, the target BS sends a handover response to the source BS at operation 215. Upon receiving the handover response, the source BS notifies the UE to perform the handover at operation 216.
[0034] In view of the above, those skilled in the art will appreciate that the handover procedures in the existing solution does not take the uplink signal quality into account.
[0035] FIG. 3 illustrates a flow chart of a method 300 for performing handover in a communication system according to an embodiment of the invention. In this embodiment, the communication system at least comprises a source base station, a target base station and a UE. The source base station manages a macrocell, the target base station manages a femtocell, and the UE is being served by the source base station.
[0036] According to embodiments of the present invention, the method of FIG. 3 may be performed at a target base station, for example, performed by an apparatus of the target base station, by a processor of the target base station, or by the target base station itself. As mentioned above, the target base station may be a femto base station a home base station, HeNB, and so on.
[0037] At step S301, responsive to requesting to handover the UE from the macrocell to the femtocell, a measurement report is received from the source base station.
[0038] According to embodiments of the present invention, the measurement report may be generated at the UE and transmitted from the UE to the source base station. The measurement report may be sent from the source base station to the at the target base station, together with or after a request to handover the UE from the macrocell to the femtocell.
[0039] According to embodiments of the present invention, the measurement report may comprise a UE transmitting power and/or a reference signal receiving power (RSRP) of the target base station. As appreciated by those skilled in the art, the measurement report may comprises some other information for assisting the communication procedures known in the art, and the illustrated embodiments are only for example, but not for limitation.
[0040] At step S302, whether to perform the handover is determined based on the measurement report.
[0041] According to embodiments of the present invention, whether to perform the handover may be determined by estimating an uplink signal quality based on the received measurement report and determining whether to perform the handover based on the estimated uplink signal quality, wherein the uplink signal quality is a signal quality of the uplink from the UE to the target base station.
[0042] According to embodiments of the present invention, the uplink signal quality may be estimated based on the received measurement report in several ways according to the present invention. In an embodiment, the uplink signal quality may be estimated by: measuring receiving interference power (RIP) of the target base station; estimating the uplink receiving power when the UE is handover to the femtocell according to the received measurement report; and obtaining the uplink signal quality based on the RIP and the uplink receiving power. According to embodiments of the present invention, there may be many ways to estimating the uplink receiving power according to the received measurement report, and the details will be described with respect to FIG. 4.
[0043] According to embodiments of the present invention, whether to perform the handover may be determined based on the estimated uplink signal quality in several ways according to the present invention. In an embodiment, whether to perform the handover may be determined by: comparing the estimated signal quality with a threshold; and determining whether to perform the handover according to the comparing result.
[0044] According to embodiments of the present invention, the method for performing handover in a communication system, e.g., the method illustrated in FIG. 3, may optionally comprise a step of sending to the source base station a handover response indicating whether to perform the handover. When the source base station receives the handover response, it may identify whether to perform the handover and take corresponding actions.
[0045] FIG. 4 illustrates a flow chart of a method 400 for performing handover in a communication system according to another embodiment of the invention. In this embodiment, the communication system at least comprises a source base station, a target base station and a UE. The source base station manages a macrocell, the target base station manages a femtocell, and the UE is being served by the source base station.
[0046] According to embodiments of the present invention, the method of FIG. 4 may be performed at a target base station, for example, performed by an apparatus of the target base station, by a processor of the target base station, or by the target base station itself. As mentioned above, the target base station may be a femto base station a home base station, HeNB, and so on.
[0047] At step S401, responsive to requesting to handover the UE from the macrocell to the femtocell, a measurement report is received from the source base station.
[0048] The step S401 is similar to the step S301, so all the details described at the step S301 are also applicable to the step S401.
[0049] At step S402, RIP of the target base station is measured.
[0050] RIP of the target base station is the measuring receiving interference power which may be measured at the target base station. According to existing technical solutions, the RIP of the target base station may be measured in several known ways and details are omitted here.
[0051] At step S403, an uplink receiving power when the UE is handover to the femtocell is estimated based on the received measurement report.
[0052] According to embodiments of the present invention, the uplink receiving power may be estimated by determining an upper transmitting power of UE according to the received measurement report; obtaining a pathloss between the source base station and the target base station according to the received measurement report; and estimating the uplink receiving power based on the obtained transmitting power and the calculated pathloss.
[0053] In embodiments of the present invention, the uplink is from the UE to the target base station. For purpose of description, the uplink receiving power is the uplink power received at the target base station, exemplarily denoted as P"L ; the pathloss between the source base station and the target base station is exemplarily denoted as RpatMoss ; the reference signal receiving power (RSRP) of the target base station is exemplarily denoted as P^ ; the target base station transmitting power is the transmitting power of the target base station, exemplarily denoted as Pt femt0 ;the transmitting power of UE is the uplink transmitting power transmitted at the UE, exemplarily denoted as P" ; and the upper transmitting power of UE is the upper limit of the uplink transmitting power, exemplarily denoted as P"L upper■
[0054] According to an embodiment of the present invention, the measurement report comprises a UE transmitting power. The upper transmitting power of UE may be determined by retrieving the UE transmitting power from the measurement report; assigning a weight to the retrieved UE transmitting power based on power capping; weighting the retrieved UE transmitting power with the assigned weight; and determining the weighted UE transmitting power as the upper transmitting power of UE.
[0055] In this embodiment, the UE transmitting power FfL is included in the measurement report, which may be sent from the UE to the source base station and then transferred the source base station to the target base station. Conventionally, when a UE accesses a femtocell, the transmitting power of the UE will be limited so that the uplink of the source base station will not be seriously interfered, which is usually called as "power capping". Taking the power capping into account, a weight may be assigned to the transmitting power of UE to limit the upper value of the transmitting power of UE. Traditionally, the weight is a value between 0 and 1. The UE transmitting power F 1 may be weighted by a coefficient W according to the following equation (1) to obtain the upper transmitting power of UE Pt UL upper .
Pt U!upper = W x Pt UL, 0 < W < \ (1)
[0056] According to another embodiment of the present invention, the measurement report at least comprises a UE transmitting power. The upper transmitting power of UE may be determined by retrieving the UE transmitting power from the measurement report; and determining the retrieved UE transmitting power as the upper transmitting power of UE.
[0057] In this embodiment, the UE transmitting power FfL is included in the measurement report and the issue of "power capping" is considered as having little influence on the handover. In this regard, the retrieved UE transmitting power Pt UL may be directly regarded as the upper transmitting power P"L upper .
[0058] According to embodiments of the present invention, the measurement report comprises a reference signal receiving power ( SRP) of the target base station. The pathloss between the source base station and the target base station may be obtained by retrieving the RSRP of the target base station from the measurement report; obtaining the target base station transmitting power; and calculating the pathloss based on the obtained RSRP of the target base station and the target base station transmitting power.
[0059] In these embodiments, the RSRP of the target base station, that is,
, is included in the measurement report, which may be obtained at the UE and sent from the UE to the source base station and then transferred the source base station to the target base station. For the target base station, the target base station transmitting power Pt femt0 may be obtained by various means which are known in the art, so the details are omitted herein. Based on the obtained RSRP of the target base station P sw and target base station transmitting power Pt femto ? the pathloss between the source base station and the target base station may be calculated according to the following equation (2).
femto
R pathloss = p femto (2
"RSRP
[0060] According to embodiments of the present invention, based on the obtained transmitting power and the calculated pathloss, the uplink receiving power may be calculated according to the following equation (3).
Figure imgf000013_0001
[0061] It is to be noted that the illustrative equations are only examples but not for limitation, those skilled in the art may employ other suitable means to perform the respective operations.
[0062] At step S404, the uplink signal quality is obtained based on the RIP and the uplink receiving power.
[0063] According to embodiments of the present invention, the uplink signal quality may refer to a signal quality of the uplink from the UE to the target base station. In the present invention, the signal quality may be one of the group of SINR (Signal to Interference plus Noise Ratio), SNR (Signal to Noise Ratio), SIR (Signal to Interference Ratio) CINR (Carrier to Interference plus Noise Ratio), CNR (Carrier to Noise Ratio), and so on. In this embodiment, SINR is taken as an example to represent the signal quality. It is to be noted that, in other embodiments of the present invention, the channel quality may be SNR, SIR, CINR, CNR or any combination of SINR, SNR, SIR, CINR, and CNR.
[0064] In an embodiment, for purpose of description, the uplink signal quality when the UE is handovered to the femtocell may be represented as SINR and denoted as SINR Jink , which may be calculated according to the following equation (4).
Figure imgf000013_0002
[0065] In another embodiment, the uplink signal quality when the UE is handovered to the femtocell may be represented as SIR and denoted as SIRuplink , which may be calculated according to the following equation (5).
Figure imgf000014_0001
[0066] It is to be noted that the illustrative equations for calculating the uplink signal quality are only examples but not for limitation, those skilled in the art may employ other suitable means to obtain the uplink signal quality based on the RIP and the uplink receiving power.
[0067] At step S405, the signal quality is compared with a threshold.
[0068] There are several ways of determining the threshold. For example, the threshold may be preset by operators according to their preferences or experiences. Alternatively, the threshold may be determined by a noise level. As appreciated by those skilled in the art, noise levels may be different for various application scenarios, and there are existing methods for determining the threshold by a noise level.
[0069] At step S406, whether to perform the handover is determined according to the comparing result.
[0070] According to embodiments of the present invention, if the signal quality exceeds a threshold, it may be indicated that the uplink quality is good enough for communication between the UE and the target base station, so the handover may be determined to be performed; otherwise, it may be indicated that the uplink quality is not so good for communication between the UE and the target base station, so the handover may be determined not to be performed.
[0071] At step S407, a handover response indicating whether to perform the handover is sent to the source base station.
[0072] FIG. 5 illustrates a flow chart of a method 500 for performing handover in a communication system according to a further embodiment of the invention. In this embodiment, the communication system at least comprises a source base station, a target base station and a UE. The source base station manages a macrocell, the target base station manages a femtocell, and the UE is being served by the source base station.
[0073] According to embodiments of the present invention, the method of FIG. 5 may be performed at a source base station, for example, performed by an apparatus of the source base station, by a processor of the source base station, or by the source base station itself. As mentioned above, the source base station may be a macro base station or any other applicable network node.
[0074] At step S501, the target base station is requested to handover the UE from the macrocell to the femtocell.
[0075] According to embodiments of the present invention, step S501 may be performed at the source base station by several ways. For example, the source base station may send to the target a request for handover.
[0076] At step S502, a measurement report is transmitted to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
[0077] According to embodiments of the present invention, the measurement report may be generated at the UE and transmitted from the UE to the source base station.
[0078] According to embodiments of the present invention, the measurement report may comprise a UE transmitting power and/or a reference signal receiving power ( S P) of the target base station.
[0079] According to embodiments of the present invention, the method for performing handover in a communication system, e.g., the method illustrated in FIG. 5, may optionally comprise a step of receiving a handover response indicating whether to perform the handover from the target base station.
[0080] According to embodiments of the present invention, the handover response may be made according to the method, such as the method 300 or 400, for performing handover in a communication system according to the present invention. For example, whether to perform the handover may be determined according to the method 300 or 400 as illustrated in the embodiment of FIG. 3 or FIG. 4, which is based on a measurement report, e.g., the measurement report sent to the target base station at step S502. Upon determining whether to perform the handover, a handover response may be sent from the target base station to the source base station, so as to trigger the UE to perform the handover.
[0081] FIG. 6 illustrates a block diagram of an apparatus 600 for performing handover in a communication system according to an embodiment of the invention. In this embodiment, the communication system at least comprises a source base station, a target base station and a UE. The source base station manages a macrocell, the target base station manages a femtocell, and the UE is being served by the source base station.
[0082] According to embodiments of the present invention, the apparatus 600 may be an apparatus of the target base station, a processor of the target base station, or the target base station. As mentioned above, the target base station may be a femto base station a home base station, HeNB, and so on.
[0083] Referring to FIG. 6, the apparatus 600 may comprises two components: receiving unit 610 and determining unit 620.
[0084] According to embodiments of the present invention, the receiving unit 610 may be configured to, responsive to requesting to handover the UE from the macrocell to the femtocell, receive a measurement report from the source base station; and the determining unit 620 may be configured to determine whether to perform the handover based on the measurement report.
[0085] According to embodiments of the present invention, the measurement report is generated at the UE and transmitted from the UE to the source base station.
[0086] According to embodiments of the present invention, the determining unit 620 may comprise: estimating means configured to estimate an uplink signal quality based on the received measurement report, wherein the uplink signal quality is a signal quality of the uplink from the UE to the target base station; and determining means configured to determine whether to perform the handover based on the estimated uplink signal quality.
[0087] According to embodiments of the present invention, the estimating means of the determining unit 620 may comprise: means configured to measure receiving interference power (RIP) of the target base station; means configured to estimate the uplink receiving power when the UE is handover to the femtocell based on the received measurement report; and means configured to obtain the uplink signal quality based on the RIP and the uplink receiving power.
[0088] According to embodiments of the present invention, the means configured to estimate the uplink receiving power when the UE is handover to the femtocell based on the received measurement report may comprise: means configured to determine an upper transmitting power of UE according to the received measurement report; means configured to obtain a pathloss between the source base station and the target base station according to the received measurement report; and means configured to estimate the uplink receiving power based on the obtained transmitting power and the calculated pathloss.
[0089] According to embodiments of the present invention, the measurement report may comprise a UE transmitting power and the means configured to determine an upper transmitting power of UE according to the received measurement report may comprise: means configured to retrieve the UE transmitting power from the measurement report; and means configured to determine the retrieved UE transmitting power as the upper transmitting power of UE.
[0090] According to embodiments of the present invention, the measurement report may comprise a UE transmitting power and the means configured to determine an upper transmitting power of UE according to the received measurement report may comprise: means configured to retrieve the UE transmitting power from the measurement report; means configured to assign a weight to the retrieved UE transmitting power based on power capping; means configured to weight the retrieved UE transmitting power with the assigned weight; and means configured to determine the weighted UE transmitting power as the upper transmitting power of UE.
[0091] According to embodiments of the present invention, the measurement report may comprise a reference signal receiving power ( S P) of the target base station and the means configured to obtain a pathloss between the source base station and the target base station according to the received measurement report may comprise: means configured to retrieve the RSRP of the target base station from the measurement report; means configured to obtain the target base station transmitting power; and means configured to calculate the pathloss based on the obtained RSRP of the target base station and the target base station transmitting power.
[0092] According to embodiments of the present invention, the determining means of the determining unit 620 may comprise: means configured to compare the estimated signal quality with a threshold; and means configured to determine whether to perform the handover according to the comparing result.
[0093] According to embodiments of the present invention, the apparatus 600 may further comprise: sending unit configured to send to the source base station a handover response indicating whether to perform the handover.
[0094] It is noted that the apparatus 600 may be configured to implement functionalities as described with reference to FIGs. 3 and 4. Therefore, the features discussed with respect to methods 300 and 400 apply to the corresponding components of the apparatus 600. It is further noted that the components of the apparatus 600 may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus 600 may be respectively implemented by a circuit, a processor or any other appropriate selection device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation.
[0095] In some embodiment of the present disclosure, the apparatus 600 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 600 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 600 to at least perform according to methods 300 or 400 as discussed above.
[0096] FIG. 7 illustrates a block diagram of an apparatus 700 for performing handover in a communication system according to a further embodiment of the invention. In this embodiment, the communication system at least comprises a source base station, a target base station and a UE. The source base station manages a macrocell, the target base station manages a femtocell, and the UE is being served by the source base station.
[0097] According to embodiments of the present invention, the apparatus 700 may be an apparatus of the source base station, a processor of the source base station, or the source base station. As mentioned above, the source base station may be a macro base station or any other applicable network node.
[0098] Referring to FIG. 7, the apparatus 700 may comprises two components: requesting unit 710 and transmitting unit 720.
[0099] According to embodiments of the present invention, the requesting unit 710 may be configured to request the target base station to handover the UE from the macrocell to the femtocell; and the transmitting unit 720 may be configured to transmit a measurement report to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
[00100] According to embodiments of the present invention, the apparatus 700 may further comprise: receiving unit configured to receive a handover response indicating whether to perform the handover from the target base station.
[00101] According to embodiments of the present invention, the measurement report may be generated at the UE and transmitted from the UE to the source base station.
[00102] According to embodiments of the present invention, the measurement report may comprise a UE transmitting power and/or a reference signal receiving power ( S P) of the target base station.
[00103] It is noted that the apparatus 700 may be configured to implement functionalities as described with reference to FIG. 5. Therefore, the features discussed with respect to method 500 apply to the corresponding components of the apparatus 700. It is further noted that the components of the apparatus 700 may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus 700 may be respectively implemented by a circuit, a processor or any other appropriate selection device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation.
[00104] In some embodiment of the present disclosure, the apparatus 700 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 700 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 700 to at least perform according to method 500 as discussed above.
[00105] FIG. 8 illustrates schematic diagram of procedures for performing handover according to an embodiment of the invention.
[00106] Taken the communication system shown in FIG .1 as an example, the target BS detects an uplink signals transmitted from one or more UEs and sends a report including information about the uplink signals to the source base station. The source base station identifies the UE that has entered a coverage area of the target base station based on the report. Then the femtocell inbound handover may be performed according to an embodiment of the present invention shown in FIG. 8.
[00107] Referring to FIG. 8, at operations 811 and 812, UE measures downlink signals of both the source BS and the target BS. Then, at operation 813, the UE transmits a measurement report to the source BS. Based on the measurement report, the source BS sends a handover request to the target BS at operation 814. In addition, the source BS further transmits a measurement report to the target BS at operation 814. In response to the handover request, the target BS estimated uplink signal quality at operation 815 based on the received measurement report to determine whether to perform the handover. Then, the target BS sends a handover response indicating whether to perform the handover to the source BS at operation 816. Upon the handover response indicating to perform the handover, the source BS notifies the UE to perform the handover at operation 817.
[00108] In view of the above, those skilled in the art will appreciate that the handover procedures according to embodiments of the present invention take the uplink signal quality into account, so the present invention improves the effectiveness and anti-interference performance of handover.
[00109] Based on the above description, the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus, a method, or a computer program product. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
[00110] The various blocks shown in FIGS. 3-5 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure.
[00111] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
[00112] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.
[00113] Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.
[00114] Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:
1. A method for performing handover in a communication system, the communication system at least comprising a source base station, a target base station and a user equipment (UE), the source base station managing a macrocell, the target base station managing a femtocell, and the UE being served by the source base station, wherein the method comprises:
responsive to requesting to handover the UE from the macrocell to the femtocell, receiving a measurement report from the source base station; and
determining whether to perform the handover based on the measurement report.
2. The method of Claim 1, wherein the measurement report is generated at the UE and transmitted from the UE to the source base station.
3. The method of Claim 1, wherein determining whether to perform the handover based on the measurement report comprises:
estimating an uplink signal quality based on the received measurement report, wherein the uplink signal quality is a signal quality of the uplink from the UE to the target base station; and
determining whether to perform the handover based on the estimated uplink signal quality.
4. The method of Claim 3, wherein estimating an uplink signal quality based on the received measurement report comprises:
measuring receiving interference power (RIP) of the target base station;
estimating the uplink receiving power when the UE is handover to the femtocell based on the received measurement report; and
obtaining the uplink signal quality based on the RIP and the uplink receiving power.
5. The method of Claim 4, wherein estimating the uplink receiving power when the
UE is handover to the femtocell based on the received measurement report comprises: determining an upper transmitting power of UE according to the received measurement report;
obtaining a pathloss between the source base station and the target base station according to the received measurement report; and
estimating the uplink receiving power based on the obtained transmitting power and the calculated pathloss.
6. The method of Claim 5, wherein the measurement report comprises a UE transmitting power and wherein determining an upper transmitting power of UE according to the received measurement report comprises:
retrieving the UE transmitting power from the measurement report; and
determining the retrieved UE transmitting power as the upper transmitting power ofUE.
7. The method of Claim 5, wherein the measurement report comprises a UE transmitting power and wherein determining an upper transmitting power of UE according to the received measurement report comprises:
retrieving the UE transmitting power from the measurement report;
assigning a weight to the retrieved UE transmitting power based on power capping; weighting the retrieved UE transmitting power with the assigned weight; and determining the weighted UE transmitting power as the upper transmitting power ofUE.
8. The method of Claim 5, wherein the measurement report comprises a reference signal receiving power ( SRP) of the target base station and wherein obtaining a pathloss between the source base station and the target base station according to the received measurement report comprises:
retrieving the RSRP of the target base station from the measurement report;
obtaining the target base station transmitting power; and
calculating the pathloss based on the obtained RSRP of the target base station and the target base station transmitting power.
9. The method of Claim 3, wherein determining whether to perform the handover based on the estimated uplink signal quality comprises:
comparing the estimated signal quality with a threshold; and
determining whether to perform the handover according to the comparing result.
10. The method of Claim 1, further comprising:
sending to the source base station a handover response indicating whether to perform the handover.
11. A method for performing handover in a communication system, the communication system at least comprising a source base station, a target base station and a user equipment (UE), the source base station managing a macrocell, the target base station managing a femtocell, and the UE being served by the source base station, wherein the method comprises:
requesting the target base station to handover the UE from the macrocell to the femtocell; and
transmitting a measurement report to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
12. The method of Claim 11, further comprising:
receiving a handover response indicating whether to perform the handover from the target base station.
13. The method of Claim 11, wherein the measurement report is generated at the UE and transmitted from the UE to the source base station.
14. The method of Claim 11, wherein the measurement report comprises a UE transmitting power and/or a reference signal receiving power (RSRP) of the target base station.
15. An apparatus for performing handover in a communication system, the communication system at least comprising a source base station, a target base station and a user equipment (UE), the source base station managing a macrocell, the target base station managing a femtocell, and the UE being served by the source base station, wherein the apparatus comprises:
receiving unit configured to, responsive to requesting to handover the UE from the macrocell to the femtocell, receive a measurement report from the source base station; and
determining unit configured to determine whether to perform the handover based on the measurement report.
16. The apparatus of Claim 15, wherein the measurement report is generated at the UE and transmitted from the UE to the source base station.
17. The apparatus of Claim 15, wherein the determining unit comprises:
estimating means configured to estimate an uplink signal quality based on the received measurement report, wherein the uplink signal quality is a signal quality of the uplink from the UE to the target base station; and
determining means configured to determine whether to perform the handover based on the estimated uplink signal quality.
18. The apparatus of Claim 17, wherein the estimating means comprises:
means configured to measure receiving interference power (RIP) of the target base station;
means configured to estimate the uplink receiving power when the UE is handover to the femtocell based on the received measurement report; and
means configured to obtain the uplink signal quality based on the RIP and the uplink receiving power.
19. The apparatus of Claim 18, wherein the means configured to estimate the uplink receiving power when the UE is handover to the femtocell based on the received measurement report comprises:
means configured to determine an upper transmitting power of UE according to the received measurement report;
means configured to obtain a pathloss between the source base station and the target base station according to the received measurement report; and means configured to estimate the uplink receiving power based on the obtained transmitting power and the calculated pathloss.
20. The apparatus of Claim 19, wherein the measurement report comprises a UE transmitting power and wherein the means configured to determine an upper transmitting power of UE according to the received measurement report comprises: means configured to retrieve the UE transmitting power from the measurement report; and
means configured to determine the retrieved UE transmitting power as the upper transmitting power of UE.
21. The apparatus of Claim 19, wherein the measurement report comprises a UE transmitting power and wherein the means configured to determine an upper transmitting power of UE according to the received measurement report comprises: means configured to retrieve the UE transmitting power from the measurement report;
means configured to assign a weight to the retrieved UE transmitting power based on power capping;
means configured to weight the retrieved UE transmitting power with the assigned weight; and
means configured to determine the weighted UE transmitting power as the upper transmitting power of UE.
22. The apparatus of Claim 19, wherein the measurement report comprises a reference signal receiving power (RSRP) of the target base station and wherein the means configured to obtain a pathloss between the source base station and the target base station according to the received measurement report comprises:
means configured to retrieve the RSRP of the target base station from the measurement report;
means configured to obtain the target base station transmitting power; and means configured to calculate the pathloss based on the obtained RSRP of the target base station and the target base station transmitting power.
23. The apparatus of Claim 17, wherein the determining means comprises:
means configured to compare the estimated signal quality with a threshold; and means configured to determine whether to perform the handover according to the comparing result.
24. The apparatus of Claim 15, further comprising:
sending unit configured to send to the source base station a handover response indicating whether to perform the handover.
25. An apparatus for performing handover in a communication system, the communication system at least comprising a source base station, a target base station and a user equipment (UE), the source base station managing a macrocell, the target base station managing a femtocell, and the UE being served by the source base station, wherein the method comprises:
requesting unit configured to request the target base station to handover the UE from the macrocell to the femtocell; and
transmitting unit configured to transmit a measurement report to the target base station, so that the target base station determines whether to perform the handover based on the measurement report.
26. The apparatus of Claim 25, further comprising:
receiving unit configured to receive a handover response indicating whether to perform the handover from the target base station.
27. The apparatus of Claim 25, wherein the measurement report is generated at the UE and transmitted from the UE to the source base station.
28. The apparatus of Claim 25, wherein the measurement report comprises a UE transmitting power and/or a reference signal receiving power (RSRP) of the target base station.
PCT/CN2011/079828 2011-09-19 2011-09-19 Method and apparatus for performing handover in communication system WO2013040743A1 (en)

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