KR20100084213A - Method and system for estimating speed of user equipment in wireless communication system - Google Patents

Abstract

PURPOSE: A method and a device for estimating moving speed of a terminal in a wireless communication system are provided to accurately estimate moving speed of a terminal. CONSTITUTION: When a UE(User Equipment) moves to a cell controlled by another ENB(Evolved Node B) of a wireless communication system, a cell size information transmitting unit(501) transmits size information of cells to which the UE moves during a set period and a cell controlled by the ENB to another ENB. A terminal speed estimating unit(502) estimates moving speed of the UE using size information of the cell. A transmission power measuring unit(504) measures transmission power of a downlink signal transmitted to a cell coverage edge of the ENB.

Description

Method and apparatus for estimating terminal movement speed in wireless communication system

The present invention relates to a method and apparatus for estimating a terminal movement speed in a wireless communication system. More particularly, the present invention relates to a method and an apparatus for efficiently estimating a terminal movement speed when different cell coverages are controlled for each base station in a wireless communication system. .

UMTS (Universal Mobile Telecommunication Service) system is based on the European mobile communication system Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), and Wideband Code Division Multiple Access, Third generation asynchronous mobile communication system using WCDMA).

The 3rd Generation Partnership Project (3GPP), which is in charge of UMTS standardization, is discussing Long Term Evolution (LTE) as the next generation mobile communication system of the UMTS system. LTE is a technology that implements high-speed packet-based communication with a transmission speed of up to 300 Mbps, and aims to commercialize it in 2010. To this end, various schemes are discussed. For example, a scheme of reducing the number of nodes located on a communication path by simplifying a network structure, or approaching wireless protocols as close as possible to a wireless channel are under discussion.

Meanwhile, in the LTE Release 8 standard, the number of handovers during a specific time is used as a main factor of a method of estimating a moving speed of a user equipment (UE), and the moving speed of the terminal is selected from among high, medium, and low. Assume one. The method using the number of handovers during a specific time period is suitable for a wireless communication system in which the size of a cell controlled by one base station is constant. There is a problem that the error is likely to occur in the speed estimation. In addition, there is a problem that an error is likely to occur when setting the event start timing during the handover control of the terminal.

In the wireless communication system of the present invention, a method for estimating a terminal movement speed and an apparatus therefor aim to accurately estimate the movement speed of a terminal by sharing size information of a cell controlled by each base station between base stations of the wireless communication system. In addition, the method and apparatus for estimating the movement speed of a terminal in a wireless communication system according to the present invention aim to accurately set an event start timing during handover control of a terminal.

In the wireless communication system of the present invention for solving the above problems, the method of estimating the movement speed of a terminal has moved the terminal for a predetermined time when the terminal moves from a cell controlled by a first base station to a cell controlled by a second base station. Transmitting cell and cell size information controlled by the first base station from the first base station to the second base station, estimating a moving speed of the terminal using the size information of the cell at the second base station; And transmitting the estimated moving speed information of the terminal from the second base station to the terminal to match the moving speed information of the terminal. In addition, the size information of the cell is characterized in that the type information of the cells.

In addition, in the wireless communication system of the present invention for solving the above problems, the terminal movement speed estimation apparatus when the terminal moves to a cell controlled by another base station of the wireless communication system, the terminal has moved with the cells that have been moved for a set time; And a cell size information transmitter for transmitting the size information of the cell controlled by the base station to the other base station, and a terminal movement speed estimator for estimating the movement speed of the terminal using the size information of the cell. In addition, the size information of the cell is characterized in that the type information of the cells. The terminal movement speed estimator may transmit the estimated movement speed of the terminal to the terminal to match the movement speed information with the terminal.

According to a method and an apparatus for estimating the movement speed of a terminal in a wireless communication system of the present invention, it is possible to accurately estimate the movement speed of a terminal by sharing the size information of a cell controlled by each base station between base stations of the wireless communication system, and reflecting this. By reducing the unnecessary handover attempt as the movement speed of the terminal is measured faster than the actual movement speed, the connection release caused by delayed initiation of the handover event as the movement speed of the terminal is measured slower than the actual movement speed. Can be prevented.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined.

In addition, the terms of the embodiment of the present invention will be in accordance with the 3GPP LTE system standard.

1 is a view showing a schematic structure of a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, in a wireless communication system according to an exemplary embodiment of the present invention, an Evolved Radio Access Network (E-RAN) 110 and 112 may be an Evolved Node B (ENB) 120. , 122, 124, 126, and 128 and an Evolved Packet Core (EPC) 130, 132.

The UE (User Equipment) 101 connects to the Internet Protocol (IP) network 114 by the E-RANs 110 and 112. The ENBs 120, 122, 124, 126, and 128 are nodes corresponding to the existing Node Bs and are connected to the user UE 101 by a radio channel. In order to realize a transmission rate of up to 300 Mbps, a wireless communication system uses orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) in a 20 MHz bandwidth as a wireless access technology. In addition, an adaptive modulation & coding (AMC) scheme that determines a modulation scheme and a channel coding rate according to the channel state is applied.

Hereinafter, the E-RAN 110, 112 including the ENBs 120, 122, 124, 126, and 128 and the EPCs 130, 132 will be referred to as a base station.

In particular, in the present invention, the terminal moves between cells controlled by a plurality of base stations, and the base station estimates the moving speed of the terminal. In addition, the movement speed of the terminal estimated by the base station is transmitted back to the terminal, thereby obtaining synchronization with respect to the movement speed between the base station and the terminal and using this to control the handover event of the terminal.

In the prior art, the terminal used the number of handovers occurring during a certain period as a main factor to estimate its moving speed. In this case, as described above, in a system in which the size of the cell controlled by the base station is constant, the moving speed of the terminal can be estimated without a large error, and thus a large problem does not occur even when the moving speed of the terminal is estimated in the prior art. However, especially in the LTE system, the size of the cell varies, such as a macro cell, a femto cell, and a pico cell, and the cell size is dynamically changed by a cell coverage optimization function. Therefore, when estimating the movement speed of the terminal according to the prior art, there is a high possibility that the movement speed of the terminal is larger than the actual movement speed.

Meanwhile, in the conventional method, the terminal estimates its own moving speed separately from the base station, and the terminal controls the handover event by using the same. In more detail, the base station transmits a handover related parameter to the terminal. In addition, the terminal estimates its moving speed to one of High, Medium, and Low by using the number of handovers occurring for a certain period according to the conventional LTE standard. Subsequently, the terminal detects a parameter corresponding to its estimated moving speed among parameters received from the base station, determines a handover event start time, and uses the same to initiate a handover event. That is, when the estimated movement speed and the actual movement speed of the terminal are large, the handover event start time is incorrectly determined. When the estimated movement speed is slower than the actual movement speed, the handover is not performed at an appropriate time. If the estimated movement speed is faster than the actual movement speed, there is a problem that the possibility of attempting a handover event is excessively high.

In addition, in the conventional LTE system, since the terminal and the base station separately estimate the moving speed of the terminal, when one of the terminal and the base station incorrectly measures the moving speed of the terminal, it is difficult for the terminal and the base station to secure synchronization regarding the moving speed. Problems also arise.

2 is a conceptual diagram of a wireless communication system including base stations for controlling cells of various sizes according to an embodiment of the present invention.

Referring to FIG. 2, the wireless communication system includes a terminal 201, a first base station 202 controlling cell A 205, a second base station 203 controlling cell B 206, and a cell C ( 207 includes a third base station 204. In addition, in the present embodiment, the terminal 201 moves through the cell B 206 from the cell A 205 to the cell C 207.

In order to solve the above-described problems, the present invention shares cell size information between base stations 202, 203, and 204, and the base stations 202, 203, and 204 move the terminal 201 using such cell size information. By accurately estimating the speed, the base stations 202, 203, and 204 inform the corresponding terminal 201 of the estimated moving speed of the terminal 201 to obtain synchronization with respect to the moving speed. In this embodiment, the terminal 201 has moved from the cell A 205 to the cell C 207 through the cell B 206 to control the cell C 207. Assume that 204 estimates the moving speed of the terminal 201.

First, as a scheme for sharing cell size information between base stations 202, 203, and 204, there is a core network approach and a distributed approach. The third base station 204, which intends to estimate the moving speed of the terminal 201 in the core network approach, may include sizes of cells, for which the terminal 201 has been handed over for a period of time, that is, cells A 205 and B B206. Information is sent from the core network. Possible core networks include OAM / SON / Cell planning tools. This core network approach is suitable for systems with relatively little variation between the sizes of the cells.

The distributed approach, on the other hand, is suitable for systems where the variation between cell sizes is relatively large or the cell size changes dynamically. In the distributed approach, each of the base stations 202, 203, and 204 recognizes its cell size in real time to an adjacent cell through an x2 interface. In addition, in the distributed approach, the terminal 201 needs to share not only the size information of the cell before handover, but also the size information of the cells, which have been handed over for a predetermined time. That is, since not only the size information of the cell B 206, but also the size information of the cell A 205, which is the previous cell, is required, accurate exchange speed measurement of the terminal is not sufficient only by exchanging size information between neighboring cells. For example, in order to accurately measure the moving speed of the terminal 201 in the third base station 204, not only the cell B 206 but also the size information of the cell A 205 is required.

In addition, in the distributed approach, cell size information controlled by the base stations 202, 203, and 204 includes coarse grain size information and fine-grained size information. Coarse grain size information refers to information on a cell type, and cell types include macro cells, femto cells, and pico cells. The weight of the cell may be added to calculate the size of cells that the terminal has moved, and the moving speed of the terminal may be estimated using the weight. Fine-grained size information may be considered as more precise cell size information. That is, by measuring the transmission power of the downlink signal transmitted to the terminal located at the cell edge for each base station can accurately measure the size of the cell.

3 is a flowchart illustrating a signal transmitted and received to share cell size information between base stations in a wireless communication system according to an exemplary embodiment of the present invention. In the embodiment of the present invention, it is assumed that the terminal moves from cell A 301 to cell C 303 via cell B 302. In addition, it is assumed that a distributed approach is used as a method of sharing cell size information between base stations described above.

In the existing LTE standard, the number of handovers within a predetermined time is measured, and whether the reference handover number is exceeded or not is estimated to move the terminal to one of high / medium / normal. However, in the embodiment of the present invention, a parameter according to each cell size is set, and the moving speed of the terminal is estimated using the parameter corresponding to the cell size.

Referring to FIG. 3, the base station controlling the cell A 301, the cell B 302, and the cell C 303, respectively, shares cell size information through an x2 interface. To this end, when the terminal hands over to another base station, the base station adds the following fields to the UE history information defined in the existing LTE standard and transmits the size information of the cell controlled by the base station.

In more detail, in the existing UE history information, there is a list field of cells to which the UE has been handed over and a dwell time in each cell. In the present invention, in addition to this information, the type of each cell (macro cell, A cell type field (cell type) indicating a femto cell, a pico cell, etc.) or a cell size field indicating a radius of each cell measured using the downlink signal transmission power of the base station is newly added.

When the base station controlling the cell B 302 intends to estimate the moving speed of the terminal, the moving speed of the terminal using the size information 304 of the cell A 301 transmitted from the base station controlling the cell A 301. Estimate On the other hand, when the terminal performs a handover from cell B 302 to cell C 303, the base station controlling cell B 302 is not only the size information 305 of cell B 302 but also the cell A 301. The size information 304 is also transmitted to the cell C 303. Accordingly, when the base station controlling the cell C 303 wants to estimate the moving speed of the terminal, the terminal moves using the size information 304 of the cell A 301 and the size information 305 of the cell B 302. The speed can be estimated more accurately.

However, in the present embodiment, only the size information 304 of the cell A 301 and the size information 305 of the cell B 302 are transmitted to the cell C 303 which is the base station for which the terminal is to measure the moving speed. The number of information can be flexibly modified according to the capacity or design use of the wireless communication system.

4 is a flowchart illustrating a method in which a base station and a terminal match movement speed information of a terminal in an embodiment of the present invention.

Referring to FIG. 4, in the conventional LTE system, there is a problem in that the terminal and the base station separately estimate the moving speed of the terminal. In the present invention, the base station corresponds to the moving speed of the terminal estimated using the cell size information. The synchronization is obtained by transmitting to the terminal. In more detail, the base station estimates the moving speed of the terminal by the method described above in step 403 and transmits it to the terminal in step 404.

The terminal, which has received its own movement speed information in step 405, maintains the movement speed information calculated by itself when the error between the estimated movement speed and the movement speed information received from the base station is less than or equal to a predetermined value. On the other hand, if the error of the movement speed estimated by the terminal and the movement speed information received from the base station is greater than or equal to the set value, the movement speed information received from the base station is updated to match the movement speed information of the terminal between the base station and the terminal. By sharing the movement speed information of the terminal between the base station and the terminal in this way, it is possible to build an optimized process in setting the handover start time of the terminal.

5 is a block diagram of a base station for estimating the moving speed of the terminal according to an embodiment of the present invention.

Referring to FIG. 5, a base station of a wireless communication system for estimating a moving speed of a terminal according to an embodiment of the present invention includes a cell size information transmitting unit 501 and a terminal moving speed estimating unit 502.

First, when the terminal moves to a cell controlled by another base station of the wireless communication system, the cell size information transmitting unit 501 displays the size information 503 of the cells moved by the terminal for a predetermined time and the size information of the cell controlled by the base station. Send to another base station together. In addition, the cell size information transmitter 501 may transmit cell size information to the other base station through an x2 interface.

The terminal movement speed estimator 502 estimates the movement speed of the terminal as one of High, Medium, and Normal using cell size information. In addition, the movement speed estimator 502 transmits the estimated movement speed of the terminal to the terminal to match the information on the movement speed with the terminal. That is, the terminal receiving its own moving speed information maintains the calculated moving speed information when the error between the estimated moving speed and the moving speed information received from the base station is less than or equal to a set value. On the other hand, if the error of the movement speed estimated by the terminal and the movement speed information received from the base station is greater than or equal to the set value, it is updated with the movement speed information received from the base station to match the information on the movement speed of the terminal between the base station and the terminal.

Meanwhile, the size information of the above-described cells may be a cell type (macro cell, femto cell, pico cell, etc.), and in this case, the terminal movement speed estimator 502 may determine the size of the cell at a time when the terminal stays in the cells that have been handed over. The moving speed of the terminal can be estimated by adding weights according to the type.

In addition, as described above, the size information of the cells may be radius information of the cell calculated by the base station measuring the transmission power of the downlink signal. In this case, the base station of the wireless communication system of the present invention further includes a transmission power measuring unit 504 and a cell size measuring unit 505.

The transmission power measuring unit 504 measures the transmission power of the downlink signal transmitted to the terminal located at the edge of the cell coverage of the base station. In addition, the cell size measuring unit 505 calculates the size of the cell, that is, the radius of the cell using the measured transmission power of the downlink signal.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

1 illustrates a schematic structure of a wireless communication system according to an embodiment of the present invention.

2 is a conceptual diagram of a wireless communication system including base stations for controlling cells of various sizes according to an embodiment of the present invention.

3 is a flowchart illustrating a signal transmitted and received in order to share cell size information between base stations in a wireless communication system according to an embodiment of the present invention.

4 is a flowchart illustrating a method in which a base station and a terminal match movement speed information of a terminal in an embodiment of the present invention.

5 is a block diagram of a base station for estimating the moving speed of the terminal according to an embodiment of the present invention.

Claims (8)

When the terminal moves from a cell controlled by the first base station to a cell controlled by the second base station, the first base station displays the size information of the cells moved by the terminal and the cell controlled by the first base station for a predetermined time. Transmitting to 2 base stations; Estimating a moving speed of the terminal by using the size information of the cell at the second base station; And And transmitting the estimated movement speed information of the terminal from the second base station to the terminal so as to match the movement speed information of the terminal. The method of claim 1, wherein the size information of the cell is And a terminal type information of the cell. The method of claim 1, wherein the size information of the cell is The base station controlling the cell is a size information calculated by measuring the downlink transmission power of the base station and using it, the terminal movement speed estimation method in a wireless communication system. In the base station of the wireless communication system for estimating the moving speed of the terminal, A cell size information transmitter configured to transmit, to the other base station, size information of cells that the terminal has moved and cell controlled by the base station to the other base station when the terminal moves to a cell controlled by another base station of the wireless communication system; And And a terminal movement speed estimator for estimating a movement speed of the terminal using the size information of the cell. The method of claim 4, wherein the size information of the cell And base station information of the cells. The method of claim 4, wherein A transmission power measurement unit for measuring transmission power of a downlink signal transmitted to a terminal located at a cell coverage edge of the base station; And a cell size measuring unit configured to calculate size information of a cell controlled by the base station by using the downlink transmission power. The method of claim 4, wherein the cell size information transmission unit The base station of the wireless communication system, characterized in that for transmitting the size information of the cell to the other base station via an X2 interface. The method of claim 4, wherein the terminal moving speed estimating unit And transmitting the estimated moving speed of the terminal to the terminal to match the moving speed information with the terminal.

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