KR20100137187A - Method for controlling handover in mobile internet system - Google Patents

Abstract

PURPOSE: A handover control method in an indoor base station is provided to enable an indoor base station to temporarily lower the transmission signal strength, thereby satisfying a handover condition within a short time. CONSTITUTION: An indoor eNB sets reducing amount of transmission signal strength(301). The indoor base station reduces the transmission signal strength as much as set reduced amount according to reception of a handover notification message from a terminal(302). The indoor base station repetitively reduces the transmission signal strength as much as reducing amount until satisfying the handover determination condition. According to completion of a handover of a terminal, the indoor base station increases the transmission strength as much as reduction amount(303).

Description

Handover control method in indoor base station {METHOD FOR CONTROLLING HANDOVER IN MOBILE INTERNET SYSTEM}

The present invention relates to a handover control method in an indoor base station. More specifically, when a terminal handovers from an indoor base station to an outdoor base station, the indoor base station lowers the transmission signal strength for a short time, thereby performing a handover. The present invention relates to a handover control method in an indoor base station for supporting handover of a terminal more quickly by satisfying an over condition.

In the following embodiment according to the present invention will be described by taking an indoor base station based on a portable Internet, but the present invention is not limited thereto.

The present invention is derived from the research conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunication Research and Development. [Task control number: 2007-S-029-03, Assignment name: WiBro system technology for home use / business] Development].

Wireless Broadband (WiBro) systems provide Internet services in a wireless environment, such as Wi-Fi, and provide broadband Internet access, such as high-speed Internet services. In terms of transmission speed, mobility, cell radius, etc., it can supplement the advantages and disadvantages in terms of transmission distance and transmission speed of current mobile communication and wireless LAN, and can provide wireless internet service of more than 1Mbps in the city without interruption while on the move. Is a representative mobile communication technology.

The portable Internet system can use a portable wireless terminal (portable Internet terminal) anytime, anywhere to access the Internet at a high speed transmission speed even when moving, to obtain or utilize a variety of information and content. Therefore, like many existing cellular mobile communication systems, the portable Internet system supports handover to ensure mobility of mobile terminals. In addition, the portable Internet system is a complementary relationship between a cellular mobile communication system having nationwide wide area and high speed mobility and a wireless LAN system supporting high speed transmission speed indoors.

However, in the portable Internet system, various kinds of base stations are located at the same time. These various types of base stations can be broadly divided into indoor base stations and outdoor base stations, which are divided into cell coverage perspectives and main installation sites and applications.

In general, handover includes a communication path (base station ↔ terminal communication path) so that a mobile terminal can maintain communication when entering a cell area of another base station out of the cell area of a serving base station currently communicating. This refers to changing to a target base station located in the movement direction of the terminal.

The portable Internet should be able to continuously provide services with guaranteed quality of service (QoS) on the go. For this purpose, the handover technology used in the mobile Internet uses a hard handover technology, which is a method of breaking an existing call line and connecting to a new base station, but recently using two or more base stations, Soft handover technology that can support high handover is being considered. The handover technique may be divided into a network topology acquisition procedure for periodically measuring parameter values required for handover determination and a procedure for determining and performing a handover.

In general, a portable Internet system in an indoor environment supports handover as in an outdoor environment in order to provide seamless communication to a portable Internet terminal located in a specific area of an indoor environment. When the handover control procedure of the outdoor portable Internet system is applied to the system, the candidate base station (target base station) includes not only indoor base stations but also adjacent outdoor base stations, and the base station to be handed over is selected according to signal strength. do.

In this way, if the neighboring outdoor base station is included in the base station to be handed over, a handover occurs from the indoor base station to the neighboring outdoor base station or from the neighboring outdoor base station to the indoor base station when the terminal located in the area of the indoor base station moves. When a handover occurs from an indoor base station to a neighboring outdoor base station or from a neighboring outdoor base station to an indoor base station, the core router (ACR) is changed to perform a network re-entry procedure.

Hereinafter, a handover scenario in a portable Internet system including an indoor base station and an outdoor base station will be described with reference to FIG. 1.

1 is an exemplary diagram of a portable Internet system consisting of an indoor base station and an outdoor base station.

As shown in FIG. 1, in a portable Internet system including an indoor base station and an outdoor base station, outdoor base stations 12-1 to 12-3 are disposed in a cell center, and outdoor base stations 12-1 to 12- The indoor base stations 13-1 to 13-8 in the cell area provided by 3) are independent (13-1, 13-2, 13-5 to 13-8) or group 13-3, 13-. 4) (2f) is arrange | positioned. In addition, indoor base stations 13-2 and 13-5 are located at portions where two or more cell regions overlap.

In other words, the indoor base station in the portable Internet system may operate as a single base station, but several indoor base stations may be gathered in a building or a specific area to form a group of indoor base stations.

Here, the outdoor base stations 12-1 to 12-3 are "BS", the indoor base stations 13-1 to 13-8 are "Inner_BS", the terminal is "MS", and the indoor base station group is It is indicated by "G".

In addition, BS and Inner_BS, MS, and G are distinguished by attaching numbers such as BS1, Inner_BS1, MS1, or G1, and indoor base station 1 (Inner_BS1) (13-1) belonging to outdoor base station 1 (BS1) 12-1. ) Is designated as "BS1.Inner_BS1".

In addition, indoor base station 3 (Inner_BS3) 13-3 constituting group 2f belonging to outdoor base station 2 (BS1) 12-2 is designated as "BS2.G1.Inner_BS3", and indoor base station 4 ( Inner_BS4) (13-4) is designated as "BS2.G1.Inner_BS4".

In such a portable Internet system, cells and cells are not clearly distinguished, and cells are overlapped with each other. That is, the base stations are not uniformly arranged at a certain distance. Thus, when the portable Internet terminal MS moves and performs handover, one or more candidates of the target base station BS exist.

Therefore, for handover, one base station must be selected from a plurality of target base stations, and at this time, the target base station is evaluated with signal strength.

2 is an exemplary view illustrating a handover decision region according to received signal strengths from indoor base stations and outdoor base stations.

As shown in FIG. 2, the portable Internet terminal has a handover decision zone (Zone) according to the received signal strength from the indoor base station and the outdoor base station, and when the mobile base station moves from the indoor base station to the outdoor base station, The handover is initiated when the received signal strength from the device falls below the serviceable level and the received signal strength of the outdoor base station exceeds the serviceable level.

In general, a portable Internet terminal is connected to an indoor base station or an outdoor base station having different characteristics and is provided with a service through a base station suitable for a subscriber's unique environment such as mobility.

When the indoor base station serving the base station moves from the indoor base station to the target base station, the received signal strength from the indoor base station gradually decreases, and the received signal strength from the outdoor base station gradually increases to generate a handover.

That is, in FIG. 2, when the received signal strength is measured outside the handover determination region while the received signal strength is measured in the handover determination region (Zone), handover is performed.

At this time, since the handover starts when the difference between the received signal strength from the serving base station and the received signal strength from the target base station exceeds the threshold in the handover decision region, the received signal strength from the serving base station and the target base station are received. There is a problem that the handover is delayed due to the time taken for the difference between the received signal strengths to exceed the threshold (handover condition is satisfied), that is, the time required for the handover decision.

It is a problem of the present invention to solve the problems of the prior art as described above.

Therefore, when the terminal handovers from the indoor base station to the outdoor base station, the indoor base station lowers the transmission signal strength for a while, thereby satisfying the handover condition within a short time to support the handover of the terminal more quickly. In addition, the present invention provides a method for controlling handover in an indoor base station.

Meanwhile, in the present invention, when there is an outdoor base station terminal that acts as a large interference around the indoor base station, the indoor base station increases the transmission signal strength to induce handover of the outdoor base station terminal, thereby eliminating interference by the outdoor base station terminal. Another object is to provide a handover control method in an indoor base station for improving the performance of a wireless communication system.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a method for controlling a handover in an indoor base station, the method comprising: setting an amount of reduction of a transmission signal strength by the indoor base station; A transmission signal strength reduction step of reducing the transmission signal strength by the set reduction amount as the indoor base station receives the handover notification message from the terminal; And increasing, by the indoor base station, the transmission signal strength by the decrease amount as the handover of the terminal is completed.

On the other hand, the method of the present invention for achieving the other object, the handover control method in the indoor base station, the increment setting step of setting the increase amount of the transmission signal strength by the indoor base station; A first notification step of notifying the indoor base station to the outdoor base station to which the indoor base station belongs as there is a terminal causing interference in the vicinity; A second notification step of notifying the expansion of the communication area by the indoor base station to other nearby base stations according to the handover induction instruction from the outdoor base station; And a handover derivation step of inducing the handover of the terminal by increasing the transmission signal strength by the set increase amount by the indoor base station.

The method may further include resetting the communication area by the indoor base station as the handed-over terminal terminates service use or operates in an idle mode.

The method may further include buffering data to be transmitted by other nearby indoor base stations as the indoor base station notifies the expansion of the communication area; And resetting the communication area by the neighboring indoor base stations as the indoor base station resets the communication area, and then transmits the buffered data.

In the present invention, when the terminal is required to move the handover decision occurs when moving from the indoor base station to the outdoor base station becomes longer, when there is a terminal requesting handover while moving from the indoor base station to the outdoor base station, The time required for handover decision can be shortened by temporarily reducing the transmission signal strength of the base station.

In addition, the present invention induces a handover to an indoor base station that can be connected to the indoor base station terminal causing a large interference around the indoor base station, the efficient progress of the handover procedure between the indoor base station and the outdoor base station and the performance of the wireless communication system Can be increased.

According to the present invention as described above, when the terminal handovers from the indoor base station to the outdoor base station, the indoor base station lowers the transmission signal strength for a while, thereby satisfying the handover condition within a short time, and thus performing handover of the terminal more quickly. There is an effect it can support.

In addition, in the present invention, when there is an outdoor base station terminal acting as a large interference around the indoor base station, the indoor base station increases the transmission signal strength to induce handover of the outdoor base station terminal, thereby eliminating interference by the outdoor base station terminal Therefore, there is an effect of improving the performance of the wireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It can be easily carried out. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a handover control method in a mobile Internet based indoor base station according to the present invention, and illustrates a handover control process when the portable Internet terminal moves from an indoor base station to an outdoor base station.

First, the decrease amount? P of the transmission signal strength is set (301). At this time, the amount of decrease in the transmission signal strength is preferably 3dB as an example.

Subsequently, as the handover notification message is transmitted from the portable Internet terminal, the transmission signal strength is decreased by the set reduction amount (302). In this case, when the reduction amount is applied but the handover decision condition is not satisfied, the reduction amount is repeatedly applied.

This can be expressed as Equation 1 below.

Here, MacroPow ^Curr currently transmitted signal strength of the outdoor base station, the current intensity is FemtoPow ^Curr transmission signal of a base station for indoor use, △ P will decrease, △ H is meant each of the handover decision condition of hysteresis.

At this time, ΔP is the minimum amount to be reduced when the difference between the transmission signal strength of the outdoor base station and the transmission signal strength of the indoor base station is equal to or larger than ΔH which is a handover decision condition. [Delta] P is determined by the difference between signal strengths of the two base stations and [Delta] H, which is a handover decision condition. In general, [Delta] P is a range of 3 to 5 dB. same.

Thereafter, as the handover of the portable Internet terminal is completed, the transmission signal strength is increased again by the decrease amount (303). That is, it returns to the original transmission signal strength.

Looking at this in more detail as follows.

First, the indoor base station calculates a reduction amount ΔP of the transmission signal strength to reduce its communication area (Coverage) to perform the outbound handover quickly. The amount of decrease in the transmission signal strength is a range which does not affect the portable Internet terminal currently serving. That is, the quality of service (QoS) of the other portable Internet terminal in service is guaranteed and set to a range where no handover occurs.

When the mobile Internet terminal connected to the indoor base station moves to the outdoor base station and handovers, the mobile base station transmits a 'MOB_MSHO-REQ' message to the indoor base station. At this time, the indoor base station sends a 'MOB_MSHO-RSP' message in response.

The portable Internet terminal finally sends a 'MOB_HO-IND' message to the indoor base station to notify the handover from the indoor base station to the outdoor base station. The indoor base station sending the 'MOB_MSHO-RSP' message informs neighboring indoor base stations that there will be a change in its communication area. The surrounding indoor base stations do not change their communication area.

The indoor base station reduces the communication area of the indoor base station by applying the previously set transmission signal strength reduction amount ΔP. Accordingly, the portable Internet terminal satisfies the handover decision condition and performs a quick handover process. At this time, the portable Internet terminal selects one of 'Controlled-HO' and 'UnControlled-HO' according to whether the 'MOB_BSHO-RSP' message is received.

When the handover process from the indoor base station to the outdoor base station is completed, the transmission signal strength is increased again to return the communication area of the indoor base station to its original state.

4 is a flowchart illustrating a handover control method in a mobile Internet based indoor base station according to the present invention, and illustrates a handover control process when a terminal connected to an outdoor base station acts as an interference.

First, an increase amount ΔP of transmission signal strength is set (401). At this time, the amount of increase in the transmission signal strength is preferably 3dB as an example.

Thereafter, as there is a portable Internet terminal causing interference in the vicinity, it notifies the outdoor base station to which it belongs (402). At this time, the outdoor base station is notified when the strength and duration of the interference exceed the threshold.

Thereafter, in response to the handover induction instruction from the outdoor base station, the neighboring base stations are notified of the expansion of the communication area (403). The surrounding indoor base station then buffers the data to transmit.

Thereafter, the transmission signal strength is increased by the set increase amount to induce handover of the portable Internet terminal (404). In this case, when the increase amount is applied but the handover decision condition is not satisfied, the increase amount is repeatedly applied.

This can be expressed as Equation 2 below.

Here, MacroPow ^Curr currently transmitted signal strength of the outdoor base station, the current intensity is FemtoPow ^Curr transmission signal of a base station for indoor use, △ P will increase, △ H means a handover decision condition of hysteresis, respectively.

At this time, ΔP is the minimum amount to increase when the difference between the transmission signal strength of the outdoor base station and the transmission signal strength of the indoor base station is equal to or larger than ΔH which is a handover decision condition. [Delta] P is determined by the signal strength difference between the two base stations and [Delta] H, which is a handover decision condition. In general, [Delta] P is a range of 3 to 5 dB. same.

Subsequently, the handovered portable Internet terminal terminates the service or operates in the idle mode, thereby resetting the communication area through the self-organizing network (SON) function (405).

Then, the neighboring indoor base station also transmits the buffered data after resetting each communication area for the changed environment.

Looking at this in more detail as follows.

First, the indoor base station automatically recognizes the surrounding environment by utilizing a self-organizing network (SON) function to perform inbound handover, and increases the transmission signal strength (ΔP) to expand its communication area and Calculate the maximum increase. At this time, the amount of increase in the transmitted signal strength is a range that does not affect the terminal serving. That is, the quality of service (QoS) of the other indoor base station terminals in service is guaranteed and set to a range where no handover occurs.

The indoor base station records the strength and duration of the interference in an alarm message and transmits the signal to the outdoor base station in order to indicate that there is a suspicious terminal causing large interference. At this time, the alarm message is transmitted to the outdoor base station only when the interference strength minimum value or the interference minimum duration time is longer.

The outdoor base station collects the alarm message received from the indoor base station for a certain period and compares whether the terminal in the list managed by the outdoor base station is the suspect terminal. At this time, the use of location-based information (LBS) is also possible.

If it is determined that the outdoor base station is managed by the outdoor base station, the outdoor base station transmits a 'MOB_BSHO-REQ' message to an accessible indoor neighbor base station to instruct the handover to cause interference.

The indoor base station then announces that the communication area is expanded for inbound handover to nearby indoor base stations.

Then, when there are data to be transmitted, neighboring indoor base stations perform buffering on the data for a while.

The indoor base station then increases the communication area. That is, by gradually applying the transmission signal strength increase amount ΔP, the interfering terminal is induced to handover to the indoor base station.

Thereafter, the terminal requests a handover with a 'MOB_MSHO-REQ' message, and the indoor base station transmits a 'MOB_BSHO-RSP' message to the terminal to perform a handover. After the handover ends, when the terminal handing over to the indoor base station terminates the use of the service or enters the idle mode, the indoor base station returns to the optimal communication area by using the SON function. At this time, the surrounding indoor base station calculates and adjusts the respective communication area for the changed environment, and then transmits the buffered data.

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention can be used for indoor base stations and the like.

1 is an exemplary diagram of a portable Internet system consisting of an indoor base station and an outdoor base station.

2 is an exemplary view illustrating a handover determination region according to received signal strengths from indoor base stations and outdoor base stations;

3 is a flowchart illustrating a handover control method in a mobile Internet-based indoor base station according to the present invention;

4 is a flowchart of another embodiment of a handover control method in a mobile Internet-based indoor base station according to the present invention.

* Explanation of symbols for the main parts of the drawings

12-1 to 12-3: indoor base station 13-1 to 13-8: indoor base station

Claims (9)

A handover control method in an indoor base station, A reduction amount setting step of setting, by the indoor base station, a reduction amount of the transmission signal strength; A transmission signal strength reduction step of reducing the transmission signal strength by the set reduction amount as the indoor base station receives the handover notification message from the terminal; And Increasing, by the indoor base station, the transmission signal strength by the decrease amount as the handover of the terminal is completed; Handover control method in an indoor base station comprising a. The method of claim 1, The transmitting signal strength reduction step, The method for controlling handover in an indoor base station characterized in that the transmission signal strength is repeatedly reduced by the amount of reduction until a handover decision condition is satisfied. The method according to claim 1 or 2, The reduction amount setting step, A method for controlling handover in an indoor base station, characterized by setting an amount of reduction in transmission signal strength using Equation A below. Equation A

(Here, the MacroPow ^Curr currently transmitted signal strength of the outdoor base station, the current intensity is FemtoPow ^Curr transmission signal of a base station for indoor use, △ P will decrease, △ H is meant each of the handover decision condition of hysteresis.) A handover control method in an indoor base station, An increment setting step of setting, by the indoor base station, an increase amount of the transmission signal strength; A first notification step of notifying the indoor base station to the outdoor base station to which the indoor base station belongs as there is a terminal causing interference in the vicinity; A second notification step of notifying the expansion of the communication area by the indoor base station to other nearby base stations according to the handover induction instruction from the outdoor base station; And A handover derivation step of inducing the handover of the terminal by increasing the transmission signal strength by the set increase amount by the indoor base station Handover control method in an indoor base station comprising a. The method of claim 4, wherein Resetting the communication area by the indoor base station as the handed-over terminal terminates service use or operates in idle mode Handover control method in an indoor base station further comprising. The method according to claim 4 or 5, Buffering data to be transmitted by other nearby indoor base stations according to the indoor base station notifying the expansion of the communication area; And Transmitting the buffered data after resetting the communication area by the surrounding indoor base stations as the indoor base station resets the communication area. Handover control method in an indoor base station further comprising. The method according to claim 4 or 5, The handover derivation step, And repeatedly transmitting the signal strength by the increment until the handover decision condition is satisfied. The method according to claim 4 or 5, The first notification step, The method of handover control in an indoor base station, wherein the outdoor base station is notified when the strength and duration of the interference exceed a threshold. The method according to claim 4 or 5, The increasing amount setting step, A method for controlling handover in an indoor base station, characterized by setting the increase amount of the transmission signal strength using Equation B below. Equation B

(Here, the MacroPow ^Curr currently transmitted signal strength of the outdoor base station, FemtoPow ^Curr the current transmission signal strength, P is the increase △, △ H of the indoor base station refers to a handover decision of a hysteresis condition, respectively.)

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