KR101808839B1 - Method and apparatus for supporting handoff in communication system - Google Patents

Abstract

In a communication system of a linear cell structure, a base station identifies an antenna for receiving a signal from a mobile terminal among a plurality of antennas distributed in a cell, detects a moving direction of the mobile terminal based on the antenna identified in time order, So that the target BS can complete the preparation for the handoff before receiving the handoff request from the mobile terminal by transmitting the handoff preparation command to the target base station based on the direction of the handoff do.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for supporting handoff in a communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handoff support method and apparatus for a communication system, and more particularly, to a handoff support method and apparatus in a communication system having a linear cell structure.

Future mobile communication systems should be able to support faster and more traffic now to provide multimedia-type ultra-broadband / intelligent services, including intelligent communications, which are expected to increase explosively in the future. Accordingly, a millimeter wave band of 6 GHz or more is attracting attention. However, the millimeter wave has a poor propagation characteristic which is very large in propagation loss and does not diffract. Therefore, in the future mobile communication system using millimeter wave, it is expected that a small cell having a small cell size will be spotlighted.

Especially, in a high-speed mobile environment moving at a high speed such as a vehicle, a train, a ship and an airplane, the small cells are linearly arranged in a linear cell structure. In a small linear cell structure, handoff frequently occurs due to high mobility of a moving object, and handoffs are likely to fail due to frequent handoffs. That is, when the mobile station moves at high speed in a small cell environment, the handoff process is delayed, resulting in a problem that the connection service is disconnected such as data communication speed degradation, data loss, and connection disconnection. Therefore, in the future mobile communication system having such a small linear cell structure, there is a need for a method capable of rapidly handing off frequent handoffs even in a high speed mobile body.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a handoff support method and apparatus in a communication system capable of reducing handoff delay time while systematically and efficiently using radio resources in a mobile communication system with a linear cell structure.

According to an embodiment of the present invention, there is provided a method of supporting handoff of a base station in a communication system in which cells are linearly arranged. A method of supporting handoff includes the steps of sensing a direction of movement of a mobile station based on a signal strength received from a mobile station through a plurality of antennas of the base station distributed in the cell, Predicting the target base station, and transmitting a handoff preparation indication to the target base station before the terminal reaches the handoff area.

The detecting may include identifying an antenna that receives a signal with the highest signal strength from the terminal, and estimating a moving direction of the terminal based on the antenna identified in time sequence.

The handoff support method may further include reserving a channel for a handoff call upon receiving a handoff preparation instruction from another base station.

According to another embodiment of the present invention, there is provided an apparatus for supporting handoff of a mobile terminal in a communication system in which cells are linearly arranged. The handoff support apparatus includes a movement direction sensing unit, a target base station determination unit, and an instruction unit. The movement direction sensing unit identifies an antenna that receives a signal from the mobile terminal among a plurality of antennas of the base station distributed in the cell and senses the direction of movement of the terminal based on the antenna identified in chronological order. The target BS determining unit determines a target BS to which the MS performs a handoff based on the movement direction of the MS. The instruction unit transmits a handoff preparation instruction to the target base station.

The indication unit may transmit a handoff preparation indication to the target base station before the terminal reaches the handoff area.

The instruction unit may determine a transmission time point of the handoff preparation instruction according to the speed of the user equipment and the amount of traffic being used by the user equipment.

The movement direction sensing unit identifies the antenna that receives the signal with the highest signal strength from the terminal and predicts the movement direction of the terminal based on the position of the antenna identified in time sequence.

According to the embodiment of the present invention, in the future linear cell mobile communication system, not only a subscriber can receive a handoff service without call interruption, but also systematically and efficiently uses radio resources, thereby effectively providing a mobile communication service even in a high- Can receive. Particularly, the present invention can effectively support the cloud base station technology, which has recently been spotlighted, by being applied to a structure in which antennas are installed in a distributed manner.

1 is a schematic diagram of a linear cell mobile communication system according to an embodiment of the present invention.
2 is a diagram illustrating a handoff method of a terminal according to an embodiment of the present invention.
3 is a flowchart illustrating a handoff support method of a base station according to an embodiment of the present invention.
4 is a diagram illustrating a handoff support apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

Throughout the specification, a terminal may be referred to as a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station (HR- May refer to a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) HR-MS, SS, PSS, AT, UE, and the like.

In addition, the base station (BS) includes an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B ), An access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) BS, Node B, eNB, AP, RAS, BTS, MMR-BS, and the like.

Also, the base station of the small cell includes a femto BS, a home Node B, a home eNB (HeNB), a pico BS, a metro BS, a micro BS, , And may include all or some of the functions of a femto base station, an HNB, an HeNB, a pico base station, a metro base station, a micro base station, and the like.

A method and apparatus for supporting handoff of a communication system according to an embodiment of the present invention will now be described in detail with reference to the drawings.

1 is a schematic diagram of a linear cell mobile communication system according to an embodiment of the present invention.

Referring to FIG. 1, a mobile communication system in a mobile environment moving at high speed, such as a vehicle, a train, a ship and an airplane, may include a plurality of cells 10 and 20 arranged in a linear array. The cells 10 and 20 may be small cells having a small size. A small cell is a cell in which the size of a cell operated by a single base station is about 10 to 20 m in a mobile communication system, and a typical example of a small cell is a femtocell or a picocell.

Cells 10, 20 include base stations 100, 200 that manage cells 10, 20, respectively.

The base station 100 includes antennas 101, 102, and 103 and may be connected to the antennas 101, 102, and 103 wirelessly or by wire. The base station 200 includes antennas 201, 202, and 203 and may be connected to the antennas 201, 202, and 203 wirelessly or by wire. An antenna identifier is assigned to each of the plurality of antennas 101, 102, 103, 201, 202, and 203 of the base stations 100 and 200.

The base stations 100 and 200 transmit the cell identifiers and the antenna identifiers of the cells 10 and 20 managed by the base stations 100 and 200 to the terminal 300 through the control channel.

The terminal 300 can identify the service area based on the cell identifier and the antenna identifier.

The plurality of antennas 101, 102, 103, 201, 202 and 203 of the base stations 100 and 200 each have service areas 110, 120, 130, 210, 220 and 230, , 201, 202 and 203 transmit signals to the corresponding service areas 110, 120, 130, 210, 220 and 230 or receive signals of the corresponding service areas 110, 120, 130, 210, 220 and 230 .

At this time, a plurality of antennas 101, 102, 103, 201, 202, and 203 of the base stations 100 and 200 are linearly dispersed in the cells 10 and 20, And may be partially overlapped with the area. Therefore, the service area of the cell 10, 20 can be composed of a combination of the service areas of the antennas installed in the cells 10, 20. For example, in the case of the communication system shown in FIG. 1, the service area of the cell 10 includes a combination of service areas 110, 120 and 130 of the antennas 101, 102 and 103 in the service area of the cell 10 And the service area of the cell 20 may be composed of a combination of the service areas 210, 220, and 230 of the antennas 201, 202, and 203 in the service area of the cell 20.

At this time, an area (hatched area) where the service area of the cell 10 and the service area of the cell 10 overlap is the handoff area. That is, the area where the service area 130 of the antenna 103 and the service area 210 of the antenna 201 overlap is the handoff area between the cells 10 and 20.

When the terminal 300 enters the handoff area, a handoff is started.

In a moving object environment moving at a high speed, handoff frequently occurs due to high-speed mobility of the terminal 300. If a handoff is started after the terminal 300 enters the handoff area, , Data loss, and connection disconnection. Therefore, faster handoff processing is required in a mobile environment moving at high speed.

The base stations 100 and 200 transmit the direction of movement of the terminal 300 based on the signal strength of the terminal 300 received through each of the antennas 101, 102, 103, 201, 202 and 203 for faster handoff processing And predicts a target base station to which the terminal 300 handoffs based on the movement direction of the terminal 300. [ The base stations 100 and 200 transmit a handoff preparation instruction to the target base station before the terminal 300 reaches the handoff area.

The target base station which has been instructed to prepare for handoff performs a preparation procedure for handoff such as channel reservation for handoff call.

As described above, the target base station can perform fast handoff even if the terminal 300 reaches the handoff area and starts the handoff by performing the preparatory procedure for the handoff in advance.

2 is a diagram illustrating a handoff method of a terminal according to an embodiment of the present invention.

2, the terminal 300 measures the strength of a signal received from a base station (hereinafter referred to as a "serving base station") to which the terminal is currently connected, for example, RSSI (Received Signal Strength Indicator) If the strength of the received signal from the base station decreases below the threshold value, the handoff is determined (S210). Generally, when the terminal 300 reaches the handoff area, the received signal strength from the serving base station becomes lower than a threshold value, and the terminal 300 determines a handoff.

The terminal 300 selects a target base station to be handed off (S220). The MS 300 measures a strength of a signal received from a neighboring BS and selects a neighboring BS having the largest received signal strength as a target BS.

After selecting the target base station, the terminal 300 transmits a handoff request message to the target base station (S230). The target base station transmits a handoff response message for the handoff request message.

Upon receiving the handoff response message from the target base station (S240), the terminal 300 performs a handoff with the target base station (S250).

In general, every cell uses a scheme for reserving a channel for a handoff call. A new call can not be assigned to a channel reserved for handoff. The target base station performs a handoff with the terminal 300 using the reserved channel. The channel reservation scheme for such a handoff call causes a waste of a channel in a cell in which handoff is not frequent.

In the embodiment of the present invention, the target base station supports fast handoff by reserving resources for handoff before receiving the handoff request message from the terminal 300.

3 is a flowchart illustrating a handoff support method of a base station according to an embodiment of the present invention.

Referring to FIG. 3, a serving base station (e.g., 100) detects a moving direction of a terminal by identifying an antenna that receives a signal from the terminal 300 (S310). The serving base station 100 measures the signal strength received from the terminal 300 through each of the antennas 101, 102 and 103 and detects the moving direction of the terminal 300 by identifying the antenna having the largest signal strength. For example, when the antennas 101, 102, and 103 of the base station 100 are A, B, and C, when antennas having the largest received signal strength are A antennas, B antennas, and C antennas in chronological order, The direction sensing unit 310 can predict the direction toward the position of the C antenna through the position of the B antenna at the position of the A antenna toward the direction of the terminal 300. [

The serving base station predicts a target base station to which the mobile station 300 handoffs based on the movement direction of the mobile station 300 (S320). The serving base station may determine at least one base station closest to the target base station (for example, 200) based on the movement direction of the terminal 300. [

The serving base station 100 transmits a handoff preparation instruction to the predicted target base station 200 (S330). The serving base station 100 performs a handoff preparation procedure in the target base station 200 before the terminal 300 reaches the handoff area in consideration of the network environment such as the moving speed of the terminal 300, It may transmit the handoff preparation instruction to the target base station 200 considering the sufficient time to be completed. For example, the serving base station 100 may perform a handoff preparation procedure in the target base station 200 before the terminal 300 reaches the handoff area when the movement speed of the terminal 300 is high or the amount of traffic being used is high It is possible to transmit the handoff preparation instruction to the target base station 200 sooner so that it can be completed.

When the target base station 200 receives the handoff preparation command from the serving base station 100, the target base station 200 reserves resources for handoff. In this case, since it is not necessary to reserve a dedicated channel for handoff as in the conventional art, resources can be efficiently used.

When the terminal 300 reaches the handoff area, the terminal 300 starts handoff with the target base station 200. At this time, the target base station 200 can support fast handoff of the terminal 300 using resources reserved for handoff.

4 is a diagram illustrating a handoff support apparatus according to an embodiment of the present invention.

Referring to FIG. 4, the handoff support apparatus 400 includes a movement direction sensing unit 410, a target base station determination unit 420, and an instruction unit 430. The handoff support device 400 may be implemented within the base station 100, 200.

The movement direction sensing unit 410 detects the movement direction of the terminal 300 by identifying the antenna that receives the signal from the terminal 300. [ The movement direction sensing unit 410 can measure a signal intensity received from the terminal 300 through each antenna and can detect a movement direction of the terminal by identifying an antenna having the highest signal intensity.

The target base station determining unit 420 determines the target base station based on the moving direction of the terminal 300. [

The instruction unit 430 transmits a handoff preparation instruction to the target base station. The instruction unit 430 may determine the transmission time point of the handoff preparation instruction in consideration of the network environment such as the speed of the terminal, the amount of traffic in use, and the type of service, and the transmission time may be determined before the terminal reaches the handoff region have.

Upon receiving the handoff preparation instruction, the target base station performs a preparation procedure such as reserving a channel for a handoff call, and then performs a handoff with the terminal 300 upon receiving a handoff request from the terminal 300 do.

In this manner, the handoff support apparatus 400 identifies an antenna that receives signals for a plurality of base station antennas distributed in the cell, predicts a target base station to be handed off in advance, and enables the target base station to prepare for handoff The possibility of handoff failure can be reduced. Accordingly, the terminal 300 not only can receive uninterrupted service but also utilize radio resources systematically and efficiently, thereby effectively providing a high-speed mobile communication service.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, Such an embodiment can be readily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (7)

A method for supporting handoff in a base station in each cell in a communication system,
Detecting a moving direction of the mobile station based on a signal strength received from the mobile station through a plurality of antennas of the base station distributed in each cell in a structure in which cells are linearly arranged;
Estimating a target base station to which the mobile station will handoff based on the direction of movement of the mobile station, and
Transmitting a handoff preparation command to the target base station before the terminal reaches the handoff area
Gt; The method of claim 1,
The sensing step
Identifying an antenna that has received the signal with the highest signal strength from the terminal, and
And predicting the direction of movement of the terminal based on the antenna identified in time sequence. The method of claim 1,
When receiving a handoff preparation instruction from another base station, reserving a channel for a handoff call
Further comprising the steps of: An apparatus for supporting handoff of a mobile station in a base station in each cell in a communication system,
In a structure in which cells are linearly arranged, an antenna for receiving a signal from the mobile terminal among a plurality of antennas of a base station dispersed in each cell is identified, and a moving direction of the terminal is determined based on an antenna identified in time order A moving direction sensing unit for sensing,
A target base station determination unit for determining a target base station to which the mobile station performs a handoff based on a moving direction of the mobile station,
A handover preparation instruction to the target base station;
The handoff support device comprising: 5. The method of claim 4,
Wherein the indication unit transmits a handoff preparation indication to the target base station before the terminal reaches the handoff area. 5. The method of claim 4,
Wherein the instruction unit determines a transmission time point of the handoff preparation instruction according to a speed of the terminal and an amount of traffic being used by the terminal. 5. The method of claim 4,
Wherein the movement direction sensing unit identifies an antenna that receives a signal with the highest signal strength from the terminal and predicts a moving direction of the terminal based on the position of the antenna identified in time order.

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