KR100937873B1 - Method for inter-radio access technology handover in mobile communication systems - Google Patents

Abstract

The present invention relates to a handover between different wireless communication systems, and in a method of transmitting a forward synchronization signal for handover between wireless communication systems using different wireless access technologies, on a wireless communication system to which a mobile station intends to move. Generating, by an existing base station, a frame including two or more primary-broadcasting channels (P-BCHs) including the frame number of the wireless communication system within one frame period and transmitting the frame through a forward link; Including, by acquiring the LTE cell search and system related information before the inter-RAT handover, there is an effect of seamless Inter-RAT handover.

OFDM, Wireless Access Technology, Handover, Synchronization Channel, Broadcast Channel, Inter-RAT Handover / Measurement

Description

Method for handover between wireless communication systems using different radio access technologies and a method for transmitting forward synchronization signals for the same {Method for inter-radio access technology handover in mobile communication systems}

The present invention relates to handover between different wireless communication systems, and more particularly, a WCDMA / LTE dual mode terminal or a GSM / WCDMA / LTE triple mode terminal, from WCDMA system to LTE system or from GSM system to LTE system. The present invention relates to a procedure and method for seamless handover.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development. [Task management number: 2005-S-404-13, Task name: 3G Evolution wireless transmission technology development] .

The third generation of mobile communication systems, also called International Mobile Technology (IMT) -2000, uses Code Division Multiple Access (CDMA) technology and provides packet-based text wherever mobile phone or terminal users are anywhere in the world. It provides a consistent service for transmitting digitized voice, video and multimedia data at high speeds of 2 Mbps and higher.

These third generation mobile communication systems are divided into asynchronous WCDMA (Wideband CDMA), which is adopted as a European standard, and a synchronous CDMA-2000, which is adopted as a US standard.

WCDMA is based on the Global System for Mobile communication (GSM) and General Packet Radio Services (GPRS), which are widely used in Europe and elsewhere, and is also called a Universal Mobile Telecommunication Service (UMTS) system.

CDMA-2000 is based on 2nd generation CDMA system such as IS-95 or J-STD008 used in Korea, USA, Japan, etc. Currently, there is a trend to harmonize the two systems, and accordingly, various techniques for compatibility between the two systems have been studied. One of them is a technology related to handover that can occur when a mobile terminal (Mobile Terminal, Mobile Station or User Equipment) moves between two systems.

Handover is a technology that allows a user to communicate without interruption of a call when the mobile terminal moves from one cell to another cell of the cellular mobile communication system. There are two methods of handover: one is a soft handover that communicates using a plurality of channels in an area where two or more cells overlap, and drops the channel when one channel quality falls below a reference value. One is a hard handover that attempts to connect to an adjacent cell by disconnecting the channel of the previous cell when moving between cells.

Currently, in the 3rd Generation Partnership Project (3GPP), standardization of wireless transmission technology based on orthogonal frequency division multiplexing (OFDM) under the name of 3G Long Term Evolution (LTE) is underway.

For example, before moving from LTE to WCDMA, a UE needs to acquire a sync / cell ID of an LTE cell during a transmission gap (eg, 5 ms or less). In the current LTE standard, since a synchronous channel (SCH) exists every 5 ms, seamless handover is possible.

However, demodulating a Primary-Broadcasting Channel (P-BCH) that contains information related to initial LTE system connection (e.g., system frame number) before moving on to LTE system for smoother Inter-RAT handover. It is important.

P-BCH channel coding block size of the current LTE system is a basic unit is 10 msec, the mobile station must receive 10 msec continuously to detect the system timing of the LTE system. As mentioned above, in the case of WCDMA system, it is smaller than 10msec to define the transmission gap to support Inter-ART handover. Therefore, there is a disadvantage in that handover from WCDMA to LTE becomes difficult.

The present invention provides a procedure and method for performing an Inter-RAT handover in which a dual or triple mode terminal hands over from a WCDMA or GSM radio access system to a 3GPP LTE (Long-Term Evolution) radio access system.

The present invention provides a frame structure including an SCH / P-BCH that supports measurement of handover.

The present invention provides a method of transmitting a forward synchronization signal for handover between wireless communication systems using different radio access technologies.

In order to solve the above technical problem, the forward sync signal transmission method proposed by the present invention is a forward sync signal transmission method for handover between wireless communication systems using different radio access technologies, and the mobile station intends to move. Generating a frame including two or more primary-broadcasting channels (P-BCHs) including a frame number of the wireless communication system within a frame period by a base station existing on the base station and transmitting the frame through a forward link; Characterized in that it comprises a step.

In addition, the frame is characterized in that two or more P-BCHs included in one frame period have the same system frame number.

In addition, the P-BCH includes system information on the bandwidth and the number of antennas of the wireless communication system, and is characterized in that the same in two or more P-BCH included in one frame period.

In addition, the P-BCH may be self decodable within a transmission gap of a wireless communication system in which the mobile station is currently communicating.

In order to solve the above technical problem, the handover method between wireless communication systems using different radio access technologies presented in the present invention may also include a system frame number for handover between wireless communication systems using different radio access technologies. A handover method using a P-BCH (Primary-Broadcasting Channel) comprising a frame including two or more frames within a frame period, the handover method comprising the steps of: (a) The cell ID and signal strength of the target base station are measured by using the frame of the target base station of the wireless communication system to be moved within the transmission gap of the home base station, and demodulated by the P-BCH included in the frame. Obtaining a wireless communication system frame number in which the target base station is included; Requesting a handover of the mobile station to a corresponding target base station; (c) transmitting, by the target base station, a system frame number indicating a handover time to the mobile station in response to the handover request; and (d) the handover. At the time point, the target base station allocating resources for communication with the mobile station.

In addition, the step (a) is a primary-synchronous channel included in a frame of a target base station of a wireless communication system to move within a transmission gap of a wireless communication system with which the mobile station is currently communicating. The cell ID and signal strength of the target base station are measured by using a CHannel, P-SCH), a secondary-synchronous CHannel (S-SCH), and a pilot signal (Reference Signal, RS).

In addition, the step (a) is to demodulate the P-BCH included in the frame to obtain the system information about the frame number of the wireless communication system including the target base station, the bandwidth of the wireless communication system, the number of antennas do.

In addition, the step (b) is a step of transmitting a cell ID of the target base station, a signal strength and a radio communication system frame number including the target base station to the home base station and the home base station corresponding to the cell ID Requesting handover of the mobile station to the mobile station.

In the step (c), the home base station receives a system frame number indicating a handover time to the mobile station in response to the handover request, and the home base station transmits a system frame number to the mobile station. And transmitting the handover indication and the system frame number.

In the step (d), the mobile station transmits a handover preamble to the target base station at the time of handover and when the target base station receives the handover preamble, allocates resources for communication with the mobile station. Characterized in that it comprises a step.

In order to solve the above technical problem, a handover method between wireless communication systems using different radio access technologies proposed by the present invention includes a system frame number for handover between wireless communication systems using different radio access technologies. In a handover method using a forward synchronization signal composed of frames including two or more primary-broadcasting channels (P-BCHs) within one frame interval, a transmission blank interval of a home base station of a wireless communication system with which a mobile station currently communicates. The target base station is included by measuring the cell ID and signal strength of the target base station using a frame of the target base station of the wireless communication system to be moved within a transmission gap, and demodulating the P-BCH included in the frame. Acquiring a wireless communication system frame number; Transmitting a cell ID of a target base station, a signal strength, and a frame number of a wireless communication system including the target base station; requesting a handover of the mobile station from the home base station to a target base station corresponding to the cell ID; The base station receiving a system frame number indicating a handover time to the mobile station in response to the handover request, transmitting a handover instruction for the target base station and the system frame number to the mobile station to the home base station; And transmitting, by the mobile station, a handover preamble to the target base station at the time of handover, and allocating resources for communication with the mobile station when the target base station receives the handover preamble. It is characterized by.

As described above, the present invention has an effect of seamlessly inter-RAT handover by acquiring LTE cell search and system related information before inter-RAT handover.

In addition, the present invention provides a frame structure including the SCH / P-BCH to support the measurement of the handover to enable seamless handover between wireless communication systems using different radio access technologies.

In addition, the present invention transmits a forward synchronization signal consisting of a frame including a SCH / P-BCH to support the measurement of handover hand between wireless communication systems using different radio access technologies in a dual or triple mode mobile terminal Allow over to be performed.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a diagram illustrating handover between different radio access technologies according to an exemplary embodiment of the present invention.

As shown in FIG. 1, when a specific GSM / LTE dual mode terminal or a GSM / WCDMA / LTE triple mode terminal wants to receive a high speed / high quality LTE multimedia service from a low speed GSM (or WCDMA) service, a GSM (or WCDMA) radio There may be a situation in which an inter-RAT handover is required from the access system to the LTE wireless access system.

The GSM (or WCDMA) and LTE wireless communication system of FIG. 1 is an example of a wireless communication system using different wireless access technologies, and a radio using all other wireless access technologies other than those wishing to access the LTE wireless communication system. It is clearly stated that communication systems are also included in the scope of the present invention.

According to the present invention, in the case of a wireless communication system using different wireless access technologies, an LTE wireless communication system supporting a measurement procedure and a handover procedure for smooth and seamless handover from another wireless communication system to an LTE wireless communication system A channel structure of a synchronous channel (SCH) and a primary-broadcasting channel (P-BCH) is proposed.

FIG. 2 is a diagram illustrating a frame including a transmission gap of a conventional GSM or WCDMA system.

As shown in FIG. 2, a GSM or WCDMA wireless communication system defines a transmission gap (100), during which the mobile station temporarily changes the currently communicating frequency and uses it to search for downlink signals of other frequencies in the same system. It is used to search for other wireless communication systems, for example 3G LTE downlink signals.

This procedure is to facilitate the inter-frequency hard handover or inter-RAT handover between mobile systems supported by the mobile station. In the GSM or WCDMA wireless communication system, a transmission gap 100 is about 5 msec long.

3 is a diagram illustrating a P-BCH structure implemented when handover between different radio access technologies is not considered.

As shown in FIG. 3, a typical wireless communication system defines a 10 msec frame, and a frame number is assigned to each frame to control all mobile stations in the system.

In the LTE wireless communication system, a system frame number (SFN) is assigned every 10 msec, and this number is modulo 4096. Modulo 4096 means that the number is… 4094, 4095, 0, 1, 2... , 4094, 4095, 0, 1, 2,... It means that it works.

The system frame number (SFN) is transmitted to the mobile station on the P-BCH once every 10 msec. The mobile station demodulates the P-BCH to obtain the system timing of the LTE wireless communication system to which the current mobile station belongs.

If the Inter-RAT handover is not considered from the GSM radio system to the LTE radio system (GSM to LTE) or from the WCDMA radio system to the LTE radio system (WCDMA to LTE), the P-BCH 300-A When the information to be transmitted from the base station (or cell) of the LTE wireless communication system to the mobile station only need to be transmitted once per 10 msec. As a result, the packet of the P-BCH needs to be transmitted only once every 10 msec.

4 is a diagram illustrating a P-BCH structure implemented when considering handover between different radio access technologies according to an embodiment of the present invention.

In order to support inter-RAT handover from a GSM wireless communication system to an LTE wireless communication system (GSM to LTE) or from a WCDMA wireless communication system to an LTE wireless communication system (WCDMA to LTE), the P-BCH has at least a transmission space interval ( It must be self decodable within the transmission gap, P-BCH must be transmitted at least twice within 10 msec of the LTE wireless communication system, and each of the two P-BCH packets is self decodable. And each packet must contain the same system frame number (SFN).

4 is a conceptual diagram illustrating a P-BCH channel structure of an LTE downlink for supporting Inter-RAT handover according to the present invention.

As can be seen in FIG. 4, the P-BCH coding blocks 400-A and 400-B of the LTE wireless communication system for supporting the Inter-RAT handover are transmitted at least twice per 10 msec frame and transmitted within 10 msec. Each P-BCH coding block implies the same SFN number.

In addition, the P-BCH may further include the number of transmit antennas, bandwidth information, etc. of the target base station, which is also the same in the two coding blocks in the 10 msec frame.

5 is a flowchart illustrating a handover procedure between different radio access technologies according to an embodiment of the present invention.

The mobile station 500 communicating with the currently connected home base station 510 (step S0) periodically checks the target base station (or cell) 520 of the target base station (or cell) 520 that exists on the LTE wireless communication system during the transmission gap. Signal strength, cell ID, etc. are included in the primary-synchronous channel (P-SCH), secondary-synchronous channel (S-SCH) and pilot signal (reference signal) of the downlink of the LTE wireless communication system. , RS) and demodulate the P-BCH to obtain information such as the number of transmit antennas and bandwidth information of the target base station included in the P-BCH (step S1).

The mobile station, which has obtained the information on the target base station (or cell) 520 in step S1, reports the information to the home base station 510 that is currently communicating. Examples of the information may include signal strength of the target base station (or cell), cell ID, system frame number (SFN), and the like (step S2).

In step S2, the home base station 510 having obtained the information on the target base station (or cell) 520 from the mobile station 500 may perform the handover of the mobile station 500 to the target base station corresponding to the cell ID. The resource is queried to the target base station (or cell) 520 (step S3).

The target base station (or cell) 520 receives the handover query from the home base station 510 and notifies the home base station 510 when there is available radio resource. At this time, the handover time (SFN number) may be informed (step S4).

The home base station 510 receiving the response to the resource statement gives a handover instruction to the mobile station 500. At this time, the system frame number (SFN) indicating the handover time can be informed to the mobile station (step S5).

The mobile station receiving the handover indication from the home base station 510 transmits a handover preamble to the target base station (or cell) 520 at the handover time (SFN) (step S6).

The target base station (or cell) 520 allocates a resource for data communication after successfully receiving the preamble transmitted by the mobile station (step S7).

The mobile station to which the resource has been allocated has completed the Inter RAT handover by making a call or communication with the target base station (or cell) 520 using the allocated radio resource (step S8).

FIG. 6 is a diagram illustrating a forward link frame including SCH / P-BCH that supports measurement of inter-RAT handover between different radio access technologies according to an embodiment of the present invention.

One radio frame (10 msec) of the LTE system consists of 10 subframes, and each subframe consists of two slots. SCH and P-BCH are transmitted only in dual subframe 0 and subframe 5.

In addition, the SCH and the P-BCH are transmitted using different OFDM symbols. As mentioned above, the SCH includes information necessary for the mobile station to acquire a 10 msec frame boundary and a cell identifier, and the P-BCH includes system bandwidth, system timing, antenna information, and the like.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a diagram illustrating handover between different radio access technologies according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a frame including a transmission gap of a conventional GSM or WCDMA system.

3 is a diagram illustrating a P-BCH structure implemented when handover between different radio access technologies is not considered.

4 is a diagram illustrating a P-BCH structure implemented when considering handover between different radio access technologies according to an embodiment of the present invention.

5 is a flowchart illustrating a handover procedure between different radio access technologies according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a forward link frame including SCH / P-BCH that supports measurement of inter-RAT handover between different radio access technologies according to an embodiment of the present invention.

Claims (10)

delete In the forward sync signal transmission method for handover between wireless communication systems using different radio access technologies, Generating, by a base station existing on a wireless communication system to which a mobile station is to move, a frame including two or more Primary-Broadcasting Channels (P-BCHs) including the wireless communication system frame number within one frame period; And Transmitting the frame over a forward link; 2 or more P-BCHs included in one frame period of the frame have the same system frame number. In the forward sync signal transmission method for handover between wireless communication systems using different radio access technologies, Generating, by a base station existing on a wireless communication system to which a mobile station is to move, a frame including two or more Primary-Broadcasting Channels (P-BCHs) including the wireless communication system frame number within one frame period; And Transmitting the frame over a forward link; The P-BCH includes system information on the bandwidth and the number of antennas of the wireless communication system, and the same method in the two or more P-BCH included in one frame period. In the forward sync signal transmission method for handover between wireless communication systems using different radio access technologies, Generating, by a base station existing on a wireless communication system to which a mobile station is to move, a frame including two or more Primary-Broadcasting Channels (P-BCHs) including the wireless communication system frame number within one frame period; And Transmitting the frame over a forward link; And the P-BCH is self decodable within a transmission gap of a wireless communication system with which the mobile station is currently communicating. P-BCH (Primary-Broadcasting Channel) including a system frame number for handover between wireless communication systems using different radio access technologies using a forward sync signal composed of two or more frames within one frame period In the handover method, (a) Measuring cell ID and signal strength of the target base station by using the frame of the target base station of the wireless communication system to be moved within the transmission gap of the home base station of the wireless communication system with which the mobile station is currently communicating Demodulating the P-BCH included in the frame to obtain a wireless communication system frame number including the target base station; (b) requesting a handover of the mobile station to a target base station corresponding to the cell ID; (c) transmitting, by the target base station, a system frame number indicating a handover time point to the mobile station in response to the handover request; And (d) allocating resources for communication with the mobile station by the target base station at the time of handover; handover method between wireless communication systems using different radio access technologies. The method of claim 5, wherein step (a) Primary-Synchronous CHannel (P-SCH) 2 included in a frame of a target base station of a wireless communication system to be moved within a transmission gap of a wireless communication system to which the mobile station is currently communicating. Wireless using different radio access technologies, characterized in that the cell ID and signal strength of the target base station are measured by using a secondary-synchronous channel (S-SCH) and a pilot signal (Reference Signal, RS) Handover method between communication systems. The method of claim 5, wherein step (a) P-BCH included in the frame is demodulated to obtain system information about the frame number of the wireless communication system including the target base station and the bandwidth and the number of antennas of the wireless communication system. Handover method between wireless communication systems. The method of claim 5, wherein step (b) Transmitting a cell ID of the target base station, a signal strength, and a frame number of a wireless communication system including the target base station to the home base station; And Requesting a handover of the mobile station from a target base station corresponding to the cell ID by the home base station; and a handover method between wireless communication systems using different radio access technologies. The method of claim 5, wherein step (c) Receiving, by the home base station, a system frame number indicating a handover time point to the mobile station in response to the handover request; And And transmitting to the home base station a handover instruction for the target base station and the system frame number to the mobile station. The method of claim 5, wherein step (d) Transmitting, by the mobile station, a handover preamble to the target base station at the handover time; And Allocating a resource for communication with the mobile station when the target base station receives the handover preamble; and a handover method between wireless communication systems using different radio access technologies.

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