KR100602026B1 - Hand off method of asynchronous mobile station from asynchronous system to synchronous system - Google Patents

Abstract

The present invention relates to a handoff method between an asynchronous system and a synchronous system of a mobile communication system. In particular, when the asynchronous mobile station is handed off from an asynchronous communication wireless network to a synchronous communication wireless network, A handoff processing method characterized in that the asynchronous mobile station can know the information of the wireless network of the synchronous communication method by using a technique such as provided compressed mode, the method of the present invention is synchronized in the asynchronous system When handoff to the system, the initial search time can be reduced to enable smooth handoff, thereby ensuring the user's mobility.

Mobile communication system, IMT-2000, handoff, synchronous base station, asynchronous base station, compressed mode,

Description

HAND OFF METHOD OF ASYNCHRONOUS MOBILE STATION FROM ASYNCHRONOUS SYSTEM TO SYNCHRONOUS SYSTEM             

1A-D is a diagram illustrating an interworking structure of a mobile station, a wireless network, and a core network of an IMT-2000 system;

2 is an overall interworking structure diagram when the core network of the IMT-2000 system is an ANSI-41 network;

3 is a diagram illustrating a cell configuration of a synchronous base station and an asynchronous base station in a mobile communication system;

4 is a flowchart of a handoff processing method from an asynchronous system to a synchronous system according to the present invention;

5 is a view illustrating a compressed mode transmission method that can be used when handing off from an asynchronous base station to a synchronous base station in the present invention;

6 is a handoff call flow implementing the handoff processing method from the asynchronous system to the synchronous system according to the present invention.

Explanation of symbols on the main parts of the drawings

       10; Synchronous base station cell 100; Synchronous base station

       20, 21, 22, 23, 24: Asynchronous base station cell

       30, 31, 32, 33, 34; Asynchronous base station 200; Mobile station

The present invention relates to a base station handoff method in a mobile communication system, and more particularly, in the IMT-2000 communication system, when a mobile station of an asynchronous communication method moves from an asynchronous wireless network to a synchronous wireless network, etc. The present invention relates to a method for processing a handoff of an asynchronous mobile station from an asynchronous system to a synchronous system by enabling information in a synchronous system to be obtained by using the synchronous system.

The mobile communication service has developed into the first generation method based on analog technology in the 1980s and the second generation method based on digital technology in the 1990s, and the non-telephone various types beyond the conventional voice-oriented services in the second generation method. Service areas are expanding to services and data transmission services. On the other hand, according to the rapid increase of users, the expansion of activity range, personalization, multimedia, etc., it is possible to move between users / mobile stations and to transmit and receive various types of information between global scale networks. In order to cope with the demand for information and communication in the future, standardization work related to IMT-2000 (International Mobile Telecommunication), which is a third generation mobile communication system, is being carried out.

The mobile communication system divides the entire service area into cells, which are small service areas, in order to use limited frequency resources more efficiently. At this time, the user is provided with the current service to guarantee the mobility of the user. A handoff is performed to take over the call channel between the mobile station and the base station so that the call can be maintained continuously even if it leaves the cell. In detail, handoff allows a mobile station to be allocated a new call channel from a mobile base station when the mobile station moves to another cell. There are two types of handoffs: soft handoff and hard handoff. .

On the other hand, the mobile communication system is largely divided into a synchronous system and an asynchronous system. Among them, the synchronous system is a system in which each subsystem communicates synchronously according to the master clock from the GPS. It is a communication system that does not use a master clock. The synchronous mobile communication system herein refers to a second generation synchronous system currently being serviced or a third generation synchronous system (synchronous IMT-2000) to be commercialized in the future, and an asynchronous mobile communication system refers to a third generation asynchronous system (asynchronous IMT-2000). do.

In one example, the IMT-2000 system has four types of interworking structures as shown in FIGS. 1A-D according to a network deployment situation. That is, the IMT-2000 system includes a synchronous mobile station (terminal), a synchronous wireless network and an ANSI-41 network interworking structure as shown in FIG. 1a, a synchronous mobile station (terminal) as shown in FIG. 1b, a synchronous wireless network and a GSM-MAP network interworking structure, It has an asynchronous mobile station, asynchronous wireless network and GSM-MAP network interworking structure as shown in Figure 1c and an asynchronous mobile station, asynchronous wireless network and ANSI-41 network interworking structure as shown in Figure 1d. In this interworking structure, the mobile station has both CC (Call Control) and MM (Mobility Management) protocol entities for ANSI-41 and GSM-MAP networks, and selects CC and MM protocol entities in the same manner according to the core network type. Use it.

In the interworking structure, if the core network of the IMT-2000 system is an ANSI-41 core network, referring to the above-described interworking structure with reference to FIG. 2, the ANSI-41 core network includes a synchronous wireless network (a second generation wireless network and a third network). Generation wireless network), asynchronous wireless network, and analog wireless network can be interlocked.

As in the above-described example, when the synchronous wireless network and the asynchronous wireless network are interworked, a handoff between the synchronous system and the asynchronous system is required to increase efficiency.

3 is a diagram illustrating a cell configuration of a synchronous base station and an asynchronous base station when the synchronous system and the asynchronous system are being serviced in the same region.

 As shown in FIG. 3, since the third generation asynchronous system cannot initially service in all regions, the third generation asynchronous system will be adjacent to or included in the synchronous system currently being serviced. That is, the asynchronous base stations 30, 31, 32, 33, 34 having certain cells 20, 21, 22, 23, 24 are located in the cell 10 of the synchronous base station 100.

In this situation, when the mobile station 200 supporting both of the asynchronous / synchronous modes receives service from the asynchronous base stations 30, 31, 32, 33, and 34, and moves to the boundary of the synchronous base station 100 in which the asynchronous base station does not exist. The mobile station 200 does not have asynchronous base stations 30, 31, 32, 34 to hand off, and the mobile station 200 needs to handoff from the asynchronous base station 33 to the synchronous base station 100.

As described above, when the asynchronous mobile station performs handoff from the asynchronous system to the synchronous system, the handoff process follows the handoff process of the asynchronous system. However, since the handoff process of the asynchronous system does not take into account the handoff process with the synchronous system, a handoff process may occur during handoff between the asynchronous system and the synchronous system. In addition, in the case of a synchronous system, all synchronous systems are synchronized about a certain start time. The mobile station thus obtains information on the synchronization start time of all synchronization systems to synchronize with the synchronization system. However, unlike asynchronous systems, the synchronization of all asynchronous systems does not coincide around any start time. Therefore, when the asynchronous mobile station handoffs from the asynchronous system to the synchronous system, the synchronization information, frame information, etc. of the synchronous system are not known, and thus a problem occurs that the handoff from the asynchronous system to the synchronous system is impossible.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems of the prior art, and to enable the asynchronous mobile station to know the information of the synchronous system at the time of handoff from the asynchronous system to the synchronous system, thereby enabling smooth handoff from the asynchronous system to the synchronous system. To provide a handoff processing method from an asynchronous system to a synchronous system.

That is, one aspect of the present invention provides a handoff process from an asynchronous system to a synchronous system,

A first step in which the asynchronous base station sends a neighbor list of neighboring synchronous base stations to the mobile station at the beginning of the network so that the mobile station stores such information;

A second step of searching for an asynchronous wireless network to determine whether a suitable asynchronous wireless network exists when a handoff is required;

A third step of sending a message to the mobile station by the asynchronous base station to find a synchronous base station if there is no suitable asynchronous wireless network as a result of the determination in the second step;

A fourth step in which the mobile station receives a message from the asynchronous base station and sends an acknowledgment message for it;

The mobile station receiving the message from the asynchronous base station of the third stage monitors and processes the information of the common channel (pilot channel, base station offset, synchronous channel superframe timing) that is always broadcast from the base station of the synchronous wireless network, which is most suitable for handoff. A fifth step of selecting a synchronous base station; And

And a sixth step of transmitting the index value of the synchronous base station selected in the fifth step to the asynchronous base station, thereby causing the mobile station to perform a handoff to the determined synchronous base station. It is to provide a handoff processing method of.

According to another aspect of the present invention, when an asynchronous mobile station serving as an asynchronous base station performs handoff to a synchronous base station, pilot synchronization, base station offset, super frame timing of a synchronous channel, and long code state of a traffic channel are provided. It is possible to obtain information of necessary synchronization base station such as Long Code State during the idle period of the mobile station's compressed mode, thereby minimizing call disconnection time due to initial discovery in handoff performance. .

Hereinafter, a handoff processing method between a synchronous system and an asynchronous system in a mobile communication system according to the present invention will be described in detail.

The present invention recognizes a problem that handoff is not possible from an asynchronous system to a synchronous system due to a problem in the handoff process or a problem of information acquisition of the synchronous system when the asynchronous system and the synchronous system are serviced in the same area. In order to perform a smooth handoff of the asynchronous mobile station to the synchronous wireless network, an additional common channel is always provided to the base station of the synchronous wireless network to always broadcast a pilot channel, base station offset, and super frame timing of the synchronous channel.

4 is a flowchart of a handoff processing method from an asynchronous system to a synchronous system according to the present invention.

In the method of the present invention, the asynchronous base station sends a neighbor list of neighboring synchronous base stations to the mobile station at the beginning of the network to store such information (S1). At this time, the neighbor set is sent as an RRC (Radio Resource Control) message. Since the RRC message is not defined previously, it is necessary to newly define or modify an existing message.

Subsequently, the asynchronous base station currently in communication with the mobile station searches for an adjacent asynchronous wireless network according to the information received from the mobile station and determines whether there is an appropriate asynchronous base station to hand off (S2).

As a result of the determination of the previous step, if there is an asynchronous base station to be handed off among the adjacent asynchronous base stations, handoff is performed to the corresponding asynchronous base station (S10).

However, when there are no asynchronous base stations to hand off among the adjacent asynchronous base stations in the second step S2, the asynchronous base station transmits a message to the mobile station to find the synchronous base station as an RRC message (S3). Since these RRC messages are not defined previously, they need to be newly defined or modified to use existing messages. In this step, the mobile station operates in the compressed mode to retrieve information about the synchronous base station.

FIG. 5 is a diagram illustrating a compressed mode of an asynchronous terminal, and illustrates a compressed mode transmission method when a handoff is performed from an asynchronous base station to a synchronous base station.

As shown in FIG. 5, in the compressed mode scheme, a transmission gap is formed between frames without using the entire slot for data transmission. In the present invention, an idle period (where the data is not transmitted in this way) During the idle period, information on the sync base station required for handoff is obtained by using a common channel broadcasted from the sync base station. Specifically, the synchronous base station transmits zero offset, long code state, and synchronous channel super frame timing information to the mobile station through the common channel.

The mobile station receiving the message in the third step S3 sends an acknowledgment message for the message as an RRC message to the asynchronous base station (S4). Since these RRC messages are not defined previously, they need to be newly defined or modified to use existing messages.

Upon receiving this message, the mobile station monitors and processes information on the common channel that is always broadcast from the base station of the synchronous radio network to set the zero offset pilot PN sequence timing, the maximum pilot signal of the synchronous base station, and obtain handoff after frame synchronization. The most suitable synchronization base station is selected (S5). In the present invention, the selection criteria of the base station suitable for handoff is not particularly limited. For example, after obtaining zero offset timing information, the mobile station searches for only the corresponding pilot offset from the adjacent base station list and selects a base station to handoff to the maximum value of the pilot signal. You can decide.

Finally, the mobile station sends the index of the synchronous base station best suited for handoff to the asynchronous base station, and the asynchronous base station sends a handoff command based thereon to perform the handoff to the determined synchronous base station. At this time, the index value of the asynchronous base station is in the form of RRC (Radio Resource Control). Since the RRC message is not previously defined, it is necessary to newly define or modify an existing message. Specifically, when performing handoff, a source asynchronous base station transmits a handoff required message to the switching center, and the switching center transmits a handoff request signal to the synchronous base station. to a synchronous base station. Upon receipt of the handoff request signal, the synchronous base station allocates the appropriate channel to take over the call.

6 illustrates an example of a handoff call flow implementing a handoff processing method from an asynchronous system to a synchronous system according to the present invention. Detailed description is omitted to avoid duplication.

A method for processing handoff of an asynchronous mobile station from an asynchronous system to a synchronous system of the present invention is a mobile communication system having an asynchronous mobile station, an asynchronous wireless network, and a synchronous wireless network. In spite of using the method, it is possible to provide a smooth handoff, thereby realizing mobile communication in a true sense.

Claims (9)

In performing the handoff process from the asynchronous system to the synchronous system, A first step in which the asynchronous base station sends a neighbor list of neighboring synchronous base stations to the mobile station at the beginning of the network so that the mobile station stores such information; A second step of searching for an asynchronous wireless network to determine whether a suitable asynchronous wireless network exists when a handoff is required; A third step of sending a message to the mobile station by the asynchronous base station to find a synchronous base station if there is no suitable asynchronous wireless network as a result of the determination in the second step; A fourth step in which the mobile station receives a message from the asynchronous base station and sends an acknowledgment message for it; A fifth step of the mobile station receiving the message from the asynchronous base station of the third step selecting and selecting the most suitable synchronous base station for handoff by monitoring and processing information of the common channel which is always broadcasted by the base station of the synchronous communication type wireless network; And And a sixth step of transmitting the index value of the synchronous base station selected in the fifth step to the asynchronous base station, thereby causing the mobile station to perform a handoff to the determined synchronous base station. How to handle handoffs. 2. The handoff process from an asynchronous system to a synchronous system according to claim 1, wherein the third step includes the step of acquiring information about the synchronous base station by the asynchronous mobile station using the compressed mode. Way. 3. The method of claim 1 or 2, wherein the information transmitted from the synchronization base station to the mobile station through the common channel in the sixth step includes synchronization base station timing, synchronization channel superframe timing, long code state, and synchronization channel. The handoff processing method from the asynchronous system to the synchronous system, characterized in that the frame timing information. The method according to claim 1 or 2, wherein the fifth step comprises setting a zero offset pilot PN sequence timing transmitted by the synchronization base station through a common channel, a maximum pilot signal of the synchronization base station, and frame synchronization. A method of processing handoff from an asynchronous system to a synchronous system, characterized in that it is a process of selecting a synchronous base station best suited for handoff after the acquisition. 5. The method of claim 4, wherein after the mobile station acquires zero offset timing information in step 6, the mobile station searches for only the corresponding pilot offset from the neighboring base station list to determine the base station to be handed off to the maximum value of the pilot signal. How to handle handoff to synchronous system. The asynchronous system to a synchronous system according to claim 1 or 2, wherein the first step is a step of sending a neighbor set of asynchronous base station neighboring synchronous base stations from the asynchronous base station to the mobile station in an RRC message (Radio Resource Message). How to handle handoff. 3. The method of claim 1 or 2, wherein the third step is a step in which the asynchronous base station delivers the message to the mobile station via an RRC message. 3. The method of claim 1 or 2, wherein the fourth step is a process of sending an acknowledgment message using an RRC message. The asynchronous system to a synchronous system according to claim 1 or 2, wherein the sixth step is a process of transmitting an index value of a synchronous base station most suitable for handoff by the asynchronous mobile station to the asynchronous base station in the form of an RRC message. How to handle handoff.

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