KR0123398B1 - Control method of hard-hand off in cdma msc - Google Patents

Abstract

The control method of hard-handoff of a CDMA MSC including a base station control unit(BSC)(01); the MSC(02) for performing circuit switching service and location registration, handoff, paging and so on; and a home location resister(HLR)(03) for permanently storing and managing mobile subscriber information, comprises the steps of: (203-213)if a handoff type corresponds to the handoff between base stations within the MSC, processing the handoff; (303-319)if the handoff type corresponds to a handoff forward, processing the handoff; (403-418)if the handoff type corresponds to a handoff backward, processing the handoff; and (503-524)if the handoff type corresponds to the handoff to a second MSC, processing the handoff.

Description

Hard Handoff Control Method in CDMA Mobile Switching System

1 is a simplified structural diagram of a mobile communication switch to which the present invention is applied.

2 is an exemplary configuration diagram of a general mobile communication system network for explaining the present invention.

3 is a flow chart of the procedure of Inter-BSC Handoff.

4 is a process flow diagram of handoff forward.

5 is a process flow diagram of Handoff Backward.

6 is a flow chart of the handoff to the third system with the smallest path.

FIG. 7 is a diagram showing a call path before handoff occurs. FIG.

8 is a diagram showing a path of a call after issuing a handoff.

* Explanation of symbols for main parts of the drawings

01: Base station controller (BSC) 02: Mobile communication switch (MSC)

03: Hum location register (HLR) 04: ASS

05: INS 06: CCS

11: starting base station 12: starting mobile communication exchange

21: service base station 22: service mobile communication switch

31: target base station 32: target mobile communication exchange

The present invention relates to a method for controlling hard handoff in a CDMA mobile communication switch, and more particularly, to a hard handoff control method for enabling the shortest distance to be set in a multi-stage hard handoff occurrence.

In general, handoff is a phenomenon caused by mobility of a mobile subscriber. When a signal quality falls below a certain level by measuring signal strength at a base station or a mobile station at all times, a new call channel is secured to transfer an ongoing call to a new channel. Means.

Since the accuracy of the handoff described above is an important factor in determining the call quality, the mobile communication exchange requires the allocation of a handoff call to a new base station in order to secure a call path that can be maintained without being disconnected. A system is designed so that a call can be transferred to a base station that manages a moving area of a mobile station without affecting an ongoing call of a mobile subscriber by using a road, and a control method for controlling handoff has been provided or developed.

In addition, in the case where the handoff of the mobile station is made in the area of another exchange, the relay line must also be configured separately.

Referring to the conventional switching channel control method proposed as a control method of the handoff described above, if a handoff occurs due to the movement of a mobile station in a call path connection method used in an analog mobile communication system, the existing channel is changed to a new one. There has been a problem that the user is not able to talk for a time enough to be recognized by the subscriber in a way that is disconnected before the connection to the call is made, causing a considerable inconvenience for the user.

In order to solve the problems caused in the conventional switching call path control method as described above, the newly-combined combination-type call path connection method is a conventionally configured call after the handover process is finished. After the connection to the new call is completed, the existing call path and the newly formed call path are simultaneously connected in the form of being disconnected, thereby maintaining a good call state.

For example, a mobile communication system employing the above-described combined call path connection method, although the European Global System for Mobile communication (GSM) method uses a call mixer circuit for the call path connection method, There is a problem that wastes system resources available for conference calls for off.

In addition, the CDMA system has the advantage of having the best call quality by connecting the better one of the existing and new ones for a certain time by performing soft handoff processing. In case of use, the problem is that soft handoff processing is impossible and hard handoff processing is required.

In addition, in the CDMA system, a problem arises in that the transmission and reception of a telegram proceeds sequentially through a multi-stage switch when a handoff-forward occurs in addition to the handoff in the case of the heterogeneous frequency described above.

Briefly referring to the above-mentioned problems caused by the handoff-forward phenomenon, the mobile communication exchange controls the hard handoff when the handoff occurs between base stations controlled by different exchanges. In the CDMA system, the secondary handoff that occurs when the mobile subscriber moves to another exchange after the primary handoff of the exchange period for handoff-forward processing is performed. There is a system using a handoff to third form.

In such a case, in order to perform additional service that occurs after the handoff, the corresponding information is provided from the visitor location register (VLR) of the anchor MSC that set the initial call at the service exchange, or the service is provided at the origin exchange. If a mobile subscriber moves by using a plurality of cell areas managed by arbitrary exchanges, the information passes through multiple exchanges at the time of information transmission, thereby causing a waste of efficiency and reduced efficiency of the entire system. There is.

An object of the present invention for solving the above problems can be changed to a new call without affecting the switch of the other subscriber, without deterioration of the call state, the exclusion of the intermediate exchange when the continuous handoff must be performed The present invention provides a hard handoff control method in a mobile communication system employing a CDMA scheme that minimizes a call path by processing a handoff between a first switch to which a call is set and a final switch that will accept a handoff.

In order to achieve the above object, a feature of the present invention is to divide an area for providing a wireless call service into a predetermined number of exchange jurisdiction areas, and re-partition the exchange jurisdiction area into a predetermined number of base station jurisdictions. Switch in response to mobile station handoff request for moving multiple exchange jurisdictions in mobile communication system applying code division multiple access method for allocating call channel of mobile station moving each cell area A method for controlling hard handoff in a mobile station, comprising: receiving a handoff request message generated by moving a mobile station from an area where a communication channel is formed to an area of a second base station jurisdiction through a corresponding base station; A first exchange manages a destination cell in the handoff request message. A first step of retrieving the unique number of the ventilation (destination exchange number); and if the destination exchange number retrieved in the first step is the same as the unique number of its own exchange, the mobile station has a jurisdiction of any first base station in the first exchange area. The second process of determining that the second base station to move to another jurisdiction area and converts the call channel of the mobile station to the jurisdiction of the second base station, and the destination exchange number retrieved in the first process is the unique number of its own exchange. Is different from the third process of determining where the exchange area (originating exchange) in which the mobile station opened the first channel is located, and when the first exchange itself is determined as the originating exchange in the third process, the call channel of the mobile station is determined. In the fourth process of switching to the second exchange jurisdiction and the third process, it is determined that the first exchange itself is not the originating exchange. A fifth step of comparing the destination exchange number and the originating exchange number; and a sixth process of converting the call channel of the mobile station to the originating exchange jurisdiction if the destination exchange number and the originating exchange number are determined to be the same in the fifth process. And a seventh step of converting the communication channel of the mobile station into the destination exchange jurisdiction by directly connecting the destination exchange number and the internal exchange path of the origin exchange period when it is determined that the destination exchange number and the origin exchange number are different in the fifth process. To include the process.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a structural diagram of a digital cellular mobile communication system to which the present invention is applied, and includes a plurality of base station control devices (BSCs) (01,01a, 01b) and location registration, paging and A mobile service switching center (MSC) 02 which performs a function of starting a simple handoff or a hard handoff process during the exchange period, and performs the same function as the mobile communication switch 02; A service mobile communication switch (07) for performing handoff-forward, handoff-backward, and handoff functions to a third exchange through telegram exchange with the mobile communication switch (02), and the starting mobile communication switch (02). At the request of the mobile communication exchange 08 which actually handles the handoff to the third exchange and the home location register which permanently stores / manages the subscriber information. gister: HLR) (03).

The mobile communication switch having the above configuration has an access switching subsystem (ASS) (04,04a, 04b), an interconnection network subsystem (INS) (05,05a, 05b), and a central control subsystem (CCS) (06,06a, 06b). It consists of a subsystem of.

At this time, each of the mobile communication exchanges (02, 07, 08) is expressed as a starting point, a service, and an object, depending on the case, the corresponding exchange will vary.

In other words, the base mobile communication exchange is an exchange in which an arbitrary mobile station maintains an initial communication path.

In addition, the target mobile communication exchange refers to the MSC as the target mobile communication exchange during handoff processing when the MSC managing the target cell is another MSC in the process of changing the location area while the mobile station is moving. The MSC is referred to as a service mobile communication exchange.

That is, the service mobile communication exchange refers to an exchange that manages a cell in which a mobile station is currently receiving a call service.

Therefore, in the above-described configuration, the mobile station has been described under the assumption that the mobile station has moved from the first base international language device 01 to the third base international language device 01b.

In addition, only three connection configurations are used during the exchange period.

Among the components constituting the switches 02, 07, and 08 divided into the above functions, the ASS (04, 04a, 04b) includes a subscriber and a relay line matching device, a time switch, various signaling devices, and the like. The call processing function and its own maintenance are performed, and the INS (05, 05a, 05b) performs the centralized functions such as number translation, route control function, and space switch connection among the call processing functions.

In addition, the CCS (06, 06a, 06b) performs system-level operation management, maintenance, billing and statistics, and stores / manages the subscriber registration process and the subscriber information.

In particular, ASS is not shown, but consists of ASS-M and ASS-T, the Access Switching Subsystem for Mobile Subscriber (ASS-M) performs a call processing function, handoff and mobility management function for the mobile subscriber, ASS-T (Access Switching SubsyStem for Trunk) performs call processing function for relay line by matching with mobile communication switch and fixed network switch.

Referring to the accompanying drawings, a control method of a hard handoff according to the present invention in a CDMA communication network having the above configuration is as follows.

2 is an exemplary configuration diagram of a general mobile communication system for explaining the present invention. When the mobile station requests a handoff, the mobile station maintains the current path while measuring the electric field strength of the neighboring cell received at the current location. It is generated for a movement request by a call to a cell having a field strength greater than a predetermined value compared to the field strength of the current cell compared to the field strength of the cell.

Therefore, when the mobile station requires a handoff, the handoff can be classified into about five types. For each case, a brief handoff control operation according to the present invention is as follows.

[Case 1]

The handoff request generated when the mobile station in the first cell area cell 11 of the cell area in the first base station 10a moves to the second cell area cell 12 is transmitted within the service area managed by the base station itself. Since it is a cell-to-cell movement, the first base station 10a performs processing by itself, and operates so that the first switch 100A does not perform a control operation according to the occurrence of a handoff.

This is often referred to as soft handoff and is not considered in the present invention.

[Case 2]

Any cell in the cell area in the first base station 10a, i.e., a mobile station that is in a call in the 1-3 cell areas cell 11 to cell 13, is a cell area in the second base station 10b, for example, a fourth cell. When moving to the area cell 21, the first base station 10a transmits its handoff request received from the mobile station to the first exchange 100A because the mobile station leaves its service area.

At this time, the first switch 100A searches for a target cell number to which the corresponding mobile station is to move in the handoff request information input from the first base station 10a.

In general, a cell number is composed of a network number, an exchange number, a base station number, and a cell identification number (ie, cell number = network number + exchange number + base station number + cell identification number).

Since the switch number is the same as its own number, the first switch 100A searching for the target cell number configured as described above determines the handoff time between base stations in the same exchange service area and processes the handoff time as an inter-BSC handoff. box.

[Case 3]

When the mobile station moves from the fifth cell area (cell 22) where the current path is formed to the seventh cell area (cell 31), i.e., the service of the second exchange 100B in the service area of the first exchange 100A. When moving to the area, the handoff request generated at the mobile station is transmitted to the first exchange 100A through the second base station 10b managing the fifth cell area cell 22.

The first switch (100A) is a target cell (ie, target cell) to which the mobile station intends to move in the received handoff request information. The number of the seventh cell area (cell 31) is searched, and it is determined that the handoff type is handoff period, that is, handoff-forward, because the switch number is different from its own number.

Accordingly, the first exchange 100A requests the second exchange 100B for handoff of the mobile station.

[Case 4]

Handoff by any mobile station moving from the service area of the first exchange 100A to the service area of the second exchange 100B, i.e., from the fifth cell area cell 22 to the seventh cell area cell 31. The mobile station again switches the seventh cell area (cell 31) to the fifth cell area (cell 22) or any service cell area of the first exchanger 100A during the call while forming a transfer to a forward type call. In step S, the handoff request generated by the mobile station is transmitted to the second exchange 100B through the third base station 10c managing the seventh cell area cell 31.

The second switch 100B searches for a target cell, ie, a fifth cell region cell 22, to which the mobile station intends to move, from the received handoff request information.

At this time, the second exchange 100B already recognizes the originating exchange number at the request of the handoff-forward of the mobile station, and the exchange number is different from its own number and is identical to the exchange number of the originating exchange already recognized. Therefore, it is determined that the handoff type is handoff-backward during the handoff period during the exchange.

Accordingly, the second exchange 100B requests the base exchange, that is, the first exchange 100A, to handoff the mobile station.

[Case 5]

In this case, if the handoff-forward as shown in 3 is repeated so that a plurality of exchanges do not overlap, that is, the mobile station starts a call in the service area of the first exchange 100A and then moves during a call, the service area of the second exchange 100B. When entering, the first exchanger 100A becomes a starting exchanger and the second exchanger 100B becomes a target exchanger to perform a handoff-forward operation.

Subsequently, when the mobile station continuously moves again from the service area of the second exchange 100B to enter the service area of the third exchange 100C, the second exchange 100B becomes the service exchange and becomes the third exchange. 100C becomes the target exchange and makes a second handoff-forward operation.

When the above handoff-forward process occurs a plurality of times in succession, in the second exchange 100B, the mobile station is in a handoff request generated by the mobile station entering the service area of the third exchange 100C. The exchange number is searched for in the number of the target cell to be moved.

At this time, the second exchange 100B already recognizes the number of the originating exchange at the request of the handoff-forward of the mobile station, and the exchange number is different from its own unique number and is already recognized with the exchange number of the originating exchange. Since the handoff type is different, it is determined that the handoff type is the handoff to the third exchange during the handoff period.

In the case of the handoff type as described above, the form 2 to case 5 is a hard handoff to be solved herein.

In addition, the form of each handoff may actually occur unspecified depending on the situation, and furthermore, in case of handoff-forward or backward generation, an inter-base station or inter-cell handoff may occur and a specific exchange is fixed to origin, service and destination. It can be seen that it is not.

With reference to the accompanying drawings, the handoff control method according to the present invention for each case as described above in detail as follows.

FIG. 3 is a flow chart of a handoff occurring in case of the foregoing case 2, i.e., between base stations within one exchange service area.

When the mobile station changes the location area while the mobile station is busy, that is, when a handoff occurs, the exchange (MSCi) 22 that receives the handoff request 201 message via the base station (BSCI) 21 receives the hand. In the case of handoff between base stations in the exchange (203) by analyzing the off type (202), the internal call path of the exchange is established using an ASS-M front end connector (formed by looping back the time slot of the time switch). 204 so that the change of the timeslot connected with the base station does not affect the space switch or the time switch with the other subscriber.

The exchange sends a handoff request 205 message to the base station (BSCi2) 23 to perform the handoff.

The exchange (MSCi2) 22 having received the handoff response 206 message from the base station (BSCi2) 23 transmits a Perform Handoff (207) message to the target base station (BSCi2) 23 if the traffic channel can be established. A new call path is constructed 208 to send a handoff command 209 message to the serving base station.

When the exchange receives the handoff complete 210 message from the target base station (BSCi2) 23, the exchange transfers the old call path to the new call path (211).

The exchange ends the handoff when the traffic channel multiplication request 212 is made to the base station (BSCi2) 23 that has provided the previous service and the response 213 message is received.

4 shows the main message flow diagram for case 3 described above, i.e., the handoff forward procedure and the network element.

Handoff forward occurs when a mobile station moves to another exchange area that will accept a handoff from an exchange providing existing service during a call.

In an exchange (NSCi) 22 that has received a handoff request 301 message from a base station (BSCi) 21, the exchange (MSCi) 22 in which the handoff type 302 is currently serving is the originating exchange in which an initial call is established. (Anchor MSC) performs a handoff forward 303 procedure.

If the handoff that has occurred is the first handoff, the exchange internal call path is first established (304).

However, if there is a handoff between base stations before, it is omitted.

After occupying 305 a trunk with a target exchange (MSCj) 32 to accept a handoff, a resource occupancy request 306 message is sent to the target exchange (MSCj) 32 to accept a handoff.

The target exchange makes a handoff request 307 to the target base station (BSCj) 31 that will accept the handoff and receives a handoff response 308 message.

The exchange (MSCj) 32 receiving this message transmits a handoff 309 message to the base station (BSCj) 31 if it is able to establish a traffic channel in the message, and establishes a call path with the base station (310). After that, the resource exchange request response message is transmitted to the service exchange.

The exchange (MSCi) 22 that has received the resource occupancy request response 311 message establishes 312 a call path with the target exchange (MSCj) 32, and hands the base station (BSCi) 21 that requested handoff. Send an off command 313 message.

When the target exchange (MSCj) 32 receives the handoff completion 314 message from the base station (BSCj) 31, it transmits a radio channel occupation notification (315) message to the serving exchange (MSCi) 22 and the base station. (BSCj) 31 connects the call path with (316).

The service switch (MSCi) 22 switches 317 from the existing channel to the new channel with the target switch (MSCj) 32, and then sends a traffic channel multiple request (318) message to the base station (BSCi) 21. The handoff forward procedure ends upon sending and receiving a complete 319 message.

FIG. 5 is a message flow diagram between the network element and the procedure for case 4 described above, that is, a handoff backward (Handoff Backword).

The handoff backward is the switch (MSCi) 31 immediately before the type 402 of the handoff request 401 message received from the base station (BSCj) 31 after the handoff forward is performed to move to the current position. (403).

The exchange (MSCj) 32 sends a handoff backward request 404 message to the handoff target exchange (MSCi) 22, and then the counter exchange (MSCi) 22 performs a handoff at the base station BSCi. When the handoff request 405 is received and the response 406 is received, the handoff operation 407 is transmitted to the base station (BSCi) 21, and a call path with the base station is established. 408).

The MSCj 32 receiving the handoff backward response 409 message from the MSCi 22 sends a handoff command 410 message to the BSCj 22 requesting the handoff. send.

When the target exchange (MSCi) 22 receives the handoff complete 411 message from the base station (BSCi) 21, it connects to a new channel (412) and exchange (MSCj) 32 that previously provided a call service. Forwards the resource release request 413 message.

The exchange (MSCj) 32 receiving this message recovers the trunk of the switching period (414), recovers the call path with the existing base station (BSCj) 31 (415), and then requests the traffic channel recovery request ( 416) Send the message.

After transmitting the resource release request response 417 message to the target exchange (MSCi) 22, the handoff backward procedure is terminated when receiving the traffic channel recovery complete 418 message from the base station (BSCj) 31.

6 is a flow chart between the network elements and the procedure for handoff to the third exchange for case 5 described above.

If the type 502 of the handoff request 501 received from the base station 31 after the handoff of the exchange period is moved to another exchange jurisdiction (503), hand to the third system. The off 504 message is sent to the originating exchange (MSCi) 22 where the call was originally established.

The origin exchange switch (MSCi) 22 seizes the trunk with the target exchange (MSCk) 42 to perform the handoff (505), and then sends a resource occupancy request (506) message, and the target exchange (MSCk) 42 Transmits a handoff request (507) message to the base station (BSCk) 41 after the handoff request 507 is transmitted to the base station (BSCk) 41 to perform the handoff. do.

Thereafter, the resource exchange request response 510 message is transmitted to the origin exchange switch (MSCi) 22, and a new channel is configured (511).

When the target exchange (MSCk) 42 receives the handoff completion 514 message from the base station (BSCk) 41, it waits for a resource release request message from the origin exchange (MSCi) 22.

When the target exchange (MSCk) 42 receives the handoff complete 514 message from the base station (BSCk) 41, it transmits a radio occupancy channel notification (515) message to the originating exchange (MSCi) 22 and transmits the call. Connect (516).

The originating exchange (MSCi) 22 transfers the call from the exchange (MSCj) 32 that provided the previous service to the exchange with the new exchange (517), and then releases the resource release request (518) message. The trunk is recovered (519) after transmission to MSCj) 32.

The former service switch (MSCj) 32 recovers the trunk (520) and restores the call path (521), and then sends a traffic channel multiple request (522) message to the base station (MSCj) 31 and the origin exchange (MSCi). Resource release request response (523).

Upon receiving the traffic channel recovery complete 524 message from the base station (BSCj) 341, the handoff procedure to the third exchange ends.

7 is a block diagram of a call of a mobile communication switch before a handoff occurs, which is composed of an originating time switch space switch and an originating time switch between called and receiving subscribers.

8 is a block diagram of a call between incoming and outgoing subscribers after a handoff occurs.

As a front junctor assigned to the time switch of the mobile subscriber A in which the handoff has occurred, the internal route of the exchange is established to maintain the call path with the counterpart B so that the time of the space switch or the counterpart B is maintained. Represents a newly configured currency path without affecting the switch.

Brief description of the shear connector is as follows.

In general, the switch network of the mobile communication exchange has a structure of T-S-T (time switch-space switch-time switch).

The time switch has a predetermined number of time slots provided at a front end connected to a subscriber or a relay line, and has a predetermined number of time slots provided at a rear end connected to the space switch.

Therefore, the shear connector refers to using a loop back of a part of the time slots provided in the front end at any time switch.

According to the present invention carried out as described above, it is possible to change to a new call without affecting the switch of the other subscriber, without deterioration of the call state, and when a continuous handoff needs to be performed, the call is first established without the intermediate exchange. The handoff between the exchange and the final exchange that will accept the handoff has the effect of minimizing the call path.

Claims (6)

After dividing the area providing the wireless call service into a predetermined number of exchange jurisdictions, re-changing the exchange jurisdiction area into a predetermined number of base station jurisdictions, the base station jurisdiction area is divided into a predetermined number of cell areas, and each cell area is divided. A method for controlling hard handoff in an exchange according to a handoff request of a mobile station moving a plurality of exchange jurisdictions in a mobile communication system employing a code division multiple access scheme for allocating a call channel of a mobile station. The first exchange receiving a handoff request message through the base station from the mobile station to any second exchange jurisdiction in which the communication channel is formed is generated. Retrieve the unique number (target exchange number) of the exchange that manages the cell First step; If the number of the destination exchange retrieved in the first step is the same as the unique number of its exchange, it is determined that the mobile station moves from the jurisdiction of any first base station within the area of the first exchange to another jurisdiction of the second base station. Converting a communication channel to the second base station jurisdiction; A third step of determining, if the destination exchange number retrieved in the first step is different from its own exchange number, the exchange area (originating point exchange) in which the mobile station opened the first channel; A fourth step of converting the call channel of the mobile station into the jurisdiction of the second exchange when the first exchange itself is determined as the originating exchange in the third process; A fifth step of comparing the destination exchange number and the originating exchange number if it is determined that the first exchange itself is not the originating exchange in the third process; A sixth step of converting the call channel of the mobile station to the originating exchange jurisdiction area when it is determined in step 5 that the destination exchange number and the originating exchange number are the same; And a seventh step of converting the communication channel of the mobile station into the destination exchange jurisdiction by directly connecting the destination exchange number and the internal exchange path of the origin exchange period when it is determined that the destination exchange number and the origin exchange number are different in the fifth process. Hard handoff control method in a CDMA mobile communication switch comprising a process. The method of claim 1, wherein the second process comprises: a first step of establishing an internal call path in the exchange; Sending a handoff request message to a second base station to perform a handoff at the exchange; If the exchange receiving the hand-operation response message from the second base station is able to establish a traffic channel, it transmits a handoff execution message to the second base station, constructs a new call path, and sends a handoff command message to the serving first base station. Transmitting a third step; A fourth step of, when the exchange receives a handoff complete message from the second base station, transferring the previous call path to the new call path; And a fifth step of terminating the handoff when the exchange makes a request to recover the traffic channel to the first base station which has provided the previous service and receives the response message. Way. The method of claim 1, wherein the fourth process comprises: first setting the internal call path of the exchange when the handoff currently occurring is the first handoff, and omitting it if there is a handoff like the second process before. Step; A second step of, after the originating exchange occupies a trunk with the destination exchange (second exchange) that will accept the handoff, sending a resource occupancy request message to the destination exchange; Receiving, by the destination exchange, a handoff request from the target base station by making a handoff request to a target base station to accept the handoff; If the destination exchange that has received the message in step 3 can establish a traffic channel in the message, it transmits a handoff message to the target base station, establishes a call path with the target base station, and then sends a resource occupancy request response message to the base exchange. Transmitting a fourth step; A fifth step of the base exchange that receives the resource occupancy request response message in the fourth step, establishing a communication path with the destination exchange, and transmitting a handoff command message to the base station which requested the handoff; A sixth step of, when the destination exchange receives the handoff completion message from the target base station, delivering a wireless channel occupancy notification message to the serving base exchange in service and connecting a call path with the target base station; A seventh step in which the base exchange exchanges the traffic channel recovery request message to the base station after the transfer from the existing channel to the new channel with the destination exchange; Hard handoff control method in a CDMA mobile communication switch characterized in that it is salvaged. The method of claim 1, wherein the sixth step transmits a handoff backward request message to a base exchange that is a handoff target, and then the base exchange exchange requests a handoff to a target base station to perform a handoff and receives the response. Transmitting a handoff performance message to the target base station, and constructing a call path with the target base station; A second step in which a service exchange currently in service of a call receiving a handoff backward response message from the originating exchange transmits a handoff command message to a service base station in its jurisdiction requesting a handoff; A third step of, when the originating exchange receives a handoff completion message from the destination base station, connecting a new channel and delivering a resource release request message to a service exchange; A fourth step of the service exchange receiving the message, restoring a trunk of the switching period, restoring a call path with an existing serving base station, and then transmitting a traffic channel recovery request message; And the fifth step in which the handoff backward procedure is terminated when the service exchange sends a resource release request response message to the base exchange and then receives the traffic channel recovery complete message from the service base station. Hard Handoff Control Method in. 2. The method of claim 1, wherein the seventh step comprises: a first step of the service switching station sending a handoff message to a third exchange to an originating exchange in which a call was first established; After the origin exchange occupies the trunk with the destination exchange to perform the handoff, it sends a resource occupancy request message, and after the destination exchange transmits the handoff request message to the destination base station to perform the handoff, it receives a handoff response. Transmitting a handoff performance message to the destination base station; A third step of sending, by the destination exchange, a resource occupancy request response message to the base exchange, and constructing a new channel; A fourth step when the service exchange receives a handoff request response message from the originating exchange to the third system, sending a handoff command message to the service base station, and waiting for a resource release request message from the originating exchange; A fifth step of, when the destination exchange receives the handoff completion message from the destination base station, transmitting a radio occupancy channel notification message to the base exchange and connecting a call path; A sixth step in the base switching center, recovering the trunk after the transfer of the resource release request message to the service switching center after the transfer from the communication path with the service exchange which provided the previous service to the communication path with the destination exchange; A seventh step of recovering a trunk, restoring a call path, and transmitting a traffic channel recovery request message to the service base station and transmitting a resource release request response message to the base station; And an eighth step of terminating a handoff procedure to a third system when receiving a traffic channel recovery completion message from the service base station. The access switching subsystem for mobile subscriber (ASS-M) according to claim 2 or 2, wherein the internal call path of the exchange is maintained without changing the space switch or the time switch of the other subscriber by maintaining the call path with the other subscriber. Hard handoff control method in a CDMA mobile switching center, characterized in that it is set using the front junction (Front Junctor).