KR100376580B1 - A hand-off method between synchronous system and asynchronous system - Google Patents

Abstract

The present invention relates to a handoff method between a synchronous system and an asynchronous system for quickly acquiring a system synchronization for a synchronous system using a system reference time of GPS. A method for performing a handoff on a network, the method comprising: a first step of measuring a pilot signal for the synchronous system through a compression mode in the dual mode terminal as the handoff measurement request is transmitted from the asynchronous system to the dual mode terminal; A second step of identifying a PN offset value of a base station to be handed off using pattern matching for pilot signals from each base station of the synchronization system and a reference time of a global positioning system; And a third process of reporting, to the network, PEN offset information for the base station capable of handoff together with the identified PEN offset value and signal strength information of the measured sync cell to the network. Service continuity support and service system in synchronous system can be used as complementary system for asynchronous system.

Description

A hand-off method between synchronous system and asynchronous system

The present invention relates to a handoff method between a synchronous system and an asynchronous system. More particularly, the present invention relates to a synchronous system and an asynchronous system. To a method for smooth handoff to the system.

Due to the development of mobile communication technology and the evolution of communication networks, various types of mobile communication systems are being developed. In particular, the problem of global roaming support is a serious problem in the mobile phone service due to the different frequency or communication method of each country.

In order to solve this problem, the International Mobile Telecommunication (IMT) -2000 system has been developed for the purpose of global roaming, but due to the interests of each country, the synchronous and asynchronous methods are not integrated. It is developed in a divided way.

That is, the IMT-2000 system is currently being divided into a CDMA 2000-based synchronous system and a W-CDMA-based asynchronous system.

Mobile terminal developers are developing dual-mode terminals that can be used in both synchronous and asynchronous systems to support global roaming, and incorporate GPS (Global Positioning System) to provide various location-related services. We are preparing to develop a mobile communication terminal.

Dual-mode terminals supporting both the synchronous and asynchronous schemes have their respective protocol stacks, but at any one moment, they support one air interface. That is, an asynchronous service is provided in the service area of the asynchronous system, and a synchronous service is provided in the synchronous service area.

When the network construction for the asynchronous service is formed in stages as illustrated in FIG. 1, the second generation synchronous system has a service area including the service area of the third generation asynchronous system.

In this process, when a user moves from an asynchronous 3rd generation system to a synchronous 2nd generation system, handoff between systems is required for continuous service. That is, when the mobile terminal moves from cell B of the third generation system to cell A of the second generation system as shown in FIG. 1, handoff should be provided to the second generation system using the handoff procedure of the third generation system.

In Fig. 1, a base station in each cell (second generation-cells A, B, C, D, E, F) of the second generation system is connected to a control station (second generation-control station) of the corresponding second generation system. The control station (second generation-control station) of the second generation system is connected to the switching station (second generation-exchange station) of the second generation system. The base stations (nodes A, B, C) in each cell (3G-Cells A, B, C) of the 3G system are connected to the control station (3G-Control Station) of the corresponding 3G system, and the 3G The control station of the system (3rd generation control station) is connected to the switching station (3rd generation switching center) of the 3rd generation system. The switching station of the second generation system (2nd generation switching center) and the switching station of the third generation system (3rd generation switching center) are interconnected by an interworking function.

When handing off from an asynchronous system to a synchronous system, the biggest problem is the system's acquisition of the synchronous system.

In general, in the synchronous system, all base station nodes synchronize the system based on GPS time.

However, the asynchronous system maintains the synchronization between systems by adjusting the offset value between nodes, but the system synchronization is not as accurate as the synchronization system.

In the synchronous system, a synchronization channel message is transmitted to a mobile terminal that has obtained a pilot for system synchronization, and includes information such as system time, long code status information, and PN offset. Since the base station maintains accurate system synchronization, the mobile terminal receiving these information can know the valid time for the information accurately.

However, mobile terminals operating in an asynchronous manner are allowed only up to 10msec idle time at a time for system handoff during handoff.

Therefore, it is impossible to receive a synchronization channel message composed of frames of 20 msec or more in the wireless section while the asynchronous system operates. Even when a synchronous channel message is received through a network message of an asynchronous system, the system synchronization acquisition problem is not known because the exact system time is not known.

As a result, in order to hand off from an asynchronous system to a synchronous system, the communication in the asynchronous system is interrupted, the pilot for the synchronous system is acquired, and the system is adapted to the system time through the reception of the synchronous channel message. In this case, disconnection due to a handoff of several hundred msec or more occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a handoff method between a synchronous system and an asynchronous system to quickly acquire a system synchronization for a synchronous system using a system reference time of GPS. There is a purpose.

1 is a network construction diagram to which the present invention is applied,

2 is a view for explaining a pilot pattern matching and a PN option calculation process applied to the present invention;

3 is a flowchart illustrating a handoff method between a synchronous system and an asynchronous system according to an embodiment of the present invention.

In order to achieve the above object, a handoff method between a synchronous system and an asynchronous system according to a preferred embodiment of the present invention is a method for performing a handoff between a synchronous system and an asynchronous system on a network using a dual mode terminal.

A first step of measuring a pilot signal for the synchronous system through a compression mode in the dual mode terminal as the handoff measurement request is transmitted from the asynchronous system to the dual mode terminal; A second step of identifying a PN offset value of a base station to be handed off using pattern matching for pilot signals from each base station of the synchronization system and a reference time of a global positioning system; And a third process of reporting the PEN offset information and the measured signal strength information of the measured synchronization cell to the network together with the identified PEN offset value.

In addition, according to another embodiment of the present invention, the handoff method between the synchronous system and the asynchronous system includes a signal of the asynchronous system as the signal strength of the asynchronous system is lowered below a threshold value during a call between the dual mode terminal and the asynchronous system. A first step of notifying the control station of the asynchronous system of the strength measurement value; A second step of notifying the dual mode terminal of the base station information of the adjacent synchronous system from the control station of the asynchronous system; The dual mode terminal operates the asynchronous system in a compression mode to measure signals of the adjacent synchronous system, pattern-matches the measured signals of the synchronous system, and outputs the result of the synchronous system through the control station of the asynchronous system. A third step of informing the control station to request a handoff; A fourth step of determining a handoff from a control station of the synchronous system to a base station having the best signal strength and requesting a handoff to the dual mode terminal through the asynchronous system; And a fifth process of performing handoff from the dual mode terminal to the synchronization system.

Hereinafter, a handoff method between a synchronous system and an asynchronous system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a view illustrating a pilot pattern matching and a PN option calculation process applied to the present invention.

When a measurement request for handoff from a network is transmitted to a mobile terminal in an asynchronous system, the mobile terminal transmits a pilot signal to another system (ie, a synchronous system) during a transmission idle time of up to 10 msec through a compressed mode. Will be measured. By using the pattern matching of the pilot signal and the reference time of the GPS for the pilot signals received from each base station of the synchronization system, the mobile station can calculate the PN offset and calculate the PN offset of the base station to perform handoff. Able to know.

The GPS reference time is received by the base station and the mobile station (mobile terminal) in the same manner.

The PN code consists of 32768 PN chips repeated every 26.67 msec. The PN code transmits the PN code at a time interval equal to the PN offset with respect to the GPS reference time to distinguish the base stations. That is, when neighboring base stations have A and B, base station A transmits a PN code with a difference of PN offset A with respect to the GPS reference time, and base station B has a difference of PN offset B with respect to the GPS reference time. Send PN code.

The PN codes transmitted from the neighboring base stations arrive at the mobile station after a certain propagation delay time according to the distance to the mobile station. Since the propagation delay time is much smaller than the difference between the PN offsets between neighboring base stations, it does not affect the base station identification. .

When the pilot signal of the synchronous system is measured using the compression mode in the asynchronous system, the starting point of the PN code cannot be accurately set. Therefore, the PN offset value is calculated from the pilot signal measured using the GPS reference time. That is, since the pilot pattern is repeated every 26.67msec, the GPS reference time is recorded at any time point at which pilot reception is possible, and after receiving the pilot pattern, the pilot pattern is mapped with the original PN code. In this way, information (ie, offset-A, offset-B) on which part of the pattern is located within a pilot PN period can be obtained, and time information on the starting point of the PN code can be calculated.

By mapping the time information of the start point of the PN code calculated using the offset value to the GPS reference time, the absolute time at which the PN code starts can be known and the PN offset value for the base station transmitting the pilot signal can be calculated. Can be. In this process, when the propagation delay time is reflected, accurate time calculation is not performed. In this case, the nearest PN offset is selected.

By repeating this operation, the PN offset for the neighbor cell is known, and the PN offset for the base station to be handed off is found based on the pilot signal strength information.

If the PN information and the base station ID for the neighbor sync cell have already arrived from the network, the mobile terminal can know the base station to perform the handoff, and if there is no PN information and the base station ID for the neighbor sync cell. PN offset information for the base station capable of handoff and signal strength information of the measured sync cell are reported to the network together with the PN offset value.

Then, after the handoff process is performed in the network, a handoff request message is delivered to the mobile terminal. The mobile terminal receiving the handoff request message maps the time when the handoff is requested, that is, the CFN value of the asynchronous type to the system time of the GPS, and readjusts the long code state information to match the handoff time.

3 is a flowchart illustrating a handoff method between a synchronous system and an asynchronous system according to an embodiment of the present invention.

As the mobile station (mobile terminal with dual mode function) moves out of the asynchronous system in a busy state with the asynchronous system and approaches the synchronous system, the signal of the asynchronous system is gradually weakened, and at the boundary area where the asynchronous system and the synchronous system meet. When the signal strength of the asynchronous system falls below a predetermined threshold, the mobile station notifies the control station of the asynchronous system through the base station of the measured value of the signal strength of the asynchronous system.

The control station of the asynchronous system recognizes that the current mobile station is located in the boundary area of the asynchronous system and determines that handoff to the synchronous system is required, and notifies the mobile station of base station information of the adjacent synchronous system, and measures and reports the synchronous system. To do so. Here, the base station information of the synchronous system to be notified is a base station designated by an operator as a base station at the base station boundary of the asynchronous system.

The mobile station operates the asynchronous system in a compressed mode and measures the signal of the synchronous system. After measuring the signal of the synchronous system, the mobile station returns to the asynchronous system to continuously conduct a call, and during this call, performs a pattern match on the signal of the measured synchronous system to delay PN. Find the code, despread the received signal using the PN code delayed from the reference time provided by GPS, measure the value of Ec / Io, and report the value to the control station of the asynchronous system.

During the call, the time required to acquire the PN code of the synchronous system is about 10 msec. Since the call is composed of 20 msec frames, the disconnection of about 10 msec is not a problem for the voice call.

The control station of the asynchronous system notifies the control station of the synchronous system of the reported result and requests a handoff. The control station of the synchronization system requesting the handoff determines the handoff as the base station having the best signal strength among the measured signal strengths of the base station, and requests the base station to assign a channel (radio link assignment).

When the channel is allocated, the control station of the synchronous system again notifies the mobile station of the channel assignment details through the asynchronous system to instruct handoff of the mobile station.

The mobile station that has received the handoff instruction performs a handoff to the synchronization system by correcting by the elapsed time so far to make a call with the synchronization system and informs the synchronization system that the handoff is completed. Receiving that the handoff is complete, the control station of the synchronous system notifies the asynchronous system of the handoff completion to release the resources of the asynchronous system.

As described in detail above, according to the present invention, service continuity support and the synchronous system can be used as a complementary system to the asynchronous system in the stepwise construction process of the asynchronous system, thereby enhancing service competitiveness.

On the other hand, the present invention is not limited only to the above-described embodiment, but can be modified and modified within the scope not departing from the gist of the present invention, the technical idea to which such modifications and variations are also applied to the claims Must see

Claims (9)

In a method for performing a handoff between a synchronous system and an asynchronous system on a network using a dual mode terminal, A first step of measuring a pilot signal for the synchronous system through a compression mode in the dual mode terminal as the handoff measurement request is transmitted from the asynchronous system to the dual mode terminal; A second step of identifying a PN offset value of a base station to be handed off using pattern matching for pilot signals from each base station of the synchronization system and a reference time of a global positioning system; And And a third process of reporting, to the network, PEN offset information of the base station capable of handoff together with the identified PEN offset value and signal strength information of the measured sync cell to the network. Off way. The method of claim 1, The second process, The reference time of the global positioning system is recorded at any point in time at which the pilot signal can be received, the pilot pattern is received, and then mapped to the original PEN code, which part of the pilot pattern is located within one pilot PIE period. Calculating offset information for and time information on the starting point of the PEN code; And The time information of the start point of the PEN code is mapped to the reference time of the global positioning system to calculate the PEN offset value for the base station transmitting the pilot signal and the absolute time at which the PEN code starts and the PEN for the base station to be handed off. And a second step of identifying an offset value. The method of claim 1, And re-adjusting a sync channel message information element with respect to the determined handoff time after the handoff process is performed. The method of claim 3, wherein The sync channel message information element includes long code state information and a P & N offset, and uses this as a handoff related message information field in the asynchronous system. A first step of notifying the control station of the asynchronous system of the signal strength measurement value of the asynchronous system as the signal strength of the asynchronous system is lowered below a threshold value during the call between the dual mode terminal and the asynchronous system; A second step of notifying the dual mode terminal of the base station information of the adjacent synchronous system from the control station of the asynchronous system; The dual mode terminal operates the asynchronous system in a compression mode to measure the signal strength of the adjacent synchronous system, pattern-match the measured signal of the synchronous system, and output the result through the control station of the asynchronous system. Requesting handoff by notifying the control station of the third step; Determining a handoff from the control station of the synchronization system to the base station having the strongest signal strength and requesting handoff to the dual mode terminal through the asynchronous system; And And a fifth process of performing handoff from the dual mode terminal to the synchronous system. The method of claim 5, The base station information of the adjacent synchronous system to be notified in the second step is information about the base station on the boundary of the base station of the asynchronous system. The method of claim 5, In the fourth process, if a handoff to the base station having the strongest signal strength is determined, the channel is allocated to the corresponding base station, and the channel allocation history is notified to the dual mode terminal through the asynchronous system. Handoff method between system and asynchronous system. The method of claim 5, The fifth process is a handoff method between a synchronous system and an asynchronous system, wherein the dual mode terminal that has requested a handoff is corrected by the elapsed time so as to perform a handoff to the synchronous system. The method of claim 5, And after the handoff to the synchronous system is completed, a step of notifying the asynchronous system of the handoff completion by the control station of the synchronous system to release resources of the asynchronous system. How to handoff between systems.