A hand-off method between synchronous system and asynchronous system

A hand-off method between synchronous system and asynchronous system

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

2 is a diagram for explaining a pilot pattern matching and 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.

<background-art><p>The present invention relates to a handoff method between a synchronous system and an asynchronous system, and more particularly, to a synchronous system in an asynchronous system in a dual-mode mobile terminal that simultaneously supports a synchronous system and an asynchronous system and has a built-in GPS. It relates to a method for smooth handoff to a system.</p><p>With the development of mobile communication technology and the evolution of communication networks, various types of mobile communication systems are being developed. In particular, in the mobile phone service, the problem of global roaming support is seriously emerging due to the differences in frequencies or communication methods in each country.</p><p>To solve this problem, in the International Mobile Telecommunication (IMT)-2000 system, the development of the system was promoted with the goal of global roaming, but due to the interests of each country, it is not a unified standard, but a synchronous method and asynchronous method. It is being developed in a divided way.</p><p>That is, the current IMT-2000 system is being developed by dividing it into a CDMA2000-based synchronous system and a W-CDMA-based asynchronous system.</p><p>Mobile communication terminal developers are developing dual-mode terminals that can be used in both synchronous and asynchronous systems to support global roaming, and have built-in GPS (Global Positioning System) to provide various location-related services. We are preparing for the development of a mobile communication terminal.</p><p>The dual-mode terminals supporting both the synchronous and asynchronous methods have respective protocol stacks, but support one wireless interface at any one time. That is, in the service area of the asynchronous system, the asynchronous service is provided, and in the synchronous service area, the synchronous service is provided.</p><p>When the network construction for the asynchronous service is performed step by step as illustrated in FIG. 1 , the service area of the 2nd generation synchronous system includes the service area of the 3rd generation asynchronous system.</p><p>In this process, when a user moves from an asynchronous 3G system to a synchronous 2G system, inter-system handoff is required for continuous service. That is, when the mobile terminal moves from cell B of the 3rd generation system to cell A of the 2nd generation system as shown in FIG. 1 , handoff must be provided to the 2nd generation system using the handoff procedure of the 3rd generation system.</p><p>In Fig. 1, a base station in each cell (2nd generation-cells A, B, C, D, E, F) of the 2nd generation system is connected to a control station (2nd generation-control station) of the corresponding 2nd generation system, and the The control station of the 2nd generation system (2nd generation-control station) is connected with the switching center of the 2nd generation system (2nd generation-switching center). The base stations (nodes A, B, C) in each cell (3rd generation - cell A, B, C) of the 3rd generation system are connected to the control station (3rd generation - control station) of the corresponding 3rd generation system, and the 3rd generation The control station of the system (3rd generation-control station) is connected to the switching center of the 3rd generation system (3rd generation-switching station). And, the switching center of the second generation system (second generation-switching center) and the switching center of the third generation system (third generation-switching center) are interconnected by an interworking function unit.</p><p>In case of handoff from an asynchronous system to a synchronous system, the biggest problem is the problem of obtaining synchronization of the synchronous system.</p><p>In general, in a synchronous system, all base station nodes synchronize the system based on the GPS time.</p><p>However, the asynchronous system maintains synchronization between the systems by adjusting the offset values between nodes, but the system synchronization is not as accurate as that of the synchronous system.</p><p>In the synchronization system, a synchronization channel message is transmitted to a mobile terminal that has acquired a pilot for system synchronization acquisition, which includes information such as system time, long code state information, and PN offset. Since the base station maintains accurate system synchronization, the mobile terminal receiving the information can accurately know the effective time for the corresponding information.</p><p>However, a mobile terminal operating in an asynchronous manner is allowed only an idle time of up to 10 msec at a time for system handoff at the time of handoff.</p><p>Therefore, it is impossible to receive a synchronization channel message composed of a frame of 20 msec or longer in a wireless section while the asynchronous system is operating. Even when the synchronous channel message is received through the network message of the asynchronous system, the system does not know the exact system time in the synchronous system, so there is a problem in system synchronization acquisition.</p><p>After all, in order to handoff from an asynchronous system to a synchronous system, communication in the asynchronous system is stopped, a pilot for the synchronous system is acquired, and the system time is adapted through reception of a synchronous channel message. is used, and in this case, a call disconnection occurs due to a handoff of several hundred msec or more.</p></background-art><tech><p>The present invention has been devised to solve the above-mentioned problems of the prior art, and it is to provide a handoff method between a synchronous system and an asynchronous system so that the system synchronization acquisition for the synchronous system can be quickly achieved using the system reference time of the GPS. There is a purpose.</p></tech>

<p>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 handoff between a synchronous system and an asynchronous system on a network using a dual-mode terminal,</p><p>a first step of measuring a pilot signal for the synchronous system through a compression mode in the dual-mode terminal as the asynchronous system transmits a handoff measurement request to the dual-mode terminal; a second process of identifying a PN offset value of a base station to perform handoff using pattern matching for pilot signals from each base station of the synchronization system and a reference time of the global positioning system; and a third process of reporting, together with the identified PN offset value, PN offset information for a base station capable of handoff and measured signal strength information of a synchronization cell to the network.</p><p>And, in the handoff method between the synchronous system and the asynchronous system according to another embodiment of the present invention, as the signal strength of the asynchronous system falls below a threshold value during a call between the dual mode terminal and the asynchronous system, the signal of the asynchronous system a first step of notifying the intensity measurement value to the control station of the asynchronous system; a second process of notifying the base station information of the adjacent synchronization system from the control station of the asynchronous system to the dual-mode terminal; In the dual mode terminal, the asynchronous system is operated in a compressed mode to measure the signal of the adjacent synchronous system, the measured signal of the synchronous system is pattern-matched, and the result is transmitted through the control station of the asynchronous system. a third process of notifying the control station to request a handoff; a fourth step of determining handoff from the control station of the synchronous system to a base station having the best signal strength and requesting handoff to the dual-mode terminal through the asynchronous system; and a fifth step of performing handoff from the dual-mode terminal to the synchronization system.</p><p>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.</p><p>2 is a diagram for explaining a pilot pattern matching and PN option calculation process applied to the present invention.</p><p>In an asynchronous system, when a measurement request for handoff from the network is transmitted to a mobile terminal, 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 measure If the pattern matching of the pilot signal and the reference time of the GPS are used for the pilot signals received from each base station in the synchronization system, the mobile terminal can calculate the PN offset, and the PN offset of the base station to perform handoff is determined. Able to know.</p><p>The GPS reference time is equally received by the base station and the mobile station (mobile terminal).</p><p>The PN code is composed of 32768 PN chips that are repeated every 26.67 msec, and the PN code is transmitted with a time interval equal to the PN offset with respect to the GPS reference time to distinguish the base stations. That is, when there are adjacent base stations A and B, the base station A transmits the PN code with a difference of as much as PN offset A with respect to the GPS reference time, and the base station B transmits the difference by the PN offset B with respect to the GPS reference time. and transmit the PN code.</p><p>The PN codes transmitted from the adjacent base station arrive at the mobile station after a certain propagation delay time according to the distance from the mobile station, and the propagation delay time is much smaller than the PN offset difference between the adjacent base stations, so it does not affect the identification of the base station. .</p><p>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 matched. Therefore, the PN offset value is calculated from the measured pilot signal using the GPS reference time. That is, since the pilot pattern is repeated every 26.67 msec, the GPS reference time is recorded for any point in time where pilot reception is possible, and after receiving the pilot pattern, it is mapped with the original PN code. In this way, information on where the corresponding pattern is located within one pilot PN period (ie, offset-A, offset-B) can be obtained, and time information about the starting point of the PN code can be calculated.</p><p>If the time information on the start point of the PN code calculated using the offset value is mapped to the reference time of the GPS, the absolute time at which the PN code starts can be known, and the PN offset value for the base station transmitting the corresponding pilot signal can be calculated. can If propagation delay time is reflected in this process, accurate time calculation is not performed. In this case, the closest PN offset is selected.</p><p>By repeating this operation, the PN offset for the adjacent cell is learned, and the PN offset for the base station to be handed off is learned based on the pilot signal strength information.</p><p>If the PN information and the base station ID for the adjacent synchronization cell have already arrived from the network, the mobile terminal can know the base station to perform the handoff, and when there is no PN information and the base station ID for the adjacent synchronization cell Reports PN offset information for a base station capable of handoff and measured signal strength information of a synchronization cell together with the PN offset value to the network.</p><p>Thereafter, after handoff processing is performed in the network, a handoff request message is transmitted to the mobile terminal. Upon receiving the handoff request message, the mobile terminal maps the handoff request time, that is, the asynchronous CFN value to the GPS system time, and readjusts the long code status information to match the handoff time.</p><p>3 is a flowchart illustrating a handoff method between a synchronous system and an asynchronous system according to an embodiment of the present invention.</p><p>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 gradually weakens, and in the boundary area where the asynchronous system and the synchronous system come into contact. When the signal strength of the asynchronous system falls below a predetermined threshold, the mobile station notifies the measured value of the signal strength of the asynchronous system to the control station of the asynchronous system through the base station.</p><p>The control station of the asynchronous system recognizes that the current mobile station is located in the boundary area of the asynchronous system, determines that handoff to the synchronous system is necessary, informs the mobile station of the base station information of the adjacent synchronous system, and measures and reports the synchronous system command to do Here, the base station information of the synchronous system to be notified is the base station designated by the operator as the base station at the base station boundary of the asynchronous system.</p><p>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 perform a call, and during the call, the mobile station performs a pattern match on the measured signal of the synchronous system to perform a delayed PN Find the code, measure the value of Ec/Io by despreading the received signal using the PN code of the delayed time from the reference time provided by GPS, and then report this value to the control station of the asynchronous system.</p><p>During a call, it takes about 10 msec to acquire the PN code of the synchronization system. Since a voice call consists of one frame in units of 20 msec, a call break of about 10 msec is not a big problem for the voice call.</p><p>The control station of the asynchronous system notifies the control station of the synchronous system of the reported result to request a handoff. The control station of the synchronization system that has been requested for handoff determines handoff to the base station having the best signal strength among the measured signal strengths of the base station, and requests channel allocation (radio link allocation) to the corresponding base station.</p><p>When the channel is allocated, the control station of the synchronous system notifies the mobile station of the channel allocation details through the asynchronous system again to instruct the mobile station to handoff.</p><p>Upon receiving the handoff instruction, the mobile station performs a handoff to the synchronous system by correcting the time elapsed so far, performs a call with the synchronous system, and notifies the synchronous system that the handoff is completed. Upon receiving that the handoff has been completed, the control station of the synchronous system notifies the asynchronous system of the completion of the handoff to release the resources of the asynchronous system.</p>

<p>As described in detail above, according to the present invention, service continuity support in the step-by-step construction process of the asynchronous system and the synchronous system can be used as a complementary system to the asynchronous system, thereby enhancing service competitiveness.</p><p>On the other hand, the present invention is not limited to the above-described embodiments, but can be implemented with modifications and variations within the scope without departing from the gist of the present invention, and the technical idea to which such modifications and variations are applied also falls within the scope of the following claims. have to see</p>