KR100279676B1 - Handover Method in Code Division Multiple Access System by Backward Synchronous Transmission Method and Backward Synchronous Transmission Method Using the Same - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a handover method and a reverse synchronous transmission method using the same.

2. The technical problem to be solved by the invention

The present invention provides a handover method in which a mobile station performs handover by receiving an orthogonal code and a pseudo noise code of a target base station in a code division multiple access system using a reverse synchronous transmission scheme, and after performing the handover, the current base station and the target base station. The purpose of the present invention is to provide a synchronous transmission method for transmitting and receiving traffic to and from a mobile station by switching to a newly assigned code, and a recording medium thereof.

3. Summary of Solution to Invention

The present invention provides a first step of determining a point in time when a mobile station enters a handover area while maintaining backward synchronization with a current base station, and then transitions an object of reverse synchronization from the current base station to a target base station; And a second step in which the mobile station is assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performs handover to the target base station.

4. Important uses of the invention

The present invention is used in a reverse synchronous communication system.

Description

Handover Method in Code Division Multiple Access System by Backward Synchronous Transmission Method and Backward Synchronous Transmission Method Using the Same

The present invention relates to a handover method in a code division multiple access (CDMA) system using a reverse synchronous transmission method, a reverse synchronous transmission method using the same, and a computer-readable recording medium recording a program for realizing the method. .

First, in the reverse synchronous transmission scheme, in order to reduce the reverse interference, the synchronization setting method and the reverse synchronous transmission method using the same to divide the channels with orthogonal codes and maintain the orthogonality between these channels in the reverse direction are provided by the applicant of the present invention. It has been previously filed (Patent application No. 98-29760: reverse synchronization setting method in the mobile communication system and reverse synchronous transmission method using the same).

On the other hand, in the conventional general code division multiple access (CDMA) communication system including the "IS-95" method, a separate pseudo noise (PN) code is assigned to each mobile station (channel) so that the mobile station moves to a new cell. Even if the communication was performed with the existing pseudo noise (PN) code.

However, in a code division multiple access (CDMA) communication system using a reverse synchronous transmission scheme, each mobile station (channel) is divided into orthogonal codes in order to provide orthogonality. The orthogonal code of cannot be assigned.

Therefore, in the code division multiple access (CDMA) communication system using the backward synchronous transmission scheme, the base station classification pseudo noise (PN) code and the mobile station (channel) identification orthogonal code are used in the reverse direction as in the forward direction. Instead of sharing a limited orthogonal code with each base station, since the PN codes for different base stations are different from each other, each mobile station (channel) can be allocated.

However, in this case, when the mobile station moves to a new base station area, there is a problem in that a pseudo noise (PN) code and an orthogonal code of the new base station are allocated and communicated. If the existing assigned PN code and orthogonal code are used as it is, orthogonality with other mobile stations in the new base station cannot be obtained, meaning of backward synchronous transmission is lost.

That is, according to the conventional handover method, even if the mobile station moves to a new base station area, the mobile station continues to transmit a signal because it uses the pseudonoise (PN) code allocated to the mobile station. An initial method of handover is performed in which a base station controller simultaneously compares two signals and selects a good signal. This results in breaking the orthogonality of the backward synchronous transmission scheme in the new base station.

Therefore, in a code division multiple access (CDMA) communication system using a reverse synchronous transmission scheme, when a mobile station moves to a new base station, a new code is assigned to establish a reverse synchronization with the new base station. It must be carried out in stages. Therefore, the present invention proposes a new handover method in a code division multiple access (CDMA) communication system using a reverse synchronous transmission scheme.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and in a code division multiple access (CDMA) system using a reverse synchronous transmission scheme, a mobile station performs handover by receiving an orthogonal code and a pseudo noise (PN) code of a target base station. A handover method and a reverse synchronous transmission method in which both the current base station and the target base station switch to a newly assigned code after performing the handover and transmit and receive traffic with the mobile station, and a computer readable program recording the program for realizing the method. The purpose is to provide a recording medium.

In addition, the present invention, if more fingers are assigned to the target base station or the received signal from the target base station in the process of receiving and combining the signals of the current base station and the handover target base station is determined that the target base station of the target base station; A handover method in which an orthogonal code is assigned and a pseudo noise (PN) code is also converted to a pseudo noise (PN) code for a target base station to perform a handover, and a new code assigned to both the current base station and the target base station after performing such a handover It is another object of the present invention to provide a synchronous transmission method for transmitting and receiving traffic to and from a mobile station by switching to a mobile station, and a computer-readable recording medium recording a program for realizing the method.

In addition, when the base station controller determines that a signal reported from the target base station is better in the process of performing the signal selection, the present invention not only selects the signal but also assigns the orthogonal code to the target base station, and the target base station is available according to the command. A handover method for performing a handover by assigning an orthogonal code and switching the received code of the mobile station, and when the mobile station transmits the assigned code to the base station controller, the base station controller transmits this information to the current base station so that the current base station can also transmit the mobile station signal. It is another object to provide a reverse synchronous transmission method for transmitting and receiving traffic in synchronization with a promised time point and a new code for receiving, and a computer-readable recording medium having recorded thereon a program for realizing the method.

1 is a schematic structural diagram of a code division multiple access system to which the present invention is applied.

2 is a flowchart illustrating an embodiment of a handover method and a reverse synchronous transmission method using the same when a subject for determining handover is a mobile station;

3 is a flowchart illustrating an embodiment of a handover method and a reverse synchronous transmission method using the same when a subject for determining whether a handover is a base station controller;

* Explanation of symbols for the main parts of the drawings

110: base station

120, 122, 124, 126: mobile station

130: base station controller

A handover method for achieving the above object is a handover method applied to a code division multiple access system using a reverse synchronous transmission scheme, wherein when a mobile station enters a handover region while maintaining backward synchronization with a current base station, A first step of determining a time point at which a target of reverse synchronization is transitioned from the current base station to a target base station; And a second step in which the mobile station is assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performs handover to the target base station.

In addition, the reverse synchronous transmission method of the present invention is a reverse synchronous transmission method applied to a code division multiple access system using a reverse synchronous transmission method, wherein the mobile station enters a handover region while maintaining backward synchronization with the current base station. Determining a time point at which a target of reverse synchronization is transitioned from the current base station to a target base station according to a reverse received signal; A second step of the mobile station being assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performing a handover to the target base station; A third step of the target base station transmitting and receiving traffic with the mobile station as handover is performed; And a fourth step in which the current base station is also assigned an orthogonal code and a pseudo noise (PN) code of the target base station according to a command of a base station controller and transmits and receives traffic with the mobile station.

On the other hand, the present invention, in the code division multiple access system having a high-capacity processor for the handover in the reverse synchronous transmission scheme, while maintaining the reverse synchronization with the current base station, when the mobile station enters the handover region, the reverse synchronization A first function of determining a time point at which the target of the transition from the current base station to the target base station; And a computer-readable recording medium having recorded thereon a program for realizing a second function of performing a handover to the target base station by receiving the orthogonal code and the pseudo noise (PN) code of the target base station. .

On the other hand, the present invention, in the code division multiple access system having a high-capacity processor for backward synchronous transmission, if the mobile station enters the handover area while maintaining backward synchronization with the current base station, the reverse synchronization according to the reverse received signal A first function of determining a time point at which the target of the transition from the current base station to the target base station; A second function of the mobile station being assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performing a handover to the target base station; A third function of transmitting and receiving traffic to and from the mobile station as handover is performed; And a computer-readable recording program recording a program for realizing a fourth function of transmitting and receiving traffic with the mobile station by receiving an orthogonal code and a pseudo noise (PN) code of the target base station according to a command of a base station controller. Provide the medium.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic structural diagram of a code division multiple access system to which the present invention is applied.

As shown in the figure, the code division multiple access system to which the present invention is applied includes a base station 110 and mobile stations 120, 122, 124, and 126.

In addition, in a code division multiple access system, each cell is a unit area in which the base station 110 and the mobile stations 120, 122, 124, and 126 communicate wirelessly, and the mobile stations 120, 122, 124, and 126 are carried by the user. A terminal device capable of freely communicating while moving, and the base station 110 is a device fixedly located in each cell in order to relay the communication of the mobile station (120, 122, 124, 126).

Next, the main concept of the present invention will be described in detail.

The mobile station continuously measures the received signals of the current base station and the neighboring base station and compares the received signal from the neighboring base station with the current base station received signal, and if the received signal from the base station is determined to be greater than the received signal of the current base station by the base station, the mobile station hands the base station. Send a command to perform the over (similar to the existing IS-95 scheme).

The base station notifies the handover capable base stations reported by the mobile station of the orthogonal code currently used by the mobile station and its pseudo noise (PN) code, and transmits a command through the base station controller to receive the transmission signal of the mobile station. Accordingly, when each of the handoverable base stations receives the mobile station signal and reports it to the base station controller, the base station controller selects the best base station received signal (same as IS-95). The process up to this point is similar to the conventional method since the mobile station has not yet switched between the orthogonal code and the pseudo noise (PN) code.

However, in a communication system considering reverse link synchronous transmission, even if backward synchronization is established with the current BS, when the mobile station completes handover to the target BS, backward synchronization with the target BS should be newly established. do. This is a basic implementation method of the reverse synchronous communication system considering the handover proposed in the present invention.

The important thing here is to determine when the mobile station transitions the object of reverse synchronization from the current base station to the target base station, which is also proposed in the present invention. The following two methods are proposed in a manner in which the mobile station transitions backward synchronization to a base station targeted for backward synchronization, that is, a new orthogonal code and a pseudo noise (PN) code are allocated.

In the first method, the mobile station is dominant. In the process of receiving and combining the signals of the current base station and the handover target base station, the mobile station allocates more fingers or receives signals from the target base station. If it is determined to be larger, then an orthogonal code of the target base station is allocated and the pseudo noise (PN) code is also converted to a pseudo noise (PN) code for the target base station. Thereafter, both the current base station and the target base station switch to newly assigned codes to attempt a call with the mobile station.

In the second method, the base station controller is dominant. When the base station controller determines that the signal reported from the target base station is better in the process of performing the signal selection, not only the signal selection but also the assignment of the orthogonal code to the target base station is performed. Command Subsequently, when the target base station assigns an available orthogonal code according to the command, switches the received code of the mobile station, and transmits the assigned code to the base station controller, the base station controller transmits this information to the current base station so that the current base station can also transmit the mobile station signal. Synchronize with the new time and the promised time to receive.

2 and 3 to be described below are flowcharts of an embodiment of a handover method and a reverse synchronous transmission method using the same according to the present invention. As shown in the figure, when the mobile station enters the handover area while maintaining backward synchronization with the current base station, it continuously compares the reception quality with a specific reference value possessed by the mobile station (FIG. 2) or the base station controller (FIG. 3). If the reference value is exceeded, a process of handover to a pseudo noise (PN) code and an orthogonal code of the target base station is shown.

2 is a flowchart illustrating an embodiment of a handover method and a reverse synchronous transmission method using the same when a subject for determining handover is a mobile station.

2 illustrates a case in which the subject determining the handover is a mobile station, and determines whether the handover is performed based on the strength of the pilot signal of the forward link or the number of fingers.

Initially, the mobile station continues to monitor the strength of pilot signals received from the current base station and the target base station. At the initial time point 21 entering the handover region, the pilot signal strength from the current base station is superior to the pilot signal strength from the target base station (22), but the pilot signal from the target base station at some point as the mobile station gradually moves to the target base station. There is a point in time when the strength is received stronger than the pilot signal strength from the current base station, or when the signal from the target base station occupies a large number of fingers in the mobile station (23), at which point the mobile station is responsible for handover. It is determined by the viewpoint (24).

Subsequently, when the handover is performed, the target base station transmits and receives traffic in a state of backward synchronization with the mobile station (25), and the current base station also receives an orthogonal code and a pseudo noise (PN) code of the target base station according to a command of the base station controller. Resume data transmission and reception with the mobile station (26,27).

3 is a flowchart illustrating an embodiment of a handover method and a reverse synchronous transmission method using the same when a subject for determining handover is a base station controller.

3 is a case where the subject of the handover decision is the base station controller, it is determined whether or not the handover based on the quality of the reverse link.

Once the mobile station enters the handover area (31), the base station controller uses a selective combining method (32), which detects backward received signals from the current base station and the target base station, respectively, and selects a better one of them. At this time, if it is determined that the signal reported from the target base station is better in the process of performing the signal selection (33), the received signal from the target base station is selected and the handover is performed to the pseudo noise (PN) code and the orthogonal code of the target base station. Command 34 to do it. In this case, one of several methods may be selected as a criterion for signal selection, such as FER of a reverse traffic channel or received signal strength of a reverse pilot symbol.

Subsequently, when the handover is performed, the target base station transmits and receives traffic in the state of backward synchronization with the mobile station (35), and the current base station also receives an orthogonal code and a pseudo noise (PN) code of the target base station according to the command of the base station controller. Resume data transmission and reception with the mobile station (36,37).

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention can maximize the effect of the synchronization between the reverse link channels by using the PN code and the orthogonal code of the target base station for the reverse transmission of the mobile station after performing the handover.

That is, if the mobile station still performs backward transmission through the PN code and the orthogonal code of the current base station in the target base station after performing the handover, it becomes a cause of reverse link synchronization in the target base station. Therefore, it is preferable to shift to the pseudo noise (PN) code and the orthogonal code of the target base station in the handover area, and handover is performed accordingly. That is, when the current base station and the target base station communicate with the mobile station based on the code of the current base station and satisfy the handover criterion proposed by the present invention, the handover occurs instantaneously with the sign and time offset of the target base station. Therefore, it is possible to maintain backward synchronization of all mobile stations in the target base station, so that orthogonality between the reverse channels is completely established, and the capacity beyond the channel capacity in the forward link having a large number of control channels can be obtained in the reverse direction.

Claims (16)

A handover method applied to a code division multiple access system using a backward synchronous transmission method, A first step of determining a point in time when the mobile station enters a handover area while maintaining backward synchronization with the current base station, transitioning the object of reverse synchronization from the current base station to the target base station; And A second step in which the mobile station is assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performs handover to the target base station; Handover method comprising a. The method of claim 1, The first step is, The handover method according to claim 1, wherein the handover time is determined based on the strength of the pilot signal when the subject determining the handover is the mobile station. The method of claim 2, The first step is, The mobile station entering the handover region continues to monitor the strength of the pilot signals received from the current base station and the target base station, and as the mobile station moves to the target base station, the pilot signal strength from the target base station is increased to the current base station. And a handover time point is determined from a time point when the signal received from the base station is stronger than the pilot signal strength. The method of claim 1, The first step is, The handover method according to claim 1, wherein the handover time is determined based on the number of fingers occupied by the mobile station. The method of claim 4, wherein The first step is, The mobile station entering the handover area continues to monitor pilot signals received from the current base station and the target base station, and then targets the plurality of fingers in the mobile station as the mobile station moves to the target base station. A handover method comprising determining a handover point in time at which a signal from a base station occupies. The method of claim 1, The first step is, If the subject to determine whether the handover is the base station controller, the handover method characterized in that the handover time is determined based on the quality of the reverse link. The method of claim 6, The first step is, When the mobile station enters a handover area, the base station controller detects reverse reception signals from the current base station and the target base station, respectively, and determines that the signal quality of the target base station is better than the signal quality of the current base station. The handover method, characterized in that for determining the handover time. A reverse synchronous transmission method applied to a code division multiple access system using a reverse synchronous transmission method, Maintaining a backward synchronization with the current base station, and when the mobile station enters the handover region, determining a time point at which the reverse synchronization target is transitioned from the current base station to the target base station according to a reverse reception signal; A second step of the mobile station being assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performing a handover to the target base station; A third step of the target base station transmitting and receiving traffic with the mobile station as handover is performed; And A fourth step in which the current base station is also assigned an orthogonal code and a pseudo noise (PN) code of the target base station according to a command of a base station controller to transmit and receive traffic with the mobile station; Reverse synchronous transmission method comprising a. The method of claim 8, The first step is, And when the subject determining the handover is the mobile station, determining the handover time based on the strength of the pilot signal. The method of claim 9, The first step is, The mobile station entering the handover region continues to monitor the strength of the pilot signals received from the current base station and the target base station, and as the mobile station moves to the target base station, the pilot signal strength from the target base station is increased to the current base station. And a handover time point is determined from a time point when the signal received from the base station is stronger than the pilot signal strength. The method of claim 8, The first step is, And when the subject determining the handover is the mobile station, determining the handover time based on the number of fingers occupied. The method of claim 11, The first step is, The mobile station entering the handover area continues to monitor pilot signals received from the current base station and the target base station, and then targets the plurality of fingers in the mobile station as the mobile station moves to the target base station. And a handover point in time at which a signal from a base station occupies. The method of claim 8, The first step is, If the subject to determine whether the handover is the base station controller, the handover timing is determined based on the quality of the reverse link. The method of claim 13, The first step is, When the mobile station enters a handover area, the base station controller detects reverse reception signals from the current base station and the target base station, respectively, and determines that the signal quality of the target base station is better than the signal quality of the current base station. The method for synchronous transmission, characterized in that for determining the handover time. In the code division multiple access system having a large capacity processor for handover in the reverse synchronous transmission scheme, Maintaining a backward synchronization with the current base station, and when the mobile station enters a handover region, a first function of determining a time point for transitioning the reverse synchronization target from the current base station to the target base station; And A second function in which the mobile station is assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performs handover to the target base station; A computer-readable recording medium having recorded thereon a program for realizing this. In the code division multiple access system having a large capacity processor for reverse synchronous transmission, Maintaining a backward synchronization with the current base station, and when the mobile station enters the handover region, a first function of determining a time point at which the reverse synchronization target is transitioned from the current base station to the target base station according to a reverse reception signal; A second function of the mobile station being assigned an orthogonal code and a pseudo noise (PN) code of the target base station and performing a handover to the target base station; A third function of transmitting and receiving traffic to and from the mobile station as handover is performed; And A fourth function of transmitting and receiving traffic to and from the mobile station by receiving an orthogonal code and a pseudo noise (PN) code of the target base station according to a command of a base station controller; A computer-readable recording medium having recorded thereon a program for realizing this.