KR20010028203A - apparatus and method for implementing hand-off from asynchronous mobile communication system to synchronous mobile communication system having auxiliary sync channels - Google Patents

Abstract

PURPOSE: The apparatus for performing handoff is provided to make a synchronous system base station transmit a 'PN_OFFSET' value through the first short synchronization channel, and to obtain information on peripheral cells in a shortest time, so as to reduce call cutoff times between the synchronous mobile communication system and a mobile station. CONSTITUTION: A forward pilot channel generator(103) generates a pilot signal. A forward synchronous channel generator(104) generates a synchronous signal. The first forward auxiliary synchronous channel generator(105) generates 'PN_OFFSET' information of a base station. The second forward auxiliary synchronous channel generator(106) generates a long code state signal of the base station and frame timing information. A forward DCCH(Dedicated Control Channel) generator(102) generates a control message of a DCCH. A forward dedicated fundamental channel generator(108) generates a voice signal. A forward dedicated supplementary channel generator(109) generates packet data.

Description

Apparatus and method for implementing hand-off from asynchronous mobile communication system to synchronous mobile communication system having auxiliary sync channels

The present invention relates to an apparatus and method for performing handoff in a mobile communication system, and more particularly, to an apparatus and method for handoff that occurs when a mobile station moves from an asynchronous mobile communication system to a synchronous mobile communication system.

The asynchronous mobile communication system may be, for example, UMTS adopted by a European standard method, and the synchronous mobile communication system may be a second generation such as IS-95 or J-STD008 in Korea, the United States, and Japan. CMT systems and IMT2000, which is adopted in the US standard manner. Currently, the two systems are harmonized, and accordingly, various technologies for making the two systems compatible are required. One of them is a technique for handoff that can occur between two systems.

In general, handoff is a technology that allows a user to communicate without interruption of a call when the mobile station moves from one cell to another in the mobile communication system. There are two methods for the handoff, one of which is assigned a channel from the base station that is the target of the handoff during communication, and communicates using a plurality of channels together with the channel received from the currently serving base station. The soft handoff is to cut off the channel which falls below, and the second is a hard handoff to disconnect the channel received from the base station currently being serviced and to connect to the neighboring base station during communication.

Until now, the technology of the handoff has developed around a synchronous mobile communication system. However, with the advent of the asynchronous mobile communication system, the handoff technology between the asynchronous mobile communication system and the asynchronous mobile communication system is being researched. As the implementation of the asynchronous mobile communication system becomes possible, the handoff between the asynchronous mobile communication system and the synchronous mobile communication system is also studied. Off implementation is required.

In general, a mobile station communicating in a cell of a mobile communication system measures and reports information on neighboring cells to a base station when a pilot signal received by the mobile station has a predetermined value or a request from the base station of the mobile communication system. The reported information is used as information about the handoff generated when the mobile station moves to another cell during communication. The information is transmitted to the mobile station through a paging channel (in the case of a synchronous mobile system) or a broadcasting channel (in the case of an asynchronous mobile communication system).

In general, a hard handoff occurs when a mobile station moves from an asynchronous mobile communication system to a synchronous mobile communication system. When the hard handoff is performed, communication with the asynchronous mobile communication system is stopped while the mobile station is measuring information on neighboring cells.

In general, in order to interpret the system information in the conventional synchronous mobile communication system, the following process is required. The mobile station interprets the synchronization signal message contained in the synchronization signal frame transmitted in the synchronization channel of the synchronization mobile communication system. Here, the transmission bit per 80ms frame of the synchronization signal frame is 96 bits, and the length of the synchronization signal message including information that the mobile station can communicate with the synchronous mobile communication system is 221 bits. Therefore, the mobile station needs at least 240 ms (80 ms x 3) as the interpretation time of the message. The figures in the above description describe what is specified in the TIA / EIA-IS-2000.5 of the standard that defines the synchronous mobile communication system.

3 illustrates a process of measuring information on a synchronous mobile communication system around a asynchronous mobile communication system by a mobile station in communication in the asynchronous mobile communication system. Referring to FIG. 3, in step 301, the mobile station receives an information measuring instruction for a peripheral synchronous mobile communication system from an asynchronous mobile communication system base station. Then, in step 303, the mobile station starts searching for information on the synchronous mobile communication system around the asynchronous mobile communication system. In step 305, the mobile station detects the pilot signal of the synchronous mobile communication system. In step 307, the mobile station checks whether a pilot signal having a maximum amplitude is detected. At this time, when detecting the pilot signal having the maximum size, the mobile station proceeds to step 309. When the pilot signal having the maximum size is not detected, the mobile station returns to step 305 to perform the pilot signal detection operation of the synchronous mobile communication system again. . In step 309, the mobile station that detects the pilot signal having the maximum size receives the sync frame transmitted on the forward sync channel of the synchronous mobile communication system. Here, the mobile station should receive at least three sync frames in units of 80msec. When receiving a synchronous frame transmitted in the synchronous mobile communication system having a channel structure as shown in FIG. 2, the minimum reception time is 240ms, during which the mobile station stops communicating with the asynchronous mobile communication system. Furthermore, since there is no guarantee that the start of reception is the beginning of the message, 240 msec. If you include the time to wait for the starting point of the unit, communication interruption of about 513.3 msec is required even if there is no reception frame error. Therefore, a long time for performing the process illustrated in FIG. 3 may cause loss of communication data between the asynchronous mobile communication system and the mobile station. This assumption does not comply with the compressed mode specification defined in asynchronous systems for monitoring other frequency bands proposed in the asynchronous standard.

The base station forward channel structure of a conventional synchronous mobile communication system is shown in FIG. Referring to FIG. 2, a forward pilot channel 203 for generating a pilot signal, a forward sync channel 204 for generating a synchronization signal, a forward dedicated control channel 202 for generating a control message for a dedicated channel, and a forward direction for generating a voice signal It consists of a dedicated basic channel 207 and a forward dedicated additional channel 208 for generating packet data. The detailed specification and operation of each channel is described in detail in the previously filed patent application P1998-11381 of the present applicant.

12 illustrates a handoff procedure when the mobile station moves from the asynchronous mobile communication system to the synchronous mobile communication system having the above structure. In the following description, a base station of the asynchronous mobile communication system is referred to as an asynchronous base station 12001, and a base station of the synchronous mobile communication system is referred to as a synchronous base station 12003.

Referring to FIG. 12, it is assumed that the mobile station B is handed off from the asynchronous base station to the synchronous base station. 12 is a message transmitted / received between the asynchronous base station and the mobile station. 12, the step 1201 message is a message for transmitting information on neighbor cells updated by the base station to the mobile station through a broadcast channel or a paging channel. After receiving the message of step 1202 from the mobile station B, the asynchronous base station of FIG. 12 interprets the message of step 1202 and determines the handoff of the mobile station B if there is another asynchronous base station to which the mobile station B is to be handed off. After interpreting the message of step 1102 and detecting that the mobile station B has not found the pilot signal of the other asynchronous base station to be handed off, the asynchronous base station sets parameters T, T ₀ , N for detecting the pilot signal of the synchronous base station. Then, a step 1203 message is sent to the mobile station. Receiving the message 1203 of FIG. 12, the mobile station measures pilot signals of the synchronous base station and the asynchronous base station in the vicinity of the asynchronous base station. In FIG. 12, it is assumed that the mobile station has detected a pilot signal of the synchronization base station. After detecting the pilot signal of the synchronous base station, the mobile station interprets the synchronous message transmitted through the forward synchronous channel of the synchronous base station, and then transmits a message to the asynchronous base station. After receiving the message in step 1204, the asynchronous base station receives the handoff command from the mobile station B to the synchronization base station C through the upper network, and transmits the message in step 1205. The message in step 1205 of FIG. 12 is a Handoff Direction message and includes call channel information for a call at the synchronization base station.

The messages 1206-1211 of FIG. 12 are messages transmitted and received between the mobile station and the synchronization base station. The message 1206 of FIG. 12 is transmitted through a forward pilot channel as a pilot signal continuously transmitted by the synchronous base station. The step 1206 message is information transmitted through the forward pilot channel. The signal input to the forward pilot channel is always a logic signal 0 or 1 (both send 0 or send 1). The step 1206 message enables the mobile station to estimate the channel and enables fast initial synchronization for a new multipath. The mobile station estimates the channel of the synchronization base station by detecting the PN_OFFSET value transmitted from the synchronization base station using the step 1206 message. At this point the mobile station does not know the exact PN_OFFSET of the base station and only detects the position of PN_OFFSET with the maximum value. Accordingly, the mobile station detects the message of step 1206 and simultaneously receives the message of step 1107 to determine information about the synchronous base station. The step 1207 message is information contained in a sync frame transmitted through a forward sync channel. The 1212 message is a system identification number, a network identification number, a PN_OFFSET value, information about a long code state after 320 ms, and system information that must be known to communicate with a base station such as a paging channel data rate. As an example of a synchronization channel through which the message of step 1207 is transmitted, a frame of a synchronization channel used in IS-95 has a length of 80 ms, consists of three subframes having an end call cycle length, and transmits 96 bits per frame. do. In the example of the synchronization channel, the system information is over 200 bits including the message length field and the CRC. In addition, the 80 ms sync frame is transmitted with a length of 96 bits by inserting an extra bit even if the data length is not 96 bits. In order to include all of the system information, three 80 ms sync frames are required. Accordingly, in FIG. 12, it is assumed that there is no transmission error of the step 1207 message, and even if the mobile station receives the step 1207 message transmitted from the synchronous base station, the mobile station knows that the base station transmitting the step 1207 message is the synchronous base station. A minimum time of 240 ms is required to obtain information on the synchronization base station. 12, after receiving the message 1107, the mobile station transmits the information contained in the message 1207 to the asynchronous base station using the message 1204. In FIG. 12, when the mobile station receives a handoff direction message from the synchronization base station, the synchronization base station transmits a message 1208 to the mobile station. The step 1208 message is null traffic or other data transmitted through the forward basic channel of the synchronous base station, and the synchronous base station tests the channel stability with the mobile station. In FIG. 12, the message transmitted from the mobile station to the cell of the synchronous base station is a message transmitted through a forward basic channel. In step 1209, a call communicating with the mobile station and an asynchronous base station is connected to the synchronous base station. Transmitted to the mobile station. 12, the mobile station receiving the message of step 1209 transmits a message of step 1210 through a reverse base channel. The step 1210 message is a reverse signal transmission (Preamble) to inform that the mobile station transmits normally. The mobile station which has transmitted the message of step 1110 transmits the message of step 1111 to the synchronous base station.

The step 1211 message is a handoff completion message indicating that the mobile station has completed the handoff to the synchronization base station. In FIG. 12, the synchronous base station receiving the step 1211 message knows that the handoff of the mobile station has been completed successfully.

As described above, in the forward channel structure of the conventional synchronous mobile communication system, the mobile station receives at least three or more 80 msec sync frames transmitted on the forward sync channel of the synchronous mobile communication system in order to obtain system information of the synchronous mobile communication system. Should be. In the case of the synchronous mobile communication system having the channel structure as shown in FIG. 2 as an example, the minimum reception time is 240ms, during which the mobile station stops communicating with the asynchronous mobile communication system. That is, when the time for performing the process shown in FIG. 3 is long, there is a problem that may cause loss of communication data between the asynchronous mobile communication system and the mobile station.

Accordingly, an object of the present invention is to provide timing information of a synchronous system necessary for providing a successful handoff function to a terminal operating in an asynchronous mobile communication system, that is, a forward first auxiliary synchronization channel and a long code for generating a PN_OFFSET signal. A base station communication apparatus and method of a synchronous mobile communication system using a forward second auxiliary synchronization channel for generating status information and information for frame timing synchronization.

Another object of the present invention is to provide a channel transmission apparatus and method for generating information on a PN_OFFSET signal, a long code state, and frame synchronization information in a synchronization system.

It is still another object of the present invention to provide a mobile station with a forward first auxiliary synchronous channel for generating a PN_OFFSET signal and a forward second auxiliary synchronous channel for generating long timing information and frame timing synchronization information in a synchronous mobile communication system. An object of the present invention is to provide a handoff procedure and an apparatus that occurs when a mobile communication system moves from an asynchronous mobile communication system.

It is still another object of the present invention to provide asynchronous mobile communication using a forward first auxiliary synchronous channel for generating a PN_OFFSET signal and a forward second auxiliary synchronous channel for generating long timing and frame timing synchronization information in a synchronous mobile communication system. An apparatus and method for reducing the time for a mobile station communicating in a system to collect information of a synchronous mobile communication system.

A base station communication apparatus of a synchronous mobile communication system according to an embodiment of the present invention for achieving the above object, the forward pilot channel generator for generating a pilot signal, the forward sync channel generator for generating a synchronization signal, and the PN_OFFSET signal of the base station A forward first auxiliary synchronous channel generator to be generated, a forward second auxiliary synchronous channel generator to generate long-signal information and frame timing synchronous information, a forward dedicated control channel generator to generate a control message of a dedicated channel, and voice And a forward dedicated base channel generator for generating a signal and a forward dedicated additional channel generator for generating packet data.

In addition, the handoff process of the asynchronous mobile communication system according to an embodiment of the present invention for achieving the above object is the handoff from the asynchronous mobile communication system to the asynchronous mobile communication system, the handoff from the asynchronous mobile communication system to the synchronous mobile communication system Characterized in that can be performed.

In addition, the mobile station communicating in the asynchronous mobile communication system according to an embodiment of the present invention to detect the pilot signal of the base station of the asynchronous mobile communication system and the pilot signal of the base station of the synchronous mobile communication system to achieve the above object It is characterized by being.

1 is a diagram illustrating a base station structure of a synchronous mobile communication system having two auxiliary synchronization channels according to the present invention.

2 is a diagram illustrating a base station structure of a conventional synchronous mobile communication system.

3 is a diagram illustrating a process of measuring information on a synchronous mobile communication system by a mobile station in communication in an asynchronous mobile communication system;

FIG. 4 is a diagram showing a detailed configuration of a forward first auxiliary synchronization channel and a second auxiliary synchronization channel generator in FIG. 1; FIG.

5 is a diagram showing the structure of data input to the forward first auxiliary synchronization channel generator and the second auxiliary synchronization channel generator;

FIG. 6 is an explanatory view of frame timing information which is part of the second forward auxiliary channel. FIG. 6 is a mismatch between an end call period and a frame period and 80mesc. The figure explaining the coincidence time in a unit boundary and the frame timing information value at this time

FIG. 7 illustrates a structure in which a first auxiliary synchronization channel frame is transmitted within one period of a PN code. FIG.

8 illustrates a handoff procedure of an asynchronous base station in accordance with the present invention.

9 illustrates a handoff procedure of a mobile station in accordance with the present invention.

10 is a diagram illustrating a handoff procedure of a synchronous base station according to the present invention.

11 illustrates base station pilot signal detection parameters used in an asynchronous base station in accordance with the present invention.

12 illustrates messages transmitted and received when a mobile station according to the prior art moves from an asynchronous base station to a synchronous base station.

13 is a diagram illustrating messages transmitted and received when a mobile station moves from an asynchronous base station to a synchronous base station when the first auxiliary synchronization channel is provided in the synchronous mobile communication system according to the present invention.

FIG. 14A illustrates a structure of auxiliary synchronization channels proposed in another embodiment of the present invention. FIG.

FIG. 14B is a diagram illustrating a timing at which a first auxiliary synchronization channel and a second auxiliary synchronization channel are transmitted in an embodiment of the present invention. FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible. In the following description, specific details such as the length of the frames transmitted to each channel, the coding rate, and the number of data and symbols output from the blocks of the respective channels are shown to provide a more general understanding of the present invention. It will be apparent to one of ordinary skill in the art that the present invention may be readily practiced without these specific details and also by their modifications.

First Auxiliary Synchronization Channel used in the following description means a forward channel of a base station of a synchronous mobile communication system transmitting a message including PN_OFFSET information.

In addition, the term "PN_OFFSET information" used in the embodiment of the present invention means a message transmitted through the first auxiliary synchronization channel, and a message transmitted through the first auxiliary synchronization channel is used by a synchronous mobile communication base station. Is an offset value of a pseudo noise code having a period of 26.6 ... msec.

The term Second Auxiliary Synchronization Channel used in the following description is 80 msec for long code state information and frame synchronization. A forward channel of a base station of a synchronous mobile communication system in which a message including boundary information is transmitted.

In addition, the term "long code state value" used in the embodiment of the present invention means a part of a message transmitted through the second auxiliary synchronization channel, and a long time after receiving the second auxiliary synchronization channel. Sign generator status. Also, the term "frame synchronization information" means that the end call period (26.666 .. msec) and the call channel frame period (20 msec) are different so that the starting timing found from the LCM between the two periods coincides, for example, the existing system. 80 msec. By notifying the boundary, it plays a role of informing the call channel frame timing to the terminal, which only knew the end call cycle. That is, 80 msec by counting the end arc period from 0 to 2. 80 msec. It means a message that provides the boundary, that is, the moment when the counting value returns from 2 to 0 as the start of the frame without the frame offset (see FIG. 6). Can be.

1 is a diagram illustrating each channel configured in a mobile station and a base station in a code division multile access (CDMA) communication system, which is one of synchronous mobile communication systems according to an exemplary embodiment of the present invention, and a configuration of each channel transceiver An example is shown. In FIG. 1, each channel configuration is shown around the transmitter.

First, the channel configuration of the base station, the controller 101 performs the function (enable, disable) to control the operation of each channel generator of the base station, and processes the messages of the physical layer (physical layer) transmitted and received from the base station, It is responsible for communicating messages. The pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, the second auxiliary synchronization channel generator 106, the paging channel generator 107 share common channel information commonly used by users in one cell or multiple cells. The dedicated control channel generator 102, the basic channel generator 108, and the additional channel generator 109 are apparatuses for generating subscriber-specific channel information allocated differently for each user.

The dedicated control channel generator 102 is responsible for processing and transmitting various control messages transmitted through a dedicated control channel (DCCH) of the forward link to the terminal. Messages transmitted through the dedicated control channel of the forward link are RLP (Radio Link Protocol) frames or various control messages (L3 signaling) used in the IS-95B, packet data such as allocating additional channels and releasing additional channels. It consists of a MAC (Medium Access Control) message, which is a control message related to service control. When the base channel is not used, the power control signal may be transmitted through a dedicated control channel. In this case, the control message may include the power control signal. In addition, in the forward dedicated control channel, a data rate to be used for the base station and the additional channel is negotiated, and when the orthogonal code is used for the additional channel, a command for changing the orthogonal code is also issued. In the dedicated control channel of the forward link, an unused orthogonal code among the orthogonal codes not assigned to the pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, the second auxiliary synchronization channel generator 106, and the paging channel generator 107 is used. Assign one to spread. The RLP frame provides a service capable of transmitting octet streams well. RLPs can be divided into transparent RLPs and non-transparent RLPs. Transparent RLP does not retransmit erroneously transmitted frames, but informs the upper layer of the time and location of erroneously transmitted frames. Non-transparent RLPs provide error correction.

The pilot channel generator 103 is responsible for processing and transmitting the information transmitted through the pilot channel (pilot channel) of the forward link to the terminal. The pilot channel of the forward link always transmits a logic signal 0 or 1 (all 0's or all 1's). In this case, it is assumed that 0 logic signal is output to the pilot channel. The pilot channel signal allows the terminal to quickly acquiesce a new multipath and to estimate the channel. The pilot channel signal is spread by assigning one predetermined orthogonal code to a pilot channel.

The sync channel generator 104 is responsible for processing and transmitting information transmitted through a sync channel of a forward link to the terminal. Information transmitted through the synchronization channel is information for allowing terminals in a cell to match initial time synchronization and frame synchronization. A predetermined predetermined Walsh code is assigned to the sync channel of the forward link to spread the information of the sync channel.

The first auxiliary synchronization channel generator 105 is responsible for processing and transmitting the information transmitted through the first short synchronization channel of the forward link to the terminal. The information transmitted through the first auxiliary synchronization channel is a value of K1 bits having a size such that a terminal communicating in a base station of an asynchronous mobile communication system can quickly search for information of a base station of a synchronous mobile communication system. The information represented is a PN_OFFSET value, a zero padding bit, and a header bit for determining the start of a message of a synchronous mobile communication base station. The information is transmitted N ₂ times in the PN end call period so that the terminal communicating in the base station of the asynchronous mobile communication system can obtain the information quickly. K and N ₂ are shown in Figs. 5 and 6, respectively. The information is received by the terminal communicating in the asynchronous mobile communication system within the PN end call period and transmitted to the base station of the asynchronous communication system. The transmitted information allows the base station of the asynchronous mobile communication system to update the information about the cells around the base station. The information is also used for handoff that occurs when a terminal communicating in an asynchronous mobile communication system moves to a base station of a synchronous mobile communication system. In addition to the information, information of a base station of a synchronous mobile communication system transmitted through a synchronous channel is transmitted from a base station of an asynchronous mobile communication system to a terminal using a paging channel or a broadcasting channel. The terminal receiving the information transmitted from the first auxiliary device channel moves in a situation in which the system information of the synchronous mobile communication base station that moves when moving to the synchronous mobile communication system base station can communicate without a separate synchronization process. The information transmitted in the first auxiliary synchronization channel is allocated with one predetermined specific Walsh code that is identically used in all systems to spread the information of the first auxiliary synchronization channel.

The second auxiliary sync channel generator 106 is responsible for processing and transmitting information transmitted through the second auxiliary sync channel of the forward link to the terminal. The information transmitted through the second auxiliary synchronization channel has a size that enables the terminal communicating in the base station of the asynchronous mobile communication system to search for the long encoder and frame synchronization information quickly after handing off to the synchronous mobile communication system. The information represented by the value is long code state information of a synchronous mobile communication base station and PN period count information for frame synchronization. The information is transmitted one or more times in the PN end call period so that the mobile station communicating in the base station of the asynchronous mobile communication system can obtain the information quickly. The information is received by the mobile station communicating in the asynchronous mobile communication system within the PN end call period and transmitted to the base station of the asynchronous communication system. The transmitted information is used by the mobile station to communicate with the asynchronous mobile communication system in the handoff process, receive a handoff instruction to the synchronous base station, and move to the basic frequency band of the synchronous base station to obtain the long code synchronization and adjust the frame synchronization. Since the second auxiliary synchronization channel is transmitted by the end call cycle like the first auxiliary synchronization channel, communication can be performed without a separate synchronization process. The Walsh code used to spread the information transmitted on the second auxiliary synchronization channel and distinguish the channels may be allocated to a predetermined predetermined Walsh code that is identically used in all systems, or an asynchronous base station for efficient use of the Walsh code. Only when there is a handoff request from the mobile station, a Walsh code that is temporarily not used is allocated and transmitted, and then, after the handoff is completed, the channel is released to use the Walsh code used for another channel.

The paging channel generator 107 is responsible for processing and transmitting the information transmitted through the paging channel (paging channel) of the forward link to the terminal. The information transmitted on the paging channel is all the information needed before the communication channel is established. The paging channel of the forward link selects and spreads one of predetermined orthogonal codes.

The base channel generator 108 is responsible for processing and transmitting the information transmitted through the fundamental channel of the forward link to the terminal. Information transmitted on the base channel of the forward link is basically a voice signal. In addition, the information transmitted through the basic channel of the forward link may include various control messages (L3 signaling) and power control signals used in the IS-95B in addition to the voice signal. In addition, if necessary, a signal transmitted through the base channel of the forward link may include an RLP frame and a MAC message. The base channel uses a data rate of 9.6 kbps or 14.4 kbps, and depending on the situation, 4.8 kbps or 7.2 kbps having a rate of 1/2 of a given data rate may be used. 2.4 kbps or 3.6 kbps with a rate of 4 may be used, and a variable rate that may use 1.2 kbps or 1.8 kbps with a 1/8 rate is used. This modified data rate should be detectable at the receiving end. The base channel generator 108 of the forward link is not used among the orthogonal codes not assigned to the pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, the second auxiliary synchronization channel generator 106, and the paging channel generator 107. One orthogonal code is assigned to spread the base channel signal.

The additional channel generator 109 is responsible for processing and transmitting the information transmitted through the supplemental channel of the forward link to the terminal. Information transmitted through the additional channel of the forward link is an RLP frame, packet data, and the like. The additional channel generator 109 has a data rate of 9.6 kbps or more. The additional channel generator 109 has a scheduled data rate. As described above, the scheduled rate means that the base station and the terminal negotiate through the dedicated control channel to communicate at a data rate determined by the base station. The additional channel generator 109 of the forward link is not used among the orthogonal codes not assigned to the pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, the second auxiliary synchronization channel generator 106, and the paging channel generator 107. One orthogonal code is allocated and spreads an additional channel signal. In this case, the basic channel and the additional channel become a communication channel.

The adder 110 includes the I-channel transmission signals of the forward link output from the dedicated control channel generator 102, the basic channel generator 108, and the additional channel generator 109, the pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, The transmission signals output from the second auxiliary synchronization channel generator 106 and the paging channel generator 107 are added and output. The adder 111 adds and outputs Q channel transmission signals output from the dedicated control channel generator 103, the basic channel generator 108, and the additional channel generator 109. The spreading modulator 112 performs a function of multiplying the spreading signal output from the adder 110 and the adder 111 by the spreading sequence, and then up-converting the frequency of the transmitting signal to transmit the spreading signal. The receiver 113 receives respective channel signals of the terminal received on the reverse link, converts frequencies into base bands, and multiplies them by a spreading sequence to despread. In FIG. 1, the configuration of the channel receivers of the reverse link provided in the base station is omitted.

Second, referring to the configuration of the terminal, the controller 114 performs a function of controlling (enable, disable) the operation of each channel generator of the base station, processes the message of the physical layer (physical layer) transmitted and received from the terminal, the upper layer It is in charge of communicating messages with the user.

The dedicated control channel generator 115 is responsible for processing and transmitting various control messages transmitted through the dedicated control channel of the reverse link to the base station. The messages transmitted through the dedicated control channel of the reverse link include RLP (Radio Link Protocol) frames or various control messages (L3 signaling) used in the IS-95B, and a response to allocating additional channels and releasing additional channels. It consists of Medium Access Control (MAC) messages with contents. The dedicated control channel of the reverse link does not transmit the power control signal since the power control signal is inserted into the pilot channel and transmitted. It also negotiates the data rate to be used for the additional channel with the base station in the reverse dedicated control channel. The dedicated control channel generator 115 of the reverse link is pre-determined and spreads by orthogonal codes assigned to each channel to distinguish each channel and spreads to different user-assigned PN codes to distinguish users. In this case, the orthogonal codes are used to distinguish the channels. Therefore, different orthogonal codes predetermined for the dedicated control channel, pilot channel, access channel, basic channel, and additional channel are used. Use the same. For example, the orthogonal code used for the dedicated control channel means that all users use the same orthogonal code to distinguish the dedicated control channel.

In the dedicated control channel of the reverse link, the data rate is fixed at 9.6 kbps and transmitted. By fixing the data rate to 9.6kbps, the complexity of the receiver can be reduced by eliminating the performance due to data rate determination or the need for a data rate determination circuit. In addition, by having the same data rate as the basic data rate of the voice signal 9.6kbps has the advantage of maintaining the same service radius as the basic voice service.

The pilot channel generator 116 is responsible for processing and transmitting the information transmitted on the pilot channel of the reverse link to the base station. The pilot channel signal of the reverse link, like the pilot channel signal of the forward link, enables fast initial synchronization for a new multipath and also enables channel estimation. While transmitting the power control signal at a certain point in time to transmit the reverse power control information.

The access channel generator 117 is responsible for processing and transmitting the information transmitted through the access channel (access channel) of the reverse link to the base station. The message of the access channel signal is composed of all information and control messages of the terminal required by the base station before the communication channel is established.

The base channel generator 118 is responsible for processing and transmitting information transmitted through a fundamental channel of the reverse link to the base station. Information transmitted on the base channel of the reverse link is basically a voice signal. In addition, the information transmitted through the base channel of the reverse link may include various control messages (L3 signaling) used in the IS-95B in addition to the voice signal. In addition, if necessary, a signal transmitted through the base channel of the reverse link may include an RLP frame and a MAC message. In the reverse link, the power control signal is transmitted through the pilot channel, so the power control signal is not transmitted through the base channel. The base channel uses a data rate of 9.6 kbps or 14.4 kbps, and depending on the situation, 4.8 kbps or 7.2 kbps having a rate of 1/2 of a given data rate may be used. 2.4 kbps or 3.6 kbps with a rate of 4 may be used, and a variable rate that may use 1.2 kbps or 1.8 kbps with a 1/8 rate is used. This modified data rate should be detectable at the receiving end. The base channel generator 118 of the reverse link is pre-determined and spread with an orthogonal code assigned to each channel to distinguish each channel and distinguish a user with a PN code differently assigned to each user. In this case, the orthogonal codes are used to distinguish the channels. Therefore, different orthogonal codes predetermined for the pilot channel, the access channel, the basic channel, and the additional channel are used, and each orthogonal code used for each channel is the same for all users. . For example, the orthogonal code used for the basic channel means that all users use the same orthogonal code to distinguish the basic channel.

The additional channel generator 119 is responsible for processing and transmitting information transmitted through the supplemental channel of the reverse link to the base station. Information transmitted through the additional channel of the reverse link is an RLP frame, packet data, and the like. The additional channel generator 119 has a data rate of 9.6 kbps or more. The additional channel generator 118 has a scheduled data rate. As described above, the scheduled rate means that the base station and the terminal negotiate through the dedicated control channel to communicate at a data rate determined by the base station. The additional channel generator 119 of the reverse link is pre-determined and spread with an orthogonal code assigned to each channel to distinguish each channel and distinguish a user by a PN code differently assigned to each user. In this case, the basic channel and the additional channel become a communication channel.

The adder 120 adds and outputs transmission signals of the reverse link output from the dedicated control channel generator 115 and the pilot channel generator 116. The adder 121 adds and outputs the transmission signals of the reverse link output from the access channel generator 117, the base channel generator 118, and the additional channel generator 119. The spreading modulator 122 performs a function of multiplying and spreading the transmission signals of the reverse link output from the adder 120 and the adder 121 by a spreading sequence, and then up-converting and transmitting the frequency of the transmission signal. The receiver 123 receives respective channel signals of the base station received on the reverse link, converts frequencies into base bands, and multiplies them by a spreading sequence to despread. In FIG. 1, the configuration of the channel receivers of the forward link provided in the terminal is omitted.

As shown in FIG. 1, in a CDMA communication system according to an exemplary embodiment of the present invention, a base station includes a controller 101 for controlling all channels, a dedicated control channel generator 102 for processing signals transmitted through each channel, and a pilot channel generator 103. And a synchronization channel generator 104, a first auxiliary synchronization channel generator 105, a first auxiliary synchronization channel generator 106, a paging channel generator 107, a basic channel generator 108, and an additional channel generator 109. The terminal also includes a controller 114, a dedicated control channel generator 115, a pilot channel generator 116, an access channel generator 117, a basic channel generator 118, an additional channel generator 119. In addition, when the output form of each channel generator, the signals transmitted from the dedicated control channel generator 102, the basic channel generator 108, the additional channel generator 109 of the base station is I-channel (In-phase channel) component and Q channel (Quadrature-phase channel) Although two channel signals are generated, the pilot channel generator 103, the synchronization channel generator 104, the first auxiliary synchronization channel generator 105, the second auxiliary synchronization channel generator 106, and the paging channel generator 107 generate only one channel component. . In this case, it is assumed that components generated by only one channel are output as I channel (Inphase channel) components only.

Each channel of the terminal outputs one channel component differently from the channels of the base station. Therefore, the outputs of the dedicated control channel generator 115 and the pilot channel generator 116 of the terminal are added to the I-channel (in-phase channel) input of the spreading modulator 122, and the outputs of the remaining channels 117, 118, and 119 are added to the spreading modulator 122. Q channel (Quadrature-phase channel) input. Since the access channel generator 117 generates an output before the communication channel is generated, when using the access channel, the output of the pilot channel generator 116 is an I channel input, and the output of the access channel generator 117 is a Q channel input.

Detailed configuration and operation of all channel transmitters except for the first auxiliary synchronization channel transmitter and the second auxiliary synchronization channel transmitter in FIG. 1 are described in detail in Korean Patent Application No. 98-11381 filed by the present applicant.

The present invention first describes the detailed configurations of the first auxiliary synchronization channel and the second auxiliary synchronization channel transmitter, and then, in the procedure for performing handoff from the asynchronous mobile communication system to the synchronous mobile communication system according to an embodiment of the present invention. Explain.

4 illustrates a detailed configuration of the first auxiliary sync channel transmitter 105 and the second auxiliary sync channel transmitter 106 according to an embodiment of the present invention.

Referring to FIG. 4, the encoder 401 encodes and inputs the first auxiliary synchronization channel data (or second auxiliary synchronization channel data). The encoder 401 may use a convolutional encoder or a turbo encoder. In FIG. 4, it is assumed that the encoder 401 uses a convolutional encoder having a code rate of 1/2 and a constraint length of 9. The iterator 402 repeatedly outputs the symbols output from the encoder 401 by N times. The interleaver 403 interleaves and outputs the symbols output from the iterator 402 to prevent the occurrence of a burst error. The interleaving may be omitted in the first auxiliary synchronization channel in order to reduce the time required for message detection of the first auxiliary synchronization channel. The interleaver may be a block interleaver, a turbo interleaver, or the like. The signal converter 404 converts the level of the auxiliary synchronization channel signal output from the interleaver 403. The multiplier 405 multiplies the orthogonal code by the synchronization channel signal output from the signal converter 404 and orthogonal modulates. The orthogonal code used in the multiplier 405 promises one of the Walsh codes in advance. The Walsh code used in the multiplier 405 should be only one specific Walsh code used in the synchronous mobile communication system. The length of the Walsh code used in the multiplier 405 uses the length specified in the synchronous mobile communication system. For example, Walsh codes of length 128 in IMT2000 SR1 and 256 in IMT2000 SR3 are used. The encoders 401, repeaters 402 and interleaver 403 used in FIG. 4 are optional, not essential, types of encoders 401, repeaters 402, interleaver 403 are also optional, and transmitters 105 and 106 are selectively implemented according to circumstances. In FIG. 4, various types of information input to the first auxiliary synchronization channel generator 105 or the second auxiliary synchronization channel generator 106 may be provided. For example, a method of transmitting only the transmission information (PN_OFFSET in the case of the first auxiliary synchronization channel, long code state value and frame timing related information in the second auxiliary synchronization channel), and a method of attaching a CRC to the back of the "transmission information" value. And a method of encoding and transmitting the " transmission information " by a separate encoding scheme, and transmitting the " header bit + transmission information + CRC " in order to detect the transmission information within a short time without depending on the end code cycle. And the like.

FIG. 5 is a diagram showing a frame structure of information input to the first auxiliary synchronization channel generator 105. FIG. Referring to FIG. 5, information 501 input to the first auxiliary synchronization channel generator 105 is PN_OFFSET information of a base station of a synchronous mobile communication system. The PN_OFFSET information is represented by K bits, and FIG. 5 shows an example in which the PN_OFFSET information, the Zero Pading Bit, and the header bit are K bits, and CRC502 is attached during transmission. In the current synchronous mobile communication system, PN_OFFSET is an integer between 0 and 511, and 9 bits are used. In this case the number of bits in the header will be 10. The data rate and the length of the CRC of the information input to FIG. 5 may be used differently depending on the Walsh code length, the number of repetitions, and the type of encoder.

In addition, in the case of the second auxiliary synchronization channel, the input information includes a long code state value and frame timing information. The long code state value indicates the state of the long code generator in the terminal after a certain end code period (26.6666 .. * integer msec), which is represented by 41 bits in the current synchronous mobile communication system. On the other hand, since the frame synchronization timing is different between the end call period (26.666 .. msec) and the call channel frame period (20msec), the end-call is notified by informing the boundary of the least common multiple between the two periods, for example, 80 msec. It plays a role of informing the call channel frame timing to the terminal that only knew the period.

Figure 6 shows the timing difference between this end call period and the call channel frame. Where the least common multiple between the end call period and the frame period, i.e. 80 msec. It can be seen that the starting point of the zero offset end call and the call channel frame coincide with each boundary. Accordingly, the frame information timing of the second auxiliary synchronization channel may indicate that the timing coincides with the instant of changing the value from 2 to 0 by repeating the value between 0 and 2 by increasing the count value for each end call period. In this case, the frame timing information consists of 2 bits. As another example, one bit may be configured by transmitting another binary signal, that is, 1 or 0 only at the 80 msec boundary in which timing matches, and vice versa in the remaining period.

FIG. 7 illustrates a structure in which a first auxiliary synchronization channel frame is transmitted within one period of a PN code.

Referring to FIG. 7, the first auxiliary synchronization channel frame is transmitted N ₂ (N ₂ ≥ 1) times within one period of the PN end call. That is, several transmissions are possible instead of one transmission of PN_OFFSET information within one period of PN code. Therefore, the terminal communicating with the base station of the asynchronous mobile communication system can acquire the information of the base station of the synchronous mobile communication system in a short time.

Equation 1 shows a method of determining the transmission frequency N ₂ of the first auxiliary synchronization channel frame.

N_chip = {(K + CRC) × R × N ₁ × W ^l } × N ₂

If the variable used in <Equation 1> is defined as follows.

N_chip = Number of chips in one cycle of PN code (32768 if SR1, 98304 if SR3)

K = data bit (Header bit + PN_OFFSET value + zero padding bit length)

The use of the header bit and zero padding bit is optional.

CRC = CRC bit used in the 1st auxiliary synchronization channel

R = code rate of encoder used in the 1st auxiliary synchronization channel generator

N ₁ = number of symbol repetitions

W ^l = length of the Walsh code

N ₂ = Number of PN_OFFSET FRAME transmissions during one cycle of PN end call

For example, if 9 bits of PN_OFFSET and N_chip = 32768, R = 2, N ₁ = 2, W ^l = 128 are set in the current synchronous mobile communication system, 64 = (K + CRC) × N ₂ The bit rate of the first auxiliary synchronization channel is 2400 bps. To repeat the frame of the first auxiliary synchronization channel twice, K + CRC must be 32 bits. If the CRC bit is used 20 without using the header bit, K includes 9 bits of PN_OFFSET value and 1 bit of zero fading and may be set to 10 bits.

As another example, if 9 bits of PN_OFFSET and N_chip = 32768, R = 2, N ₁ = 2, W ^l = 128 are currently used in the synchronous mobile communication system, 64 = (K + CRC) × N ₂ The bit rate of the first auxiliary synchronization channel is 2400 bps. In order to repeat the frame of the first auxiliary synchronization channel four times, K + CRC should be 16 bits. If 4 bits are used for the CRC bit, K may be set to 12 bits including 9 bits of PN_OFFSET value and 3 bits of zero fading.

Hereinafter, a procedure for performing handoff from an asynchronous mobile communication system to a synchronous mobile communication system according to an exemplary embodiment of the present invention will be described. In the following description, a base station of the asynchronous mobile communication system is called an asynchronous base station, and a base station of the synchronous mobile communication system is called a synchronous base station. 8, 9 and 10, soft handoff is used between the asynchronous base station and the asynchronous base station. In addition, the synchronous base station of the synchronous mobile communication system in the following description is a base station having the channel structure of FIG.

8 is a diagram illustrating a handoff procedure of an asynchronous mobile communication system base station capable of handoff to a synchronous mobile communication system.

Referring to FIG. 8, the asynchronous base station A receives pilot signal measurement results of neighboring asynchronous base stations from the mobile station B in step 801. The process of finding the asynchronous base station to be handed off by the mobile station B is to measure the pilot signal strengths of the asynchronous base stations around the asynchronous base station without any report to the asynchronous base station A and to find the asynchronous base station having a pilot signal of a predetermined value or more. Report to Station A. Then, the asynchronous base station A determines whether there is an asynchronous base station to which the mobile station B is to be handed off, based on the measurement result received from the mobile station B in step 802. If the mobile station B determines that there is an asynchronous base station to be handed off, the asynchronous base station A proceeds to step 803 and transmits a handoff direction necessary for handoff to the mobile station B. On the other hand, if the mobile station B determines that there is no asynchronous base station to be handed off, the asynchronous base station A proceeds to step 804 to determine the pilot signal detection parameters (T, T ₀ , N) of the mobile station B for the neighboring base station cell. Set it. Here, the pilot signal detection parameter for the synchronous base station cell is shown in FIG. As shown in FIG. 11, T ₀ is a time for detecting a pilot signal of a synchronous base station, T is a time interval for detecting a pilot signal of a synchronous base station, and N is how many times to find a pilot signal of a synchronous base station. This parameter defines.

In step 805, the asynchronous base station A transmits the set parameter to the mobile station B, and transmits a message for measuring the pilot signal strength for the synchronous base stations and the asynchronous base station around the asynchronous base station A. Then, the mobile station B detects the pilot signal of the synchronization base station during the determined parameter T ₀ , and detects the pilot signal of the asynchronous base station and communicates with the asynchronous base station during (TT ₀ ) time. Thereafter, the asynchronous base station A receives the pilot signal measurement result from the mobile station B in step 806. Here, the pilot signal measurement results transmitted from the mobile station B to the asynchronous base station A can be classified into four types. That is, information for finding another asynchronous base station to be handed off, information for finding a synchronous base station to be handed off, information for finding another asynchronous base station to be handed off, and information for not finding a base station to be handed off. Among the information, the information found for the synchronization base station is transmitted together with the system information for the synchronization base station. Here, the system information of the synchronization base station is of two types, one of which is the PN_OFFSET information of the synchronization base station when the synchronization base station having the first auxiliary synchronization channel as shown in FIG. 1 is found, and the synchronous mobile communication system as shown in FIG. When is found, it is the synchronization message of the synchronization base station received through the synchronization channel.

Upon receiving the pilot signal measurement result from the mobile station B, the asynchronous station A determines whether there is a target cell to hand off in step 807. At this time, when it is determined that there is no target cell to be handed off, the asynchronous station B returns to step 801 to perform the following process again. On the other hand, when the target cell to be hand-hop is found, the asynchronous base station A determines whether the target cell is an asynchronous base station or a synchronous base station in step 808. That is, since the asynchronous base station A measures both pilot signals of the asynchronous base station and the synchronous base station when setting parameters in step 804, it is necessary to determine whether the target cell found in step 808 is a synchronous base station or an asynchronous base station. In addition, if the synchronous base station and the asynchronous base station are found at the same time, which base station is to be hand hoped is a system setting parameter of the asynchronous base station A. Which base station should be given priority may be set in the system of the asynchronous base station A.

If it is determined in step 808 that the target cell to be hand hoped is an asynchronous base station, the asynchronous base station A proceeds to step 809 and transmits information (Handoff Direction) necessary for handoff to the asynchronous base station to the mobile station A. On the other hand, when the cell to be hand-hop is determined to be a synchronous base station, the asynchronous base station A reports in step 806 the PN_OFFSET information or the system information of the synchronous base station pilot signal received from the mobile station B and the received synchronous base station to the higher network. . In step 810, the asynchronous base station A receives a request to handoff the mobile station B to the synchronization base station from the upper network. In this case, when handoff is performed to the synchronization system of FIG. 1, system information is received together. During step 810, the higher level network transmits information to the synchronous base station to be handed off that the mobile station B will be handed off. The reception target of the information may be a synchronization base station or a higher network of the synchronization base station. The asynchronous base station A, which has received a handoff request from the upper network, transmits information (Handoff Direction) necessary for handoff to the determined base station cell to the mobile station B.

As another embodiment, the asynchronous base station A may omit step 804 in the process of FIG. 8, and perform step 807 directly from the moment the mobile station B moves to the cell of the asynchronous base station A. FIG. The other embodiment has the advantage that the asynchronous base station A can shorten the time for handing off the mobile station B.

9 is a diagram illustrating a procedure in which a mobile station B communicating with an asynchronous base station B performs handoff. In FIG. 9, mobile station B is assumed to be a dual mode capable mobile station capable of communicating with the asynchronous base station and the mobile base station.

Referring to FIG. 9, the mobile station B measures the pilot signal received in step 901 and transmits the measurement value to the asynchronous base station A. Here, the mobile station B transmits a message indicating that it has found an asynchronous base station to be handed off if it finds another asynchronous base station to be handed off, and transmits a message notifying that it has not been found. After receiving the response of the asynchronous base station B in step 901, the mobile station B checks in step 902 whether the response is a handoff request to the asynchronous base station target cell. If the mobile station B receives the handoff message (the message transmitted in step 803 of FIG. 8) from the asynchronous base station A to the target cell of the asynchronous base station in step 902, the mobile station B proceeds to the target cell of the asynchronous base station. Perform a handoff. In step 904, the mobile station B transmits a reverse transmission signal to the asynchronous base station which is the target cell. Thereafter, in step 905, a handoff complete message is transmitted to the asynchronous base station, which is the target cell, to inform that the handoff has been successfully performed.

On the other hand, the mobile station B that has not received the handoff message receives the pilot signal detection parameters of the asynchronous base station and the synchronous base station in the vicinity of the asynchronous base station A in step 906. The received parameters are values defined in FIG. 11. In setting the parameters received in step 906, it should be noted that if the time of T ₀ for locating the pilot signal of the synchronization base station is too long, there is a problem in the stability of communication with the asynchronous base station. If the interval of T is too long, the synchronization base station When N is large, difficulty in detecting a pilot signal occurs, and when N is large, the time for searching for a base station (synchronous base station or asynchronous base station) to be handed off is long, and the time for handoff of the mobile station B is missed, resulting in disconnection of a call.

In step 907 to step 913, the mobile station B detects the pilot signal strength of the synchronous base station during the time T ₀ for N times and detects the pilot signal of the asynchronous base station for the time TT ₀ . The process of communicating with an asynchronous base station. In FIG. 9, the mobile station B performs step 908 for a time of T ₀ and step 910 for (TT ₀ ). In step 908, a pilot signal of the synchronization base station is detected. In step 908, there are two methods for detecting a pilot signal of the synchronization base station. In order to detect the synchronization signal directly during the time of T ₀ and to ensure the stability of the call between the asynchronous system A and the mobile station B, set T ₀ to a small value and store the signal transmitted from the synchronization base station in the buffer of the mobile station B. This method detects the pilot signal of the synchronization base station from the signal stored in the buffer for (TT ₀ ) time. If the pilot signal of the synchronous base station is detected in step 908, the mobile station B performs step 909.

The mobile station B interprets the system information from the synchronization channel of the synchronization base station or the first auxiliary synchronization channel in step 909. In case of using the method of directly detecting the synchronization signal during the time T ₀ in step 909, the mobile station B performs a channel with the synchronization base station for a time sufficient to obtain system information of the synchronization base station at the time when the pilot signal of the synchronization base station is detected. It shall be maintained and shall not return to the channel with the asynchronous base station. However, with the signals stored in the buffer in the step 908, if using the method for detecting a pilot signal of the sync base station in the next T ₀ of the T ₀ stores the pilot signal of the sync base station can obtain the system information of the synchronous base stations sufficiently Maintain channel with synchronization base station for time. In addition, if the mobile communication system does not have the first auxiliary synchronization channel, the mobile station B should receive the synchronization message transmitted to the synchronization channel of the synchronization base station for at least 240 ms in step 909. Therefore, in order to obtain the information necessary for handoff in the mobile communication system without the first auxiliary synchronization channel as described above, it may not be possible to ensure stability in the call between the mobile station B and the asynchronous base station A. On the other hand, in the synchronous mobile communication system composed of the system of FIG. 1, the mobile station B transmits to the first auxiliary synchronization channel in a relatively short time (less than 26.666 / N ₂ ms if there is no reception error) in step 909. Receive PN_OFFSET information.

In step 910, the mobile station B measures the asynchronous base station pilot signal strength around the base station A and maintains a call with the asynchronous base station A at (TT ₀ ) time. In step 911, it is determined whether the pilot signal strength of the asynchronous base station measured in step 910 is an appropriate value for handoff. At this time, when detecting the pilot strength suitable for handoff, the mobile station B proceeds to step 913; otherwise, the mobile station B proceeds to step 912. If the mobile station B does not detect the pilot signal of the synchronous base station or the asynchronous base station that can be handed off in steps 908 and 910, the mobile station B counts the number of executions in step 912 to exceed N trials. To judge. If the number of times N has not been exceeded in step 912 and the pilot signal of the synchronous base station or the pilot signal of the asynchronous base station is not detected, the mobile station B returns to step 907 and repeats steps 908 and 910. On the other hand, if the number of times N is exceeded in step 912, the measurement result up to that point is transmitted to the asynchronous system A in step 913. If a signal is detected in step 908 within the N number of trials, and step 909 is performed, the mobile station B immediately performs step 913. In addition, if a signal is detected in step 910 within the N number of trials, and it is determined in step 911 that the base station has the appropriate pilot signal strength, the mobile station B immediately performs step 913. The mobile station B transmits to the asynchronous base station A the measurement result of the received signal strength of the pilot signal detected from the synchronous base station and the asynchronous base station in step 913.

The mobile station B determines whether to receive a handoff message from the asynchronous base station A in step 914. In this case, if the handoff message is not received, the process returns to step 902 and repeats the following steps. If the handoff message is received, the process proceeds to step 915 and the handoff message received from the asynchronous base station A is transferred to the synchronization cell. It is determined whether the message is a handoff message or a handoff message to an asynchronous cell. In this case, if the message received in step 914 is a handoff message to the asynchronous cell, the mobile station B performs steps 921, 922, and 923. If it is determined in step 915 that the handoff message is a handoff message to a synchronization cell, the mobile station B proceeds to step 916. The mobile station B moves to the target cell using the system information of the synchronous mobile communication base station included in the handoff message received in step 914 in step 916. The mobile station B receives the second auxiliary synchronization channel from the synchronous mobile communication system base station C in step 917 to obtain the long code state and the frame timing information. In step 919, the mobile station B initializes the long code generator from the obtained long code state, establishes a call channel from the obtained frame timing, and normally receives the call channel of the synchronous mobile communication base station. In step 919, the mobile station B transmits a reverse signal to the synchronous base station C on the reverse base channel. In step 920, the mobile station B transmits a handoff complete message through the reverse base channel. To send.

FIG. 10 illustrates a procedure of performing a handoff for a mobile station from a base station of a synchronous mobile communication system using the system of FIG.

Referring to FIG. 10, in step 1001, the synchronous base station C transmits a pilot signal through a pilot channel and transmits PN_OFFSET information of the base station C through a first auxiliary synchronization channel. The PN_OFFSET information of the base station C transmitted through the first auxiliary synchronization channel may be transmitted as an example as shown in FIG. 5, or may be in various other forms. In addition, the first auxiliary synchronization channel generator may be configured as shown in Figure 4, the encoder, interleaver, repeater and the like used in Figure 4 is optional. Further, the information of the first auxiliary synchronization channel is 26.6... It is transmitted N ₂ times every ms. The synchronous base station C receives a handoff message from the higher network to base station C of the mobile station B in step 902. In step 1002, the synchronization base station C, which has received the handoff message from the mobile station B to the base station C, sets the second auxiliary synchronization channel and transmits a long code state and frame timing information. At this time, the second auxiliary synchronization channel information (frequency band, Walsh code) set for the asynchronous base station must also be transmitted to the mobile station together with the call channel information set at the time of handoff. Here, the second auxiliary synchronization channel may always be broadcast using a certain Walsh code, and these two methods are optional. In step 1004, the base station C transmits null traffic or other data to the mobile station B through a forward basic channel. Wherein step 100 is optional. When the mobile station B moves to the cell of the synchronous mobile communication base station C, the mobile station B first demodulates the second auxiliary synchronization channel and takes a predetermined time to set up the long code and align the framing synchronization point. Transmits the call channel to the mobile station B normally by using the forward basic channel. For example, when the second auxiliary synchronization channel is transmitted in one end of a call, demodulation of the second auxiliary synchronization channel and a longer code setup and frame timing alignment require 2 or 3 more cycles, so that a call channel may be set after about 80 msec. In step 1006, the synchronization base station C receives a Handoff Completion message from the mobile station B. After receiving the Handoff Completion message, the synchronous base station C may release the second auxiliary synchronous channel set when there are no mobile stations moving from the asynchronous base station A to the synchronous base station C in step 1007. Wherein step 1007 is optional.

FIG. 13 illustrates a handoff process performed when a mobile station moves from an asynchronous base station to a synchronization base station in a call channel control state when the synchronization base station includes a first auxiliary synchronization channel and a second auxiliary synchronization channel according to an embodiment of the present invention. It is a figure. In FIG. 13, it is assumed that the mobile station 13002 is handed off from the asynchronous base station 13001 to the synchronous base station 13003. 13 are messages transmitted and received between the asynchronous mobile communication system base station and the mobile station. Steps 1306 and 1312 are messages transmitted and received between the synchronous mobile communication system base station 13003 and the mobile station 13002. The message 1301 of FIG. 13, the message 1201 of FIG. 12, the message 1302 of FIG. 13, the message 1202 of FIG. 12, the message 1303 of FIG. 13, the message 1203 of FIG. 12, and the message 1304 of FIG. 12, 1204 message of FIG. 12, 1305 message of FIG. 13, 1205 message of FIG. 12, 1306 message of FIG. 13, 1206 message of FIG. 12, 1309 message of FIG. 13, 1208 message of FIG. The 1311 message of FIG. 13, the 1210 message of FIG. 12, the 1312 message of FIG. 13, and the 1211 message of FIG. 12 each perform the same function.

As described above, the asynchronous base station 13001 transmits information on other neighbor cells of the base station A to the mobile station through a broadcast channel in step 1301, and the mobile station 13002 receives pilot signals from the other neighbor base stations in step 1302. The measurement result is reported to the asynchronous base station 13001 through the reverse dedicated channel. There are two kinds of messages of the mobile station 13002 reported to the asynchronous base station 13001 in step 1302. The mobile station 13002 may send information indicating that it has found another asynchronous base station that can be handed off, or transmit information that no other asynchronous base station was found. In FIG. 13, assuming that the mobile station 13002 has transmitted a message indicating that it has not detected a pilot signal of another asynchronous base station, the asynchronous base station 13001 transmits a pilot signal for the synchronous base station and the asynchronous base station around the asynchronous base station 13001 to the mobile station 13002 in step 1303. A measurement is required, and the set parameters T, T ₀ , N are transmitted to the mobile station 13003 through the forward dedicated channel. On the other hand, the synchronization base station 13003 transmits a pilot signal through the forward pilot channel in step 1306, and simultaneously transmits PN_OFFSET information of the synchronization base station 13003 through the forward first auxiliary synchronization channel in step 1307. The mobile station 13002 receiving the message transmitted by the asynchronous base station 13001 in step 1303 measures the strength of the pilot signal for the other asynchronous base station and the synchronous base station around the asynchronous base station 13001 to obtain a pilot signal having the maximum size. In the present embodiment, it is assumed that the diok station 13002 acquires the signal of the synchronization base station 13003. Here, the mobile station 13002 obtains PN_OFFSET information of the synchronization base station 13003 transmitted through the first auxiliary synchronization channel of the synchronization base station 13003. In step 1304, the mobile station 13002 reports the PN_OFFSET information and the pilot signal measurement result of the synchronization base station 13003 to the asynchronous base station 13001. The message reported in step 1304 is transmitted to the upper network, and then a handoff command to the asynchronous base station 13003 is transmitted from the upper network to the asynchronous base station 13001. In addition, the system information for the synchronous base station 13003 is transmitted from the upper network to the asynchronous base station 13001. Along with this, information about a second auxiliary synchronization channel to be set to assist handoff is also transmitted. This operation is optional. If the second auxiliary synchronization channel is always broadcasted using the fixed Walsh code like the first auxiliary synchronization channel, this operation is not necessary and thus is not performed. In step 1305, the asynchronous base station 13001 transmits information necessary for handoff (including call channel information for system call, system information, and second auxiliary synchronization channel information if necessary) to the mobile station 13002 on the forward dedicated channel. Meanwhile, the synchronization base station 13003 receives a handoff command from the upper network to the base station 13003 of the mobile station 13002.

Then, the synchronization base station 13003 transmits the long code state and the frame timing information to the mobile station 13002 through the second auxiliary synchronization channel in step 1308 simultaneously with receiving the handoff command. In step 1309, the synchronous base station 13003 transmits null traffic to the mobile station 13002 through a forward basic channel. Thereafter, the mobile station 13002, which is out of the cell of the asynchronous base station 13001, moves to the cell of the synchronization base station 13003, and the synchronization base station 13003 has a short time delay in consideration of the reception time of the second auxiliary synchronization channel of the mobile station 13002, and then the forward basic Send traffic through the channel. That is, in step 1310, the synchronization base station 13003 receives the call between the asynchronous base station 13001 and the mobile station 13002, and the synchronization base station 13003 transmits the call channel to the mobile station 13002 normally. Thereafter, the mobile station 13002 transmits a reverse signal using a reverse base channel in step 1311, and transmits a handoff completion message to the synchronization base station 13003 in step 1312, indicating that the handoff is successfully completed. After receiving this signal, the synchronous base station 13003 may release the second auxiliary synchronization channel and the use of this operation is optional.

The difference between FIG. 13 and FIG. 12 lies in the manner in which the mobile station obtains system information of the synchronous mobile communication system.

The method of obtaining the system synchronization information of the base station 12003 by the mobile station 12002 shown in FIG. 12 is a method of receiving the synchronization signal frame of the base station 12003 for at least 240 ms and interpreting the synchronization signal message contained in the synchronization signal frame. However, in FIG. 13, the mobile station 13002 obtains system synchronization information from the base station 13003 by taking only PN_OFFSET information of the base station 13003 transmitted through the first auxiliary synchronization channel shown in FIG. And the base station 13001 receiving the received system synchronization information of the synchronous base station 13003 from its own network or from an upper network of the base station 13001. That is, this method is a method in which the mobile station 13002 finds the system synchronization information of the base station 13003 by using information about neighbor cells previously received from the base station 13001. In addition, time-limited information (long code state and frame timing information) to be transmitted through the network is received through the second auxiliary synchronization channel set by the synchronous base station separately after moving to the synchronous base station band.

13, the first auxiliary synchronization channel message received by the mobile station 13002 in step 1307 of FIG. 13 is PN_OFFSET information used by the synchronization base station 13003. I can see. In the embodiment of the present invention, it is assumed that the mobile station 13002 transmits the message received in step 1307 by the synchronous base station 13003.

As illustrated in FIG. 5, the message 1307 may be transmitted in various types of applications including PN_OFFSET information of the synchronous mobile communication base station 13003. The message of step 1307 of FIG. 13 can be repeatedly transmitted several times within the period (26.6 ... ms) of the PN Short Code as shown in FIG. Therefore, when the mobile station 13002 receives the PN_OFFSET information of the base station 13003, the time required is very small compared to the minimum time required for acquiring the mobile station system synchronization information shown in FIG.

The present invention proposes a method for assisting hard handoff from a system such as W-CDMA, GSM, AMPS, etc., which is not synchronized to the existing system by using an additional auxiliary synchronization channel in the existing IS-95 or IS-2000 system. . In the above embodiment, the base station includes two auxiliary synchronization channels, and the first auxiliary synchronization channel has information of the PN offset of the synchronized IS-95 base station, and the second auxiliary synchronization channel has the long code state of the synchronized IS-95. Send it. The second auxiliary synchronization channel transmits information for 80 ms synchronization. The above 80ms synchronization information means that one period of 26.7ms found by the mobile station through the search indicates which position of the 80ms period. However, the 80 ms synchronization information may be transferred to the first auxiliary synchronization channel to perform hard handoff.

14 (a) shows the structure of the auxiliary synchronization channels proposed in another embodiment of the present invention. The first synchronization channel transmits 80 ms synchronization information as well as PN offset information of the synchronized IS-95 system. The second synchronization channel transmits a long code state. CRC may be added to each auxiliary synchronization channel.

FIG. 14B illustrates timings of transmitting a first auxiliary sync channel and a second auxiliary sync channel in an embodiment of the present invention. The first auxiliary synchronization channel is transmitted after a time delay by a PN offset at an 80 ms reference time of a base station having a 0 PN offset. This is the same as the existing sync channel. This is because the mobile station cannot catch the 80 ms timing synchronization of the base station with zero offset until it knows the PN offset. In the embodiment of the present invention, it is assumed that the first auxiliary synchronization channel is repeated N1 times within 80 ms. If 64 chips are assumed to be one symbol, 512 symbols are transmitted within 80 ms, and the first auxiliary synchronization channel is repeatedly transmitted ^{512/2 S1_LENGTH} times with 2 ^S1_LENGTH symbol lengths. For example, the first synchronous channel has 32 symbol lengths, which are transmitted 16 times in 26.7 ms. In this case, information of 9 bits of information about the PN offset and 2 bits of information about 80 ms synchronization are encoded (a CRC of NUM_CRC1 bits may be added) to form a first synchronization channel having a length of 32 symbols.

The second auxiliary synchronization channel is synchronized with the 80 ms boundary of the base station with zero offset. The reason for the transmission is that the mobile station can receive the traffic channel immediately by loading only the initial state of the long code without receiving a time synchronization process after receiving the long code information. The second auxiliary synchronization channel can be encoded in units of 20ms, 40ms, 80ms or 26.7ms, and is encoded and interleaved within one frame.

The operation of the mobile station for the above embodiment is as follows. The mobile station acquires a signal of an adjacent base station through a search process and then receives a first auxiliary synchronization channel. After acquiring the pilot channel of the adjacent base station, the mobile station is already in sync with 26.7 ms and thus is in sync with the first auxiliary sync channel. The mobile station receives the first sync channel to obtain the information of the PN offset and then informs the base station of this. At this time, the 80ms synchronization information is acquired together to catch the 80ms synchronization. If the base station instructs the handoff to the handoff to the base station. In order to perform a handoff, you need to know the long sign status of the IS-95 system. For this purpose, the mobile station must receive a second auxiliary synchronization channel. The second synchronous channel is transmitted in synchronization with the 80 ms boundary of 0 offset and there is no problem in receiving it since the mobile station has already acquired this information through the first auxiliary synchronous channel. In this way, if the mobile station acquires 80 ms of synchronization in advance before the second auxiliary synchronization channel is acquired, the time used for hard handoff can be reduced.

As described above, according to the present invention, in a mobile communication system in which an asynchronous system and a synchronization system coexist, the synchronization system base station can acquire information on neighbor cells within a short time while transmitting the PN_OFFSET value through the first auxiliary synchronization channel. After determining the synchronous base station to be handoff target by using this, additionally, the long code synchronization and frame synchronization necessary are moved to the frequency band of the synchronous base station and then transmitted by the synchronous base station through the second auxiliary synchronization channel. The timing of a synchronous mobile communication system can be obtained without demodulation, enabling a stable and fast handoff between asynchronous and synchronous systems. That is, since the mobile station communicating in the asynchronous mobile communication system can acquire the information on the neighboring cells of the asynchronous mobile communication system in a short time, it is possible to reduce the call disconnection time between the asynchronous mobile communication system and the mobile station. .

Claims (31)

A forward pilot channel generator for generating a pilot signal; A forward sync channel generator for generating a sync signal; A forward first auxiliary synchronization channel generator for generating PN_OFFSET information of the base station; A second forward auxiliary channel generator for generating a long code state signal and frame timing information of the base station; A forward transmission control channel generator for generating a control message of a dedicated channel; A forward dedicated basic channel generator for generating a voice signal, A base station transmitter comprising a forward dedicated additional channel generator for generating packet data. The method of claim 1, wherein the first auxiliary synchronization channel generator, An encoder for encoding the first auxiliary synchronization channel data, A repeater for repeating symbols output from the encoder by a set number of times; An interleaver for interleaving the output of the iterator; A signal converter for converting a level of the first auxiliary synchronization channel signal output from the interleaver; And a multiplier for performing orthogonal modulation by multiplying an orthogonal code with a first auxiliary synchronization channel signal output from the signal converter. The method of claim 1, And the first auxiliary synchronization channel generator orthogonally modulates and outputs the PN_OFFSET information. The method of claim 1, And the first auxiliary synchronous channel generator adds a CRC to PN_OFFSET information and quadrature modulates and outputs the quadrature modulation. The method according to claim 3 or 4, And the PN_OFFSET information is a data string represented by 9 bits. The method of claim 1, And a first auxiliary synchronization channel frame generated by the first auxiliary synchronization channel generator is transmitted at least once within a PN code period. The method of claim 6, The PN terminal code period is 26.666..ms characterized in that the base station transmitter. The method of claim 6, And a transmission frequency of the first auxiliary synchronization channel frame is determined by Equation 2 below. N_chip = {(K + CRC) × R × N ₁ × W ^l } × N ₂ Here, N_chip = number of chips in one cycle of PN code (32768 for SR1 and 98304 for SR3) K = data bit (number of header bits + PN_OFFSET value + length of zero padding bit) Here, whether to use header bits and zero padding bits is optional. CRC = CRC bit used in the 1st auxiliary synchronization channel R = code rate of encoder used in the 1st auxiliary synchronization channel generator N ₁ = number of symbol repetitions W ^l = length of the Walsh code N ₂ = Number of PN_OFFSET FRAME transmissions during one cycle of PN end call A method for performing handoff when a mobile station moves from an asynchronous base station to a synchronous base station having a first auxiliary synchronization channel, When the mobile station detects the pilot signal of the synchronous base station at the maximum size, obtaining and reporting PN_OFFSET information transmitted from the synchronous base station through a forward first auxiliary synchronization channel to the asynchronous base station; When the mobile station receives information necessary for handoff to the synchronization base station corresponding to the PN_OFFSET information from the asynchronous base station, the mobile station performs a handoff operation to the synchronization base station by using the information necessary for the handoff. How to. The method of claim 9, The information required for the handoff includes traffic channel information for the mobile station to communicate with the synchronization base station, system information of the synchronization base station, and information of a second auxiliary synchronization channel. The method of claim 9, The PN_OFFSET information is a data string represented by 9 bits. The method of claim 9, And wherein the first auxiliary synchronization channel frame is transmitted at least once within a PN code period. The method of claim 12, The PN terminal code period is characterized in that 26.666..ms. The method of claim 9, When the asynchronous station receives the PN_OFFSET information, the asynchronous station transmits the information to the upper network, and then the system information of the synchronous base station corresponding to the PN_OFFSET information received from the upper network, the traffic channel information for communicating with the base station, and the long code state signal. And transmitting second auxiliary synchronization channel information for transmitting frame timing information to the mobile station as the handoff information. In the method of performing a handoff of the asynchronous base station when the mobile station moves from the asynchronous base station to the synchronous base station having auxiliary synchronous channels, Receiving pilot signal measurement results of neighboring asynchronous base stations to the mobile station; Notifying the mobile station to handoff to the asynchronous base station when it is determined that there is an asynchronous base station to handoff from the measurement result; Determining and transmitting a pilot signal detection parameter for a synchronous base station cell when determining that there is no asynchronous base station to hand off; Determining whether a target cell to be handed off is a synchronous base station upon receiving the pilot signal measurement result from the mobile station; Handoff system information of the synchronization base station, traffic channel information for communication with the synchronization base station, and information on a second auxiliary synchronization channel newly established or already set in the synchronization base station from the synchronization base station temporary upper network; And transmitting the information to the mobile station together with the necessary information. The method of claim 15, And when notifying that the target cell to be handed off is an asynchronous base station, informing the mobile station to handoff to the asynchronous base station. The method according to claim 15 or 16, The pilot signal detection parameter includes a synchronization base station pilot signal detection period (T), a synchronization base station pilot signal detection time (T ₀ ), and a synchronization base station pilot signal detection frequency (N). In the method of performing a handoff of the mobile station when the mobile station moves from the asynchronous base station to the synchronous base station having auxiliary synchronous channels Receive pilot signal measurement parameters of neighboring base stations at handoff, detect pilot signal of synchronous base station during the first search section according to the received measurement parameter, detect pilot signal of neighbor asynchronous base station during second search section, and , Repeating this the set number of times, Acquiring PN_OFFSET information through a first auxiliary synchronization channel of the synchronous base station in the presence of a synchronous base station in which a pilot signal is detected at a set level or higher and reporting it to the asynchronous base station together with a reception strength measurement result; Transmitting a reception strength measurement result to the asynchronous base station in the presence of an asynchronous base station in which a pilot signal is detected to be above a set level in the second search section; Determining whether a target cell is a synchronous base station or an asynchronous base station when receiving a handoff message from the asynchronous base station; After the target cell shifts the band to the synchronous base station, the second auxiliary synchronization channel is first demodulated, the long code generator is initialized, the frame timing is aligned, and the call channel is set to wait for reception of a good frame. And performing a handoff operation to the asynchronous base station at the time of the target cell. The method of claim 18, The first search section has a time period relatively smaller than the second search section. The method of claim 19, The mobile station detects the pilot signal in the second search section and simultaneously communicates with the asynchronous base station. The method of claim 19, And the mobile station temporarily stores a signal of a synchronization base station received during the first search period, and detects the strength of a pilot signal with the stored signal in the second search period. In the method of performing a handoff of the synchronization base station when the mobile station moves from the asynchronous base station to the synchronization base station having the auxiliary synchronization channel Transmitting a pilot signal and transmitting its own PN_OFFSET information through the first auxiliary synchronization channel; When receiving information that the mobile station is handed off to its cell from an upper network, an extra Walsh code is allocated to the mobile station to set a second auxiliary synchronization channel and broadcasted to the asynchronous base station. Transmitting the traffic data through the forward basic channel assigned to the And completing a second auxiliary synchronization channel set when there is no other terminal handing off into a cell when receiving a handoff complete message from the mobile station. The method of claim 1, wherein the second auxiliary synchronization channel generator, An encoder for encoding second auxiliary synchronization channel data, A repeater for repeating symbols output from the encoder by a set number of times; An interleaver for interleaving the output of the iterator; A signal converter for converting a level of the first auxiliary synchronization channel signal output from the interleaver; And a multiplier configured to multiply orthogonally modulate a second auxiliary synchronization channel signal output from the signal converter and an orthogonal code. The method of claim 1, And the second auxiliary synchronization channel generator orthogonally modulates the long code state information and the frame timing information. The method of claim 1, And the second auxiliary synchronous channel generator adds a CRC to the long code state information and the frame timing information to perform orthogonal modulation for output. The method of claim 25, The long code state information is represented by 41 bits and is a data string representing a long code generator state after a predetermined time from a reception time, and the frame information timing is 20 msec. And a data string represented by two bits indicating the moment when the frame coincides with the start point of the 26.666 .. msec end-call period. The method of claim 1, And a second auxiliary synchronization channel frame generated by the second auxiliary synchronization channel generator is transmitted at least once within a PN code period. The method of claim 27, And a transmission frequency of the second auxiliary synchronization channel frame is determined by Equation 3 below. N_chip = {(K + CRC) × R × N ₁ × W ^l } × N ₂ Here, N_chip = number of chips in one cycle of PN code (32768 for SR1 and 98304 for SR3) K = data bit (long coded value length + frame timing information value length + zero padding bit length) CRC = CRC bit used in the 1st auxiliary synchronization channel R = code rate of encoder used in the 1st auxiliary synchronization channel generator N ₁ = number of symbol repetitions W ^l = length of the Walsh code N ₂ = Number of PN_OFFSET FRAME transmissions during one cycle of PN end call The method of claim 15, And the information on the second auxiliary synchronization channel is a Walsh code and a frequency band of the second auxiliary synchronization channel set in the synchronous base station. In a hard handoff method from an asynchronous cell to a synchronous cell, The synchronization base station of the synchronization cell includes a first auxiliary synchronization channel for transmitting PN_OFFET information and frame synchronization information and a second auxiliary synchronization channel for transmitting long code state information, and the PN_OFFSET information through the first auxiliary synchronization channel. And broadcasting information on frame synchronization; Acquiring PN_OFFSET information through the first auxiliary synchronization channel and notifying the asynchronous base station of the asynchronous cell when the mobile station acquires a signal of the synchronous base station through a discovery process, and obtaining the frame synchronization; When the handoff instruction is received from the asynchronous base station, the communication with the asynchronous base station is terminated, the second auxiliary synchronization channel is received at the time point of the acquired frame synchronization to obtain a long code state, and communication with the asynchronous base station is performed. Method comprising the process of performing. The method of claim 30, The handoff instruction includes system information of the synchronous base station, traffic channel information for communication with the synchronous base station, and information on the second auxiliary synchronous channel.