JPH1051852A - Method for using spread code in cdma mobile communication system and base station equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for using a spread code in a code division multiple access(CDMA) mobile communication system and the base station equipment in which the capacity is increased by making possible incoming radio channel same code soft hand-over even when a decreased long code length is shared for a plurality of cells/sectors. SOLUTION: Each base station measures sequentially a reception level as to all or part of combinations not in use among combinations of long codes and short codes as to an incoming radio channel (steps S11, S12) and selects a combination between long codes and short codes providing a lowest reception level in the case of setting up a radio channel with a specific mobile station so as to set up the radio channel (steps S13, S14), then the radio channel is set up through the combination of long codes and short codes most apart from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread code using method and a base station apparatus in a code division multiple access (hereinafter abbreviated as CDMA) type mobile communication system using a spread spectrum code.

[0002]

2. Description of the Related Art In IS-95, which is one of the CDMA digital mobile communication systems in the United States, a spreading code different for each mobile station, specifically, a long code having a long code length, is used as a spreading code for an uplink. You are using code. By using a different long code for each mobile station in this way, even if the mobile station repeats movement between cells / sectors after calling / receiving connection, it is possible to always use the same spreading code for the uplink radio line. Therefore, at the time of handover activation, it is possible to always execute soft handover of the same code on the uplink radio line which can increase the capacity.

In the United States mobile communication system IS-95, high-precision synchronization is established between base stations, and the entire system operates at the same long code phase. Therefore, the base station can establish synchronization with the uplink radio channel transmitted by the mobile station at a known timing. However, achieving high-precision synchronization between base stations increases the load on the system and is disadvantageous in terms of cost.

In this regard, the asynchronous system between base stations is more effective than the synchronous system between base stations. On the other hand, since a different long code phase is used for each base station, an extremely long time is required to establish the synchronization of the long code.

On the other hand, methods for establishing long code synchronization in a short time are disclosed in Japanese Patent Application Nos. 6-95086 and 6-110833. In these methods, since control such as constantly reporting long code phase information from the base station is required, a method of establishing long code synchronization in a short time without using these methods is desired.

As one proposal, it is conceivable to shorten the code length of a long code. However, when the long code length is shortened, the number of usable long codes decreases, so that a different long code cannot be assigned to each mobile station. Therefore, a limited number of long codes are shared by a plurality of cells / sectors. In such a usage method of the long code, after the mobile station repeats the movement between the cells / sectors after the call connection, the same long code and the short code are already used in the destination cell / sector. Can occur. In this case, it is not possible to execute soft handover with the same code for the uplink wireless channel, and thus it is impossible to increase the capacity.

[0007]

As described above, in order to establish the synchronization of a long code in a short time, the code length of the long code is reduced so that it is shared by a plurality of cells / sectors. However, there is a case where it is not possible to execute soft handover with the same code for the uplink radio line, and there is a problem that capacity cannot be increased.

[0008] The present invention has been made in view of the above,
It is an object of the present invention to provide a method of using a spreading code in a CDMA mobile communication system capable of increasing the capacity by enabling soft handover of the same code on the uplink radio line even if the long code length is shortened and shared by a plurality of cells / sectors. An object of the present invention is to provide a base station device.

[0009]

In order to achieve the above object, according to the present invention, in each cell / sector, a radio line used for communication between a base station and a mobile station has a code length. A method of using a spreading code in a CDMA mobile communication system in which a long code that is a long spreading code and a short code that is a spreading code shorter in code length than the long code are used. For the uplink radio line, the reception level is sequentially measured for all or some of the unused combinations among the combinations of the long code and the short code, and a combination having a low reception level is selected, and the base station transmits a specific combination. When setting a wireless line with a mobile station, select the combination of the long code and short code with the lowest reception level at the time of setting. And summarized in that to set the radio channel Te.

According to the first aspect of the present invention, each base station sequentially measures the reception level of all or some of the unused combinations of the long code and short code combinations for the uplink radio line. When setting a wireless line with a specific mobile station, the combination of the long code and short code with the lowest reception level is selected and the wireless line is set. Use to set up a wireless line.

Further, according to the present invention, each cell /
A method of using a spreading code in a CDMA mobile communication system in which a radio channel used for communication between a base station and a mobile station in a sector is set using a long code having a long code length. The mobile station sequentially measures the reception level of all or a part of the long code with respect to the uplink radio line from the mobile station, selects one having a low reception level, and sets the base station to a radio line with a specific mobile station. At the time of setting, the gist is that the long code having the lowest reception level at the time of the setting is selected to set a wireless channel.

According to the second aspect of the present invention, each base station sequentially measures the reception level of all or a part of the long code for the uplink radio line, and sets up the radio line with a specific mobile station. In this case, since a long code having the lowest reception level is selected to set a radio line, a radio line can be set with the longest long code.

Further, the present invention according to claim 3 provides the invention according to claim 1.
Alternatively, in the invention according to the second aspect, a gist of the invention is to use a reception SIR, which is a ratio between a desired wave reception level and an interference wave reception level, instead of the reception level.

According to a fourth aspect of the present invention, a service area is divided into a plurality of unit areas, ie, cells or sectors.
When a base station is provided in each of the plurality of cells, and a long code that is a spread code having a long code length is assigned to each of the plurality of cells or sectors, N types of long codes are geographically collected. Is assigned to each of the N cells or sectors arranged in the base station, and is used as a basic allocation pattern of a long code. The basic allocation pattern is geographically repeated, and a long code is allocated. As the long code for the uplink radio channel from the station, the long code repeatedly used is used, and the base station sets the uplink radio channel with the mobile station that has been transitioned by soft handover so that the mobile station is already in the handover source. Use the same long code as the uplink radio line set between the base station and the And summarized in that to achieve the same code soft handover.

According to the present invention, a basic allocation pattern of long codes in which N types of long codes are respectively allocated to N cells or sectors arranged in a geographically integrated range is geographically repeated. In connection with outgoing / incoming calls, the base station uses the repeatedly assigned long code as the long code for the uplink radio channel from the mobile station, and communicates with the mobile station that has transitioned through soft handover. In the setting of the uplink radio line, the mobile station uses the same long code of the uplink radio line that has already been set with the handover source base station to realize soft handover with the same code of the uplink radio line. be able to.

According to a fifth aspect of the present invention, in the invention of the fourth aspect, a group of one or a plurality of upstream long codes and a group of a single or a plurality of downstream long codes have a one-to-one correspondence. The gist of the present invention is to assign both the up and down long codes in the long code assignment.

According to a sixth aspect of the present invention, a radio line used for communication between a base station and a mobile station in each cell / sector is provided with a long code, which is a spreading code having a long code length, and a longer code than the long code. A base station device in a CDMA mobile communication system set in combination with a short code that is a spread code having a short code length, wherein the base station device combines the long code and the short code for an uplink radio channel from a mobile station. Measuring means for sequentially measuring the reception level for all or some of the unused combinations, storage means for storing the reception level measured by the measurement means, and setting of a radio line with a specific mobile station. The combination of the long code and the short code having the lowest reception level at the time of the setting is stored in the reception level stored in the storage means. Selected based on, and summarized in that a control means for controlling to set a radio channel with a combination of the selected long code and short code.

According to the sixth aspect of the present invention, each base station sequentially measures the reception level of all or some of the unused combinations of the long code and short code combinations for the uplink radio line. When setting a wireless line with a specific mobile station, the combination of the long code and short code with the lowest reception level is selected and the wireless line is set. Use to set up a wireless line.

According to a seventh aspect of the present invention, in each cell / sector, a radio channel used for communication between a base station and a mobile station is set using a long code which is a spreading code having a long code length. A base station device in a mobile communication system, wherein the base station device sequentially measures all or a part of the reception level of the long code for an uplink radio channel from a mobile station, and the measurement unit measures the reception level. Storage means for storing a reception level, and when setting a wireless channel with a specific mobile station, selecting the long code having the lowest reception level at the time of setting based on the reception level stored in the storage means Further, the gist of the present invention is to have control means for controlling to set a wireless channel using the selected long code.

According to the present invention, each base station sequentially measures the reception level of all or a part of the long code for the uplink radio line, and sets up the radio line with a specific mobile station. In this case, since a long code having the lowest reception level is selected to set a radio line, a radio line can be set with the longest long code.

According to an eighth aspect of the present invention, in the sixth or seventh aspect of the present invention, instead of the reception level,
Reception S, which is the ratio between the desired wave reception level and the interference wave reception level
The point is to use IR.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a base station device in a CDMA mobile communication system that implements a spreading code using method according to one embodiment of the present invention.

The base station apparatus shown in FIG. 1 has an antenna 1 for receiving a radio signal from a mobile station and transmitting a radio signal to the mobile station. A signal from the mobile station received by the antenna 1 is transmitted and received. The signal is supplied to the demodulation circuit 7 and the measurement circuit 19 via the distribution circuit 3 and the reception circuit 5, and the demodulation circuit 7 performs despreading using a spreading code and normal demodulation. The demodulated signal is supplied to a decoding circuit 9, where the transmission signal and the control signal are decoded.
, And the transmission signal is transmitted to a higher-level switching center. The measurement circuit 19 measures a reception level or a reception SIR which is a ratio of a desired signal reception level and an interference wave reception level with a combination of a long code and a short code designated by the control circuit 11 or only with the long code as described later. The measurement result is supplied to the control circuit 11. The control circuit 11
The measurement result is supplied to the memory 21, and the memory 21 stores the measurement result for each combination of a long code and a short code or for each long code.

The transmission signal from the exchange to the base station is:
The modulated signal is supplied to the encoding circuit 13 and encoded by the encoding circuit 13 together with the control signal from the control circuit 11.
Are subjected to primary modulation and spread modulation by a spread code, and then transmitted from the antenna 1 to the mobile station via the transmission circuit 17 and the transmission / reception distribution circuit 3.

The control circuit 11 controls the entire base station, notifies the measurement circuit 19 of only the long code and the short code or the long code whose reception level is to be measured, and measures the measured value of the reception level or the reception SIR. And has the function of selecting a combination with a low reception level or a low reception SIR from the memory 21.

FIG. 2 is a flowchart showing a processing operation in the spreading code using method of the present embodiment, which is performed by the base station apparatus shown in FIG.

The method of using a spreading code according to the present embodiment establishes long code synchronization in a short time without controlling long code phase information for each base station in realizing an asynchronous mobile communication system between base stations. In order to achieve this, the code length of the long code is shortened, and the code length is shortened so that a limited number of long codes can be stored in a plurality of cells / cells.
It is shared by sectors.

When the limited long code is shared by a plurality of cells / sectors, the same long code and the short code used in combination with the long code may already be used. However, as described in the related art, there is a problem that the soft handover cannot be performed for the same code on the uplink radio line, and thus the capacity cannot be increased. In this embodiment, such a problem is solved. For this purpose, the combination of a long code and a short code in each cell / sector is selected and the unused one with the lowest reception level is measured and selected, and a radio line is established using the selected combination of the long code and the short code. Is what you want to set.

This will be described specifically with reference to the flowchart of FIG. In FIG. 2, the control circuit 11 of each base station appropriately selects an unused combination of a long code and a short code in each cell / sector for an uplink radio line (step S11). Control circuit 1
1 causes the measuring circuit 19 to sequentially measure the reception level for all or a part of the selected unused long code and short code combination (step S12), and compares the measured reception level with the combination of the long code and the short code. Each combination is stored in the memory 21 and a combination having a low reception level is selected (step S13).

At the time of setting up a radio channel with a specific mobile station, the control circuit 11 of the base station selects a combination of a long code and a short code having the lowest reception level at the time of the setting from the memory 21. Set up a wireless line using long code and short code (step S
14).

By selecting the combination of the long code and the short code having the lowest reception level from the combination of the long code and the short code, the same combination of the long code and the short code is used at the farthest place. Therefore, even if the mobile station repeats the movement between cells / sectors after the call connection, the combination of the same long code and short code collides, and execution of soft handover with the same code for the uplink radio line is not possible. The possibility of becoming possible can be extremely reduced.

In the above embodiment, the case where the reception level is measured has been described. However, instead of the reception level, a reception SIR which is a ratio between a desired wave reception level and an interference wave reception level may be used. Further, instead of the combination of the long code and the short code, only the long code may be used.

FIG. 3 shows a CD according to another embodiment of the present invention.
FIG. 4 is an explanatory diagram showing assignment of a long code to each cell / sector that implements a method of using a spreading code in an MA mobile communication system.

In this embodiment, similarly to the embodiment described with reference to FIG. 1, the code length of the long code is shortened, and the long code having the short code length is shared by a plurality of cells / sectors. In the present embodiment, as shown in FIG. 3, a limited number of long codes C1, C2, C3.
Are assigned to a plurality of cells or sectors installed in a geographically coherent range, respectively, and these are used as basic allocation patterns of long codes, and the basic allocation patterns are geographically repeated to allocate long codes. In FIG. 2, 19 long codes C1 to C19 are allocated to 19 cells, respectively, and the allocation pattern of these 19 long codes is used as a basic allocation pattern. The same number of more cells or sectors may constitute the basic assignment pattern. As a result, cells using the same long code C1, C2, C3.
Since the sectors can be arranged at the same repetition distance for all the long codes, a combination of some long codes and short codes can be used at a relatively short distance to reduce the probability of collision. it can.

Then, the base station, when making outgoing and incoming connections,
As the long code for the uplink radio channel, a long code repeatedly assigned to a cell or a sector is used.

In addition, the base station sets up an uplink radio channel with the mobile station that has transitioned by soft handover,
The mobile station uses the same long code as that of the uplink radio channel already set up with the handover source base station, thereby realizing soft handover of the same code for the uplink radio channel.

By assigning a long code to each cell / sector as described above, cells / sectors that use the same long code in outgoing / incoming connections can be separated by the same repetition distance for all long codes. Therefore, it is possible to minimize the possibility that a combination of the same long code and short code will collide with the movement of the mobile station for some long codes, and that the execution of soft handover for the same code on the uplink radio line becomes impossible. it can.

In the above embodiment, the group of one or more uplink long codes and the group of one or more downlink long codes have a one-to-one correspondence, so that one long code arrangement can be used for uplink and downlink. The arrangement of both long codes can be performed. That is, since the long code arrangement required for the uplink and the downlink can be performed up to the other arrangement only by examining one arrangement, the system design can be simplified.

[0040]

As described above, according to the present invention,
Each base station successively measures the reception level / reception SIR or the reception level / reception SIR of all or part of the long code for all or some of the unused combinations of the long code and short code combinations for the uplink radio line. In addition, when setting a wireless line with a specific mobile station, a combination of a long code and a short code having the lowest reception level / reception SIR or a long code is selected and the wireless line is set. The wireless line can be set up with a combination of a long code and a short code or a long code. The possibility of becoming impossible can be minimized.

Also, according to the present invention, a long code is repeatedly assigned to each of a plurality of cells / sectors, and the base station uses the long code as the long code for the uplink radio line from the mobile station when making a call connection. In setting up an uplink radio channel with a mobile station that has transitioned by soft handover using a repeatedly assigned long code, the long radio channel already set up by the mobile station with the handover source base station is used. Using the same code as the code to realize soft handover for the same code on the uplink radio line,
The combination of the same long code and short code collides with some of the long codes as the mobile station moves, thereby minimizing the possibility that execution of soft handover for the same code on the uplink radio line becomes impossible.

Further, according to the present invention, a group of one or more uplink long codes and a group of one or more downlink long codes have a one-to-one correspondence, and both uplink and downlink are assigned by one long code assignment. , The system design can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a base station device in a CDMA mobile communication system that implements a spreading code using method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing operation in a spreading code using method of the present embodiment performed by the base station apparatus shown in FIG. 1;

FIG. 3 is an explanatory diagram showing assignment of a long code to each cell / sector for implementing a method of using a spreading code in a CDMA mobile communication system according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 transmission / reception distribution circuit 5 reception circuit 7 demodulation circuit 9 decoding circuit 11 control circuit 13 encoding circuit 15 modulation circuit 17 transmission circuit 19 measurement circuit 21 memory

Claims (8)

[Claims] 1. A radio line used for communication between a base station and a mobile station in each cell / sector is composed of a long code having a long code length and a spread code having a code length shorter than the long code. A method of using a spreading code in a CDMA mobile communication system to be set in combination with a short code, wherein each base station uses an unused combination of the combination of the long code and the short code for an uplink radio channel from a mobile station. The reception level is sequentially measured for all or a part, and a combination having a low reception level is selected, and the base station sets up a radio line with a specific mobile station.
A method for using a spreading code in a CDMA mobile communication system, wherein a combination of the long code and the short code having the lowest reception level at the time of the setting is selected to set a radio channel. 2. Use of a spreading code in a CDMA mobile communication system for setting a radio channel used for communication between a base station and a mobile station in each cell / sector using a long code which is a spreading code having a long code length. A method, wherein each base station sequentially measures the reception level of all or a part of the long code for an uplink radio channel from a mobile station,
This low reception level is selected, and the base station sets up a radio line with a specific mobile station,
C. wherein the long code having the lowest reception level at the time of setting is selected to set a radio line.
A method of using a spreading code in a DMA mobile communication system. 3. The CDMA according to claim 1, wherein a reception SIR, which is a ratio between a desired wave reception level and an interference wave reception level, is used instead of the reception level.
A method of using a spreading code in a mobile communication system. 4. A service area is divided into a plurality of cells or sectors as unit areas, a base station is provided in each of the plurality of cells, and a spread with a long code length is applied to each of the plurality of cells or sectors. When allocating a long code, which is a code, N types of long codes are allocated to N cells or sectors arranged in a geographically coherent range, respectively, and this is used as a basic allocation pattern of the long code. The base station uses the repeatedly assigned long code as a long code for the uplink radio channel from the mobile station when making and receiving connection, and the base station performs soft handover. In setting up the uplink radio channel with the mobile station that has transitioned, the mobile station is already in contact with the handover source base station. Use the same as the long code of the uplink radio lines that are set with the diffusion code used method in CDMA mobile communication system, characterized in that to realize the uplink radio channel the same coding soft handover. 5. A one or more uplink long code group and a one or more downlink long code group have a one-to-one correspondence, and one long code assignment allocates both uplink and downlink long codes. 5. The method according to claim 4, wherein the spreading code is used. 6. A radio line used for communication between a base station and a mobile station in each cell / sector is composed of a long code having a long code length and a spread code having a code length shorter than the long code. A base station apparatus in a CDMA mobile communication system set in combination with a short code, wherein all or some of the unused combinations of the combination of the long code and the short code are used for an uplink radio channel from a mobile station. Measuring means for sequentially measuring the reception level; storage means for storing the reception level measured by the measurement means; and setting of a radio line with a specific mobile station, the longest reception level at the time of the setting. A combination of a code and a short code is selected based on the reception level stored in the storage means, and the selected long code is selected. Control means for controlling a wireless line to be set by a combination of a code and a short code.
A base station device in a mobile communication system. 7. A base station apparatus in a CDMA mobile communication system in which a radio channel used for communication between a base station and a mobile station in each cell / sector is set using a long code that is a long code length spreading code. A measuring means for sequentially measuring the reception level of all or a part of the long code for an uplink radio channel from a mobile station; a storage means for storing the reception level measured by the measurement means; and a specific mobile station. When setting the wireless line with, the long code having the lowest reception level at the time of the setting is selected based on the reception level stored in the storage means,
Control means for controlling to set up a radio line using the selected long code.
A base station device in a DMA mobile communication system. 8. The CDMA according to claim 6, wherein a reception SIR, which is a ratio between a desired wave reception level and an interference wave reception level, is used instead of the reception level.
A base station device in a mobile communication system.