JP2002369244A - Small-capacity base station control system for cdma mobile communication system, and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-capacity base station control system, capable of economically and simply enlarging a service area by efficiently utilizing a special purpose line resource and suppressing base station adding cost for eliminating a dead zone. SOLUTION: A small capacity base station (S-BTS) adding means for eliminating the dead zone comprises an equipment of one sector part. A selection combining means of a radio communication signal from the small-capacity base station (S-BTS) is diverted from a soft hand-over function between sector cells of a normal base station (BTS) and controller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio network control system and method in a code division multiple access (CDMA) mobile communication system, and more particularly to a control of a small capacity base station for eliminating a blind zone. The method and the method.

[0002]

2. Description of the Related Art In recent years, the number of subscribers in a digital mobile communication system has increased remarkably, and with this, the service area in which the subscribers can use a portable telephone has been expanding. At present, mobile communication carriers are gradually expanding their service areas, but subscribers still want to use them even in suburbs or mountainous areas that are not service areas. In addition, obstacles such as department stores, underground shopping centers, buildings, etc.
Even within the service area, there are many blind zones where radio waves from base stations do not reach and mobile phones cannot be used.

In order to cover such a dead zone in detail, a base station (Base Transceiver Station:
The conventional base station expansion method adjusts the size of the base station (the number of usable channels, etc.) according to the traffic volume and installs the base station.

However, the service area for eliminating dead zones caused by obstacles such as department stores, underground shopping malls, buildings and the like has a small coverage, so that the traffic volume is small, and a conventional base station is installed in such a low traffic zone. Doing so would be too large and costly. Also,
To increase the number of base stations, a radio network controller (Radio Network Controller: RN)
C) also needs to be increased, which is not only economical, but also complicates maintenance and operation.

[0005]

In addition to the cost problem associated with the installation of various devices described above, there are also problems specific to CDMA mobile communication systems. FIG. 5 shows a conventional CDM.
1 is a schematic block diagram illustrating a mobile communication system A. FIG.
As shown in FIG. 5, the base station (BTS) 51 and the base station (B
A TS 52 and a base station (BTS) 53 are connected to a radio network controller (RNC) 55 by dedicated lines 57, 58, and 59, respectively.
55 is a Mobile Switching Center (M)
SC) 56 to form a CDMA mobile communication system.

[0006] The mobile terminal 50 includes a base station 51 and a base station 53.
Are located in the service area overlap zone, and two radio paths are provided and connected between the base station 51 and the base station 53.

The radio network controller 55 has a selection / combining means 54 for performing soft handover processing between a plurality of base stations. In the example of FIG. 4, soft handover processing is performed between the base station 51 and the base station 53. . This soft handover process enables simultaneous communication with multiple base stations for mobile terminals located on the service area boundary, thereby realizing a call without interruption between multiple base stations and using less transmission power. This is a technique for obtaining good communication quality.

The base stations 51 and 52 are small capacity base stations, and the base station 53 is a normal base station.

When the position of the mobile terminal 50 is not changed (the mobile terminal is stopped) during the soft handover process between a plurality of base stations including the small-capacity base station as described above, , Small capacity base station 51 and base station 53
The soft handover state is continued for a long time, and a problem occurs that the dedicated line resource is occupied for a long time.

[0010] The present invention has been made in view of the above,
The objective is to reduce the cost of adding base stations to eliminate dead zones and to efficiently utilize dedicated line resources to create a small-capacity base station control method that can expand the service area economically and easily. To provide.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a mobile terminal, a parent base station comprising a service area divided into a plurality of sector cells,
A mobile communication system of a code division multiple access system configured with the parent base station and a small capacity base station connected thereto, wherein the parent base station communicates with the mobile terminal located in a sector cell of the base station. Means for performing wireless communication, wherein the small-capacity base station performs wireless communication with the mobile terminal located within the service area of the base station and simultaneously transfers the wireless communication information to the parent base station. When the mobile terminal is located in an overlap zone between a sector cell area of the parent base station and a service area of the small capacity base station, the parent base station includes radio communication information of the parent base station. Means for selectively combining the transferred wireless communication information of the small capacity base station by softer handover processing.

Further, the means for performing wireless communication of the small-capacity base station may be constituted by equipment for one sector of the parent base station.

The means for connecting the parent base station and the small-capacity base station comprises a line termination device installed in the parent base station, a dedicated line, and a line termination device installed in the small-capacity base station. You may.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a CDMA mobile communication system constituting the present invention. As shown in FIG. 1, a base station (S-BTS) 2 and a base station (BTS) 4 are connected by a dedicated line 8, and a base station (S-BTS) 3 and a base station (BTS) 4 are connected by a dedicated line. The base station (BTS) 4 is connected to a radio network controller (RNC) 6 by a dedicated line 10.
The radio network controller (RNC) 6 is connected to the mobile radio switch (MSC) 7 to form a CDMA mobile communication system.

The base station (S-BTS) 2 and the base station (S-BTS) 3 are small-capacity base stations and the base station (BTS)
4 is the parent base station. The service area of the parent base station 4 is divided into a plurality of sector cells, and the small-capacity base station 2 and the small-capacity base station 3 are configured to correspond to one sector cell in the parent base station 4, respectively.

The mobile terminal 1 is located in the service area overlap zone of the small capacity base station 2 and the parent base station 4, and provides two radio paths between the small capacity base station 2 and the parent base station 4. Connected.

The parent base station 4 has a selecting / combining means 5 for performing a softer handover process between a plurality of sector cells.
In the example of FIG. 1, softer handover processing is performed between the small capacity base station 2 and the parent base station 4. The softer handover process enables simultaneous communication between a plurality of sector cells to a mobile terminal located at a sector cell area boundary, thereby realizing a non-stop communication between a plurality of sector cells, and achieving good transmission with less transmission power. This is a technique for obtaining communication quality.

FIG. 2 is a conceptual diagram of the service area of the small capacity base station (S-BTS) 2, the small capacity base station (S-BTS) 3, and the parent base station (BTS) 4, which constitute the present invention. As shown in FIG. 2, the service area of the parent base station 4 is divided into three sector cells, which are respectively a sector a (13), a sector b (14), and a sector c (15).

There is an obstacle 16 in the sector c (15) of the parent base station 4, and there is a dent (dead zone) in the service area behind the obstacle 16 as shown in the figure. Then, a small-capacity base station 3 is installed to supplement the dead zone, and forms a service area 12.

There is a dead zone in the area adjacent to the sector b (14) of the parent base station 4, and the small-capacity base station 2 is installed to supplement the dead zone, and constitutes the service area 11. The mobile terminal 1 is located in the overlap zone between the service area 11 of the small capacity base station 2 and the sector b (14) of the parent base station 4.

Incidentally, a small capacity base station (S-BTS) 2, a small capacity base station (S-BTS) 3, a parent base station (BTS) 4, a radio network controller (RNC) 6, and a mobile radio switch (MSC) The connection state of 7 is the same as that described in FIG.

As can be seen from the description of FIG. 1 and FIG.
Necessary functions of the small-capacity base station 2 and the small-capacity base station 3 for eliminating the dead zone can be configured only by a radio communication function corresponding to one sector of the parent base station 4 and a connection function with the parent base station 4. The functions required for the small-capacity base station addition in the parent base station 4 include a function of selectively combining radio communication signals corresponding to one sector held by the small-capacity base station 2 and the small-capacity base station 3, and a function of the small-capacity base station. It can be constituted only by the connection function with the station 2 and the small capacity base station 3. The function of selectively combining the radio communication signals can be realized by diverting and controlling the softer handover function between sector cells of a normal base station.

A dedicated line 8 used to connect the small-capacity base station 2 to the parent base station 4 and a dedicated line 9 used to connect the small-capacity base station 3 to the parent base station 4 are, as shown in FIG. The cell radius of the base station 4 plus the length of α may be sufficient, and it is possible to configure with a small line capacity corresponding to the traffic of the small capacity base station 2 and the small capacity base station 3.

FIG. 3 is an equipment block diagram of the small capacity base station (S-BTS) and the parent base station (BTS) described in FIGS. As shown in FIG. 3, the small-capacity base station (S-BTS) 2 includes an antenna 20 and a duplexer (D-BTS).
UP) 21, a transmission / reception amplifier (AMP) 22 composed of a transmission amplifier and a reception amplifier, and a radio transmission / reception device (TRX) 23 for converting a radio frequency signal into a baseband signal and converting the baseband signal into a radio frequency signal. And a line termination unit (DSU) 24 for performing protocol conversion between a dedicated line and
And is connected to the parent base station (BTS) 4 by a dedicated line 8.

Similarly, the small capacity base station (S-BTS) 3
An antenna 25, a duplexer (DUP) 26, and a transmission / reception amplifier (AM) including a transmission amplifier and a reception amplifier
P) 27, a radio transceiver (TRX) 28 for converting a radio frequency signal to a baseband signal and a baseband signal to a radio frequency signal, and a line termination unit (DSU) 29 for performing protocol conversion with a dedicated line. And is connected to the parent base station (BTS) 4 by a dedicated line 9.

As described above, the small-capacity base station 2 and the small-capacity base station 3 are each composed of the equipment for one sector of the parent base station 4, and particularly the radio transceiver (TR) of the small-capacity base station.
Since X) can use the radio transceiver (TRX) of the parent base station as it is, the cost of adding a base station for eliminating the dead zone can be reduced.

Next, the parent base station (BTS) 4 is a base station having a three-sector configuration, and includes an antenna 30 of sector a, an antenna A of sector b, an antenna 32 of sector c, and a duplexer for three sectors. DUP) 33, a transmission amplifier (TX AMP) 34 for three sectors, a reception amplifier (RX AMP) 35 for three sectors, and a switch (RF SW &) for switching and distributing radio frequency signals for each radio channel.
DIST) 36 and a plurality of wireless transmission / reception device groups (TRX1) 37 to (TRXn) 3 corresponding to wireless channels for three sectors.
8 and a signal processing unit 39 installed corresponding to TRX1
And a common control unit 4 to which a plurality of signal processing units are connected to perform various control processes with a radio network controller (RNC)
2 and a line terminating device (DS) for performing protocol conversion between a dedicated line 8 and a small capacity base station (S-BTS) 2.
U) 40 and a line termination unit (DSU) 41 for performing protocol conversion with the dedicated line 9 for connection to the small capacity base station (S-BTS) 3.

In FIG. 3, the first wireless transmission / reception device (T
RX1) 37 and the last radio transceiver (TRXn) 38
Are shown, and the illustration of the wireless transmitting / receiving device mounted between them is omitted. FIG. 3 also shows only the signal processing unit 39 corresponding to TRX1, and omits the illustration of signal processing units corresponding to other TRXs.

The signal processing unit 39 includes a radio transmitting / receiving device (T
RX1) 37 baseband signals for three sectors, a dedicated line 8 and a baseband signal of the small-capacity base station 2 via a line termination unit (DSU) 40, a dedicated line 9 and a line termination unit (D
The baseband signal of the small-capacity base station 3 via the SU) 41 is connected, and the signal processing unit 39 performs encoding / decoding processing of these baseband signals and also performs selective synthesis processing related to these softer handover operations. In the example of FIGS. 1 and 2, the sector b of the small capacity base station 2 and the parent base station 4
(14) is in the softer handover state, and the respective baseband signals are added to the signal processing unit 39 to perform the softer handover processing.

That is, the softer handover processing means in the signal processing unit 39 represents the selection / synthesis means 5 shown in FIG. 1, and this selection / synthesis means is provided between the sector cells of the ordinary base station. It can be realized by diverting and controlling the softer handover function.

FIG. 4 is an operation flowchart of the present invention. As a precondition of this operation flowchart, first, the mobile terminal 1 is in the sector cell b (14) of the parent base station 4 and moves from this position to the overlap zone of the sector cell b (14) and the service area of the small capacity base station 2. The following describes the operation.

As shown in FIG. 4, the mobile terminal 1 located in the sector cell b (14) of the parent base station 4
Wireless communication with the sector cell b (14) (step 1).
00).

While performing the above communication, the mobile terminal 1 moves to the overlap zone between the sector cell b (14) of the parent base station 4 and the service area of the small capacity base station 2. As a result, wireless communication between the mobile terminal 1 and the small-capacity base station 2 is newly added (Step 101), and the small-capacity base station 2 and the parent base station 4 are connected to each other. Communication information with the station 2 is transferred to the parent base station 4 (step 102).

The parent base station 4 transmits the first sector cell b (1
The wireless communication information with the mobile terminal 1 in 4) and the wireless communication information between the small capacity base station 2 and the mobile terminal 1 transferred in step 102 are selectively combined by softer handover processing (step 103).

Although this embodiment has been described with the configuration of two small-capacity base stations and one parent base station, and the parent base station has been described as being divided into three sectors, in the present invention the small-capacity base station is divided into three sectors. The number of base stations, the number of parent base stations, the number of sector divisions of the parent base station, and the like are not limited to these numerical values, and assume any values based on system design.

[0036]

As described above, according to the present invention,
The small-capacity base station expansion means for eliminating the dead zone can be constituted by equipment for one sector of the parent base station, and the selection and combination means for the connection signal from the small-capacity base station can be used between the sector cells of the normal base station. Can be realized by diverting and controlling the softer handover function of the above, so that it is possible to provide a small-capacity base station control method capable of economically and easily expanding the service area by suppressing the base station expansion cost. Is obtained.

Also, the dedicated line used to connect the small-capacity base station and the parent base station for eliminating the dead zone can be configured with a small line capacity corresponding to the traffic of the small-capacity base station. An effect is obtained that a small-capacity base station control system capable of efficiently and efficiently expanding resources and expanding a service area economically can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a CDMA mobile communication system constituting the present invention.

FIG. 2 shows a small capacity base station (S-BTS) constituting the present invention.
2, small capacity base station (S-BTS) 3, parent base station (BT)
It is a service area conceptual diagram of S) 4.

FIG. 3 shows a small-capacity base station (S
FIG. 2 is a device block diagram of a BTS and a parent base station (BTS).

FIG. 4 is an operation flowchart of the present invention.

FIG. 5 is a schematic block diagram showing a conventional CDMA mobile communication system.

[Explanation of symbols]

Reference Signs List 1 mobile terminal 2, 3 small-capacity base station (S-BTS) 4 parent base station (BTS) 5 selective combining means 6 radio network controller (RNC) 7 mobile radio switch (MSC) 8, 9, 10 dedicated line 11 small Service area of capacity base station (S-BTS) 2 12 Service area of small capacity base station (S-BTS) 3 13 Service area of sector a 14 Service area of sector b 15 Service area of sector c 20, 25 Antenna 21, 26, 34 Transmit / receive duplexer (DUP) 22, 27 AMP 23, 28 TRX 24, 29, 40, 41 Line terminator 30 Antenna of sector a 31 Antenna of sector b 32 Antenna of sector c 34 TX AMP 35 RX AMP 36 Switching Devices 37, 38 wireless transmission / reception device 39 signal processing unit 42 common control unit

Claims (6)

[Claims] 1. A code division multiple access system comprising a mobile terminal, a parent base station composed of a service area divided into a plurality of sector cells, and a small capacity base station connected to the parent base station. In a mobile communication system, the parent base station has means for performing wireless communication with the mobile terminal located in a sector cell of the base station, and the small-capacity base station is located in a service area of the base station. Means for performing wireless communication with the mobile terminal located at the same time and transferring the wireless communication information to the parent base station, wherein the mobile terminal is located in the sector cell area of the parent base station and the small capacity base station. When located in the overlap zone of the service area, the parent base station performs softer handover processing on the wireless communication information of the parent base station and the transferred wireless communication information of the small capacity base station. 2. A small-capacity base station control system characterized by comprising means for selecting and combining in (1). 2. The small-capacity base station control system according to claim 1, wherein the means for performing wireless communication with the small-capacity base station is constituted by devices for one sector of the parent base station. 3. The means for connecting the parent base station and the small-capacity base station includes a line termination device installed in the parent base station, a dedicated line, and a line termination device installed in the small-capacity base station. 2. The small-capacity base station control method according to claim 1, wherein: 4. A code division multiple access system comprising a mobile terminal, a parent base station composed of a service area divided into a plurality of sector cells, and a small capacity base station connected to the parent base station. A mobile communication system base station control method, wherein the parent base station performs radio communication with the mobile terminal located in a sector cell of the base station, and the small-capacity base station performs a service of the base station. Simultaneously performing wireless communication with the mobile terminal located in the area and transferring the wireless communication information to the parent base station; and wherein the mobile terminal has a sector cell area of the parent base station and a small capacity base station. When located in the overlap zone of the service area, the master base station transmits the wireless communication information of the master base station and the transferred wireless communication information of the small-capacity base station to a soft base station. A small-capacity base station control method, comprising a step of performing selective combining by handover processing. 5. The small-capacity base station control method according to claim 4, wherein the step of performing wireless communication with the small-capacity base station comprises devices for one sector of the parent base station. 6. The step of connecting the parent base station and the small-capacity base station includes a line termination device installed in the parent base station, a dedicated line, and a line termination device installed in the small-capacity base station. 5. The small capacity base station control method according to claim 4, wherein: