JP2001028779A - Mobile communication system and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system when a form of utilization is extended by effectively dividing an area of a mobile communication system adopting an area configuration of marco cell-micro cell with a degree of freedom and to provide its control method. SOLUTION: At least one micro base station 3 is placed in marco cells 1-1, 2-1 formed by marco cell base stations 1, 2 to form a micro cell by a micro base station 3 in the marco cells 1-1, 2-1 and an interference wave generating base station 4 placed at a prescribed position in the micro cell transmits an interference wave in a transmission timing of a control channel of the marco cell base stations 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system and a control method thereof, and more particularly, to a macro cell system.
The present invention relates to a mobile communication system and a control method thereof, in which the use form is expanded by effectively and flexibly dividing an area of a mobile communication system having a microcell area configuration.

[0002]

2. Description of the Related Art Conventionally, in a mobile communication system having such a macro cell-micro cell area configuration, a micro cell base station having a low transmission output is installed in a macro cell formed by the macro cell base station. By drawing a mobile communication device (hereinafter simply referred to as a terminal) existing in an area where the transmission electric field strength of the base station exceeds the transmission electric field strength of the macro cell base station to the micro cell base station,
An independent cell is created in a macro cell to distribute traffic in a traffic concentrated area.

According to this conventional mobile communication system having a macro cell-micro cell area configuration, the area of a micro cell base station depends on its transmission output, but the transmission of the macro cell base station is only in the immediate vicinity of the micro cell base station. Electric field strength cannot be exceeded.

[0004] In particular, in a city area, since there are many macrocell base stations in a narrow area, when a terminal monitors neighboring base stations and makes a call in order from a base station with a higher control channel level, The terminals that can be drawn into the microcell base station are narrowed down to an extremely narrow range.

FIG. 7 is a diagram showing a conventional mobile communication system having a macro cell-micro cell area configuration.

In FIG. 7, reference numerals 1 and 2 denote macro cell base stations, 3 denotes a micro cell base station, 1-1 denotes a cover area (macro cell) of the macro cell base station 1, and 2-1 denotes a cover area of the macro cell base station 2. (Macro cell), 3-
Reference numeral 1 denotes an actual coverage area (microcell) of the microcell base station 3.

Here, in a place where the electric field strength of the macrocell base stations 1 and 2 is strong and the number of overlaps between the macrocells 1-1 and 2-2 is large, the microcell base station 3 is in an electric field strength area where communication is possible. With respect to 3-2, only terminals within a very small area 3-1 can be drawn.

Further, when the purpose is to disperse traffic, it is necessary to install the microcell base station 3 or its antenna at the center of the point where the traffic is generated. It is very difficult to install the microcell base station 3 or its antenna at an optimum position.

Therefore, in order to avoid such a problem, a flag is set in the data of the control channel of the microcell base station 3, and the terminal is configured to preferentially call the control channel with the flag. Thus, a configuration has been proposed in which even if the microcell base station 3 and its antenna are somewhat away from the traffic concentration area, a terminal in that area can be pulled in.

However, in such a configuration, it is necessary for the terminal to correspond to the control channel flag, and since the terminal is forcibly pulled in to secure an area, the communication quality of the terminal connected just before the area is reduced. There is a problem that it is bad.

FIG. 8 is a diagram for explaining the above problem in a conventional mobile communication system having a macro cell-micro cell area configuration.

In FIG. 8, reference numerals 1 and 2 denote macro cell base stations, 3 denotes a micro cell base station, 1-1 denotes a coverage area (macro cell) of the macro cell base station 1, and 2-1 denotes a coverage area of the macro cell base station 2. (Macro cell). Reference numeral 3-3 denotes a range in which the communication area fluctuates due to fading or the like.

Here, when a flag is set and an attempt is made to forcibly bring the mobile communication device into the microcell base station 3,
A terminal located at the very end of the area 3-2 is also drawn into the microcell base station 3, and the communication quality of the terminal in that case becomes very poor.

[0014]

As described above, in a conventional mobile communication system having a macro cell-micro cell area configuration, the area in which a terminal can be drawn into the micro cell base station 3 becomes extremely narrow, There was a problem that call quality deteriorated.

Therefore, the present invention provides a mobile communication system in which the area of use of a mobile communication system having a macro cell-micro cell area configuration is effectively and flexibly divided to expand the usage form, and a control method therefor. The purpose is to:

[0016]

In order to achieve the above object, according to the first aspect of the present invention, a macro cell base station and all base stations including the macro cell base station are synchronized with each other at a frequency independent of a communication channel. In a TDMA mobile communication system for allocating a communication channel with a mobile communication device using a control channel having a slot,
At least one micro base station is arranged in a macro cell formed by the macro cell base station to form a micro cell by the micro base station in the macro cell, and the macro cell base station is located at a predetermined position in the micro cell. An interference wave transmitting means for transmitting an interference wave at a transmission timing of a control channel of a station is arranged, and the macrocell base station is provided in a mobile communication device existing in the microcell and in an area affected by the interference wave by the interference wave transmitting means. Are selectively assigned.

According to a second aspect of the present invention, in the first aspect, the interference wave transmitting means transmits the interference wave at a transmission timing of a frame identification code of the control channel of the macro cell base station. It is characterized by doing.

According to a third aspect of the present invention, in the first aspect of the present invention, the interference wave transmitting means includes means for changing the area affected by the interference wave by adjusting the transmission power of the interference wave. It is characterized by having.

According to a fourth aspect of the present invention, there is provided a mobile communication system using a control channel having a slot in which a macrocell base station and all base stations including the macrocell base station are synchronized with each other at a frequency independent of a communication channel. In the mobile communication control method of the TDMA system for allocating a communication channel to a mobile station, at least one micro base station is arranged in a macro cell formed by the macro cell base station, and the micro cell by the micro base station is allocated to the micro base station. An interference wave is formed in a macrocell, and an interference wave is transmitted at a transmission timing of a control channel of the macrocell base station from an interference wave transmission unit arranged at a predetermined position in the microcell, and the interference wave is transmitted in the microcell and the interference wave. A communication channel of the macrocell base station is provided to a mobile communication device existing in the area affected by the interference wave by the transmitting means. And wherein selectively assigning the channel.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the interference wave transmitting means transmits the interference wave at a transmission timing of a frame identification code of a control channel of the macrocell base station. It is characterized by the following.

According to a sixth aspect of the present invention, in the fourth aspect of the invention, the interference wave transmitting means changes an area affected by the interference wave by adjusting a transmission power of the interference wave. It is characterized by doing.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a mobile communication system and a control method according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an area configuration diagram of a mobile communication system configured by applying the mobile communication system and the control method according to the present invention.

In FIG. 1, the same reference numerals as those used in FIG. 7 or FIG. 8 are used for parts common to those shown in FIG. 7 or FIG.

In FIG. 1, reference numerals 1 and 2 denote a macro cell base station, 3 denotes a micro cell base station, 1-1 denotes a cover area (macro cell) of the macro cell base station 1, and 2-1 denotes a cover area of the macro cell base station 2. (Macro cell), 3-
Numeral 2 denotes an electric field strength area of the microcell base station 3 where communication is possible.

Reference numeral 4 denotes an interference wave generating base station provided in the field strength area 3-2 of the microcell base station 3 where communication is possible, and 4-1 denotes an interference wave generated from the interference wave generating base station 4. The affected area.

In the above configuration, the macro cell base stations 1 and 2 and the micro cell base station 3 communicate with the mobile communication device using a control channel having slots synchronized with each other at a frequency independent of the communication channel. A mobile communication system of the TDMA system for allocating the traffic channel of the TDMA system.

FIG. 2 is an enlarged view showing the periphery of the microcell base station 3 of the mobile communication system shown in FIG.

In FIG. 2, the base station 4 for generating the interference wave is the field strength
Terminal (mobile communication device)
5 transmits the interference wave at the transmission timing of the control channel of the macrocell base stations 1 and 2 with which communication is possible.

The size of the area 4-1 affected by the interference wave of the interference wave generation base station 4 can be changed by adjusting the transmission level of the interference wave transmitted from the interference wave generation base station 4. .

However, the influence area 4-1 of the interference wave of the interference wave generating base station 4 is within a range in which the communication area fluctuates due to fading or the like within the field strength area 3-2 in which the microcell base station 3 can originally talk. The transmission level of the interference wave transmitted from the interference wave generation base station 4 is adjusted so as to be in a range excluding 3-3.

Here, the terminal 5 existing in the interference wave affected area 4-1 of the interference wave generating base station 4 is affected by the interference wave transmitted from the interference wave generating base station 4, and Since the control channels 1 and 2 are masked, signals transmitted from the macro cell base stations 1 and 2 on the control channel cannot be received.

Therefore, the terminal 5 existing in the interference wave affected area 4-1 of the interference wave generating base station 4 selectively receives the signal transmitted on the control channel of the microcell base station 3. And selectively drawn into the microcell base station 3.

That is, the terminal 5 existing in the area 4-1 affected by the interference wave of the interference wave generating base station 4 transmits the interference wave 4a transmitted from the interference wave generating base station 4 to the micro cell base station 3. And selectively receives signals transmitted on the control channel of the micro cell base station 1 or 2 even if the reception strength of the macro cell base stations 1 and 2 is greater than the reception strength of the micro cell base station 3. 3a can be established.

FIG. 3 shows the terminal (mobile communication device) shown in FIG.
5 is a block diagram showing a detailed configuration of No. 5. FIG.

In FIG. 3, this terminal (mobile communication device) 5
Includes an antenna 51, a transmission / reception unit 52, a communication control unit 53, an audio processing unit 54, a speaker 55, a microphone 56, a bus 57, a read only memory (ROM) 58, a random access memory (RAM) 59, a control unit 60, and a key input. It comprises a unit 61, a display unit 62, a driver 63, an oscillation circuit 64, a sounder 65, and a battery 66.

Here, the transmitting / receiving unit 52, the communication control unit 53,
Voice processing unit 54, read-only memory (ROM) 5
8, random access memory (RAM) 59, control unit 6
0 is connected via a bus 57.

An antenna 51 is connected to the transmission / reception unit 52, a speaker 55 and a microphone 56 constituting a handset are connected to the audio processing unit 54, and a control unit 60
Is connected to a key input unit 61, a display unit 62, and a driver 63, and the driver 63 has an oscillation circuit 64 and a sounder 6.
5 is connected.

The transmission / reception unit 52 is composed of a transmission circuit and a reception circuit each having a frequency conversion unit and a modem (not shown). The frequency conversion units of the transmission circuit and the reception circuit are connected via an antenna switch (not shown). Connected to antenna 51.

The frequency conversion unit of the reception side circuit of the transmission / reception unit 52 takes in the signal received by the antenna 51 via the antenna switch and mixes it with a local oscillation signal of a predetermined frequency output from the PLL synthesizer, for example, The 1.9 GHz band received signal is converted to an IF near the 1 MHz band.
(Intermediate frequency) Frequency conversion to a signal.

The frequency converter of the transmitting side circuit of the transmitter / receiver 52 is provided with a π / 4 shift QPSK supplied from the modem.
Is mixed with a local oscillation signal of a predetermined frequency output from a PLL synthesizer to obtain a frequency of 1.9 GHz.
The frequency is converted to a band signal and transmitted from the antenna 51.

The modem of the receiving side circuit of the transmitting / receiving section 52 demodulates the IF signal from the frequency converting section, separates the IF signal into IQ data, and sends it to the communication control section 53 as a data string.

The modem of the receiving side circuit of the transmitting / receiving section 52 creates IQ data from the data supplied from the communication control section 51, modulates the data by π / 4 shift QPSK, and modulates the frequency data by the frequency modulation section of the transmitting side circuit. Send to

The communication control section 53 is composed of a transmitting side processing section and a receiving side processing section (not shown), and performs frame synchronization of transmission / reception signals and data format of slots.

That is, the receiving-side processing unit of the communication control unit 51 extracts data for one slot from the received data supplied from the modem of the transmitting and receiving unit 52 at a predetermined timing, and from this data, a unique word (synchronization signal). ) Is extracted to generate a frame synchronization signal, and after descrambling the control data and the audio data, the control data is sent to the control unit 60, and the audio data is sent to the audio processing unit 5.
4

The transmitting side processing unit of the communication control unit 53
Control data and the like are added to the audio data supplied from the audio processing unit 54, a predetermined scrambling process is performed on the control data, a unique word and the like are added, and transmission data for one slot is created. It is inserted into a predetermined slot in the transmission frame at the timing and transmitted to the modem of the transmission / reception unit 52.

The audio processing section 54 is composed of a speech codec and a PCM codec (not shown).

Here, the speech codec performs compression / expansion processing of digital data. On the transmission side, an ADPCM audio signal (4 bits × 8 KHz = 32 Kbps) supplied from the communication control unit 13 is converted to a PCM audio signal ( It is expanded by decoding to 8 bits × 8 KHz = 64 Kbps and output to the PCM codec.

On the receiving side of the speech codec, the PCM audio signal supplied from the PCM codec is encoded into an ADPCM audio signal, compressed and transmitted to the communication control unit 53.

The PCM codec performs an analog / digital conversion process. On the receiving side, a PCM audio signal (digital signal) supplied from the speech codec is converted into an analog signal, and is output from the speaker 55. , Converts the analog audio signal input from the microphone 56 into a PCM signal and sends it to the speech codec.

The key input section 61 is composed of a dial key for inputting a telephone number of a destination (a destination), a volume switch for changing a voice output, and the like. The state of these keys and switches is detected by the control section 60.

The control unit 60 is composed of a microprocessor or the like, and has a predetermined operation system (OS).
And the overall operation of the terminal 5 according to a predetermined program.

The driver 63 is driven at the time of the incoming call 2 under the control of the control unit 60, and adds a signal corresponding to the ringing tone output from the oscillation circuit 64 to the sounder 65.
Generate ringtone from.

The ROM 58 and the RAM 59 include:
An OS, a program, various parameters, and the like executed by the control unit 60 are stored. Note that the storage of the RAM 58 is held by a power supply from the battery 66. The battery 66 supplies power to each part of the terminal 5.

FIG. 4 is a block diagram showing a detailed configuration of the interference wave generating base station 4 shown in FIG. 1 and FIG.

In FIG. 4, this interference wave generating base station 4
Monitors the control channels of the macro cell base stations 1 and 2 and the control channel of the micro cell base station 3, and transmits interference waves at the transmission timing of the control channels of the macro cell base stations 1 and 2.

That is, the interference wave generating base station 4 includes an antenna 41, a transmitting / receiving unit 42, a communication control unit 43, a control unit 44,
Interference wave generation section 45, interference wave level setting section 46, power supply section 4
7 is provided.

Here, the control unit 44 monitors the control channels of the macro cell base stations 1 and 2 and the control channel of the micro cell base station 3 via the antenna 42, the transmission / reception unit 42, and the communication control unit 43, and generates an interference wave. A signal corresponding to the interference wave generated from the unit 45 is added to the communication control unit 432, and the interference wave is transmitted at the transmission level set by the interference wave level setting unit 46 and at the transmission timing of the control channels of the macrocell base stations 1 and 2. Communication control unit 43, transmitting / receiving unit 42, antenna 41
To send over.

FIG. 5 is a block diagram showing the interference wave generating base station 4 shown in FIG.
FIG. 3 is a diagram showing transmission timings of interference waves transmitted from the STA.

In FIG. 5, (a) shows TDMA-T
2 shows a slot configuration of a DD communication system;
Here, the control channel transmission timing of the macro cell base stations 1 and 2 uses slots 1 to 3 of the transmission slot Tx, and the control channel transmission timing of the micro cell base station 3 uses slot 4.

Therefore, the interference wave generating base station 4 transmits the interference wave at the timing of the slots 1 to 3 of the transmission slot Tx, which is the control channel transmission timing of the macro cell base stations 1 and 2, and controls the micro cell base station 3. At the timing of slot 4, which is the channel transmission timing, no interference wave is transmitted.

Note that the transmission slot of the control channel of the macro cell base stations 1 and 2 may be different from the transmission slot of the control channel of the micro cell base station 3 depending on the system configuration. This can be dealt with by matching the transmission slots of the control channels of the macrocell base stations 1 and 2.

FIG. 6 shows the interference wave generating base station 4 shown in FIG.
FIG. 7 is a diagram showing a relationship between transmission timing of an interference wave transmitted from a GW and a control channel frame configuration in a slot.

FIG. 6A shows a PHS control frame. Here, the interference wave does not need to cause interference in the entire control frame, and it is sufficient that the terminal 5 does not receive a part of the frame recognition code indicated as a unique word. A few bits are sufficient.

This means that the average transmission power is very small, and the power consumption can be reduced. Therefore, the power supply unit 47 of the interference wave generation base station 4 shown in FIG.
In addition, the solar cell and the small battery can be operated independently, and the degree of freedom of the installation location can be greatly increased. Further, by incorporating a clock function and the like, it is also possible to transmit an interference wave only in a time zone where traffic is concentrated, and to take measures against traffic.

As described above, in the present embodiment, it is possible to draw a terminal in an arbitrary area to the microcell base station 3 by transmitting an interference wave. Even when it is difficult to install a cell base station, traffic countermeasures can be taken by installing a base station in the periphery and transmitting an interference wave near the center of the traffic concentration area.

This is very effective for dispersing traffic at very limited points such as a station or a meeting spot currently occurring in an urban area.

[0068]

As described above, according to the present invention,
At least one micro base station is arranged in a macro cell formed by the macro cell base station to form a micro cell by the micro base station in the macro cell, and an interference wave transmitting means arranged at a predetermined position in the micro cell Since the interference wave is configured to be transmitted at the transmission timing of the control channel of the macro cell base station from, the mobile communication device in an arbitrary area can be connected to the micro cell base station within an area where the electric field strength enough to maintain sufficient communication quality can be guaranteed. The mobile station can be drawn into the station, and this makes it possible to effectively and flexibly perform the area division of the mobile communication system having the macro cell-micro cell area configuration, so that the use form can be greatly expanded. It works.

[Brief description of the drawings]

FIG. 1 is an area configuration diagram of a mobile communication system configured by applying a mobile communication system and a control method thereof according to the present invention.

FIG. 2 is an enlarged view showing a periphery of a microcell base station 3 of the mobile communication system shown in FIG.

FIG. 3 is a block diagram showing a detailed configuration of a terminal (mobile communication device) 5 shown in FIG.

FIG. 4 is a block diagram showing a detailed configuration of an interference wave generating base station 4 shown in FIGS. 1 and 2;

FIG. 5 is a diagram illustrating transmission timings of interference waves transmitted from the interference wave generation base station 4 illustrated in FIG.

6 is a diagram showing a relationship between transmission timing of an interference wave transmitted from the interference wave generation base station 4 shown in FIG. 4 and a control channel frame configuration in a slot.

FIG. 7 is a diagram showing a conventional mobile communication system having a macro cell-micro cell area configuration.

FIG. 8 is a diagram illustrating the above problem in a conventional mobile communication system having a macro cell-micro cell area configuration.

[Explanation of symbols]

1, 2 Macrocell base station 1-1, 2-1 Coverage area of macrocell base station (macrocell) 3 Microcell base station 3-2 Electric field strength area where microcell base station can originally talk 4 Interference wave generating base station 4- 1 Influence area of interference wave generated from interference wave generation base station 41 Antenna 42 Transmission / reception unit 43 Communication control unit 44 Control unit 45 Interference wave generation unit 46 Interference wave level setting unit 47 Power supply unit 5 Terminal (mobile communication device) 51 Antenna 52 Transmission / reception unit 53 Communication control unit 54 Audio processing unit 55 Speaker 56 Microphone 57 Bus 58 Read only memory (ROM) 59 Random access memory (RAM) 60 Control unit 61 Key input unit 62 Display unit 63 Driver 64 Oscillator circuit 65 Sounder 66 Battery

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumi Doi 3-1, 1-1 Asahigaoka, Hino-shi, Tokyo Toshiba Abu E Co., Ltd. Hino Office (72) Inventor Tadamasa Goto Asahigaoka, Hino-shi, Tokyo Takano Sato, inventor Takashi Sato 3-1-1, Asahigaoka, Hino-shi, Tokyo Toshiba Communication Technology Co., Ltd. F-term (reference) 5K067 AA12 BB02 CC04 DD13 DD25 DD27 DD34 EE02 EE10 EE54 GG03 GG08 HH05 JJ13

Claims (6)

[Claims] 1. A communication channel between a mobile communication device and a base station using a control channel having slots synchronized with each other at a frequency independent of the communication channel by a macrocell base station and all base stations including the macrocell base station. T to assign
In a mobile communication system of a DMA system, at least one of the micro base stations is arranged in a macro cell formed by the macro cell base station, and a micro cell by the micro base station is formed in the macro cell. At a predetermined position, an interference wave transmitting means for transmitting an interference wave at a transmission timing of a control channel of the macrocell base station is arranged, and is present in the microcell and in an area affected by the interference wave by the interference wave transmitting means. A mobile communication system, wherein a communication channel of the macro cell base station is selectively assigned to a mobile communication device. 2. The mobile communication system according to claim 1, wherein said interference wave transmitting means transmits said interference wave at a transmission timing of a frame identification code of said control channel of said macro cell base station. 3. The mobile communication system according to claim 1, wherein the interference wave transmitting unit includes a unit that changes an influence area of the interference wave by adjusting a transmission power of the interference wave. 4. A communication channel between a mobile communication device and a macrocell base station using a control channel having slots synchronized with each other at a frequency independent of the communication channel by a macrocell base station and all base stations including the macrocell base station. T to assign
In the mobile communication control method of the DMA system, at least one of the micro base stations is arranged in a macro cell formed by the macro cell base station, and a micro cell by the micro base station is formed in the macro cell. Transmitting an interference wave at a transmission timing of a control channel of the macrocell base station from an interference wave transmitting unit disposed at a predetermined position of the macrocell base station; and present in the microcell and within an area affected by the interference wave by the interference wave transmitting unit. A method for selectively allocating a communication channel of the macrocell base station to a mobile communication device to be controlled. 5. The control method for a mobile communication system according to claim 4, wherein said interference wave transmitting means transmits said interference wave at a transmission timing of a frame identification code of a control channel of said macro cell base station. . 6. The control of a mobile communication system according to claim 4, wherein said interference wave transmitting means comprises changing an area affected by said interference wave by adjusting a transmission power of said interference wave. Method.