JP2669288B2 - Integrated micro / macro cell mobile communication system - Google Patents

Abstract

PURPOSE:To provide an integrated mobile communication system which can have selective accesses to both a microcell and a macrocell through a single terminal. CONSTITUTION:A service area consists of plural microcells 12 and the macrocells which cover the microcells 12. A mobile terminal 16 has accesses to these microceells 12 and macrocells 11 via a common radio interface and moves at a walking speed or less to have the communication with a microcell base station 13. Meanwhile a mobile terminal 15 moves at a speed lower than that of the terminal 16 has the communication with a macrocell base station 14 respectively. Then each station 13 transmits a radio control channel in synchronism with the radio control channel which is transmitted in time division by the station 14. The mobile terminal included in the macrocell 11 repetitively measures the reception level of the radio control channel of the station 13 and decides the station 13 or 14 based on the moving speed estimated by the varying speed of the preceding reception level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a land mobile communication system provided by two independent systems represented by a car telephone and a cordless telephone. By integrating these two systems, the mobile terminal's battery life and frequency utilization efficiency can be improved, and one terminal can access these two systems. The present invention relates to the configuration of a radio control channel and estimation of the moving speed of a mobile terminal for that purpose.

[0002]

2. Description of the Related Art The present land mobile communication system is roughly divided into a macro cell cell structure, a cellular car telephone system for users moving at high speed, and a cell structure microcell for low speed. Is provided with two independent wireless interfaces and a network configuration for a cordless telephone system intended for mobile users. Therefore, when using these systems, the user had to have two different mobile terminals.

In a conventional cellular land mobile communication system composed of macro cells, the radius of a cell is equal to 0.
The communication between the mobile terminal and the serving macrocell base station is several hundred meters.
This is performed via a wireless line with a transmission output of about W to several W. As described above, since the transmission power from the mobile terminal is large, the power consumption of the mobile terminal is also large, and the duration of the battery is limited to about one day. Further, since the cell radius is large, it is necessary to increase the frequency reuse distance, and the number of simultaneous call subscribers is inferior to the micro cell system described below. However, since the cell radius is large, radio line switching that occurs when moving between cells is reduced, which is an advantageous system for mobile terminals that move at high speed.

On the other hand, a cordless telephone system is constituted by microcells having a cell radius of several tens to hundreds of meters. Therefore, the frequency reuse distance can be reduced, and the number of simultaneous call subscribers can be increased as compared with the macro cell system described above. In addition, since the cell radius is small, the mobile terminal can communicate with the serving microcell base station via a wireless line with a low transmission output of about several mW, and the battery duration of the mobile terminal is It will be about one week. However, since the cell radius is small, radio line switching frequently occurs for a mobile terminal moving at high speed, and the control for this is very complicated. The target moving speed is about the speed of a pedestrian.

FIG. 6 shows an example of base station configuration in the prior art. 64 is a cell which is a micro cell or a macro cell, 65 is a radio controller for controlling a radio channel, 66
Is a central controller and 67 is a base station.

Conventionally, a base station having such a configuration has been individually provided for a micro cell and a macro cell.

[0007]

As described above, the cellular mobile communication system composed of macro cells and the cordless telephone system composed of micro cells differ in the moving speed of the mobile terminal handled by each system. Are configured by different systems. Therefore, in order to access these systems, it is necessary to use dedicated mobile terminals, which is inconvenient for the user.

A cordless telephone system composed of microcells is superior to a cellular car telephone system composed of macrocells from the viewpoints of effective use of frequency and battery life of mobile terminals. Since the radius is small, it has a drawback that it can be handled only by a user who moves at a low speed and has a small number of handovers.

[0009] On the other hand, a cellular automobile system composed of macro cells has a large cell radius.
Although it has the advantage of being able to handle users moving at high speed, it has the disadvantage of being inferior to microsystems in terms of effective use of frequency and battery life of mobile terminals due to the large cell radius. Have.

Further, since the mobile terminal of the cellular mobile communication system is handled in macro cell units regardless of the moving speed, even if the mobile terminal is used as a mobile terminal of a cordless telephone system, the frequency repetition distance is longer than necessary. Has the drawback of being secured.

The present invention solves the above-mentioned drawbacks.
It is an object of the present invention to provide an integrated mobile communication system in which one terminal can selectively access both a micro cell and a macro cell.

[0012]

SUMMARY OF THE INVENTION A feature of the present invention is that a service area is covered by a plurality of microcells of a first size, and the same service area is covered by a plurality of macrocells of a second size larger than the microcell. Has a cell configuration that covers the microcells, a common radio interface is used to access these two cells, and a mobile terminal that moves at a first speed equal to or lower than a walking speed is provided for each microcell. The mobile terminal that communicates with the installed microcell base station via the wireless line, and the mobile terminal that moves at the second speed faster than the first speed communicates with the macrocell base station installed for each macrocell via the wireless line. Each macro cell base station in the macro cell synchronizes with the frame of the radio control channel transmitted by the macro cell base station in a time division manner. By transmitting in a time division Le,
A mobile terminal located in a macro cell is synchronized with a time division control signal transmitted from each micro cell base station arranged in the macro cell, and radio of a micro cell base station receivable on a predetermined frequency and slot. The reception level of the control channel is repeatedly measured, the moving speed of the mobile terminal is estimated from the speed at which those reception levels fluctuate, and the mobile terminal selects one of the macrocell base station and the microcell base station according to the estimated moving speed. In the integrated microcell / macrocell mobile communication system for selectively accessing

[0013]

The present invention relates to a mobile communication system having a cell structure that integrates a micro cell and a macro cell according to a common radio interface. In the present invention, since a mobile terminal accesses a base station having a different cell size according to a moving speed, a radio control channel access method of selecting / switching between a macro cell base station and a micro cell base station becomes a problem. Further, when a call is received to the mobile terminal, the mobile terminal needs to be waiting for a paging channel for notifying the incoming call, and the transmission method of the paging channel from the base station poses a problem.

In the present invention, the mobile terminal autonomously estimates the moving speed of the mobile terminal. The mobile terminal measures the reception levels of a plurality of radio control channels transmitted from the microcell base station and their temporal variations during standby and during communication. The fluctuation speed of the reception level is very fast during high-speed movement, and changes slowly during low-speed movement. The mobile terminal
The moving speed is determined by comparing the measured fluctuation speed with the magnitude relationship between the predetermined set value. In order to perform this measurement accurately, it is necessary to synchronize the radio control channel between the microcell base stations. This is synchronized with the radio control channel frame transmitted from the macrocell base station in a time-division manner.
This is possible because each microcell base station in the macrocell transmits the radio control channel in a time division manner, and the mobile terminal located in the macrocell can measure the reception level of the control signal transmitted from the neighboring microcell base stations. By doing so, the mobile terminal autonomously estimates the moving speed.

In a general mobile communication system, a base station transmits, as control signals, a broadcast information channel for broadcasting system information, a paging channel for performing an incoming call, and a response signal to a call request from a mobile terminal. Is done. The mobile terminal transmits a call request and a response signal to the paging channel from the base station.

According to the present invention, the macrocell base station transmits a broadcast information channel for a mobile terminal moving at a high speed located in the macrocell and a paging channel for all mobile terminals located in the macrocell. In addition, the microcell base station transmits a broadcast information channel for a mobile terminal that moves in the microcell and moves at a low speed.

When the mobile terminal on standby is moving at a low speed, the paging channel transmitted from the serving macrocell base station and the broadcast information channel transmitted from the serving microcell are moved at high speed. If so, the paging channel and the broadcast information channel transmitted from the serving macrocell base station are intermittently received. Further, in order to determine the transition between cells, the mobile terminal moving at a low speed measures the reception level of the broadcast information channel of the peripheral microcell, and the mobile terminal moving at a high speed measures the reception level of the broadcast information channel of the peripheral macrocell. . Further, the mobile terminal moving at high speed periodically estimates the moving speed and periodically confirms the change in the moving speed. When the moving speed of the mobile terminal changes from a low speed to a high speed, it becomes difficult for the mobile terminal to receive the radio control channel transmitted from the microcell base station. Start estimation of. The mobile terminal measures the reception level of the radio control channel of the microcell base station for determining the movement between the microcells, and estimates the moving speed using the measurement result.

At the time of calling from a mobile station, the mobile terminal selects a microcell base station if the speed is low and a macrocell base station if the speed is high based on the autonomously estimated moving speed. At the time of incoming call to the mobile station, the mobile terminal receives the paging channel transmitted from the macrocell base station, and sends a response signal to the paging channel to the existing macrocell base station when moving at low speed. If so, the communication is started after transmitting to the microcell base station in the area.

[0019]

Embodiment 1 FIG. 1 shows a cell configuration of an integrated micro cell / macro cell mobile communication system according to the present invention.

11 is a macro cell, 12 is a micro cell,
13 is a micro cell base station, 14 is a macro cell base station,
Reference numeral 15 indicates a mobile terminal that moves at high speed, and 16 indicates a mobile terminal that moves at low speed. FIG. 1 shows the service area as a macro cell 1
The cell structure is covered by repeating 1 and repeating microcell 12. The mobile terminal 15 moving at a high speed includes the macrocell base station 11 and the mobile terminal 16 moving at a low speed.
Communicates with the microcell base station 13 using a common wireless interface.

FIG. 2 is a diagram for explaining the moving speed estimating method according to the present invention. Reference numerals 21a to 21g denote numbers for identifying the radio control channels transmitted from the micro cell base station existing in the macro cell in synchronization with the frame of the radio control channel of the macro cell base station. Radio control channel 21
a to 21g are repeatedly reused in microcells separated by a distance that does not interfere with each other. 22 is an example of a movement route of a mobile terminal moving at a high speed, 23 is an example of a movement route of a mobile terminal moving at a low speed within the same time as 22 and 2
4 is time T # (# of the mobile terminal moving on the moving route 22;
= 1 to 6), the temporal change of the reception levels of the radio control channels 21 a to 21 g,
7 shows how the reception levels of the radio control channels 21a to 21g of the mobile terminal moving above move at time T # (# = 1 to 6). In tables 24 and 25,
The radio control channel with the highest reception level at each time is indicated by diagonal lines.

The mobile terminal at the time of standby measures the reception level of the radio control channel on a predetermined frequency and slot, and prepares a table 24 or 25 of the measurement result including their temporal fluctuation.

In the table 24 of the measurement result of the mobile terminal moving at high speed, the radio control channel having the maximum measured reception level is the radio control channel 21a when the mobile terminal is at the position A of the moving route 22 at time T1. It is. Similarly, the radio control channel 21g at time T2 (position B) and the radio control channel 21g at time T3 (position C)
d, at time T4 (position D), the radio control channel 21a,
The radio control channel 21g at time T5 (position E) and the radio control channel 21d at time T6 (position F) are the radio control channels at which the reception level becomes the maximum value at each time. In the case of the mobile terminal moving at high speed shown in Table 24, the radio control channel having the maximum reception level fluctuates five times within times T1 to T6.

On the other hand, in the measurement result table 25 of the mobile terminal moving at a low speed, the fluctuation of the radio control channel having the maximum reception level within the measurement time T1 to T6 indicates that the radio control channel 21f changes from the radio control channel 21f at the position H. 21
e, which changes only once, and the change is slow compared to the table 24 of the mobile terminal moving at high speed.

Here, a threshold value is set for the time at which the radio control channel at which the reception level becomes the maximum is switched, and the result is compared with the measurement result by the mobile terminal. Make a decision.

In the standby mode, the mobile terminal moving at a low speed intermittently receives the broadcast information channel transmitted from the microcell base station. In this case, the reception quality of the broadcast information channel deteriorates, and it becomes difficult for the mobile terminal to resynchronize with the control signal transmitted from the microcell base station in the visited area or the destination. To that end, with that as a trigger,
The mobile terminal can start estimating the moving speed according to the above procedure. On the other hand, a mobile terminal that moves at a high speed has intermittently received a broadcast information channel transmitted from a macrocell base station, and it is difficult to determine the speed of the mobile terminal using only the information received thereby. A separate trigger is required to start the estimation. For this purpose, a mobile terminal that moves at a high speed autonomously estimates the moving speed at regular time intervals, and determines whether the moving speed is high or low.

According to this method, the mobile terminal transmits a high transmission power to the macrocell base station at high speed according to the moving speed,
At low speed, communication is performed with low transmission output to the microcell base station. Therefore, the interference amount of the same frequency is reduced,
The frequency can be used effectively.

[0028]

Embodiment 2 FIG. 3 shows an example of the configuration of an integrated micro-cell / macro-cell mobile communication system according to the present invention.

Reference numeral 31 is a paging channel transmitted from the macrocell base station to call the mobile terminal when an incoming call is made to the mobile terminal, and 32 is a control signal transmitted between the macrocell base station and the mobile terminal moving at high speed. And communication signals,
33 is a control signal and a communication signal performed between the microcell base station and the mobile terminal moving at a low speed.

When a call is made from the mobile terminal, the mobile terminal 16 moving at a low speed accesses the microcell base station 13 and, after a predetermined control sequence, the microcell base station 1
3 starts communication. The mobile terminal 15 moving at high speed accesses the macrocell base station 14 and starts communication with the macrocell base station 14 after a predetermined control sequence.

When receiving an incoming call to a mobile terminal, a paging channel for calling the mobile terminal is transmitted from the macrocell base station 14. The mobile terminal that has received the paging channel transmits a response signal to the microcell base station 13 at a low speed and starts communication with the microcell base station 13 after a predetermined control sequence. Further, at high speed, a response signal is transmitted to the macrocell base station 14, and after a predetermined sequence, communication with the macrocell base station 14 is started.

A mobile terminal during communication performs a handover for switching a base station according to a moving speed. When the speed of the mobile terminal changes from low speed to high speed during communication, the time margin until the mobile terminal moves outside the serving microcell is limited, and the wireless line switching between multiple microcells Therefore, high-speed handover is required. Under such circumstances, there is not always enough time to estimate the moving speed. Therefore, when a mobile terminal moving at low speed moves out of the micro cell, the mobile terminal first starts inter-micro cell handover. However, when the mobile terminal is moving at high speed, the mobile terminal further moves to another microcell before the inter-microcell handover process ends, and the inter-microcell handover fails. Probability is high. In such a case, the mobile terminal determines that the moving speed has changed from low speed to high speed, and sends a handover request to the macrocell base station in the area, thereby moving the base station from the microcell base station to the macrocell base station. Perform a handover to switch to the base station. On the other hand, a mobile terminal moving at high speed can estimate the moving speed periodically during communication as well as during standby. Therefore, when the speed of the mobile terminal changes to a low speed, the mobile terminal sends a handover request to the macrocell base station to switch the communication destination base station from the macrocell base station to the microcell base station. Perform over.

FIG. 4 shows a configuration example of a base station for realizing this embodiment. 41 is a central controller, 42 is a macro cell radio controller that performs radio management of mobile terminals that move at a low speed, 43 is a micro cell radio controller that performs radio management of mobile terminals that move at a high speed, and 44 is a public line. A cross-connect switch for switching the communication channel for communication between the communication channel for the micro cell and the communication channel for the macro cell, and 45 is a public line. In this embodiment, transmission / reception signals at the microcell base station 13 existing in the macrocell are concentrated to the macrocell base station 14.

Radio management of mobile terminals located in the macro cell is performed by the micro cell radio controller 43 for mobile terminals moving at low speed and by the macro cell radio controller 42 for mobile terminals moving at high speed. It is.

When an incoming call is made to a mobile terminal, the macro base station 14 transmits a paging channel for calling the called mobile terminal. The mobile terminal called from the macrocell base station 14 is a mobile terminal that moves at a low speed according to the moving speed estimated autonomously.
To start communication via the communication channel assigned by the microcell wireless controller 43.
Further, the mobile terminal moving at high speed transmits a response signal to the macrocell base station 14 and starts communication via the communication channel assigned by the macrocell radio controller 42.

According to the above configuration, since the paging channel is always transmitted from the macrocell base station 14, the mobile terminal does not need to notify the base station side of speed information every time the moving speed changes, The burden on the base station side for managing the moving speed is reduced.

Handover when a mobile terminal maintaining a constant moving speed moves between cells is managed by the macro cell radio controller 42 or the micro cell radio controller 43 according to the moving speed. The radio control of the handover accompanying the movement of the mobile terminal moving at a low speed between the microcells is performed by the microcell radio controller 43. Also,
The radio management of the handover accompanying the movement of the mobile terminal moving at high speed between the macro cells is performed by the macro cell radio controller 42 of the serving macro cell base station and the macro cell base station 14 to which the mobile terminal moves.

When the moving speed changes during communication, the macrocell base station 14 to the microcell base station 13 or the microcell base station 1 responds to the change in the moving speed.
Handover from 3 to the macrocell base station 14 occurs. When the moving speed of the mobile terminal changes from high speed to low speed, the macro cell base station 14
Handover to switch to 3 occurs. In the macrocell base station 14 that has received the handover request transmitted from the mobile terminal, the microcell controller 43 via the central controller 41 allocates the switching destination communication channel. Based on the allocation result, the mobile terminal determines that the macrocell base station 14
From the mobile station to the microcell base station 13 performs a handover for switching the communication channel. When the moving speed of the mobile terminal changes from low speed to high speed, the mobile terminal sends a handover request to the macrocell base station 14. In the macrocell base station 14 which has received the handover request, the macrocell radio controller 42 via the central controller 41
Assigns the switching destination communication channel. Based on the allocation result, the mobile terminal performs a handover for switching the communication channel from the micro cell base station 13 to the macro cell base station 14. According to the instruction of the central controller of 41, 44
Cross-connect switch switches the communication channel connected to the 45 public lines between the communication channel for the micro cell and the communication channel for the macro cell.

FIG. 5 shows a configuration example of a mobile terminal for realizing this embodiment. 51 is an antenna, 52 is a transmission / reception splitter that separates / combines a transmission signal and a reception signal, 53 is an up-converter, 54 is a modulator, 55 is a TDMA circuit that manages time-division signals, and 56 is audio coding. Voice code to do
C, 57 are a handset, 58 is a down converter, 59 is a demodulator, 60 is a level measuring device for measuring the level of a received signal, 61 is a moving speed estimator for estimating a moving speed, 62 is a communication channel and a radio control channel. It is a synthesizer that sets the frequency of. The level measurement device 60 determines a base station to be a standby station when the power is turned on, monitors the reception level of the communication channel during communication, monitors the reception level of the radio control channel of another base station during communication, and estimates the moving speed. Perform level measurement for

In accordance with the frequency and slot of the communication channel allocated by the base station, the control circuit of 63
5 TDMA circuits and 62 synthesizers are activated.
Switching between 4 modulators and 55 demodulators and 56 audio CODs
Perform EC management.

The mobile terminal during standby and during communication uses a vacant slot which is not used for receiving the radio control channel or the communication channel, and uses the level measuring device of 60 to detect the presence of a micro-locator for the moving area. The level of the radio control channel transmitted from the microcell base station located around the cell is measured. The result measured by the 60 level measuring device is sent to the moving speed estimator at 61. The moving speed estimator 61 calculates the time at which the radio control channel at which the reception level is maximized is switched, and compares the calculated result with a threshold value to estimate the moving speed. The obtained estimation result is notified to 63 control circuits. When a change in the moving speed is detected during communication, the mobile terminal notifies the existing macrocell base station of the change in the moving speed. If a change in the moving speed is detected during standby, the mobile terminal switches a base station to be accessed at the time of calling between the macro cell base station and the micro cell base station.

[0042]

As described above, according to the moving speed estimation method, the wireless control channel configuration method, and the mobile terminal in communication according to the moving speed of the present invention, the communication destination base station is autonomously changed to the macro cell base station. By switching between the microcell base station and the microcell base station, the frequency repetition distance and the transmission output are selected according to the moving speed, and the frequency is effectively used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a microcell / macrocell integrated cell according to the present invention.

FIG. 2 is a principle diagram of a moving speed estimation method according to the present invention.

FIG. 3 is a diagram illustrating a system configuration example of a second embodiment.

FIG. 4 is a diagram illustrating a base station configuration according to a second embodiment.

FIG. 5 is a diagram illustrating the configuration of a mobile terminal according to the second embodiment.

FIG. 6 is a diagram showing a configuration example of a base station in a conventional technique.

[Explanation of symbols]

11 micro cell 12 macro cell 13 micro cell base station 14 macro cell base station 15 mobile terminal moving at high speed 16 mobile terminal moving at low speed 21a to 21g from a micro cell base station in synchronization with a frame of a radio control channel of the macro cell base station Radio control channel number transmitted 22 Movement route of mobile terminal moving at high speed 23 Movement route of mobile terminal moving at low speed 24 Radio control channel reception level fluctuation of mobile terminal moving at high speed 25 Mobile terminal moving at low speed Of the radio control channel reception level of the mobile station 31 Paging channel for calling the mobile terminal 32 Radio control channel and communication channel between the mobile terminal moving at high speed and the macrocell base station 33 Between the mobile terminal moving at low speed and the microcell base station Radio control channel and communication channel 41 Central controller 42 Macro cell radio controller 43 for radio management of mobile terminals moving at high speed 43 Micro cell radio controller 44 for radio management of mobile terminals moving at low speed 44 Cross-connect switch 45 Public line 51 Aerial line 52 Transmission / reception Wave device 53 Up-converter 54 Modulator 55 TDMA circuit 56 Voice encoder 57 Handset 58 Down-converter 59 Demodulator 60 Level measuring device 61 Moving speed estimator 62 Synthesizer 63 Control circuit 64 Cell 65 Radio controller 66 Central controller 67 base station

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-143725 (JP, A) JP-A-62-1101135 (JP, A) JP-A-6-209278 (JP, A)

Claims (2)

(57) [Claims] 1. A cell in which a service area is covered by a plurality of micro cells of a first size, and the same service area is covered by a plurality of macro cells of a second size, which are larger than the micro cells, so as to cover the micro cells. A mobile terminal that has a configuration and uses a common wireless interface to access these two cells and moves at a first speed equal to or lower than the walking speed is installed in each microcell The mobile terminal that communicates via the mobile terminal and moves at the second speed, which is faster than the first speed, communicates with the macrocell base station installed for each macrocell via the wireless line, and the macrocell base station transmits in time division. Each microcell base station in the macrocell transmits the radio control channel in a time-division manner in synchronization with the The mobile terminal located in the macro cell is a micro cell base station capable of receiving on a predetermined frequency and slot in synchronization with a time division control signal transmitted from each micro cell base station arranged in the macro cell. Repeatedly measure the reception levels of the radio control channels of the mobile terminal, estimate the moving speed of the mobile terminal from the speed at which the received levels fluctuate, and according to the estimated moving speed, the mobile terminal determines the macrocell base station and the microcell base station. A microcell / macrocell integrated mobile communication system characterized by selectively accessing one of the two. 2. The mobile communication system according to claim 1, wherein the mobile terminal determines the moving speed at regular intervals during standby so that the mobile terminal autonomously accesses the mobile terminal when the mobile terminal makes or receives a call. If the station selects a microcell base station or a macrocell base station, and if the moving speed of the mobile terminal changes during communication, the base station in communication is automatically set between the microcell base station and the macrocell base station. A microcell / macrocell integrated mobile communication system, which is characterized in that it is selectively switched.