JPH05130018A - Mobile body communication system - Google Patents

Abstract

PURPOSE:To eliminate deficiency of channels by sequentially selecting a wide cell and a narrow cell in response to a mobile speed of a mobile body with a mobile body communication terminal equipment arranged thereto so as to suppress the frequency of hand-off. CONSTITUTION:Each cell CL consists of a cell MCL having a wide communication area and a narrow cell mCL resulting from dividing the wide cell minutely and the micro cell MCL and the micro cell m,, are sequentially selected in response to the mobile speed of a mobile body with a mobile communication terminal equipment TM arranged thereto. When the mobile body communication terminal equipment TM moves from a macro cell MCL1 to a macro cell MCL2 as shown in the arrow (a) and the micro cell mCL is used for mobile body communication, 7 to 8 times of hand-off are required, for example. When the macro cell MCL is used for the mobile body communication, only one hand-off is enough from the macro cell MCL1 to the macro cell MCL2.

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 for performing communication using a mobile communication terminal arranged in a mobile body such as an automobile.

[0002]

2. Description of the Related Art In a conventional terrestrial mobile communication system, usually, a plurality of base stations are arranged and there are service areas which are in charge of each of them. The service area covered by each base station is called a normal cell, and therefore each cell has one base station.

FIG. 13 shows the relationship between the cell and the base station in such a mobile communication system.

In FIG. 13, in the mobile communication system, each cell CL (for example, cells CL1, CL2, CL) is arranged in order to minimize a gap between service areas.
3) is usually arranged so that it overlaps little by little. Also,
Since the mobile communication terminal TM is arranged in a mobile body such as an automobile, when the mobile body is moving, the mobile communication terminal TM may move away from one base station BS even during a call. There is. In the example of FIG. 13, when the mobile communication terminal TM moves from the cell CL1 in the direction indicated by the arrow a in the figure, the mobile communication terminal TM moves away from the base station BS1 of the cell CL1. Therefore, in such a case, it is necessary to switch to another base station BS that can communicate better. In the example of FIG. 13, it is necessary to switch to the base station BS3.

Thus, from one cell CL to another cell C
L (for example, cell CL1 to cell CL3 in FIG. 16)
Moving to) is usually called a handoff.

[0006]

By the way, usually, the frequency band or the number of channels that can be used in one communication system is limited. In addition, for example, adjacent cells do not use the same channel. As a result, the number of channels that can be used in one cell is further reduced.

Here, the number of mobile communication terminals that can be used in one cell is determined by the usage rate and the number of channels per mobile communication terminal.

Therefore, for example, when the number of users (users) of the mobile communication terminal increases and the number of the mobile communication terminals increases, the state in which all channels are used increases, so that when communication is desired. May not be able to communicate with.

To avoid this, for example, there is a method of miniaturizing the cell. That is, this is 1 because the number of channels per cell is determined as described above.
The service area of one base station is reduced to reduce the number of mobile communication terminals per cell.
In particular, in the case of car telephones, the size of cells is becoming smaller in urban areas, and the size of one cell is decreasing from a radius of 500 km to about 1 km. As described above, it is expected that the miniaturization of the cell will be further advanced in the future as handy type telephones become popular.

As described above, the miniaturization of the cell has the merit that the transmission output of each mobile communication terminal can be small, but when the mobile communication terminal moves, the handoff frequently occurs because the cell is small. become. If handoffs occur frequently in this way, there arises a problem that complicated processing of the base station (or control station) increases.

That is, in the conventional mobile communication system, for example, if the cell is made larger, the number of handoffs can be reduced, but as described above, the number of channels is insufficient,
On the contrary, for example, if the cell size is reduced, the channel shortage can be resolved, but the number of handoffs increases.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and provides a mobile communication system capable of suppressing the frequency of handoff to a low level and solving the shortage of channels. It is intended to be provided.

[0013]

The mobile communication system of the present invention is proposed to achieve the above-mentioned object, and a plurality of base stations each provided with a cell and one or more mobile communication systems are provided. Comprising a terminal, the mobile communication terminal existing in the cell is a mobile communication system that communicates via the base station, each cell of the plurality of base stations, a wide communication area cell, It is configured by a narrow cell of a communication area that subdivides the wide cell, and the wide cell and the narrow cell are sequentially selected according to the moving speed of the mobile body in which the mobile communication terminal is arranged. It is a thing.

That is, the mobile communication system of the present invention is used in mobile communication such as a car telephone.
Base stations are arranged so that cells with large communication areas (macro cells) and narrow cells (micro cells) exist in the same area at the same time, and the moving speed of mobiles (moving speed of mobile communication terminals)
In this system, the macro cell and the micro cell are selectively used according to the above, so that the handoff can be made small and the channel shortage can be eliminated at the same time.

Here, the macro cell and the micro cell can be mixed by using different channels (frequency).

Further, in the above macro cell, it is required for both the base station and the mobile communication terminal to increase the transmission output, but in the mobile communication terminal, it is possible to save by controlling the output power according to the size of the cell. It will also be possible to achieve electricity conversion.

[0017]

According to the mobile communication system of the present invention, each cell of a plurality of base stations is composed of a cell having a wide communication area and a cell having a narrow communication area for subdividing the wide cell. A wide cell and a narrow cell are sequentially selected according to the moving speed. When the moving object is moving at a high speed, the wide cell is selected and it is not moving or is moving at a constant speed. By selecting a narrow cell at times, it is possible to reduce handoff and eliminate channel shortage at the same time.

[0018]

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

The mobile communication system of this embodiment comprises, for example, a plurality of base stations each provided with a cell and one or more mobile communication terminals, and mobile communication existing in any one of the above cells. The terminal is a mobile communication system that communicates via the base station (base station of the cell in which the mobile communication terminal exists), and as shown in FIG.
L is composed of a cell having a wide communication area (hereinafter referred to as macro cell M _CL ) and a cell having a narrow communication area (hereinafter referred to as micro cell m _CL ) that subdivides the wide cell, and the mobile communication terminal TM Depending on the moving speed of the moving body where
The macro cell M _CL and the micro cell m _CL are sequentially selected.

Here, as will be described later, whether to use the macro cell M _CL or the micro cell m _CL according to the moving speed of the moving body is determined by, for example, the mobile communication terminal TM.
Entrusted to. That is, whether or not the mobile communication terminal TM is moving at high speed cannot be known to the base station (a control station or the like described later), and thus the above determination is left to the mobile communication terminal TM.

Although the macro cell M _CL is the same as the cell CL shown in FIG. 13 in the example of FIG. 1, a plurality of macro cells M _CL may be arranged in the cell _CL. Good.

Further, in this embodiment, the macro cell M _{CL is}
Is about 5 km to 10 km, and the microcell m _CL is about 0.5 km to 1 km. Further, the macro cell M _CL includes a plurality of micro cells m _CL . The sizes of the macro cells M _CL and the micro cells m _CL are considered to be appropriate when the mobile communication system is, for example, a mobile phone, and therefore other types of systems are used instead of the mobile phone. It is also possible to change it according to the conditions such as the number of mobile communication terminals or the area.

In FIG. 1, an arrow a is drawn from the macro cell M _CL1 to the macro cell M _CL2 , but if the mobile communication terminal TM moves as shown by this arrow a, For example, if the above-mentioned micro cell (cell miniaturized in accordance with the increase in the number of mobile communication terminals) m _CL is used for mobile communication, for example, 7 to 8 handoffs are required. On the other hand, if the macro cell M _CL is used for mobile communication, the handoff is required only once from the macro cell M _CL1 to the macro cell M _CL2 .

[0024] Here, in the mobile communication system of the present embodiment, the line control is performed by the macrocell M _CL units, the system configuration corresponding to one macrocell M _CL is
This is done as shown in FIG.

In FIG. 2, the system configuration for the macro cell M _CL is one control station B _CT , one macro cell M _CL base station BS _M, and a plurality (n) of micro cells m _CL1 , m _CL2 , ..., m _CLn base stations bs _m1 , b
s _m2, ···, composed of the bs _mn.

The control station B _CT includes base stations BS _M and bs _m1 , b of the macro cell M _CL and the micro cell m _CL.
At the same time as controlling the wireless lines used by s _m2 , ..., Bs _mn , the communication path between the switching center (not shown) and each base station is controlled.

Further, between the control station B _CT and the switching center, control relating to the handoff between the macro cells M _CL is performed in addition to the communication path.

Further, the base stations BS _M and bs _m1 , bs _m2 , ..., B of the macro cell M _CL and the micro cell m _CL are described.
s _mn connects to the mobile communication terminal TM on the designated channel.

Between each of these base stations and the control station B _CT , control of the wireless line (calling from the mobile communication terminal or calling of the mobile communication terminal, and handoff control between the microcells m _CL ) is performed. Be seen.

FIG. 3 shows the base station B of the macro cell M _CL.
The block diagram of S _M is shown.

The configuration of FIG. 3 has the above-mentioned mobile communication terminal T.
L + 1 of the call transceiver device 10 for connecting the communication line to the M, L + 2, ···, each transmitter 11 for each channel of the _{N L1, 11 L2, ···,} 11 N and the receiver 12 _L1,
12 _L2, · · ·, 12 and _N, the antenna sharing device 2 for sending a received signal from or the antenna 4 transmits the transmission signal from the antenna 4 from each transmitter to each receiver, the base station BS _M And a base station control circuit 1 that controls the control of the mobile communication terminal TM when the base station BS _M of the macro cell M _CL undertakes a call to the mobile communication terminal TM. It also has 20 transmitters 23. However, this transmitter 23 is
It is not necessary if the _CL base station BS _M has a control transmitter.

That is, in FIG. 4, the base station BS
_M is a plurality of frequencies (for example, L + 1, L + 2, ...
, N channels), and therefore, the transmitters 11 _L1 , 11 _L2 , ..., 11 _N and the receivers 12 _L1 , 12 of the respective channels of the call transmitter / receiver 10 are transmitted. _L2, · · ·, 12 _N is connected to the antenna 4 through the antenna sharing device 2.

Here, only the channel L + 1 will be described. A received signal that has passed through the antenna 4 and the antenna sharing apparatus 2 is transmitted to the channel L + via the receiver input signal line.
1 is input to the receiver 12 _L1 . The signal demodulated by the receiver 12 _L1 is sent to the base station control circuit 1 via the receiver output signal line. The signal transmitted through the base station control circuit 1 is sent from the terminal 5 to the wireless control station B _CT , and is further connected to the exchange.

On the other hand, from the switching center to the wireless control station B _CT
The transmission signal sent to the terminal 5 via the base station control circuit 1 is input to the transmitter 11 _L1 for channel L + 1, for example, through the transmitter input signal line. The transmission signal modulated by the transmitter 11 _L1 is input to the antenna sharing apparatus 2 via the transmitter output signal, and the antenna 4
Sent from.

The other transmitters and receivers of the call transmitting / receiving apparatus 10 are the same as those described above, and a description thereof will be omitted.

The base station control circuit 1 controls each constituent element of the base station BS _M.

FIG. 4 shows each base station bs of the microcell m _{CL.
The structure of m1} , bs _m2 , ..., Bs _mn is shown.

The configuration of FIG. 4 has the above-mentioned mobile communication terminal T.
The transmitters / receivers 71 of the channels 1, 2, ..., N-P of the telephone transceiver 70 for connecting a telephone line to M
₁ , 71 ₂ , ..., 71 _NP and receivers 72 ₁ , 72
₂ , ..., 72 _NP , an antenna sharing device 62 for transmitting a transmission signal from each transmitter from the antenna 64 or sending a reception signal from the antenna 64 to each receiver, and the base station bs _m It has a base station control circuit 61 that controls the control, and a receiver 84 of a control receiving device 80 that receives a control channel. Further, the base station bs of the macro cell M _CL is provided.
_{When m} does not have the transmitter 23, the base station bs _m of the microcell m _CL has the transmitter 83 for control.

That is, each microcell m _CL of this embodiment
In order for the control station B _CT to know which microcell m _{CL the} mobile communication terminal TM is in, the base station bs _m of
The receiver 84 is provided for receiving a control signal (control channel signal) from the mobile communication terminal TM. Specifically, the control station B _CT selects which base station bs _m to use based on the signal strength received by the receiver 84 of each base station bs _m . The control signal sent to the mobile communication terminal TM does not need to be held by the base station bs _m of each micro cell m _CL , but may be held by the base station bs _m of the macro cell M _CL .

In FIG. 4, the base station bs _m can transmit and receive a plurality of frequencies (for example, the above 1, 2, ..., N-P channels).
Transmitter 71 for each channel of the call transceiver 70
₁ , 71 ₂ , ..., 71 _NP and receivers 72 ₁ , 7
2 _2, · · ·, 72 _NP is connected to the antenna 64 through the antenna sharing device 62.

Explaining only the channel (1CH), for example, the received signal that has passed through the antenna 64 and the antenna sharing device 62 is input to the receiver 72 ₁ for the channel 1 via the receiver input signal line. The receiver 72 ₁
The signal demodulated in (4) is sent to the base station control circuit 61 via the receiver output signal line. The base station control circuit 61
The signal via the terminal 65 is transmitted from the terminal 65 to the wireless control station B _CT.
To the switching center.

On the other hand, from the exchange to the radio control station B _CT
The transmission signal sent to the terminal 65 via the base station control circuit 61 is further input to the transmitter 71 ₁ for channel 1, for example, through the transmitter input signal line. The transmission signal modulated by the transmitter 71 ₁ is input to the antenna sharing device 62 via the transmitter output signal, and is output from the antenna 64.

The other transmitters and receivers of the call transmitting / receiving apparatus 70 are the same as those described above, and the description thereof will be omitted.

The base station control circuit 61 controls each constituent element of the base station bs _m .

[0045] Figure 5 is a specific configuration diagram of the control station B _CT, the control station B _CT is comprised of a channel device 100 and the radio network controller 110.

The communication path device 100 serves as an interface between the exchange and each base station, and operates according to a command from the radio network controller 110.

The radio network controller 110 receives a call from the mobile communication terminal TM received from each base station, a handoff request between the microcells m _CL , an incoming call request from the switching center, and a handoff between the macrocells M _CL. On the basis of the request, the use channel is assigned to each base station.

Although not shown in FIG. 5, the exchange is a control station B _CT and a public line, and a control station B _CT and a control station B _CT.
It is the interface with.

By the way, when the service areas of the macro cell M _CL and the micro cell m _CL are overlapped as in the embodiment of the present invention, the same channel cannot be used in both cells M _CL and m _CL. In such a case, it is necessary to use different channels for the macro cell M _CL and the micro cell m _CL .

FIG. 6 shows the macro cell M in this embodiment.
Channel allocation for _CL and microcell m _CL is shown.

That is, in the present embodiment, usable channels are, for example, a plurality (N) of channels (N in the figure).
Channels), for example, L channels (L channels in the figure) of them are dedicated to the microcell m _CL , and P channels of them (P channels in the figure) are dedicated to the macrocell M _CL , and the rest are Common to micro cell m _CL and macro cell M _CL (NPL in the figure)
Channel).

Here, the shared channel (N-
If the P-L channel) is not prepared, the following can occur. That is, for example, when all the channels for the microcell m _CL (the L channel) are used,
Even if the channel for the macro cell M _CL (the P channel) is vacant, the micro cell m _CL
Will not be able to use the base station bs _m .
In this case, the macro cell M _CL is used,
This will reduce the use efficiency of the channel.

On the contrary, when the channel (L channel) for the microcell m _CL is vacant but the channel (P channel) for the macrocell M _CL is occupied, the macrocell M _CL is Since the base station BS _M cannot be used and the microcell m _CL is used, the mobile communication terminal TM moving at a high speed causes frequent handoff.

Therefore, the shared channel (N-
Micro-cell m
It becomes possible to selectively use the channels of the _CL and the macro cell M _CL (L channel and P channel) depending on the usage status.

On the other hand, the shared channel (NP-
If there is no dedicated channel only for the L channel), the following problems may occur.

That is, let us consider a case where, for example, all the N channels are used for the micro cell m _CL , and there is a mobile communication terminal TM which wants to use the macro cell M _CL .

Here, in the macro cell M _CL , a plurality of micro cells m _CL use the same channel. In order for this channel to be released for the macrocell M _CL , all microcell m _CL base stations using this channel must release this channel, but to the extent that all channels are used. If it is crowded, it cannot be expected to be released for the macro cell M _CL .

In this case, it suffices to be able to forcibly move the mobile communication terminal TM from this channel, but for that purpose, another unused channel is required.

On the contrary, in the situation where most of the N channels are used for the macro cell M _CL , the use efficiency of the channels is lowered, and when the number of mobile communication terminals TM requesting line connection increases rapidly. The number of mobile communication terminals TM that cannot use the line will increase rapidly. In order to solve this situation, the mobile communication terminal TM using the macro cell M _CL releases the channel to release the micro cell m _CL.
Have to wait to be assigned to. However, since it is considered that the mobile communication terminal TM using the macro cell M _CL does not release the channel at one time,
It can only be resolved gradually.

Therefore, it is important to comprehensively judge the above-mentioned matters and allocate the dedicated channel and the shared channel.

In FIG. 6, the channels for each cell and the shared channel are arranged consecutively, but they are not necessarily arranged consecutively and may be discontinuous.

Channel control in the control station B _CT will be described with reference to FIG. However, the channel control in the control station B _CT described below is a specific example.

The control station B _CT manages the allocation of channels used by the macro cell M _CL and the micro cell m _CL, and has a table as shown in FIG.

In FIG. 7, the macro cell M _CL and the micro cells m _CL1 , m _CL2 , ..., _{M CLn} included therein are _taken as an example. Further, in FIG. 7, for convenience of explanation, a channel dedicated to the macro cell M _CL (P channel) and a channel dedicated to the micro cell m _CL (L channel),
The shared channel (N-P-L channel) is continuously arranged. As shown in FIG. 6 described above, the channels dedicated to the microcell m _CL are from 1 channel to L channel, the shared channels are from L + 1 channel to N−P channel, and the macro cell M _{CL is used.}
The dedicated channels are N-P + 1 channels to N channels.

That is, the control station B _CT uses the macro cell M _CL for channel allocation of the macro cell M _CL.
Table TB for dedicated channel (P channel)
₃ and table TB ₂ for shared channel. Also, the micro cell m is used for the micro cell m _CL .
Table t for _CL dedicated channel (L channel)
b ₁₁ , tb ₁₂ , ..., Tb _1n and the shared channel (N
-P-L channel) tables tb ₂₁ , tb ₂₂ ,.
..Has tb _2n Each of the tapes for the microcell m _CL tb ₁₁ , tb ₁₂ , ..., Tb _1n and tb ₂₁ ,
tb _22, ···, tb _2n, each microcell of each of the aforementioned FIG. _{2 m CL1, m CL2, ···} , correspond to the m _CLn.

FIG. 8 shows a channel allocation procedure when the mobile communication terminal TM is called and when the mobile communication terminal TM is called by the mobile communication terminal TM and when the mobile communication terminal TM is handed off in the present embodiment. Note that FIG. 8 exemplifies a case where the mobile communication terminal TM exists in, for example, the micro cell m _CL1 in the macro cell M _CL . Since the same applies to the other macro cells M _CL and the micro cells m _{CL2 to} m _CLn in the other macro cells M _CL , the description thereof will be omitted.

In the flowchart of FIG. 8, when the process is started in step S1, the cell requested by the mobile communication terminal TM in step S2 is the macro cell M _CL or the micro cell m _CL1 . Determine if there is.

If it is determined in step S2 that the macro cell M _CL is requested (Yes), the table TB ₃ shown in FIG. 7 of the control station B _CT is checked, and the macro cell M _CL is searched in step S3. Determine whether the _CL dedicated channel (P channel) can be used.

When it is determined in step S3 that the macro cell M _CL dedicated channel can be used (Yes), P of the macro cell M _CL dedicated channel in FIG. 6 is used.
Channel N, for example, is assigned from channel N-P + 1 of the channels, and the process proceeds to step S5 and ends. If it is determined in step S3 that the macro cell M _CL dedicated channel is full and cannot be used (No), the table TB _{2 in} FIG. 7 is examined, and in step S6, the shared channel (NPL channel) is determined. Determine if it can be used.

If it is determined in step S6 that the shared channel is not full and can be used (No), the process proceeds to step S7, and the shared channel (channel L + 1 to channel N-P) of FIG. 6 is selected. A channel is assigned, and then the process ends in step S5. If it is determined in step S6 that the shared channel is also full and cannot be used (Yes), the process proceeds to step S9, and Busy is set in the mobile communication terminal TM in step S9.
Alternatively, the exchange is notified, and the process ends in step S5.

Further, when the micro cell m _CL1 is requested in step S2 (No), step S2 is performed.
11, the table tb of FIG. 7 is set in this step S11.
₁₁ is checked and the above-mentioned microcell m _CL1 dedicated channel (L
Channel) is available.

If it is determined in this step S11 that the dedicated channel for the microcell m _CL1 is not full (No), the process proceeds to step S12, in which the channel from channel 1 to channel L in FIG. 6 is selected. Channel is allocated, and the process ends in step S5. Further, in a case where a dedicated channel in step S11 is determined to not be used in full (Yes), the flow proceeds to step S14, it examines the table tb ₂₁ of FIG. 7 in this step S, determines whether the shared channel is available ..

When it is determined in step S14 that the shared channel is not full and can be used (No), the process proceeds to step S15, and the shared channels, that is, the channels L + 1 to N-P in FIG. 6 are shared channels.
After allocating channels from, the process ends in step S5. If it is determined in step S14 that the shared channel is also full and cannot be used (Yes), the process proceeds to step S17, Busy is notified, and then the process ends in step S5.

FIG. 9 shows an example of the procedure for releasing the channel after the communication is completed. In FIG. 9 as well, for example, the micro cell m in the macro cell M _CL is used.
An example is given in which the mobile communication terminal TM is present in _CL1 . Since the same applies to the other macro cells M _CL and the micro cells m _{CL2 to} m _CLn in the other macro cells M _CL , the description thereof will be omitted.

In the flowchart of FIG. 9, when the process is started in step S31, it is first checked in step S32 whether the base station BS _M of the macro cell M _CL is used, and it is determined that the base station BS _M is used in step S32. If YES (Yes), the macro cell M _CL is determined in step S33.
Find out if you were using a dedicated channel or a shared channel. That is, in this step S33, it is checked whether or not the table TB _{3 of} FIG. 7 has been used.

[0076] If it is determined that uses the dedicated channel in step S33 (Yes), the use of the table TB ₃ in FIG channel in step S34 (or the usable channels of the channel N-P +. 1 to channel N) Erase (release channel). In the case it is judged that uses shared channels (No), step S33, the process proceeds to step S36, any of this step S36 using the table TB ₂ of Fig. 7 channel (channel L + 1-channel N-P Delete the used channel) (release the channel).

If it is determined No in step S32, that is, it is determined that the base station bs ₁ of the microcell m _CL1 is being used (No), the process proceeds to step S38. Cell m
_Find out if you were using a dedicated _CL1 channel or a shared channel. That is, in this step S38, it is checked whether or not the table tb _{11 of} FIG. 7 has been used.

When it is determined in step S38 that the dedicated channel is used (Yes), step S38
39, and in step S39, the table tb in FIG.
_The channel used (channel used among channel 1 to channel L) is deleted from 11 (release of channel). If it is determined in step S39 that the shared channel is used (No), step S4
1, and in step S41, the table tb ₂₁ in FIG.
To use channels (channel L + 1 to channel N
-Delete (use channel of P) (release channel).

FIG. 10 shows an example of channel control at the time of transmission from the mobile communication terminal TM. It should be noted that this FIG.
0, the case where the transmitter for channel control is in the base station BT _M of the macro cell M _CL is described as an example.

That is, in FIG. 10, first, the mobile communication terminal TM uses the control channel as shown by an arrow PP ₁ in the figure to make a call origination request. At this time, the mobile communication terminal TM attaches information as to which of the macro cell M _CL and the micro cell m _CL is to be used, to the call origination request. Receiving this, for example, the base station bt _m of the micro cell m _CL sends a call origination request as indicated by an arrow PP ₂ in the figure, and the control station B
Information of reception level is added to this transmission request while being transferred to _CT . The call origination request issued by the mobile communication terminal TM is not always received by one base station.

The control station B _CT determines the cell and channel to be used based on the transmission request received from the plurality of base stations, the reception level attached to the transmission request, and the information on which cell to use. To do. The control station B _CT is indicated by an arrow PP _{3 in} the figure.
As shown in, the cell used and the channel designation information are transferred to the base station BT _M of the macro cell M _CL . The control station B _CT is also connected to the exchange B _TE .

The base station BT _M of the macro cell M _CL uses the control transmitting device 20 shown in FIG. 3 described above to indicate the transferred designation information as shown by the arrow PP ₄ in the figure to the mobile communication terminal TM. Tell to.

Therefore, the mobile communication terminal TM concerned is
The call line is connected using the channel designated by this designation information.

FIG. 11 shows a mobile communication terminal TM when receiving a call.
Shows the procedure for calling and connecting the call line.

In FIG. 11, when the exchange B _TE informs the control station B _CT of an incoming call, this control station B _CT is called.
_As shown by arrows AP ₁ and AP ₂ in the figure, the _CT calls the mobile communication terminal TM by using the control transmission device 20 of FIG. 3 of the base station bs _m of the macro cell M _CL .

As a result, the mobile communication terminal TM, which has learned that it is being called, makes a line connection using the control channel. The procedure is as shown by arrow PP _{3 in} the figure.
As shown in ~PP _4, it is the same as that in the above outgoing.

Here, the macro cell M _CL and the micro cell m _CL
It is left to the mobile communication terminal TM to decide which of _CL is used at least at the time of making a call and when making a call. That is, whether or not the mobile communication terminal TM is moving at high speed is left to the mobile communication terminal TM because the control station B _CT and the base station do not know.

FIG. 12 shows the procedure for handoff. In addition, in FIG. 12, the macro cell M _CL
However, the same operation is performed when the microcell m _CL is used.

That is, in FIG. 12, the base station BS _M of the macro cell M _CL constantly monitors the reception level of the channel being used, and the base station BS _{Ma which} has learned that the reception level has decreased is, for example, the base station BS _Ma. , As indicated by arrows HP ₁ and HP ₂ in the figure, notify the switching _center B _TE through the control station B _CTa .

The exchange B _TE has a device for controlling handoff, and the exchange B _TE has a cell (macro cell M _CLa ) adjacent to the cell (macro cell M _CLa ) with which the exchange B _TE has contacted.
_CLb ) to the base station BS _Mb for the arrows HP ₃ and HP in the figure.
_As shown in ₄ , an instruction is given to report the reception level of the signal from the mobile communication terminal TM. However, the control station B _CTb does not always give one instruction.

Receiving this, the base station B of the macro cell M _CLb
As indicated by arrows HP ₅ and HP ₆ in the figure, S _Mb reports the reception level of the designated channel and the information of the channel allocation result to the exchange B _TE .

The switching center B _TE selects the optimum cell based on the report from the base station BS _Mb, and the arrows HP ₇ and H in the figure
As shown in P ₈ , the macro cell M is transmitted via the control station B _{CTb.
Instructing} the base station BS _{Mb of CLb} to connect the communication line with the mobile communication terminal TM, the arrows HP ₉ and H in FIG.
As indicated by P ₁₀ and HP ₁₁ , the mobile communication terminal TM is instructed to switch the channel via the base station BS _Ma (and the control station B _CTa ) which has been used until then.

After the mobile communication terminal TM switches the channel, the base station BS _Ma releases the used channel. This completes the handoff procedure.

From the above, according to the mobile communication system of the present embodiment, a system in which large and small macro cells M _CL and micro cells m _CL are combined is constructed, and it is determined whether the system is moving at high speed or moving at low speed. By selectively using the cell to be used for communication among the macro cell M _CL and the micro cell m _CL , it is possible to suppress the frequency of handoffs and solve the channel shortage. In addition, by controlling the transmission output according to the size of the cell, it is possible to save power when using the microcell m _CL .

[0095]

As described above, in the mobile communication system of the present invention, each cell of a plurality of base stations is composed of a cell having a wide communication area and a cell having a narrow communication area for subdividing a wide cell. By configuring to sequentially select a wide cell and a narrow cell in accordance with the moving speed of the mobile body in which the mobile communication terminal is arranged, the frequency of handoff can be suppressed to a low level, and the channel It is possible to resolve shortages.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a macro cell and a micro cell in a mobile communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a mobile communication system according to an embodiment.

FIG. 3 is a block circuit diagram showing the configuration of the base station of the macro cell of the embodiment.

FIG. 4 is a block circuit diagram showing the configuration of the base station of the microcell of the embodiment.

FIG. 5 is a block circuit diagram showing a configuration of a control station of the embodiment.

FIG. 6 is a diagram for explaining channel allocation to macro cells and micro cells according to an embodiment.

FIG. 7 is a diagram for explaining a channel control table of a control station according to the embodiment.

FIG. 8 is a flowchart showing a procedure of channel allocation of the control station of the embodiment.

FIG. 9 is a flowchart showing a procedure of channel release of the control station of the embodiment.

FIG. 10 is a diagram for explaining a procedure at the time of making a call from the mobile communication terminal of the embodiment.

FIG. 11 is a diagram for explaining a procedure at the time of receiving an incoming call from the exchange according to the embodiment.

FIG. 12 is a diagram for explaining a procedure of handoff between macro cells according to the embodiment.

FIG. 13 is a diagram for explaining a conventional cell.

[Explanation of symbols]

TM: Mobile communication terminal M _CL1 , M _CL2 , M _CL3: Macro cell m _CL: Micro cell B _CT: Control station BS _M ... Macro cell base station bs _{m1 to} bs _m3 ... Micro cell base station

Claims (1)

[Claims] 1. A plurality of base stations each provided with a cell,
In a mobile communication system comprising one or more mobile communication terminals, the mobile communication terminal existing in the cell communicates via the base station. It is characterized by comprising a wide cell and a cell having a narrow communication area for subdividing the wide cell, and sequentially selecting the wide cell and the narrow cell according to the moving speed of the mobile communication terminal. Mobile communication system.