JP2002185997A - Mobile communication system - Google Patents

Abstract

(57) [Problem] To efficiently relay communication performed by a communication terminal accommodated in a fixed base station in a congested area to another fixed base station even when different mobile communication systems coexist. To do. SOLUTION: A control device 34 gives priority to a fixed base station 21 or a fixed base station 25 using the same communication system as the communication system used by the fixed base station 11 as an alternative base station for the congested fixed base station 11. To select. The mobile relay station 40
The communication in the fixed base station 11 is relayed to the alternative base station selected by the control device 34.

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 using a cellular system, and more particularly to a mobile communication system in which a mobile relay station is dispatched to a congested coverage area to perform wireless communication.

[0002]

2. Description of the Related Art In a mobile communication system, a cellular system in which a service area of one radio base station is set to several kilometers and a large number of radio base stations are arranged is widely used. In this cellular system, a plurality of radio base stations spatially separated from each other use the same radio channel, so that a finite radio channel can be effectively used.

In the above-mentioned cellular system, in order to provide communication services smoothly and efficiently, a relatively large number of radio base stations are arranged in an urban area where many users are present. Optimized to build a network (mobile communication network). Thus, in the cellular system, a communication service is provided while securing a sufficient number of channels in each area.

[0004] However, when a sudden incident / accident or disaster occurs in a certain area, or when a planned event is performed, mobile stations concentrate in the area, congestion occurs, and the traffic in the area increases. May temporarily increase. In an area where such congestion occurs (a congestion area), a large number of mobile stations simultaneously make outgoing calls, resulting in a shortage of the number of channels of the radio base station.
Phenomena occur, and communication cannot be performed.

[0005] As a technique for coping with the above-mentioned temporary increase in the amount of communication, for example, a "mobile communication system" is disclosed in JP-A-10-066138. According to JP-A-10-066138, a mobile base station (hereinafter, simply referred to as a “mobile base station”) is dispatched to a congested area, and a wireless line that does not mix with a fixed base station is connected to the mobile base station and the fixed base station. Set between communication terminals that cannot be accommodated in the station. The mobile base station establishes a wireless line with an existing exchange. The exchange is provided with an antenna and a radio transceiver for establishing a radio line equivalent to a wired communication line between the fixed base station and the exchange between the mobile base station. Thereby, the exchange can handle the communication via the fixed base station and the communication via the mobile base station equally.

[0006]

However, when the distance from the mobile base station to the nearest exchange is long, or when the radio line allocated to the exchange is insufficient,
There is a problem that a wireless channel cannot be established between the mobile base station and the exchange.

[0007] The present invention has been made in view of such a point, and even when different mobile communication systems coexist, communication performed by a communication terminal accommodated in a fixed base station in a congested area is different. It is an object of the present invention to provide a mobile communication method and a mobile communication system capable of efficiently relaying to a fixed base station.

[0008]

A mobile communication system according to the present invention includes a plurality of fixed base stations for performing wireless communication with a communication terminal existing in a coverage area of the mobile station, and at least one fixed base station included in the plurality of fixed base stations. A control device that selects one fixed base station as an alternative base station, and a movable mobile relay station that relays communication in a target fixed base station included in the plurality of fixed base stations to the alternative base station, The control device adopts a configuration in which a fixed base station using the same communication system as the communication system used by the target fixed base station is preferentially selected.

According to this configuration, when communication systems having different communication systems coexist, as an alternative base station,
By prioritizing and selecting a fixed base station using the same communication system as the target fixed base station, the communication performed by the communication terminal accommodated in the target fixed base station can be replaced without changing the communication method It can be relayed to a base station. This can reduce the processing load when relaying communication.

In the mobile communication system according to the present invention, in the mobile communication system described above, the target fixed base station performs wireless communication with a multi-mode terminal existing in its own coverage area, and the multi-mode terminal communicates with the target fixed base station. In this configuration, the mode for performing communication using the same communication method as that of the alternative base station is changed to the mode for performing communication using the same communication method as the alternative base station to perform wireless communication.

According to this configuration, even when a fixed base station using a communication system different from the communication system used by the target fixed base station is selected as the substitute base station, the call is set to the calling multimode terminal. The current mode is changed to a mode for performing the same communication method as the alternative base station, and communication in the changed mode is relayed. Therefore, the mobile relay station does not need to convert the communication method even when relaying between systems using different communication methods, and can reduce the processing load at the time of relaying.

In the mobile communication system according to the present invention, in the mobile communication system described above, the target fixed base station performs wireless communication with a multi-mode terminal and a single-mode terminal existing in its own coverage area, and the control device includes: When selecting a station, a configuration is adopted in which a fixed base station using the same communication scheme as the communication scheme used by the target fixed base station is assigned to the single mode terminal with priority over the multimode terminal. .

According to this configuration, when a multi-mode terminal and a single mode terminal are mixedly accommodated in the target base station, the fixed base station using the same communication system as the target fixed base station is configured as a single fixed base station. Assigned to mode terminals with priority. Thereby, the call loss of the single mode terminal can be reduced.

In the mobile communication system according to the present invention, in the mobile communication system described above, the target fixed base station performs wireless communication with a software defined radio existing in its own coverage area,
The software radio device adopts a configuration in which software for realizing communication according to a communication method used by an alternative base station is obtained and wireless communication is performed.

According to this configuration, when a fixed base station using a communication system different from the communication system used by the target fixed base station is selected as the substitute base station, the software radio that has made the call will not be able to use the substitute base station. The software that realizes communication in the communication method to be used is downloaded, and communication is performed using the downloaded software. Therefore, the mobile relay station does not need to convert the communication scheme even when relaying between systems having different communication schemes, and can reduce the processing load when relaying between systems.

In the mobile communication system according to the present invention, in the mobile communication system described above, the mobile relay station substitutes the communication of the communication terminal originating in the coverage area of the target fixed base station in which all of the allocated channels are used as an alternative base station. Adopt a configuration to relay to the station.

According to this configuration, when communication systems having different communication systems coexist, as an alternative base station,
By preferentially selecting a fixed base station using the same communication system as the communication system used by the congested fixed base station, the communication terminal accommodated in the congested fixed base station performs the operation. The communication can be relayed to the alternative base station without changing the communication system. As a result, it is possible to reduce a processing load when relaying communication of a communication terminal existing in a congested area.

A mobile relay station according to the present invention is a mobile relay station that relays communication at a target fixed base station included in a plurality of fixed base stations to an alternative base station.
Means for acquiring identification information for identifying an alternative base station selected from a control device that preferentially selects a fixed base station using the same communication system as the communication system used by the target fixed base station; and A configuration is provided that includes: a moving unit that moves to a position where it can communicate with a communication terminal existing in the coverage area;

According to this configuration, it is possible to reduce the conversion of the communication system when relaying the communication at the target fixed base station to the alternative base station. This can reduce the processing load on the mobile relay station when relaying communication.

In the mobile communication method according to the present invention, in the mobile communication method in which a plurality of fixed base stations connected to a network perform radio communication with a communication terminal existing in the coverage area of the mobile station, the plurality of fixed base stations may be used as the alternative base stations. Preferentially selecting a fixed base station using the same communication scheme as the communication scheme used by the target fixed base station included in the fixed base station, and relaying communication in the target fixed base station to the alternative base station And so on.

According to this method, when communication systems having different communication systems coexist, as an alternative base station,
By prioritizing and selecting a fixed base station using the same communication system as the target fixed base station, the communication performed by the communication terminal accommodated in the target fixed base station can be replaced without changing the communication method It can be relayed to a base station. This can reduce the processing load when relaying communication.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention is that when different communication systems coexist, an alternative base station is selected by considering whether or not a relay source system and a relay destination system match. The purpose is to efficiently relay communication performed by a communication terminal in a congested area to an alternative base station.

That is, in the present invention, a fixed base station accommodated in the same communication system as a communication system accommodating a fixed base station in a congested area is preferentially selected as an alternative base station. The processing load when performing various conversion processes involved in communication between systems is reduced.

Further, in the present invention, when a fixed base station accommodated in a system different from the system in the congested area is selected as an alternative base station, the mode of the multi-mode terminal that has made a call is accommodated by the alternative base station. Change to the mode that is appropriate for the current system and communicate in the mode after the change.

Further, according to the present invention, when a fixed base station accommodated in a system different from the system in the congested area is selected as an alternative base station, the software radio that makes the call is accommodated in the alternative base station. The software that realizes communication in the system being downloaded is downloaded from the mobile relay station, and communication is performed using the downloaded software.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. (Embodiment 1) FIG. 1 shows a partial configuration of a mobile communication system including a mobile relay station 40.
The mobile relay station 40 is mounted on a mobile body such as a helicopter or an automobile, and is dispatched to a congestion area under the control of the control device 34. The mobile relay station 40 relays the communication performed by the communication terminal calling in the congested area to the alternative base station selected by the control device 34. The alternative base station provides a radio channel in place of the fixed base station where congestion has occurred. The mobile communication system illustrated in FIG. 1 includes a communication system that performs wireless communication using an 800 MHz band carrier including an exchange 31 and an exchange 33, and a 1.5G
It is dispatched to an area where a communication system that performs wireless communication using a carrier in the Hz band coexists.

Each of the fixed base station (BS) 11 and the fixed base station (BS) 21 is connected to the exchange 31 by wire, and communicates with a communication terminal existing in its own coverage area by 800.
Wireless communication is performed using a carrier in the MHz band. The base station (BS) 23 performs wireless communication with a communication terminal existing within its own coverage area 24 using a carrier in the 1.5 GHz band. The fixed base station (BS) 25 performs wireless communication with a communication terminal existing in its own coverage area 26 using an 800 MHz band carrier. The fixed base station 21, the fixed base station 23, and the fixed base station 25 have a function as an alternative base station in addition to a function as a normal base station. The coverage area 12 is a coverage area of the fixed base station 11 and accommodates a large number of communication terminals, causing congestion. The cover area 22 is a cover area of the fixed base station 21.

The communication terminals 13 to 18 perform radio communication with the fixed base station 11 using a carrier in the 800 MHz band. When there is no free channel in the fixed base station, the mobile relay station 40 and the 800 MHz band or 1. Wireless communication is performed using a carrier in the 5 GHz band.

The exchange 31 is connected by wire to a plurality of fixed base stations including the fixed base station 11 and the fixed base station 21, and controls the fixed base stations and exchanges communication lines. The exchange 32 is connected to a plurality of fixed base stations including the fixed base station 23 by wire, and the exchange 33 is connected to a plurality of fixed base stations including the fixed base station 25 by wire. Performs line switching, etc.

The control device 34 includes the exchange 31 and the exchange 3
2 and a plurality of exchanges including the exchange 33. The control device 34 includes an antenna and a radio transceiver for establishing a dedicated channel with the mobile relay station 40, and controls the mobile relay station 40 to move to a vicinity of a congestion area. Further, when there is a fixed base station that is congested, the control device 34 selects an alternative base station from the fixed base stations connected to the subordinate exchanges, and selects the selected alternative base station as the fixed base station in the congestion area. Instead, let it function as a base station. Further, the control device 34 notifies the mobile relay station 40 of identification information for identifying the selected alternative base station.

Next, the mobile relay station 40 will be described with reference to FIG. FIG. 2 is a functional block diagram showing the internal configuration of the mobile relay station 40. The mobile relay station 40
A 1.5 GHz band or 800 MHz band channel (broadcast channel, access channel, and dedicated physical channel) is set with the communication terminal by the antenna 41, and a dedicated channel is established with the control device 34 by the antenna 42. , 1.5 GHz with the communication terminal by the antenna 43
A channel or an 800 MHz band channel (broadcast channel, access channel, and dedicated physical channel) is set. The antennas 41 and 43 are designed so as not to cause interference in the fixed base station when setting the channel. The transmission / reception units 44 to 46 perform radio reception processing such as frequency conversion on received signals received via the corresponding antennas 41 to 43, and are input from the relay unit 47 that causes the mobile relay station 40 to function as a relay station. The transmission signal is subjected to radio transmission processing such as frequency conversion, and is transmitted by radio from the corresponding antenna 41 to 43.

The control unit 49 receives a control signal transmitted from the control device 34 via the antenna 42 and the transmission / reception unit 45, and controls the control unit 48 based on the control signal. The control unit 48 controls a mobile body (a helicopter, a car, or the like) on which the mobile relay station 40 is mounted. The mobile relay station 40 includes a propulsion device (not shown) and can move to a position according to the control of the control unit 48. The mobile relay station 40 moves to a position where it can communicate with a communication terminal in a congested area under the control of the control unit 48. Transceiver 44
The transmission / reception unit 46 converts the frequency of the transmission signal to the frequency band used by the alternative base station with reference to the identification information obtained by the control unit 49 from the control device 34.

Next, the operation of the mobile communication system having the above configuration will be described. Here, the calling operation of the communication terminal 18 existing in the congested cover area (congestion area) 12 will be described. It is assumed that mobile relay station 40 has already been dispatched near cover area 12 under the control of control device 34. The mobile relay station 40 can set a channel with a communication terminal existing in the coverage area 12 at the dispatched position.

First, the communication terminal 18 communicates with the coverage area 12.
A call signal is transmitted to the fixed base station 11 via the access channel in. However, since there is no free channel in the fixed base station 11, the exchange 31 outputs a signal indicating that a call has been made from the congestion area (hereinafter, simply referred to as a "congestion signal") to the control device 34.

The control unit 34 manages the communication state of the subordinate fixed base stations, and when receiving a congestion signal from the exchange 31, the mobile relay station 40 which relays the communication in the congestion area 12.
And a fixed base station (alternate base station) that provides a communication channel as a base station instead of the fixed base station 11 (target fixed base station). The control device 34 uses the same communication method as the communication method used by the fixed base station 11 (target fixed base station) in the congested area as an alternative base station in order to reduce the processing load caused by relaying between systems using different communication methods. A fixed base station using the scheme is selected with priority. In the present embodiment, in a communication system in which a communication system that performs communication using an 800 MHz band channel and a communication system that performs communication using a 1.5 GHz band channel coexist, a communication terminal using an 800 MHz band channel Since there was an outgoing call from 18, the control device 34
The fixed base station 21 or the fixed base station 25 that performs communication using the channel of the z band is selected with priority over the fixed base station 23 that performs communication using the channel of the 1.5 GHz band. Hereinafter, for the sake of simplicity, a case where the fixed base station 21 is selected as an alternative base station will be described as an example.

When the control device 34 selects the fixed base station 21 as the substitute base station, the control device 34 sets the fixed base station 21 and the mobile relay station 40 from the available channels of the channels allocated to the fixed base station 21. Select an alternate channel to use. When selecting the alternative base station (fixed base station 21) and the alternative channel, the control device 34 controls the alternative base station (fixed base station 21) to notify the mobile relay station 40 of the alternative channel. Thereby, the alternative base station and the mobile relay station are connected by the alternative channel. Also, the mobile relay station 40
Notifies the communication terminal 18 of the alternative channel, and the communication terminal 18 and the mobile relay station 40 are connected by this alternative channel. As described above, the communication terminal 18 is connected to the alternative base station (the fixed base station 21), and the communication terminal 18 can communicate using the alternative channel.

As described above, in the present embodiment, the fixed base station 21 that performs communication using the same 800 MHz band channel as the congestion area is selected as an alternative base station. In this way, by selecting a fixed base station using the same communication method as the congestion area as a substitute base station with priority over a fixed base station using a different communication method, the system can be used when different communication systems coexist. It is possible to reduce the processing load due to the relay between them. In the present embodiment, an example has been described in which a system that performs communication using different frequency bands of the 800 MHz band and the 1.5 GHz band coexists. According to the present embodiment, by selecting a fixed base station having an 800 MHz band channel, processing by frequency conversion is more efficient than when a fixed base station using a 1.5 GHz band channel is selected as an alternative base station. The burden can be reduced.

In the mobile communication system according to the present embodiment, a case where fixed base station 11, fixed base station 21, fixed base station 23, and fixed base station 25 are installed as fixed base stations will be described as an example. However, the present invention is not limited to this.

In the above description, the procedure of selecting an alternative base station and the procedure of relaying from the congested area to the alternative base station when communication systems having different channel frequency bands coexist have been described. Subsequently, a procedure for selecting an alternative base station when a plurality of communication systems using communication methods different from each other except for the frequency band of a channel coexist will be described.

A. When Systems with Different Multiple Access Systems Coexist First, TDMA (Time Division Multiplexing: Time
A case where a Division Multiple Access (CDMA) system and a CDMA (Code Division Multiple Access) system coexist will be described again with reference to FIG.
In FIG. 1, it is assumed that the fixed base stations under the exchanges 31 and 35 use the TDMA method, and the fixed base stations under the exchange 33 adopt the CDMA method.

In the mobile communication system, when a call is made from a communication terminal 18 included in the congestion area 12, the control device 34 selects an alternative base station in consideration of the communication system in the congestion area. Specifically, the control device 3
4 prioritizes a fixed base station using the same communication system as the communication system (TDMA system) used by the fixed base station 11 in order to reduce the processing load caused by relaying between systems using different communication systems. To select. That is, since a call is made from the communication terminal 18 that performs communication using the TDMA method, the fixed base station 21 or the fixed base station 25 that performs communication using the TDMA method is changed to the fixed base station that performs communication using the CDMA method. The selection is made prior to the station 23.

This eliminates the need for a process of converting a frame configuration or the like from the TDMA system to the CDMA system, thereby reducing the processing load in relaying between systems.

B. When systems having different voice coding systems coexist Next, as voice coding methods, a waveform coding method, an analysis voice coding method, and a CELP (Code Excited Linear Pr
ediction) will be described with reference to FIG. 1. FIG.
, The fixed base station under the switch 31 uses the hybrid coding method, the fixed base station under the switch 33 uses the waveform coding method, and the fixed base station under the switch 35 uses the analysis voice coding method. I do.

When a call is made from a communication terminal 18 included in the congestion area 12 in the mobile communication system, the control device 34 sets a communication system (hybrid code) used by the fixed base station 11 as an alternative base station. Fixed base station that uses the same communication scheme as that of the base station).
That is, the communication terminal 1 using the hybrid coding scheme
8, a fixed base station 21 using the same hybrid coding scheme as the communication terminal 18 is selected in preference to the fixed base stations 23 and 25 using other voice coding schemes. .

[0044] This eliminates the need for the process of converting the encoding method, thereby reducing the processing load in relaying between systems. Further, since the mobile relay station 40 does not need to include a plurality of encoders / decoders for converting the coding scheme, the size and cost of the apparatus can be reduced.

As described above, a fixed base station that uses the same frame format as the communication terminal that made the call is also substituted for a system in which the communication system is different in terms of the frame form when performing data communication. By selecting the base station, the conversion of the frame form becomes unnecessary, so that the processing load can be reduced. Further, the communication method in the present embodiment is not limited to the above-described frequency band of the channel, the multiple access method, the voice coding method, and the frame form in the data communication.

(Embodiment 2) In the present embodiment, a relay system in a case where a multi-mode terminal that can be used by appropriately changing a plurality of functions is used in the mobile communication system described in Embodiment 1 will be described. 3 will be described.
In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted.

When a multi-mode terminal 61 to multi-mode terminal 66 shown in FIG. 3 receives a control signal requesting a mode change (hereinafter, simply referred to as a "change signal"), it performs communication by changing a plurality of functions. . Multimode terminals 61-
The multimode terminal 66 can change, for example, a function of performing communication using an 800 MHz band channel and a function of performing communication using a 1.5 GHz band channel.
Further, communication can be performed by changing the frame format of the multiple access system, the voice encoding system, and the data communication. Note that the multi-mode terminals 61 to 66
The function may be changed by a user operation. In this embodiment, a case will be described as an example where a multimode terminal performs communication by alternately changing a function of performing communication using an 800 MHz band channel and a function of performing communication using a 1.5 GHz band channel. .

The exchange 31 houses a fixed base station that performs communication using an 800 MHz band channel. The multimode terminals 61 to 66 are connected to the exchange 3
Wireless communication is performed using the fixed base station 11 under one control and a carrier in the 800 MHz band. The multimode terminal 61 to the multimode terminal 66 perform radio communication with the mobile relay station 40 using an 800 MHz band or a 1.5 GHz band carrier.

Next, the operation of the mobile communication system having the above configuration will be described. Here, the multimode terminal 6 existing in the congested coverage area (congestion area) 12
The calling operation of No. 6 will be described. The mobile relay station 40
Is assumed to have been dispatched near the cover area 12 under the control of the control device 33.

First, the multimode terminal 66 transmits a calling signal to the fixed base station 11 via the access channel in the cover area 12. However, since there is no free channel in the fixed base station 11, the exchange 31 outputs a congestion signal to the control device 34.

Upon acquiring the congestion signal from the exchange 31, the control unit 34 selects a mobile relay station 40 for relaying communication in the congestion area 12 and an alternative base station. The control device 34 preferentially selects a fixed base station using the same communication system as the communication system used by the fixed base station (target fixed base station) 11 in which congestion has occurred, as an alternative base station. If a fixed base station using the same communication scheme as the base station cannot secure a line (if there is no available channel), a fixed base station using a communication scheme different from that of the fixed base station 11 in which congestion occurs is replaced with an alternative base station. Select as Specifically, an attempt is made to preferentially select the fixed base station 21 or the fixed base station 25 using the channel of the 800 MHz band, but if congestion also occurs in these base stations, the 1.5 GHz band is selected. The fixed base station 23 that uses the channel of (1) is selected. When selecting the alternative base station (the fixed base station 23 in this case), the control device 34 selects an alternative channel (1) to be set between the mobile relay station 40 and the available channels of the channels allocated to the fixed base station 23. .5 GHz band).

The control device 34 controls the selected alternative base station (fixed base station 23) to notify the mobile relay station 40 of the alternative channel. Thereby, the alternative base station and the mobile relay station are connected by the alternative channel. Further, the control device 34 controls the mobile relay station 40 to
6 is notified of the alternative channel. The multimode terminal 66 and the mobile relay station 40 are connected by this alternative channel. As described above, the multimode terminal 66 is connected to the alternative base station (fixed base station 23), and the multimode terminal 6
6 can communicate using the alternative channel.

The control device 34 outputs a signal indicating that the fixed base station 23 using a frequency band different from the frequency band used by the calling communication terminal 18 has been selected as an alternative base station (hereinafter simply referred to as “change”). ) Is transmitted to the multimode terminal 66 via the exchange 31 and the fixed base station 11. The change signal may be transmitted to the multi-mode terminal 66 via the mobile relay station 40.

When receiving the change signal, the multimode terminal 66 switches the mode for 800 MHz to the mode for 1.5 GHz. Specifically, communication is performed using software that executes the mode specified by the change signal. Alternatively, communication is performed using a DSP that executes a mode specified by the change signal. After changing the mode to the 1.5 GHz mode, the multimode terminal 66
The communication is performed using the 1.5 GHz channel set between.

As described above, according to the present embodiment, when a fixed base station using a communication method different from the communication method used by the fixed base station in the congested area is selected as the alternative base station, the multi-mode call originated. Changing the mode of the terminal 66 to a mode adapted to the communication method used by the alternative base station,
Communication is performed in the mode after the change. Therefore, even when relaying between systems using different communication methods, the mobile relay station 40 does not need to perform conversion processing such as frequency conversion, and can reduce the processing load at the time of relaying.

As described above, when systems with different multiple access systems coexist, systems with different audio coding systems coexist, and systems with different data communication frame formats coexist, as described above. By changing the mode of the called multi-mode terminal to a mode adapted to the communication system used by the alternative base station, the processing load at the time of relaying can be reduced.

(Embodiment 3) In this embodiment, a relay system in a case where a multi-mode terminal and a single-mode terminal comprising a single mode are mixed in an area will be described in detail with reference to FIG. I do. In FIG. 4, the same parts as in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and the detailed description thereof will be omitted.

As shown in FIG. 4, the congested cover area 12 accommodates multi-mode terminals 71, 73, 75 and single-mode terminals 72, 74, 76. The multimode terminals 71, 73, and 75 can perform communication in any of the 800 MHz band and the 1.5 GHz band by changing the mode. Further, communication can be performed by changing the frame format of the multiple access system, the voice encoding system, and the data communication. On the other hand, the single-mode terminals 72, 74, and 76 communicate using one mode of the multi-mode terminal. In the present embodiment,
The multi-mode terminal performs communication by alternately changing the function of performing communication using the 800 MHz band channel and the function of performing communication using the 1.5 GHz band channel, and the single mode terminal uses the 800 MHz band channel. The following describes an example in which the communication is performed by using the communication. Hereinafter, the operation of the mobile communication system having the above-described configuration will be described by taking as an example a case where a call is made from the multimode terminal 75 and the single mode terminal 76.

First, the multi-mode terminal 75 and the single-mode terminal 76 transmit a call signal to the fixed base station 11 via the access channel in the cover area 12. However, since there is no free channel in the fixed base station 11, the exchange 31 outputs a congestion signal of each terminal to the control device 34.

The control unit 34 receives the congestion signal from the exchange 31, and relays the communication in the congested coverage area 12, the mobile relay station 40, the alternative base station for the multimode terminal 75, and the Are selected as alternative base stations. The control device 34 preferentially selects a fixed base station using the 800 MHz channel used by the fixed base station 11. The controller 34 determines that the single mode terminal 76 is
Considering that communication can be performed only on the channel of the 0 MHz band (that is, communication cannot be performed on the channel of the 1.5 GHz band), the multi-mode terminal 7
800M preferentially for single mode terminal 76 over 5
A fixed base station using a channel in the Hz band is allocated. That is, if there is a free channel in a fixed base station using an 800 MHz band channel, the fixed base station is first selected as an alternative base station for a single mode terminal. And as an alternative base station for the multimode terminal 75,
If there is an 800 MHz fixed base station having an empty channel after selecting the alternative base station of the single mode terminal 76, an 800 MHz fixed base station is selected and there is no 800 MHz fixed base station having an empty channel. In this case, a fixed base station using a channel in the 1.5 GHz band is selected.

The control device 34 controls the selected alternative base station to make the mobile relay station 40 broadcast the alternative channel. Thereby, the alternative base station and the mobile relay station are connected by the alternative channel. Further, the control device 34 controls the mobile relay station 40 to make the multi-mode terminal 75 and the single-mode terminal 76 broadcast an alternative channel. This alternate channel allows the multimode terminal 75 and the single mode terminal 76
And the mobile relay station 40 are connected. As described above, the multi-mode terminal 75 and the single-mode terminal 76 are connected to the respective alternative base stations, and the multi-mode terminal 75 and the single-mode terminal 76 can communicate using the alternative channel.

As described above, according to the present embodiment, when a multi-mode terminal and a single-mode terminal coexist in a congestion area, the same communication system as that of fixed base station 11 in which congestion occurs is used. The fixed base station to be used is preferentially allocated to the single mode terminal. Thereby, the call loss of the single mode terminal can be reduced.

As described above, when systems with different multiple access systems coexist, systems with different audio coding systems coexist, and systems with different data communication frame formats coexist, as described above. By preferentially assigning a fixed base station using a communication scheme used in an area to a single-mode terminal, it is possible to reduce the processing load when performing relaying.

(Embodiment 4) In this embodiment, in the mobile communication system described in Embodiment 1, a plurality of functions are appropriately changed by downloading software as needed from a mobile relay station. Figure 5 shows the relay method using a software defined radio
This will be described with reference to FIG. In FIG. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and the detailed description thereof will be omitted.

The software defined radio has a function of a radio (radio device) conventionally constituted by an analog circuit and has a DSP (Digita
l Signal Processor), FPGA (Field Programmable)
Gate Array) and ASIC (Application Specific)
It is a wireless device realized by digital circuits such as IC). In a software defined radio, since signal processing functions such as channel separation and modulation / demodulation processing performed in analog manner are processed by software after A / D conversion, the functions can be flexibly changed.

When the software radio 81 to software radio 86 shown in FIG. 5 receives a control signal requesting a mode change (hereinafter, simply referred to as a “change signal”), the software radio 81 Download the software to execute the mode. Software radio 81
The software radio 86 is software or 1.5 for realizing radio communication using an 800 MHz band channel.
By downloading software that realizes wireless communication using a channel in the GHz band, wireless communication can be performed using either the 800 MHz band or the 1.5 GHz band.

Next, the operation of the mobile communication system having the above configuration will be described. Here, the calling operation of the software defined radio 86 existing in the congested coverage area 12 (congestion area) will be described. The mobile relay station 40
Has already been dispatched in the vicinity of the cover area 12 under the control of the control device 33, and it is possible to set a channel with a communication terminal existing in the cover area 12. The software defined radio 86 is connected to the mobile relay station 40.
When communication is performed with the fixed base station 11 without going through
It is assumed that a channel in the 0 MHz band is used.

First, software defined radio 86 transmits a call signal to fixed base station 11 via the access channel in cover area 12. However, the fixed base station 11
Since there is no free channel in, the exchange 31 outputs a congestion signal to the control device.

Upon receiving the congestion signal from the exchange 31, the control unit 34 selects a mobile relay station 40 for relaying communication in the congested coverage area 12 and an alternative base station for the software defined radio 86. The controller 34 preferentially selects a fixed base station using the same communication system as the communication system used by the congested fixed base station 11 (target fixed base station) as an alternative base station. If a line cannot be secured in a fixed base station using the same communication method as that of the target fixed base station, a fixed base station using a communication method different from that of the target fixed base station is selected. Specifically, 800 MHz
Base station 21 or fixed base station 2 using band channel
5 is preferentially selected, but when congestion occurs in these base stations as well, the fixed base station 23 using a 1.5 GHz band channel is selected. In addition, the control device 34 controls the alternative base station (here, the fixed base station 23).
Is selected, an alternative channel (1.5 GHz band) set with the mobile relay station 40 is selected from the available channels allocated to the fixed base station 23.

The control device 34 controls the selected alternative base station (fixed base station 23) to make the mobile relay station 40 broadcast the alternative channel. Thereby, the alternative base station and the mobile relay station are connected by the alternative channel. In addition, the control device 34 controls the mobile relay station 40 to make the software defined radio 86 broadcast an alternative channel. The software radio 86 and the mobile relay station 40 are connected by this alternative channel. As described above, the software defined radio 86 and the alternative base station (fixed base station 23) are connected, and the software defined radio 86 can communicate using the alternative channel.

Further, control device 34 provides a signal indicating that fixed base station 23 using a communication system different from the communication system used by calling communication terminal 18 has been selected as an alternative base station (hereinafter simply referred to as a “change signal”). Is transmitted to the software defined radio 86 via the exchange 31 and the fixed base station 11. The change signal may be transmitted to the software defined radio 86 via the mobile relay station 40.

When receiving the change signal, software radio 86 requests download of software for realizing a mode (wireless communication in 1.5 GHz band) different from the current mode (wireless communication in 800 MHz band). The signal is transmitted to the mobile relay station 40. The mobile relay station 40 transfers software (hereinafter, software for 1.5 GHz) for realizing the requested 1.5 GHz band wireless communication to the software defined radio 86. Software defined radio 8
6 downloads the software when the download is completed.
Update to 5GHz software. In this way,
The software defined radio 86 communicates with the mobile relay station 40 using a 1.5 GHz band channel set.

As described above, according to the present embodiment, when a fixed base station using a communication system different from the communication system used by the fixed base station in which congestion occurs is selected as an alternative base station, a call is originated. The software radio device 86 downloads software for realizing communication in the communication method used by the alternative base station from the mobile relay station 40, and performs communication using the downloaded software. Therefore, the mobile relay station 40 does not need to perform conversion processing such as frequency conversion even when relaying is performed between systems having different communication schemes, which is a case where communication systems having different communication schemes coexist. However, the processing load at the time of relaying between systems can be reduced.

As described above, when systems with different multiple access systems coexist, systems with different audio coding systems coexist, and systems with different frame formats for data communication coexist, as described above. The called software radio 86 downloads the software that realizes communication in the system in which the alternative base station is accommodated, and performs communication, thereby reducing the processing load at the time of relaying.

Note that the present invention is not limited to the above-described embodiments, and for example, the above-described embodiments can be appropriately combined and used.

[0076]

As described above, according to the present invention,
When communication systems having different communication systems coexist, by preferentially selecting a fixed base station using the same communication system as the communication system used by the fixed base station in the congestion area as a substitute base station, Communication performed by the communication terminal accommodated in the fixed base station can be efficiently relayed to the alternative base station.

[Brief description of the drawings]

FIG. 1 is a diagram showing a partial configuration of a mobile communication system including a mobile relay station according to Embodiment 1 of the present invention.

FIG. 2 is a functional block diagram showing an internal configuration of a mobile relay station.

FIG. 3 is a diagram showing a partial configuration of a mobile communication system including a mobile relay station according to Embodiment 2 of the present invention.

FIG. 4 is a diagram showing a partial configuration of a mobile communication system including a mobile relay station according to Embodiment 3 of the present invention.

FIG. 5 is a diagram showing a partial configuration of a mobile communication system including a mobile relay station according to Embodiment 4 of the present invention.

[Explanation of symbols]

 11, 21, 23, 25 Fixed base station 13-18 Communication terminal 31, 32, 33 Switch 34 Controller 40 Mobile relay station 61-66, 71, 73, 75 Multi-mode terminal 72, 74, 76 Single-mode terminal 81 ~ 86 software radio

Claims (7)

[Claims] 1. A plurality of fixed base stations for performing wireless communication with a communication terminal existing in a coverage area of the own station, and control for selecting at least one fixed base station included in the plurality of fixed base stations as an alternative base station. Apparatus, and a movable mobile relay station that relays communication in the target fixed base station included in the plurality of fixed base stations to the alternative base station, and the control device is used by the target fixed base station. A mobile communication system characterized by preferentially selecting a fixed base station using the same communication system as the communication system. 2. The target fixed base station performs wireless communication with a multimode terminal existing in its own coverage area, and the multimode terminal performs a mode for performing communication using the same communication scheme as the target fixed base station. 2. The mobile communication system according to claim 1, wherein the wireless communication is performed by changing the mode to a mode for performing communication by the same communication method as the alternative base station. 3. The target fixed base station performs wireless communication with a multi-mode terminal and a single-mode terminal existing in its own coverage area, and the control device, when selecting an alternative base station, transmits a signal from the multi-mode terminal. The mobile communication system according to claim 1, wherein a fixed base station using the same communication system as the communication system used by the target fixed base station is assigned to the single mode terminal with priority. 4. The target fixed base station performs wireless communication with a software radio located in its own coverage area, and the software radio implements software that implements communication by a communication method used by an alternative base station. The mobile communication system according to claim 1, wherein the mobile communication system performs acquisition and wireless communication. 5. The mobile relay station according to claim 1, wherein the mobile terminal relays the communication of the communication terminal originating the call in the coverage area of the target fixed base station in which all the allocated channels are used to the alternative base station. The mobile communication system according to any one of claims 1 to 4. 6. A mobile relay station that relays communication at a target fixed base station included in a plurality of fixed base stations to an alternative base station, wherein the same communication scheme as the alternative base station is used as a communication method used by the target fixed base station. Means for acquiring identification information for identifying an alternative base station selected from a control device that preferentially selects a fixed base station using a method, and a position at which communication can be performed with a communication terminal present in the coverage area of the target fixed base station. A mobile relay station comprising: moving means for moving; and means for relaying communication in the target fixed base station to the alternative base station. 7. A mobile communication method in which a plurality of fixed base stations connected to a network wirelessly communicate with a communication terminal existing in a coverage area of the own station,
A step of preferentially selecting a fixed base station using the same communication scheme as the communication scheme used by the target fixed base station included in the plurality of fixed base stations, and relaying communication in the target fixed base station to the alternative base station Performing the mobile communication method.