JP2014195176A - Communication system, communication terminal and base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable power saving in a communication terminal that can perform communication using a plurality of communication methods with different used radio resources.SOLUTION: A transmission device in a base station transmits a predetermined signal through a predetermined channel. Here, the predetermined channel signifies a channel existent in a second frequency band corresponding to the 3G system and allocated to report the existence of a service area conforming to a wireless LAN system. A processor 33 in a communication terminal 30 activates a communication device 32 on determining the existence of a signal received through the predetermined channel by a communication device 31.

Description

  The present invention relates to a communication system, a communication terminal, and a base station.

  In recent years, public wireless LAN (Local Area Network) services are rapidly spreading as a complement to mobile phone network services. As an example of the cellular phone network, a network corresponding to a third generation mobile communication system (3G: 3rd Generation) can be cited. Furthermore, as an example of a mobile phone network, a network corresponding to 3GPP LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution) which is a communication standard can be cited.

  By introducing a public wireless LAN, the communication load of the mobile phone network can be distributed, which is advantageous for communication carriers. Furthermore, the introduction of a public wireless LAN enables high-speed and stable communication, which is advantageous for users.

  Here, the base station of the public wireless LAN has a smaller “range” than the base station of the mobile phone network. The “range” is an area where radio waves transmitted from one base station can reach. Furthermore, the “service area” of the public wireless LAN is narrower than the service area of the mobile phone network. The “service area” is an area where communication is possible over the entire network.

  Therefore, a communication terminal compatible with both a mobile phone system and a public wireless LAN system is usually connected to a mobile phone network with a wide service area, and when entering the wireless LAN service area, The connection is switched to the wireless LAN. This switching can be realized, for example, by setting the communication terminal to automatically switch to the wireless LAN when a known signal transmitted from the wireless LAN base station is received.

JP 2002-199426 A

  However, in order for the communication terminal to automatically switch the connection network, both the frequency band assigned to the mobile phone system and the frequency band assigned to the wireless LAN system are always monitored. Thereby, the power consumption of a communication terminal will become large. This problem is not limited to a mobile phone system and a wireless LAN system, but applies to a plurality of communication systems having different assigned frequency bands.

  The disclosed technology has been made in view of the above, and provides a communication system, a communication terminal, and a base station that can save power in a communication terminal that can communicate with a plurality of communication methods using different radio resources. For the purpose.

  In the disclosed aspect, when a signal transmitted on a predetermined channel is received, a communication device corresponding to the first communication method is activated. The predetermined channel is a channel in the second frequency band corresponding to the second communication method and assigned to notify the presence of the service area corresponding to the first communication method.

  According to the disclosed aspect, it is possible to save power for a communication terminal that can communicate with a plurality of communication schemes using different radio resources.

FIG. 1 is a schematic diagram of an example of a communication system according to the first embodiment. FIG. 2 is a block diagram illustrating an example of the first base station according to the first embodiment. FIG. 3 is a block diagram illustrating an example of the second base station according to the first embodiment. FIG. 4 is a block diagram illustrating an example of a communication terminal according to the first embodiment. FIG. 5 is a diagram for explaining the state change of the communication terminal due to the movement of the communication terminal. FIG. 6 is a diagram for explaining the processing operation of the communication system accompanying the movement of the communication terminal. FIG. 7 is a diagram for explaining the state transition of the communication terminal.

  Hereinafter, embodiments of a communication system, a communication terminal, and a base station disclosed in the present application will be described in detail based on the drawings. Note that the communication system, communication terminal, and base station disclosed in the present application are not limited by this embodiment. Moreover, the same code | symbol is attached | subjected to the structure which has the same function in embodiment, and the overlapping description is abbreviate | omitted.

[Example 1]
[Outline of communication system]
FIG. 1 is a schematic diagram of an example of a communication system according to the first embodiment. In FIG. 1, the communication system 1 includes base stations 10-1, 2, 3 corresponding to the second communication method, base stations 20-1, 2 corresponding to the first communication method, the first communication method, And a communication terminal 30 that can communicate with both of the second communication methods. The numbers of the base station 10, the base station 20, and the terminal 30 are examples and are not limited thereto. In the following description, the base stations 10-1, 2, 3 may be simply referred to as the base station 10 unless otherwise distinguished. Further, when the base stations 20-1 and 20-2 are not particularly distinguished, they may be simply referred to as the base station 20.

  The base stations 20-1 and 20-2 are included in the first communication system corresponding to the first communication method, while the base stations 10-1, 2, and 3 are the second communication corresponding to the second communication method. Included in the system. That is, the communication system 1 includes a first communication system and a second communication system.

  A first frequency band is assigned to the first communication system, and a second frequency band is assigned to the second communication system.

  The base station 10 communicates using a channel assigned to the base station 10 in the second frequency band. For example, as shown in FIG. 1, the base station 10-1 transmits using the channel C11 assigned to the base station 10-1 in the second frequency band. Base stations 10-2 and 3 transmit using channels C12 and C13 allocated to base stations 10-2 and 3 in the second frequency band, respectively. In FIG. 1, areas A <b> 11, A <b> 12, and A <b> 13 are range areas corresponding to the second communication method of the base stations 10-1, 2, and 3, respectively. Here, the “channel” is defined by at least one of frequency, time, and code.

  On the other hand, the base station 20 communicates using a channel assigned to the base station 20 in the first frequency band. For example, as shown in FIG. 1, the base station 20-1 transmits using the channel C21 assigned to the base station 20-1 in the first frequency band. The base station 20-2 transmits using the channel C22 assigned to the base station 20-2 in the first frequency band. In FIG. 1, areas A21 and A22 are range areas corresponding to the first communication method of the base stations 20-1 and 20-2, respectively. Further, if the area A21 and the area A22 do not overlap, the channel C21 and the channel C22 may be the same or different.

  Further, the base station 20 transmits a “predetermined signal” using the “predetermined channel”. The “predetermined channel” is a channel in the second frequency band, and is a channel assigned to notify the presence of a service area corresponding to the first communication method. That is, the base station 20 communicates in the first frequency band, and further transmits a predetermined signal on a channel in the second frequency band. For example, the base stations 20-1 and 20-2 transmit a predetermined signal through the predetermined channel C31. Here, the common channel C31 is used in the base stations 20-1 and 20-2 because the communication terminal 30 does not need to distinguish the base station 20 that is the transmission source of the channel C31. By using the common channel C31, radio resources for a predetermined channel can be minimized. Further, the predetermined signal may be a known signal such as a beacon or a signal corresponding to an SSID (Service Set Identifier). In FIG. 1, areas A31 and A32 are range areas corresponding to predetermined channels of the base stations 20-1 and 20-2, respectively.

  When connected to the second communication system, the communication terminal 30 monitors a predetermined channel. The communication terminal 30 turns off the communication device corresponding to the first communication method while receiving no signal on the predetermined channel. Then, when receiving a signal on the predetermined channel, the communication terminal 30 turns on the communication device corresponding to the first communication method, and switches the connection destination system from the second communication system to the first communication system. That is, in FIG. 1, when the communication terminal 30 is out of the areas A31 and A32, the communication device corresponding to the first communication method is turned off and the first communication method is not entered until the communication device 30 enters the areas A31 and A32. Turn on the communication device corresponding to.

  As described above, the communication terminal 30 can specify that the communication terminal 30 has entered the service area of the first communication system by simply turning on the communication device corresponding to the second communication system. The communication device corresponding to the system can be turned off. Thereby, since the power consumption of the communication terminal 30 can be reduced, the power saving of the communication terminal 30 is realizable.

  Hereinafter, as an example, a case will be described in which the first communication system is a wireless LAN system and the second communication system is a mobile phone system (for example, a 3G system).

[Configuration Example of Base Station 10]
FIG. 2 is a block diagram illustrating an example of the first base station according to the first embodiment. In FIG. 2, the base station 10 includes a communication device 11, a processor 12, and a memory 13. Examples of the processor 12 include a central processing unit (CPU), a digital signal processor (DSP), and a field programmable gate array (FPGA). Examples of the memory 13 include a RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, and the like. The communication device 11 is realized by, for example, an LSI (Large Scale Integrated circuit).

  The communication device 11 is a device that supports the 3G system. That is, the communication device 11 communicates with the communication terminal 30 using the 3G method.

  For example, the communication device 11 includes a wireless unit 14 and a baseband processing unit 15. The radio unit 14 receives a radio signal by the 3G method via the antenna, and performs predetermined reception radio processing, that is, down-conversion, analog-digital conversion, and the like on the received radio signal. The baseband processing unit 15 performs baseband processing, that is, demodulation and decoding, on the baseband signal obtained by the wireless unit 14. The baseband processing unit 15 performs encoding and modulation on the transmission signal received from the processor 12 to form a baseband signal. The radio unit 14 performs predetermined transmission radio processing, that is, digital-analog conversion, up-conversion, and the like on the baseband signal obtained by the baseband processing unit 15 to form a radio signal, and 3G system via an antenna Send with.

  The processor 12 generates a transmission signal to be transmitted to the communication terminal 30 and transmits it via the communication device 11. For example, the processor 12 generates a notification signal indicating that a service area corresponding to the first communication method exists in the range of the base station 10.

  The memory 13 stores various programs used by the processor 12 and various data. Various processes by the processor 12 are realized by the program stored in the memory 13 being read and executed by the processor 12.

[Configuration Example of Base Station 20]
FIG. 3 is a block diagram illustrating an example of the second base station according to the first embodiment. In FIG. 3, the base station 20 includes a communication device 21, a transmission device 22, a processor 23, and a memory 24. Examples of the processor 23 include a CPU, a DSP, and an FPGA. Examples of the memory 24 include RAM such as SDRAM, ROM, flash memory, and the like. The communication device 21 and the transmission device 22 are realized by, for example, an LSI (Large Scale Integrated circuit).

  The communication device 21 is a device that supports the wireless LAN system. That is, the communication device 21 communicates with the communication terminal 30 using the wireless LAN method.

  For example, the communication device 21 includes a wireless unit 25 and a baseband processing unit 26. The wireless unit 25 receives a wireless signal by a wireless LAN system via an antenna, and performs predetermined reception wireless processing, that is, down-conversion, analog-digital conversion, and the like on the received wireless signal. The baseband processing unit 26 performs baseband processing, that is, demodulation and decoding, on the baseband signal obtained by the radio unit 25. In addition, the baseband processing unit 26 performs encoding and modulation on the transmission signal received from the processor 23 to form a baseband signal. The radio unit 25 performs predetermined transmission radio processing, that is, digital-analog conversion, up-conversion, and the like on the baseband signal obtained by the baseband processing unit 26 to form a radio signal, and performs wireless LAN via an antenna. Send by method.

  The transmission device 22 is configured to be able to transmit a predetermined signal in the second frequency band corresponding to the 3G system. That is, the transmission device 22 transmits a predetermined signal using a predetermined channel. The predetermined channel here is a channel in the second frequency band, and is a channel assigned to notify the presence of a service area corresponding to the wireless LAN system.

  For example, the transmission device 22 includes a transmission radio unit 27 and a baseband processing unit 28. The baseband processing unit 28 forms a baseband signal using a predetermined signal received from the processor 23. The transmission radio unit 27 performs predetermined transmission radio processing, that is, digital-analog conversion, up-conversion, and the like on the baseband signal obtained by the baseband processing unit 26 to form a radio signal, and performs predetermined transmission via an antenna. Transmit on the channel. Here, as long as the communication terminal 30 can determine the presence / absence of a signal in a predetermined channel, the baseband processing unit 28 may not perform processing such as encoding and modulation on the predetermined signal.

  Here, the transmission power value of the predetermined signal may be equal to or greater than the maximum transmission power value of the signal transmitted by the communication device 21. This is to enable the communication terminal 30 that has received the predetermined signal to determine that a service area corresponding to the wireless LAN system exists nearby.

  The processor 23 generates a transmission signal to be transmitted to the communication terminal 30 by the wireless LAN method, and outputs the transmission signal to the communication device 21. Further, the processor 23 generates the predetermined signal and outputs it to the transmission device 22.

  The memory 24 stores various programs used by the processor 23 and various data. Various processes by the processor 23 are realized by the program stored in the memory 24 being read and executed by the processor 23.

[Configuration Example of Communication Terminal 30]
FIG. 4 is a block diagram illustrating an example of a communication terminal according to the first embodiment. In FIG. 4, the communication terminal 30 includes communication devices 31 and 32, a processor 33, and a memory 34. The communication terminal 30 is configured to be able to communicate with both the wireless LAN method and the 3G method. Examples of the processor 33 include a CPU, a DSP, and an FPGA. Examples of the memory 34 include RAM such as SDRAM, ROM, flash memory, and the like. The communication devices 31 and 32 are realized by, for example, an LSI (Large Scale Integrated circuit).

  The communication device 31 is a device that supports the 3G system. That is, the communication device 31 transmits and receives signals using the second frequency band corresponding to the 3G system. That is, the communication device 31 communicates with the base station 10 using the 3G method. Furthermore, the communication device 31 performs a process of receiving a predetermined channel in the second frequency band corresponding to the 3G system.

  For example, the communication device 31 includes a wireless unit 35 and a baseband processing unit 36. The radio unit 35 receives a radio signal in the second frequency band via the antenna, and performs predetermined reception radio processing, that is, down-conversion, analog-digital conversion, and the like on the received radio signal. The baseband processing unit 36 performs baseband processing, that is, demodulation and decoding, on the baseband signal obtained by the wireless unit 35. The baseband processing unit 36 performs encoding and modulation on the transmission signal received from the processor 33 to form a baseband signal. The radio unit 35 performs predetermined transmission radio processing, that is, digital-analog conversion, up-conversion, and the like on the baseband signal obtained by the baseband processing unit 36 to form a radio signal, and 3G system via an antenna Send with.

  The communication device 32 is a device that supports the wireless LAN system. That is, the communication device 32 communicates with the base station 20 using the wireless LAN method.

  For example, the communication device 32 includes a wireless unit 37 and a baseband processing unit 38. The wireless unit 37 receives a wireless signal by a wireless LAN system via an antenna, and performs predetermined reception wireless processing, that is, down-conversion, analog-digital conversion, and the like on the received wireless signal. The baseband processing unit 38 performs baseband processing, that is, demodulation and decoding, on the baseband signal obtained by the radio unit 37. The baseband processing unit 38 performs encoding and modulation on the transmission signal received from the processor 33 to form a baseband signal. The radio unit 37 performs predetermined transmission radio processing, that is, digital-analog conversion, up-conversion, and the like on the baseband signal obtained by the baseband processing unit 38 to form a radio signal, and performs wireless LAN via an antenna. Send with.

  The processor 33 measures the radio wave level in each channel in the second frequency band in the first period. By this measurement, the channel corresponding to the base station 20 that is transmitting a signal that can reach the communication terminal 30 can be specified. The measurement target channel includes the predetermined channel. That is, the processor 33 monitors whether a signal is received by a predetermined channel. Note that measurements on channels other than the predetermined channel may be performed in the first cycle, and measurements on the predetermined channel may be performed in the second cycle longer than the first cycle. For example, measurement for a predetermined channel may be performed at a part of a plurality of measurement timings repeated in the first cycle. Further, the processor 33 may start monitoring a predetermined channel triggered by receiving the notification signal transmitted from the base station 10. Here, in determining whether or not a signal is received on a predetermined channel, it is determined that the signal is received when the radio wave level measured on the predetermined channel is equal to or higher than a threshold value, and is not received when the signal level is lower than You may judge.

  Further, the processor 33 performs control to turn off the communication device 32 corresponding to the wireless LAN system when the signal is not received through the predetermined channel. On the other hand, when a signal is received through a predetermined channel, the processor 33 turns on the communication device 32 corresponding to the wireless LAN system and switches the connection destination system from the 3G system to the wireless LAN system. That is, the processor 33 switches the communication device used for communication from the communication device 31 to the communication device 32.

  The memory 34 stores various programs used by the processor 33 and various data. Various processes by the processor 33 are realized by the program stored in the memory 34 being read and executed by the processor 33.

[Operation of Communication System 1]
Processing operations in the communication system 1 having the above configuration will be described. FIG. 5 is a diagram for explaining the state change of the communication terminal due to the movement of the communication terminal. FIG. 6 is a diagram for explaining the processing operation of the communication system accompanying the movement of the communication terminal. FIG. 7 is a diagram for explaining the state transition of the communication terminal. The processing operation of the communication terminal 30 described below is mainly performed by the processor 33 described above.

  First, when the communication terminal 30 exists in the point L1 of FIG. 5, it is in the state connected with the base station 10-1. This state corresponds to state 2 in FIG. In this state, the base station 10-1 transmits the notification signal to the communication terminal 30 (step S101).

  Then, the communication terminal 30 starts measurement of the predetermined channel, that is, monitoring of the predetermined channel (step S102).

  And the communication terminal 30 shall move continuously toward the point L2. The base station 20-1 transmits a predetermined signal on the channel C31 (steps S103 to S105), but the communication terminal 30 cannot receive the predetermined signal until the point L2 is reached (see steps S103 and S104). . Only after the communication terminal 30 reaches the point L2 and enters the area A31, the communication terminal 30 can receive the predetermined signal (see step S105).

  And the communication terminal 30 can detect a predetermined signal, if the detection process of a predetermined channel is performed (step S106). Then, the communication terminal 30 turns on the communication device 32 corresponding to the wireless LAN method from off (step S107). This state corresponds to state 3 in FIG.

  Then, the communication terminal 30 starts connection processing with the wireless LAN system (step S108). Here, when the transmission power value of the predetermined signal is larger than the maximum transmission power of the wireless LAN system of the base station 20-1, the communication terminal 30 cannot establish a wireless LAN connection until reaching the point L3. (Step S109).

  The communication terminal 30 can establish a wireless LAN connection only after reaching the point L3 and entering the area 21 (step S110). This state corresponds to state 4 in FIG.

  Furthermore, it is assumed that the communication terminal 30 passes through the point L4 and moves to the point L5. Before the communication terminal 30 moves to the point L5, it first deviates from the area A21. When the communication terminal 30 is out of the area A21, the connection between the communication terminal 30 and the base station 20-1 is disconnected. Then, the communication terminal 30 performs a wireless LAN disconnection process (step S111). This state corresponds to state 3 in FIG.

  Next, the communication terminal 30 is out of the area A31. If it deviates from the area A31, the communication terminal 30 cannot receive the predetermined signal. For this reason, the communication terminal 30 cannot detect the predetermined channel even if the predetermined channel detection process is executed (step S112).

  Then, the communication terminal 30 turns the wireless LAN communication device 32 from on to off (step S113). This state corresponds to state 2 in FIG. In addition, the state 1 in FIG. 7 is a state where it is not connected to the 3G system.

  As described above, according to the present embodiment, in the base station 20, the transmission device 22 transmits a predetermined signal on a predetermined channel. Here, the predetermined channel is a channel in the second frequency band corresponding to the 3G system and a channel assigned to notify the existence of a service area corresponding to the wireless LAN system.

  Then, in the communication terminal 30, the processor 33 activates the communication device 32 when it is determined that there is a signal received by the communication device 31 on the predetermined channel.

  With this configuration of the communication terminal 30, it is possible to specify that the wireless LAN system has entered the service area simply by turning on the communication device 31, so that the communication device 32 can be turned off. Thereby, since the power consumption of the communication terminal 30 can be reduced, the power saving of the communication terminal 30 is realizable.

  In the base station 10, the communication device 11 transmits a notification signal indicating that a service area corresponding to the wireless LAN system exists within the range of the base station 10.

  Then, in the communication terminal 30, when the notification signal is received by the communication device 31, the processor 33 starts determining whether or not there is a reception signal on the predetermined channel.

  With this configuration of the communication terminal 30, the determination process can be performed only when the service area corresponding to the wireless LAN system is surely present within the range of the base station 10 in which the communication terminal 30 is located. As a result, it is possible to prevent the communication terminal 30 from performing wasteful determination processing, so that the power consumption of the communication terminal 30 can be further reduced.

  Further, in the communication terminal 30, the processor 33 stops the communication device 32 when determining that there is no signal received on the predetermined channel.

  With this configuration of the communication terminal 30, the communication device 32 can be stopped when it can be determined that there is no wireless LAN system service area around the point where the communication terminal 30 exists. Thereby, since the power consumption of the communication terminal 30 can be reduced, the power saving of the communication terminal 30 is realizable.

  Further, in the base station 20, the transmission device 22 transmits the predetermined signal with transmission power equal to or higher than the maximum transmission power value of the communication device 21.

  With this configuration of the base station 20, the communication terminal 30 can know that the area exists in the vicinity before entering the wireless LAN service area. For this reason, the communication terminal 30 can perform communication preparation processing by the wireless LAN method in advance, and thus can stably start communication by the wireless LAN method.

[Other embodiments]
Each component of each part illustrated in the first embodiment does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each part is not limited to the one shown in the figure, and all or a part thereof may be functionally or physically distributed / integrated in arbitrary units according to various loads and usage conditions. Can be configured.

  Furthermore, the various processing functions performed in each apparatus of the first embodiment are all or arbitrary on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). A part of the above may be executed. Various processing functions may be executed entirely or arbitrarily on a program that is analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU) or hardware based on wired logic. .

  That is, the various processes described in the first embodiment can be realized by reading a program prepared in advance from a memory by a terminal or a processor of a base station and executing each read program.

DESCRIPTION OF SYMBOLS 1 Communication system 10, 20 Base station 11, 21, 31, 32 Communication device 12, 23, 33 Processor 13, 24, 34 Memory 14, 25, 35, 37 Wireless part 15, 26, 28, 36, 38 Baseband processing Unit 22 Transmission device 27 Transmission wireless unit 30 Communication terminal

Claims (7)

A first communication device configured to be able to transmit and receive signals in a first frequency band corresponding to a first communication method; a channel in a second frequency band corresponding to a second communication method; A base station having a transmission device that transmits a predetermined signal on a predetermined channel, which is a channel allocated to notify the presence of a service area corresponding to one communication method;
A second communication device configured to transmit and receive signals in the first frequency band; a third communication device configured to transmit and receive signals in the second frequency band; and the third communication device. A communication terminal having a processor that activates the second communication device when it is determined that there is a signal received on the predetermined channel by:
A communication system comprising: A first communication device configured to transmit and receive signals in a first frequency band corresponding to the first communication method;
A second communication device configured to transmit and receive signals in a second frequency band corresponding to the second communication method;
A signal received by the second communication device on a predetermined channel that is a channel in the second frequency band and assigned to notify the presence of a service area corresponding to the first communication method. A processor that activates the first communication device when it is determined that
A communication terminal comprising: The processor starts a determination on the presence or absence of a reception signal on the predetermined channel when a notification indicating the presence of the service area is received by the second communication device;
The communication terminal according to claim 2. If the processor determines that there is no signal received on the predetermined channel, the processor stops the first communication device;
The communication terminal according to claim 2 or 3, wherein A communication device configured to be able to transmit and receive signals in a first frequency band corresponding to the first communication method;
A predetermined signal is transmitted on a predetermined channel which is a channel in a second frequency band corresponding to the second communication method and assigned to notify the existence of a service area corresponding to the first communication method. A sending device to send, and
A base station comprising: The transmission power value of the predetermined signal by the transmission device is not less than the maximum transmission power value of the communication device,
The base station according to claim 5. A processor that generates a notification signal indicating the presence of a service area corresponding to the first communication method in the area of the device;
A communication device that transmits the notification signal in a second frequency band corresponding to a second communication method;
A base station comprising:

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