JP2004135346A - Bidirectional communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bidirectional communication system capable of transmitting mass data at a high speed with an information terminal which particularly emphasizes portability. <P>SOLUTION: An information terminal 1 sends low volume data such as a command to a Web server 6 on the Internet 5 to an asymmetric router 4 through a bidirectional radio network 2. The router 4 sends the command to the server 6 through the Internet 5 and also sends mass data from the server 6 (e.g., HTML browser data) to a data superposition broadcasting device 3. The device 3 predetermines transmission time based on the volume of the received data, and notifies the information terminal 1 through the network 2. When the predetermined time comes, the device 3 broadcasts the mass data by superposing on a free area of a television signal. The terminal 1 activates a broadcasting receiving part when the predetermined time comes, receives the television signal superposed with the mass data, and performs a fixed processing such as displaying the received data on the display part. <P>COPYRIGHT: (C)2004,JPO

Description

<< The present invention relates to a two-way communication system for exchanging data at a high speed using an existing communication system.

In recent years, the Internet using general analog telephone lines or digital dedicated lines has been known as a two-way communication system. On the Internet, you can browse (browse) HTML (Hypertext Markup Language) format data (documents consisting of images, sounds, and characters) and receive large amounts of large amounts of data stored on servers distributed around the world. It is possible to do. In addition, there is a normal television broadcast that provides video and audio to a user in one direction in a plurality of channels, not two-way communication. In the television broadcasting, character information (text broadcasting) is transmitted on a plurality of channels using a vacant area of a television signal, and the communication system can provide a large amount of information to a user.

In addition, as a two-way communication system for transmitting and receiving a larger amount of information between a plurality of users, a CATV (cable television) such as a VOD (Video On Demand) using a unique communication network is used. There is a two-way communication system in which two-way communication is enabled by installing an up line / down line.

However, in the above-described Internet, data can be transferred at a high speed when accessed by a fixed terminal such as a computer installed in a home or office. When an information terminal (mobile terminal) is used, the data transfer speed is the maximum at about 9.6 kbps because the information terminal (mobile terminal) is passed through a relay device (base station of a two-way communication network). For example, when the portable information terminal accesses a WWW (World Wide Web) server on the Internet and attempts to browse HTML format data (a document including images, sounds, and characters), 150 kbytes of data is received. In this case, it takes about 15 seconds, which is too slow to be practical.

地上 In addition, for terrestrial digital broadcasting that has been put into practical use in Europe as television broadcasting, mobile communication that enables a transmission speed of about 1 Mbps is added as one of its services. When the communication system is used, in the above example, data can be received in about 2 seconds. However, in the above-mentioned television broadcasting and the above-mentioned terrestrial digital broadcasting, no matter how high-speed data transmission is possible, there is a problem that only the user receives the data transmission and interactive two-way communication cannot be performed.

Further, in a two-way communication system using a dedicated line like the above-mentioned CATV, a user cannot receive a service at an arbitrary place (on a train, in a hall, a conference hall, etc.), and therefore receives a service only at a specific place. However, there is a problem that services cannot be obtained with portable information terminals.

Therefore, an object of the present invention is to provide a two-way communication system that can transmit large-capacity data at a high speed in an information terminal in which portability is particularly important.

To achieve the above object, a two-way communication system according to the first aspect of the present invention provides a two-way wireless network for wirelessly transmitting and receiving data bidirectionally, and a large-capacity data transmitting means for wirelessly transmitting large-capacity data in one direction. An asymmetric router that sends data from the two-way wireless network to an existing information providing network that provides large-capacity data while sending large-capacity data from the information providing network to the large-capacity data transmitting unit; An information terminal for transmitting and receiving bidirectional data from the bidirectional wireless network and receiving large data from the large data transmission means.

In a preferred embodiment, the two-way wireless network is a base for exchanging data bidirectionally with an information terminal existing in a corresponding service area for each predetermined service area. Stations may be arranged. Also, the large-capacity data transmitting means is usually a broadcasting station that broadcasts a predetermined television signal, and stores large-capacity data from the asymmetric router in an empty area of the television signal. It is also possible to provide a superimposing means for superimposing and broadcast a television signal on which a large amount of data is superimposed.

The information terminal may further include a bidirectional transmission / reception unit that transmits / receives data bidirectionally to / from the two-way wireless network, and a large-capacity data from the large-capacity data transmission unit. And a large-capacity receiving means for receiving.
Further, the asymmetric router selectively switches either the bidirectional wireless network or the large-capacity data transmission means as a communication path according to the amount of data to be transmitted. Is also good.
Also, the large-capacity data transmitting means may include, for example, a storage means for temporarily storing transmission data, and a scheduled transmission time calculating means for calculating a scheduled transmission time according to at least the transmission data amount. And transmitting means for transmitting the transmission data stored in the storage means when the scheduled transmission time calculated by the scheduled transmission time calculating means is reached.

Also, the large-capacity data transmitting means may include, for example, a storage means for temporarily storing transmission data, and a scheduled transmission time calculating means for calculating a scheduled transmission time according to at least the transmission data amount. A scheduled transmission time notifying unit for notifying the scheduled transmission time calculated by the scheduled transmission time calculating unit to the asymmetric router; and storing the scheduled transmission time calculated by the scheduled transmission time calculating unit in the storage unit. Transmitting means for transmitting the transmission data, the asymmetric router, the notifying means for notifying the information terminal via the two-way wireless network the scheduled transmission time notified from the scheduled transmission time notifying means, The information terminal includes a bidirectional transmitting / receiving means for transmitting and receiving bidirectional data from the bidirectional wireless network, and a large-capacity data from the large-capacity data transmitting means. A large-capacity receiving means for receiving data, the bidirectional transmitting / receiving means receives in advance the scheduled transmission time notified from the asymmetric router via the two-way wireless network, and when the scheduled transmission time comes, the The large-capacity receiving means may be activated.

Further, the large-capacity data transmitting means is plural, and is arranged for each predetermined area, and each of the large-capacity data transmitting means is provided with a large-capacity wireless communication in one direction with respect to the predetermined area. Transmitting information, the information terminal notifies the bidirectional wireless network of location information indicating a current location at a predetermined timing, and the asymmetric router temporarily stores the large-capacity data supplied from the information providing network. Storing means for storing, and selecting means for selecting a large-capacity data transmitting means in a corresponding area based on positional information of the information terminal supplied via the two-way wireless network, and selecting by the selecting means The large-capacity data transmitting means may transmit the large-capacity data from the information providing network.

In addition, the asymmetric router includes, for example, an encryption unit that performs predetermined encryption on large-volume data transmitted to the large-volume data transmission unit, and the information terminal includes the encryption unit. Decryption means may be provided for restoring encrypted large-volume data transmitted from the capacity data transmission means using the encryption key used for encryption in the asymmetric router.
Further, the information terminal may transmit an encryption key used for decryption by the decryption unit from the asymmetric router to the bidirectional wireless communication before receiving large-volume data. You may make it acquire via a network.
In addition, the two-way wireless network and the information terminal each include, for example, an encryption unit that performs predetermined encryption on data exchanged with each other, and an encrypted data, Decryption means for returning to the original state using the encryption key used in the encryption may be provided.

Further, the information providing network is, for example, the Internet to which a plurality of servers for providing files in an HTML format are connected, and the asymmetric router is connected to the Internet via the two-way wireless network. In accordance with a command supplied from an information terminal, there is provided a browsing unit for browsing an HTML file provided by a predetermined server on the Internet, wherein the browsing unit transmits the HTML file transmitted by the Internet in response to a command. Is converted into a display format on the information terminal, and then supplied to the large-capacity data transmitting means, wherein the information terminal includes display means for displaying data in a display format from the large-capacity data transmitting means. You may.

Further, the large-capacity data transmitting means is plural in number and is arranged for each predetermined area, and each of the large-capacity data transmitting means is provided with a large-capacity one-way radio communication for the predetermined area. While transmitting data, transmitting wireless network information indicating a two-way wireless network available to the information terminal in each region, the information terminal performs both based on the wireless network information from the large-capacity data transmitting means. A two-way wireless network used for two-way communication may be selected.

Further, the large-capacity data transmitting means assigns, to the large-capacity data supplied from the asymmetric router, an identification code for specifying the information terminal to receive the large-capacity data, for example, as described in claim 14. The information terminal transmits whether the identification code assigned to the large-capacity data matches an identification code set in advance for itself before receiving the large-capacity data from the large-capacity data transmission means. It is also possible to receive the large-capacity data only when it is determined that they match.

Further, the information terminal notifies the two-way wireless network of location information indicating a current location at a predetermined timing, and the asymmetric router communicates with the two-way wireless network via the two-way wireless network. And transmitting the position information of the information terminal supplied to the large-capacity data transmitting means to the large-capacity data transmitting means, wherein the large-capacity data transmitting means comprises a plurality of transmitting antennas having different directivities. A large amount of data may be transmitted from a transmission antenna according to the information.

According to the present invention, the following effects can be obtained.
(1) An information terminal capable of two-way communication can transmit large-capacity data and large-capacity data when the amount of information to be transferred is asymmetric and different between uplink and downlink, particularly when the amount of information in downlink is large. Since transmission is performed from a large-capacity data transmitting unit, efficient transmission can be performed by making use of the high-speed performance of the large-capacity data transmitting unit, and the load on the bidirectional wireless network can be reduced.
(2) The bidirectional wireless network is a wireless network in which base stations that exchange data bidirectionally with information terminals existing in corresponding service areas are arranged for each predetermined service area. As the two-way wireless network, for example, an existing PHS or cellular (cellular phone) can be used.

(3) Since the large-capacity data is usually superimposed on the vacant area of the television signal to be broadcasted and broadcast, an ordinary television broadcasting station can be used as the large-capacity data transmission means.
(4) Since the large-capacity data transmitting means temporarily stores the large-capacity data to be transmitted in the memory, the scheduled transmission time can be set from the data amount of the large-capacity data, so that the transmission schedule is determined. Further, by notifying the information terminal of the above-mentioned scheduled transmission time, the information terminal may operate the large-capacity receiving means only during a time period in which the large-capacity data is transmitted, thereby reducing power consumption.

(5) Since an appropriate large-capacity data transmission means is selected from a plurality of information terminals based on the current position of the information terminal, radio resources can be effectively used.
(6) Data transmitted between the information terminal and the two-way wireless network and data transmitted from the large-capacity data transmission means to the information terminal are subjected to predetermined encryption, thereby preventing information leakage. In addition, since only the specific information terminal that has obtained the encryption key for decryption can receive the data, it is possible to provide, for example, a paid service that requires charging management.

(7) Assuming that a server on the Internet is used as the information providing means, a browsing means for browsing information (large-volume data) on the server is provided in the asymmetric router, and the information terminal transmits a command or the like. In addition, since only the processing of displaying data in the display format is executed, the load on the memory capacity and processing speed of the information terminal can be reduced, the circuit scale can be reduced, and the portability can be reduced without compromising portability. Environment can be provided.
(8) Since the large-capacity data transmitting means transmits the radio network information indicating the available two-way radio network in the corresponding service area, the information terminal can use a different service area (two-way radio network or large-capacity radio network). (Data transmission means), an appropriate system can be selected and the system can be moved over a wide range.

(9) Since the large-capacity data transmitted by the large-capacity data transmitting means is provided with an identification code for identifying the information terminal, the information terminal can receive only the large-capacity data intended for itself. Thus, leakage of information can be prevented and paid services can be realized.
(10) A plurality of directional antennas having directivities in different directions are provided in the large-capacity data transmitting means, and the information terminal transmits the large-capacity data to the large-capacity data transmitting means at a predetermined timing via a bidirectional wireless network and an asymmetric router. Since the position information indicating the current position is notified, a large amount of data can be transmitted to a plurality of information terminals at the same time and at the same frequency, and effective use of radio wave resources and improvement of transmission efficiency can be achieved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as an embodiment applied to the Internet and a value-added communication network (VAN).

(First embodiment)
A. Configuration A-1 of First Embodiment FIG. 1 is a block diagram showing a configuration of a two-way communication system according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes an information terminal carried by a user, which includes a key input unit (not shown) for inputting an instruction from the user, a display unit for displaying various data (images, characters, and the like), and the like. A transmission / reception function for transmitting / receiving data to / from a two-way communication network 2 described later, and a broadcast reception function for receiving data from a data superimposition broadcasting device 3 described later. The information terminal 1 performs a normal two-way communication with the two-way wireless network 2 to add a value added to a server 6 on the Internet 5 or a fixed network 7 to be described later via the two-way wireless network 2. It transmits and receives data (small capacity) such as commands to and from the network 8 and receives data (large capacity) from the server 6 on the Internet 5 and the value-added network 8 on the fixed network 7 via the data superimposition broadcasting device 3. I do.

The two-way wireless network 2 is a wireless network capable of wireless two-way communication with the information terminal 1, and can be covered by a wireless signal of a predetermined output level, such as a communication network such as a mobile phone or a PHS. This is a communication network composed of base stations installed in each area. The two-way wireless network 2 supplies small-capacity data wirelessly received from the information terminal 1 to an asymmetric router 4 described later, and transmits small-capacity data from the asymmetric router 4 to the information terminal 1 by wireless.

The data superimposition broadcasting device 3 is a device for superimposing predetermined large-capacity data from the asymmetric router 4 on a normal broadcast signal and transmitting the data only in one direction (transmission), for example, a television signal of a predetermined channel. Is a television broadcasting station that superimposes a large amount of data supplied from the asymmetric router 4 on the television signal like a text broadcast and broadcasts it from a broadcast tower (antenna) (not shown). The data superimposed broadcasting device 3 may be a normal analog television broadcasting station or a digital television broadcasting station adopted in Europe as described above.

The asymmetric router 4 transfers the small amount of data supplied from the two-way wireless network 2 via a predetermined server 6 on the Internet (dedicated line or analog line) 5 and a fixed network (dedicated line or analog line) 7 which will be described later. While supplying the data to the value-added communication network 8, the large-capacity data supplied from the server 6 on the Internet 5 and the value-added communication network 8 on the fixed network 7 is supplied to the data superimposed broadcasting device 3.

The Internet 5 is a communication network connecting computers (servers) of various organizations and individuals around the world, and is directly connected to the asymmetric router 4 or via a provider via a dedicated line or ordinary analog. Connected via a line. The server 6 is a WWW (World Wide Web) server (hereinafter, referred to as a Web server) that provides HTML format data (a document composed of images, sounds, and characters), and a server that provides various news and data. The fixed network 7 is a dedicated line or a normal analog line to which a value-added communication network 8 for providing various information is connected, and is directly connected to the asymmetric router 4.

A-2. FIG. 2 is a block diagram showing a schematic configuration of the data superimposed broadcasting device 3 described above. In the figure, a data superimposing broadcast device 3 superimposes a large volume of data from an asymmetric router 4 temporarily on a memory 3a and superimposes the large volume of data stored in the memory on a television signal at a predetermined timing (scheduled transmission time). And a superimposing device 3b for transmission. Upon receiving a transmission request from the asymmetric router 4, the data superimposition broadcasting device 3 notifies the asymmetric router 4 of the available channel, temporarily stores the received large-capacity data in the memory 3a, and, in accordance with the data amount and the transmission request. The transmission scheduled time at which the large-capacity data is transmitted to the information terminal 1 is determined. Thereafter, the scheduled transmission time is returned to the asymmetric router 4, and when the scheduled transmission time is reached, the large-volume data stored in the memory 3a is superimposed on the television signal by the superimposing device 3b and transmitted.

In order to determine the scheduled transmission time, for example, it is desirable to use a FIFO method for transmitting data in order from the first received data or a method for determining the transmission order by combining priority with the FIFO method. Further, when a broadcast is scheduled in advance, the scheduled transmission time may be determined avoiding this. In addition, the data stored in the memory 3a is retained as it is after transmission in preparation for retransmission, and is deleted when an ACK signal obtained from the information terminal 1 via the asymmetric router 4 is received or when a certain time has elapsed. You.

A-3. Information Terminal Next, FIG. 3 is a block diagram showing a schematic configuration of the information terminal described above. In the figure, an information terminal 1 has a bidirectional transmitting / receiving unit 1a for transmitting / receiving data to / from a bidirectional wireless network 2, and a broadcast receiving unit 1b for receiving a television signal from the data superimposed broadcasting device 3, The reception preparation and data selection can be performed based on the scheduled transmission time notified via the wireless communication network 2. The broadcast receiving unit 1b is in a sleep state for reducing power consumption in a time zone other than the receiving operation, and is activated by the control unit 1f based on the time measured by the timer 1, and the television signal on which the large-capacity data is superimposed. Operation. Further, the activation control may include a function of designating a reception frequency (channel).

The data selector 1c selects data received by either the two-way wireless network 2 or the data superimposed broadcasting device 3 under the control of the controller 1f, and supplies the selected data to the processing device 1d. The processing device 1d processes the supplied data, converts the data into a predetermined display format, and displays the data on the display unit 1h.

The timer 1e measures the current time based on a system clock (not shown) and supplies the current time to the control unit 1f. The control unit 1f controls the above-described units, compares the current time with the scheduled transmission time received via the two-way wireless network 2, and, when the scheduled transmission time is reached, broadcast reception as described above. Activate the unit 1b to receive the television signal on which the large-volume data transmitted from the data superimposition broadcasting device 3 is superimposed.

The key input unit 1g is a keyboard for accessing the Internet 5, accessing the value-added network 8, and giving various instructions to the control unit 1f. The display unit 1h includes, for example, a liquid crystal display or the like, and displays a homepage on the Internet 5 and information on a value-added network. Note that a display device such as a CRT may be externally connected as the display unit 1h.

A-4. Layer Configuration of Information Terminal FIG. 4 is a conceptual diagram showing a layer configuration of the information terminal described above. In the figure, an information terminal 1 has a physical layer 10, a data link layer 11, and a network layer 12 for a two-way wireless network 2, a physical layer 13, a data link layer 14, and a network layer 12 and data for superimposed data broadcasting. An asymmetric routing layer 15 is provided above the link layer 14, and an application layer 16 is provided further above. For example, in the case of accessing the Internet 5, the application layer 16 is a Web browser (software). Since the routing (switching) between the two-way wireless network 2 and the data superimposed broadcast 3 is performed by the asymmetric routing layer 15, the application 16 can be made aware of a plurality of receiving means when selecting a receiving unit. Absent.

B. First, the basic operation (part) of the above-described asymmetric router, data superimposed broadcasting device, and information terminal will be described. Here, FIGS. 5 to 7 are flowcharts showing basic operations (parts) of the asymmetric router, the data superimposition broadcasting device and the information terminal, respectively.

B-1. Asymmetric Router First, a procedure for selecting a downlink communication path in an asymmetric router will be described with reference to FIG. When receiving the data (large capacity or small capacity), the asymmetric router 4 calculates the capacity of the received data in step S10, and determines in step S12 whether the total capacity of the data is larger than a preset specified value. Judge. The specified value is a threshold value that determines whether data to be transmitted to the information terminal 1 is transmitted by the data superimposition broadcasting device 3 or the two-way wireless network 2. The comparison judgment is that the data is large. In the case of a capacity, it is more efficient to transmit from the data superimposition broadcasting device 3 having a relatively high data transmission rate, and in the case of a small capacity of data, a relatively low data transmission rate is provided. Since it is more efficient to transmit via the two-way wireless network 2, this is a process for determining which to transmit. Then, if the total capacity of the data is equal to or less than the specified value, the process proceeds to step S14, and the data is transmitted to the information terminal 1 via the two-way wireless network 2.

On the other hand, if the total data capacity is larger than the specified value, the process proceeds to step S16. In step S16, a transmission request is transmitted to the data superimposition broadcasting device 3, and in step S18, it is determined whether transmission is possible based on a response from the data superimposition broadcasting device 3. As a transmission request, for example, a request is made as to where to allocate a channel to which data is to be transmitted. As a response from the data superimposition broadcasting device 3, if transmission is possible, the channel to be transmitted is returned. If the transmission is not possible, the process proceeds to step S14, and the data is transmitted to the information terminal 1 via the two-way wireless network 2.

On the other hand, if transmission is possible, the process proceeds to step S20, and the data is transmitted to the data superimposition broadcasting device 3. When receiving the data, the data superimposition broadcast device 3 calculates the scheduled transmission time according to the data capacity and returns the same to the asymmetric router 4 as described later. The asymmetric router 4 receives the scheduled transmission time in step S22, and notifies the information terminal 1 of the transmission channel and the scheduled transmission time via the two-way wireless network 2 in step S24.

Then, in step S26, the process waits for an ACK signal indicating completion of the reception of the data from the information terminal 1 to be supplied via the two-way wireless network 2. Then, when the ACK signal is supplied, the received ACK signal is transmitted to the data superimposition broadcasting device 3 in step S28, and the process is terminated.

B-2. Data superimposed broadcasting apparatus Next, a downlink broadcasting procedure in the data superimposed broadcasting apparatus will be described with reference to FIG. Upon receiving the data from the asymmetric router 4, the data superimposition broadcasting device 3 temporarily stores the data in the memory 3a in step S30. Next, in step S32, the received data capacity is calculated, and in step S34, the scheduled transmission time is calculated based on the obtained data capacity. Then, the transmission time is notified to the asymmetric router 4.

Next, in step S38, it is determined whether or not the scheduled transmission time has been reached. If the scheduled transmission time has not been reached, step S38 is repeated and the process stands by. On the other hand, when the scheduled transmission time comes, the process proceeds to step S40, in which the data accumulated in the memory 3a in step S30 is superimposed on a free area of a normal television signal and broadcast. Then, in a step S42, it is determined whether or not the ACK signal from the asymmetric router 4 is received. The ACK signal is a confirmation signal transmitted to the asymmetric router 4 by the information terminal that has received the television signal on which the data is superimposed, indicating that all data has been received. It is transmitted to the broadcasting device 3.

If the ACK signal has not been received from the asymmetric router 4, the process proceeds to step S44, and it is determined whether a timeout has occurred. Here, if it is not time-out, the process returns to step S42 and waits until an ACK signal is received. On the other hand, if the ACK signal cannot be received and the timeout occurs after the data is superimposed and broadcast, the process proceeds to step S46, and the information terminal 1 notifies the asymmetric router 4 that the information terminal 1 has not received the data. Provide notifications.

On the other hand, when the ACK signal is received from the information terminal 1 via the asymmetric router 4 in step S42 after the data is superimposed and broadcast, it is determined that the data has been received by the information terminal 1, and the process proceeds to step S48, where the broadcasted data Is deleted from the memory 3a, and then the process is terminated.

B-3. Information Terminal Next, a procedure for selecting a reception path in the information terminal will be described with reference to FIG. First, in step S50, the information terminal 1 determines whether the planned communication path is the two-way wireless network 2 or the data superimposed broadcast 3. If the planned communication path is the two-way wireless network 2, the process proceeds to step S52, where the two-way transmitting / receiving unit (receiving unit) 1a, which is a receiving function of the two-way wireless network 2, is selected and activated, and step S54 is performed. , Small-capacity data from the two-way wireless network 2 is received.

On the other hand, when the scheduled communication path is the data superimposed broadcast 3, the process proceeds to step S56, where the broadcast receiving unit 1b, which is a function of receiving the data superimposed broadcast, is selected. Set the scheduled broadcast channel. Next, in step S60, it is determined whether or not the scheduled transmission time notified from the asymmetric router 4 has been reached similarly by referring to the current time by the timer 1e. Execute repeatedly and wait. On the other hand, when the scheduled transmission time is reached, the process proceeds to step S62, where the sleep of the broadcast receiving unit 1b is released, and in step S64, the television signal on which the data is superimposed from the data superimposition broadcasting device 3 is received.

When the reception of the data superimposed on the television signal is completed, the broadcast receiving unit 1b is returned to the sleep state in step S66, and an ACK signal indicating the completion of the data reception is transmitted via the bidirectional wireless network 2 in step S68. After notifying the asymmetric router 4, the process ends.

B-4. Next, the overall operation of the first embodiment will be described. Here, FIG. 8 is a sequence for explaining the operation of the two-way communication system according to the first embodiment. When a connection request is issued from a Web browser to a Web server 6 on the Internet 5, the information terminal 1 transmits a command CMD to the asymmetric router 4 via the two-way wireless network 2. The asymmetric router 4 sends the command CMD to the Web server 6 via the Internet 5. Accordingly, the Web server 6 transmits, for example, browser data (HTML format file) D1 to the asymmetric router 4 via the Internet 5 according to the received command CMD.

Next, the asymmetric router 4 should transmit the browser data D1 to the data superimposition broadcasting device 3 when the data amount of the browser data D1 transmitted from the Web server 6 exceeds a predetermined amount. Send a channel request CRQ. On the other hand, the data superimposition broadcasting device 3 returns an empty channel and an ACK signal to the asymmetric router 4. Upon receiving the ACK signal, the asymmetric router 4 transmits the browser data D1 to the data superimposed broadcasting device 3. Upon receiving the browser data D1, the data superimposition broadcasting device 3 calculates a scheduled transmission time based on the data capacity, and notifies the asymmetric router 4 of the scheduled transmission time as a time tag TT.

(4) Upon receiving the time tag TT, the asymmetric router 4 transmits the previously received transmission channel C and the time tag TT to the information terminal 1 via the two-way wireless network 2. The information terminal 1 receives the transmission channel C and the time tag TT by the bidirectional transmission / reception unit 1a, and waits until a television signal on which the browser data D1 is superimposed is transmitted according to the time tag TT.

On the other hand, at the scheduled transmission time, the data superimposition broadcasting device 3 superimposes the browser data D1 on the television signal of the transmission channel C set previously by the superimposition device 3b and transmits the TV signal. Similarly, when the scheduled transmission time comes, the information terminal 1 activates the broadcast receiving unit 1b, and the activated broadcast receiving unit 1b receives the television signal on which the browser data D1 is superimposed, and The browser data D1 is extracted, data in a display format is generated, and displayed on the display unit 1h. Further, the information terminal 1 sends an ACK signal indicating completion of reception of the browser data D1 to the bidirectional transmitting / receiving unit 1a, and the bidirectional transmitting / receiving unit 1a sends the ACK signal to the asymmetric router 4 via the bidirectional wireless network 2. Send. Upon receiving the ACK signal, the asymmetric router 4 notifies the data superimposition broadcasting device 3 of the ACK signal. On the other hand, the data superimposition broadcasting device 3 deletes the browser data D1 stored in the memory 3a.

As described above, in the above-described first embodiment, an upstream data stream (a small amount of data such as a command) as viewed from the information terminal 1 is transmitted via the bidirectional communication network 2 having a relatively low data transmission speed. On the other hand, a data stream in the downstream direction (large-capacity data such as browser data) as viewed from the information terminal 1 is transmitted by the data superimposition broadcasting device 3 having a relatively high data transmission speed, so that the data transmission speed is relatively low. Data can be transmitted at high speed while reducing the load on the two-way wireless network 2.

(Second embodiment)
Next, a second embodiment of the present invention will be described. In the second embodiment, of the plurality of data superimposed broadcasting devices, a data superimposed broadcasting device in which the current position of the information terminal 1 is a service area (a radio wave arrival area) is selected, and large-capacity data is transmitted from the data superimposed broadcasting device. The superimposed television signal is transmitted. When the data capacity to be transmitted exceeds the broadcastable capacity of the data superimposed broadcasting device 3, large-capacity data is transmitted via the two-way wireless network 2. Hereinafter, the configuration and operation of the second embodiment will be described.

Here, FIG. 9 is a block diagram showing the configuration of the two-way communication system according to the second embodiment of the present invention. The parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 9, the asymmetric router 20 includes a memory 20a for temporarily storing a large amount of data received via the Internet 5 or the fixed network 7. The large-capacity data is usually supplied to one of the data superimposed broadcasting devices 3-1, 3-2,..., 3-n, and the information superimposed broadcasting device 3-i (i = 1 to n) 1 is sent. However, if the data capacity to be transmitted exceeds the broadcastable capacity of the data superimposed broadcasting device 3-i to be transmitted, large-capacity data must be transmitted via the two-way wireless network 2. Since the two-way wireless network 2 has a relatively low data transmission speed, it is necessary to temporarily hold a large amount of data. The memory 20a of the asymmetric router 20 is used for transmitting data via the two-way radio network 2 when the data cannot be transmitted by the data superimposition broadcasting device 3-i.

Each of the data superimposing broadcasting devices 3-1 to 3-n is provided for each range in which a broadcast wave of a predetermined output can reach. Is superimposed on a television signal and broadcast. The current position of the information terminal 1 is obtained by an asymmetric router via a base station installed for each predetermined area in the two-way wireless network 2, and the asymmetric router 20 controls the data superimposed broadcasting devices 3-1 to 3-n. Select which to supply the large amount of data to. Note that the correspondence between the current position of the information terminal 1, that is, the area obtained through the base station and in which the information terminal 1 is located and the data superimposed broadcasting apparatus 3 having the area as a service area is asymmetric in advance as a table. Be prepared for the router 20.

Next, the operation of the second embodiment will be described.
When the asymmetric router 20 receives a command for requesting a connection to the Web server 6 on the Internet 5 from the information terminal 1 via the two-way wireless network 2, the asymmetric router 20 sends the command to the Web server 6 via the Internet 5. . In addition, at this time, at the same time as receiving the command, position information indicating the current position of the information terminal 1 is acquired. Next, upon receiving large-volume data (browser data) transmitted from the Web server 6 on the Internet 5, the asymmetric router 20 temporarily stores the received browser data in the memory 20a.

Next, based on the position information of the information terminal 1, the asymmetric router 20 sends the browser / broadcast to the corresponding data superimposed broadcasting device 3-i among the plurality of data superimposed broadcasting devices 3-1 to 3-n. Request a channel to send data to. On the other hand, when the corresponding data superimposed broadcasting device 3-i can transmit, the browser data temporarily stored in the memory 20a is transmitted to the corresponding data superimposed broadcasting device in the same manner as in the first embodiment. Transmit to the device 3-i. Hereinafter, similarly to the above-described first embodiment, the data superimposition broadcasting device 3-i superimposes the browser data on the television signal and broadcasts it at a predetermined scheduled transmission time.

On the other hand, when the corresponding data superimposition broadcasting device 3-i cannot transmit, the asymmetric router 20 notifies the information terminal 1 that browser data is transmitted using the two-way wireless network 2, The browser data once stored in the memory 20a is transmitted to the information terminal 1 via the two-way wireless network 2. According to the notification from the asymmetric router 20, the information terminal 1 sets the reception path to the two-way wireless network 2 as shown in the above-described flowchart, and receives the browser data by the two-way transmission / reception unit 1a. The display data is generated from the browser data and displayed on the display unit 1h. When the asymmetric router 20 receives the ACK signal indicating the completion of the reception of the browser data from the information terminal 1, the asymmetric router 20 deletes the browser data in the memory 20a.

As described above, according to the above-described second embodiment, of the plurality of data superimposed broadcasting devices 3-1 to 3-n, only the data superimposed broadcasting device 3-i whose service area is the current position of the information terminal 1 is used. Since the large-volume data is superimposed on the television signal and broadcast (transmitted), the radio wave resources can be effectively used. If there is no transmittable data superimposed broadcasting device, large-capacity data is temporarily stored in a memory 20a provided in the asymmetric router 20, and the large-capacity data stored in the memory 20a is transmitted via the bidirectional wireless network 2. Therefore, even when the data superimposed broadcasting device is congested, large-capacity data can be received without waiting for a long time.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the third embodiment, in order to transfer data (small capacity and large capacity) only between specific information terminals, data is encrypted and transmitted and received. Here, FIG. 10 is a block diagram showing a configuration for implementing an encryption process for transmitting data only to a specific information terminal in the above-described two-way communication system. The parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 10, the authentication center 30 has an encryption key K2 unique to the asymmetric router 4 and supplies it to the asymmetric router 4. The asymmetric router 4 encrypts a large amount of data to be transmitted to the data superimposition broadcasting device 3 using the encryption key K2. Further, the asymmetric router 4 transmits the encryption key K2 to the information terminal 1 via the two-way wireless network 2 in response to a request from the information terminal 1.

The decryption / encryption scheme unit 31 has an encryption key K1 unique to the two-way wireless network 2 and supplies it to the two-way wireless network 2. The two-way wireless network 2 uses the encryption key K1 to encrypt and decrypt small-volume data between information terminals.

The information terminal 1 includes a decryption / encryption unit 1i for encrypting and decrypting a small amount of data exchanged with the two-way wireless network 2 using the encryption key K1. And a decryption unit 1j for decrypting a large amount of data from the asymmetric router using the encryption key K2 obtained from the asymmetric router 4 via the two-way wireless network 2.

Here, assuming that the two-way wireless network 2 encrypted with the encryption key K1, which is a secure path, can be used as the encryption method used in the authentication center 30, "One Time Pad encryption using a time tag or the like" is used. It is preferable to use the "method". In the “One Time Pad encryption method”, an encryption key for encryption / decryption is generated every time, and the encryption key is used only once, and the same encryption key is not repeatedly used. That is, each time data that needs to be encrypted is generated, an encryption key K2 is generated, the data superimposed broadcast is encrypted using the encryption key K2, and then the information terminal 1 is transmitted to the information terminal 1 via the two-way wireless network 2. It is transferred and the encryption key K2 of that value is never used again.

As described above, in the third embodiment, between the asymmetric router 4 and the data superimposed broadcasting device 3, between the two-way radio network 2 and the information terminal 1, and between the data superimposed broadcasting device 3 and the information terminal 1. By encrypting the data to be transmitted and received, data transmission can be performed safely, and only the information terminal 1 authorized in advance can receive, so that, for example, charging management for each information terminal can be realized, It is very effective in service operation.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, a configuration for reducing the load on the information terminal is provided. In general, for example, when considering accessing the Web server 6 on the Internet 5, a general personal computer (or a terminal that accesses the Internet in a broad sense) may use, for example, an OS environment such as Windows (registered trademark). By executing a Web browser. However, in this case, a sufficient memory capacity and a high processing speed are required, which leads to an increase in the cost of the terminal, a complicated and large-scale circuit configuration, and a loss of portability.

Here, FIG. 11 is a block diagram showing a configuration of a terminal such as a conventional personal computer. In the figure, an input / output device 40 is a display (liquid crystal or the like) or a mouse keyboard (a cursor key or a trackball provided on a housing is also possible), and is controlled by a mouse driver 41 and a display driver 42 on the OS. You. The Web browser 43 is application software that operates under the OS, generates data in a display format from the browser data, displays the data on a display unit by the display driver 42, and operates the mouse by the user by the mouse driver 41. / Accept input from keyboard.

When accessing the Internet 5, the Web browser 43 sends to the communication driver 44 a designation (command) of a browsing page and an instruction (command) of downloading a program allocated to the page. The communication driver 44 is software on the OS, controls a modem (or an Ethernet (registered trademark) card, etc.) 45 and transmits the command to the Internet 5. At this time, the connection to the Internet 5 may be through a firewall 46 such as a proxy server. Note that the firewall 46 is software for security that prevents intrusion (access) into the information terminal 1 from outside. As described above, in the information terminal having the conventional configuration, a large-capacity software such as a Web browser must be started in addition to the OS, so that it is difficult to realize a comfortable environment due to limitations in memory capacity and processing speed. .

Therefore, in the fourth embodiment, the processing of the Web browser is performed by the asymmetric router 4, and the information terminal 1 performs only the input / output processing. Hereinafter, the fourth embodiment will be described in detail. Here, FIG. 12 is a block diagram showing a schematic configuration of an information terminal and an asymmetric router according to the fourth embodiment. Note that the same reference numerals are given to portions corresponding to FIG. 3 and description thereof is omitted.

First, in the information terminal 1, the display unit 1h shown in FIG. 12 is a display device composed of a liquid crystal display or the like, as described above, and displays data (large-capacity data) supplied via the input / output driver 52. : Browser data, small volume data: command) are displayed. The touch screen sensor 50 is a sensor that detects that the user has touched the screen of the display unit 1h, and sends the touched position to the quick pointer 51. The quick pointer 51 acquires which position on the display screen has been touched based on the touch position from the touch screen sensor 50 and the display screen information of the display unit 1h (position information), and the input / output driver 52 Through the communication driver 53.

The communication driver 53 supplies the position information as a command to the bidirectional transmitting / receiving unit 1a. Note that the communication driver 53 may supply the ID number 55 for identifying the information terminal 1 to the two-way transmitting / receiving unit 1a as necessary. Next, the communication / port selector 54 outputs the small-capacity data from the two-way wireless network 2 supplied via the two-way transmission / reception unit 1a or the large-capacity data (from the data superimposed broadcasting device 3 received by the broadcast reception unit 1b). Browser data) is selectively switched and supplied to the display unit 1h via the input / output driver 52.

Next, in the asymmetric router 4, the input / output / ID driver 56 shown in FIG. 12 receives the data and the ID number transmitted from the information terminal 1 via the two-way wireless network 2, and the ID number and the Internet address With reference to a correspondence table 57 stored in association with the above, the data is passed to the Web browser 58, and the large-volume data (browser data, etc.) received by the Web browser 58 is transmitted to the data superimposition broadcasting device 3. As described above, the Web browser 58 is software for accessing the Internet 5, and accesses a predetermined server 6 on the Internet 5 according to data from the input / output ID driver 56. Further, the connection to the Internet 5 may be made via a firewall 59 such as a proxy server as in the related art.

As described above, in the fourth embodiment, the asymmetric router 4 is provided with software for accessing the Internet 5, and the information terminal 1 is provided with only software for input / output processing. 1 can reduce the load on the memory capacity and processing speed, and can be used in a comfortable environment. Therefore, the server 6 on the Internet 5 can be accessed by the inexpensive and lightweight information terminal 1. Further, even an information terminal having no Internet 5 address can access the server 6 on the Internet 5.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, the two-way wireless network 2 is, for example, one capable of providing service in a predetermined area such as PHS, one capable of providing service in almost all areas such as Celera (mobile phone), or the like. A plurality of two-way wireless networks can be used, and an available two-way wireless network can be selected according to the current position of the mobile information terminal 1.

For example, a two-way wireless network that has the same configuration as that of the above-described second embodiment and that can be used in a region corresponding to each television signal transmitted from a plurality of data superimposed broadcasting devices provided in each region is shown. When the information terminal 1 moves to another area while the radio network identification data is superimposed and broadcast, by confirming the radio network identification data superimposed on the television signal received at the moved location, the current area Select an available two-way wireless network.

Further, when the information terminal 1 moves, the fact that the television signal can be received at the place where the information terminal 1 has moved is notified to the asymmetric router 4 via the bidirectional wireless network 2 available at the place. You may make it notify. Thereby, the asymmetric router 4 can bidirectionally exchange data with the information terminal 1 via the notified two-way wireless network 2.

Alternatively, the above two methods are combined, and the radio network identification data indicating the two-way radio network 2 available in the corresponding area is superimposed on each television signal transmitted from the data superimposition broadcasting device (plural), and broadcast. The asymmetric router is notified that the moved information terminal 1 is ready to receive the television signal via the two-way wireless network 2 indicated by the wireless network identification data broadcast superimposed on the television signal. It may be.

As described above, in the fifth embodiment, even when the information terminal 1 moves and moves to a different service area of the two-way wireless network 2 and the data superimposed broadcasting device 3 than before, the current Since an appropriate two-way wireless network 2 can be selected according to the position, it can cope with a wide range of movement.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. In the sixth embodiment, a data format broadcast by the data superimposition broadcasting device 3 is configured as shown in FIG. 13 to provide more detailed services. In FIG. 13, the frame length 60 includes a preamble / time marker 70, a signal distribution code 71, data 80 for individual users, data 90 for group users, and public data 100.

The frame length 60 is variable, and the length of each data can be set flexibly. However, in order to reduce power consumption, a periodic time marker is provided, and a flexible frame configuration is realized based on the time marker. The signal distribution code 71 specifies the distribution of the lengths of the data 80 addressed to the individual users, the data 90 addressed to the group users, and the public data 100, and is encoded and added.

(4) The data 80 addressed to an individual user is encrypted so that a specific individual can decrypt only with a key based on the individual ID of the individual. The details of the encryption have been described in the third embodiment. The group user data 90 is encrypted so that it can be decrypted only with a key based on the group ID of the common group, and has a preamble 90a at the beginning. The public data 100 is not encrypted so that an unspecified number of recipients (information terminals) can freely receive the public data 100, and has a preamble 100 a at the head, similarly to the group user data 90.

The personal ID and the group ID may be different from each other, or may be such that the group ID is embedded in a predetermined position of the personal ID. In the embedded format, for example, the format of the ID may be “AAAABBB”, the first half “AAAAA” may be used as a personal ID for identifying an individual, and the second half “BB” may be used as a group ID for identifying a group. Conceivable.

As described above, in the sixth embodiment, the data to be transmitted by being superimposed on the television signal from the data superimposition broadcasting device 3 is converted into the data format including the data 80 addressed to the individual users, the data 90 addressed to the group users, and the public data 100. By doing so, the broadcast target user can be set flexibly. Also, the data 80 for individual users and the data 90 for group users are encrypted so that only the intended user can decrypt them, thereby preventing information leakage. Also, by attaching the time marker 70, the information terminal 1 starts reception in accordance with the reception timing. Otherwise, by putting the information terminal 1 in a sleep state, power consumption can be reduced.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described. In the seventh embodiment, by using a plurality of directional antennas oriented in different directions in the data superimposition broadcasting device 3, specific users (plurality) can be selectively and simultaneously used by radio waves of the same frequency. , For transmitting data addressed to each user. As described in the sixth embodiment, in transmitting data addressed to an individual user, since communication with a specific individual user is performed via the two-way wireless network 2, the service area corresponding to the base station number is set. By knowing, the position of the individual user can be specified.

Therefore, when large-capacity data is to be transmitted to a plurality of individual users at the same time, by using a plurality of directional antennas directed to different directions in the data superimposition broadcasting device 3, the CIR is sufficiently increased due to the directivity of the antenna. If the plurality of individual users are sufficiently separated in a direction that can be secured in the same manner, different data corresponding to the respective users can be simultaneously transmitted at the same frequency.

Here, FIG. 14 is a conceptual diagram for explaining the operation when the directional antenna according to the seventh embodiment is used. In the figure, Z is a service area of broadcasting by the data superimposition broadcasting device 3, and A, B, and C are service areas of one base station of the two-way wireless network 2, respectively. That is, a plurality of base stations exist in the service area Z of the broadcast by one data superimposed broadcasting device 3, and the two or more base stations constitute the two-way wireless network 2. Note that a plurality of base stations of the two-way wireless network 2 may overlap service areas provided by different data superimposed broadcasting devices 3. 110, 111, 112, 113, and 114 are directivity boundaries of the directional antennas of the data superimposition broadcasting device 3, respectively.

In the service area A, a personal user who tries to access the Web server 6 on the Internet 5 may have a directivity direction overlapping with that of an individual user accessing in the service area B. Is difficult to secure, but separation from individual users in the service area C with sufficient directivity is possible. In this case, the individual users of the service area A and the individual users of the service area C are transmitted at the same frequency and at the same time from the antennas corresponding to the respective service areas to the individual users of the service area A. The individual user and the individual user in the service area C can simultaneously receive data corresponding to each.

On the other hand, when data is transmitted only to the individual users in the service area A, the use of the directional antenna limited by the directional boundaries 110 and 111 eliminates the need to transmit radio waves in other unnecessary directions. , Radio wave resources can be used effectively. Furthermore, since unnecessary radio waves are not output, interference between radio waves can be reduced.

In the above-described embodiment, only the browser data of the Internet 5 has been described. However, the present invention is not limited to this, and the same applies to the illustrated value-added communication network 8, for example, a TV learning system, news (selection of detailed items). , Advertisement (request for explanation), quiz / game (answer), and questionnaire survey. In addition, if encryption or a personal ID is used, an education system for a specific individual, home shopping, and the like can be performed.

1 is a block diagram illustrating a configuration of a bidirectional communication system according to an embodiment of the present invention. FIG. 1 is a block diagram illustrating a schematic configuration of a data superimposition broadcasting device according to an embodiment. It is a block diagram which shows the schematic structure of an information terminal. It is a conceptual diagram which shows the layer structure of an information terminal. 6 is a flowchart illustrating a basic operation (part) of an asymmetric router. 6 is a flowchart illustrating a basic operation (part) of the data superimposed broadcasting device. 6 is a flowchart illustrating a basic operation (part) of the information terminal. 5 is a sequence for explaining the operation of the two-way communication system according to the embodiment. FIG. 6 is a block diagram illustrating a configuration of a bidirectional communication system according to a second embodiment of the present invention. FIG. 13 is a block diagram showing a configuration for implementing an encryption process for transmitting data only to a specific information terminal according to a third embodiment of the present invention. It is a block diagram which shows the structure of the information terminal comprised by the conventional personal computer etc. FIG. 13 is a block diagram illustrating a schematic configuration of an information terminal and an asymmetric router according to a fourth embodiment of the present invention. FIG. 13 is a conceptual diagram showing a data format broadcast by a data superimposition broadcasting device 3 according to a sixth embodiment of the present invention. It is a conceptual diagram for explaining operation at the time of using the directional antenna by a 7th example of the present invention.

Explanation of reference numerals

1 information terminal 1a bidirectional transmission / reception unit (bidirectional transmission / reception means)
1b Broadcast receiver (Large-capacity receiving means)
1c Data selection unit 1d Processing unit 1e Timer 1f Control unit 1g Key input unit 1h Display unit 2 Bidirectional wireless network 3,3-1-3-n Data superimposed broadcasting device (large-capacity data transmission means)
3a memory (storage means)
3b Superposition device (superposition means)
4 Asymmetric router 5 Internet (information providing network)
6 Server 7 Fixed network 8 Value-added communication network (information providing network)
20 asymmetric router 20a memory 1j decoding unit (decoding means)
1i Decryption / encryption unit (encryption means, decryption means)
30 Authentication center (encryption means)
31 Decryption / encryption method section (encryption means, decryption means)
Reference Signs List 50 touch sensor 51 quick pointer 52 input / output driver 53 communication driver 54 communication port selector 55 ID number 56 input / output ID driver 57 table 58 Web browser (browsing means)
59 firewall 1h display unit (display means)

Claims (15)

A two-way wireless network that transmits and receives data in two directions wirelessly,
A large-capacity data transmitting means for transmitting large-capacity data in one direction by wireless;
An asymmetric router that sends data from the two-way wireless network to an existing information providing network that provides large-capacity data, while sending large-capacity data from the information providing network to the large-capacity data transmitting unit;
An information terminal for transmitting and receiving bidirectional data from the bidirectional wireless network and receiving large data from the large data transmission means. 2. The two-way wireless network according to claim 1, wherein a base station that exchanges data bidirectionally with an information terminal in a corresponding service area is arranged for each predetermined service area. Two-way communication system. The large-capacity data transmitting means is usually a broadcasting station that broadcasts a predetermined television signal, and includes superimposing means for superimposing large-capacity data from the asymmetric router on an empty area of the television signal. 2. The two-way communication system according to claim 1, wherein the superimposed television signal is broadcast. The information terminal includes: a bidirectional transmission / reception unit that transmits and receives data bidirectionally to and from the bidirectional wireless network; and a large-capacity reception unit that receives large-capacity data from the large-capacity data transmission unit. The two-way communication system according to claim 1, wherein: The two-way communication system according to claim 1, wherein the asymmetric router selectively switches either the two-way wireless network or the large-capacity data transmission means as a communication path according to the amount of data to be transmitted. . The large-capacity data transmitting unit is configured to temporarily store transmission data, at least according to the amount of transmission data, a scheduled transmission time calculating unit that calculates a scheduled transmission time, and to be calculated by the scheduled transmission time calculating unit. 2. The two-way communication system according to claim 1, further comprising a transmission unit that transmits the transmission data stored in the storage unit when the scheduled transmission time comes. The large-capacity data transmitting unit is configured to temporarily store transmission data, at least according to the amount of transmission data, a scheduled transmission time calculating unit that calculates a scheduled transmission time, and to be calculated by the scheduled transmission time calculating unit. A scheduled transmission time notifying unit that notifies the scheduled transmission time to the asymmetric router; and a transmission unit that transmits the transmission data stored in the storage unit when the scheduled transmission time calculated by the scheduled transmission time calculation unit is reached. ,
The asymmetric router includes a notifying unit that notifies the information terminal of the scheduled transmission time notified from the scheduled transmission time notifying unit via the two-way wireless network,
The information terminal includes a bidirectional transmission / reception unit that transmits and receives bidirectional data from the bidirectional wireless network, and a large-capacity reception unit that receives large-volume data from the large-capacity data transmission unit. 2. The large-capacity receiving unit according to claim 1, wherein the scheduled transmission time notified from the asymmetric router via the network is received in advance by the bidirectional transmitting / receiving unit, and when the scheduled transmission time comes, the large-capacity receiving unit is activated. Two-way communication system. A plurality of the large-capacity data transmitting means, each of which is arranged for each predetermined area, and each of which transmits large-capacity data in one direction by radio to the predetermined area;
The information terminal notifies the two-way wireless network of location information indicating a current location at a predetermined timing,
The asymmetric router is configured to temporarily store large-capacity data supplied from the information providing network, and based on location information of the information terminal supplied via the two-way wireless network, to determine a size of a corresponding area. 2. A large capacity data transmitting means, comprising: selecting means for selecting the large capacity data transmitting means, wherein the large capacity data from the information providing network is transmitted to the large capacity data transmitting means selected by the selecting means. Two-way communication system. The asymmetric router includes an encryption unit that performs predetermined encryption on large-volume data transmitted to the large-volume data transmission unit,
The information terminal further includes a decryption unit that restores the encrypted large-volume data transmitted from the large-volume data transmission unit using an encryption key used for encryption in the asymmetric router. The two-way communication system according to claim 1, wherein: The information terminal acquires an encryption key used for decryption by the decryption means from the asymmetric router via the two-way wireless network each time prior to receiving large-capacity data. The two-way communication system according to claim 9. The two-way wireless network and the information terminal each use encryption means for performing predetermined encryption on data to be exchanged with each other, and encrypt the encrypted data using an encryption key used for encryption. 2. The two-way communication system according to claim 1, further comprising: a decryption unit. The information providing network is the Internet to which a plurality of servers providing HTML format files are connected,
The asymmetric router includes a browsing unit for browsing an HTML file provided by a predetermined server on the Internet in accordance with a command supplied from the information terminal via the two-way wireless network. After converting the HTML format file transmitted by the Internet in response to a command into a display format on the information terminal, supplying the file to the large-capacity data transmission means;
The two-way communication system according to claim 1, wherein the information terminal includes a display unit that displays data in a display format from the large-capacity data transmission unit. A plurality of the large-capacity data transmission means are provided, each of which is arranged for each predetermined area. Each of the large-capacity data transmission means transmits the large-capacity data in one direction by radio to the predetermined area, and in each area, Transmitting wireless network information indicating a two-way wireless network available to the terminal;
2. The two-way communication system according to claim 1, wherein the information terminal selects a two-way wireless network to be used for two-way communication based on wireless network information from the large-capacity data transmitting means. The large-capacity data transmitting means, to the large-capacity data supplied from the asymmetric router, transmitting the large-capacity data with an identification code for identifying the information terminal to receive the large-capacity data,
Prior to receiving the large-capacity data from the large-capacity data transmitting means, the information terminal determines whether or not the identification code given to the large-capacity data matches an identification code set in advance for itself. 2. The two-way communication system according to claim 1, wherein the large-capacity data is received only when they match. The information terminal notifies the two-way wireless network of location information indicating a current location at a predetermined timing,
The asymmetric router transmits position information of the information terminal supplied through the two-way wireless network to the large-capacity data transmitting unit,
2. The large-capacity data transmitting means includes a plurality of transmission antennas having different directivities, and among the plurality of transmission antennas, transmits large-capacity data from a transmission antenna corresponding to the position information. A two-way communication system as described.

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