JP2005063234A - Portal server and cache server in content distribution system, and content distribution method and content distribution program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the access number and traffic from a fixed server to a content provider, and to improve the accuracy of communication and reduce a communication fee to be spent in acquiring information. <P>SOLUTION: A portal server 2 receives a content distribution request from an on-vehicle unit 1, retrieves the list of cache servers which owns the content by referring to a contents list, specifies the optimal cache server on the basis of the positional information of the on-vehicle unit 1 and the cache server, and instructs content distribution from the specified cache server. For example, a cache server 3 mounted on a public transportation facility selects the optimal communication media by determining the possibility of communication for each of communication media, and instructs, on the basis of instructions from the portal server 2, the distribution of the content through the selected communication media to the on-vehicle unit 1 which has made the request. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a portal server and a cache server, a content distribution method, and a content distribution program in a content distribution system.

Information services for individuals targeting in-vehicle users by installing in-vehicle computers, mobile phones, and personal digital assistants in vehicles, and introducing an agent system in the midst of the advancement of vehicle electronics such as car navigation Can now be provided.
Conventionally, when content is acquired from a mobile body such as a vehicle, an information request is issued to a fixed server (portal server) using a public mobile infrastructure, and information is distributed from the fixed server to the vehicle. (See Patent Document 1).
JP 2002-244947 A

  By the way, depending on the information to be distributed, there is information depending on the location, such as traffic information limited to the area, such as location and area, etc., but according to the above-described conventional technology, these information are not related to the location or area. All information is acquired from a fixed server. Therefore, if the access is concentrated on the fixed server, there is a disadvantage that the server and the network are burdened when the content is downloaded. Further, since there is only one fixed server, there is a limit in terms of reliability.

  Furthermore, in the communication from the in-vehicle terminal, the communication medium is currently limited to the public wireless line, and it is necessary to access a specific fixed server in order for vehicles located in front and back or in the vicinity to acquire the same content, A certain communication time and communication path are required for content acquisition. In addition, while the vehicle is running, communication may become impossible due to movement, and there is a guarantee that communication reliability is sufficient when sharing information and transmitting / receiving information between vehicles via a fixed server. There wasn't.

  The present invention has been made in view of the various circumstances described above, and by distributing the download sources of content depending on the position, the number of accesses from the fixed server to the content provider and the amount of communication are reduced. Portal server and cache in a content distribution system that improve communication reliability and reduce communication charges when acquiring information by constructing a mechanism that uses not only public wireless lines but also short-range wireless communication for communication media It is an object to provide a server, a content distribution method, and a content distribution program.

  In order to solve the above-described problems, the present invention temporarily stores a mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and content provided by the content server. A cache server to be stored is a portal server in a content distribution system connected via a communication medium of a public mobile line, a wired line, a public mobile line, or a short-range wireless communication line, and the mobile terminal And data storage means for storing the location information of the cache server and a list of contents owned for each cache server, and receiving a content distribution request from the mobile terminal, and searching for a list of cache servers that own the corresponding contents The mobile terminal and the cache server Identify optimum cache server based on the location information, characterized by comprising a cache server managing means for instructing the content delivery from the cache server that is the specific.

  According to the present invention, the cache server management unit receives the content distribution request from the mobile terminal, and owns the corresponding content by referring to the content list indicating the owned content list for each cache server in the data storage unit. By searching a list of cache servers, specifying an optimal cache server based on the location information of the mobile terminal and the cache server in the data storage means, and instructing content delivery from the specified cache server, It is possible to distribute the download sources of content depending on the position, thereby reducing the number of accesses and the amount of communication from the portal server to the content server as the content provider.

  In the present invention, when there is no cache server that owns the relevant content, the cache server management means acquires the relevant content from the content server and is located closest to the mobile terminal. It is characterized by instructing the accumulation to.

  In order to solve the above-described problems, the present invention manages each mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and the location of content requested by the mobile terminal. A cache server in a content distribution system connected via a communication medium of a public mobile line, a wired line, a public mobile line, or a near field communication line, and the portal server Receiving a content distribution request from the mobile terminal, obtaining a distribution instruction for the content by specifying a cache server that owns the content, and determining the communication possibility for each communication medium Selecting means for selecting a communication medium, and from the portal server Based on view, it is characterized in that and a content distributing unit for distributing the corresponding contents to the mobile terminal for which the said request via the selected communication media.

  According to the present invention, the media selection means determines the communication possibility for each communication medium and selects the optimum communication medium, and there is a request through the selected communication medium based on an instruction from the portal server. By instructing the mobile terminal to distribute the corresponding content, it is possible to construct a mechanism that utilizes short-range wireless communication as well as public media, for example, to improve communication reliability and information acquisition. Such communication charges can be reduced.

  Further, in the present invention, when the content is not owned, the content is received from the content server under the instruction of the portal server, the content is stored, and the portal server and another cache server are stored. Content list transmission means for broadcasting the updated content list.

  In order to solve the above-described problems, the present invention temporarily stores a mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and content provided by the content server. A content distribution method of a portal server in which a cache server to be stored is connected via respective communication media of a public mobile line, a wired line, a public mobile line, or a short-range wireless communication line, and the mobile terminal The content distribution request is received, the list of cache servers that own the corresponding content is searched with reference to the owned content list, and the optimal cache server is identified based on the location information of the mobile terminal and the cache server stored in advance. Content distribution from the identified cache server To instruct, it characterized.

  In order to solve the above-described problems, the present invention manages each mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and the location of content requested by the mobile terminal. And a portal server that distributes contents of a cache server connected via a communication medium of a public mobile line, a wired line, a public mobile line, or a short-distance wireless communication line. Receives a content delivery request from the mobile terminal, obtains a delivery instruction for the content instructed by specifying a cache server that owns the content, and determines the communication possibility for each communication medium Select the optimal communication media, and select the selected communication media based on instructions from the portal server. Performing the delivery of the corresponding content to the mobile terminal for which the said request via a signal medium, characterized by.

  In order to solve the above-described problems, the present invention temporarily stores a mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and content provided by the content server. A cache server to be stored is a content distribution program of a portal server connected via a communication medium of a public mobile line, a wired line, a public mobile line, or a short-range wireless communication line, and the mobile terminal Receiving a content delivery request from the server, searching a list of cache servers that own the content by referring to the owned content list, identifying an optimal cache server based on the location information of the mobile terminal and the cache server, Content distribution from the specified cache server Characterized in that to execute the steps of: instructing, to the computer.

  In order to solve the above-described problems, the present invention manages each mobile terminal having an agent execution base, a content server that distributes content to the mobile terminal, and the location of content requested by the mobile terminal. A content distribution program of a cache server connected via a communication medium of a public mobile line, a wired line, a public mobile line, or a short-range wireless communication line, and the portal server Receiving a content distribution request from the mobile terminal, obtaining a distribution instruction for the content by specifying a cache server that owns the content, and determining the communication possibility for each communication medium Selecting an appropriate communication medium and based on an instruction from the portal server Characterized in that to execute the steps for distributing the corresponding contents to the mobile terminal for which the said request via the selected communication media, to the computer.

  As described above, according to the present invention, the number of accesses to the ASP server that provides content from the portal server and the amount of communication can be reduced. Therefore, it is possible to reduce the load on the portal server and reduce network traffic, and to ensure communication reliability. Along with the improvement, the communication charges can be expected to be reduced.

Hereinafter, a content distribution system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a construction example of a content distribution system in which the present invention is adopted. In FIG. 1, reference numeral 1 denotes an in-vehicle device as a mobile terminal, which enables bidirectional vehicle-to-vehicle communication between a mobile vehicle and a cache server 3 described later. Reference numeral 2 denotes a portal server, which is a fixed server that provides a service integrated with a service by an ASP (Application Service Provider) described later.
Reference numeral 3 denotes a cache server, which is installed in a public common institution such as a bus or train, or a normal vehicle, temporarily stores contents provided by ASP, and responds quickly to access requests from clients. Used in meaning. Reference numeral 4 denotes a content server (hereinafter simply referred to as ASP server 4), which provides various contents such as video and music and navigation functions to the vehicle-mounted device 1 serving as a client via a network.

Note that each of the in-vehicle device 1, the portal server 2, the cache server 3, and the ASP server 4 includes an agent execution base. The access from the in-vehicle device 1 and the cache server 3 to the portal server 2 is, for example, a public mobile line 5 such as PIAFS (PHS Internet Access) or PDC (Personal Digital Cellular), between the in-vehicle device 1 and the cache server 3. The vehicle-to-vehicle communication includes a short-distance wireless communication 6 such as the above-described wireless public line 5 or IEEE802.11x (wireless LAN), and between the wireless base station 7, the portal server 3, and the ASP server 4, a LAN (Local Area Network) or They are connected via a wired line 8 such as a WAN (Wide Area Network) and communicate with each other.
Here, “agent execution platform” refers to software that moves on the network (switches processing to another device or program), collects necessary information according to the contents defined in the scenario, and performs various processes independently. Here, it is installed in any of the in-vehicle device 1, the portal server 2, the cache server 3, and the ASP server 4.

FIG. 2 is a block diagram showing the functions of the internal configurations of the portal server and the cache server according to the present invention.
The portal server 2 according to the present invention includes a data storage unit and a cache server management unit 22. The data storage unit includes a user information DB 211, a content / application information DB 212, and a cache server information DB 213. Although details will be described in detail with reference to FIG. 3, an outline, location information of the mobile system 1 and the cache server 3, As well as the owned content list.

The cache server management unit 22 receives the content distribution request from the in-vehicle device 1, refers to the content list stored in the data storage unit, searches the list of the cache server 3 that owns the corresponding content, and the in-vehicle device 1 and the cache Based on the location information of the server 3, the optimum cache server 3 is specified, and content distribution from the specified cache server 3 is instructed.
The cache server management unit 22 also has a function of instructing accumulation in the cache server 3 located closest to the vehicle-mounted device 1 by acquiring the corresponding content from the ASP server 4 when there is no cache server 3 that owns the corresponding content. Also has.

On the other hand, the cache server 3 of the present invention includes a media selection unit 31, a content distribution unit 32, a content list transmission unit 33, and a cache DB.
The media selection unit 31 receives the content distribution request from the in-vehicle device 1 by the portal server 2, obtains the distribution instruction of the corresponding content specified by specifying the cache server 3 that owns the corresponding content, It has a function to select the optimal communication media by judging the communication possibility. Further, the content distribution unit 32 has a function of distributing the corresponding content to the in-vehicle device 1 requested through the selected communication medium based on an instruction from the portal server 2.
In addition, when the content list generation unit 33 does not own the content, the content list generation unit 33 receives the content from the APL server 4 under the instruction of the portal server 2 and accumulates the content. It has a function of broadcasting the updated content list to the public common institution cache server 3.
It is assumed that the cache DB 34 stores the contents obtained from the ASP server 4 and cached.

FIG. 3 shows information managed by the portal server 2, that is, information stored in the data storage unit (user information DB 211, content / application information DB 312 and cache server information DB 313) of the portal server 2 with an example. FIG.
That is, the user information DB 211 includes a user ID, a password, vehicle position information (URL or latitude / longitude), and communication route selection reference information. Here, the position information of the vehicle is managed in a URL (Uniform Resource Locator) format or a latitude / longitude format. Further, the communication path selection criterion information can be selected from the viewpoint of price, stability, and communication speed by setting by a user when selecting a communication medium. However, the selection criteria may be determined as a method for the agent to reliably reach the user based on the content type, size, area, and communication possibility. Details of both will be described later.

The content / application information DB 312 includes a content ID / application ID and a URL of the ASP server 4 that holds the content. Here, the content ID refers to the content itself, and the application ID refers to an application required to operate the content, which is different but related.
The cache server information DB 313 includes a cache server ID, a content ID / application ID, and vehicle position information. The content ID / application ID and vehicle position information are as described above.

4 and 5 are system operation sequence diagrams cited for explaining the operation of the embodiment of the present invention. When there is no content required for the cache server 3 (FIG. 4), it is necessary for the cache server 3. Each case where content exists and the cache server 3 is selected with the shortest distance (FIG. 5) is shown.
4 shows an operation sequence between the in-vehicle device 1, the cache server 3, the portal server 2, and the ASP server 4, and FIG. 5 shows an operation sequence between the in-vehicle device 1, the cache server 3, and the portal server 2. Yes.
The operation of the embodiment of the present invention shown in FIGS. 1 to 3 will be described in detail below with reference to the system operation sequence diagrams shown in FIGS.

First, the operation when the requested content does not exist in the cache server 3 will be described with reference to the system operation sequence diagram shown in FIG.
The portal server 2 receives user login information via the in-vehicle device 1. The login information includes a user ID, a password, a car URL, and a content ID. Here, the automobile URL indicates the position information of the automobile, and is information indicating the latitude and longitude of the vehicle that is the moving body. Next, the portal server 2 accesses the user information DB 211 and performs user authentication for the received login information (S41). Then, the fact that the authentication is complete is transmitted to the in-vehicle device 1.
Further, the portal server 2 receives the content request and the vehicle position information from the in-vehicle device 1, transmits the reception of the request to the in-vehicle device 1, and activates the mobile agent (S42).

When the mobile agent is activated, the cache server management unit 22 acquires a list of cache servers that own the requested content (S43), and from this list, the presence or absence of the cache server 3 that possesses the content ID Is confirmed (S44). If there is a cache server 3 that owns the requested content ID, an optimum cache server selection process described later is executed (S47), and the cache server with the shortest distance between the vehicle-mounted device 1 and the cache server 3 is executed. 3 is selected, and the user ID, the car URL, the requested content ID, and the corresponding content are transmitted to the cache server 3.
On the other hand, if there is no cache server 3 that owns the requested content ID, the agent moves to the ASP server 4 that owns the requested content (S45), and the agent acquires the requested content and sends it to the portal server 2. Transmit (S46). Thereafter, the optimum cache server selection process of S47 described above is followed.

The cache server 3 that has received the requested content or the like activates the content list transmission unit 33 in addition to updating its own cache list, and sends the updated cache list to the other cache servers 3 and the portal server 2. Broadcast transmission is then performed to synchronize (S49).
In addition, the cache server 3 accumulates the received content in the cache DB 34 (S49) and activates the media selection unit 31 to perform communication media selection processing described later (S50). In addition to URL and content ID, notification of communication media is performed. As a result, the in-vehicle device 1 uses the notified communication medium, accesses the cache server 3 based on the received content URL and content ID, activates the content distribution unit 32, and becomes content acquisition ( S51).

Details of the communication media selection process (S50) by the media selection unit 31 will be described. Here, when the communication media possessed by the cache server 3 cannot perform wireless communication with the vehicle, the user has specified “price”, “communication speed”, “stability”, etc. as communication selection criteria. In this case, for example, not the wireless communication between the cache server 3 and the vehicle-mounted device 1, but a processing procedure when the content is distributed to the vehicle-mounted device 1 using other communication media such as a mobile phone. A process for selecting whether to use the media is executed.
FIGS. 6 to 9 show the respective processes when the communication selection criterion is “price”, “communication speed”, “stability”, “price”, and when the judgment of the agent is entered. The procedure is shown in the flowchart.

According to the example shown in FIG. 6, first, the possibility of communication is determined for each communication medium (S501a). Here, the communication possibility is performed by calculating whether the communication is possible by calculating the electric field strength from the position information of the base station 7 and the position information of the vehicle. If there are a plurality of communication media (S502a-Yes), a communication fee is calculated for each (S503a), and the cheapest one is selected (S504a). If there are not plural (S502a-No), the remaining communication medium is selected (S505a). Here, it is assumed that at least one communication medium is present, and when there is no communication medium, an abnormal processing system is established when communication is impossible.
That is, the media selection unit 31 stores a table (not shown) in which the content data amount and the communication fee are associated with each communication medium, and calculates the communication fee based on the content data amount from this table. , To choose the cheapest communication media.

According to the example shown in FIG. 7, the media selection unit 31 stores a table (not shown) in which the communication speed is associated with each communication medium, and selects the communication medium with the highest communication speed from the table. (S504b).
Further, according to the example shown in FIG. 8, the media selection unit 31 has a table (not shown) in which each communication medium is associated with a numerical value indicating whether the radio wave condition is good or not for each delivery area surrounded by latitude and longitude. ) And the communication medium that is the distribution area with the highest radio wave condition and the highest numerical value is selected based on the table (S504c).

Note that the example shown in FIG. 9 is based on the assumption that the user has specified that the communication medium with the lowest charge is selected. Here, even if the media selection unit 31 selects the cheapest communication medium, if the communication medium is an unreliable communication medium, the media selection unit 31 selects another communication medium based on its own judgment. Means. Here, whether or not the communication medium is reliable is determined based on a table (not shown) in which the communication area is associated with the reliability availability information for each communication medium.
That is, after selecting the cheapest communication medium (S504d), it is determined whether or not the selected communication medium is appropriate from the history when the same type of content is transmitted (S506d), and the result of checking whether or not it is correct ( S507d) When it is accurate (S507d-Yes), the selected inexpensive communication path is selected (S508d), and when it is not (S507d-No), the optimum communication path determined by the agent is selected (S509d). ). The history used here is obtained from the portal server 2, and the portal server 2 determines from the content distribution history to other users problems that occurred during distribution of the same or similar content and the reliability of the communication path in each area. The data about is accumulated.

Next, an example in which requested content exists in the cache server 3 and the cache server 3 is selected with the shortest distance will be described with reference to a system operation sequence diagram shown in FIG.
The portal server 2 receives the login information from the in-vehicle device 1 and authenticates the user. Further, the portal server 2 receives the content request and the vehicle position information, activates the mobile agent, and selects from the list of cache servers possessing the content. The series of operations up to confirming whether or not there is a cache server 3 possessing a content ID is the same as the system operation sequence shown in FIG. 4, and thus detailed description is omitted in order to avoid duplication. To do.

Here, when the cache server 3 exists, the optimum cache server selection process (S47) is executed. Here, the distance from the reference is used as a reference to calculate the straight line distance from the request source (S471), and the in-vehicle device of the request source The cache server 3 located in the shortest distance from 1 is selected (S472).
In addition, there is a method of selecting in consideration of the direction. Specifically, the communication time can be determined by selecting the cache server 3 that can maintain the “short-distance state” for as long as possible, using the location information of the in-vehicle device 1 and the cache server 3 as the request source and the predicted traveling direction. Such streaming data, large-capacity files, and the like can be communicated with the possibility of being cut off as low as possible. Furthermore, in order to improve the accuracy of the prediction of the traveling direction of the cache server 3, it is conceivable to use a data mining technique based on the vehicle travel history, position, time, content history, etc. accumulated in the portal server 2.

Here, the fire server 2 transmits the user ID, the car URL, and the content ID to the selected cache server 3, and the cache server 3 acquires the content URL (S52), and then performs the communication media selection process described above. (S50) After execution, the notification of the cache content URL, the content ID, and the selected communication media information is transmitted to the vehicle-mounted device 1 that requested it.
In the in-vehicle device 1, based on the communication media information notified from the cache server 3, processing (S 51) for acquiring content via the communication media is executed. At this time, the previously received content URL and content ID are used.

As described above, according to the present invention, in the case of content with high position dependency, information to be acquired from a mobile terminal such as an in-vehicle device in the same region often has the same content, for example, a bus Since there is a high possibility that information is stored in familiar public institutions such as trains and trains, it is equipped with a cache server 3 that caches content in public transport that often circulates within a certain range, and the inter-vehicle communication medium The medium is selected based on an original selection criterion.
Specifically, the portal server 2 manages the location information and the owned content list of public transportation such as buses and trains (equipped with the cache server 3). A list of cache servers 3 having contents is searched, and the cache server 3 closest to the vehicle-mounted device 1 is identified from the list in consideration of the positions of the vehicle-mounted device 1 and the cache server 3.

Then, the identified cache server 3 determines whether or not communication media can be communicated according to a preset priority order, and selects the communication media with the lowest communication fee, for example, and distributes the corresponding content to the in-vehicle device 1. If there is no cache server 3 having the corresponding content, the mobile agent is activated to acquire the corresponding content from the ASP server 4, and the corresponding cache server 3 located closest to the in-vehicle device 1 that requested it. The cache server 3 to which the content has been transferred and received the content stores the content, and broadcasts a new content list to the portal server 2 and the other cache server 3 to synchronize.
As a result, the download sources of content depending on the location are distributed, the number of accesses from the portal server 2 to the content provider (ASP server 4) and the amount of communication are reduced, and the communication media is used only for the public wireless line. In addition, by constructing a mechanism that utilizes short-range wireless communication, it is possible to improve the reliability of communication and reduce the communication fee for acquiring information.

  The procedure executed by each of the cache server management unit 22, the media selection unit 31, the content distribution unit 32, and the content list transmission unit 33 shown in FIG. 2 is recorded on a computer-readable recording medium and recorded on this recording medium. The portal server and the cache server in the content distribution system of the present invention are realized by causing the computer system to read and execute the program. The computer system here includes an OS and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope not departing from the gist of the present invention.

It is a figure which shows the construction example of the content delivery system by which this invention is employ | adopted. It is the block diagram which expanded and showed the internal structure of each of the portal server of this invention, and a cache server. It is a figure which shows an example of the data structure of the database which a portal server manages. It is a system operation | movement sequence diagram quoted in order to demonstrate operation | movement of this invention embodiment. It is a system operation | movement sequence diagram quoted in order to demonstrate operation | movement of this invention embodiment. 6 is a flowchart cited for explaining an example of a detailed procedure of the communication media selection process shown in FIGS. 4 and 5. 6 is a flowchart cited for explaining an example of a detailed procedure of the communication media selection process shown in FIGS. 4 and 5. 6 is a flowchart cited for explaining an example of a detailed procedure of the communication media selection process shown in FIGS. 4 and 5. 6 is a flowchart cited for explaining an example of a detailed procedure of the communication media selection process shown in FIGS. 4 and 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle equipment, 2 ... Portal server, 3 ... Cache server, 4 ... Content server (ASP server), 5 ... Wireless public line, 6 ... Near field communication, 7 ... Wireless base station, 8 ... Wired line, 22 ... Cache server management unit, 31 ... media selection unit, 32 ... content distribution unit, 33 ... content list transmission unit, 34 ... cache DB, 211 ... user information DB, 212 ... content / application information DB, 213 ... cache server information DB

Claims (8)

A mobile terminal, each having an agent execution base, a content server that distributes content to the mobile terminal, and a cache server that temporarily stores content provided by the content server are public mobile lines, A portal server in a content distribution system connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
Data storage means for storing location information of the mobile terminal and the cache server, and a list of contents owned for each cache server;
A content distribution request is received from the mobile terminal, a list of cache servers that own the content is searched, an optimal cache server is specified based on location information of the mobile terminal and the cache server, and the specified cache A cache server management means for instructing content distribution from the server;
A portal server in a content distribution system characterized by comprising: The cache server management means includes:
When there is no cache server that owns the relevant content, the relevant content is acquired from the content server and instructed to be stored in the cache server located closest to the mobile terminal. 2. A portal server in the content distribution system according to 1. A mobile terminal having an agent execution platform, a content server that distributes content to the mobile terminal, and a portal server that manages the location of content requested by the mobile terminal are public mobile lines, A cache server in a content distribution system connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
The portal server receives a content distribution request from the mobile terminal, obtains a distribution instruction for the corresponding content specified by specifying a cache server that owns the corresponding content, and determines the communication possibility for each communication medium. A media selection means for judging and selecting the optimum communication media;
Based on an instruction from the portal server, content distribution means for distributing the content to the requested mobile terminal via the selected communication medium;
A cache server in a content distribution system comprising: If the content is not owned, the content is received from the content server under the instruction of the portal server, the content is stored, and the content updated to the portal server and other cache servers Content list transmission means for broadcasting the list;
The cache server according to claim 3, further comprising: A mobile terminal, each having an agent execution base, a content server that distributes content to the mobile terminal, and a cache server that temporarily stores content provided by the content server are public mobile lines, A content distribution method for a portal server connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
Receiving a content delivery request from the mobile terminal, searching a list of cache servers that own the content with reference to the owned content list,
Specifying an optimal cache server based on the location information of the mobile terminal and the cache server stored in advance, and instructing content delivery from the specified cache server;
A content distribution method characterized by the above. A mobile terminal having an agent execution platform, a content server that distributes content to the mobile terminal, and a portal server that manages the location of content requested by the mobile terminal are public mobile lines, A content distribution method for a cache server connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
The portal server receives a content distribution request from the mobile terminal, and obtains a distribution instruction for the content instructed by specifying a cache server that owns the content;
Judging the communication possibility for each communication medium and selecting the optimum communication medium,
Based on an instruction from the portal server, delivering the corresponding content to the mobile terminal that has made the request via the selected communication media;
A content distribution method in a content distribution system. A mobile terminal, each having an agent execution base, a content server that distributes content to the mobile terminal, and a cache server that temporarily stores content provided by the content server are public mobile lines, A portal server content distribution program connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
Receiving a content delivery request from the mobile terminal, referring to an owned content list and searching a list of cache servers that own the content; and
Specifying an optimal cache server based on the location information of the mobile terminal and the cache server, and instructing content delivery from the specified cache server;
Distribution program that causes a computer to execute A mobile terminal having an agent execution platform, a content server that distributes content to the mobile terminal, and a portal server that manages the location of content requested by the mobile terminal are public mobile lines, A content distribution program for a cache server connected via a communication medium of a wired line, a public mobile line, or a short-range wireless communication line,
The portal server receives a content distribution request from the mobile terminal, obtains a distribution instruction for the corresponding content specified by specifying a cache server that owns the corresponding content, and determines the communication possibility for each communication medium. Judging and selecting the most suitable communication media;
Based on an instruction from the portal server, delivering the content to the requested mobile terminal via the selected communication media;
Distribution program that causes a computer to execute

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