A control method and system for information delivry through mobile communications network

BACKGROUND OF THE INVENTION

1. Field of the Invention

0001The present invention relates to a control method and a control system for delivering information to mobile terminal through mobile communication network. The present invention further relates to an information storage method which is performed at each node in the mobile communication network where information is delivered in accordance with the control method.

2. Description of the Related Art

0002A control method for delivering information using the cache function of the fixed communication network is defined in the standards, RFC2186 (Internet Cache Protocol, Version 2) and RFC2187 (Application of Internet Cache Protocol, Version 2). In the mobile communication network where the control method for delivering information complying with the standards,. the existence of a cache node along the route through which data is transferred is checked before a mobile terminal downloads the data. If a cache node exists in the delivery channel, the information delivery is performed through the cache node.

0003A communication system in which the information delivery is performed in compliance with the control method for delivering information to fixed terminals are configured as shown in <figref idref="f0001">Fig. 1</figref>, for example. The Internet Cache Protocol is utilized as the control method for delivering information.

0004In <figref idref="f0001">Fig. 1</figref>, the communication network includes communication nodes N1-N6 each functioning as a router and communication nodes 21, 22, 31, and 41 each functioning as a router and a cache (hereinafter referred to as "cache nodes"). The local cache node 21 (LC-1) is connected to the parent cache node 31 (PC-1) through the communication node N3 and the subsidiary cache node 22 (SC-1) through the communication node N2. The parent cache node 31 is connected to the grand parent cache node 41 (GC-1) through the communication nodes N4 and N5. The grand parent cache node 41 is connected to the internet INT where a host server 50 (SVR) exists, through the communication node N6.

0005Client terminals 10₁ (C1) , 10₂ (C2), 10₃ (C3) are connected to the local cache node 21 through the communication node N1. They receive information delivery service from the communication network where the local cache node 21, the parent cache node 31, and the grand parent cache node 41 each having a cache function are arranged in a hierarchy.

0006In the network system described above, information "D" stored in the host server SVR is transferred to the client terminal 10₁(C1), for example, in the following manner.

0007A request for delivery of the information D sent by the client terminal 10₁ is transferred to the local cache node 21 through the communication node N1. The local cache node 21 checks whether it stores the information D, and if it does not store the information D, it transfers the request for delivery toward the communication node N3. In response to the reception of the request for the delivery, the parent cache node 31 checks whether it stores the information D, and if it does not store the information D, it further transfers the request for delivery toward the communication node N4. The request for delivery is transferred to the grand parent node 41 through the communication nodes N4 and N5. As described above, if no cache node stores the information I) which is requested by the client 10₁, the request for delivery is transferred to the communication nodes (including cache nodes) sequentially.

0008The request for delivery of the information D is finally transferred to the host server 50 in the internet INT. The host server 50 delivers the information D the client terminal 10₁ through the internet INT. The information D delivered by the host server 50 is delivered to the client terminal 10₁ through each communication nodes (including cache nodes).

0009An example of a cache management scheme involving the relocation of full caches is disclosed by the document "A resource management scheme for efficient WWW computing in wireless communications" by Hadjiefthymiades et al.

0010As shown in <figref idref="f0002">Fig. 2</figref>, in the process in which the information D is delivered from the host server 50 to the client terminal 10₁, the cache nodes, the local cache node 21 and the parent cache node 31 for example, near the client terminal 10₁ stores (or caches) cache information D' identical to the information D.

0011If one of the client terminals 10₁, 10₂, 10₃ issues another request for delivery or the information D , the cache information D' corresponding to the information D stored in the local cache node 21 is delivered to the client terminal requested for the delivery. Accordingly, the traffic within the communication network is reduced.

0012Mobile terminals, however, move while receiving the delivery of information, that is, downloading data. Therefore, it is necessary to switch delivery channel while receiving information. Since the switching of the communication channel degrades the efficiency of information delivery, it is not practical to apply the abovementioned method for delivery information complying with the Internet Cache Protocol designed for the fixed communication network to the mobile communication network. For example, while receiving the delivery of cache information from a cache node in the mobile communication network, a mobile terminal, as it moves, switches its connection to cache nodes. That is, the delivery channel between the mobile terminal and the host server is switched. If a new delivery channel does not include cache node which stores cache information, the cache function of the cache nodes do not work effectively.

SUMMARY OF THE INVENTION

0013Accordingly, it is the object of the present invention to provide an information storage method for communication nodes in the mobile communication network to which the control method for delivery information is applied.

0014To achieve the object, the present invention includes an information storage method for a first cache node in a mobile communications network in which a mobile terminal receives information through a plurality of delivery channels while said mobile terminal moves from a communication area to another, wherein a portion of said information which is transferred through said first cache node is stored in said first cache node, and said first cache node maintains a table indicating the relation between said information to be delivered to said mobile terminal and said portion of said information which has been transferred through said first cache node; if said first cache node storing said portion of said information therein is included in a delivery channel established in response to a delivery request from said mobile terminal for said information, said first cache node delivers said portion of said information to said mobile terminal; and if a second cache node is included in said delivery channel established in response to said delivery request, said first cache node informs said second cache node that said first cache node has delivered said portion of said information and said second cache node delivers a remaining portion of said information to said mobile terminal except for said portion of said information which has been delivered by said first cache node to said mobile terminal through said delivery channel.

0015In this information storage method, in the process that the cache information is delivered to the mobile terminal, portions of the cache information are stored in each communication node in the mobile communications network. If another mobile terminal requests for the delivery of the information under the circumstances where the portions of the cache information are stored in each communication node, the portions of the cache information are to be delivered from each communication node to the mobile terminal.

0016Accordingly the volume of information transferred through the delivery channel in the mobile communications network can be reduced.

0017The present invention is yet further configured to a control system for information delivery to a mobile terminal through a plurality of delivery channels in a mobile communication network, while said mobile terminal moves from a communication area to another, the control system including a plurality of cache nodes storing portions of said information, including a first cache node and a second cache node, wherein said first cache node is adapted to store a portion of said information which is transferred through said first cache node, to maintain a table indicating the relation between said information to be delivered to said mobile terminal and said portion of said information which has been transferred through said first cache node, and, if said first cache node storing said portion of said information is included in a delivery channel established in response to a delivery request from said mobile terminal for said information, to deliver said portion of said information to said mobile terminal based on said table indicating the relation between said information to be delivered to said mobile terminal and said portion of said information which has been transferred through said first cache node; wherein said first cache node is further adapted, if said second cache node is included in said delivery channel established in response to said delivery request, to inform said second cache node that said first cache node has delivered said portion of said information, and said second cache node is adapted, if said second cache node is included in said delivery channel established in response to said delivery request, to deliver a remaining portion of said information to said mobile terminal except for said portion of said information which has been delivered by said first cache node to said mobile terminal through said delivery channel.

0018Furthermore, the present invention is configured to a cache node apparatus which is adapted to deliver information to a mobile terminal through a plurality of delivery channels while said mobile terminal is adapted to move from a communication area to another communication area, said cache node apparatus comprising: a control register unit for storing, entry data therein; and a network control unit for storing, in response to a hand-over request from said mobile terminal, entry data of said mobile terminal in said control register unit if said control register unit does not store said entry data of said mobile terminal; wherein said first cache node is adapted to store a portion of said information which is transferred through said first cache node apparatus, to maintain a table indicating the relation between said information to be delivered to said mobile terminal and said portion of said information which has been transferred through said first cache node apparatus, and, if said first cache node apparatus storing said portion of said information is included in a delivery channel established in response to a delivery request from said mobile terminal for said information, to deliver said portion of said information to said mobile terminal; wherein said first cache node is further adapted, if a second cache node apparatus is included in said delivery channel established in response to said delivery request, to inform said second cache node apparatus that said first cache node apparatus has delivered said portion of said information, said second cache node being adapted to deliver a remaining portion of said information except for said portion of said information which has been delivered by said first cache node apparatus to said mobile terminal through said delivery channel.

0019Other objects, features, and advantages of the present invention will be more apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0020<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a schematic drawing showing a conventional fixed communication network system in which information delivery is controlled in accordance with the Internet Cache Protocol;</li><li><figref idref="f0002">Fig. 2</figref> is a schematic drawing showing cache information stored in each node in the conventional fixed communication network system shown in <figref idref="f0001">Fig. 1</figref>;</li><li><figref idref="f0003">Fig. 3</figref> is a schematic drawing showing a configuration of a mobile communication system in which information delivery is controlled by the control method relative to an embodiment of the present invention;</li><li><figref idref="f0004">Fig. 4</figref> is a schematic drawing showing a mobile communication system, relative to the embodiment of the present invention, in which information delivery channel is switched as a mobile terminal moves;</li><li><figref idref="f0005">Fig. 5A, 5B, and 5C</figref> are schematic drawings of a stored data table relative to an embodiment of the present invention; and</li><li><figref idref="f0006">Fig. 6</figref> is a.block diagram of a communication node apparatus relative to an embodiment of the present invention.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0021<figref idref="f0003">Fig. 3</figref> shows a system in which information is delivered in accordance with the control method for delivering information relative to an embodiment of the present invention.

0022In <figref idref="f0003">Fig. 3</figref>, a mobile communication network includes local cache nodes 21₁, 21₂, 21₃, 21₄, parent cache nodes 31₁, 31₂, 31₃, and grand parent cache node 40, each operating as a router and an information storage device. The local cache node 21₁ is connected to the parent cache node 31₁ through a communication node N41. The local cache node 21₂ is connected to the parent cache node 31₁ through communication nodes N32 and N41. The local cache node 21₃ is connected to the parent cache node 31₂ through a communication node N33. The local cache node 21₄ is connected to the parent cache node 31₃ through a communication node N34.

0023The parent cache node 31₁ is further connected to a communication node N71 through communication nodes N51 and N61. Each of the parent cache nodes 31₂ and 31₃ is connected to a communication node N52. The communication node N52 is connected to the communication node N71 through communication nodes N62 and N72. The communication node N71 is further connected to the grand parent cache node 40. The grand parent cache node 40 is connected to the internet including a host server 50 through a communication node N8.

0024A plurality of wireless base stations 11₁₁, 11₁₂, ...., 11_1n (BS) is connected to the local cache node 21₁ through communication nodes N11 and N21. A mobile terminal 15₁ (MT) receives the delivery of information (packets) through the mobile communication network described above by wireless communicating with one of the wireless base stations.

0025The host server 50. in the internet INT stores information D. It is assumed that the grand parent cache node 40, the parent cache node 31₁, and the local cache node 21₃ in the mobile communication network have already stored cache information D'.

0026When the mobile terminal 15₂ is turned on, while staying in the communication area of the wireless base station 11_2m, or enters the communication area of the wireless base station 11_2m, the wireless base station 11_2m recognizes that the mobile terminal 15₂ is in its communication area, and establishes a default delivery channel of information for the mobile terminal 15₂ in the following manner.

0027In response to the recognition that the mobile terminal 15₂ is in its communication area, the wireless base station 11_2m issues a registration request of the mobile terminal 15₂ together with, for example, its own identification such as its IP address toward the communication node N12. The registration request is transferred through the communication nodes N12 and N22, the local cache node 21₂, the communication nodes N32 and N41, the parent cache node 31₁, the communication nodes N51, N61, N71, the grand parent node 40, and the communication node N8. During the process of transferring the registration request, each node (including cache nodes) registers itself as a member of the delivery channel for the mobile terminal 15₂ (entry). Accordingly, a default delivery channel ① is established for the mobile terminal 15₂ in the mobile communication network.

0028When the mobile terminal 15₂ issues a delivery request for information D toward the wireless base station 11_2m, the wireless base station 11_2m transfers the request serially through each communication nodes (including cache nodes) in the delivery channel ① described above. In the delivery process, each cache node checks whether it stores cache information D' relative to the information D, in response to the receipt of the delivery request. If the cache node does not store the cache information D', the cache node further transfers the delivery request toward the upper communication nodes. If the cache node determines that it stores the cache information D', it determines that it becomes the delivery source of the cache information D'.

0029For example, if the local cache node 21₂ finds, in response to the delivery request, that it does not store the cache information D' relative to the information D, the local cache node 21₂ transfers the delivery request toward the communication node N32. The parent cache node 31₁ checks, in response to the receipt of the delivery request, whether it stores cache information D', and if the parent cache node 31₁ finds that it stores the cache information D' therein, it determines that it becomes the delivery source of the cache information D'.

0030Accordingly, once the parent cache node 31₁ determines that it becomes the delivery source of the cache information D', it transfers the cache information D' addressed to the mobile terminal 15₂ toward the communication node N41. The cache information D' is transferred to the wireless base station 11_2m which performs wireless communications with the mobile terminal 15₂ through the communication nodes N41 and N32, the local cache node 21₁, the communication nodes N41 and N32, the local cache node 21₁, the communication nodes N21 and N11, and finally delivered from the wireless base station 11_2m to the mobile terminal 15₂.

0031Under such situation, it is further assumed that the mobile terminal 15₂, while being delivered the cache information D' from the parent cache node 31₁, moves from the communication area of the wireless base station 11_2m to the communication area of the wireless base station 11₃₁.

0032The mobile terminal 15₂ sends a hand-over request. In response to the receipt of the hand-over request, the wireless base station 11_2m transfers the hand-over request toward the communication node N12 next to the wireless base station 11_2m. The hand-over request is further transferred from the communication node N12 through each communication node (including cache nodes) in the delivery channel ①. The parent cache node 31₁ which is delivering the cache information D' stops the delivery of the cache information D' in response to the receipt of the hand-over request.

0033The mobile terminal 15₂ sends the hand-over request with the information which is contained in the cache information D' to identify the original information D to the wireless base station 11₃₁. In response to the hand-over request, another default delivery channel ② is newly established in the following manner.

0034The wireless base station 11₃₁ receives the hand-over request, and record (entry) that it becomes a member of the delivery channel for the mobile terminal 15₂ after finding that it has no entry of the mobile terminal 15₂. The wireless base station 11₃₁ next transfers the hand-over request to the upper node, that is, the communication node N13. The communication node N13 makes the entry of the mobile terminal 15₂, and further transfers the hand-over request to the upper node, that is the communication node N23. In the same manner, the hand-over request is transferred serially from the communication node N23 through the local cache node 21₃, the communication node N33, the parent cache node 31₂, the communication nodes N52, N62, and N72, to the communication node N71. During this process, each communication node records (entry) that it became a member of the delivery channel for the mobile terminal 15₂. Since the communication node N71, however, has the entry of the mobile terminal 15₂, it does not transfer the hand-over request to the upper node. The communication node N71 recognizes that it is a common member of both delivery channels before and after the hand-over, that is, the diverging point of the two delivery channels.

0035When the communication node N71 finds that it is the diverging point of the two delivery channels, sends a control signal for eliminating the entry of the mobile terminal 15₂ toward the communication node N61 in the delivery channel ①. This control signal is transferred to the wireless base station 11_2m serially through the communication nodes N61 and N51, the parent cache node 31₁, the communication nodes N41 and N32, the local cache node 21₂, the communication nodes N22 and N12. During this process, each communication node eliminates the entry relative to the mobile terminal 15₂. That is, the delivery channel ① for the mobile terminal 15₂ is disengaged.

0036As described above, once each communication node finishes recording the entry relative to the mobile terminal 15₂, a new delivery channel ② for the mobile communication terminal 15₂ after the hand-over is established in the mobile communication network.

0037After the new delivery channel ② is established, a delivery request for the cache information D' issued by the mobile terminal 15₂ is transferred from the wireless base station 11₃₁ which received the delivery request from the mobile terminal 15₂ to the local cache node 21₃ serially through the communication nodes N13 and N23 in the delivery channel ②. The local cache node 21₃, in response to the delivery request, checks that it stores the cache information D' therein, then informs the communication node N33 next to the local cache node 21₃ that the local cache node 21₃ stores the cache information D', and is the cache node near the mobile terminal 15₂ which originated the delivery request. The information is transferred from the communication node N33 up to the communication node N71, the diverging point of the old and new delivery channels, through the parent cache server 31₂ and the communication nodes N52, N62, and N72, serially.

0038On the other hand, the parent cache node 31₁ which was the delivery source of the cache information D' before the hand-over sends control information indicating that it stopped the delivery of the cache information D' because of the hand-over to the communication node N51. The information is. transferred through the communication nodes N51 and N61 up to the communication node N71. The control information described above further indicates the portion (sequence number) of the cache information D' delivered prior to the hand-over request from the mobile terminal 15₂ in addition to the information that the transfer of the cache information D' was interrupted by the hand-over.

0039The communication node N71, in response to the receipt of the above information, transfer the information about the delivered portion of the cache information D' to the local cache node 21₃, that is, the new delivery source of the cache information D'. The information is transferred to the local cache node 21₃ through the communication nodes N72, N62, and N52, the parent cache node 31₂, and the communication node N33.

0040The local cache node 21₃, in response to the receipt of the information about the delivered portion of the cache information D', delivers the remaining portion of the cache information D' to the mobile terminal 15₂. The remaining portion of the cache information D' is transferred through the communication nodes N23 and N13 to the wireless base station 11₃₁, the destination of the hand-over, in the delivery channel ②. It is further transferred from the wireless base station 11₃₁ to the mobile terminal 15₂.

0041As described above, even if the mobile terminal 15₂ is handed over to the wireless base station 11₃₁ during the information delivery, the mobile terminal 15₂, which is receiving the cache information D' from the parent cache node 31₁ through the communication nodes N41 and N32, the local cache node 21₁, the communication node N22 and N12, and the wireless base station 11_2m in the delivery channel ①, can continuously receive the remaining portion of the cache information, 'after the hand-over without issuing another delivery request-for the information D. Accordingly, the information delivery control in the mobile communication network realizes efficient information delivery with utilizing the cache function of the communication nodes, and reduces information traffic within the mobile communication network.

0042In the embodiment described above, it is assumed that communication nodes (including cache nodes) in the mobile communication network are connected in a hierarchy (at least logically), but the control method for delivering information is also applicable to a mobile communication network in which communication nodes are connected in a different manner such as meshed configuration.

0043In the mobile communication network in which information delivery is controlled as described above, each cache node stores information in the following manner.

0044In the case that the mobile terminal 15 to which information is delivered through the mobile communication network where the information delivery is controlled in the manner described above moves in a wide range, as shown in <figref idref="f0004">Fig. 4</figref>, cache nodes serve the mobile terminal 15 by turns, as the mobile terminal 15 moves in the range, as a delivery source of the cache information. In <figref idref="f0004">Fig. 4</figref>, common components to <figref idref="f0003">Fig. 3</figref> are referred to by the same numerals as in <figref idref="f0003">Fig. 3</figref>. The communication nodes. connected to the local cache nodes 21₁, 21₂, 21₃, 21₄ and the wireless base stations under the local cache nodes are omitted.

0045While the mobile terminal 15 staying at a position 1 receives the cache information D' from the parent cache node 31₁ through the communication nodes N41. and N32 and the local cache node 21₂ (delivery channel ①), the local cache node 21₂ stores the cache information D' (packets) serially. After receipt of a portion d1 of the cache information D', the mobile terminal 15 is assumed to move from the position 1 to a position 2. Since the grand parent cache node 40 starts serving, in accordance with the control method for information delivery described above, the mobile terminal 15 as a new delivery source of the cache information D' after the move of the mobile terminal 15, the parent cache node 31₁ stops sending the cache information D' to the local cache node 21₂. The local cache node 21₂ registers the storage of the portion d1 of the cache information D' therein.

0046The local cache node 21₂ registers the storage using a stored data control table, shown in <figref idref="f0005">Fig. 5A</figref> for example, indicating information for identifying the cache information D' (its name, for example) and information for identifying the portion d1, such as sequential numbers of stored packets (SN1 - SNn, for example).

0047As the mobile terminal 15 moves to the position 2, the grand parent cache node 40 starts delivering the remaining portion of the cache information D' as the new delivery source of the cache information D' in accordance with the procedure described above in reference with <figref idref="f0003">Fig. 3</figref>. Then, the remaining portion of the cache information D' is transferred to the mobile terminal 15 at the position 2 through communication nodes N71, N72, N62, and N52, the parent cache node 31₂, and the local cache node 21₃ (delivery channel ②). The parent cache node 31₂ and the local cache node 21₃ store the cache information D', portion by portion, as they transfer the cache information D'.

0048Furthermore, the mobile terminal 15 is assumed to move from the-position 2 to a position 3 after it receives portions d2 and d3 of the cache information D'. Due to this move, a new delivery channel of the cache information from the grand parent cache node 40 through the parent cache node 31₃ and the local cache node 21₄ is established in accordance with the abovementioned control method for information delivery, and the parent cache node 31₂ and the local cache node 21₃ are disengaged from the delivery channel. Once the new delivery channel is established, the parent cache node 31₂ stops sending the cache information D' to the local cache node 21₃. The local cache node 21₃ registers therein the portions d2 and d3 of the cache information D' which have been stored.

0049As shown in <figref idref="f0005">Fig. 5B</figref>, the local cache node 21₃ maintains a stored data control table indicating the relationship between the information to identify the cache information D' and the information (packet sequential numbers) to identify the stored portions d2 and d3 of the cache information D'.

0050The yet remaining portion of the cache information D' is transferred from the grand parent cache node 40 to the mobile terminal 15 through the newly established, as the mobile terminal 15 moves to the position 3, delivery channel including the parent cache node 31₃ and the local cache node 21₄ (delivery channel ③). The parent cache node 31₃ and the local cache node 21₄ transferring the cache information D' store the yet remaining portions of the cache information D' portion by portion.

0051It is further assumed that the delivery of the cache information D' ends by the mobile terminal 15 receiving the portions d4 and d5 of the cache information D'. Accordingly the mobile terminal 15 obtains the cache data D' consisted of the portions d1, d2, d3, d4, and d5. The parent cache node 31₃ and the local cache node 21₄ receive no more portion of the cache information D' to be transferred because the portion d5 is-the last portion. The parent cache node 31₃ and the local cache node 21₄ register therein the portions d4 and d5 of the cache information D' stored by the end of the transfer of the cache information D'. For example, the stored data control table registers the relationship of the information to identify the cache information D' and the information to identify the'stored portion d4 and d5 (sequential numbers of packets) as shown in <figref idref="f0005">Fig. 5C</figref>.

0052As described above, as the mobile terminal 15 moves from the position 1 to the position 3, the delivery channel of the cache information D' is switched in the mobile communication network, and the portions of the cache information D' are stored by each cache node through which each portion of the cache data is transferred. Each cache node control the stored portions of the cache information D' utilizing the stored data control table shown in <figref idref="f0005">Figs. 5A, 5B, and 5C</figref>.

0053If another mobile terminal at the position 2, for example, requests for the delivery of the information D after the end of the delivery of the cache information D' to the mobile terminal 15, the information D is transferred to the mobile terminal in the following manner.

0054It is assumed here that the mobile terminal 15 issued another delivery request for the information D for the ease of description. The delivery request for the information D is transferred through the communication nodes (including cache nodes) with establishing the delivery channel ②. During the process, the local cache node 21₃, in response to the receipt of the delivery request of the information D, checks whether it stores the cache information D' of the information D relative to the delivery request. In reference to the stored data control table (shown in <figref idref="f0005">Fig. 5B</figref>), the local cache node 21₃ determines that it stores the portions d2 and d3 of the cache information D', and it transfers the information with the delivery request from the mobile terminal 15 as cache node information. The parent cache node 31₂ transfers, as cache node information, the information indicating that the local cache node 21₃ stores the portions d2 and d3 of the cache information D'. The grand parent cache node 40 further transfers, as cache node information, the information indicating that it stores entire cache information D'.

0055The grand parent cache node 40 which stores entire cache information D' relative to the delivery request from the mobile terminal 15 at the position 2, based on the delivery request and the cache node information, assigns the local cache node 21₃ as the delivery source of the portions d2 and d3 of the cache information D', and further assigns itself, that is, the grand parent cache node 40, as the delivery source of the remaining portions d1, d4, and d5 of the cache information D'. Then, information indicating that the local cache node 21₃ is assigned as the delivery source of the portions d2 and d3 of the cache information D' is transferred from the grand parent cache node 40 to the local cache node 21₃ as a control signal. In response to the control signal, the local cache node 21₃ serially transfers the portions d2 and d3 of the cache information D' to the mobile terminal 15 at the position 2. Accordingly, the portions d2 and d3 of the cache information D' are transferred from the local cache node 21₃ to the mobile terminal 15 through each communication node in the delivery channel ②.

0056After the local cache node 21₃ finishes transferring the portions d2 and d3, the local cache node 21₃ informs the grand parent cache node 40 that the local cache node 21₃ finished transferring the portions d2 and d3. The grand parent cache node 40, in response to the information indicating the finish of delivery, delivers the remaining portions d1, d4, and d5 of the cache information D' to the mobile terminal 15 at the position 2 through the communication nodes N71, N72, N62, N52, the parent cache node 31₂, the communication node N33, and the local cache node 21₃ in the delivery channel ②.

0057As described above, the cache information D' consisted of the portions d1, d2, d3, d4, and d5 is delivered from each cache node in the mobile communication network to the mobile terminal 15. In the procedure described above, the portions of the cache information D' is delivered to the mobile terminal 15 in the order of d2, d3, d1, d4, and d5. The mobile terminal 15 arranges the portions in reference to a packet sequential number of each portion into the order d1, d2, d3, d4, and d5. Accordingly, the mobile terminal 15 obtains the requested information D by reproducing the cache information D' arranged in the order of d1, d2, d3, d4, and d5.

0058Because portions of the cache information D' stored in the cache nodes in the delivery channel ② is effectively used through the delivery control of the cache information D' described above, only the portions d1, d4, d5 are necessary to be transferred through the delivery channel between the grand parent cache node 40 and the local cache node 21₃. It is only the delivery channel (including the wireless portion) between the local cache node 21₃ and the mobile terminal 15 at the position 2 that all portions d1, d2, d3, d4, and d5 of the cache information D' are delivered through. Compared to the case in which all portions of the cache information D' from the grand cache node 40 to the mobile terminal 15 at the position 2, information traffic in the mobile communication network is effectively reduced.

0059In the case that, after the delivery of the cache information D' to the mobile terminal 15, another mobile terminal at the position 3 makes a delivery request for the information D, each portion of the cache information D' is delivered to the mobile terminal at the position 3 in the same manner as the portions are delivered to the mobile terminal at the position 2 as described above. That is, the portions d4 and d5 from the local cache node 21₄, the remaining portions d1, d2, and d3 from the grand parent cache node 40 through the parent cache node 31₃ and the local cache node 21₄ are delivered to the mobile terminal 15 at the position 3. The mobile terminal 15 arranges the delivered portions of the cache information D' to reproduce the requested information D.

0060Accordingly, only portions d1, d2, and d3 of the cache information D' are delivered through the delivery channel between the grand cache node 40 and the local cache node 21₄. It is only the delivery channel (including wireless portion) between the local cache node 21₄ and the mobile terminal 15 at the position 3 that all portions of the cache information D' are necessary to be transferred through. Compared to the case in which all portions of the cache information D' are delivered from the grand parent cache node 40 to the mobile terminal at the position 3, the information traffic in the mobile communication network is reduced.

0061<figref idref="f0006">Fig. 6</figref> is a block diagram of a communication node apparatus 100 (including a cache node) relative to an embodiment of the present invention described above.

0062A communication node apparatus 100 which exchanges information with other communication node apparatuses 104 and 105 in a mobile communications network, includes a control register unit 102 which stores entry data therein. If the control register unit 102 stores the entry data therein, the communication node apparatus 100 is included in a delivery channel of information to the mobile terminal. The communication node apparatus further includes a network control unit 101 which, in response to a hand-over request from a mobile terminal, stores entry data of the mobile terminal in the control register unit 102 if the control register unit 102 does not store the entry data of the mobile terminal. Through this process, the communication node apparatus 100 joins the delivery channel of information to the mobile terminal.

0063The communication node apparatus 100 described above, wherein the network control unit 101, if the control register 102 stores the entry data of the mobile terminal therein, sends to one of the other communication node apparatuses, the communication node apparatus 105 for example, an instruction, in response to which the one of the network node apparatuses, that is, the communication node apparatus 105 in this example, deletes an entry data of the mobile terminal-stored in a control register unit thereof.

0064A cache node can be configured as the communication node described above, further including a cache data storage unit 103 which stores cache data therein, wherein the network control unit 101, in response to a delivery request for information from the mobile terminal, if the cache data is identical to the requested information, sends to a communication node apparatus a first signal indicating that the cache data storage unit 103 stores the cache data therein, and the network control unit 101, in response to a second signal from one of the communication node apparatuses indicating that a portion of the information has been sent to the mobile terminal, sends a remaining portion of the cache data identical to the information stored in the cache data storage unit.

0065In summary, according to the present invention, when the delivery channel of the mobile terminal which receives the cache information from the first cache node through the first delivery channel is switched to the second delivery channel, because the second cache-node in the second delivery channel continues the delivery of the cache information, the information transfer to a mobile terminal is performed in more efficient manner utilizing the cache function of the mobile communications network.

0066According to the present invention, in the process where the requested information is delivered to the mobile terminal, a portion of the information is stored in each communication node in the mobile communication network. Accordingly, if another mobile terminal requests for the same information, each communication node can deliver the portion of the information to the mobile terminal.

0067Furthermore, according to the present invention, a control method and system for information delivery in which information is delivered to a mobile terminal efficiently through a mobile communications network including each communication node storing a portion of the information are realized.

0068The preferred embodiments of the present invention are described above. The present invention is not limited to these embodiments.

0069This patent application is based on <patcit id="pcit0001" dnum="JP2002217812B"><text>Japanese priority patent application No. JP 2002 217 812</text></patcit> filed on January 15, 2001.