JP2007074413A - Content distribution apparatus, content receiving apparatus, content distribution system, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the amount of data transmission for on-demand distribution, adding redundancy. <P>SOLUTION: It is a contents distribution system which uses together multicast distribution and on-demand distribution in a radio network 3, and carries out a countermeasure against packet losses, by adding redundancy to multicast distribution data. At this time, a server 1 dynamically controls the redundancy according to packet loss status of a client 2, even though the data transmission amount of the radio network 3 is increased by adding the redundancy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a content distribution device, a content reception device, a content distribution system, and a computer program that distribute or receive content by using both multicast distribution and on-demand distribution in a wireless network.

In recent years, content distribution services in wireless networks have attracted attention. In addition to distributing mail-based text information such as e-mail magazines, multimedia content such as music and video is also distributed. In the future, due to user preferences and diversification of content, it is desired to improve technology in content distribution services in wireless networks.
By the way, since content distribution using a wireless network is performed via a base station in the network, content is individually distributed to a plurality of clients (terminals) located in almost the same place by bidirectional communication (hereinafter, (On-demand distribution) is not preferable in terms of bandwidth efficiency. Therefore, techniques for broadcasting the same content to a plurality of clients from a single base station (hereinafter referred to as multicast distribution) have been studied conventionally.

However, according to the wireless network, sometimes there is a dead zone where the wireless signal does not reach the client. At this time, a client that is receiving content distributed by multicast cannot receive one or more packets (packet loss).
Therefore, FEC (Forward Error Correction), which is a transmission error control method that detects errors due to packet loss during transmission and performs self-repair, is used as a measure against packet loss in multicast distribution. In FEC, K packets (contents) to be transmitted are encoded and transmitted as N (≧ K) encoded data. As a result, even if a packet loss occurs during transmission, the client can restore the original K packets by receiving at least K encoded data out of the N encoded data. However, this encoding process increases the amount of data to be transmitted, which increases the load on the network. Further, when the reception state of the client is further deteriorated and K encoded data cannot be received, the client cannot restore the original K packets. Here, N / K, which is the ratio of the number K of packets before encoding and the number N of data after encoding, is called redundancy.

Further, in the wireless network, since the reception status of each client is different, the packets that cannot be received by each client are also different. Therefore, when multicast distribution is performed using FEC in a wireless network, redundancy suitable for each client is different, and it is difficult for all clients to receive transmission data without packet loss. For this reason, there is known a technique for ensuring the communication quality of all clients by transmitting each client with the redundancy required by each client even if the reception status of each client is different (for example, patents). Reference 1)
JP 2005-65100 A

However, according to the technique disclosed in Patent Document 1, a relay that distributes a multicast-distributed packet to each client has a special feature that changes the redundancy of distribution data according to the redundancy required by each client. In order to transfer the redundancy required by each client from the distribution data transmitting apparatus, a transmission medium different from the original data transmission medium is required.
In order to deal with packet loss, FEC is originally used in the network layer of OSI (Open System Interconnection) 7 layers. However, the reception status of the client changes due to various factors such as time, place, content (application), and the like. Therefore, such a factor cannot be effectively dealt with only by a network layer in which it is difficult to observe the behavior of application data. Therefore, it is necessary to take measures against packet loss at the application layer using information that cannot be grasped at the network layer.

The present invention has been made based on the above circumstances, and in a content distribution system that uses both multicast distribution and on-demand distribution in a wireless network, measures are taken against packet loss by adding redundancy to multicast distribution data. It is another object of the present invention to provide a content distribution device, a content reception device, a content distribution system, and a computer program capable of on-demand distribution of data that cannot be received by a client during multicast.
In addition, although the amount of data transmitted over the network increases due to the addition of redundancy described above, the redundancy is dynamically controlled according to the packet loss situation of the client, and data transmission for on-demand delivery is performed. It is another object of the present invention to provide a content distribution device, a content reception device, a content distribution system, and a computer program that reduce the amount, thereby reducing the total transmission amount on the network.

  In order to solve the above-described problem, the present invention is a content distribution device that distributes content by using both multicast distribution and on-demand distribution in a wireless network, and the first content is distributed according to arbitrary redundancy with respect to the original content. An encoding operation unit that generates an encoded data group, and a push-type transmission unit that multicast-distributes the first encoded data group to a content receiver connected to the content distribution apparatus via the wireless network And the amount of data transmission in the second encoded data group that could not be received by the content receiving device based on packet loss information transmitted from the content receiving device due to multicast distribution of the first encoded data group A transmission amount estimation calculation unit for calculating a total sum of the second encoding data and the second coding data; A pull-type transmitting unit that performs on-demand distribution of a data group to all of the content receiving devices, and the first code by the encoding operation unit based on a total transmission amount in the second encoded data group And a redundancy determination calculating unit that updates the redundancy used for generating the data group.

  Further, in the present invention, the redundancy degree determination calculation unit includes a sum of data transmission amounts in the second encoded data group that is distributed on demand to the content receiving device, and the first encoding that is multicast distributed. Redundancy that minimizes the total amount of data transmission in the data group is calculated.

  Also, in the present invention, the push-type transmission unit writes information on the updated redundancy and the data amount of the original content in a predetermined area in the first encoded data group, via the wireless network. The first encoded data group is multicast-distributed to a connected content receiving device.

  In addition, the present invention is a content receiving apparatus that receives content by using both multicast distribution and on-demand distribution in a wireless network, and the content receiving apparatus is connected to the content receiving apparatus via the wireless network. A push-type receiving unit that receives the first encoded data group that is generated and multicast-distributed and that encodes the original content according to an arbitrary redundancy, and a content reproduction unit that decodes the first encoded data group A decoding calculation unit that transfers to the packet, a packet loss information generation unit that generates packet loss information based on the first encoded data that could not be decoded by the decoding calculation unit, the packet loss information, and an unreceived packet Send original content to the content distribution device for on-demand request Receiving the second encoded data corresponding to the unreceived original content, which is encoded by the updated redundancy based on the packet loss information, which is distributed on demand by the content distribution device, and the decoding operation Playing back the original content output by the pull type transmission / reception unit to be transferred to the decoding unit and the decryption calculation unit, and requesting the undelivered original content to the content distribution device via the pull type transmission / reception unit on demand And a section.

  Further, in the present invention, when the decoding operation unit encodes the original content with reference to information written in a predetermined area in the first encoded data received by the push type receiving unit The redundancy used in the above and the data amount of the original content are acquired.

  In the present invention, the packet loss information generation unit can receive the number of packets constituting the content based on the redundancy and the data amount of the content acquired through the decoding operation unit. The packet loss information is generated by obtaining a ratio of the number of missing packets.

  In addition, the present invention is a content distribution system that distributes content by using both multicast distribution and on-demand distribution in a wireless network, and generates a first encoded data group according to an arbitrary redundancy for original content An encoding calculation unit that performs multicast distribution of the first encoded data group to a content reception device connected via the wireless network, and the first encoding unit. Along with the multicast distribution of the data group, based on the packet loss information notified from the content receiving device, an operation is performed to estimate the total amount of data transmission in the second encoded data group that could not be received by the content receiving device. A transmission amount estimation calculation unit and the second encoded data group are received as the content reception unit. Redundancy used for generating the first encoded data group by the encoding unit based on the total amount of data transmission in the second encoded data group, a pull-type transmission unit that performs on-demand distribution to all of the devices A content distribution device comprising: a redundancy determination operation unit for updating the data; a push-type reception unit that receives the first encoded data group that is generated by the content distribution device and distributed by multicast; the received first A decoding operation unit that decodes the encoded data group and transfers the encoded data group to the content reproduction unit, and a packet loss information generation unit that generates packet loss information based on the first encoded data that could not be decoded by the decoding operation unit , Transmitting the packet loss information and the unreceived original content to the content distribution device for an on-demand request, and Receiving the second encoded data corresponding to the unreceived original content encoded by the redundancy updated based on the packet loss information, which is distributed on demand by the content distribution apparatus, and the decoding operation unit A pull-type transmission / reception unit for transferring to the content reproduction unit, reproducing the original content output by the decryption calculation unit, and requesting the undelivered original content to the content distribution device on-demand via the pull-type transmission / reception unit; And a content receiving apparatus comprising:

  The present invention is also a computer program used in a content distribution apparatus that distributes content by using both multicast distribution and on-demand distribution in a wireless network, and the first code according to an arbitrary redundancy with respect to the original content A process for generating a coded data group, a process for multicasting the first coded data group to a content receiving apparatus connected to the content distribution apparatus via the wireless network, and the first code With the multicast distribution of the encoded data group, an operation for estimating the total amount of data transmission in the second encoded data group that could not be received by the content receiving device based on the packet loss information notified from the content receiving device. A process to be performed and the second encoded data group as the content. A process of performing on-demand delivery to all of the receiving apparatuses, and a process of updating the redundancy used for generating the first encoded data group based on the total amount of data transmission in the second encoded data group Are executed by a computer.

  The present invention is also a computer program used for a content receiving apparatus that receives content by using both multicast distribution and on-demand distribution in a wireless network, and is connected to the content receiving apparatus via the wireless network. A process of receiving a first encoded data group generated by a content distribution apparatus and multicast-distributed by encoding original content according to an arbitrary redundancy; and a process of decoding the first encoded data group A process of generating packet loss information based on the first encoded data that could not be decoded, and transmitting the packet loss information and unreceived original content to the content distribution device for an on-demand request, On-demand distribution by content distribution device Receiving the second encoded data corresponding to the unreceived original content encoded with the updated redundancy based on the packet loss information, and reproducing the original content generated as a result of the decoding And causing the computer to execute an on-demand request to the content distribution apparatus via the pull-type transmission / reception unit for the unreceived original content.

According to the present invention, in a content distribution system that uses both multicast distribution and on-demand distribution in a wireless network, it is possible to take measures against packet loss by adding redundancy to multicast distribution data.
In addition, despite the increase in the amount of data transmitted over the network due to the addition of redundancy, the content distribution device dynamically controls the redundancy according to the packet loss situation of the content reception device, thereby delivering on-demand. Data transmission amount for the wireless network can be reduced, and as a result, the total transmission amount on the wireless network can be reduced. Furthermore, according to the present invention, it is possible to realize a packet loss countermeasure at the application layer using packet loss information that cannot be grasped at the network layer. For this reason, a particularly remarkable effect can be obtained when used for content distribution in a wireless network in which the reception status of the client changes due to various factors such as time, place, and application.

FIG. 1 is a diagram showing a system configuration and an operation concept of a content distribution system in an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a server as a content distribution apparatus, and reference numeral 2 denotes a plurality of clients as content reception apparatuses, which are connected via a wireless network 3 and a base station 4. The content distribution system having the above configuration takes a hybrid content distribution form having the following two functions.
One is a push-type distribution function for performing multicast distribution from the server 1 through the base station 4 to the clients 2 existing within the wireless communication range. In this case, the content is continuously distributed in a carousel shape. The other is a pull-type distribution function in which the server 1 performs unicast distribution when each client 2 requests content on demand.

Each client 2 holds user profile information and uploads it to the server 1 as appropriate. The profile information includes user preference information (degree of likes and dislikes), behavior information when viewing the content, and the like. Each client 2 also individually requests content when necessary.
Here, in the wireless network 3, there is a possibility that the wireless signal may not reach the client 2 from time to time due to radio wave conditions. At this time, the receiving client 2 cannot receive one or more packets and cannot restore the original content. For this reason, in the present invention, it is assumed that packet loss occurs, and distribution data is made redundant in push-type distribution. For this reason, a function for formulating a content distribution strategy for dynamically determining the redundancy of distribution data is added to the server 1. Details will be described later.

FIG. 2 is a conceptual diagram when an erasure code, which is a type of FEC, which is a transmission error control method for detecting an error due to packet loss during transmission and performing self-repair, is applied.
Here, one original content to be transmitted is divided into R packets, and these K packets are defined as one block. At this time, the size of each packet and block is constant, and if it is less than one block size, padding processing is performed. Then, encoding processing is performed on K packets included in each block, N (≧ K) encoded data is generated, and the encoded data is distributed. Here, N / K is referred to as “redundancy” by encoding.

When the client 2 that receives the encoded data is able to receive at least K encoded data in each block that originally includes N encoded data, the block is successfully received, and the original content Can be decoded into packets. Thus, even if an error occurs during transmission and the encoded data in each block cannot be received to some extent, the client 2 can restore the original data if it can receive K or more encoded data.
On the other hand, when the reception state of the client 2 deteriorates and K pieces of encoded data in each block cannot be received, the client 2 discards the block itself. Further, the client 2 requests the same block from the server 1 on demand, and receives it after waiting for its distribution. In other words, even in an environment where packet loss frequently occurs and the number of encoded data received by the client 2 decreases, the original data can be restored by increasing the redundancy by encoding.

However, since the total number of encoded data increases, the amount of data transmission on the wireless network 3 increases and transmission efficiency decreases. That is, since there is a trade-off relationship between the redundancy by encoding and the transmission amount, it is necessary to determine an efficient redundancy. Further, when the reception environment of many clients 2 is bad, the data transmission amount by the pull type increases, and in particular, the transmission efficiency of the entire mobile phone network is deteriorated.
Therefore, as a method for determining redundancy, generally, various environments with different numbers of clients, packet loss states, and the like are assumed, so that no packet loss occurs regardless of the reception state of the client 2. Redundancy is determined in advance and always maintained. In other words, the usage status and the like are observed in units of 4 base stations, and the redundancy is determined in accordance with the state of the busiest time (worst time). However, the behaviors of users who use mobile phones or the environment around the users are diverse, not only differing from one base station 4 unit to another, but even in an area managed by one base station 4, the user may vary depending on the time of day. Since the number and the like change, setting the redundancy that always assumes the most busy time (worst time) decreases the data transmission efficiency on the wireless network 3.

  Therefore, in the present invention, the optimum redundancy is determined as needed based on the packet loss information transmitted from the client 2. That is, the server 1 sums the transmission amount of block data requested by the client 2 on demand (hereinafter referred to as “on-demand transmission amount”) and the transmission amount of data distributed by multicast (hereinafter referred to as multicast transmission amount) (hereinafter referred to as “multicast transmission amount”). , Referred to as the total transmission amount), and the redundancy that minimizes it is determined.

This will be specifically described below. Here, it is assumed that the client i (0 ≦ i ≦ M−1) already knows the redundancy parameter K, the redundancy parameter N, and the content size C, and these pieces of information are distributed as needed. Shall.
Further, it is assumed that each client 2 can always calculate the packet loss rate p _i . Here, the packet loss rate indicates the ratio of the number of packets that could not be received to the number of packets when the original content was divided.

First, push-type distribution of content is started from a certain time t ₁ . Here, if the redundancy is N (t ₁ ) / K (t ₁ ), the encoded data length is L, and the header length of the encoded data is H, the number of blocks B (t ₁ ) during transmission is as follows: This is expressed by the following equation (1).

At this time, the multicast transmission amount T (t ₁ ) is expressed by the following arithmetic expression (2). However, when encoding, the packet length before encoding and the payload length in the encoded data after encoding are not changed.

Subsequently, the server 1 simultaneously with the end of the delivery of one period of content, based on the packet loss rate p _i transmitted from the client i (step S44 “Yes”), the block loss rate I _{i of the} client 2 (T ₁ ) is estimated by the following arithmetic expression (3).
Here, when the block loss rate, relative to the number of blocks when encoding on the server, indicates the ratio of the number of blocks that the client is not received, the packet loss rate is p _i, N number of code This is equal to the probability that K or more pieces of encoded data cannot be received.

The above-mentioned arithmetic expression (3), the expected value of the number of blocks that the client i is requested on demand d _{i (t 1)} is expressed by the following expression (4).

As a result, the server 1 estimates the transmission amount D _i (t ₁ ) of the block to be distributed on demand to the client i by the following arithmetic expression (5) (step S45).

Therefore, the on-demand transmission amount U (t ₁ ) for all the clients 2 is expressed by the following arithmetic expression (6).

Next, assuming that push distribution (multicast) in the next cycle is started from time t ₂ and the redundancy at that time is changed to N (t ₂ ) / K (t ₂ ), the multicast transmission amount T (T ₂ ) is expressed by the following arithmetic expression (7).

However, the number of blocks B (t ₁ ) at the time of transmission at this time is expressed by the following arithmetic expression (8).

Therefore, the total transmission amount W (t ₂ ) on the mobile phone network at time t ₂ is expressed by the following arithmetic expression (9).

Next, the server 1 from among all combinations of N envisioned _{(t 2)} and _{K (t 2), W (} t 2) value N _{(t 2)} that minimizes the K of _{(t 2)} Calculate the combination. That is, N (t ₂ ) and K (t ₂ ) satisfy the condition of the following arithmetic expression (10).

FIG. 3 is a block diagram showing the configuration of the content distribution system according to the embodiment of the present invention, in which the internal configurations of the server and the client are respectively developed in function.
In FIG. 3, the server 1 that performs content distribution includes a database 10 (DB), an encoding operation unit 11, a complementary operation unit 12, a push-type transmission unit 13, a pull-type transmission / reception unit 14, and packet loss information collection. A unit 15, a transmission amount estimation calculation unit 16, and a redundancy degree determination calculation unit 17 are configured.

The DB 10 is a database that stores original data to be distributed to the client 2. Further, the encoding operation unit 11 encodes the original content to be multicast distributed to the client 2 stored in the DB 10 according to the distribution procedure including the redundancy specified by the redundancy determination operation unit 17 (first). Encoded data is generated and transferred to the push-type transmitter 13.
The push type transmission unit 13 multicasts the encoded data transferred from the encoding calculation unit 11 to the client 2. In addition, the complement calculation unit 12 transmits the content request from each client 2 and the content unreceived data (the second data that the client 2 could not receive when receiving the multicast data) transferred via the pull-type transmission / reception unit 14 described later. (Encoded data) request is received from the encoding operation unit 11 and transferred to the pull-type transmission / reception unit 14.

In response to a content non-reception data request and packet loss information transmission issued from the client 2, the pull type transmission / reception unit 14 transmits the corresponding data and transfers the packet loss information. Further, the packet loss information collection unit 15 transfers the packet loss information from each client 2 transferred via the pull type transmission / reception unit 14 to the transmission amount estimation calculation unit 16.
The transmission amount estimation calculation unit 16 estimates the sum of the data transmission amounts in the encoded data group that the client 2 could not receive based on the packet loss information transmitted from the client 2 along with the multicast distribution of the encoded data group. The calculation is performed and transferred to the redundancy determination calculation unit 17. The redundancy determination calculation unit 17 determines the redundancy that minimizes the sum of the data transmission amounts in the encoded data group that is distributed on demand to the client 2 and the sum of the data transmission amounts in the encoded data group that is distributed by multicast. Calculate and instruct the encoding operation unit 11.

  On the other hand, the client 2 that receives the content distributed by the server 1 includes a push type reception unit 21, a pull type transmission / reception unit 22, a decryption calculation unit 23, a packet loss information generation unit 24, and a content reproduction unit 25. Consists of.

The push-type receiving unit 21 receives a (first) encoded data group that is generated by the server 1 connected via the wireless network 3 and is multicast-distributed and encoded according to an arbitrary redundancy. To the decoding operation unit 23. The decoding calculation unit 23 decodes the first encoded data group and transfers it to the packet loss information generation unit 24 and the content reproduction unit 25.
The packet loss information generation unit 24 generates packet loss information based on the (first) encoded data that could not be decoded by the decoding calculation unit 23 and transfers the packet loss information to the pull type transmission / reception unit 22. The pull-type transmitting / receiving unit 22 transmits packet loss information as well as unreceived original content to the server 1 for an on-demand request, and is delivered on-demand by the server 1 according to the updated redundancy based on the packet loss information. The (second) encoded data corresponding to the unreceived original content to be encoded is received and transferred to the decoding calculation unit 23.

  The content reproduction unit 25 reproduces the original content output by the decryption calculation unit 23 and requests the server 1 for on-demand original content not received via the pull-type transmission / reception unit 22.

4 and 5 are flowcharts cited for explaining the operation of the content distribution system according to the embodiment of the present invention. The computer program installed in the server 1 (FIG. 4) and the client 2 (FIG. 5) is shown in FIG. Each processing procedure is also shown.
The operation of the content distribution system according to the embodiment of the present invention shown in FIG. 3 will be described in detail below with reference to the flowcharts shown in FIGS.

The operation of the server 1 shown in FIG. 4 will be described. First, the encoding calculation unit 11 acquires original content to be multicast distributed from the DB 10 under the instruction of the redundancy determination calculation unit 17, generates a (first) encoded data group based on the redundancy α, It transfers to the push type | mold transmission part 13 (step S41). The push type transmission unit 13 distributes the encoded data group transferred by the encoding calculation unit 11 by multicast (step S42).
The push-type transmitting unit 13 writes information on the redundancy α and the data amount of the original content in the header area of the encoded data group, and this encoded data group is transmitted to the client 2 connected via the wireless network 3. Is distributed by multicast.

  As a result of multicast distribution of the coded data group described above, the packet loss information generated by the client 2 is collected by the packet loss information receiving unit 15 via the pull type transmitting / receiving unit 14 (step S44 “Yes”). Here, the transmission amount estimation calculation unit 16 estimates the on-demand transmission amount by executing calculations according to the above-described arithmetic expressions (5) and (6) (step S45), and is acquired via the complementary calculation unit 12. The encoded data is distributed on demand to the requested client 2 via the pull type transmission / reception unit 14 (step S46).

The redundancy determination calculation unit 17 simultaneously distributes the sum of the data transmission amount in the (second) encoded data group to be distributed to the client 2 on-demand to the client 2 simultaneously with the end of the distribution of the content for one period described above, and multicast distribution. The redundancy α that minimizes the total amount of data transmission in the (first) encoded data group is calculated, and is instructed to the encoding calculation unit 11 each time. This is reflected in the generation (step S47).
In other words, the redundancy degree determination calculation unit 17 executes the calculation according to the above equation (10), and dynamically determines the redundancy α that minimizes the sum of the on-demand transmission amount and the multicast transmission amount, so that the client The amount of data transmission on the on-demand side is reduced according to the packet loss situation. The above processing is repeated until the content distribution is completed (step S43 “Yes”).

Next, the operation of the client 2 functioning as a content receiving apparatus will be described with reference to the flowchart shown in FIG.
First, the encoded data group multicast-distributed by the server 1 is received by the push-type receiving unit 21 and transferred to the decoding calculation unit 23 (step S51).
The decoding calculation unit 23 refers to the information written in the header area of the (first) encoded data group received by the push type receiving unit 21 and uses the redundancy α used when encoding the original content. And the data amount of the original content, and the received (first) encoded data group is decoded based on the information and transferred to the packet loss information generation unit 24 and the transmission / reception content reproduction unit 25 (step S52). .

  At this time, the packet loss information generation unit 24 generates packet loss information based on the encoded data group when there is an encoded data group that cannot be decoded by the decoding calculation unit 23 (step S53 “Yes”). Then, the data is transmitted to the server 1 via the pull type transmission / reception unit 22 (step S54). That is, the packet loss information generation unit 24 obtains the ratio of the number of packets that could not be received with respect to the number of packets that constitute the content, based on the redundancy α and the data amount of the content acquired through the decoding calculation unit 23. And packet loss information is generated and transferred to the pull-type transceiver 22. Further, the content reproduction unit 25 issues an on-demand request for packet loss information to the server 1 via the pull type transmission / reception unit 22 based on the data transferred from the decryption calculation unit 23 (step S55).

The pull type transmission / reception unit 22 transmits the packet loss information generated by the packet loss information generation unit 24 and the unreceived original content to the server 1 for an on-demand request. Then, the (second) encoded data group corresponding to the unreceived original content encoded with the redundancy β updated based on the packet loss information and distributed on demand by the server 1 is received (step S56). “Yes”), the data is transferred to the decoding operation unit 23.
The encoding operation unit 23 performs a decoding process on the received (second) encoded data group and transfers the decoded data group to the content reproduction unit 25. Then, the content reproduction unit 25 reproduces the original content output by the decryption calculation unit 23 (Step S57).

As described above, the present invention is a content distribution system that uses both multicast distribution and on-demand distribution in the wireless network 3, and takes measures against packet loss by adding redundancy to multicast distribution data. It is. At this time, although the data transmission amount on the wireless network 3 is increased by adding the redundancy, the server 1 is turned on by dynamically controlling the redundancy according to the packet loss situation of the client 2. The data transmission amount for demand distribution can be reduced, and as a result, the total transmission amount on the network can be reduced.
Further, according to the present invention, it is possible to realize a packet loss countermeasure at the application layer using packet loss information that cannot be grasped at the network layer. For this reason, a particularly remarkable effect can be obtained when used for content distribution in a wireless network in which the reception status of the client changes due to various factors such as time, place, and application.

  In addition, the encoding calculating part 11, the complement calculating part 12, the push type | mold transmission part 13, the pull type | mold transmission / reception part 14, the packet loss information collection part 15, the transmission amount estimation calculating part 16, and the redundancy determination calculating part 17 shown in FIG. , The push type receiving unit 21, the pull type transmitting / receiving unit 22, the decoding calculation unit 23, the packet loss information generating unit 24, and the content reproducing unit 25 are recorded on a computer-readable recording medium, and this recording is performed. By executing the program recorded on the medium, the content distribution device, the content reception device, and the content distribution system of the present invention can be realized. 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 embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

It is a figure which shows the system configuration | structure and operation | movement concept of the content delivery system which concern on embodiment of this invention. It is a figure which shows the concept of the transmission error control system FEC used in the content delivery system which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of the content delivery system which concerns on embodiment of this invention. It is the flowchart quoted in order to demonstrate operation | movement of the content delivery system (server) which concerns on embodiment of this invention. It is the flowchart quoted in order to demonstrate operation | movement of the content delivery system (client) which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Server (content delivery apparatus), 2 ... Client (content receiving apparatus), 3 ... Wireless network, 4 ... Base station, 11 ... Encoding calculating part, 12 ... Complementary calculating part, 13 ... Push type | mold transmission part, 14 ... Pull type transmission / reception unit, 15 ... Packet loss information collection unit, 16 ... Transmission amount estimation calculation unit, 17 ... Redundancy determination calculation unit, 21 ... Push type reception unit, 22 ... Pull type transmission / reception unit, 23 ... Decoding calculation unit, 24 ... Packet loss information generation unit, 25 ... Content playback unit

Claims (9)

A content distribution device that distributes content by using both multicast distribution and on-demand distribution in a wireless network,
An encoding operation unit that generates a first encoded data group according to an arbitrary redundancy with respect to the original content;
The content distribution device is a push-type transmission unit that multicast-distributes the first encoded data group to a content reception device connected via the wireless network;
The total amount of data transmission in the second encoded data group that could not be received by the content receiving device based on the packet loss information transmitted from the content receiving device due to multicast distribution of the first encoded data group A transmission amount estimation calculation unit for performing calculation to estimate
A pull-type transmission unit that performs on-demand distribution of the second encoded data group to all of the content reception devices;
A redundancy determination calculation unit that updates the redundancy used for the first encoded data group generation by the encoding calculation unit based on the total transmission amount in the second encoded data group;
A content distribution apparatus comprising: The redundancy determination calculation unit includes:
Redundancy that minimizes the total amount of data transmission in the second encoded data group that is distributed on-demand to the content receiving apparatus and the total amount of data transmission in the first encoded data group that is distributed by multicast The content distribution apparatus according to claim 1, wherein the degree is calculated. The push-type transmitter is
Information on the updated redundancy and the data amount of the original content is written in a predetermined area in the first encoded data group, and the first content receiver connected via the wireless network has the first 2. The content distribution apparatus according to claim 1, wherein the encoded data group is distributed by multicast. A content receiving device that receives content by using both multicast distribution and on-demand distribution in a wireless network,
The content receiving device is a push type that receives a first encoded data group that is generated by a content distribution device connected via the wireless network and is multicast distributed, and is obtained by encoding original content according to an arbitrary redundancy. A receiver,
A decoding operation unit for decoding the first encoded data group and transferring the decoded encoded data group to a content reproduction unit;
A packet loss information generation unit that generates packet loss information based on the first encoded data that could not be decoded by the decoding operation unit;
The packet loss information as well as the unreceived original content is transmitted to the content distribution device for an on-demand request, and is distributed on-demand by the content distribution device, and is encoded with the redundancy updated based on the packet loss information A pull-type transmission / reception unit that receives second encoded data corresponding to the unreceived original content to be converted, and transfers the second encoded data to the decoding calculation unit;
A content reproduction unit that reproduces the original content output by the decryption calculation unit and requests the content distribution device to request the unreceived original content via the pull-type transmission / reception unit;
A content receiving apparatus comprising: The decoding operation unit
The redundancy used when encoding the original content with reference to information written in a predetermined area in the first encoded data received by the push type receiving unit, and the data amount of the original content The content receiving apparatus according to claim 4, wherein: The packet loss information generation unit
Based on the redundancy and the data amount of the content obtained through the decoding operation unit, a ratio of the number of packets that could not be received to the number of packets that constitute the content is obtained, and the packet loss information is obtained. The content receiving apparatus according to claim 4, wherein the content receiving apparatus is generated. A content distribution system that distributes content using both multicast distribution and on-demand distribution in a wireless network,
An encoding operation unit that generates a first encoded data group according to an arbitrary redundancy for the original content, and the content distribution device connected to the content distribution device via the wireless network Push type transmission unit for multicast distribution of encoded data group, and the content reception apparatus could not receive based on packet loss information notified from the content reception apparatus due to multicast distribution of the first encoded data group A transmission amount estimation calculation unit that performs a calculation for estimating the total amount of data transmission in the second encoded data group, and a pull type that performs on-demand distribution of the second encoded data group to all of the content receiving devices Based on the sum of the amount of data transmission in the transmission unit and the second encoded data group, a first unit by the encoding unit Redundancy determination operation unit for updating the redundancy to be used in No. data set generator, a content distribution apparatus consisting of,
A push-type receiving unit that receives the first encoded data group, which is generated by the content distribution device and distributed by multicast, and a decoding unit that decodes the received first encoded data group and transfers the decoded group to the content reproduction unit On-demand request for packet loss information generation unit for generating packet loss information based on the first encoded data that could not be decoded by the decoding calculation unit, the packet loss information, and unreceived original content Second content corresponding to the unreceived original content encoded with redundancy updated based on the packet loss information, transmitted to the content distribution device for delivery on demand by the content distribution device A pull-type transceiver unit that receives encoded data and transfers the encoded data to the decoding operation unit; To reproduce the original content output by the section, and a content receiving apparatus comprising the original content of the non-received from the content reproduction unit, to request on-demand to the content delivery apparatus via the pull-type transmission and reception unit,
A content distribution system comprising: A computer program used for a content distribution apparatus that distributes content by using both multicast distribution and on-demand distribution in a wireless network,
A process of generating a first encoded data group according to an arbitrary redundancy for the original content;
The content distribution device is a multicast distribution of the first encoded data group to a content reception device connected via the wireless network;
The total amount of data transmission in the second encoded data group that could not be received by the content receiving device based on the packet loss information notified from the content receiving device due to the multicast distribution of the first encoded data group Processing for estimating
A process of performing on-demand distribution of the second encoded data group to all of the content receiving devices;
A process of updating the redundancy used for generating the first encoded data group based on the total amount of data transmission in the second encoded data group;
A computer program that causes a computer to execute. A computer program used in a content receiving apparatus for receiving content by using both multicast distribution and on-demand distribution in a wireless network,
The content receiving device is a process of receiving a first encoded data group generated by a content distribution device connected via the wireless network and multicast-distributed and encoded original content according to an arbitrary redundancy. ,
A process of decoding the first encoded data group;
A process of generating packet loss information based on the first encoded data that could not be decoded;
The packet loss information as well as the unreceived original content is transmitted to the content distribution device for an on-demand request, and is encoded by the updated redundancy based on the packet loss information distributed on-demand by the content distribution device. Processing to receive second encoded data corresponding to the unreceived original content that has been converted to
A process of playing back the original content generated as a result of the decryption and requesting the undelivered original content to the content distribution device via the pull-type transmission / reception unit;
A computer program that causes a computer to execute.

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