KR101241507B1 - Cache system and cache allocation method for content on demand service using multicast - Google Patents

Abstract

PURPOSE: A cache system and a cache allocation method for a content-on-demand service using a multicast is provided to store the front part of the popular content having a high content exposure rate, transmit the front part of the content from the cache server to a unicast, and transmit the other part from a server to a multicast. CONSTITUTION: A content providing system determines data length of near content-on-demand content to be stored in a cache server(610). If a multicast transmission cost is less than a unicast transmission cost, the system orders to store data as long as the cache length of corresponding content in the cache server(630,640). The system generates a transmission schedule mixing the cache server and a source server(650). According to the transmission schedule, the system transmits a partial stream corresponding to the first part of the content in the unicast mode. The system transmits the stream in a multicast mode(680). [Reference numerals] (610) Calculating a cache length(l) by using related information of contents; (620) Calculating a multicast transmission cost(Cm) and a unicast transmission cost(Cu) according to the cache length(l); (640) Ordering to store the initial part of the contents as long as the cache length(l) in a server; (650) Generating a transmission schedule mixing an original server and a cache server; (660) Deleting an existing cache stored in the cache server; (670) Generating a transmission schedule using the original server; (680) Controlling to transmit corresponding contents according to the transmission schedule; (AA) Start; (BB) No; (CC) Yes; (DD) End

Description

CACHE SYSTEM AND CACHE ALLOCATION METHOD FOR CONTENT ON DEMAND SERVICE USING MULTICAST}

Embodiments of the present invention relate to a content providing system and method for providing a portion of content through a cache when providing an on-demand content service using multicast.

This study was conducted as a result of the research project supported by the IT Research Center of the Ministry of Knowledge Economy and the Korea IT Industry Promotion Agency. (NIPA-2011- (C1090-1111-0013))

With the recent widening of network and development of broadcasting technology, CoD (Content-on-Demand) service is attracting much attention as a new value-added industry. CoD is a two-way system that can provide video data such as movies, education, games, and shopping, which are being stored in digital data, to multiple users over a long distance using a communication network. On-demand content is a collection of large-capacity data such as video and voice, and many data must be transmitted even after compression. When transmitting this over a network, a very large channel bandwidth is required, and a considerable amount of cost is required to secure the bandwidth. Therefore, efficient use of the bandwidth is required.

CoD is classified into real-time on-demand content (TCoD: True-CoD) and similar on-demand content (NCoD: Near-CoD) according to the method of transmitting the content. Among them, TCoD is an interactive service that provides various multimedia services to the user through a unicast transmission method in which a user can select and watch a desired program at a desired time. TCoD has the advantage of interactive service, but since the user occupies the transport channel from the content server to the user's end, it requires a lot of bandwidth to provide the service and a lot of cost. NCoD, on the other hand, instead of sacrificing the interactive service function and the user's waiting time, NCoD repeats one content sequentially through several broadcasting channels. NCoD drastically reduced system costs by allowing multiple users to simultaneously access content using one channel. NCoD requires significantly fewer channels than TCoD, but the disadvantage is that many users do not see the requested content immediately.

 As described above, there are two methods of transmitting content, a unicast method of 1: 1 transmission and a multicast method of 1: N transmission. In NCoD service, there is a method of reducing transmission bandwidth of a server by dividing the multicast stream into one or more and repeatedly. However, when only multicast is used in NCoD, a user participating in a multicast group during content transmission misses the front of the content. That is, the waiting time for starting content may be long because it is necessary to wait until the beginning of content in the multicast stream.

In order to solve this problem, a method of transmitting content by using a mix of unicast and multicast has been proposed. In addition, a plurality of cache servers are used in order to reduce the start waiting time and the channel change waiting time of the on-demand content service using multicast. However, the storage capacity of the cache server is limited to the installation and expansion in consideration of cost issues. Accordingly, there is a need for a cache allocation method to provide the best quality service within the limited storage space.

Provided are a system and method for allocating cache for each content in an on-demand content service environment in which a multicast scheme and a unicast scheme are mixed.

The present invention provides a system and method for storing the front of popular content having a high content rate in a cache server.

Provided is a system and method for reducing content start waiting time due to multicast join waiting time, which is a disadvantage of a similar on-demand content service environment.

Provided are a system and method that can alleviate the bandwidth burden of a server providing on-demand content.

A content providing method for providing near-content-on-demand includes determining a data length to be stored in a cache server for the similar-on-demand content; Retrieving a partial stream of a data length from a source server in which similar on-demand content is stored and storing the same on a cache server; And transmitting some streams from the cache server in a unicast manner and transmitting the remaining streams from the origin server in a multicast manner when a user terminal requests similar content on demand.

According to an aspect, the determining of the data length may determine the data length by using the reproduction speed of the similar on-demand content, the total data length, and the content request rate.

According to another aspect, the content providing method may further include calculating a multicast transmission cost and a unicast transmission cost according to the data length. In this case, in the step of taking some streams and storing them in the cache server, if the multicast transmission cost is smaller than the unicast transmission cost, some streams may be stored in the cache server.

According to another aspect, in the content providing method, if the multicast transmission cost is greater than the unicast transmission cost, transmitting some streams and the remaining streams from the origin server to the user terminal at the request of the user terminal for the similar on-demand content. It may further include.

Content providing method for providing similar on-demand content includes the steps of determining the data length to be stored in the cache server for the similar on-demand content; Calculating a multicast transmission cost and a unicast transmission cost according to the data length; Generating a transmission schedule for the similar on-demand content according to a result of comparing the multicast transmission cost with the unicast transmission cost; And transmitting a partial stream as much as the data length in a unicast manner and transmitting the remaining streams in a multicast manner according to a transmission schedule when a user terminal requests similar content on demand.

Content providing system for providing similar on-demand content includes a source server that stores similar on-demand content; A control server for determining a data length to be stored in the cache server by using a reproduction speed of the similar on-demand content, total data length, and content request rate; And a cache server that obtains and stores some streams as long as the data length from the source server, wherein the control server transmits some streams in a unicast manner when a user terminal requests similar content on demand. A transmission schedule can be created to transmit in a multicast manner.

By storing the first part of the popular content with high content arrival rate in the cache server, it is possible to provide the best quality service by transmitting the first part of the content from the cache server to the unicast sheet and the remaining part from the origin server by multicast.

In the on-demand content service environment, which is a mix of multicast and unicast methods, a transmission schedule for the content is generated in consideration of the content transmission cost according to the content cache length, thereby effectively reducing the bandwidth burden of the server providing the on-demand content. have.

1 is a flowchart illustrating an on-demand content service procedure.
2 to 4 are diagrams illustrating a service structure in which multicast and unicast are combined.
FIG. 5 is a diagram illustrating a service structure of a content providing system for providing on-demand content through cache allocation according to an embodiment of the present invention.
6 is a flowchart illustrating a content providing method for providing on-demand content through cache allocation according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments are based on an on-demand content service environment. 1 is a flowchart illustrating one form of an on-demand content service structure. The service procedure shown in FIG. 1 is intended for IPTV, but is not limited thereto, and is intended for all terminals capable of consuming on-demand content.

As shown in FIG. 1, the on-demand content service may include the following procedure.

(1) A user connects to a content providing server by using an IPTV terminal.

(2) A web application functional block (hereinafter referred to as a 'web application block') on the content providing server side transmits an approval message (OK) for access to the user's IPTV terminal.

(3) The IPTV terminal searches for and selects a service or content using an IPG (interaction program guide) or an EPG (electronic program guide).

(4) The web application block requests the authority for the IPTV terminal with content deliver & service control functions (hereinafter, referred to as a 'service control block') in a content providing server.

(5) The service control block checks the authority for the IPTV terminal and transmits a response message to the authority request to the web application block.

(6) The web application block sends a response message of the service control block to the IPTV terminal.

(7) The IPTV terminal transmits a request signal for the service URL or the content URL to the service control block.

(8) The service control block requests an IPTV terminal function (ITF) from a network provider for an on-demand content service.

(9) The network provider provides location information for the ITF.

(10) The service control block allocates CD & SF capabilities using location information about the ITF.

(11) The service control block requests network resource allocation from a network provider.

(12) The network provider allocates network resources.

(13) The network provider transmits a response message to the request for allocation of network resources to the service control block.

(14) The service control block sends a response to the service URL or content URL request to the IPTV terminal.

(15) The IPTV terminal transmits a play message to the service control block.

(16) The service control block starts the content transmission after sending the approval message to the IPTV terminal.

(17) When the user finishes viewing the content, the IPTV terminal transmits an end message to the service control block.

(18) The service control block releases CD & SF performance.

(19) The service control block transmits a request signal for releasing network resources to the network provider.

(20) The network provider releases network resources.

(21) The network provider sends a response message to the network resource release request to the service control block.

(22) The service control block sends a response message to the service completion to the IPTV terminal.

(23) The IPTV terminal transmits a connection release message to the web application block.

(24) The web application block transmits a response message to the connection release request to the IPTV terminal.

Embodiments of the present invention provide a content providing system and method for implementing the procedure related to (16) in the on-demand content service environment described above. In particular, the present invention is applicable to a service environment in which a multicast transmission method and a unicast transmission method are combined.

2 to 4 are diagrams illustrating a service structure in which multicast and unicast are combined.

As shown, in a similar on-demand content service environment, such as staggered broadcasting (FIG. 2), fast broadcasting (FIG. 3), harmonic broadcasting (FIG. 4), and the like. In order to reduce the start waiting time and the channel change waiting time of the user, the front part of the content requested by the user may be transmitted by unicast transmission.

In particular, in the present embodiment, the cache is allocated for each content to store the front parts 201, 301 and 401 of the content in the cache, and then the front parts 201, 301 and 401 of the content from the cache are unicast. And the rest can be sent multicast from the origin server.

5 and 6, a content providing system and method through cache allocation will be described in detail.

5 is a diagram illustrating a service structure of a content providing system that provides on-demand content through cache allocation.

As shown in FIG. 5, the content providing system 500 according to an exemplary embodiment may be implemented with an original server 510, a control server 520, and a cache server 530.

The origin server 510 serves as a database system for storing and maintaining similar on-demand content. If the source server 510 is to provide similar on-demand content to the user, basically, the transport stream corresponding to the content is transmitted by repetitive multicast transmission method, and at the same time, the first part of the content is unicast transmission method. Can be sent. For example, when the origin server 510 joins a specific multicast group that is transmitting the content requested by the user, the original server 510 may transmit some streams corresponding to the first part of the content as unicast and transmit the remaining streams as multicast.

The cache server 530 stores and maintains some streams of similar on-demand content to be transmitted in unicast. In the present embodiment, a cache may be allocated for each content to store a part of the content in the cache server 530. This is to use the cache server 530 in some cases because the source server 510 has a limitation in reducing the start wait time and the channel change wait time of the content when the content is mixed and transmitted by unicast and multicast. to be. Therefore, the origin server 510 may be responsible for multicast based content transmission, and the cache server 530 may be responsible for unicast based patch (ie, cached data) transmission.

The control server 520 is responsible for cache allocation and transmission schedule generation for similar on-demand content. First, the control server 520 allocates a cache for each similar on-demand content based on the service state information of the original server 510, and then transfers a cache storage command to the cache server 530. In detail, the control server 520 uses the bit rate, the full data length, and the content request rate of the content for each content stored in the original server 510 to cache the server 530. The length of data to be stored in (hereinafter referred to as 'cache length') can be determined. In this case, the content request rate may mean a content reach rate indicating the percentage of users who have requested a service for the corresponding content. For example, the control server 520 may calculate the cache length by using Equation 1 below.

Where l is the cache length, L is the total data length of the content, and N 'is the argument that minimizes the cost of the multicast scheme.

In addition, the control server 520 transmits data corresponding to the cache length in a multicast method (hereinafter, referred to as a multicast transmission cost C _m ) and a unicast method. The transmission cost (hereinafter referred to as 'unicast transmission cost C _u ') is calculated. In this case, the control server 520 may calculate the unicast transmission cost (C _u ) using Equation 2, and in the case of the multicast transmission cost, any of Equations 3 to 5 according to the transmission method used in the system It can be calculated through one equation.

Where b is the playback speed, L is the total data length, and λ is the content request rate.

Here, _Chm is a multicast transmission cost according to the harmonic transmission method, and Nh 'is a factor for minimizing the cost of the multicast method.

Here, C _fm is a multicast transmission cost according to the fast transmission method, and Nf 'is a factor for minimizing the cost of the multicast method.

Here, C _sm is a multicast transmission cost according to the staggered transmission method, and Ns' is a factor for minimizing the cost of the multicast method.

The control server 520 then compares the multicast transmission cost C _m and the unicast transmission cost C _u . Accordingly, the control server 520 stores the data in the cache server 530 as much as the previously determined cache length, which is the first part of the content, if the multicast transmission cost C _m is less than the unicast transmission cost C _u . Command At this time, the cache server 530 may request the source server 510 according to the command of the control server 520 to retrieve the cache length data (hereinafter referred to as 'some stream') from the source server 510 and store it. have. On the other hand, the control server 520 de-allocates and caches the content because it is more efficient to send directly from the origin server 510 if the multicast transmission cost (C _m ) is greater than the unicast transmission cost (C _u ). If there is an existing cache of the corresponding content in the server 530, it is deleted. Accordingly, the control server 520 may calculate the cache length for each content and then determine whether to allocate the cache based on the multicast transmission cost for the corresponding cache length.

Next, the control server 520 may generate a transmission schedule according to cache allocation for the similar on-demand content. Basically, the control server 520 generates a transmission schedule to transmit some streams corresponding to the first part of the content in a unicast manner and transmit the remaining streams in a multicast manner. In addition, the control server 520 transmits some streams of content from the cache server 530 when the cache allocation is made according to the comparison result of the multicast transmission cost (C _m ) and the unicast transmission cost (C _u ). The transmission schedule may be generated and stored to transmit the stream from the origin server 510. On the other hand, if the cache allocation is released according to the result of comparing the multicast transmission cost (C _m ) and the unicast transmission cost (C _u ), the control server 520 transmits all the streams of the content and the remaining streams from the source server 510. The transmission schedule can be created and stored.

According to the above configuration, the source server 510 transmits some streams of the content in unicast according to the transmission schedule generated by the control server 520 at the request of the user terminal for the similar on-demand content, and simultaneously multiplies the remaining streams. The content requested by the user may be provided by one of the methods of transmitting the content by a cast or by transmitting some stream of the content as unicast from the cache server 530 and transmitting the remaining stream as multicast from the origin server 510. Can be. Accordingly, the user terminal may immediately start playing some streams received in the unicast manner, and at the same time, the remaining streams received in the multicast manner may be temporarily stored in a buffer and then start playing after some streams.

6 is a flowchart illustrating a content providing method for providing on-demand content through cache allocation according to an embodiment of the present invention. In the content providing method according to an exemplary embodiment, each step may be performed by the content providing system described with reference to FIG. 5.

In step 610, the content providing system determines the data length, that is, the cache length for which cache allocation is required, using the related information of each content for each similar-demand content. In this case, the content providing system may determine the cache length using the content reproduction speed, the total data length, and the content request rate.

In step 620, the content providing system calculates the multicast transmission cost (C _m ) and unicast transmission cost (C _u ) for the data corresponding to the cache length. That is, the content providing system can calculate the transmission cost when transmitting data corresponding to the cache length by the multicast method and the transmission cost when transmitting by the unicast method.

In step 630, the content providing system compares the multicast transmission cost (C _m ) and the unicast transmission cost (C _u ) for the data corresponding to the cache length.

In step 640, the content providing system instructs the cache server to store as much data as the cache length in the content if the multicast transmission cost C _m is less than the unicast transmission cost C _u . At this time, the cache server may request the source server that stores the content and store some streams corresponding to the first part of the content as much as the cache length from the source server.

In step 650, the content providing system transmits some streams of content from the cache server to the unicast when the cache allocation is made according to the comparison result of the multicast transmission cost (C _m ) and the unicast transmission cost (C _u ), You can create a transmission schedule that mixes the cache server and the origin server to send the remaining streams from the origin server to multicast.

In step 660, the content providing system deassigns the cache for the content and sends it to the cache server because it is more efficient to send directly from the origin server if the multicast transmission cost (C _m ) is greater than the unicast transmission cost (C _u ). If there is an existing cache of the content, delete it.

In step 670, the content providing system, if the cache is deallocated according to the result of the comparison of the multicast transmission cost (C _m ) and the unicast transmission cost (C _u ), both the source stream and the remaining streams are transmitted from the origin server. A transmission schedule using only a server can be created.

In step 680, the content providing system transmits some streams corresponding to the first part of the content in a unicast manner and transmits the remaining streams in a multicast manner according to a transmission schedule of the corresponding content when a user terminal requests similar content on demand. Can transmit In other words, the content providing system transmits some streams of the content and all remaining streams from the origin server according to the transmission schedule generated for the similar on-demand content, or transmits some streams of the content from the cache server and sends the remaining streams to the origin server. The content requested by the user may be provided in one of the forms of transmission by the user.

As described above, according to an embodiment of the present invention, by storing the front part of the popular content having a high content arrival rate in the cache server, the front part of the content is transmitted from the cache server to the unicast sheet, and the remaining part is multicasted from the origin server. To provide the highest quality service. In addition, according to an embodiment of the present invention, in the on-demand content service environment in which the multicast scheme and the unicast scheme are mixed, providing on-demand content by generating a transmission schedule for the content in consideration of the content transmission cost according to the content cache length You can effectively reduce the bandwidth burden on the server.

Methods according to an embodiment of the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. In addition, the above-described file system can be recorded in a computer-readable recording medium.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

500: content providing system
510: source server
520: control server
530: cache server

Claims (11)

In the content providing method for providing a near-content-on-demand,
Determining a data length to be stored in a cache server for the similar on-demand content;
Retrieving a partial stream as long as the data length from a source server in which the similar on-demand content is stored and storing in the cache server; And
Transmitting the partial stream in the unicast method from the cache server and transmitting the remaining stream in the multicast method from the origin server at the request of the user terminal for the similar on-demand content.
Content providing method comprising a. The method of claim 1,
Determining the data length,
Determining the data length using the reproduction speed of the pseudo-custom content and the total data length and content request rate.
Content providing method characterized in that. The method of claim 1,
The content providing method,
Calculating a multicast transmission cost and a unicast transmission cost according to the data length
Further comprising:
Obtaining the partial stream and storing in the cache server,
Storing the partial stream in the cache server if the multicast transmission cost is less than the unicast transmission cost.
Content providing method characterized in that. The method of claim 3,
The content providing method,
If the multicast transmission cost is greater than the unicast transmission cost, transmitting the partial stream and the remaining stream from the origin server to the user terminal at the request of the user terminal for the similar on-demand content.
Content providing method further comprising. In the content providing method for providing similar on-demand content,
Determining a data length to be stored in a cache server for the similar on-demand content;
Calculating a multicast transmission cost and a unicast transmission cost according to the data length;
Generating a transmission schedule for the similar on-demand content according to a result of comparing the multicast transmission cost with the unicast transmission cost; And
Transmitting some streams of the data length in a unicast manner and transmitting the remaining streams in a multicast manner according to the transmission schedule when a user terminal requests the similar on-demand content.
Content providing method comprising a. The method of claim 5,
Determining the data length,
Determining the data length using the reproduction speed of the pseudo-custom content and the total data length and content request rate.
Content providing method characterized in that. The method of claim 5,
Generating a transmission schedule for the similar on-demand content,
If the multicast transmission cost is less than the unicast transmission cost, retrieving the partial stream from a source server storing the similar on-demand content and storing the stream in the cache server; And
Generating the transmission schedule to transmit the partial stream from the cache server to the user terminal and transmit the remaining stream from the origin server
Content providing method comprising a. The method of claim 7, wherein
Generating a transmission schedule for the similar on-demand content,
If the multicast transmission cost is greater than the unicast transmission cost, deleting the partial stream stored in the cache server; And
Generating the transmission schedule to transmit the partial stream and the remaining stream from the source server to the user terminal;
Content providing method further comprising. In the content providing system for providing similar on-demand content,
An original server storing the similar on-demand content;
A control server for determining a data length to be stored in a cache server by using a reproduction speed of the pseudo-custom content and a total data length and a content request rate; And
The cache server for retrieving and storing a partial stream of the data length from the origin server
Including,
Wherein the control server comprises:
Generating a transmission schedule to transmit the partial streams in a unicast manner and transmit the remaining streams in a multicast manner when a user terminal requests the similar on-demand content;
Content providing system, characterized in that. 10. The method of claim 9,
Wherein the control server comprises:
After calculating the multicast transmission cost and the unicast transmission cost according to the data length, if the multicast transmission cost is less than the unicast transmission cost, the partial stream is transmitted from the cache server to the user terminal Generating the transmission schedule to transmit the remaining stream from the origin server.
Content providing system, characterized in that. The method of claim 10,
Wherein the control server comprises:
If the multicast transmission cost is greater than the unicast transmission cost, generating the transmission schedule to transmit the partial stream and the remaining stream from the origin server to the user terminal;
Content providing system, characterized in that.

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