KR102120660B1 - Content cachhing mehtod using mobile cache - Google Patents

Abstract

A content caching method using at least one mobile helper having mobility within a wireless communication cell coverage by a base station is provided. Here, the mobile helper performs content provision through D2D (Device to Device) communication in relation to a plurality of general communication terminals existing in the cell coverage. Content caching method according to an embodiment of the present invention, (a) dividing the requested content in chunks (chunk) unit; (b) calculating D2D communication coverage for each chunk in consideration of content consumption time; (c) rearranging the content preference in chunk units by reflecting the calculated D2D communication coverage for each chunk; (d) determining a priority for each chunk to be stored in the cache of the mobile helper based on the content preferences rearranged in chunk units.

Description

Content caching method using mobility cache {CONTENT CACHHING MEHTOD USING MOBILE CACHE}

The present invention is to effectively support a number of MTC (Machine Type Communication) devices when implementing the Internet of Things (IoT) environment in a next-generation mobile communication system, and relates to a content caching method utilizing mobility characteristics of a cache having mobility. .

Recently, data traffic in wired and wireless networks has exploded. This can be seen as a result of content-based services. With the increase in video on demand (VOD) or over the top (OOT) streaming services, video data traffic accounts for a very large portion of total data traffic. And by 2020, more than three-quarters of all data traffic on mobile communications is expected to be caused by video content. Soaring data traffic can place a strain on the network, and in wired networks, caches are often geographically distributed to reduce bottlenecks in the core network.

In a wireless network, a bottleneck may occur in a radio resource utilized between a base station and a general user, that is, a base station and a device, unlike a wired network. While the backhaul of the base station is connected by an optical cable, it has sufficient backhaul throughput, but in a wireless network, when the number of users and requests rapidly increases, it may occur when radio resources such as frequencies used by the base station become insufficient. , This can lead to bottlenecks.

1 shows a case where a bottleneck occurs in a radio resource between a base station and a device in a wireless network. If a request is made from a larger number of devices than a request that can be handled by radio resources (①, ②, ③, ④) that the base station can use, the radio resource available to the base station is insufficient to prevent a response to the request. do. Conventionally, methods to improve the bottleneck have been applied by increasing bandwidth efficiency, using a new frequency band, and increasing a network density, but there are limits on radio resources and frequencies below 6 GHz There is very little available. Also, in the case of the millimeter wave (mmWave) band, it is not suitable to support a relatively large macro cell connected by an optical cable due to its high frequency characteristics, and there is a limitation in that a dense network is already formed. As with a wired network, a method of easing the bottleneck using cache is being considered.

The cache can be deployed at a base station or device. When the cache is placed in the base station, it has the advantage of being able to install a large cache because it has a larger storage space than the device, but may not be suitable to solve the bottleneck between the base station and the device. Accordingly, a case in which a cache is installed in a device may be considered. In a case where the cache is installed in a device, the overall cache size may be increased as the number of devices increases at a specific time and place where a user is densely packed. In addition, the device can utilize its own application program to easily extract information such as content preference and mobility, as well as provide content to other devices by utilizing D2D (Device to Device) communication. However, many devices, such as smartphones owned by a user, are difficult to secure a cache of sufficient size, and there are limitations that it may be difficult to provide content to other devices because of a limited battery. Since it is difficult to install and operate a sufficient cache on all devices, some devices that provide content to other devices through D2D communication at a cellular peak time when data traffic is rapidly increasing due to a large cache are called helpers. The helper is classified into a mobile helper, a nomadic helper, and a fixed helper depending on the mobility.

An object of the present invention is to solve a bottleneck of a wireless network by processing more user requests by selecting content to be cached in consideration of the mobility characteristics of a mobile helper.

According to an aspect of the present invention, a content caching method using at least one mobile helper having mobility within a wireless communication cell coverage by a base station is provided. Here, the mobile helper performs content provision through D2D (Device to Device) communication in relation to a plurality of general communication terminals existing in the cell coverage.

Content caching method according to an embodiment of the present invention, (a) classifying the requested content in chunks (chunk) unit; (b) calculating D2D communication coverage for each chunk in consideration of content consumption time; (c) rearranging the content preference in chunk units by reflecting the calculated D2D communication coverage for each chunk; (d) determining a priority for each chunk to be stored in the cache of the mobile helper based on the content preferences rearranged in chunk units.

Here, the step (b) is a method in which the communication coverage addition for the spare time determined by the movement speed as the content consumption time for each chunk and the movement speed of the mobile helper is added to the basic communication coverage in which the D2D communication is performed. , D2D communication coverage for each chunk may be calculated.

Here, in step (c), the initial preference of the corresponding content according to the common content preference is multiplied by the coverage expansion ratio compared to the basic communication coverage according to the calculated D2D communication coverage for each chunk, and the content preference in units of chunks is calculated. It may further include a step.

Here, the provision of content through the device to device (D2D) communication is executed when self-offloading from the self-cache in the general communication terminal fails, to consider the D2D communication coverage calculated through step (b). When the D2D communication is possible with the general communication terminal, the mobile helper may be configured in the chunk unit.

Here, the D2D communication may be performed by a D2D underlay communication method.

According to another aspect of the present invention, a recording medium product in which the above-described content caching method is recorded and readable by a computer is provided.

According to a content caching method using a cache having mobility according to an embodiment of the present invention, when the cache is mobile, the probability of offloading content through D2D communication increases, and long content must be provided There is an advantage that caching and offloading can occur more effectively. In addition, when a general user requests a content, if there is a free time to wait for delivery of content from the mobile helper, the content must be provided from the helper only within the free time, so content caching efficiency using D2D communication There is an effect that can be greatly improved.

1 is an exemplary diagram for explaining a bottleneck in a wireless network.
Figure 2 is an exemplary view for explaining a three-stage offloading method applicable to the present invention.
3 is a flowchart illustrating a content caching method considering mobility of a helper according to an embodiment of the present invention.
FIG. 4 is an exemplary diagram for explaining chunking of content and D2D coverage change for each chunk.
5 is an exemplary diagram for explaining a method of caching content for each chunk using a mobile helper.
6 is a simulation graph showing the degree of offloading according to the moving speed of the helper.
7 is a simulation graph showing the degree of offloading according to the content length.

The present invention can be applied to various transformations and may have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all conversions, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing the present invention, when it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, the numbers (for example, first, second, etc.) used in the description process of the present specification are only identification symbols for distinguishing one component from other components.

Also, in the specification, when one component is referred to as "connected" or "connected" with another component, the one component may be directly connected to the other component, or may be directly connected, but in particular It should be understood that, as long as there is no objection to the contrary, it may or may be connected via another component in the middle.

In addition, throughout the specification, when a part “includes” a certain component, this means that other components may be further included instead of excluding other components, unless specifically stated otherwise. In addition, terms such as “part” and “module” described in the specification mean a unit that processes at least one function or operation, which means that it can be implemented by one or more hardware or software or a combination of hardware and software. .

2 is an exemplary diagram for explaining a three-stage offloading method applicable to the present invention, and FIG. 3 is a flowchart illustrating a content caching method considering mobility of a helper according to an embodiment of the present invention. Also, FIG. 4 is an exemplary diagram for describing chunking of content and D2D coverage change for each chunk, and FIG. 5 is an exemplary diagram for explaining a method for caching content for each chunk using a mobile helper. 6 is a simulation graph showing the degree of offloading according to the moving speed of the helper, and FIG. 7 is a simulation graph showing the degree of offloading according to the content length.

In the present specification, the present invention will be described on the assumption that a mobile helper capable of operating with a large cache such as a device such as a car or a bus having mobility in a cell is used as a helper for caching content. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to an embodiment of the present invention, a content caching method using at least one mobile helper having mobility within a wireless communication cell coverage by a base station is provided. Here, the mobile helper performs content provision through D2D (Device to Device) communication in a relationship with a plurality of general communication terminals existing in the cell coverage.

That is, the content caching system according to an embodiment of the present invention is based on a circular cell made by a base station having a very large number of uniform communication terminals and a small number of mobile helpers. At this time, the D2D communication uses a D2D underlay communication system operated independently of the cellular frequency. According to the conventional method, in an off-peak time when the wireless network is not bottlenecked, the helper stores content in the cache size in the order of high request probability based on the common content preference received from the base station. In addition, the general communication terminal stores content based on personal content preferences that it knows through the application itself. In this case, it is assumed that there is no preference of the helper's personal content. In the peak time, the general communication terminal performs three-stage offloading as in FIG. 2.

As a first step, if there is a match in comparison with the content stored by the user himself during the off-peak time, self-offloading is performed to fetch the content from his own cache.

As a second step, if self-offloading fails, if the user is within the D2D radius of the neighboring helper and the requested content exists in the cache of the helper, the content is provided by D2D offloading.

As a third step, if D2D offloading is not performed, content is provided from a base station through a cellular network.

Therefore, in a D2D caching system that considers only the mobile helper, when a general communication terminal generates a request for specific content in a cellular peak time, the following process is performed. If the general communication terminal matches the content stored in the cache at the off-peak time and the requested content, self-offloading is successful. If self-offloading fails, after confirming that it belongs to the D2D radius of the neighboring helper, if the requested content is located in the cache of the helper, offloading may be performed through D2D communication. Since the helper considered here moves, the general user may belong to the helper's D2D radius after a certain period of time, even if it does not belong to the helper's D2D radius at the time the content request is generated. And if the helper has the requested content, it can save cellular radio resources by receiving the content in D2D with a certain time, that is, delay. Therefore, in the present invention, it can be said that the offloading with a spare time so that the probability that the general communication terminal is located within a radius of a helper capable of providing content after a content request is increased is the biggest difference from the conventional method.

Referring to FIG. 3, the content caching method according to an embodiment of the present invention includes: dividing the requested content into chunk units [S310]; Calculating D2D communication coverage for each chunk in consideration of content consumption time [S320]; Rearranging the content preference in chunk units by reflecting the calculated D2D communication coverage for each chunk [S330 and S340]; And determining a priority for each chunk to be stored in the cache of the mobile helper based on the content preference rearranged in chunk units [S350].

Here, in step S320, in the manner in which the D2D communication is added to the basic communication coverage, the content consumption time for each chunk and the additional communication coverage for the spare time determined by the movement speed as the mobility characteristic of the mobile helper are added. D2D communication coverage per chunk may be calculated.

Here, the step S340 is a method of multiplying the initial preference of the corresponding content according to the common content preference by the coverage expansion ratio compared to the basic communication coverage according to the calculated D2D communication coverage for each chunk, and calculating the content preference in units of chunks. It may further include.

This will be described in more detail as follows.

In order not to affect the quality of the actual service even if the content is received with a spare time, the next required content may be stored while the requested content is consumed by the general communication terminal. Suppose, for example, that there is content with an actual playing time of NT. Divide the content by a constant length T from the start of playback to form N chunks. At this time, it is assumed that offloading and caching are performed in chunk units. If the general communication terminal makes a request for content, it actually requests for all chunks (chunk[1], chunk[2], chunk[3], …., chunk[N]) that make up the content. It is like what happens. At this time, the first chunk of the chunks constituting the content should be provided with a request at the same time with a minimum delay. Therefore, if self-offloading and D2D offloading are not possible immediately, the content is provided from the base station through cellular communication without waiting. On the other hand, if the second chunk is not the first chunk (2≤n≤N), if the chunk is delivered within the minimum (n-1)T time from the moment the content request occurs until the n-1th chunk is played, do. Therefore, the free time for attempting D2D offloading increases, and the burden on the cellular network may be reduced. It can be said that D2D radius that each chunk can be offloaded to D2D in accordance with the order of chunks constituting the content is obtained.

For example, as shown in FIG. 4, suppose that video content having a length of 3T exists. The video content can be divided into three chunks of length T when caching and offloading. When the general terminal issues a request, the first chunk, chunk[1], must be received at the same time as the content request, and chunk[2] and chunk[3] are played by chunk[1], chunk[1]~[2], respectively. Since it has to be delivered within the given time, the D2D radius increases as the chunks that make up the back part of the content as shown in Figure 4 below.

In an environment in which there is a general communication terminal and a moving helper as shown in FIG. 5, when a general communication terminal makes a content request, it can be immediately received if the first chunk is present in the helper 1, and the chunk in the back part is followed for general communication. Helper 2 or helper 3 moving in the direction of the terminal may be able to provide.

The increased D2D radius means that the number of general communication terminals capable of supporting D2D offloading increases and the probability of D2D offloading increases.

Therefore, in the past, content was stored in order of preference based on the common content preference, but in the present invention, the common content preference is rearranged in units of chunks in consideration of the size of the D2D radius that varies for each chunk.

First, the initial preference of the chunk follows the preference of the content to which it belongs. For each content, the initial preference of each chunk is multiplied by the ratio of the D2D radius of each chunk increased, and the common preferences of the chunks are arranged in descending order based on the multiplied value. The helper caches chunks as much as its storage size in order of sorted common chunk preferences.

In the case of caching and offloading using the caching method, it was confirmed that the burden on the cellular network can be reduced through D2D offloading as the helper is more mobile and the length of the requested content is longer (Fig. 6). And Figure 7).

The content caching method according to the present invention described above can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes any kind of recording medium that stores data that can be read by a computer system. For example, there may be a read only memory (ROM), a random access memory (RAM), a magnetic tape, a magnetic disk, a flash memory, and an optical data storage device. In addition, the computer-readable recording medium may be distributed over computer systems connected through a computer communication network, and stored and executed as code readable in a distributed manner.

Although described above with reference to the embodiments of the present invention, those skilled in the art variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. And it can be easily understood.

Claims (6)

A content caching method using at least one mobile helper having mobility within a wireless communication cell coverage by a base station-the mobile helper is D2D (Device to Device) communication in a relationship with a plurality of general communication terminals existing in the cell coverage Providing contents through-
(a) dividing the requested content into chunk units;
(b) calculating D2D communication coverage for each chunk in consideration of content consumption time;
(c) rearranging the content preference in chunk units by reflecting the calculated D2D communication coverage for each chunk;
(d) determining a priority for each chunk to be stored in the cache of the mobile helper based on the content preference rearranged in chunk units.
Content caching method comprising a.
According to claim 1,
Step (b) is,
The D2D communication coverage for each chunk is calculated in such a way that the basic communication coverage in which the D2D communication is performed is summed up by the content consumption time for each chunk and the additional communication coverage for the spare time determined by the movement speed as the mobility characteristic of the mobile helper Characterized in that, content caching method.
According to claim 2,
Step (c) is,
Further comprising the step of calculating the content preference in units of chunks by multiplying the initial preference of the corresponding content according to the common content preference by the coverage expansion ratio compared to the basic communication coverage according to the calculated D2D communication coverage for each chunk. Way.
According to claim 1,
The provision of content through the device to device (D2D) communication is executed when self offloading from the self cache in the general communication terminal fails, considering the D2D communication coverage calculated through step (b) above A content caching method, characterized in that it is made in the chunk unit by a mobile helper capable of D2D communication with a general communication terminal.
The method of claim 4,
The D2D communication is performed by a D2D underlay communication method, a content caching method.
A computer-readable recording medium product in which the content caching method according to any one of claims 1 to 5 is recorded.

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