CN115037958A - Method for transmitting VR video through MEC cooperation based on 5G network - Google Patents

Method for transmitting VR video through MEC cooperation based on 5G network Download PDF

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CN115037958A
CN115037958A CN202210281030.9A CN202210281030A CN115037958A CN 115037958 A CN115037958 A CN 115037958A CN 202210281030 A CN202210281030 A CN 202210281030A CN 115037958 A CN115037958 A CN 115037958A
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mec
video
bit
view
rate
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CN115037958B (en
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唐勇
杨挺
夏靖雯
陈路遥
张椰
汪文勇
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/231—Content storage operation, e.g. caching movies for short term storage, replicating data over plural servers, prioritizing data for deletion
    • H04N21/23106—Content storage operation, e.g. caching movies for short term storage, replicating data over plural servers, prioritizing data for deletion involving caching operations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/80—Responding to QoS
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/10—Processing, recording or transmission of stereoscopic or multi-view image signals
    • H04N13/194—Transmission of image signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/366—Image reproducers using viewer tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/239—Interfacing the upstream path of the transmission network, e.g. prioritizing client content requests
    • H04N21/2393—Interfacing the upstream path of the transmission network, e.g. prioritizing client content requests involving handling client requests
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
    • H04N21/4363—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network
    • H04N21/43637—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network involving a wireless protocol, e.g. Bluetooth, RF or wireless LAN [IEEE 802.11]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
    • H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
    • H04N21/64746—Control signals issued by the network directed to the server or the client
    • H04N21/64761—Control signals issued by the network directed to the server or the client directed to the server
    • H04N21/64769—Control signals issued by the network directed to the server or the client directed to the server for rate control
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a 5G network-based method for transmitting VR video through MEC cooperation, and relates to the technical field of VR video transmission. The invention provides an MEC cooperation domain, a plurality of base stations are divided into a cooperation domain according to regional characteristics, and MECs in the cooperation domain cooperate with each other to jointly complete the processing of user request contents in the cooperation domain. A full-view low-bit-rate version of a VR video is stored in a cooperation domain, and each MEC independently operates a caching strategy for high-bit-rate tile blocks. Specifically, whether the high-bit-rate version of the tile block is cached is determined according to the request frequency of the FOV to which the tile block belongs of the user in the jurisdiction and the preference similarity of the FOV and the user in the jurisdiction. The invention overcomes the limitation of the computing capability and the storage capability of a single MEC, processes the user request together with a plurality of MECs, fully utilizes the computing and storage resources of the plurality of MECs, improves the maximum number of users which can be served, reduces the average content request delay of the users and reduces the flow of a return link.

Description

5G network-based method for transmitting VR video through MEC cooperation
Technical Field
The invention relates to the technical field of VR video transmission, in particular to a 5G network-based method for transmitting VR video through MEC cooperation.
Background
There are two main technical routes for VR video transmission: full View based and Field of View (FOV) based transmission schemes.
The full-view transmission scheme is to transmit the whole 360-degree surrounding picture to the terminal, and when the user rotates the head and needs to switch the picture, all processing is completed locally at the terminal. Under the condition of the same monocular visual resolution, the code rate of the VR video is much larger than that of the common plane video due to the frame rate, the quantization level, 360-degree surrounding and the like, the former is generally 5-10 times of that of the latter, which is a great challenge for transmission and greatly increases the cost.
However, when a user watches a video, the user has a certain viewing angle limitation, and cannot watch all the content, so that the bandwidth is greatly wasted by the full-viewing-angle transmission scheme.
The FOV transmission scheme mainly transmits a visible picture in a current view angle. Generally, a 360-degree panoramic view is divided into a plurality of views, each view generates a video file only containing high-resolution visual information in the view and low-resolution visual information of the surrounding part, and a terminal requests a server for a corresponding view file according to the current view posture position of a user. Specifically, such as a TWS (Tile Wise adaptive transmission) scheme.
The disclosure date is 2019, 9, 20, the disclosure number is CN110266664A, the invention patent publication is named as 'a Cloud VR video live broadcasting system based on 5G and MEC', the disclosure patent publication discloses a Cloud VR video live broadcasting system based on 5G and MEC, a content layer comprises a VR video shooting system and is used for providing real-time VR video content for a platform layer; the platform layer comprises a VR live broadcast system, and the VR live broadcast system is used for real-time importing, transcoding, slicing and outputting of VR videos in Cloud VR video live broadcast; the network layer is based on an operator 5G/4G wireless network MEC system and is used for providing stable transmission for Cloud VR video service and realizing data interaction between the platform layer and the terminal layer as well as between the platform layer and the content layer; the terminal layer comprises a Cloud VR terminal and is used for realizing VR video content presentation, network access and user authentication functions, the network layer is accessed into the MEC system, and VR video streams in the Cloud platform layer or the MEC system are directly accessed through the local distribution function.
In the prior art, the MEC server is deployed near the base station, and local support is provided for the user by providing computing and storage resources at the edge of the network, so that the quality of user experience is improved. However, the computing power and storage capacity of a single MEC server are very limited compared with those of a cloud center, and in order to reduce backhaul link traffic and better improve QoE (Quality of Experience) of users, the application provides a method for MEC cooperative transmission of VR videos based on a 5G network.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention provides a 5G network-based method for transmitting VR videos through MEC cooperation, and aims to reduce the flow of a backhaul link and better improve the QoE of a user. In the invention, an MEC cooperation domain is provided, a plurality of base stations are divided into a cooperation region according to regional characteristics, and the MECs in the cooperation region cooperate with each other to jointly complete the processing of the user request content in the cooperation region. A full-view low-bit-rate version of a VR video is stored in a cooperation domain, and each MEC independently runs a caching strategy for high-bit-rate tile blocks. Specifically, whether the high-bit-rate version of the tile block is cached is determined according to the request frequency of the FOV to which the tile block belongs of the user in the jurisdiction and the preference similarity of the FOV and the user in the jurisdiction. The invention overcomes the limitation of the computing power and the storage power of a single MEC, processes the user request by cooperating with a plurality of MECs, fully utilizes the computing and storage resources of the plurality of MECs, improves the maximum number of users which can be served, reduces the average content request delay of the users and reduces the flow of a backhaul link.
In order to solve the problems in the prior art, the invention is realized by the following technical scheme.
A method for transmitting VR video based on MEC cooperation of 5G network includes the following steps:
s1, distributing VR video content to an MEC cooperation domain through a central cloud, wherein the MEC cooperation domain is that wireless access point connection base stations of a plurality of 5G forward transmission networks are divided into a cooperation region according to regional characteristics, an MEC server is deployed near the wireless access point connection base station of each 5G forward transmission network, and the MEC servers in the cooperation region are mutually communicated to form the MEC cooperation domain;
s2, the MEC servers in the MEC cooperation domain cooperate with each other to complete the processing of the user request view angle; the method specifically comprises the following steps:
s201, a VR terminal device tracks the head movement track of a user, and when the visual angle of the user changes, a new visual angle is required to form a high-code-rate tile block set corresponding to a new visual angle and a low-code-rate full-visual-angle video file corresponding to the new visual angle; if the video file required by the new view angle is missing in the local cache of the VR terminal device, the step S202 is carried out;
s202, the VR terminal equipment sends a video request corresponding to the view angle to the Home MEC, and the video request is divided into two types according to whether the VR terminal equipment partially caches high-bit rate tile blocks corresponding to the view angle: 1) there is no partial cache: the video request comprises the request contents of all high-bit-rate tile blocks corresponding to the field angle and the low-bit-rate full-view video corresponding to the high-bit-rate tile blocks; 2) there is a partial cache: the video request comprises a high-bit-rate tile lost by VR terminal equipment;
if the Home MEC stores the information corresponding to the video request, directly responding to the VR terminal equipment;
if the information corresponding to the video request is not stored in the Home MEC, the Home MEC sends the video request to other MECs in the MEC cooperation domain;
if the other MECs store the information corresponding to the video request, the MEC responds to the Home MEC, and after receiving the information, the Home MEC responds to the VR terminal equipment;
if none of the MEC servers in the MEC cooperation domain store the information corresponding to the video request, the Home MEC initiates the video request to a central cloud, obtains the information corresponding to the video request and then responds to the VR terminal equipment;
when the Home MEC acquires the video information corresponding to the request from other MEC servers or a central cloud in the MEC cooperation domain, the Home MEC caches the acquired video information; when the space between the Home MEC caches is insufficient, the popularity of the current requested video information and the popularity of the cached video information need to be calculated, and whether the cached video information is deleted or not and the current requested video information is cached is determined according to the popularity;
s203, the Home MEC prepares a video requested by the VR terminal equipment through the step S202, and then responds to the VR terminal equipment; meanwhile, the Home MEC pushes high-code-rate tile blocks corresponding to other view angles with more association request times of the current requested view angle video information to the VR terminal equipment;
s204, after the VR terminal device prepares a high-bit-rate tile block set and a low-bit-rate full-view video file required by the current field angle, decoding the low-bit-rate full-view video file, independently decoding each high-bit-rate tile block, and then performing rendering and playing operations; and for the high-bit-rate tile pushed by the Home MEC, the VR terminal equipment adopts an FIFO cache strategy for storage.
Further, in the step S1, if the central cloud learns the preference of the user in the MEC collaborative domain for the VR video type, the high-bit-rate tile block set corresponding to the hotspot view angle in the related VR video and the low-bit-rate full-view video thereof are issued to the collaborative domain according to the preference of the user in the MEC collaborative domain.
Furthermore, the central cloud, under the condition that there is no favorite preference of the user in the MEC collaboration domain, issues a high-bit-rate tile set corresponding to a hotspot view angle in the most popular VR video and a low-bit-rate full-view video thereof into the collaboration domain according to the popularity of the full-network VR video.
In step S201, if a high-bit-rate tile block set corresponding to a new field angle is stored in a local buffer of the VR terminal device, the low-bit-rate full-field-angle video file is directly decoded, each high-bit-rate tile block is independently decoded, and then rendering and playing operations are performed.
Further, in step S202, if it is determined to cache the currently requested video information after popularity comparison, popularity of the video information corresponding to each cached field angle is compared, and a high-bit-rate tile set corresponding to a part of the field angles with the lowest popularity and a low-bit-rate full-view video corresponding to the tile set are deleted from the cache of the Home MEC until the cache space is sufficient to store the currently requested video information.
Further, in step S202, if the Home MEC is a low-bit-rate full-view video corresponding to the requested field angle obtained from the central cloud, the obtained low-bit-rate full-view video needs to be cached; if the cache space of the Home MEC is sufficient, directly caching the low-bit-rate full-view video on the current Home MEC; if the caching space is insufficient, deleting the video information corresponding to the cached view angle with low popularity from the cache of the Home MEC according to the popularity of the video corresponding to the view angle, and storing the obtained low-bit-rate full-view-angle video; and when the corresponding view angle of the low-bit-rate full-view video does not exist in the MEC cooperation domain, deleting the low-bit-rate full-view video from the MEC cooperation domain.
When deleting the video corresponding to the field angle, if the high-bit-rate tile block required by the field angle in a cache table or to be cached exists in the high-bit-rate tile block set in the deleted field angle, the high-bit-rate tile block is reserved.
Field of view
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Popularity of
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By its similarity to the user preferences in the Home MEC area
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And its nearest time slot
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Internal access frequency
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Are obtained together; the popularity calculation formula is as follows:
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（1）；
in calculating the similarity
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When the user's preferences in the Home MEC area are expressed as keyword vectors
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，
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Weight, angle of view representing keywords
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Expressed as a vector
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，
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Representing keywords
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Viewing angle
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The degree of importance of; specifically, the calculation formula of the similarity is as follows:
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（2）；
angle of view
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Access frequency in last time slot
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The calculation formula of (c) is as follows:
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(3) (ii) a In the formula (I), the compound is shown in the specification,
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representing field of view on Home MEC
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The number of times that it is requested,
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representing the total number of times the field of view is requested on the Home MEC.
Furthermore, the newly acquired field angle on the Home MEC is the nearest time slot
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Frequency of access within
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Is set to 1.
Compared with the prior art, the beneficial technical effects brought by the invention are as follows:
1. the invention overcomes the limitation of the computing capability and the storage capability of a single MEC, processes the user request together with a plurality of MECs, fully utilizes the computing and storage resources of the plurality of MECs, improves the maximum number of users which can be served, reduces the average content request delay of the users and reduces the flow of a return link.
2. The invention stores VR video files by using tile blocks as basic units, thereby saving the storage space of MEC. Since the FOVs may have overlapped regions, that is, they have partially identical high-bit-rate tile blocks, in the present invention, only one copy of these high-bit-rate tile blocks needs to be stored on the user's Home MEC, which saves more storage space than storing a single FOV independently.
3. The invention further pushes the next field angle FOV which the user may visit to the terminal equipment, thereby reducing the average content request time delay of the user.
4. The invention provides a method for determining whether to cache the field angle FOV according to the popularity of the field angle FOV, and compared with the traditional cache algorithm, the method can more fully utilize the MEC storage space and improve the cache hit rate.
Drawings
FIG. 1 is an end-to-end system framework diagram of a 360 panoramic VR video in accordance with the present invention;
fig. 2 is a model diagram of a 5G network-based architecture for MEC cooperative transmission VR video.
Detailed Description
The technical scheme of the invention is further elaborated by combining the drawings and the specific embodiments in the specification. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the examples in the present invention, are within the scope of protection of the present invention.
Referring to the accompanying drawings 1 and 2 in the specification, the embodiment provides a method for transmitting a VR video through MEC cooperation based on a 5G network, which specifically includes the following steps:
s1, distributing VR video content to an MEC cooperation domain through a central cloud, wherein the MEC cooperation domain is that wireless access point connection base stations of a plurality of 5G forward transmission networks are divided into a cooperation region according to regional characteristics, an MEC server is deployed near the wireless access point connection base station of each 5G forward transmission network, and the MEC servers in the cooperation region are mutually communicated to form the MEC cooperation domain;
s2, the MEC servers in the MEC cooperation domain cooperate with each other to complete the processing of the angle of view requested by the user; the method specifically comprises the following steps:
s201, a VR terminal device tracks the head movement track of a user, and when the visual angle of the user changes, a new visual angle is required to form a high-code-rate tile block set corresponding to a new visual angle and a low-code-rate full-visual-angle video file corresponding to the new visual angle; if the video file required by the new view angle is missing in the local cache of the VR terminal device, the step S202 is carried out;
s202, the VR terminal equipment sends a video request corresponding to the view angle to the Home MEC, and the video request is divided into two types according to whether the VR terminal equipment partially caches high-bit rate tile blocks corresponding to the view angle: 1) there is no partial cache: the video request comprises the request contents of all high-bit-rate tile blocks corresponding to the field angle and the low-bit-rate full-view video corresponding to the high-bit-rate tile blocks; 2) there is a partial cache: the video request comprises a high bit rate tile lost by VR terminal equipment;
if the Home MEC stores the information corresponding to the video request, directly responding to the VR terminal equipment;
if the information corresponding to the video request is not stored in the Home MEC, the Home MEC sends the video request to other MECs in the MEC cooperation domain;
if the other MECs store the information corresponding to the video request, the MEC responds to the Home MEC, and after receiving the information, the Home MEC responds to the VR terminal equipment;
if none of the MEC servers in the MEC cooperation domain store the information corresponding to the video request, the Home MEC initiates the video request to the central cloud, obtains the information corresponding to the video request and then responds to the VR terminal equipment;
when the Home MEC acquires the video information corresponding to the request from other MEC servers or a central cloud in the MEC cooperation domain, the Home MEC caches the acquired video information; when the cache space of the Home MEC is insufficient, the popularity of the current requested video information and the popularity of the cached video information need to be calculated, and whether the cached video information is deleted or not and the current requested video information is cached is determined according to the popularity;
s203, the Home MEC prepares a video requested by the VR terminal equipment through the step S202, and then responds to the VR terminal equipment; meanwhile, the Home MEC pushes high-code-rate tile blocks corresponding to other view angles with more association request times of the current requested view angle video information to the VR terminal equipment;
s204, after the VR terminal device prepares a high-bit-rate tile block set and a low-bit-rate full-view video file required by the current field angle, decoding the low-bit-rate full-view video file, independently decoding each high-bit-rate tile block, and then performing rendering and playing operations; and for the high-bit-rate tile pushed by the Home MEC, the VR terminal equipment adopts an FIFO cache strategy for storage.
As an implementation manner of this embodiment, as shown in fig. 2, the whole transmission architecture is composed of four parts, namely, a central cloud, a 5G network, an MEC collaboration domain, and a user VR terminal device, and functions of the four parts are described below.
A central cloud: when the VR video service part synthesis computing capacity sinks to the edge of a network, the central cloud is mainly responsible for the early-stage production and distribution of VR videos, including video splicing and stitching, VR video mapping and encoding, and distribution of encoded content to MECs. And dividing the spliced and stitched 360-degree panoramic video into a segment set with the duration of 1 second. Each video clip is projected to a two-dimensional plane in an ERP mode, and then the two-dimensional plane video is divided into N × M blocks which can be independently coded and decoded, and the N × M blocks are called tile blocks for short. The user's field angle FOV, i.e. the area of the picture where the gaze is focused, is made up of a number of tile blocks. Because a user only pays attention to a picture inside a current FOV at one moment and does not pay special attention to a picture outside the FOV, high-rate transmission is adopted for a plurality of tile blocks forming the FOV, low-rate transmission is adopted for a plurality of tile blocks forming the picture at the periphery of the FOV, and for simplicity, a full-view-angle video transmitting the whole low rate is adopted to serve as a peripheral background image of the current FOV of the user. In addition, the FOV of the user is not fixed, and the picture area where each tile block is located may become the FOV of the user. Thus, a high rate version is prepared in the invention for each tile block. Because the delay for transmitting the whole low-rate full-view video is comparable to the delay for transmitting a high-rate tile block of FOV, even the former may be lower than the latter, so that the central cloud only distributes a low-rate full-view video to the MEC cooperation domain enough to support the request of the whole cooperation domain.
5G network: the 5G network can provide larger downlink bandwidth for a VR video system, and can simultaneously pack and send video contents of a plurality of peripheral viewpoints when the current VR video watching viewpoint is transmitted in a downlink mode. A VR video transmission network based on a 5G network can be structurally divided into three parts, a fronthaul network, a backhaul network, and a core network. The forward network consists of a number of wireless access nodes connected to a Base Station (BS) to solve the last mile problem. Typically, a base station is responsible for a small area (e.g., several residential and business areas) where users are connected to the base station when using mobile networks. This base station is also referred to as the Home BS for these users in our invention. The backhaul network consists of a number of base stations connected to a mobile switching node through which it can access the 5G core network and further connect to other networks, such as the internet. The forward Network and the return Network together form a Radio Access Network (RAN) in a 5G Network. Generally, in order to obtain better performance and serve more users, a large data center (also referred to as a cloud node) is generally configured with massive storage space and computing resources and is deployed near a core switching node of a backbone network, such as a junction between a 5G core network and the internet.
MEC cooperation domain: in a conventional RAN network, when a user wants to request a video, the data will span multiple networks, including a fronthaul network, a backhaul network, a core network, the internet, etc. The disadvantages of this mode are: 1) the user will wait a longer time and be unfriendly to delay sensitive applications; 2) the radio access network, and in particular the backhaul network therein, will face a large traffic pressure. One solution is to deploy the MEC server near the base station, which will provide local support for the user by providing computing and storage resources at the edge of the network, thereby improving the Quality of Experience (QoE) of the user. However, the computing power and storage capacity of a single MEC server are very limited compared to a cloud center, and in order to reduce backhaul link traffic and better improve QoE of users, we propose the concept of MEC collaboration domain. And dividing the base stations into a cooperation area according to regional characteristics, which is called the cooperation area for short. The MECs in one cooperation domain cooperate with each other to jointly complete the processing of the content requested by the user in the cooperation domain. An MEC has the computational power of encoding and decoding and the storage power of caching hot content. A full-view low-bit-rate version of a VR video is stored in a cooperation domain, and each MEC independently operates a caching strategy for high-bit-rate tile blocks. Specifically, whether a high-bit-rate version of the tile block is cached or not is determined according to the request frequency of a user in the jurisdiction to the FOV of the tile block and the preference similarity of the FOV and the user in the jurisdiction.
VR video terminal: the VR video terminal comprises a Wi-Fi module, a video frame processing module, a playing operation control module, a display processing module and the like, and has the capabilities of decoding, posture perception, motion trail prediction, real-time model rendering, presentation and the like. At present, the main stream resolution of VR video is 4K, but the resolution of high-quality VR video at least reaches more than 8K, and the higher resolution can reach 30K. Therefore, the typical monocular resolution of the terminal needs to reach 2K or more, the hardware needs to support 8K decoding capability, the dynamic sensing delay of the terminal head needs to be less than 20ms, and meanwhile, the terminal also needs to have high-performance communication capability. In addition, the VR video terminal also has certain storage capacity and is used for receiving a high-code-rate tile corresponding to an FOV (field of view) which is pushed by the home MEC in advance and is likely to be accessed immediately and a low-code-rate full-view video corresponding to the FOV.
As an implementation manner of this embodiment, as shown in fig. 2, the operation flow of the MEC cooperative transmission VR video framework is mainly divided into two parts: the first part is that when the cooperation system initially runs, the center cloud distributes processed video content to an MEC cooperation domain in advance; and the second part is that the MEC cooperation domains cooperate with each other to finish the processing of the FOV requested by the user.
In the first part, the flow of distributing the video content to the MEC collaboration domain by the central cloud is as follows:
if the central cloud learns the preference of the user of the MEC cooperation domain on the VR video type, issuing a hot spot FOV and a low-bit-rate full-view video in the relevant VR video to the MEC cooperation domain according to the preference of the user of the MEC cooperation domain;
if the central cloud does not have the favorite preference of the user in the MEC cooperation domain, the most popular hot-spot FOV in the VR video and the low-bit-rate full-view video thereof are delivered to the cooperation domain according to the popularity of the full-network VR video.
In the second part, when a user requests a FOV, the transmission operation flow of the MEC collaboration domain is as follows:
VR terminal equipment tracks user's head movement track, when the user visual angle changes, just needs the FOV that the new visual angle corresponds. In this embodiment, if a certain high-rate tile exists in the cache of the VR terminal device, a low-rate full-view video of the FOV to which the tile belongs is cached simultaneously in the past. Therefore, if the high-bit-rate tile block set T corresponding to the needed FOV is stored in the local cache, the low-bit-rate full-view video file is directly decoded, each tile block is independently decoded, and then rendering and playing operations are executed.
If any tile block in the set T is not stored on the Home MEC, it also means that the low-bit-rate full-view video corresponding to the FOV is not stored on the Home MEC. At this time, the VR terminal device sends a video request corresponding to the view angle to the Home MEC, and the information corresponding to the video request includes a high-bitrate tile set corresponding to the view angle and a low-bitrate full-view video corresponding to the FOV. Otherwise, it needs to request the missing high bit rate tile block in the set T from the Home MEC. And the VR terminal equipment sends one of the two types of video requests corresponding to the field angle to the Home MEC.
If the Home MEC stores the information corresponding to the video request, directly responding to the VR terminal equipment;
if the Home MEC does not store the information corresponding to the video request, the Home MEC sends the video request to other MECs in the MEC cooperation domain; if the other MECs store the information corresponding to the video request, the MEC responds to the Home MEC, and after receiving the information, the Home MEC responds to the VR terminal equipment; and if none of the MEC servers in the MEC cooperation domain stores the information corresponding to the video request, the Home MEC initiates the video request to the central cloud, obtains the information corresponding to the video request and then responds to the VR terminal equipment.
The Home MEC prepares a video file requested by the VR terminal equipment through the process, and then responds to the VR terminal equipment; meanwhile, the Home MEC pushes high-code-rate tile blocks corresponding to other view angles with more association request times of the current requested view angle video information to the VR terminal equipment; to reduce subsequent transmission bandwidth consumption.
After preparing a high-bit-rate tile block set and a low-bit-rate full-view video file required by a current field angle, the VR terminal equipment decodes the low-bit-rate full-view video file, independently decodes each high-bit-rate tile block, and then performs rendering and playing operations; and for the high-bit-rate tile pushed by the Home MEC, the VR terminal equipment adopts an FIFO cache strategy for storage. If all high-rate tile blocks corresponding to the low-rate full-view video are removed from the buffer, the low-rate full-view video also needs to be removed.
As an implementation manner of this embodiment, when the Home MEC acquires the requested corresponding video information from other MEC servers or a central cloud in the MEC cooperation domain, if the cache space of the Home MEC can accommodate the high-bit-rate tile blocks, the Home MEC directly caches the acquired video information.
When the Home MEC cache space is insufficient, the popularity of the currently requested video information and the popularity of the cached video information need to be calculated, and whether to delete the cached video information and cache the currently requested video information is determined according to the popularity.
If after popularity comparison, the currently requested video information is determined to be cached, the popularity of the video information corresponding to each cached field angle is compared, and a high-bit-rate tile set corresponding to a part of the field angle with the lowest popularity and a low-bit-rate full-view video corresponding to the high-bit-rate tile set are deleted from the cache of the Home MEC until the cache space is enough to store the currently requested video information.
If the Home MEC is a low-bit-rate full-view-angle video corresponding to the requested view angle obtained from the central cloud, caching the obtained low-bit-rate full-view-angle video; if the cache space of the Home MEC is sufficient, directly caching the low-bit-rate full-view video on the current Home MEC; if the caching space is insufficient, deleting the video information corresponding to the cached view angle with low popularity from the cache of the Home MEC according to the popularity of the video corresponding to the view angle, and storing the obtained low-bit-rate full-view-angle video; and when the corresponding view angle of the low-bit-rate full-view video does not exist in the MEC cooperation domain, deleting the low-bit-rate full-view video from the MEC cooperation domain.
When deleting the video corresponding to the field angle, if the high-bit-rate tile block required by the field angle in a cache table or to be cached exists in the high-bit-rate tile block set in the deleted field angle, the high-bit-rate tile block is reserved.
As still another embodiment of this embodiment, the field of view
Figure 175553DEST_PATH_IMAGE024
Popularity of
Figure DEST_PATH_IMAGE025
By its similarity to the user preferences in the Home MEC area
Figure 885889DEST_PATH_IMAGE026
And its most recent time slot
Figure 50154DEST_PATH_IMAGE028
Internal access frequency
Figure DEST_PATH_IMAGE029
Are obtained together; the popularity calculation formula is as follows:
Figure 495042DEST_PATH_IMAGE030
（1）；
in calculating the similarity
Figure 239007DEST_PATH_IMAGE026
Time, HomThe preferences of users in the e MEC region are expressed as keyword vectors
Figure DEST_PATH_IMAGE031
，
Figure 335008DEST_PATH_IMAGE032
Weight, angle of view representing keywords
Figure DEST_PATH_IMAGE033
Expressed as a vector
Figure 607857DEST_PATH_IMAGE034
，
Figure DEST_PATH_IMAGE035
Representing keywords
Figure 520800DEST_PATH_IMAGE036
Viewing angle
Figure DEST_PATH_IMAGE037
The degree of importance of; specifically, the calculation formula of the similarity is as follows:
Figure 537297DEST_PATH_IMAGE038
（2）；
field of view
Figure 769696DEST_PATH_IMAGE037
Last time slot
Figure DEST_PATH_IMAGE039
Internal access frequency
Figure 993873DEST_PATH_IMAGE040
The calculation formula of (a) is as follows:
Figure DEST_PATH_IMAGE041
(3) (ii) a In the formula (I), the compound is shown in the specification,
Figure 882194DEST_PATH_IMAGE042
representing angle of view on Home MEC
Figure DEST_PATH_IMAGE043
The number of times that it has been requested,
Figure 217229DEST_PATH_IMAGE044
representing the total number of times the field of view is requested on the Home MEC.
To avoid the unfriendliness of the access frequency to the newly arrived FOV on the MEC, the access frequency of the latest slot t of the newly arrived FOV is not calculated using equation 3 but is set to 1, i.e., its access popularity depends only on the distance from the user's preference keyword vector.

Claims (9)

1. A method for MEC cooperative transmission of VR video based on 5G network is characterized in that the method comprises the following steps:
s1, distributing VR video content to an MEC cooperation domain through a central cloud, wherein the MEC cooperation domain is that wireless access point connection base stations of a plurality of 5G forward transmission networks are divided into a cooperation region according to regional characteristics, an MEC server is deployed near the wireless access point connection base station of each 5G forward transmission network, and the MEC servers in the cooperation region are mutually communicated to form the MEC cooperation domain;
s2, the MEC servers in the MEC cooperation domain cooperate with each other to complete the processing of the angle of view requested by the user; the method specifically comprises the following steps:
s201, a VR terminal device tracks the head movement track of a user, and when the visual angle of the user changes, a new visual angle is required to form a high-bit-rate tile set corresponding to a new visual angle and a low-bit-rate full-visual-angle video file corresponding to the new visual angle; if the video file required by the new view angle is missing in the local cache of the VR terminal device, the step S202 is carried out;
s202, the VR terminal equipment sends a video request corresponding to the view angle to the Home MEC, and the video request is divided into two types according to whether the VR terminal equipment partially caches high-bit-rate tile blocks corresponding to the view angle: the first type is the absence of a partial cache: the video request comprises the request contents of all high-bit-rate tile blocks corresponding to the field angle and the low-bit-rate full-view video corresponding to the high-bit-rate tile blocks; the second type is that there is a partial cache: the video request comprises a high-bit-rate tile lost by VR terminal equipment;
if the Home MEC stores the information corresponding to the video request, directly responding to the VR terminal equipment;
if the Home MEC does not store the information corresponding to the video request, the Home MEC sends the video request to other MECs in the MEC cooperation domain;
if the information corresponding to the video request is stored in other MECs, the MECs respond to the Home MEC, and after receiving the information, the Home MEC responds to the VR terminal equipment;
if none of the MEC servers in the MEC cooperation domain store the information corresponding to the video request, the Home MEC initiates the video request to the central cloud, obtains the information corresponding to the video request and then responds to the VR terminal equipment;
when the Home MEC acquires the video information corresponding to the request from other MEC servers or a central cloud in the MEC cooperation domain, the Home MEC caches the acquired video information; when the cache space of the Home MEC is insufficient, the popularity of the current requested video information and the popularity of the cached video information need to be calculated, and whether the cached video information is deleted or not and the current requested video information is cached is determined according to the popularity;
s203, the Home MEC prepares a video requested by the VR terminal equipment through the step S202, and then responds to the VR terminal equipment; meanwhile, the Home MEC pushes high-code-rate tile blocks corresponding to other view angles with more association request times of the current requested view angle video information to the VR terminal equipment;
s204, after the VR terminal device prepares a high-bit-rate tile block set and a low-bit-rate full-view video file required by the current field angle, decoding the low-bit-rate full-view video file, independently decoding each high-bit-rate tile block, and then performing rendering and playing operations; and for the high-bit-rate tile pushed by the Home MEC, the VR terminal equipment adopts an FIFO cache strategy for storage.
2. The method for transmitting the VR video through MEC cooperation based on 5G network as claimed in claim 1, wherein: in the step S1, if the central cloud learns the preference of the user of the MEC collaborative domain for the VR video type, the high-bit-rate tile block set corresponding to the hot-spot view angle in the related VR video and the low-bit-rate full-view video thereof are issued to the collaborative domain according to the preference of the user of the MEC collaborative domain.
3. The method for 5G network-based MEC cooperative transmission of VR video of claim 1 or 2, wherein: in the step S1, the central cloud issues a high-bit-rate tile set corresponding to a hotspot view angle in the most popular VR video and a low-bit-rate full-view video thereof into the cooperation domain according to the popularity of the full-network VR video without the favorite preference of the user in the MEC cooperation domain.
4. The method for 5G network-based MEC cooperative transmission of VR video of claim 1, wherein: in the step S201, if the VR terminal device caches a new high-bit-rate tile block set corresponding to the field angle, the VR terminal device directly decodes the low-bit-rate full-view video file and independently decodes each tile block, and then performs rendering and playing operations.
5. The method for transmitting the VR video through MEC cooperation based on 5G network as claimed in claim 1, wherein: in step S202, if it is determined to cache the currently requested video information after popularity comparison, popularity of the video information corresponding to each cached field angle is compared, and a high-bit-rate tile set corresponding to a part of the field angle with the lowest popularity and a low-bit-rate full-field-view video corresponding to the high-bit-rate tile set are deleted from the cache of the Home MEC until the cache space is sufficient to store the currently requested video information.
6. The method for 5G network-based MEC cooperative transmission of VR video of claim 1, 2, 4 or 5, wherein: in the step S202, if the Home MEC is a low-bit-rate full-view video corresponding to the requested field angle obtained from the central cloud, the obtained low-bit-rate full-view video also needs to be cached; if the cache space of the Home MEC is sufficient, directly caching the low-bit-rate full-view video on the current Home MEC; if the caching space is insufficient, deleting the video information corresponding to the cached view angle with low popularity from the cache of the Home MEC according to the popularity of the video corresponding to the view angle, and storing the obtained low-bit-rate full-view-angle video; and when the corresponding view angle of the low-bit-rate full-view-angle video does not exist in the MEC cooperation domain, deleting the low-bit-rate full-view-angle video from the MEC cooperation domain.
7. The method of claim 6, wherein the MEC cooperatively transmits the VR video over the 5G network, and the method comprises: when deleting the video corresponding to the field angle, if the high-bit-rate tile block required by the field angle in a cache table or to be cached exists in the high-bit-rate tile block set in the deleted field angle, the high-bit-rate tile block is reserved.
8. The method for 5G network-based MEC cooperative transmission of VR video of claim 1, 2, 4 or 5, wherein: angle of view
Figure DEST_PATH_IMAGE002
Popularity of
Figure DEST_PATH_IMAGE004
By its similarity to the user preferences in the Home MEC area
Figure DEST_PATH_IMAGE006
And its nearest time slot
Figure DEST_PATH_IMAGE008
Frequency of access within
Figure DEST_PATH_IMAGE010
Are obtained together; the popularity calculation formula is as follows:
Figure DEST_PATH_IMAGE012
（1）；
in calculating the similarity
Figure 197872DEST_PATH_IMAGE006
When the user's preferences in the Home MEC area are expressed as a keyword vector
Figure DEST_PATH_IMAGE014
，
Figure DEST_PATH_IMAGE016
Weight, angle of view representing keywords
Figure DEST_PATH_IMAGE018
Expressed as a vector
Figure DEST_PATH_IMAGE020
，
Figure DEST_PATH_IMAGE022
Representing keywords
Figure DEST_PATH_IMAGE024
Viewing angle
Figure DEST_PATH_IMAGE026
The degree of importance of; specifically, the calculation formula of the similarity is as follows:
Figure DEST_PATH_IMAGE028
（2）；
field of view
Figure DEST_PATH_IMAGE030
Last time slot
Figure DEST_PATH_IMAGE032
Frequency of access within
Figure DEST_PATH_IMAGE034
The calculation formula of (a) is as follows:
Figure DEST_PATH_IMAGE036
(3) (ii) a In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE038
representing field of view on Home MEC
Figure DEST_PATH_IMAGE040
The number of times that it is requested,
Figure DEST_PATH_IMAGE042
representing the total number of times the field of view is requested on the Home MEC.
9. The method of claim 8, wherein the MEC cooperatively transmits the VR video based on the 5G network, and the method comprises: newly acquired view angle nearest time slot on Home MEC
Figure 85319DEST_PATH_IMAGE032
Frequency of access within
Figure 599477DEST_PATH_IMAGE034
Is set to 1.
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