CN1791213A - Mobile video order service system with optimized performance and realizing method - Google Patents

Abstract

A mobile video-on-demand service system and implementation method based on GPRS mobile network and performance optimization. In addition to the network elements of traditional video-on-demand services, the system also includes two types of new network elements: a central cache agent set on the boundary between GGSN and PDN CCP server, to alleviate the business load of SCS, reduce the network bandwidth consumption between GGSN and SCS; set in each BSS, that is, the user boundary cache proxy UECP server set between each BSC and each BTS, adopts cache-based The adaptive cache of the replacement strategy is used to improve the cache hit rate, thereby ensuring the rapid response of most users' video-on-demand requests; in addition, a high-speed IP direct link for transmitting streaming media content is set between the CCP and each UECP, and the two A proxy server constitutes a two-level cache device for streaming media content, thereby bypassing a large number of program content streaming media, reducing the data flow and processing load of other links, and eliminating the impact of video-on-demand services on network performance.

Description

A performance-optimized mobile video-on-demand service system and its implementation method

technical field

The present invention relates to a performance-optimized mobile video-on-demand service system and its implementation method. Specifically, it relates to a GPRS mobile network-based, performance-optimized mobile video-on-demand service system and its implementation method. The field of communication network technology.

Background technique

Mobile video on demand VoD (Video on Demand) using mobile terminals is an important mobile data service, which meets the needs of mobile users to watch video programs anytime and anywhere, and has huge market potential. At present, China Mobile has provided mobile video-on-demand services in Shanghai, Zhejiang, Fujian and other provinces and cities using the GPRS (General Packet Radio Service) network.

GPRS network is a 2.5 generation mobile communication network, it is based on the current GSM mobile communication network, mainly by adding GPRS service support node SGSN (Serving GPRS Support Node) and GPRS gateway support node GGSN (Gateway GPRS Support Node ) realized by two network element entities. The main feature of the GPRS network is that it can support medium and high-speed data transmission, and can provide each user with a data transmission rate of 9.05-171.2kbit/s. SGSN is a node that provides services for mobile terminal MS. When GPRS service is activated, SGSN establishes a mobility management environment, including information about the mobility and security of this mobile terminal MS. The main role of the SGSN is to record the current location information of the mobile station, and complete the sending and receiving of mobile packet data between the mobile station and the SGSN. The main function of the GGSN is a gateway, which is used to connect a variety of different data networks; the GGSN stores the routing information of GPRS service users, and according to the information, sends the protocol data unit PDU (Protocol Data Unit) to the current service connection of the MS using tunneling technology. The entry point is the SGSN.

The existing mobile video-on-demand system includes the following parts: GPRS network, streaming content server SCS (Streaming Content Server), WAP portal and user terminal MS. Among them, the GPRS network is used to transmit streaming media content; the streaming media content server SCS is used to store multimedia program content pre-produced by content providers; Information such as the introduction of the program and the URL of the link address; the mobile terminal must be a 2.5G mobile phone or PDA with GRPS function. In order to support the streaming media service, the terminal also needs to be installed to support the corresponding streaming media content decoding format (such as H.264) and control protocol (such as RTSP) playback software.

Usually, a complete VoD business process includes the following steps:

(1) The mobile user accesses the WAP portal website of the streaming media service through the WAP browser of the terminal, and selects the content he is interested in by browsing the program introduction;

(2) The user clicks on the title of the desired program, and the link address URL of the program content is fed back to the WAP browser of the terminal;

(3) WAP browser starts the streaming media player program on the terminal by association;

(4) the streaming media player requests connection to the corresponding streaming media content server SCS according to the URL of the program;

(5) After the streaming media content server accepts the connection, it provides the user with continuous streaming media program content, and monitors the real-time transmission control protocol of the mobile user;

(6) GPRS network bears the transmission of program content and control protocol;

(7) After receiving the program stream, the user first caches it, and starts playing the program after the cached content reaches a certain amount; and controls the service through the real-time transmission control protocol.

(8) During the playing of the program, the user sends RTSP protocol messages through the playing software to realize the interactive operation with the server.

In the framework of the execution steps of the above-mentioned VoD service, there are some performance bottlenecks:

(1) The service delay is relatively large: it is mainly reflected in the fact that the underlying protocol of the GPRS backbone network is not suitable for real-time continuous streaming media service transmission, and the tunnel protocol GTP (GPRS Tunnel Protocol) actually adopted increases the transmission delay of media streams;

(2) Large network bandwidth consumption: the transmission rate of a single media stream should not be lower than 20Kbps, and multiple users online at the same time will cause a large traffic impact on the GPRS core network;

(3) The number of concurrent users that the core network can carry is small: when multiple users are online at the same time, the service performance drops greatly.

Therefore how to solve the performance problem that occurs in the above-mentioned mobile video on demand based on the GPRS network has become an urgent technical problem to be solved.

Contents of the invention

In view of this, the purpose of the present invention is to provide a mobile video-on-demand service system based on GPRS mobile network and performance optimization and an implementation method, thereby better solving various performance bottlenecks that occur in mobile video-on-demand on the current GPRS network.

In order to achieve the above object, the present invention provides a performance-optimized mobile video-on-demand service system, at least including: GPRS network and each network element in the network: mobile switching center MSC, GPRS service support node SGSN, GPRS gateway support node Point GGSN, streaming media content server SCS, WAP portal server, base station system BSS and user mobile terminal MS; It is characterized in that: described system also comprises:

The central cache proxy CCP (Central Cache Proxy) server is set on the boundary between the GPRS gateway support node GGSN and the external packet data network PDN (Packet Data Networks), which is used to alleviate the business load of the SCS and reduce the network between the GGSN and the SCS. Bandwidth consumption, improve the response speed of video on demand;

User Edge Cache Proxy UECP (User Edge Cache Proxy) server is set in each base station system BSS, that is, between each base station switching controller BSC and each base station BTS, with adaptive caching capability based on cache replacement strategy, By improving the cache hit rate, to ensure a fast response to user video-on-demand requests;

A high-speed IP direct connection link is set between the CCP server and each UECP server, and is used to transmit streaming media content between the two, and thereby the two types of proxy servers constitute two nodes of the streaming media content in the entire system. Level cache device, thereby bypassing a large number of program content streaming media, significantly reducing the data flow and processing load of other links, reducing and eliminating the impact of video-on-demand services on network performance.

Described central caching agent CCP server is to set at least one in each public land mobile network PLMN (PublicLands Mobile Network), and its configuration quantity depends on business demand.

The functions completed by the central cache proxy CCP server further include:

Monitor real-time streaming protocol RTSP (Real Time Streaming Protocol) messages, and then match them with on-demand rankings: monitor RTSP messages between GGSN and SCS, intercept and parse RTSP request messages, and extract uniform resource locators of programs URL, and then use the URL to match the on-demand ranking list on the CCP; if the match is successful, terminate the request message, and respond to the mobile terminal with the corresponding RTSP message through the GGSN, then extract the program content from the cache library and use the real-time transport protocol RTP (Real TimeTransport Protocol) is sent to the mobile terminal via the IP direct link; otherwise, the RTSP request message is forwarded to the SCS;

Real-time Transport Protocol RTP media stream monitoring, transmission and cache replacement: monitor and intercept the RTP media stream from SCS to GGSN, intercept and save the program content that meets the cache replacement strategy in its cache library, and then transfer the content from SCS or cache library The program content is sent to the user using the RTP protocol;

Create CCP on-demand rankings: According to the set period, make statistics on program on-demand status or aggregate statistics on program on-demand status reported by each UECP, and create CCP on-demand rankings according to the ranking criteria.

The software control module in the central cache agent CCP server includes:

RTSP message filtering and forwarding module: monitor the RTSP message between GGSN and SCS, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and then respond to the RTSP message that matches the on-demand list successfully, and forward the on-demand RTSP packets that fail to match the leaderboard;

Ranking matching module: according to the URL of the program on demand, query the ranking list in the storage module for program matching; if the match is successful, then instruct the "RTP media stream monitoring and transmission module" to take out the program content from the storage module and send it to the user; Otherwise, then return to " RTSP packet filtering and forwarding module " and match unsuccessful result;

Statistical analysis module: complete the CCP on-demand ranking list and store it in the storage module;

Storage module: used to store all or the first part of the CCP on-demand ranking list and programs included in the list;

RTP media stream monitoring and transmission module: monitor and intercept the RTP media stream from SCS to GGSN, and notify the cache replacement module to save the media stream content satisfying the cache replacement strategy in the storage module; responsible for intercepting the program content from the SCS or storing it The program content of the module is sent to the user via the IP direct link using the RTP protocol.

Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy.

The functions completed by the user boundary cache proxy UECP server further include:

Monitor the real-time streaming protocol RTSP message, and then match it with the on-demand ranking list: monitor the RTSP message between BTS and BSC, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and then use the URL to match On-demand ranking list on UECP; if the match is successful, the request message will be terminated, and the corresponding RTSP message will be used to respond to the mobile terminal through the BTS, and then the program content will be extracted from the cache library and sent to the mobile terminal; if the match is unsuccessful, Then forward the RTSP request message to the BSC;

Real-time transport protocol RTP media stream monitoring, transmission and cache replacement: receive the RTP media stream from CCP and transmit it to BTS, and save the program content that meets the cache replacement strategy in its cache library; in the process of cache processing, priority is given to Header caching to make full use of the limited storage capacity of UECP;

Create UECP on-demand rankings: According to the set cycle, make statistics on the program on-demand status, make UECP's on-demand rankings according to the ranking criteria, and report the statistical information to CCP; or UECP receives CCP's on-demand rankings synchronously as its own On-demand leaderboards.

The head cache is to store the beginning part of the program that enters the list, so as to reduce the start-up delay of the program requested by the user-the time difference from sending the request for request to seeing the first frame of the picture, so as to make full use of the storage space of the UECP cache library;

The software control module in the UECP server of described User Border Cache proxy includes:

RTSP message filtering and forwarding module: monitor the RTSP message between BTS and BSC, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and forward the unmatched RTSP message;

Ranking matching module: according to the URL of the program on demand, query the ranking list in the storage module for program matching; if the match is successful, then instruct the "RTP media stream transmission module" to take out the program content from the storage module and send it to the user; otherwise, Then return the matching unsuccessful result to the "RTSP message filtering and forwarding module";

Statistical analysis module: complete the UECP on-demand ranking list, store it in the storage module, and regularly report statistical information to the CCP;

Storage module: used to store UECP on-demand rankings and all or the first part of the programs on the list;

RTP media stream transmission module: receives the RTP media stream from CCP and transmits it to BTS, and notifies the cache replacement module to save the content of the program stream satisfying the cache replacement strategy in the storage module; accepts the instruction of the leaderboard matching module, and sends the successfully matched The program content is taken out from the storage module and sent to the user;

Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy.

The program-on-demand ranking list is a core data table maintained by the CCP/UECP server. It consists of a series of records, each record corresponds to a program in the list, and a record is composed of several record items. These record items include but not Limited to the program number, program name, program profile, program URL, program access address in the storage module, and program price, the size of the leaderboard depends on the cache capacity of the CCP/UECP server.

The content of the cache replacement strategy is: if a certain program is in the on-demand ranking list, but has not been cached; or a certain program is not in the current on-demand ranking list, but the accumulated If the number of on-demand programs exceeds a certain threshold, the CCP/UECP server will cache the content of the program.

In order to achieve the above object, the present invention also provides a method for realizing a performance-optimized mobile video-on-demand service, which is characterized in that: comprising the following steps:

(1) The user connects to the content publishing page of the SCS through the WAP browser on the mobile terminal, retrieves the program introduction information, orders a certain program, that is, clicks on the hyperlink of the program, and the mobile user sends the content to the SCS through the media player software installed on the terminal. Real-time streaming protocol RTSP request, the RTSP request message at least includes the Uniform Resource Locator URL field for addressing the program requested by the user on the SCS server;

(2) The UECP server monitors the RTSP request message of the mobile terminal at the application layer, intercepts and parses the RTSP request message, extracts the URL of the program, and uses the URL to match the on-demand list on the UECP; if the match is successful, perform subsequent operations; Otherwise, jump to step (4);

(3) The UECP server terminates the RTSP request, and after sending the corresponding message response to the mobile terminal, extracts the program content from the cache module and sends it to the mobile terminal using the RTP protocol; The direct link requests the CCP to download the subsequent part of the program file to ensure the continuous playback of the user terminal and end the process;

(4) The UECP server forwards the RTSP request message of the mobile terminal to the BSC. When the CCP server monitors the RTSP request message, it intercepts and parses the RTSP request message, extracts the URL of the program, and then uses the URL to match the URL on the CCP. On-demand leaderboard; if the match is successful, then terminate the continued sending of the request message, and respond to the mobile terminal through the GGSN with the corresponding RTSP message; then extract the program content from its cache library and send it to the mobile terminal. The sending path is Through CCP, UECP, BTS and MS in turn; if the match is unsuccessful, the CCP server forwards the RTSP request message to the SCS, and then the SCS sends the program content to the mobile terminal, and the sending path is through the SCS, CCP, UECP, BTS and MS, end of process.

The present invention is a performance-optimized mobile video-on-demand service system based on GPRS mobile network and its realization method. Cache system for high-level program content. The CCP server introduced therein alleviates the service load of the streaming media content server SCS, and effectively reduces the network bandwidth consumption between the GGSN and the SCS. The UECP server has an adaptive caching capability based on a caching replacement strategy, and can ensure fast response to most users' video-on-demand requests by improving the caching hit rate. The high-speed IP direct link can bypass a large amount of mobile streaming media traffic, significantly reduce the data traffic and processing load on the GGSN-SGSN-BSC link, and reduce or eliminate the impact of video-on-demand services on part of the network performance.

The header cache adopted by the UECP server has the following advantages: (1) It speeds up the program startup speed and improves the user experience; (2) The header cache can smooth online transmission fluctuations in the network; (3) Effectively utilizes the limited UECP storage capacity.

In short, after introducing the above-mentioned two-level caching agent system, the performance of mobile streaming media services on the GPRS network has been optimized to a large extent. Except for the wireless link between the original BTS and the MS, the performance of other links has been improved. It has been improved or upgraded, which is conducive to the expansion of mobile on-demand services.

Another advantage of the two-level cache system of the present invention is that the technical solution is transparent to users, networks and content providers. From the working mechanism of UECP and CCP, it can be seen that the two newly introduced functional entities will not affect the various network element equipment and communication protocols in the original GPRS network, without any modification to the existing network system, it can be truly transparent and seamless Work seamlessly in the original GPRS mobile network.

Description of drawings

FIG. 1 is a schematic diagram of the composition of the mobile video-on-demand service GPRS network system with two levels of buffering and performance optimization in the present invention.

Fig. 2 is a schematic diagram of the composition of the software control module of the central cache proxy CCP server of the present invention.

Fig. 3 is a schematic diagram of the structure composition of the software control module of the user boundary cache proxy UECP of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 1, the present invention is a kind of mobile video-on-demand service system based on GPRS network, performance optimization, and the network element in this network comprises at least: mobile switching center MSC/VLR, GPRS service support node SGSN (Serving GPRS Support Node) , GPRS gateway support node GGSN (GatewayGPRS Support Node), streaming media content server SCS, WAP portal server, base station system BSS and user mobile terminal MS; the improvement of this system is mainly: GGSN and external packet data in the network A central cache proxy CCP server is set on the boundary of the network PDN, and a user boundary cache proxy UECP server is set in each BSS system (that is, between the BTS and the BSC), and a high-speed IP direct link is also set up between the CCP and the UECP. Thus, a two-level cache system formed by two-level proxy servers is formed.

Only one UECP is drawn in the figure, and in actual application, each BSS system must be configured with one UECP. Each public land mobile network PLMN configures one or several CCPs, and the number depends on the business demand. All CCPs and UECPs must establish high-speed IP direct links to transmit streaming media content.

The following focuses on the functions and modules of the above two types of newly added network elements. Among them, the functions completed by the central cache proxy CCP server mainly include:

RTSP packet monitoring and on-demand ranking matching function: monitor RTSP packets between GGSN and SCS, intercept and parse RTSP request packets, extract program URLs, and then use URLs to match on-demand rankings on CCP. If the matching is successful, the request message is terminated, and the mobile terminal is responded to by the GGSN with the corresponding RTSP message; then the program content is extracted from the buffer store and sent to the mobile terminal via the IP direct link using the real-time transport protocol RTP; If the matching is unsuccessful, the RTSP request message is forwarded to the SCS.

Real-time transport protocol RTP media stream monitoring, transmission and cache replacement functions: monitor and intercept the RTP media stream from SCS to GGSN, intercept and save the program content that meets the cache replacement strategy in its cache library; responsible for the program content from SCS Or program content from the repository is sent to the user using the RTP protocol.

Create CCP on-demand list function: According to the set cycle (such as one day, one week, etc.), make statistics on the program on-demand situation or summarize the program on-demand situation reported by each UECP, and according to the ranking criteria (such as according to the level of the number of on-demand ) to make CCP's on-demand leaderboard.

See Figure 2 to introduce the main control modules and functions of the CCP server:

RTSP message filtering and forwarding module: monitor the RTSP message between GGSN and SCS, intercept and analyze the RTSP request message, extract the URL of the program, and then respond to the RTSP message that the on-demand ranking list matches successfully; or forward the on-demand ranking list Unsuccessful matching of RTSP packets.

Ranking matching module: according to the URL of the on-demand program, query the on-demand ranking in the storage module, and perform program matching; if the match is successful, then instruct the "RTP stream monitoring and transmission module" to take out the program content from the storage module and send it to the user; otherwise , and return the result of unsuccessful matching to the "RTSP packet filtering and forwarding module".

Statistical analysis module: complete the CCP on-demand ranking list and store it in the storage module;

Storage module: used to store CCP’s on-demand ranking list and all/beginning content of programs on the list;

RTP media stream monitoring and transmission module: monitor and intercept the RTP media stream from SCS to GGSN, and notify the cache replacement module to save the program media stream content that meets the cache replacement strategy in the storage module; responsible for intercepting programs from the SCS or storage module The content is sent to the user via the IP direct link using the RTP protocol.

Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy.

The functions completed by the user boundary cache proxy UECP server mainly include:

RTSP message monitoring and on-demand leaderboard matching function: monitor RTSP messages between BTS and BSC. Intercept and parse the RTSP request message, extract the URL of the program, and then use the URL to match the on-demand ranking list on UECP. If the matching is successful, the request message is terminated, and the corresponding RTSP message is used to respond to the mobile terminal through the BTS, and then the program content is extracted from the cache library and sent to the mobile terminal; if the matching is unsuccessful, the UECP forwards the RTSP request message Wen to BSc.

Monitoring, transmission and cache replacement of RTP media streams: receive RTP media streams from CCP and transmit them to BTS, and save the program content satisfying the cache replacement strategy in its cache library. It should be emphasized that in order to reduce the start-up delay of the user's on-demand program (that is, the time difference between sending the on-demand request and seeing the first frame of the picture), and considering the storage space limitation of the UECP cache library, the header cache is implemented first on UECP: That is to store the beginning part of the program on the list (for example: the content of the first 5-10 minutes before the program starts).

Create UECP on-demand list function: according to a certain period (such as one day, one week, etc.), make statistics on the program on-demand situation, and make UECP on-demand list according to certain ranking criteria (such as according to the number of on-demand times), and Statistical information is reported to the CCP. Or the UECP synchronously receives the on-demand ranking list of the CCP as its own on-demand ranking list.

Referring to Figure 3, the main control modules and functions of the UECP server are introduced:

RTSP message filtering and forwarding module: monitor RTSP messages between BTS and BSC, intercept and analyze RTSP request messages, extract program URLs, and forward unmatched RTSP messages.

Ranking matching module: according to the URL of the on-demand program, query the on-demand ranking in the storage module, and perform program matching. If the matching is successful, then instruct the "RTP transmission module" to take out the program content from the storage module and send it to the user; if the matching is unsuccessful, return the result of unsuccessful matching to the "RTSP message filtering and forwarding module".

Statistical analysis module: Complete the production function of UECP on-demand ranking list, store it in the storage module, and report statistical information to CCP regularly.

Storage module: used to store UECP on-demand rankings and all or the first part of the programs on the list;

RTP media stream transmission module: receive the RTP media stream from the CCP and transmit it to the BTS, and notify the cache replacement module to store the content of the program stream satisfying the cache replacement strategy in its cache library;

Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy.

The implementation method of the performance-optimized mobile video-on-demand service of the present invention is described below according to the process in which the mobile terminal MS initiates a VoD request to the streaming media content server SCS (Streaming Content Server). At this time, the mobile terminal has downloaded and installed the RTSP protocol streaming media terminal software. The operation steps of the performance optimization method are as follows:

Step 1: The user connects to the content publishing page of SCS through the WAP browser on the mobile terminal, retrieves the program introduction information and orders a certain program, and then clicks the hyperlink of the program, and the user sends real-time information to the SCS through the media player software installed on the terminal. Streaming protocol RTSP request, the RTSP request message contains the Uniform Resource Locator URL field for addressing the program requested by the user on the SCS server;

Step 2: The UECP server monitors the RTSP request message of the mobile terminal at the application layer, intercepts and parses the RTSP request message, extracts the URL of the program, and then uses the URL to match the on-demand list on UECP; if it matches the on-demand list on UECP If the matching is successful, perform subsequent operations; otherwise, skip to step (4);

Step 3: The UECP server terminates the RTSP request, sends a corresponding RTSP response to the mobile terminal, and then extracts the program content from the cache library, and sends it to the mobile terminal in accordance with the Um interface format using the RTP protocol. If the UECP only caches part of the content, it will request the CCP to download the subsequent part of the program file through the IP direct link, and use the Simple File Transfer Protocol TFTP/File Transfer Protocol FTP to download to the UECP to ensure the continuous playback of the user end and end the playback process ;

Step 4: The UECP server forwards the RTSP request message of the mobile terminal to the BSC, and obtains media resources according to the traditional normal on-demand process. After the CCP server monitors the RTSP request message, it intercepts and parses the RTSP request message, extracts the URL of the program, and then uses the URL to match the on-demand ranking list on the CCP. If the matching is successful, the request message is terminated and sent to the PDN, and the corresponding RTSP message is used to respond to the mobile terminal through the GGSN. Then extract the program content from the cache library and send it to the mobile terminal. The sending path is CCP→UECP→BTS→MS; if the match is unsuccessful, the CCP server forwards the RTSP request message to the SCS, and then the SCS sends the program to the mobile terminal content, the sending path is SCS→CCP→UECP→BTS-→MS, and the process ends.

Since UECP needs to implement message monitoring and transparent transmission between BTS and BSC in the GPRS network, UECP must support the Abis interface specification conforming to GPRS network; since CCP needs to realize message monitoring and interception between GGSN and SCS, CCP It is necessary to support the protocol stack conforming to the Ui interface specification of the GPRS network. In addition, since the UECP needs to interact with the CCP and can download programs from the CCP, the UECP and the CCP can use the Ui interface specification conforming to the GPRS network to realize interconnection and intercommunication.

Claims (10)

1. A performance-optimized mobile video-on-demand service system, at least including: GPRS network and each network element in the network: mobile switching center MSC, GPRS service support node SGSN, GPRS gateway support node GGSN, streaming media content server SCS, WAP portal server, base station system BSS and user mobile terminal MS; It is characterized in that: described system also comprises: The central cache proxy CCP server is set on the boundary between the GPRS gateway support node GGSN and the external packet data network PDN, which is used to alleviate the service load of the SCS, reduce the network bandwidth consumption between the GGSN and the SCS, and improve the response speed of video on demand; The User Border Cache Proxy UECP server is set in each base station system BSS, that is, between each base station controller BSC and each base station BTS, and has an adaptive cache capability based on a cache replacement strategy. By improving the cache hit rate, Ensure fast response to user video-on-demand requests; A high-speed IP direct connection link is set between the CCP server and each UECP server, and is used to transmit streaming media content between the two, and thereby the two types of proxy servers constitute two nodes of the streaming media content in the entire system. Level cache device, thereby bypassing a large number of program content streaming media, significantly reducing the data flow and processing load of other links, reducing and eliminating the impact of video-on-demand services on network performance. 2. The mobile video-on-demand service system according to claim 1, characterized in that: at least one central cache proxy CCP server is set in each public land mobile network (PLMN), and the number of configurations depends on the service demand. 3. The mobile video-on-demand service system according to claim 1, characterized in that: the functions completed by the central cache proxy CCP server further include: Monitor the real-time streaming protocol RTSP message, and then match it with the on-demand leaderboard: monitor the RTSP message between GGSN and SCS, intercept and parse the RTSP request message, extract the uniform resource locator URL of the program, and then use the URL to match On-demand list on the CCP; if the match is successful, the request message will be terminated, and the mobile terminal will be responded to through the GGSN with the corresponding RTSP message, and then the program content will be extracted from the cache library and directly linked via IP using the real-time transport protocol RTP Send it to the mobile terminal; otherwise, forward the RTSP request message to the SCS; Real-time Transport Protocol RTP media stream monitoring, transmission and cache replacement: monitor and intercept the RTP media stream from SCS to GGSN, intercept and save the program content that meets the cache replacement strategy in its cache library, and then transfer the content from SCS or cache library The program content is sent to the user using the RTP protocol; Create CCP on-demand rankings: According to the set period, make statistics on program on-demand status or aggregate statistics on program on-demand status reported by each UECP, and create CCP on-demand rankings according to the ranking criteria. 4. The mobile video-on-demand service system according to claim 3, characterized in that: the software control module in the central cache proxy CCP server includes: RTSP message filtering and forwarding module: monitor the RTSP message between GGSN and SCS, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and then respond to the RTSP message that matches the on-demand list successfully, and forward the on-demand RTSP packets that fail to match the leaderboard; Ranking matching module: according to the URL of the program on demand, query the ranking list in the storage module for program matching; if the match is successful, then instruct the "RTP media stream monitoring and transmission module" to take out the program content from the storage module and send it to the user; Otherwise, then return to " RTSP packet filtering and forwarding module " and match unsuccessful result; Statistical analysis module: complete the CCP on-demand ranking list and store it in the storage module; Storage module: used to store all or the first part of the CCP on-demand ranking list and programs included in the list; RTP media stream monitoring and transmission module: monitor and intercept the RTP media stream from SCS to GGSN, and notify the cache replacement module to save the media stream content satisfying the cache replacement strategy in the storage module; responsible for intercepting the program content from the SCS or storing it The program content of the module is sent to the user via the IP direct link using the RTP protocol. Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy. 5. The mobile video-on-demand service system according to claim 1, characterized in that: the functions completed by the user boundary cache proxy UECP server further include: Monitor the real-time streaming protocol RTSP message, and then match it with the on-demand ranking list: monitor the RTSP message between BTS and BSC, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and then use the URL to match On-demand ranking list on UECP; if the match is successful, the request message will be terminated, and the corresponding RTSP message will be used to respond to the mobile terminal through the BTS, and then the program content will be extracted from the cache library and sent to the mobile terminal; if the match is unsuccessful, Then forward the RTSP request message to the BSC; Real-time transport protocol RTP media stream monitoring, transmission and cache replacement: receive the RTP media stream from CCP and transmit it to BTS, and save the program content that meets the cache replacement strategy in its cache library; in the process of cache processing, priority is given to Header caching to make full use of the limited storage capacity of UECP; Create UECP on-demand rankings: According to the set cycle, make statistics on the program on-demand status, make UECP's on-demand rankings according to the ranking criteria, and report the statistical information to CCP; or UECP receives CCP's on-demand rankings synchronously as its own On-demand leaderboards. 6. The mobile video-on-demand service system according to claim 5, characterized in that: the header cache is to store the beginning part of the program on the list, so as to reduce the start-up delay of the user-ordered program-from sending the request to watch The time difference to the first frame to make full use of the storage space of the UECP cache library; 7. The mobile video-on-demand service system according to claim 5, characterized in that: the software control module in the UECP server includes: RTSP message filtering and forwarding module: monitor the RTSP message between BTS and BSC, intercept and analyze the RTSP request message, extract the uniform resource locator URL of the program, and forward the unmatched RTSP message; Ranking matching module: according to the URL of the program on demand, query the ranking list in the storage module for program matching; if the match is successful, then instruct the "RTP media stream transmission module" to take out the program content from the storage module and send it to the user; otherwise, Then return the matching unsuccessful result to the "RTSP message filtering and forwarding module"; Statistical analysis module: complete the UECP on-demand ranking list, store it in the storage module, and regularly report statistical information to the CCP; Storage module: used to store UECP on-demand rankings and all or the first part of the programs on the list; RTP media stream transmission module: receives the RTP media stream from CCP and transmits it to BTS, and notifies the cache replacement module to save the content of the program stream satisfying the cache replacement strategy in the storage module; accepts the instruction of the leaderboard matching module, and sends the successfully matched The program content is taken out from the storage module and sent to the user; Cache replacement module: store the program content that meets the cache replacement policy in the storage module, and replace the old program content that does not meet the cache replacement policy. 8. The mobile video-on-demand service system according to claim 4 or 7, characterized in that: the program-on-demand ranking list is a core data table maintained by the CCP/UECP server, which consists of a series of records, each record corresponding to A program in the list, a record is composed of several record items, these record items include but not limited to program number, program name, program introduction, program URL, program access address in the storage module, program price, ranking list The size of depends on the cache capacity of the CCP/UECP server. 9. The mobile video-on-demand service system according to claim 4 or 7, characterized in that: the content of the cache replacement strategy is: if a program to be ordered is in the on-demand list but has not been cached; or If a certain requested program is not in the current on-demand list, but the cumulative number of on-demand programs in the current set period has exceeded a certain threshold, the CCP/UECP server will cache the content of the program. 10. A method for implementing a performance-optimized mobile video-on-demand service, characterized in that: comprising the following steps: (1) The user connects to the content publishing page of the SCS through the WAP browser on the mobile terminal, retrieves the program introduction information, orders a certain program, that is, clicks on the hyperlink of the program, and the mobile user sends the content to the SCS through the media player software installed on the terminal. Real-time streaming protocol RTSP request, the RTSP request message at least includes the Uniform Resource Locator URL field for addressing the program requested by the user on the SCS server; (2) The UECP server monitors the RTSP request message of the mobile terminal at the application layer, intercepts and parses the RTSP request message, extracts the URL of the program, and uses the URL to match the on-demand list on the UECP; if the match is successful, perform subsequent operations; Otherwise, jump to step (4); (3) The UECP server terminates the RTSP request, and after sending the corresponding message response to the mobile terminal, extracts the program content from the cache module and sends it to the mobile terminal using the RTP protocol; The direct link requests the CCP to download the subsequent part of the program file to ensure the continuous playback of the user terminal and end the process; (4) The UECP server forwards the RTSP request message of the mobile terminal to the BSC. When the CCP server monitors the RTSP request message, it intercepts and parses the RTSP request message, extracts the URL of the program, and then uses the URL to match the URL on the CCP. On-demand leaderboard; if the match is successful, then terminate the continued sending of the request message, and respond to the mobile terminal through the GGSN with the corresponding RTSP message; then extract the program content from its cache library and send it to the mobile terminal. The sending path is Through CCP, UECP, BTS and MS in turn; if the match is unsuccessful, the CCP server forwards the RTSP request message to the SCS, and then the SCS sends the program content to the mobile terminal, and the sending path is through the SCS, CCP, UECP, BTS and MS, end of process.

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