外文翻譯(外文).pdf

A Novel System Architecture for Mobile Campus Information Push Systems Huabing Zhang Guibo Luo and Yuesheng Zhu Communication revised February 27 2013 Mobile PubSub systems like RSS reader push information on demand But they mainly adopt HTTP polling mode to request updated information which is time consuming and resource consuming 2 Since the pushed information is closely related to the education and intramural life it should be protected from being leaked to unauthorized users However current mobile instant messaging systems and mobile PubSub systems introduced before are rarely aiming at campus and not appropriate to be used in campus without any modification Furthermore they are restricted on delivering text message rare dabble in multimedia information which is required by digital campus systems So designing a subscribable instant content rich and cost effective intramural information push system is very significant Mobile instant messaging system and mobile PubSub system have their own advantages A good practice is to combine the two systems together In the paper 3 Zhonghua Wang Xiaoli Xiong and Yongguang Hou proposed a campus mobile learning solution based on RSS subscription SMS and mail push methods It is a hybrid system combining the RSS PubSub system and SMS push But the RSS HTTP polling technology is not real time the SMS push is not cost effective and users who can subscribe information are browser users but not mobile users AS to mail push method it can t achieve high acceptance rate At present domestic and foreign researches on mobile information push technology are mainly limited to instant messaging systems and PubSub systems separately In this paper a novel system architecture which integrates the PubSubHubbub XMPP and RTMP is proposed And an effective android campus information push system based on this novel hybrid architecture is designed and implemented combining the virtues of real time subscribable content rich and cost effective The remaining parts of this paper describe the follows The system architecture and relevant protocols are expounded in section II the corresponding technical realization is narrated in section III the experimental results of this system are demonstrated in section IV and in the end in section V we summarize and draw conclusions II THE PROPOSED SYSTEM ARCHITECTURE Lecture Notes on Information Theory Vol 1 No 1 March 2013 64 2013 Engineering and Technology Publishing doi 10 12720 lnit 1 1 64 68 A mobile campus information push system is developed based on the proposed system architecture shown in Fig 1 which mainly consists of push resource website push proxy server android push client and streaming media server The communication between push resource website and push proxy server is based on the PubSub protocol PubSubHubbub The publisher which is the push resource website publishes various information resources such as intramural news notices and video courseware And also takes the burden of visit from the browser The communication protocol between push proxy server and android push clients is the instant messaging protocol XMPP The push proxy server acts as a subscribe proxy forwards not only the subscription requests to the Publisher but also the updated information to the android push clients Push proxy server is the interface of PubSub protocol and instant messaging protocol and is separated from the push resource website which exempts the website from keeping persistent connections with android clients and greatly reduces its burden The streaming media server which affords streaming media service uses RTMP protocol to handle the streaming media requests from both browser clients and android clients Android push clients are the terminals of this information push system can subscribe and receive information WiFi 3G GPRS Browser Client Database Push proxy server 1 Red5 origin Push resource website Red5 edge 2Red5 edge 1 Push proxy server2 Streaming media server cluster NewsNotifications Video courseware Android push client 1Android push client 2 Figure 1 Fig 1 System architecture A PubSubHubbub Protocol PubSubHubbub 4 is a server to server PubSub protocol between the push resource website and push proxy server in this system PubSubHubbub adopts HTTP non polling mode which is real time and cost effective enables subscribers to receive the updated information from publishers as soon as the information subscribed is updated Hence the subscribers do not need to query the resource website continually The PubSubHubbub consists of three parts Publisher Hub and Subscriber and two stages the subscribe stage and the publish stage PublisherHubSubscriber 3 submit topic RTMPS protocol which is over HTTPS and offers a secure connection and RTMPE protocol which is an encryption version of RTMP These versions can be adopted in our system III TECHNICAL REALISATION The push resource website is built based on the open source blog platform wordpress and the Hub in PubSubHubbub protocol is built with the wordpress plug in pushpress Here we combine the Publisher and Hub together to eliminate the HTTP request and response process between them As a result the whole system delay is lower Fig 4 explains this Publisher Hub combined Subscriber New content Figure 4 The Publisher Hub combined Androidpn Server Androidpn ClientSession 1 register 2 create client session 3 maintain cliient state 4 push message 5 send message through session 6 client close 7 logout server session Figure 5 Androidpn workflow The realization of the instant messaging part between the push proxy server and android push clients is based on the second development of the open source android push platform androidpn Androidpn 7 is developed in java implements the XMPP protocol both on server and client XMPP adopts Mina framework to manage socket connections which is really suited for high concurrent information push situation because of Mina s non blocking feature The workflow of androidpn is shown in Fig 5 1 The client opens up the client side application sets up a persistent connection to androidpn server and sends registration information 2 After finishing registration the server establishes a corresponding session for the client registered which is used to manage client s state 3 Server sends message to the sessions alive via socket connections Client receives the message parses it and shows the message Spring Hibernate technology and Mina framework are used in androidpn server In the top of the androidpn server structure shown in Fig 6 there are four important parts Session Manager Auth Manager Presence Manager and Notification Manager Session Manager is responsible for the session management between clients and server Auth Manager is responsible for user authentication Presence Manager is responsible for clients status management And Notification Manager is in charge of pushing information from server to clients Androidpn client has integrated the asmack which is the XMPP client side implementation for android Androidpn leaves a power of work such as manage connection send message and other laboring work to server but creates lightweight clients This is praisable for reducing android client power consumption and client burden The subscriber of the PubSubHubbub protocol is implemented in java and integrated with the androidpn server together to form the push proxy server The push proxy server shares the user database with the push resource website Subscribe view details video display and video broadcast functions are all implemented in the android push client To provide streaming media service as well as possible red5 is adopted as the streaming media server Red5 8 is an open source server supports RTMP RTMPT RTMPS RTMPE protocols and flv f4v mp4 format video and mp3 aac format audio Since streaming media consumes huge swathes of bandwidth it is critical on server performance So cluster the red5 to provide better QoS is a must The cluster of red5 divides into two classes the red5 origin and the red5 edge Red5 origin is the server where releases videos and the red5 edges are cluster servers do not release videos but obtain videos from the red5 origin and then forward to clients In the red5 cluster a red5 origin corresponds to several red5 edges Fig 7 shows the cluster architecture The connections between red5 origin and red5 edges are MRTMP connections on port 9035 and the connections between red5 edge and clients are RTMP or RTMPT connections Actually one MRTMP connection is the RTMP or RTMPT Lecture Notes on Information Theory Vol 1 No 1 March 2013 66 2013 Engineering and Technology Publishing connections multiplexing By this way the workload of streaming media servers is reduced and the clients can not access directly to the red5 origin which protects the security of the media Session Manager Auth Manager Presence Manager Notification Manager IO Handler Stanza Handler IQ Handler Admin Console Spring FrameworkMinaJetty Java SE 6 Runtime Figure 6 Androidpn server structure Red5 origin Red5 edge n Red5 edge 1 MRTMP RTMP MRTMP RTMP Android client2 Android client m Android client1 RTMP Figure 7 Red5 cluster TABLE I COMPARISON OF PULL PURE PUSH AND PUSH PUBSUB Pull Pure Push PubSub Push Description Android clients polling for message from website continually Website broadcast message to all android clients immediately Clients subscribe topics website publishes message push server pushes notifications clients pull detail message Latency Depend on polling interval high commonly Low Low Server consumption Little Website takes most work Website is only responsible for publishing while push server is responsible for pushing Client consumption Large Little Little Subscribe capability Good None Good IV SYSTEM TEST RESULTS This novel hybrid mobile campus information push system is based on the PubSub Push scheme proposed above Table I shows the comparison of the traditional http pull scheme pure push scheme and the proposed pubsub push scheme and we can find the advantage of the pubsub push scheme on mobile campus information push system obviously The proposed system is not only designed but also implemented in a real environment It is very convenient and prompt for the android push clients to subscribe topics and receive information over WiFi WCDMA GSM Fig 8 shows the system push delay between the time when push resource website publishes one message Hello World and when all android push clients receive it The result in Fig 8 shows that the way of pushing information over WiFi has the lowest delay about 200 milliseconds to 40 android clients while the GSM way consumes about 900 milliseconds the delay of the WCDMA way falls in between them about 400 milliseconds Either way the system proves efficient in its practical use And the delay increases very slowly with the android push clients growing So this mobile information push system proves stable The system effectiveness is demonstrated in Fig 9 Fig 10 and Fig 11 Fig 11 shows the received video playing on android mobile and the live video broadcasting on one android mobile and playing on another android mobile and our website System push delay 0 200 400 600 800 1000 102030405060708090100 Android push clients Delay ms WiFi WCDMA GSM Figure 8 Fig 8 System push delay Figure 9 Push resource website Figure 10 Subscribe and receive information on android Lecture Notes on Information Theory Vol 1 No 1 March 2013 67 2013 Engineering and Technology Publishing Figure 11 RTMP video play and live broadcast V CONCLUSION Traditional mobile instant messaging systems and mobile PubSub systems cannot meet the need of mobile digital campus system A novel mobile campus information push system which combines the PubSubHubbub XMPP and RTMP is designed and implemented in this paper This system intends to enable publishers to publish intramural information like notices and video courseware to subscribers effectively and enable subscribers to accept notices and watch videos including live videos both on android mobile terminals and on our website The experimental results of this system indicate that the combination proposed is an effective way to establish a real time subscribable content rich stable reliable and cost effective mobile campus information push system ACKNOWLEDGMENT The work described in this paper was supported by the 973 Program 2012CB315904 China and the Research Program of Shen