06-02-2010, 09:22 PM
sir can request for presentation and notes
06-02-2010, 09:22 PM
sir can request for presentation and notes
07-02-2010, 07:45 AM
Video Streaming in Wireless Internet.pdf (Size: 1.49 MB / Downloads: 761) Video services are becoming an integral part of future communication systems. Especially for the upcoming 3G wireless networks such as UMTS, video may very well turn out to be the key value addition that achieves the required return of investment. While previous generations of wireless communication systems were primarily designed and used for voice services, next generation systems have to support a broad range of applications in a wide variety of settings. Novel wireless applications such as telemetric and fleet management have introduced wireless networking to the enterprise domain. At the same time the private market sector is booming with the availability of low“priced wireless equipment. The early market stages were characterized by the needs of early adopters, mostly for professional use. As the market matures from the early adopters to normal users, new services will be demanded. These demands will likely converge toward the demands that exist for wired telecommunications services. These demands, also referred to as the usual suspects, are comprised of a variety of different services †including Internet access for browsing, chatting, and gaming. In addition, entertainment services such as television, cable“TV, and pay“per view movies are demanded. With the availability of wireless services, the location is no longer of importance to private users. Thus, the demand of mobile users, connected over wireless networks will approach this mixture of services. With the omnipresence of wireless services, the usage schemes will become independent from location and connection type. One example for such a wireless service is mobile gaming. Private users, who are waiting at an airport or elsewhere, are able to join Internet“based multi-player games to bridge time gaps. Among the different entertainment services, mobile video will likely account for a large portion of the entertainment services, as are cinemas, video rentals, and television now. This application scenario covers wireless entertainment broadcasting and video on demand. A second, professional application of video in the wireless domain is telemedicine, where remote specialists are enabled to respond to emergencies. The wide area of video services in wireless environments as well as the expectations for wireless communication systems call for an understanding of the basic principles of wireless video streaming. 7 Generally, the video delivered to wireless users is either (i) live video, e.g., the live coverage of a sporting event, concert, or conference, or (ii) prerecorded (stored) video, e.g., a TV show, entertainment movie, or instructional video. Some videos fall in both categories. For instance, in a typical distance learning system, the lecture video is available to distance learners live, i.e., while the lecture is ongoing, and also as stored video, i.e., distance learners can request the lecture video later in the day or week from a video server. In general, there are two ways to deliver video over a packet-switched network (including packet-oriented wireless networks): (i) file download, or (ii) streaming. With file download the entire video is downloaded to the user™s terminal before the playback commences. The video file is downloaded with a conventional reliable transport protocol, such as TCP. The advantage of file download is that it is relatively simple and ensures a high video quality. This is because losses on the wireless links are remedied by the reliable transport protocol and the play“out does not commence until the video file is downloaded completely and without errors. The drawback of file download is the large response time, typically referred to as start“up delay. The start“up delay is the time from when the user requests the video until playback commences. Especially for large video files and small bandwidth wireless links, the start-up delay can be very large. With video streaming, on the other hand, playback commences before the entire file is downloaded to the user™s terminal. In video streaming typically only a small part of the video ranging from a few video frames to several hundreds or thousands of frames (corresponding to video play back durations on the order of hundreds of milliseconds to several seconds or minutes) are downloaded before the streaming commences. The remaining part of the video is transmitted to the user while the video playback is in progress. One of the key trade“offs in video streaming is between the start-up delay and the video quality. That is, the smaller the amount of the video that is downloaded before streaming commences, the more the continuous video playback relies on the timely delivery of the remaining video over the unreliable wireless links. The errors on the wireless links may compromise the quality of the delivered video in that only basic low quality (and low bit rate) video frames are delivered or some video frames are skipped 8 entirely. Thus, video streaming gives the user shorter start-up delays at the expense of reduced video quality. The challenge of video streaming lies in keeping the quality degradation to a level that is hardly noticeable or tolerable while utilizing the wireless resources efficiently (i.e., supporting as many simultaneous streams as possible). We note that file download and streaming with some start-up delay are suitable only for prerecorded video. The delivery of live video, on the other hand, requires an extreme form of video streaming with essentially no pre-playback download. Another consideration in the delivery of prerecorded video is user interaction (i.e., VCR functions such as fast forward, pause and rewind). Some of these interactions may result in a new start-up delay in video streaming. In this book chapter we introduce video streaming in wireless environments. We first give an introduction to the world of digital video, and outline the fundamental need for compression. Next, we introduce the basics of video compression. We show how video compression is achieved by exploiting different types of redundancies in the raw (uncompressed) video stream. We do this by following one sample video sequence on its way from the raw video to the compressed video stream. This sample video sequence is called Highway, and is publicly available [4]. Next, we introduce the characteristics of the wireless communication channel and study the impact of the wireless link errors on the video quality. Finally, we discuss the different protocols and adaption techniques for streaming the video content over the wireless channel. The model of a transmission chain of a general wireless communication system for video streaming is given in Figure 1. At the sender side the video source is passed to the video (source) encoder. The compressed video stream is passed to the transport process which in turn passes the stream plus some overhead information to the channel coder and modulation part for transmission over the wireless link. At the receiver side the process is reversed. please read http://csplab.kaist.ac.kr/paper/Power-di...%20VBR.pdf http://ieeexplore.ieeeXplore/login.jsp?u...ision=-203
10-08-2011, 10:12 PM
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11-08-2011, 09:43 AM
To get more information about the topic " Wireless Video Service in CDMA Systems" please refer the link below
https://seminarproject.net/Thread-wirele...9#pid54229
03-02-2013, 08:34 PM
05-02-2013, 12:34 PM
Wireless Video Service in CDMA Systems
Wireless Video Service in CDMA Systems.docx (Size: 28.9 KB / Downloads: 22) Abstract of Wireless Video Service in CDMA Systems Video services are becoming an integral part of future communication systems. Especially for the upcoming 3G-CDMA system wireless networks such as UMTS, video may very well turn out to be the key value addition that achieves the required return of investment. While previous generations of wireless communication systems were primarily designed and used for voice services, next generation systems have to support a broad range of applications in a wide variety of settings. The early market stages were characterized by the needs of early adopters, mostly for professional use. As the market matures from the early adopters to normal users, new services will be demanded. These demands will likely converge toward the demands that exist for wired telecommunications services. Market research finds that mobile commerce for 3G wireless systems and beyond will be dominated by basic human communication such as messaging, voice, and video communication [1]. Because of its typically large bandwidth requirements, video communication (as opposed to the lower rate voice and the elastic e-mail) is expected to emerge as the dominant type of service in 3G/4G wireless systems. Video services obth real-time services and streaming services are gaining a lot of importance and applications in CDMA systems. There are three ways to spread the bandwidth of the signal: • Frequency hopping. The signal is rapidly switched between different frequencies within the hopping bandwidth pseudo-randomly, and the receiver knows beforehand where to find the signal at any given time. • Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the receiver knows beforehand when to expect the burst. • Direct sequence. The digital data is directly coded at a much higher frequency. The code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data. These direct sequence spread spectrum signals can be digitized voice, ISDN channels, modem data, etc. Why real-time video Traffic is difficult to handle Video Requires Extremely Large Bitrate – Large Bandwidth Requirement for Video Sources vs. Limited Resources of Wireless Networks. – High Compression Ratio Bitstreams Extremely Sensitive to Channel Errors and Network Impairments. – Stringent Latency Requirements. Compressed Video Requires Error Protection – Most Existing Video Compression Standards Originally Not Designed for Lossy Channels. – Appropriate Error Protection Schemes: an Important Research Topic. Video Streaming over CDMA-Based Wireless Networks In video streaming services, the playout begins when the queue length of the receiver buffer is above a threshold. This threshold must be large to reduce the buffer underflow probability and absorb the bit rate variations caused by the wireless channel. On the other hand, it is important to reduce this threshold in order to reduce the initial playout delay and also the size of the receiver buffer. Here a video streaming service is considered, where the last link is a wireless CDMA-based link and it has been shown how a truncated power control allows to reduce the pre-roll delay without increasing the average transmission power and without degrading the video quality. It presents the proposed truncated power control and an analytical model to evaluate the achievable pre-roll delay reduction. System Model The system model consists of a source, a server and a client. As shown in Figure 2, the video streaming passes through a wired network without losses and a lossy wireless link with CDMA-based transmission. The source can be a live program or a prestored program; in the first case the source passes a video frame to the server every t seconds, while in the second case the source passes all of the video frames to the server at the beginning of the session. The server is responsible of delivering video frames from the source to the client through a heterogeneous wired/wireless network; in this paper we refer to a UDP-based transport platform. The UDP protocol does not permit to recover from data losses and this functionality is left to the link. The server encapsulates each video frame within a UDP packet and each packet is enqueued into the UDP transmission buffer. Both at the server side and at the client side a link layer ARQ buffer and a playout/UDP buffer are needed. At the client side, the playout begins when the queue length n of the playout buffer is above a specified threshold Npr. Such a phase is called pre-roll process and it is needed in order to reduce the buffer underflow probability at the expenses of an initial delay (pre-roll delay). At the client side, underflow occurs when n = 0; after the buffer underflow occurrence the receiver temporarily suspends the playout of the video and a new pre-roll process starts. Both the pre-roll delay and the buffer underflow probability depends on the pre-roll threshold Npr and on the channel reliability. Large Npr results in a small underflow probability but increase the pre-roll delay.It is common for streaming media clients to have a 5 to 15 seconds of buffering delay before playback starts. Video Conferencing Videoconferencing is a medium where two or more people at different locations can meet face-to-face in real time .Offers new possibilities to connect with guest speakers and experts.Can make relevant learning opportunities more accessible and exciting. Videoconferencing is the conduct of a videoconference (also known as a video conference or video teleconference) by a set of telecommunication technologies which allow two or more locations to communicate by simultaneous two-way video and audio transmissions. It has also been called 'visual collaboration' and is a type of groupware . Videoconferencing uses audio and video telecommunications to bring people at different sites together. This can be as simple as a conversation between people in private offices (point-to-point) or involve several (multipoint) sites in large rooms at multiple locations. Besides the audio and visual transmission of meeting activities, allied videoconferencing technologies can be used to share documents and display information on whiteboards.
05-03-2013, 12:06 PM
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