Wireless Video StreamingPapersPerformance of H.263 Video Transmission over Wireless Channels Using Hybrid ARQConcatenated Hybrid ARQPowerPoint PresentationSlide 6Coding using CH-ARQDecoding using CH-ARQPerformance AnalysisSlide 10Slide 11Slide 12Slide 13Simulation of H.263Slide 15Slide 16Feedback-Based Error Control for Mobile Video TransmissionMotion-Compansated Hybrid CodingDecoding the Erroneus Video Bit StreamSlide 20Slide 21Error Mitigation by FeedbackSlide 23Slide 24Video Transmission over a Wireless DECT ChannelWireless MPEG-4 Video Communication on DSP ChipsDSP processorsSlide 28MPEG-4Slide 30ImplementationPerformance of the MPEG-4 implementationSlide 33Wireless Video StreamingWireless Video StreamingMikko RuotsalainenHUTPapersPapers”Performance of H.263 Video Transmission over Wireless Channels Using Hybrid ARQ,” H.Liu, and M. El Zarki, IEEE Journal on Selected Areas in Communications, Vol. 15, No. 9, Dec. 1997, pp. 1775-86”Feedback-Based Error Control for Mobile Video Transmission,” B. Girod, and N. Farber, Proceedings of the IEEE, Vol. 87, No. 10, Oct. 1999, pp. 1707-23”Wireless MPEG-4 Video Communication on DSP Chips,” M. Budagavi, W.R. Heinzelman, J. Webb, and R. Talluri, IEEE Signal Processing Magazine, Jan. 2000, pp. 36-53Performance of H.263 Video Performance of H.263 Video Transmission over Wireless Transmission over Wireless Channels Using Hybrid ARQChannels Using Hybrid ARQConcatenated Hybrid ARQConcatenated Hybrid ARQtwo conventional hybrid ARQ schemes–type-I parity bits for both error detection and error correction in every transmitted packetif error can not be corrected, packet is rejected and retransmission is requested –type-IIerroneus packet is kept for future rather than discarded like in type-I schemeredundancy bits are transmitted only when needed (more and more redundancy is sent until errors can be corrected)CH-ARQ–based on Reed-Salomon and rate-compatible punctured convolutional (RCPC) codes–combines the advantages of both type-I and type-II schemescertain error correction capability with every packetthe information can be recovered from each transmission or retransmission aloneretransmitted packet contains redundancy bits, which combined with previous transmitted packet, result powerful RS/convolutional concanated code–employs three codes C0, C1 and C2 C0 is cyclic redundancy check (CRC) code used for error detectionC1 is RCPC code for error correctionC2, is half-rate invertible shortened Reed-Salomon code for both error detection and correction–code rate at the RCPC can be selected according to the channel conditionsCoding using CH-ARQCoding using CH-ARQ1. Using RS code form parity block P(D). (D,P(D)) is code word in C2.2. k information (D) blocks are interleaved and CRC based on C0 is attached to interleaved blocks to form macroblock I.3. I is encoded with RCPC encoder and information packet is transmitted to the receiver4. If no ACK is received, states 2 and 3 are performed for parity blocks P(D) to form parity packet.Decoding using CH-ARQDecoding using CH-ARQ1. Decode using RCPC2. CRC check3. If no error is detected send ACK, else deinterleave and store received information packet4. Do 1 and 2 for parity packet.5. If no error is detected, invert parity packet to get the information, else combine parity packet with information packet to form RS code6. Error correction is performed on the RS codePerformance AnalysisPerformance AnalysisFor the performance analysis Multistate Markov channel model (MSMC) is used to model the fading radio channel –Bit-error rate (BER) and SNR change over time –the channel quality at any instant depends on the previous channel condition–model is constructed by partitioning the range of SNR into multiple intervals–each state in MSMC correspond to one interval and is characterized by particular BER–probabilities for state transitions derived from the Rayleigh fading channel model–assumptions: fading is slow, transtions happen only after packet transmission and state can change only to it’s neighboring statesNumerical results –CH-ARQ over MSMC modeled radio channel–RCPC rates 1, 4/5 and 4/8, Viterbi decoder–under a certain channel condition it is possible to find optimal code rate that yields low RPER and high throughputSimulation of H.263Simulation of H.263CH-ARQ error control scheme is simulated in H.263 video transmissionRayleigh fading simulator is used to simulate the radio channel (instead of MSMC used in numerical analysis)average peak-signal-to-noise ratio (PSNR) and objective video qualitity assesment using grade point (GP)for each channel SNR there is RCPC rate that maximizes visual quality (adaptive algorithm)Feedback-Based Error Control for Feedback-Based Error Control for Mobile Video TransmissionMobile Video TransmissionMotion-Compansated Hybrid CodingMotion-Compansated Hybrid Codingtwo modes: INTRA and INTER coding–INTRA: intraframe is coded with no reference–INTER: motion-compansated prediction is carried out by estimating the motion between successive frames and the residual is intraframe codeH.263 coding standard–each picture is divided into macroblocks (MB)–each MB is either INTRA or INTER coded–in INTER mode one motion vector / MB–a fixed number of MB´s form group of block (GOB)–for low-bit rate acceptable image qualityDecoding the Erroneus Video Bit Decoding the Erroneus Video Bit StreamStreamerror detection and resynchronization–a single bit error may cause loss of synchronization, since variable length code (VLC) words are used–GOB headers are used as resynchronization points (previous GOB discarded entirely)–errors can be detected using forward error correction (FEC)–video decoder itself can detect errors (syntax violations)error concealment–the visual effect of errors is minimized using error concealment techniques–simplest and most common approach is corrupted pixels are replaced pixels from previous framenot very good approach when heavy motion–motion vectors can be used for motion-compansated concealment error propagation–errors remaining after the concealment propagate to successive frames and stay visual for long time–decay of propagation determined by two effectssome blocks encoded in INTRA mode (stops propagation)spatial filtering in motion-compensated predictorError Mitigation by FeedbackError Mitigation by Feedbackerror