Iterative Detection Aided H.264 Wireless Video Telephony Using Irregular Convolutional Codes

Abstract

Abstract-In this paper we evaluate the performance of a DataPartitioned (DP) H.264 coded video transmission system using Unequal Error Protection (UEP) IrRegular Convolutional Codes (IRCC). Using UEP, perceptually more important bits are provided with more strong protection relative to less important bits. An iterative detection aided combination of IRCC and a rate-1 precoder was used to improve the overall BER performance and to enhance the objective video quality expressed in terms of Peak Signal-to-noise Ratio (PSNR). The effect of different error protection schemes on the attainable system performance is demonstrated, while keeping the overall bit-rate budget constant for the transmission of DP H.264 source coded video over correlated narrowband Rayleigh fading channels. In this paper we exploited the high design flexibility of IRCCs, which constitutes a family of different rate subcodes, while maintaining an excellent iterative decoding convergence performance. Additionally, due to the use of different-rate subcodes, IRCCs have the capability of providing UEP for the H.264 coded video stream. An EXIT chart matching procedure was used for the design of our specific IRCC. Additionally, EXIT charts were used for analysing the attainable system performance of various error protection schemes employed. Explicitly, our experimental results show that the proposed UEP scheme using IRCC outperforms its Equal Error Protection (EEP) counterpart employing regular convolutional codes by about 0.5 dB E b /N 0 at the PSNR degradation point of 1 dB. I. MOTIVATION AND BACKGROUNDMultimedia source coded information, such as speech, audio and video typically exhibit unequal sensitivity to channel errors [1,2]. Therefore, Unequal Error Protection (UEP) is used by exploiting the innate UEP capability of IrRegular Convolutional Codes (IRCCs) due to the employment of various constituent codes having different coding rates to ensure that the perceptually more important bits suffer from a lower number of channel errors. The construction of IRCCs was studied by Tuchler and and Hagenauer [3], where a family of different convolutional codes having various coderates were designed with the aid of EXIT charts for achieving an improved iterative decoding behaviour for a serially concatenated system. For wireless multimedia applications maintaining both a high compression efficiency as well as a high integrity, while communicating over heterogeneous communication networks is of primary importance. Therefore, to evaluate the performance of our proposed error protection schemes, we used the high-compression efficient and network-friendly H.264/AVC source codec [4], which employs various variable length coding and predictive coding techniques to achieve compression efficiency. However, these coding techniques make the compressed bit-stream more vulnerable to the effects of channel errors. Due to variable length coding a single bit error in the video stream may render the correct decoding of future code words impossible. Moreover, due to predic...