Mohd Ayyub Khan

Error resilient technique for SPIHT coded color images

The Set Partitioning in Hierarchical Trees (SPIHT) based color image coder, commonly referred as Color SPIHT (CSPIHT) are developed to quantize and encode wavelet coefficients and have excellent rate distortion characteristic in the noise free environments. However in presence of noise they are extremely sensitive to the bit errors. It was observed that bits have different degree of vulnerability of errors. The error in some of the bits (critical bits) causes the severe degradation while errors in other bits (non-critical bits) have negligible effect in the reconstructed images. In this paper, we propose an unequal error protection (UEP) scheme, in which within each bits plane, the bits are reorganized according to their sensitivity of errors and then critical bits are protected unequally using Rate Compatible Puncturing Convolutional (RCPC) codes. The protection is reduced for higher bit-planes, by changing the puncturing rate. The simulation results show an improvement of 5–15 dB in the quality of reproduced images, as compared to the equal error protection (EEP) and unprotected CSPIHT bit-stream.

Physical layer unequal error protection of wavelet coded video using Hierarchical QAM

Unequal Error protection (UEP) of wavelet coded video is investigated using Hierarchical Quadrature Amplitude Modulation (HQAM). Based on the unequal sensitivity of coded bit stream against transmission errors, this paper investigates the properties of HQAM constellation to provide different degree of error protection to the coded bits having different degree of importance. This paper proposes an UEP scheme, performed at the physical layer using HQAM to protect higher priority (more sensitive) bits strongly without any additional bandwidth, but at the cost of increased errors in the lower priority (less sensitive) bits. The performance of the transmission system is evaluated under the Additive White Gaussian Noise (AWGN). Simulation results verify the improvements in the performance.

Optimized cross-layer unequal error protection for wireless video communication

Error control strategies to video bitstream are usually provided at different layers of the communication network. Optimizing the error control strategies at different layers independently leads to inefficient utilization of the resources. In this paper, a cross-layer strategy to optimally utilize the application and physical layer resources for unequal error protection (UEP) of wavelet coded scalable video is investigated. We propose a cross-layer optimized UEP scheme, combining optimal forward error correction (FEC) at application layer and hierarchical QAM (HQAM) at physical layer. A look-up table-based approach, to select optimal parameter values at both layers that maximizes the overall video quality for a given channel condition, is suggested. A wide range of video sequences of different degree of motion and texture are considered to design the look-up table. The major advantage of the look-up table based approach is the low computation complexity of the transmission system, which is one of the major issue in portable video communication devices. Simulation results show the proposed scheme outperforms other techniques comprehensively over a wide range of channel conditions.

Unequal error protection (UEP) of wavelet coded video using multi-layered Hierarchical QAM

In this paper, the performance of unequal error protection (UEP) scheme for wavelet coded video using multi-layered 64-Hierarchical QAM (64-HQAM) is presented. Depending on the error sensitivity of coded video bitstream against channel errors, the bitstream is partitioned into multiple sub-streams. The most sensitive sub-stream is assigned highest protection while least sensitive are assigned lowest protection by adjusting the distance between points in the constellation diagram of HQAM. The performance of the communication system is evaluated for Additive White Gaussian Noise (AWGN) channel. The simulation results demonstrate that three-layer UEP provides increased Quality-of-Service (QoS) compared to level two-layer UEP.

Efficiently-mapped adaptive hierarchical QAM for reliable scalable video communication

This paper proposes an efficiently-mapped adaptive hierarchical QAM (AHQAM) scheme for unequal error protection (UEP) of embedded video bitstream. The coded bits of each frame are hierarchically partitioned into high priority (HP) and low priority (LP) substream, using two-staged partitioning strategy. Then pairs of stream blocks, one from each substream are selected judiciously to form symbols, which are modulated using HQAM with varying modulation parameter. The proposed scheme is generic in nature and can be applied to any scalable video bitstream. Simulations are performed with 16-AHQAM for AWGN channel and it is observed that the proposed scheme offers up to 7.2 dB improvement in quality of received video as compared to 16-HQAM.

Optimized unequal error protection of embedded video bitstream using adaptive-hierarchical QAM

In this paper, a reliable video communication system using adaptive Hierarchical QAM (HQAM) is designed to provide optimized unequal error protection (UEP) to embedded video bitstreams. Based on the relative importance of bits, video bitstream is partitioned into two priorities, namely High Priority (HP) and Low Priority (LP) substreams. Then, the optimal value of modulation (or hierarchical) parameter (α) of HQAM, which controls the relative error protection of these substreams, is selected from a pre-designed look-up table. The proposed system adapts itself by adapting the optimal α according to the varying channel condition, without changing the modulation level. This is in contrast to conventional WiMAX and LTE systems, in which dynamic switching among multiple modulations is used to adapt the varying channel conditions. This paper proposes HQAM with adaptive α as an alternative to the multiple modulation schemes. Moreover, for fixed average transmission power, receiver demodulates symbols without the knowledge of α. In order to further improve the video quality and to reduce the effects of erroneously received LP bits, the proposed system uses another level of adaptation, in which received LP bits are adaptively considered or discarded, before decoding the video, depending on the channel conditions (or optimized α). Simulation results show that proposed system can achieve significant improvement in the video quality compared to QAM based EEP scheme and non-adaptive HQAM.

Unequal error protection of embedded video bitstream with optimized FEC

In this paper, an optimized unequal error protection scheme using Forward Error Correction (FEC) for transmission of embedded video bitstream over AWGN channel is investigated. The scheme exploits the non-uniform importance and error sensitivity of the bits generated by the a wavelet video coder. Depending upon their importance in the reconstruction of the video, the bitstream is first divided into High Priority (HP) and Low Priority (LP) substreams. Then appropriate FEC is applied to these substreams to protect them against the channel errors. The optimal FEC parameters are searched using an offline optimization technique subject to constraint that end-to-end transmission distortion is minimized. A look-up table with optimal FEC parameters for wide range of channel conditions, is designed. Furthermore, this paper also argues that whether optimized UEP has any advantage over EEP for protection of embedded bitstream. This scheme is suitable for real-time video communication using portable devices which possess low processing capabilities and small battery power.

Performance investigation of application layer unequal error protection for embedded video bitstream

The wavelet-based video coders are excellent in providing the fine granular scalability (FGS), i.e. progressive bitstream, which can be used to multicast the video transmission to different users requiring different bit-rate, resolution and frame rate, from single coded bitstream. However, transmission of these bitstreams over erroneous channel is a challenging task. In this paper, application layer unequal error protection (UEP) using RS codes to embedded video bitstream transmitted over Additive White Gaussian Noise (AWGN) channel is investigated. The UEP of embedded bitstream exploits the non-uniform importance of the bits, in the reconstruction of the video. The bitstream is partitioned into two substreams namely, high priority (HP) and low priority (LP), depending upon their importance and sensitivity to channel errors. Then FEC based error protection is provided to them according to their priority. The results show that, under poor channel conditions, the UEP scheme improves the quality of the reconstructed video over EEP scheme for AWGN channel.