Clency Perrine

A robust joint source channel coding scheme for image transmission over the ionospheric channel

In this paper, we propose a joint source channel coding (JSCC) scheme to the transmission of fixed images for wireless communication applications. The ionospheric channel which presents some characteristics identical to those found on mobile radio channels, like fading, multipath and Doppler effect is our test channel. As this method based on a wavelet transform, a self-organising map (SOM) vector quantization (VQ) optimally mapped on a QAM digital modulation and an unequal error protection (UEP) strategy, this method is particularly well adapted to low bit-rate applications. The compression process consists in applying a SOM VQ on the discrete wavelet transform coefficients and computing several codebooks depending on the sub-images preserved. An UEP is achieved with a correcting code applied on the most significant data. The JSCC consists of an optimal mapping of the VQ codebook vectors on a high spectral efficiency digital modulation. This feature allows preserving the topological organization of the codebook along the transmission chain while keeping a reduced complexity system. This method applied on grey level images can be used for colour images as well. Several tests of transmission for different images have shown the robustness of this method even for high bit error rate (BER>10^-^2). In order to qualify the quality of the image after transmission, we use a PSNR% (peak signal-to-noise ratio) parameter which is the value of the difference of the PSNR after compression at the transmitter and after reception at the receiver. This parameter clearly shows that 95% of the PSNR is preserved when the BER is less than 10^-^2.

Impact of realistic MIMO physical layer on video transmission over mobile Ad Hoc network

In this paper we investigate the impact of a realistic physical layer on the H.264/AVC video transmission over Ad Hoc networks in urban environment. We propose a realistic Multiple Input Multiple Output (MIMO) physical layer which combines a determinist propagation model and a fine-grained model of wireless transmission errors. The determinist propagation model takes into account all the environmental characteristics (geometric and electric) and provides all the information of the multi-path channel (received power, complex impulse response). The wireless transmission errors model is based on a BER computation. The BER is calculated according to 802.11n standard to evaluate MIMO wireless links and, then, is compared to both SISO configuration and an existing wireless errors model using empirical propagation models. In the case of a SISO configuration, the BER is computed according to 802.11a standard. The simulation results show clearly a significant difference in term of QoS for the video transmission using realistic and empirical physical layer. In addition, the MIMO system, compared to a SISO one, improves the quality of links in the network and, thus, provides a better QoS for video transmission over Ad Hoc networks.

A solution to efficient power allocation for H.264/SVC video transmission over a realistic MIMO channel using precoder designs

In this paper we propose a novel scheme for real time SVC-based video transmission over MIMO channels in the context of Joint Source Channel Coding (JSCC). This scheme compares the transmission of the H.264/SVC video over four precoder solutions, namely Max-SNR, WF, QoS and E-dmin. We exploit the high flexibility of the QoS precoder to minimize the total distortion of the received video. The proposed adaptive QoS precoder takes into account the scalability of the H.264/SVC standard jointly with the instantaneous MIMO channel statue. Finally, the proposed scheme is evaluated over both statistical and time Optimal power allocation varying realistic MIMO channels. This study provides the performance of these four precoder designs in term of BER, ML decoder complexity and the quality of the received video. We show that the precoder solutions providing the best BER MIMO channels performance are not usually the most appropriate for real time video transmission. However, the adaptive QoS precoder which uses three configurations, by considering both the importance of the video bit-QoS precoder stream and the channel statue, provides the best Rate-Distortion performance regardless the channel conditions. We assess the accuracy of these four precoder solutions against channel estimation errors over time varying realistic MIMO channel. The results shows that the adaptive QoS precoder remains robust against channel estimation errors even at high mobility speed.

Optimal resource allocation for Medium Grain Scalable video transmission over MIMO channels

In this paper we investigate an optimal solution for adaptive H.264/SVC video transmission over Multiple-Input Multiple-Output (MIMO) channels. We first write the end-to-end distortion of the H.264/SVC video transmission over a diagonal MIMO channel. The total distortion is expressed following three physical layer parameters: power allocation, modulation spectral efficiency and Error Code Correction (ECC) code rate. Minimizing the total distortion is considered as an optimization problem containing both discrete and continuous variables. We use the Lagrangian method associated with Karush-Kuhn and Tucker conditions to find out the optimal continuous physical layer parameters. Concerting the discrete modulation spectral efficiency and ECC code rate, we exploit information of the MIMO system to remove all suboptimal configurations. Therefore, the optimal power allocation is computed only for a reduced number of discrete configurations. The performance of the proposed solution is evaluated over both statistical and realistic MIMO channels. Results show that the proposed solution performs an optimal resource allocation to achieve the best QoS regardless the channel conditions.

A comparison of several gradient based optimization algorithms for PAPR reduction in OFDM systems

The aim of this paper is to evaluate and compare different optimization algorithms for Peak to Average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems. Based on Tone Reservation (TR) method, we exploit the unused subcarriers of the studied standard to generate the peak canceling signal without data rate loss. Gradient, Conjugate-Gradient with two directions search and QuasiNewton methods have been investigated and evaluated on the basis of spectral regrowth, convergence speed and ability to improve the high peak-to-average reduction in multicarriers systems. As an example, the simulations are performed in the case of Local Area Network WLAN (IEEE 802.11a standard). Simulation results show that a PAPR reduction gain around 3 dB can be achieved.

A robust content-based JPWL transmission over a realistic MIMO channel under perceptual constraints

This paper proposes a global approach of JPWL (ISO/IEC 15444-11) image transmission over a realistic wireless channel able to ensure the best Quality of Service (QoS). In order to exploit the channel diversity, we consider a Closed-Loop MIMO-OFDM scheme with different precoder designs. In particular, the high flexibility of QoS precoder allows taking into account the scalability of JPWL jointly with the instantaneous MIMO channel status. This increases the visual quality of received images. The monitoring of the quality is made by a reduced-reference metric (QIP) based on objects saliency and interest point, both linked to human perception. It is performed in association with a robust JPWL decoder to determine the optimal decoding configuration in terms of PSNR. The proposed scheme provides very good results and its performance is shown through a realistic wireless channel.

Low-complexity and optimal resource allocation scheme for scalable video transmission over realistic noisy MIMO channels

We investigate a joint source-channel coding solution for H.264/SVC video transmission over noisy MIMO channels. To exploit the channel diversity, we use a closed-loop MIMO scheme, which allows the decomposition of the MIMO channel into several hierarchical SISO subchannels. The scalable video bit stream is divided into hierarchical quality layers (base layer and enhancement layers) which are passing through the SISO subchannels. For each subchannel, an adaptive modulation, an unequal error protection and an unequal power allocation are provided according to the channel state information. The contribution of our work is to provide an optimal and low-complexity method that jointly parameterizes the system elements connected to the video contents and the physical layer. The performance of our proposal is evaluated over a realistic noisy MIMO channel. The results disclose that the proposed solution optimizes the complexity and performs an optimal resource allocation to achieve the best QoS in term of PSNR regardless of the severity of channel conditions.

Optimal solution for SVC-based video transmission over a realistic mimo channel using precoder designs

In this paper we propose a novel scheme for SVC-based video transmission over MIMO channels using precoder solutions. On the one hand, H.264/SVC codec ensures spatial, temporal and quality scalabilities and provides an intrinsic hierarchy over transmitted bitstreams. On the other hand, precoder designs, which decouple a MIMO channel into parallel and independent SISOsub-channels, offer a high BER performance with a hierarchy over the sub-channels. The proposed scheme exploits the scalability of the H.264/SVC codec jointly with four precoder solutions providing an UEP without any surplus redundancy. Besides, some of these precoders such as QoS and E-dmin allow a high flexibility on the power allocation across the sub-channels. This scalability is used to analytically draw the bandwidth allocation problem for H.264/SVC transmission over MIMO channels. The solution of this problem allows an optimal selection of each transmission bloc parameter approaching the optimal solution in term of Rate Distortion (RD) criterion. The simulation results show the performance of the proposed scheme over both statistical and realistic MIMO channels. Moreover, the accuracy of these precoder solutions against the Channel Estimation (CE) errors is investigated in different user mobility speeds.

Subjective assessment of the perceived quality of video calling services over a real LTE/4G network

The rapid growth of wireless mobile communications raises the critical issue of meeting user expectations and requirements. This paper deals with the subjective assessment of the perceived quality of video calling services delivered on a real LTE/4G network. The main goal is to determine the list of parameters that are predominantly impacting the Quality of Experience (QoE). The influencing parameters considered here include the video sequence content, coding technology and both core and radio access networks. Following the ITU-T Recommendations, subjective quality assessment experiments were conducted. Subjects were shown different representative sequences of video-calling services transmitted using different network conditions. The outcomes of these experiments show that the QoE is mainly affected by packets loss, jitter. However the impact of these parameters, which vary over time and in case of user mobility, seems to be different from that observed with simulated networks.

Soft decoding algorithms for optimized JPEG 2000 wireless transmission over realistic MIMO-OFDM systems

In this paper, we investigate a new cross layer PHYsical/APPlication (PHY-APP) communication strategy for scalable JPEG 2000 wireless image transmission over a realistic Multiple-Input Multiple-Output (MIMO) system. To exploit the channel diversity, we use a closed-loop MIMO-OFDM scheme. In the proposed scheme, the MIMO channel is decomposed into several hierarchical Single-Input Single-Output (SISO) subchannels by using a precoding approach. The scalable bitstream is divided into hierarchical quality layers which are passing through these SISO subchannels. In this paper, we propose a Joint Source-Channel (JSC) decoding approach based on soft-inputs decoding techniques to decrease the error rates at the reception without introducing extra redundancy. This scheme involves the serial concatenation of a soft-input soft-output Reed-Solomon (RS) decoder and a soft-input arithmetic decoder that were integrated into the JPEG 2000 wireless decoder. The objective of our approach is to guarantee the Quality of Service (QoS) required by the user for varying channel states. To this end, a link adaption strategy adjusting all the systems parameters of each SISO sub-channel (number of used subchannels, modulation order, Forward Error Correction (FEC) code capability, source coding rate) is also adopted in order to maximize the image visual quality at the reception. Thus, Unequal Error Protection (UEP), Unequal Power Allocation (UPA), adaptive modulation and source coding rate are provided for each quality layer. Simulation results of the optimized adaptive strategy illustrate good image quality improvements at the receiver side compared to a non adaptive strategy, with significant Peak Signal to Noise Ratio (PSNR) gains, especially for a realistic noisy channel provided by a 3D ray-tracing software. HighlightsNew transmission and coding strategies for JPEG 2000 wireless com-pressed images are proposed.A joint implementation of UEP, UPA, adaptive modulation and soft decoding techniques are also considered.Soft-inputs decoding techniques are used to decrease the error rates at the reception.A realistic time-varying MIMO channel provided by a 3D ray-tracing software is adopted.Results show a significant improvement in quality compared to non adaptive strategy.