Atousa Hajshirmohammadi

Unequal Error Protection of JPEG2000 Images Using Short Block Length Turbo Codes

Examining the Bit Error Rate (BER) at various positions of a Turbo Coded data block reveals that Turbo Codes inherently possess Unequal Error Protection (UEP) properties. In this paper, we mainly investigate the impact of different puncturing patterns on the resulting UEP properties. And then we apply these properties to the JPEG2000 image transmission. The results indicate that a proper design of the system can bring substantial gain in decoded image quality.

Unequal Power Allocation for Transmission of JPEG2000 Images over Wireless Channels

In this paper, we present an unequal power allocation method that exploits the hierarchical structure of JPEG2000 coded bitstream, along with the channel state information, to assign different transmission powers to different parts of the bitstream at the coding pass level. Based on the information from the JPEG2000 bitstream, we first develop a distortion model to evaluate the distortion of the reconstructed image in terms of the power assigned to each coding pass within the bitstream. Using this model and the channel information, the powers are calculated such that the distortion of the decoded image is minimized. Simulation results show up to 7 dB improvement in the decoded image quality compared to the case of equal power allocation and up to 4 dB enhancement compared to the state-of-the-art methods proposed for the transmission of JPEG2000 streams over wireless channels.

Transmission of JPEG2000 images over frequency selective channels with unequal power allocation

In this study, transmission of JPEG2000 images using an unequal power allocation (UPA) scheme and orthogonal frequency division multiplexing (OFDM) over block-fading frequency-selective channels is presented. A distortion model is provided to evaluate the contribution of each coding pass (CP) in the construction of the received image. The optimisation algorithm exploits the hierarchical structure of the JPEG2000 images and uses the distortion model along with the channel state information for allocating optimal values of power for each CP to minimise the end-to-end distortion. Furthermore, the actual total power consumed for transmission is measured and compared with the total power initially assigned. For the purpose of simulations, the authors set the number of OFDM subcarriers to be 16, the length of the cyclic prefixes equal to the channel memory length and analyse the quality of the received image in a 2-tap and 3-tap frequency-selective channel, with and without our proposed UPA technique in an OFDM system. The results show an improvement of up to 10.5 dB in the decoded image quality when the UPA scheme is used. In addition, our system manages to maintain similar quality for the received image in a multi-tap channel scenario.

JPEG2000 image transmission over OFDM-based Cognitive Radio network

Cognitive Radio (CR) is an efficient way of spectrum utilization in the way that secondary users (SU) with high bandwidth (BW) requirements such as multimedia users, can get access to the licensed frequency resources opportunistically and resolve their BW limitation. Among all the multimedia formats, JPEG2000 has many features that makes it suitable for cognitive radio networks. In this paper a channel allocation method based on JPEG2000 and orthogonal frequency division multiplexing (OFDM) is proposed, which improves the quality of the SUs received image by providing dynamic access to the available spectrum, without violating the interference requirement to the PU. Channels with better condition are used to transmit important data in JPEG2000 coded bit-stream. Therefore, reception of determinative bits is guaranteed.

Joint Decoding of Unequally Protected JPEG2000 Bitstreams and Reed-Solomon Codes

In this paper we present joint decoding of JPEG2000 bitstreams and Reed-Solomon codes in the context of unequal loss protection. Using error resilience features of JPEG2000 bitstreams, the joint decoder helps to restore the erased symbols when the Reed-Solomon decoder fails to retrieve them on its own. However, the joint decoding process might become time-consuming due to a search through the set of possible erased symbols. We propose the use of smaller codeblocks and transmission of a relatively small amount of side information with high reliability as two approaches to accelerate the joint decoding process. The accelerated joint decoder can deliver essentially the same quality enhancement as the nonaccelerated one, while operating several times faster.

Joint source-chanel decoding of JPEG2000 images with unequal loss protection

This paper presents a method for joint decoding of JPEG2000 bitstreams and Reed-Solomon codes in the context of unequal loss protection. When the Reed-Solomon decoder is unable to retrieve the erased source symbols, the proposed joint decoder searches through the set of possible erased source symbols, making use of error resilience features of JPEG2000 to retrieve correct symbols. The joint decoder can be used as an add-on module to some of the existing schemes for unequal loss protection, and can improve the PSNR of decoded images by over 10 dB in some cases.

Power and sub-channel optimization of JPEG 2000 image transmission over OFDM-based cognitive radio networks

Abstract Cognitive Radio is an efficient way of spectrum utilization since secondary users with bandwidth-demanding applications such as multimedia can get access to licensed frequency resources opportunistically and resolve their bandwidth limitations. Among all multimedia formats, JPEG 2000 is a suitable candidate for cognitive radio networks thanks to its unique features. In conventional resource allocations for Cognitive Radio systems, all data bits are assumed equally important. However, different parts of the JPEG 2000 bit stream have different contributions to the quality of the received image. Therefore, in this paper, an unequal power allocation method is used to allocate the available power to the coded bits based on their importance in the image quality. Simulated annealing method is used to solve the unequal power allocation problem. Furthermore, bits with higher significance are further protected by using sub-channels with better channel quality. Thus, the likelihood of significant bits being received correctly is increased. The optimal solution is obtained by minimizing the image distortion without violating the interference constraint to the primary users. The performance of the proposed method is demonstrated by simulation results.

Improved Joint Source-Channel Decoding of JPEG2000 Images and Reed-Solomon Codes

In this paper we present improvements to the recently-proposed joint decoding of JPEG2000 bitstreams and Reed-Solomon codes in the context of unequal loss protection. Using error resilience features of JPEG2000 bitstreams, the joint decoder helps to restore the erased symbols when the Reed-Solomon decoder fails to retrieve them on its own. We make use of the ability of the JPEG2000 decoder to provide rough error localization within a coding pass to speed up the search for erased symbol values. In addition, we show how transmitting a relatively small amount of side information with high reliability may help the joint decoder by reducing the size of the search space and bypassing some of the JPEG2000 decoding iterations needed to verify the correctness of the restored source information. The improved joint decoder is up to 20 times faster compared to the previous one.

Multicasting JPEG2000 images over MIMO systems

Increasing demand for high-speed and efficient multimedia transmission over wireless networks has driven tremendous research on enhancing the performance of multimedia communications over noisy channels. Multimedia applications increasingly require efficient transmission of still and moving images over wireless channels. In response to the rapidly increasing demand of the data-rate requirements, of particular importance is the so-called multi-input multi-output (MIMO) antenna. In this paper, we simultaneously exploit spatial multiplexing, diversity, antenna selection, and unequal power allocation (UPA) techniques to transmit progressive JPEG2000 images over a MIMO downlink channel where communication occurs from a multi-antenna base station to multiple multi-antenna mobile terminals. We take advantage of the spatial diversity by utilizing a joint decoding in the JPEG2000 decoder. The aim is to reduce the average distortion among users. Simulation results show that our proposed algorithms provide significant image quality improvement when compared to schemes that do not consider antenna selection or UPA.

Using an adaptive UPA scheme with a channel-aware OFDM technique for wireless transmission of JPEG2000 images

In this paper, an adaptive scheme is developed for an Unequal Power Allocation (UPA) algorithm in a way to allow variable size grouping of the coding passes to enhance the optimization process at different Signal to Noise Ratio (SNR) values. The optimization algorithm exploits the hierarchical structure of the JPEG2000 images and uses a distortion model along with the channel state information (CSI) for allocating optimal values of power on each coding pass to minimize the end-to-end distortion. Orthogonal Frequency Division Multiplexing (OFDM) technique is incorporated within the transmitter to enable transmission of the JPEG2000 images over block fading frequency selective channels. In this paper, we propose a channel assignment strategy, within our OFDM transmitter, which passes the more important coding passes over the subcarriers with higher channel gain. Simulation results indicate an improvement of up to 2 dB in the decoded image quality and potentiality of energy conservation when the adaptive UPA scheme along with the channel assignment strategy are used.