Video communication over wireless links using handheld devices is a challenging task due to the time-varying characteristics of the wireless channels and limited battery resources. Rate-distortion (R-D) analysis plays...
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Video communication over wireless links using handheld devices is a challenging task due to the time-varying characteristics of the wireless channels and limited battery resources. Rate-distortion (R-D) analysis plays a key role in video coding and communication systems, and usually R-D relation does not assume any power constraint. In this paper, we investigate the relations of rate, distortion, and power consumption. Based on those relations, we propose a power-minimized bit-allocation scheme considering the processing power for sourcecoding and channelcoding, as well as the transmission power jointly. In this scheme, the total bits are allocated between source and channel coders, according to wireless channel conditions and video quality requirements, to minimize the total power consumption for a single user and a group of users in a cell, respectively. Simulation results show that our proposed joint power-control and bit-allocation scheme achieves high power savings compared to the conventional scheme.
With the emerging of the third generation (3G) wireless technology, digital media, like image and video, over wireless channel becomes more and more demanding. In this paper, the measure metrics for the wireless image...
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ISBN:
(纸本)0819444111
With the emerging of the third generation (3G) wireless technology, digital media, like image and video, over wireless channel becomes more and more demanding. In this paper, the measure metrics for the wireless image is proposed and a Qos-guarantee error control is presented, combining UEP with Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ), aiming to high quality image transmission with short delay and little energy. Simulation results show that our scheme can achieve good reconstructed image with few retransmission times and small bit budget under different channel conditions, which can reduce the energy consumed in the network interface.
Multicarrier modulation (MCM) with diversity is a promising technique for multimedia communications over fading multipath wireless channels. In this work, we first investigate the channel estimation problem for the MC...
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ISBN:
(纸本)0819441880
Multicarrier modulation (MCM) with diversity is a promising technique for multimedia communications over fading multipath wireless channels. In this work, we first investigate the channel estimation problem for the MCM system with multiple transmitter antennas. A model based channel estimation approach is proposed to identify the multiple channels simultaneously. We then apply the model based channel estimation in a jointsource and channel matching (JSCM) scheme for the robust progressive image transmission. It is shown that the channel estimation affects not only the image decoding at the receiver but also the rate allocation at the transmitter. It is important to jointly consider the channel estimation and JSCM scheme to improve the quality of image transmission.
In this letter we show how parallel concatenated codes (PCC's, also known as "turbo codes") can be endowed with unequal error protection (UEP). Given the two component encoders of the PCC encoder and the...
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In this letter we show how parallel concatenated codes (PCC's, also known as "turbo codes") can be endowed with unequal error protection (UEP). Given the two component encoders of the PCC encoder and the desired interleaver size, UEP is achieved by: 1) suitably positioning the different importance classes of information symbols into the encoder input frame) 2) puncturing the PCC redundancy symbols with a nonuniform pattern;and 3) choosing the interleaver of the PCC encoder in a class of interleavers that guarantees isolation of the importance classes. By controlling the amount of redundancy assigned to each importance class and the class positioning in the input frame, a whole family of UEP PCC's with different UEP levels can be obtained from the same component encoders and interleaver size. From a practical viewpoint, a family of UEP PCC's can he decoded by the same "turbo" iterative decoder, provided that the decoder hardware implementation allows for programmable puncturing and interleaving.
作者：
Chen, BWornell, GWMIT
Dept Elect Engn & Comp Sci Cambridge MA 02139 USA MIT
Elect Res Lab Cambridge MA 02139 USA
The properties of chaotic dynamical systems make them useful for channelcoding in a variety of practical communication applications. To illustrate this, a novel analog code based on tent map dynamics and having a fas...
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The properties of chaotic dynamical systems make them useful for channelcoding in a variety of practical communication applications. To illustrate this, a novel analog code based on tent map dynamics and having a fast decoding algorithm is developed for use on unknown, multiple, and time-varying signal-to-noise ratio (SNR) channels. This code is shown to be an attractive alternative to both digital codes and linear modulation in such scenarios, Several properties and interpretations of the codes are developed, along with some methods for their optimization.
For digital broadcasting of TV-signals over various transmission media like satellite, cable, and terrestrial channels, the MPEG-2 video sourcecoding algorithm will be considered. Since the video-signal is very sensi...
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ISBN:
(纸本)0819427497
For digital broadcasting of TV-signals over various transmission media like satellite, cable, and terrestrial channels, the MPEG-2 video sourcecoding algorithm will be considered. Since the video-signal is very sensitive to channel disturbances due to variable length coding (VLC), a bit-error rate of;less than 10(-8) has to be guaranteed. Therefore, a powerful error protection scheme is applied in the European TV-Broadcasting Standards(1-3). However, in the case of bad reception conditions, e.g. deep fades or impulsive noise, remaining errors even in the highest protected video signal may still occur. With remaining errors in the video signal a good quality of service cannot be guaranteed. Therefore, some post-processing techniques such as error concealment and iterative decoding at the receiver side will be desirable(4). The aim of this article is to study different error concealment techniques for handling residual channel errors at the receiver side taking into account a real transmission media. For I-pictures, a motion compensated temporal error concealment algorithm is proposed where motion vectors are displaced along the motion direction.
An innovative method of coding Line Spectrum Pair (LSP) parameters for transmission over noisy channels is presented. Typically, low bit-rate speech coders use these parameters to convey perceptually important spectra...
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An innovative method of coding Line Spectrum Pair (LSP) parameters for transmission over noisy channels is presented. Typically, low bit-rate speech coders use these parameters to convey perceptually important spectral information. Thus it is necessary that these parameters are not only efficiently quantized but preserved during transmission. The scheme uses a joint source and channel coding technique applied to a concatenated trellis structure. Operating as a source coder, the system encodes below the 1 dB spectral distortion limit. It is shown that by modifying the encoder cost function to include the expected channel distortion, the code exhibits improved robustness to channel errors. This is accomplished with minimal increase in complexity and without increase in bit-rate. It is noted that the scheme performs well over a wide range of channel bit error rates and compares favourably with a standard scalar LSP quantizer tandemed with a channel coder both in terms of bit-rate and channel noise immunity,
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