In this letter, we present the extension of the trellis space-time code (STC) concept to include signal mapping drawn from an N-dimensional sphere. The signal points were designed as such to Increase the minimum squar...
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In this letter, we present the extension of the trellis space-time code (STC) concept to include signal mapping drawn from an N-dimensional sphere. The signal points were designed as such to Increase the minimum squared distance between points in the constellation without increasing the average transmit energy. The mapping of the N-dimensional spherical constellations was performed in accordance to set partitioning rules for STC developed by AT&T but optimized for these codes. Performance evaluation For these spherical space-time codes (SSTC) are illustrated in an OFDM framework, which is a natural choice for multidimensional signaling.
Optimal hierarchical coding is sought, for progressive or scalable multidimensional signal transmission, by minimizing the variance of the error difference between the original image and its lower resolution rendition...
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Optimal hierarchical coding is sought, for progressive or scalable multidimensional signal transmission, by minimizing the variance of the error difference between the original image and its lower resolution renditions. The optimal, according to the above criterion, pyramidal coders are determined for images quantized using the optimal vector Lloyd-Max quantizers. A rigorous general statistical model of a vector Lloyd-Max quantizer is used, consisting of a linear time-invariant filter followed by additive noise uncorrelated with the input. Given arbitrary analysis filters, the optimal synthesis filters are found, The optimal analysis filters are subsequently determined, leading to formulas for globally optimal structures for pyramidal multidimensional signal decompositions, These structures produce replicas of the original image, which at lower resolutions retain as much similarity to the original as possible, This fs highly useful for the progressive coding of two-or three-dimensional (2-D or 3-D) images needed in applications such as fast browsing, through image databases, Furthermore, the minimization, of the variance of the error image leads to minimization of the variance or the quantization noise for this image and, hence, to its optimally efficient compression, Experimental results illustrate the implementation and performance of the optimal pyramids in application for the coding of still 2-D images.
In the content-based image coding scheme, segmentation information of the arbitrarily shaped regions may be available for both encoder and decoder. The shape-assisted block-based texture coding methodologies, such as ...
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In the content-based image coding scheme, segmentation information of the arbitrarily shaped regions may be available for both encoder and decoder. The shape-assisted block-based texture coding methodologies, such as shape-adaptive discrete cosine transform (SADCT), can use this segmentation information to improve coding efficiency. In this paper, we introduce the shape-adaptive region partitioning (SARP) methods which can reduce the number of coding blocks that partition the arbitrarily shaped region by modifying the black positions. By simply adding SARP method to aid the SADCT, the coded texture bits can be reduced by 5-10%, in comparison with the SADCT using common block-based coding infrastructure which is usually used in the MPEG-1/2 and H.263.
The sudden deterioration in transmission quality due to rain or snow attenuations is a problem in VSAT communications using the 14/12-GHz band-link, and a system that can cope with such a problem has been developed an...
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The sudden deterioration in transmission quality due to rain or snow attenuations is a problem in VSAT communications using the 14/12-GHz band-link, and a system that can cope with such a problem has been developed and studied. This paper proposes a method for improving: the bit error rate (BER) of an overall system for satellite channels showing a decreased carrier-to-noise (CNR) by using a terrestrial channel of low error rates in addition to satellite channels and by coding both channels simultaneously. The effectiveness of the proposed scheme has been clarified by deriving the theoretical upper bounds of the BER and evaluating its performance by computer simulations for the case of multidimensional coding based on QPSK signals.
We consider the general problem of the uniform error property (UEP) for multidimensional coded modulation, transmitted over the AWGN or flat fading channel and received by a generalized decoder. The symbols are restri...
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We consider the general problem of the uniform error property (UEP) for multidimensional coded modulation, transmitted over the AWGN or flat fading channel and received by a generalized decoder. The symbols are restricted to have constant energy. The generalized decoder is a very broad range model for the decoders and receivers which are used in current and proposed communication systems. It operates by maximizing an arbitrary likelihood function the arguments of which are the front-end correlator outputs. The coherent decoder for the AWGN is only a special case. A group code structure which guarantees the UEP is obtained by extending the theory of geometrically uniform codes to the generalized decoder. A discussion on the particular case of noncoherent decoding is presented. It is found that the correlation-based decoder error probability is a function of a pseudo-distance.
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