This paper proposes a class of space time parallel (STP) iterative coding scheme to combat fading for wireless MIMO systems. In addition to the inner iterations, the super iterations (or outer iterations) and symbol i...
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This paper proposes a class of space time parallel (STP) iterative coding scheme to combat fading for wireless MIMO systems. In addition to the inner iterations, the super iterations (or outer iterations) and symbol interleaved space time coding are employed to achieve additional time diversity and coding gain in fading channel. The numerical and simulation results demonstrate that the STP iterative coding scheme may make use of all the advantages of transmit diversity and time diversity in wireless MIMO systems. In particular, in the case of STP turbo codes, about I dB BER enhancement and half calculation time reduction from conventional space time (ST) turbo codes designs are achieved;in the case of low density parity check (LDPC) codes, about 0.8 dB improvement from conventional ST LDPC designs is obtained. Copyright (C) 2003 John Wiley Sons, Ltd.
To embed the multiple watermarks is a way to increase robustness in image watermark. The limitation of embedding multiple watermarks is that the limited capacity of an image severely limits the size of the watermark. ...
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To embed the multiple watermarks is a way to increase robustness in image watermark. The limitation of embedding multiple watermarks is that the limited capacity of an image severely limits the size of the watermark. Multiple-description coding is a good candidate to solve this limitation by trading off between transmission bandwidth and bit error rate. Traditionally, multiple-description coding is considered in on-off channels where channels are not marred by bit errors but occasional connection outages such as dropped packets. To apply multiple-description coding in image watermarking, we need a form of multiple-description coding for noisy channels instead of on-off channels. In this paper, we propose to add iterative coding in multiple description in order to combat bit errors in image watermarking. We call this method multiple-description iterative coding (MDIC) image watermarking. We tested our system on six images. On average, bit error did not happen until we compressed the image in JPEG to PSNR 36.97 dB. We concluded that MDIC was a very good way to increase robustness for image watermarking. (C) 2009 Elsevier Inc. All rights reserved.
作者：
Ooi, JMWornell, GWMIT
Dept Elect Engn & Comp Sci Cambridge MA 02139 USA MIT
Elect Res Lab Cambridge MA 02139 USA
A class of capacity-achieving, low-complexity, high-reliability, variable-rate coding schemes is developed for communication over discrete memoryless channels with noiseless feedback, Algorithms for encoding and decod...
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A class of capacity-achieving, low-complexity, high-reliability, variable-rate coding schemes is developed for communication over discrete memoryless channels with noiseless feedback, Algorithms for encoding and decoding that require computations growing linearly with the number of channel inputs used are developed. The error exponent associated with the scheme is shown to be optimal and implies that capacity is achievable. Simulations are performed and support the analytically predicted high performance and low complexity.
This paper presents a new fractal coding scheme to find a suboptimal transformation by performing an iterative encoding process. The optimal transformation can be defined as the transformation generating the closest a...
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This paper presents a new fractal coding scheme to find a suboptimal transformation by performing an iterative encoding process. The optimal transformation can be defined as the transformation generating the closest attractor to an original image. Unfortunately, it is impossible in practice to find the optimal transformation, due to the heavy computational burden. In this paper, however, by means of some new theorems related with contractive transformations and attractors, it is shown that for some specific cases the optimal or suboptimal transformations can be obtained. The proposed method obtains a suboptimal transformation by performing iterative processes as is done in decoding. Thus, it requires more computation than the conventional method, but it improves the image quality. For a simple case where the optimal transformation can actually be found, the proposed method is experimentally evaluated against both the optimal method and the conventional method. For a general case where the optimal transformation is unavailable due to heavy computational complexity, the proposed method is also evaluated in comparison with the conventional method. (C) 2001 Society of Photo-Optical Instrumentation Engineers.
This paper presents a simple and very flexible method for constructing quasi-cyclic (QC) low density parity-check (LDPC) codes based on finite fields. The code construction is based on two arbitrary subsets of element...
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This paper presents a simple and very flexible method for constructing quasi-cyclic (QC) low density parity-check (LDPC) codes based on finite fields. The code construction is based on two arbitrary subsets of elements from a given field. Some well known constructions of QC-LDPC codes based on finite fields and combinatorial designs are special cases of the proposed construction. The proposed construction in conjunction with a technique, known as masking, results in codes whose Tanner graphs have girth 8 or larger. Experimental results show that codes constructed using the proposed construction perform well and have low error-floors. Also presented in the paper is a reduced-complexity iterative decoding scheme for QC-LDPC codes based on the section-wise cyclic structure of their parity-check matrices. The proposed decoding scheme is an improvement of an earlier proposed reduced-complexity iterative decoding scheme.
For radio communication systems powerful error correction codes are necessary to operate in noisy and fading channel conditions. iterative forward error correction schemes like Turbo codes can achieve near Shannon cap...
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ISBN:
(纸本)9780819481702
For radio communication systems powerful error correction codes are necessary to operate in noisy and fading channel conditions. iterative forward error correction schemes like Turbo codes can achieve near Shannon capacity performance on memory-less channels and also perform well on correlated fading channels. The key to the excellent decoding performance of the Turbo coding systems is the BCJR algorithm in conjunction with the iterative processing of the soft decision information. A very popular modulation technique is Differential Phase Shift Key (DPSK) which is not only a simple non-coherent modulation and demodulation technique, it is also a recursive rate one code. Combining DPSK with a single convolutional code structure as an iterative inner outer forward error correction system can provide excellent Turbo like performance. Monte Carlo simulation results will be shown for the Additive White Gaussian Noise (AWGN) and Rayleigh fading channels for 1,2, 3 and 4 bits per symbol DPSK.
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