variable-rate coding schemes is developed for communication over discrete memoryless channels wit... more 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. Index Terms—Error-correction coding, feedback channels, iterative coding. I.
This thesis develops a framework for low-complexity communication over channels with feedback. In... more This thesis develops a framework for low-complexity communication over channels with feedback. In this framework, which is named the compressed-error-cancellation framework, data are sent via a sequence of messages: the first message contains the original data; each subsequent message contains a source-coded description of the channel distortions introduced on the message preceding it. The framework is first used for coding over known single-user channels. For discrete memoryless channels with (complete) noiseless feedback (DMC$\sb{\rm f}$'s), a coding scheme exploiting low-complexity lossless source coding algorithms is developed, and the associated encoder and decoder are shown to use a number of computations growing only linearly with the number of channel inputs used (linear complexity). The associated error exponent is optimal in an appropriate sense and implies that capacity is achievable. For the class of channels with memory known as discrete finite-state channels with n...
In Chapters 2–5, we consider channels with feedback links that provide complete noiseless feedbac... more In Chapters 2–5, we consider channels with feedback links that provide complete noiseless feedback. But in practice, some feedback links may not be accurately modeled as being noiseless. Some may also have insufficient capacity to provide complete feedback. While some research, for example [1] and [9], has been done on coding for channels with noisy and partial feedback, it has been sparse, and many questions remain unanswered.
In this chapter, we develop the compressed-error-cancellation framework for coding for feedback c... more In this chapter, we develop the compressed-error-cancellation framework for coding for feedback channels, which supports the next four chapters. We convey the central ideas that constitute the framework via the following three progressively more complicated illustrations.
International Conference on Acoustics, Speech, and Signal Processing, 1994
A wavelet-transform-based CELP coder design is presented in this paper for high-quality speech co... more A wavelet-transform-based CELP coder design is presented in this paper for high-quality speech coding at about 4.8 kbits/s. The coder quantizes the second residual using a wavelet transform approach instead of the stochastic-codebook-based vector quantization normally used in CELP coders, including the U.S. Federal Standard FS 1016 coder at 4.8 kbits/s. The wavelet coder improves the computational efficiency for encoding
Proceedings of IEEE International Symposium on Information Theory, 1997
A class of practical, very low-complexity, variable-rate coding schemes is developed for communic... more A class of practical, very low-complexity, variable-rate coding schemes is developed for communication over channels with feedback. It is shown that for arbitrary discrete memoryless channels (DMCs) with noise-free feedback, these schemes achieve error probabilities that decay exponentially with block-length at any rate below the channel capacity. Extensions of the strategy for use on finite-state channels, known and unknown (universal
Correction-based template matching has been used extensively in computer vision for object recogn... more Correction-based template matching has been used extensively in computer vision for object recognition and also for other tasks such as edge detection, stereo, motion and inspection. It has also found wide application in character recognition. A deeper understanding of the performance of this technique for such tasks would help predict when it will succeed or fail. Previous work on this problem has examined correlation-based template matching using signal processing techniques. Our approach is different: we dissect it employing concepts from geometry and physics. This leads to new insights into correlation-based template matching. We study the performance of correlation between images for different lighting conditions, viewpoints and scales of a scene, obtaining new results for scale variation and viewpoint change for binary images. We analyze gray level images for changes in lighting alone and obtain useful and novel formulae. Knowing how correlation behaves with these changes helps to strategically distribute templates for a given recognition task. We then develop a method to compute the probability of confusion for recognition by template matching. We obtain a closed form solution for the probability of confusion in the two template case. We conclude by noting that template matching encounters difficulties in tasks such as object recognition because of its strong dependence on viewing conditions, although it can be useful in some situations when templates are chosen and positioned judiciously.
The compressed-error-cancellation framework of Ooi and Wornell is extended for multiple-access ch... more The compressed-error-cancellation framework of Ooi and Wornell is extended for multiple-access channels with feedback and single-user channels with partial feedback.
While DMC’s provide accurate models for some channels used in practice, they are not accurate mod... more While DMC’s provide accurate models for some channels used in practice, they are not accurate models of channels with memory. A channel has memory if the output of the channel at a particular time k depends statistically on the input or output of the channel at a time other than k.
In the preceding three chapters, we develop and apply the compressed-error-cancellation framework... more In the preceding three chapters, we develop and apply the compressed-error-cancellation framework to the single-user case, i.e., the situation in which a single transmitter must send data to a single receiver. But often in practice, multiple transmitters must simultaneously send data to multiple receivers. If the transmitters share the same channel in some sense, then the complications introduced by the mutual interference invalidate the single-transmitter, single-receiver model.
A class of capacity-achieving, low-complexity, highreliability, variable-rate coding schemes is d... more A class of capacity-achieving, low-complexity, highreliability, 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.
The problem of estimating parameters of discrete-time non-Gaussian autoregressive (AR) processes ... more The problem of estimating parameters of discrete-time non-Gaussian autoregressive (AR) processes is addressed. The subclass of such processes considered is restricted to those whose driving noise samples are statistically independent and ...
Wavelets are a new family of orthogonal basis functions for representing finite energy signals. I... more Wavelets are a new family of orthogonal basis functions for representing finite energy signals. In this chapter, we provide a brief review of wavelets and their properties. We cite a number of applications of wavelets to speech processing that have been proposed recently. As a detailed case study in wavelet applications, we present our work on a wavelet-transform-based CELP coder
variable-rate coding schemes is developed for communication over discrete memoryless channels wit... more 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. Index Terms—Error-correction coding, feedback channels, iterative coding. I.
This thesis develops a framework for low-complexity communication over channels with feedback. In... more This thesis develops a framework for low-complexity communication over channels with feedback. In this framework, which is named the compressed-error-cancellation framework, data are sent via a sequence of messages: the first message contains the original data; each subsequent message contains a source-coded description of the channel distortions introduced on the message preceding it. The framework is first used for coding over known single-user channels. For discrete memoryless channels with (complete) noiseless feedback (DMC$\sb{\rm f}$'s), a coding scheme exploiting low-complexity lossless source coding algorithms is developed, and the associated encoder and decoder are shown to use a number of computations growing only linearly with the number of channel inputs used (linear complexity). The associated error exponent is optimal in an appropriate sense and implies that capacity is achievable. For the class of channels with memory known as discrete finite-state channels with n...
In Chapters 2–5, we consider channels with feedback links that provide complete noiseless feedbac... more In Chapters 2–5, we consider channels with feedback links that provide complete noiseless feedback. But in practice, some feedback links may not be accurately modeled as being noiseless. Some may also have insufficient capacity to provide complete feedback. While some research, for example [1] and [9], has been done on coding for channels with noisy and partial feedback, it has been sparse, and many questions remain unanswered.
In this chapter, we develop the compressed-error-cancellation framework for coding for feedback c... more In this chapter, we develop the compressed-error-cancellation framework for coding for feedback channels, which supports the next four chapters. We convey the central ideas that constitute the framework via the following three progressively more complicated illustrations.
International Conference on Acoustics, Speech, and Signal Processing, 1994
A wavelet-transform-based CELP coder design is presented in this paper for high-quality speech co... more A wavelet-transform-based CELP coder design is presented in this paper for high-quality speech coding at about 4.8 kbits/s. The coder quantizes the second residual using a wavelet transform approach instead of the stochastic-codebook-based vector quantization normally used in CELP coders, including the U.S. Federal Standard FS 1016 coder at 4.8 kbits/s. The wavelet coder improves the computational efficiency for encoding
Proceedings of IEEE International Symposium on Information Theory, 1997
A class of practical, very low-complexity, variable-rate coding schemes is developed for communic... more A class of practical, very low-complexity, variable-rate coding schemes is developed for communication over channels with feedback. It is shown that for arbitrary discrete memoryless channels (DMCs) with noise-free feedback, these schemes achieve error probabilities that decay exponentially with block-length at any rate below the channel capacity. Extensions of the strategy for use on finite-state channels, known and unknown (universal
Correction-based template matching has been used extensively in computer vision for object recogn... more Correction-based template matching has been used extensively in computer vision for object recognition and also for other tasks such as edge detection, stereo, motion and inspection. It has also found wide application in character recognition. A deeper understanding of the performance of this technique for such tasks would help predict when it will succeed or fail. Previous work on this problem has examined correlation-based template matching using signal processing techniques. Our approach is different: we dissect it employing concepts from geometry and physics. This leads to new insights into correlation-based template matching. We study the performance of correlation between images for different lighting conditions, viewpoints and scales of a scene, obtaining new results for scale variation and viewpoint change for binary images. We analyze gray level images for changes in lighting alone and obtain useful and novel formulae. Knowing how correlation behaves with these changes helps to strategically distribute templates for a given recognition task. We then develop a method to compute the probability of confusion for recognition by template matching. We obtain a closed form solution for the probability of confusion in the two template case. We conclude by noting that template matching encounters difficulties in tasks such as object recognition because of its strong dependence on viewing conditions, although it can be useful in some situations when templates are chosen and positioned judiciously.
The compressed-error-cancellation framework of Ooi and Wornell is extended for multiple-access ch... more The compressed-error-cancellation framework of Ooi and Wornell is extended for multiple-access channels with feedback and single-user channels with partial feedback.
While DMC’s provide accurate models for some channels used in practice, they are not accurate mod... more While DMC’s provide accurate models for some channels used in practice, they are not accurate models of channels with memory. A channel has memory if the output of the channel at a particular time k depends statistically on the input or output of the channel at a time other than k.
In the preceding three chapters, we develop and apply the compressed-error-cancellation framework... more In the preceding three chapters, we develop and apply the compressed-error-cancellation framework to the single-user case, i.e., the situation in which a single transmitter must send data to a single receiver. But often in practice, multiple transmitters must simultaneously send data to multiple receivers. If the transmitters share the same channel in some sense, then the complications introduced by the mutual interference invalidate the single-transmitter, single-receiver model.
A class of capacity-achieving, low-complexity, highreliability, variable-rate coding schemes is d... more A class of capacity-achieving, low-complexity, highreliability, 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.
The problem of estimating parameters of discrete-time non-Gaussian autoregressive (AR) processes ... more The problem of estimating parameters of discrete-time non-Gaussian autoregressive (AR) processes is addressed. The subclass of such processes considered is restricted to those whose driving noise samples are statistically independent and ...
Wavelets are a new family of orthogonal basis functions for representing finite energy signals. I... more Wavelets are a new family of orthogonal basis functions for representing finite energy signals. In this chapter, we provide a brief review of wavelets and their properties. We cite a number of applications of wavelets to speech processing that have been proposed recently. As a detailed case study in wavelet applications, we present our work on a wavelet-transform-based CELP coder
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Papers by James Ooi