213 research outputs found
Joint source channel coding for progressive image transmission
Recent wavelet-based image compression algorithms achieve best ever performances with fully embedded bit streams. However, those embedded bit streams are very sensitive to channel noise and protections from channel coding are necessary. Typical error correcting capability of channel codes varies according to different channel conditions. Thus, separate design leads to performance degradation relative to what could be achieved through joint design. In joint source-channel coding schemes, the choice of source coding parameters may vary over time and channel conditions. In this research, we proposed a general approach for the evaluation of such joint source-channel coding scheme. Instead of using the average peak signal to noise ratio (PSNR) or distortion as the performance metric, we represent the system performance by its average error-free source coding rate, which is further shown to be an equivalent metric in the optimization problems.
The transmissions of embedded image bit streams over memory channels and binary symmetric channels (BSCs) are investigated in this dissertation. Mathematical models were obtained in closed-form by error sequence analysis (ESA). Not surprisingly, models for BSCs are just special cases for those of memory channels. It is also discovered that existing techniques for performance evaluation on memory channels are special cases of this new approach. We further extend the idea to the unequal error protection (UEP) of embedded images sources in BSCs. The optimization problems are completely defined and solved. Compared to the equal error protection (EEP) schemes, about 0.3 dB performance gain is achieved by UEP for typical BSCs. For some memory channel conditions, the performance improvements can be up to 3 dB. Transmission of embedded image bit streams in channels with feedback are also investigated based on the model for memory channels. Compared to the best possible performance achieved on feed forward transmission, feedback leads to about 1.7 dB performance improvement
Progressive Source-Channel Coding for Multimedia Transmission over Noisy and Lossy Channels with and without Feedback
Rate-scalable or layered lossy source-coding is useful for
progressive transmission of multimedia sources, where the receiver can
reconstruct the source incrementally.
This thesis considers ``joint source-channel'' schemes
for such a progressive transmission, in the presence of
noise or loss, with and without the use of a feedback link.
First we design image communication schemes for memoryless and finite
state channels using limited and explicitly constrained use of
the feedback channel in the form of a variable incremental redundancy
Hybrid ARQ protocol. Constraining feedback allows a direct
comparison with schemes without feedback. Optimized feedback based
systems are shown to have useful gains.
Second, we develop a controlled Markov chain approach for constrained feedback Hybrid ARQ protocol design.
The proposed methodology allows the protocol to be chosen from a collection of signal flow graphs, and
also allows explicit control over the tradeoffs in throughput, reliability and complexity.
Next we consider progressive image transmission in
the absence of feedback. We assign unequal error protection to the bits of
a rate-scalable source-coder using rate compatible
channel codes. We show that, under the framework, the source and
channel bits can be ``scheduled'' in a single bitstream in such a way
that operational optimality is retained for different transmission
budgets, creating a rate-scalable joint source-channel coder.
Next we undertake the design of a joint source-channel decoder that
uses ``distortion aware'' ACK/NACK feedback generation. For
memoryless channels, and Type-I HARQ, the design of optimal ACK/NACK
generation and decoding by packet combining is cast and solved as a
sequential decision problem. We obtain dynamic programming based
optimal solutions and also propose suboptimal, lower complexity
distortion-aware decoders and feedback generation rules which
outperform conventional BER based rules such as
CRC-check.
Finally we design operational rate-distortion optimal ACK/NACK
feedback generation rules for transmitting a tree structured quantizer
over a memoryless channel. We show that the optimal feedback
generation rules are embedded, that is, they allow incremental
switching to higher rates during the transmission. Also, we
obtain the structure of the feedback generation rules in terms
of a feedback threshold function that simplifies the implementation
Progressive transmission of medical images
A novel adaptive source-channel coding scheme for progressive transmission of medical images with a feedback system is therefore proposed in this dissertation. The overall design includes Discrete Wavelet Transform (DWT), Embedded Zerotree Wavelet (EZW) coding, Joint Source-Channel Coding (JSCC), prioritization of region of interest (RoI), variability of parity length based on feedback, and the corresponding hardware design utilising Simulink. The JSCC can achieve an efficient transmission by incorporating unequal error projection (UEP) and rate allocation. An algorithm is also developed to estimate the number of erroneous data in the receiver. The algorithm detects the address in which the number of symbols for each subblock is indicated, and reassigns an estimated correct data according to a decision making criterion, if error data is detected. The proposed system has been designed based on Simulink which can be used to generate netlist for portable devices. A new compression method called Compressive Sensing (CS) is also revisited in this work. CS exhibits many advantages in comparison with EZW based on our experimental results. DICOM JPEG2000 is an efficient coding standard for lossy or lossless multi-component image coding. However, it does not provide any mechanism for automatic RoI definition, and is more complex compared to our proposed scheme. The proposed system significantly reduces the transmission time, lowers computation cost, and maintains an error-free state in the RoI with regards to the above provided features. A MATLAB-based TCP/IP connection is established to demonstrate the efficacy of the proposed interactive and adaptive progressive transmission system. The proposed system is simulated for both binary and symmetric channel (BSC) and Rayleigh channel. The experimental results confirm the effectiveness of the design.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Progressive transmission of medical images
A novel adaptive source-channel coding scheme for progressive transmission of medical images with a feedback system is therefore proposed in this dissertation. The overall design includes Discrete Wavelet Transform (DWT), Embedded Zerotree Wavelet (EZW) coding, Joint Source-Channel Coding (JSCC), prioritization of region of interest (RoI), variability of parity length based on feedback, and the corresponding hardware design utilising Simulink. The JSCC can achieve an efficient transmission by incorporating unequal error projection (UEP) and rate allocation. An algorithm is also developed to estimate the number of erroneous data in the receiver. The algorithm detects the address in which the number of symbols for each subblock is indicated, and reassigns an estimated correct data according to a decision making criterion, if error data is detected. The proposed system has been designed based on Simulink which can be used to generate netlist for portable devices. A new compression method called Compressive Sensing (CS) is also revisited in this work. CS exhibits many advantages in comparison with EZW based on our experimental results. DICOM JPEG2000 is an efficient coding standard for lossy or lossless multi-component image coding. However, it does not provide any mechanism for automatic RoI definition, and is more complex compared to our proposed scheme. The proposed system significantly reduces the transmission time, lowers computation cost, and maintains an error-free state in the RoI with regards to the above provided features. A MATLAB-based TCP/IP connection is established to demonstrate the efficacy of the proposed interactive and adaptive progressive transmission system. The proposed system is simulated for both binary and symmetric channel (BSC) and Rayleigh channel. The experimental results confirm the effectiveness of the desig
Distributed Deep Joint Source-Channel Coding over a Multiple Access Channel
We consider distributed image transmission over a noisy multiple access
channel (MAC) using deep joint source-channel coding (DeepJSCC). It is known
that Shannon's separation theorem holds when transmitting independent sources
over a MAC in the asymptotic infinite block length regime. However, we are
interested in the practical finite block length regime, in which case separate
source and channel coding is known to be suboptimal. We introduce a novel joint
image compression and transmission scheme, where the devices send their
compressed image representations in a non-orthogonal manner. While
non-orthogonal multiple access (NOMA) is known to achieve the capacity region,
to the best of our knowledge, non-orthogonal joint source channel coding (JSCC)
scheme for practical systems has not been studied before. Through extensive
experiments, we show significant improvements in terms of the quality of the
reconstructed images compared to orthogonal transmission employing current
DeepJSCC approaches particularly for low bandwidth ratios. We publicly share
source code to facilitate further research and reproducibility.Comment: To appear in IEEE International Conference on Communications (ICC)
202
Transmission of Images over Noisy Channels Using Error-resilient Wavelet Coding and Forward Error Correction
A novel embedded wavelet coding scheme is proposed for the transmission of images over unreliable channels. The proposed scheme is based on the partitioning of information into a number of layers which can be decoded independently provided that some important and highly protected information is initially errorlessly transmitted to the decoder. Forward Error Correction is used in conjunction with the error-resilient source coder for the protection of the compressed stream. Unlike many other robust coding schemes presented to-date, the proposed scheme is able to decode portions of the bitstream even after the occurrence of uncorrectable errors. This coding strategy is very suitable for application with block coding schemes such as defined by the JPEG2000 standard. The proposed scheme is compared with other robust image coders and is shown to be very suitable for transmission of images over memoryless channels
Instantly Decodable Network Coding: From Centralized to Device-to-Device Communications
From its introduction to its quindecennial, network coding has built a strong reputation for enhancing packet recovery and achieving maximum information flow in both wired and wireless networks. Traditional studies focused on optimizing the throughput of the system by proposing elaborate schemes able to reach the network capacity. With the shift toward distributed computing on mobile devices, performance and complexity become both critical factors that affect the efficiency of a coding strategy. Instantly decodable network coding presents itself as a new paradigm in network coding that trades off these two aspects. This paper review instantly decodable network coding schemes by identifying, categorizing, and evaluating various algorithms proposed in the literature. The first part of the manuscript investigates the conventional centralized systems, in which all decisions are carried out by a central unit, e.g., a base-station. In particular, two successful approaches known as the strict and generalized instantly decodable network are compared in terms of reliability, performance, complexity, and packet selection methodology. The second part considers the use of instantly decodable codes in a device-to-device communication network, in which devices speed up the recovery of the missing packets by exchanging network coded packets. Although the performance improvements are directly proportional to the computational complexity increases, numerous successful schemes from both the performance and complexity viewpoints are identified
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