Techniques for unequal error protection.

Ho Man-Shing.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 65-66).Abstracts in English and Chinese.Acknowledgement --- p.iAbstract --- p.iiList of Abbreviation --- p.iiiChapter 1. --- Introduction --- p.1Chapter 1.1 --- Digital Communication System --- p.3Chapter 1.2 --- Thesis Organization --- p.4Chapter 2. --- Error-Correcting Codes --- p.6Chapter 2.1 --- Convolutional Codes --- p.7Chapter 2.1.1 --- Generator Polynomials --- p.8Chapter 2.1.2 --- Generator Matrix --- p.9Chapter 2.1.3 --- Circuit Diagram --- p.10Chapter 2.1.4 --- State-transition Diagram --- p.11Chapter 2.1.4 --- Trellis Diagram --- p.12Chapter 2.1.5 --- Distance property --- p.13Chapter 2.2 --- Rate-Compatible Punctured Convolutional Codes --- p.14Chapter 2.3 --- Trellis-Coded Modulation --- p.17Chapter 2.3.1 --- General Model of TCM --- p.18Chapter 2.3.2 --- Trellis Representation --- p.20Chapter 2.3.3 --- Set Partitioning --- p.21Chapter 2.3.4 --- Code Modulation --- p.23Chapter 2.4 --- Decoding Algorithm --- p.25Chapter 2.4.1 --- Viterbi Algorithm --- p.27Chapter 2.4.2 --- List Viterbi Algorithm --- p.30Chapter 3. --- Unequal-Error-Protection for Embedded Image Coder --- p.33Chapter 3.1 --- SPIHT Coder --- p.35Chapter 3.1.1 --- Progressive Image Transmission --- p.36Chapter 3.1.2 --- Set Partitioning Sorting Algorithm --- p.37Chapter 3.1.3 --- Spatial Orientation Trees --- p.38Chapter 3.2 --- System Description --- p.39Chapter 3.3 --- Code Allocation --- p.41Chapter 3.4 --- System Complexity --- p.42Chapter 3.5 --- Simulation Result --- p.43Chapter 4. --- Unequal-Error-Protection Provided by Trellis-Coded Modulation --- p.51Chapter 4.1 --- System Description --- p.52Chapter 4.2 --- Unequal Constellation --- p.53Chapter 4.3 --- Free Distance --- p.55Chapter 4.4 --- Simulation Results --- p.59Chapter 5. --- Conclusion --- p.63Bibliography --- p.6

Design Of Fountain Codes With Error Control

This thesis is focused on providing unequal error protection (uep) to two disjoint sources which are communicating to a comdestination via a comrelay by using distributed lt codes over a binary erasure channel (bec), and designing fountain codes with error control property by integrating lt codes with turbo codes over a binary input additive white gaussian noise (bi-awgn) channel. A simple yet efficient technique for decomposing the rsd into two entirely different degree distributions is developed and presented in this thesis. These two distributions are used to encode data symbols at the sources and the encoded symbols from the sources are selectively xored at the relay based on a suitable relay operation before the combined codeword is transmitted to the destination. By doing so, it is shown that the uep can be provided to these sources. The performance of lt codes over the awgn channel is well studied and presented in this thesis which indicates that these codes have weak error correction ability over the channel. But, errors introduced into individual symbols during the transmission of information over noisy channels need correction by some error correcting codes. Since it is found that lt codes alone are weak at correcting those errors, lt codes are integrated with turbo codes which are good error correcting codes. Therefore, the source data (symbols) are at first turbo encoded and then lt encoded and transmitted over the awgn channel. When the corrupted encoded symbols are received at receiver, lt decoding is conducted folloby turbo decoding. The overall performance of the integrated system is studied and presented in this thesis, which suggests that the errors left after lt decoding can be corrected to some extent by turbo decoder

A New Construction Scheme of Convolutional Codes

Abstract-A new class of (2k, k, 1) convolutional codes is proposed based on the method that creating long codes by short ones in this paper, by embedding (2k, k) double loop cyclic codes in (2, 1, 1) convolutional codes. The structural mechanism of the codes is revealed by defining a state transition matrix and using algebraic method. It is then shown that the code structure is excellent in both proportionality and diversity, so a superior code is easy to be obtained. Simulation results show that, the new convolutional codes present advantages over the traditional (2, 1, l) codes in the errorcorrecting capability and decoding speed

Physical-Layer Cooperation in Coded OFDM Relaying Systems

Mobile communication systems nowadays require ever-increasing data rate and coverage of wide areas. One promising approach to achieve this goal is the application of cooperative communications enabled by introducing intermediate nodes known as relays to support the transmission between terminals. By processing and forwarding the receive message at the relays, the path-loss effect between the source and the destination is mitigated. One major limit factor for relay assisted communications is that a relay cannot transmit and receive using the same physical resources. Therefore, a half-duplex constraint is commonly assumed resulting in halved spectral efficiency. To combat this drawback, two-way relaying is introduced, where two sources exchange information with each. On the other hand, due to the physical limitation of the relays, e.g., wireless sensor nodes, it's not possible to implement multiple antennas at one relay, which prohibits the application of multiple-input multiple-output (MIMO) techniques. However, when treating multiple relays as a cluster, a virtual antenna array is formed to perform MIMO techniques in a distributed manner. %This thesis aims at designing efficient one-way and two-way relaying schemes. Specifically, existing schemes from the literature are improved and new schemes are developed with the emphasis on coded orthogonal frequency division multiplexing (OFDM) transmissions. Of special interest is the application of physical-layer network coding (PLNC) for two-phase two-way relaying. In this case, a network coded message is estimated from the superimposed receive signal at the relay using PLNC schemes. The schemes are investigated based on a mutual information analysis and their performance are improved by a newly proposed phase control strategy. Furthermore, performance degradation due to system asynchrony is mitigated depending on different PLNC schemes. When multiple relays are available, novel cooperation schemes allowing information exchange within the relay cluster are proposed that facilitate distributed MIMO reception and transmission. Additionally, smart signaling approaches are presented to enable the cooperation at different levels with the cooperation overhead taken into account adequately in system performance evaluation

Replacing the Soft FEC Limit Paradigm in the Design of Optical Communication Systems

The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit-error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high order modulation formats, the use of the soft FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis

Product Code Optimization for Determinate State LDPC Decoding in Robust Image Transmission

We propose a novel scheme for error resilient image transmission. The proposed scheme employs a product coder consisting of LDPC codes and RS codes in order to deal effectively with bit errors. The efficiency of the proposed scheme is based on the exploitation of determinate symbols in Tanner graph decoding of LDPC codes and a novel product code optimization technique based on error estimation. Experimental evaluation demonstrates the superiority of the proposed system in comparison to recent state-of-the art techniques for image transmission

Robust Transmission of H.264/AVC Streams Using Adaptive Group Slicing and Unequal Error Protection

We present a novel scheme for the transmission of H.264/AVC video streams over lossy packet networks. The proposed scheme exploits the error-resilient features of H.264/AVC codec and employs Reed-Solomon codes to protect effectively the streams. A novel technique for adaptive classification of macroblocks into three slice groups is also proposed. The optimal classification of macroblocks and the optimal channel rate allocation are achieved by iterating two interdependent steps. Dynamic programming techniques are used for the channel rate allocation process in order to reduce complexity. Simulations clearly demonstrate the superiority of the proposed method over other recent algorithms for transmission of H.264/AVC streams

16-QAM Hierarchical Modulation Optimization in Relay Cooperative Networks

16-QAM Hierarchical Modulation Optimization in Relay Cooperative Networks Sara Sallam Recently, the concept of cooperative networks has attracted special attention in the field of wireless communications. This is due to their ability in achieving diversity with no extra hardware cost. The main drawback that characterizes cooperative networks is that they require extra transmission time slots compared to the traditional non-cooperative networks. Several strategies have been proposed in order to mitigate this disadvantage. One of the most recently adopted techniques is the use of hierarchical modulation. Hierarchical modulation was originally used in Digital Video Broadcast (DVB) applications. Lately, it has been applied in cooperative networks for its ability to transmit relative high data rate with acceptable performance. In this thesis, the application of a 4/16 QAM hierarchical modulation in cooperative networks is examined. This study focuses on a downlink cellular network scenario, composed of a Base Station, a Relay and two destinations. The Base Station intends to transmit two different streams of data to these two destinations by concatenating the two streams and broadcasting the resulting sequence using a non-uniform 4/16 QAM hierarchical modulation. Unlike previous work, the main contribution in this thesis is the optimization of the 16QAM constellation’s parameters according to each user’s channel condition. In other words, this method gives each user’s data the priority it needs in order to be detected as correctly as possible at the destination. Explicit closed form expressions of Hierarchical modulation Bit Error Rate in relay cooperative networks are derived. These BER expressions are used in order to select the constellation’s parameters that will achieve total minimum BER in coded and un-coded schemes. Results prove that the proposed method achieve noticeable improvement in both users performance compared to the use of uniform 16QAM constellation