Impulsive noise is one of the major challenges for reliable transmission over power lines. Interleavers provide higher protection against the impulsive noise by dispersing information across the channel and spreading the burst of errors over multiple codewords. Multi‐fold turbo (MFT) coding is a technique that improves the communication reliability using multiple interleavers. In the MFT codes, each data subsequence is equally protected. For applications in which data constitute information with various levels of importance, it is intuitive to offer the more important subsequence, a stronger protection. A modified form of the MFT codes capable of providing unequal error protection over a two‐user power‐line binary adder channel is proposed here. As a benchmark, two test images are transmitted across the channel. The trellis‐based iterative algorithm is modified for the two‐user scenario to decode the received signal. The simulation results show a gain of 1.5 dB for the modified MFT code over the conventional turbo codes for each of the transmitted images. A gain of 2 dB is also recorded for the most protected component of each image over the least protected components.

In this work, the authors have developed a deterministic Ultra Wide Band (UWB) channel model for indoor environment using both ray-tracing technique and the art of computer game technology in 3D Game Studio (game development tool). In the developed model, the characteristics of indoor environment such as texture, transparency etc. can be taken into consideration while indoor parameters such as room size, objects position etc. can be interactively changed. Each time, indoor environment is changed, the program is compiled and hence, the underlying ray-tracing captures the updated indoor environment. It is the key novelty of the authors’ developed model and it has been so incorporated to make the authors’ model independent of any fixed (pre-defined) indoor environment. The developed model is compared against the standard statistical UWB channel model based on certain parameters such as delay spread etc. to address its validity and accuracy. The model is then enhanced to use multiple antennas on both sides of the system and capture the channel response accordingly. Finally, the developed model has been tested over a range of frequencies to see frequency effect on the channel impulse response. The simulation results have been presented and discussed in the simulation section.

It has been 20 years since the word ultrawideband (UWB) has first been used in the open literature. In these 20 years, ideas have been transformed into real products. Yet, some might object that UWB has not yet lived upto the promises of gigabit wireless. This review shows that despite some drawbacks, UWB is not only needed because of the spectrum gridlock but it can still deliver its promises, including gigabit wireless. To do so, the gap between the potential, which is achievable, and the current performance must be closed. Thus, this review identifies some main issues of UWB (range, bit error rate performance, data rate, chip complexity and issues associated by strong narrowband interference). It shows that their reasons are well understood and addressed by erudite research, which includes low complexity chip design, alternative modulation schemes, multiple antenna systems, UWB radio-over-fibre, higher band UWB and interferer detection and suppression techniques. A specific feature of this review is the cross-layer approach. The latest findings from different system layers, for example, wave propagation, are linked to the system performance or complexity.

A switchable-rate quasi-cyclic low-density parity-check (QC-LDPC) coding scheme has been proposed for integration within the legacy and next-generation high-frequency internet protocol (HF-IP) systems. The novelty in this work is based upon using a class of switchable-rate short-block-length (<1500 bits) QC-LDPC codes for the HF fading channel modelled by the ITU-R F.1487 for all latitudes and conditions. The QC-LDPC codes are constructed using a switchable-rate approach based on finite fields which provides the ability to switch among three rates to combat varying channel conditions using a single encoder/decoder structure. The proposed structure enables low-complexity implementation of the low-density parity-check encoder/decoder for use within the existing data link (DL) layer of the standardisation agreement (STANAG) 5066 profile. The performance of the proposed scheme has been evaluated comprehensively for all the HF channel conditions and latitudes. A comparison between the proposed and the current coding scheme in HF-IP systems (based on convolutional coding) shows an improvement in error-rate performance.

Abstract The public key cryptosystem (PKC) based on rank error correcting codes (the GPT cryptosystem) was proposed in 1991. Use of rank codes in cryptographic applications is advantageous since it is practically impossible to utilize combinatoric decoding. This enabled using public keys of a smaller size. Several attacks against this system were published, including Gibson's attacks and more recently Overbeck's attacks. A few modifications were proposed withstanding Gibson's attack but at least one of them was broken by the stronger attacks by Overbeck. A tool to prevent Overbeck's attack is presented by Gabidulin, which makes the cryptographer define a proper column scrambler matrix over the extension field without violating the standard mode of GPT cryptosystem. In this paper, we apply this tool to another variant of the GPT cryptosystem. Furthermore we increase the security of the proposed system against all known attacks and reduce the public key size to 4 Kbits instead of 10 Kbits. Copyright © 2010 John Wiley & Sons, Ltd.

The concept of Public-key cryptosystem was innovated by McEliece's cryptosystem. The public key cryptosystem based on rank codes was presented in 1991 by Gabidulin -Paramonov-Trejtakov (GPT). The use of rank codes in cryptographic applications is advantageous since it is practically impossible to utilize combinatoric decoding. This has enabled using public keys of a smaller size. Respective structural attacks against this system were proposed by Gibson and recently by Overbeck. Overbeck's attacks break many versions of the GPT cryptosystem and are turned out to be either polynomial or exponential depending on parameters of the cryptosystem. In this paper, we introduce a new approach, called the Smart approach, which is based on a proper choice of the distortion matrix X. The Smart approach allows for withstanding all known attacks even if the column scrambler matrix P over the base field Fq.

Almost all modern cars can be controlled remotely using a personal communicator (keyfob). However, the degree of interaction between currently available personal communicators and cars is very limited. The communication link is unidirectional and the communication range is limited to a few dozen meters. However, there are many interesting applications that could be supported if a keyfob would be able to support energy efficient bidirectional longer range communication. In this paper we investigate off-the-shelf transceivers in terms of their usability for bidirectional longer range communication. Our evaluation results show that existing transceivers can generally support the required communication ranges but that links tend to be very unreliable. This high unreliability must be handled in an energy efficient way by the keyfob to car communication protocol in order to make off-the-shelf transceivers a viable solution.

The public key cryptosystem based on rank error correcting codes (the GPT cryptosystem) was proposed in 1991. Use of rank codes in cryptographic applications is advantageous since it is practically impossible to utilize combinatoric decoding. This enabled using public keys of a smaller size. Several attacks against this system were published, including Gibson's attacks and more recently Overbeck's attacks. A few modifications were proposed withstanding Gibson's attack but at least one of them was broken by the stronger attacks by Overbeck. A tool to prevent Overbeck's attack is presented in. In this paper, we apply this approach to other variants of the GPT cryptosystem.

This paper presents new methods for constructing efficiently encodable quasi-cyclic LDPC codes based on special balanced incomplete block designs (BIBD's). Codes constructed perform well over both the AWGN and binary erasure channels with iterative decoding.

The presence and availability of several independent wired and wireless networks within a communication environment has led to the channel adaptive multiple I/O (CAMIO) protocol being developed as an appropriate and novel technique for data transmission. The proposed system utilises an intelligent multiplexing technique that enables the transmission/reception of multiple data sources via several wired/wireless networks simultaneously. Real-time configuration and adaptation capabilities when data sources/channels are dynamically added/deleted/modified are described. Data prioritisation methods, combined with traffic control and congestion-reactive techniques, are presented. Simulation results demonstrate that the use of the CAMIO protocol over multiple transmission/reception channels increases the overall data transmission rate, handles the delivery of time-sensitive packets and maintains the quality of service, especially in situations where one or more communication channels fail to operate.

This paper presents new methods for efficiently constructing encodable quasi-cyclic low-density parity-check (LDPC) codes based on special balanced incomplete block designs (BIBDs). Codes constructed perform well over both the additive white Gaussian noise (AWGN) and binary erasure channels with iterative decoding.

Recently, a symbol detection scheme based on the Viterbi algorithm was proposed for binary Two Dimensional Optical Storage (TwoDOS) in the presence of Additive White Gaussian noise (AWGN). In this paper, we extend the symbol detection scheme to allow for multilevel modulation. We demonstrate the proof of concept in a typical non-linear high density storage channel with intersymbol interference and AWGN. The relative performance, between multilevel and binary modulations is presented, where multilevel modulation provides better performance in higher capacities.

Through the use of F-metrics, a McEliece type public-key cryptosystem based around generalised Reed Solomon codes is constructed and implemented. Using such metrics increases the complexity of the system making it harder to attack allowing for smaller key-sizes. Attacks on such a system are also investigated

A new approach is proposed for constructing regular low-density parity-check (LDPC) codes based on tensor product of matrices. In this paper, first a general construction method of regular LDPC codes exploiting permutation matrices is described. Constructed codes have a quasi-cyclic structure with no short cycles of length 4 in their Tanner graph, hence simple encoding while maintaining good performance is achieved. The paper also demonstrates a generalized design, which covers a large family of LDPC codes and number of other construction methods. The new generalized LDPC codes are defined by a small number of parameters and cover a large set of code lengths and rates. Using these codes, LDPC matrices of any column weight and row weight can be constructed. Performance of these codes under iterative decoding compares well with other well-structured as well as random LDPC codes

We describe a symbol detection scheme for multilevel two dimensional optical storage (TwoDOS), where the channel is characterized by non-linear inter symbol interference and the dominant source of noise is media noise, both of which are characterized accurately by a non-linear channel model. Signal waveforms from the channel model are described as an explicit function of the channel symbols. Based on the non-linear model including media noise, we design and develop a practical symbol detection scheme for multilevel TwoDOS. This low complexity detection scheme is simulated for multilevel data for discs with different densities in the presence of media noise. Our proposed detection scheme exploits the properties of the 2D data format on the disc and is flexible enough to accommodate performance and complexity restrictions.

A new and challenging concept for optical storage is being developed, in which the information written on the disc has a two-dimensional characteristic, with the aim of realizing an increase of a factor of two in data density and a factor of ten in data rate over the current 3rd generation of optical storage (Blu-Ray Disc, BD). Experimental channel characterization provides insight into the magnitude of intersymbol interference, signal levels, modulation and noise distribution from the measured signal waveform. This information is used to evaluate the quality of the mastered discs, and provide feedback in the optimization process. It also yields essential input to the actual design of the signal processing solutions. The stages involved in characterizing the channel are downsampling and model fitting using a scalar diffraction model. The information gathered from channel characterization is demonstrated with experimental measurements from discs with an initial density of 1.4/spl times/BD using the same physical read-out system (blue laser and high-NA lens).

This correspondence presents a method for constructing structured regular low-density parity-check (LDPC) codes based on a special type of combinatoric designs, known as balance incomplete block designs. Codes constructed by this method have girths at least 6 and they perform well with iterative decoding. Furthermore, several classes of these codes are quasi-cyclic and hence their encoding can be implemented with simple feedback shift registers.

We present a new family of so-called reducible rank codes which are a generalization of rank product codes . This family includes maximal rank distance (MRD) codes for lengths n>N in the field F/sub N/. We give methods for encoding and decoding reducible rank codes. A public key cryptosystem based on these codes and on the idea of a column scrambler is proposed. The column scrambler "mixes" columns of a generator (parity-check) matrix of a code. It makes the system more resistant to structural attacks such as Gibson's attacks. Possible attacks on the system are thoroughly studied. The system is found to be secure against known attacks for public keys of about 16 kbits and greater.

The concept of the reconfigurable radio system requires new methods for the design and maintenance of the signal processing hardware and its flexible software and configurations. Existing methods used for hardware and software codesign need modification to take into account increased redundancy and how it may be used dynamically throughout the lifetime of the hardware platform. This paper describes the design flow used to build a reconfigurable processing demonstrator which is primarily intended to reconfigure between DCS1800 and UTRA air interfaces. This demonstrator forms part of the EU funded CAST (configurable radio with advance software technology) project.

The design of uniquely decodable DC-free multi-user coding schemes with good rate sums for the multiple access adder channel is described in this paper. It is shown that by using the direct sum construction on short multi-user codes, it is possible to devise longer DC-free multi-user coding schemes with rate sums which increase quite rapidly at each iteration of the construction. Asymptotically, there is no penalty in requiring the coding schemes to be DC-free. In addition, the schemes can be efficiently soft decision decoded using a relatively low complexity sectionalised trellis.

Turbo product codes (TPCs) provide an attractive alternative to recursive systematic convolutional (RSC)-based turbo systems. Rather than employ trellis-based decoders, an algebraic decoder may be repeatedly employed in a low-complexity, soft-input/soft-output errors-and-erasures decoder such as the Chase algorithm. Taking motivation from efficient forced erasure decoders, this implementation re-orders the Chase algorithm's repeated decodings such that the inherent computational redundancy is greatly reduced without degrading performance. The result is a highly efficient fast Chase implementation. The algorithm presented here is principally applicable to single error-correcting codes although consideration is also given to the more general case. The new decoder's value in practical turbo schemes is demonstrated via application to decoding of the (64,57,4) extended Hamming TPC.

We give simple sufficient conditions for a code to be rectangular and show that large families of well-known nonlinear codes are rectangular. These include Hadamard (1893), Levenshtein (1964), Delsarte-Goethals (1975), Kerdock (1972), and Nordstrom-Robinson (1967) codes. Being rectangular, each of these codes has a unique minimal trellis that can be used for soft-decision maximum-likelihood decoding.

A novel trellis design technique for both block and convolutional codes based on the Shannon (1956) product of component block codes is introduced. Using the proposed technique, structured trellises for block and convolutional codes have been designed. It is shown that the designed trellises are minimal and allow reduced complexity Viterbi decoding.

Superimposed codes for multiple-access communication in a binary adder channel are analyzed. The superposition mechanism used in this correspondence is ordinary addition. Each user is assigned a codeword from a superimposed code. It is proved that every constant-weight code C of weight w and maximal correlation c corresponds to a subclass of a disjunctive code D of order m>