Combined turbo codes and interleaver design

The impact of the distance spectrum and interleaver structure on the bit error probability of turbo codes is considered. A new turbo code design method for Gaussian channels is presented. The proposed method combines a search for good component codes with interleaver design. The optimal distance spectrum is used as the design criterion to construct good turbo component codes at low signal-to-noise ratios (SNRs). In addition, an interleaver design method is proposed. This design improves the code performance at high SNR. Search for good component codes at low SNR is combined with a code matched interleaver design. This results in new turbo codes with a superior error performance relative to the best known codes at both low and high SNR. The performance is verified by both analysis and simulation     

An overview of adaptive techniques for interference minimization in CDMA systems

This paper gives a brief review of several adaptive techniques for interference minimization in CDMA (code division multiple access) communication systems.Co-channel interference (CCI) in CDMA is the most dominant factor that limits the user capacity (definition). An overview of CCI cancellation and suppression schemes for sub-optimum but practical single user and multi-user demodulation in CDMA is presented.These techniques include adaptive temporal and spatial cancellers and adaptive digital filters. It has been demonstrated that adaptive receivers can effectively remove CCI and significantly increase the user capacity relative to the conventional matched filter receivers.     

An iterative singular vectors estimation scheme for beamforming transmission and detection in MIMO systems

A novel iterative singular vector estimation scheme has been proposed for a beamforming transmission and detection in wireless multiple input multiple output (MIMO) systems. Two singular channel matrix vectors, which correspond to the largest singular value, are iteratively obtained at the transmitter and the receiver without estimating the channel coefficients. The proposed singular vectors estimation strategy has advantages over the conventional MIMO channel estimation schemes in terms of both frame-error-rate performance, bandwidth efficiency and computation complexity.     

Design of cyclic shift interleavers for Turbo Codes

In this paper we consider cyclic shift interleavers for turbo coding. The properties of cyclic shift interleavers are discussed and compared with S-random interleavers. It is shown that the cyclic shift interleavers are equivalent or better than the S-random interleavers in the ability to break low weight input patterns. We estimated the performance of turbo codes with cyclic shift interleavers and compared it with the performance of S-random interleavers for varions interleaver sizes. The simulation results show that a turbo code with a cyclic shift interleaver can achieve a better performance than an S-random interleaver if the parameters of the cyclic shift interleaver are chosen properly. In addition, the cyclic interleavers have the advantages of lower design complexity and memory requirements.     

Space-time trellis codes for 8-PSK with two, three and fourtransmit antennas in quasi-static flat fading channels

Good 8-PSK space-time trellis codes (STTCs) for two, three and four transmit antennas are reported and the performance is evaluated by simulation. The new STTCs with three and four transmit antennas achieve large performance improvements over those with two transmit antennas     

Analytical upper bounds for convolutional coded CPM over rings

Analytical upper bounds on symbol error probability for ring convolutional coded Continuous Phase Modulation (CPM) with Maximum Likelihood Sequence Detection (MLSD) are presented. The constructed bounds for the investigated systems are shown to be asymptotically tight for increasing channel Signal-to-Noise Ratio (SNR) values. This work provides an analysis tool for the investigated systems. The analysis method is very general. It may be applied to any trellis based coding schemes.     

Synthesis of starch benzoate in aqueous media

Summary The results of investigating starch benzoate (SB) synthesis in aqueous media are presented in this study. Starch esterification with benzoyl chloride was performed in two steps, the first step being the alkalization of starch and the second step esterification. The influence of the concentration of reactants, reaction medium composition, temperature and time of synthesis on the degree of substitution (DS), degree of swelling in water and thermal stability of the synthesized starch benzoate was investigated. The optimal conditions for the synthesis of starch benzoate with degree of substitution from 0.23 to 1.76 were determined. It was shown that starch benzoate with a DS of 1.76 practically did not swell in water. However, starch benzoate is less thermally stable than native starch probably due to a change in the supermolecular order induced by the esterification reaction. Received: 18 March 2002/Revised version: 18 October 2002/ Accepted: 28 October 2002 Correspondence to Katarina Jeremić     

Piezoresistivity and electro-thermomechanical degradation of a conducting layer of nanoparticles integrated at the liquid crystal elastomer surface

When a liquid crystal elastomer (LCE) is reprocessed with conducting nanosized particles a conducting layer can be formed at the LCE surfaces. Here, two different LCE materials and two different conducting carbon particles were used. These four reprocessed LCEs were investigated when subject to a thermal phase transition and mechanical extension. Here it is shown that the resistance change with strain ('piezoresistivity') for these reprocessed LCEs can be described through lattice percolation and geometrical changes in the LCE shape. The mechanisms and rate of degradation are also described for the conducting layer as a function of the number of electro-thermomechanical strain cycles performed.