Structure Of Convolutional Codes Research Articles

Faster-Than-Nyquist Signal Design for Multiuser Multicell Indoor Visible Light Communications

We consider a typical indoor environment, where multiple light-emitting diode (LED) lamps are equipped, and each LED lamp is the base station of an optical cell. A faster-than-Nyquist signal design is presented for multiuser multicell (FTNMM) visible light communication (VLC) broadcasting systems, where all the transmitters transmit independently with a properly designed time delay to achieve multiple times spectral efficiency. The performance of FTNMM is analyzed in view of the minimum Euclidean distance of symbol sequence, and it is proved that the minimum Euclidean distance remains unchanged as transmitter number and symbol length increase. To reduce the complexity of the maximum-likelihood sequence estimation decoding algorithm, a convolutional code structure with dynamic weights and a fast iterative receiver for FTNMM are developed. Simulation results show that the proposed FTNMM obtains significant performance gains over currently available schemes.

Hybrid Concatenated Convolutional Code for Deep Space Mission

In satellite communication deep space mission are the most challenging mission, where system has to work at very low Eb/No. Concatenated codes are the ideal choice for such deep space mission. ISRO is planning to send unmanned mission for Mars and several deep space missions in future to study and detailed understanding of our own universe. This paper basically reviews the Hybrid concatenated convolutional code structure and selects the suitable candidate for our future deep space mission. The complete simulation using Simulink is done and results are presented in this paper.

Analysis and Comparison of Some Recent Classes of Turbo Like Codes for the Upcoming DVB Standards

In this paper, a number of powerful recent classes of turbo like codes are analyzed as possible candidates for theupcoming DVB Standards. The final selection is justified in terms of the best tradeoff between complexity and performance. One of these classes has been recently proposed by the authors in the framework of their ongoing work on the technologies, requested by the DVB Project, which could be considered as candidates for the second generation terrestrial transmission standard DVBT2(specification to be completed in 2009). In particular, withthe aim of maintaining the maximum compatibility with thefamily of DVB standards, the authors are currently addressing individual technology elements for the DVB-T2 standard, such as practical low-complexity coding structures. To this end, a serial concatenated convolutional code structure has been proposed, which is expected to overcome the turbo like coding schemes currently used in the family of DVB standards.

Iterative demodulation and decoding of frequency-hopped PSK in partial-band jamming

This paper considers the problem of developing and utilizing side information in a frequency-hopped communication system using phase-shift keying (PSK) and operating in an environment with partial-band jamming. Two aspects of side information are studied. The first deals with estimating the unknown random carrier phase that varies from hop to hop. The second aspect is the detection of jamming signals. We use a serially concatenated convolutional code structure with differential M-ary PSK as the inner code. The iterative receiver uses an expanded trellis in the inner decoder to resolve the phase ambiguity and is augmented by a ratio-threshold test for detecting jammer energy. Performance is compared for different dwell interval lengths and both log-APP and max-log-APP decoding algorithms. This paper also considers the effect of different thresholds on the false alarm and detection probabilities of the ratio-threshold test.

16-state space-time code for 16PSK modulation

A novel 16-state space-time (ST) code for 16-phase-shift keying (PSK) modulation is presented in the quasi-static fading channel environment. The proposed code for 16PSK is designed by adopting the ring convolutional code structure to construct a Z16-valued ST code for 16PSK modulation, and is extended by applying two optimal code search criteria as reported previously by others (refs 2, 3).

Convolutional code structure and the performance of the Viterbi algorithm (Ph.D. Thesis abstr.)

Convolutional code structure and the performance of the Viterbi algorithm (Ph.D. Thesis abstr.)

Convolutional Codes and Their Performance in Communication Systems

This tutorial paper begins with an elementary presentation of the fundamental properties and structure of convolutional codes and proceeds with the development of the maximum likelihood decoder. The powerful tool of generating function analysis is demonstrated to yield for arbitrary codes both the distance properties and upper bounds on the bit error probability for communication over any memoryless channel. Previous results on code ensemble average error probabilities are also derived and extended by these techniques. Finally, practical considerations concerning finite decoding memory, metric representation, and synchronization are discussed.

Use of a sequential decoder to analyze convolutional code structure (Corresp.)

An existing sequential decoding program can be easily modified to enumerate the number of low-weight codewords in a convolutional code, where weight is defined either over a decoding constraint length or "free." We tabulated several good rate one-half constraint-length 49 systematic codes that were obtained quickly with this procedure.