Punctured Turbo Codes for Bandwidth-efficient Transmission

Turbo codes are the error-coding schemes applied nowadays in wireless networks. In navalapplications, the information is mostly sent through wireless networks and the data is moreprone to noise. Since very important data has to be communicated, it is necessary to get backthe original data in the receiver. In military applications also, the soldiers wear electronic jacketswhich are connected by wireless networks. In such applications, the data loss is not affordableand there is also a need to utilise the bandwidth efficiently through puncturing by means ofwhich certain bits are deleted before transmission from the output of encoder. By means of thispunctured turbo codes, bandwidth-efficient coding is achieved. Hence, it is necessary to designturbo codes with an efficient puncturing pattern so that the performance of the punctured codeis also improved in spite of deletion of few bits before transmission. This paper deals in choosingthe puncturing patterns that lead to systematic rate-compatible punctured turbo codes (RCPTCs)which also give a reduction in bit-error rate. The design criterion for choosing the best puncturingpatterns is based on the minimum weight of code words and their multiplicities. The best puncturingpattern chosen is tested for its performance by simulating turbo codes for an additive whiteGaussian noise (AWGN ) channel. Compared with the existing puncturing pattern, the patternproposed is able to achieve a gain of 0.5 dB at a bit-error rate of 10-3

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

Cross-Layer design and analysis of cooperative wireless networks relying on efficient coding techniques

2011/2012This thesis work aims at analysing the performance of efficient cooperative techniques and of smart antenna aided solutions in the context of wireless networks. Particularly, original contributions include a performance analysis of distributed coding techniques for the physical layer of communication systems, the design of practical efficient coding schemes that approach the analytic limiting bound, the cross-layer design of cooperative medium access control systems that incorporate and benefit from advanced physical layer techniques, the study of the performance of such solutions under realistic network assumptions, and, finally the design of access protocols where nodes are equipped with smart antenna systems.XXV Ciclo198

Communication coopérative, codage distribué, réseaux sans fil de relais

With the rapid growth of wireless technologies, devices and mobile applications, the quest of high throughput and omnipresent connectivity in wireless networks increases rapidly as well. It is well known that cooperation increases significantly the spectral efficiency (coding gain) and the reliability (diversity gain) of the transmission between the nodes. The concept of cooperation in wireless relays network is still one of the most active research topics in wireless communication, scientists are still searching for the optimal cooperation strategies that make the possible gains at the maximum. Cooperation results when nodes in a network share their power and/or bandwidth resources to mutually enhance their transmissions and receptions. In wireless relay networks, the relays are special nodes that are used to improve the quality of communication between the source nodes and the destination nodes. In particular, the use of relays guarantees more efficient and reliable networks. In this work, we focus on a special wireless relay network where a set of sources (mobiles) want to communicate their messages to a common destination (base station) with the help of a set of relaysAt the beginning of this work, we focused on the cooperative scheme where the relay, after a fixed portion of time, tries to understand (decode) the source’s messages and forwards helpful signals for the correctly decoded ones. One of the limitations of the previous cooperative scheme is the fixe listening time of the relays, which cannot be adapted to the quality of the instantaneous sources-relays links. To solve this problem we propose a more advanced cooperative scheme where the listening time of each relay can be dynamic and not fixed in advanced. So the relay that has strong links with the sources can start cooperating earlier than the other relays with weak links. Currently, we are investigating other directions of possible improvements, for example, how can we use feedback signals to improve the efficiency of the network.Avec la croissance rapide des appareils et des applications mobiles, les besoins en débit et en connectivité dans les réseaux sans fil augmentent rapidement. Il est prouvé que les communications coopératives peuvent augmenter significativement l’efficacité spectrale et la fiabilité des transmissions entre les nœuds extrémaux. Le concept de coopération dans un réseau sans fil compte parmi les sujets de recherche les plus actifs en télécommunications, le but étant d'identifier les stratégies de coopération qui maximiseraient les gains en efficacité spectrale et en puissance d'émission. Pour coopérer, les nœuds du réseau partagent leurs ressources (énergie, bande de fréquence, etc. ...) pour améliorer mutuellement leurs transmissions et leurs réceptions. Dans les réseaux sans fil avec relais, les relais sont des nœuds dédiés à améliorer la qualité de la communication entre les nœuds sources et destination.Dans la première partie de la thèse, nous nous concentrons sur un réseau sans fil avec relais spécifique où l'ensemble de sources (mobiles) veulent communiquer leurs messages à une destination commune (station de base) avec l'aide d'un ensemble de relais (contexte cellulaire, sens montant). Nous étudions, sur les plans théorique et pratique, un schéma coopératif dans lequel les relais, après une durée d'écoute fixée a priori, essayent de décoder les messages des sources et commencent à transmettre des signaux utiles pour ceux qui sont décodés correctement. Ces signaux utiles sont le résultat d'un codage canal-réseau conjoint.Une des limitations du système coopératif précédent est précisément que le temps d'écoute des relais est figé et ne peut pas être adapté à la qualité fluctuante (aléatoire) des liens instantanés sources-relais. Pour pallier cette difficulté, nous proposons et analysons, dans une seconde partie de la thèse, un schéma de coopération plus avancé où le temps d'écoute de chaque relais peut être dynamique. Dans ces conditions, un relais bénéficiant d'une meilleure qualité de réception des sources peut commencer à coopérer plus tôt que d'autres relais ayant une qualité de réception moindre.Enfin, dans la troisième et dernière partie de la thèse, nous considérons la présence d'une information de retour limitée (limited feedback) entre la destination et les sources et les relais, et tentons de caractériser l'efficacité spectrale d'un tel système

Some notes on rate-compatible punctured turbo codes (RCPTC) design

In this letter, we propose and compare some design criteria for the search of good rate-compatible systematic turbo codes (RCPTC) families. The considerations presented by Benedetto et al. to find "best" component encoders for turbo-code construction are extended to find good rate-compatible puncturing patterns leading to codes with promising performances

Some notes on partially systematic rate-compatible punctured turbo codes (RCPTC) design

In this paper, we present some results of the search for good partially systematic rate-compatible punctured turbo codes (RCPTC) and compare them with classical systematic RCPTCs. Partially systematic RCPTCs can achieve lower error floors than systematic RCPTCs, because of their superior free distance properties. Moreover, they can achieve comparable performance in the waterfall region if the design of the puncturing scheme is carefully addressed. The two main applications of this technique are its use in hybrid incremental ARQ/FEC schemes and to achieve unequal error protection of an information sequence