Cooperative wireless communication has received significant attention during recent years due to several reasons. First, since the received power decreases rapidly with distance, the idea of multi-hopping is becoming of particular importance. In multi-hopped communication, the source exploits some intermediate nodes as relays. Then the source sends its message via those relays to the destination. Second, relays can emulate some kind of distributed transmit antennas to form spatial diversity and combat multi-path fading effect of the wireless channel. Parallel Relay Channel is an information theoretical model for a communication system whereby a sender aims to communicate to a receiver with the help of relay nodes. It represents the simplest model for a multi–hop wireless network and a full understanding of the limits of communication over such a channel can potentially shed light on the design of more efficient wireless networks. However, the capacity of the relay channel has been established only for few special cases and little progress has been made toward solving the general case since the early 1980s. In this dissertation, motivated by practical constraints, we study the information theoretical limits of the half-duplex Gaussian Parallel Relay channel , as well as, the transmission strategies for the parallel relay channel with bandwidth mismatch between the first and the second hops. Chapter 2 investigates the problem of communication for a network composed of two half-duplex parallel relays with additive white Gaussian noise (AWGN). There is no direct link between the source and the destination. However, the relays can communicate with each other through the channel between them. Two protocols, i.e., \emph{Simultaneous} and \emph{Successive} relaying, associated with two possible relay scheduling are proposed. The simultaneous relaying protocol is based on \emph{Broadcast-multiaccess with Common Message (BCM)} scheme. For the successive relaying protocol: (i) a \emph{Non-Cooperative} scheme based on the \emph{Dirty Paper Coding (DPC)}, and (ii) a \emph{Cooperative} scheme based on the \emph{Block Markov Encoding (BME)} are considered. The composite scheme of employing BME in \emph{at most} one relay and DPC in \emph{at least} another one is shown to achieve at least the same rate when compared to the \emph{Cooperative} and \emph{Non-Cooperative} schemes. A \emph{``Simultaneous-Successive Relaying based on Dirty paper coding scheme" (SSRD)} is also proposed. The optimum scheduling of the relays and hence the capacity of the half-duplex Gaussian parallel relay channel in the low and high signal-to-noise ratio (SNR) scenarios is derived. In the low SNR scenario, it is revealed that under certain conditions for the channel coefficients, the ratio of the achievable rate of the simultaneous relaying based on BCM to the cut-set bound tends to be 1. On the other hand, as SNR goes to infinity, it is proved that successive relaying, based on the DPC, asymptotically achieves the capacity of the network. Schein and Gallager introduced the Gaussian parallel relay channel in 2000. They proposed the Amplify-and-Forward (AF) and the Decode-and-Forward (DF) strategies for this channel. For a long time, the best known achievable rate for this channel was based on the AF and DF with time sharing (AF-DF). Recently, a Rematch-and-Forward (RF) scheme for the scenario in which different amounts of bandwidth can be assigned to the first and second hops were proposed. In chapter 3, we propose a \emph{Combined Amplify-and-Decode Forward (CADF)} scheme for the Gaussian parallel relay channel. We prove that the CADF scheme always gives a better achievable rate compared to the RF scheme, when there is a bandwidth mismatch between the first hop and the second hop. Furthermore, for the equal bandwidth case (Schein's setup), we show that the time sharing between the CADF and the DF schemes (CADF-DF) leads to a better achievable rate compared to the time sharing between the RF and the DF schemes (RF-DF) as well as the AF-DF.

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Dans le canal sans fil, la communication coopérative permet à un ou plusieurs relais d’aider la transmission entre la source et la destination. L'objectif de cette thèse est de développer des outils d'analyse de performance pour les systèmes coopératifs utilisant des techniques HARQ. Le premier chapitre de cette thèse donne des informations sur le codage de réseau dans les réseaux coopératifs, et introduit la motivation pour ce travail. L’objectif du deuxième chapitre est d’analyser et d’évaluer les performances de la qualité de service (QoS) des schémas ARQ-STBC, HARQ et FEC, dans le contexte de l’efficacité énergétique, aux niveaux des couches MAC et IP. Afin d’atteindre ce but, une nouvelle méthode d'analyse est dérivé et appliqué au scénario de communication point à point (P2P). Ceci nous permet de comparer les schémas avec et sans retransmissions, et d’établir la consommation d’énergie de chaque système considéré. Cela nous permet de déterminer dans quelles conditions il est énergétiquement plus efficace d’utiliser la protection cross-layer, ou le simple codage de canal. Dans le troisième chapitre une classe de protocoles coopératifs déterministes est introduite. Les protocoles que nous considérons sont différents en termes du comportement de relais(s) de source(s), et de la destination. Nous considérons deux types de protocoles coopératifs: decode-and-forward (DCF), et demodulate-and-forward (DMF). Les performances de chacun de ces protocoles sont analysés, avec et sans combining à la destination. Les évaluations de QoS qui sont examinés sont: le taux d'erreur de trame, le délai, l'efficacité, et le goodput. Les dérivations analytiques sont effectuées à l'aide de la machine à états finis de Markov, ainsi que grâce à l’approche combinatoire. Cependant, il est démontré, que la complexité de ces dérivations augmente au moment ou le crédit de retransmissions et/ou des nœuds dans le réseau est augmentée. Donc cette approche devient non-traitable pour des grands schémas coopératifs. Le quatrième chapitre présente une classe de protocoles de communication probabilistes, où les nœuds retransmettent avec une certaine probabilité. Il est démontré l'existence d'une classe de protocoles probabilistes équivalents, qui permettent d’obtenir les mêmes performances des protocoles déterministes précédemment traités. En utilisant la preuve de concept, nous démontrons que le protocole probabiliste permet d’effectuer les évaluations analytiques de réseaux multi-nœuds, même dans le cas d'un grand nombre de nœuds dans le réseau. Basée sur cela, nous déduisons les paramètres QoS, et les évaluons également par des simulations Monte-Carlo. Les paramètres d'évaluation de performances dérivées sont optimisés en limitant le taux d'erreur de trame, et en essayant de trouver le nombre de transmissions optimal et le code rate qui maximisent le goodput. Il est également démontré que la classe de protocoles probabilistes peut atteindre une région d’optimalité plus grand que la classe de protocoles déterministes. / In the wireless channel, cooperative communications allow one or many relays to assist the communication between the source and the destination. The aim of this thesis is the development of tools for the analysis of cooperative systems, when HARQ techniques are employed to provide cross-layer error protection. The first chapter of the thesis gives background information on network coding in cooperative relay networks, and introduces the motivation for this work. The second chapter is devoted to the analysis of the energetic-fair performance evaluations of FEC, ARQ-STBC and HARQ schemes at the MAC and IP layers. New analytical framework is derived and applied to a point-to-point network scenario. This framework allows to make energetic fair comparisons between the schemes with and without retransmissions. We determine under which channel conditions the cross-layer error protection is energetically more efficient than the simple channel coding. In the third chapter of this thesis we study the cooperative deterministic protocols. The protocols that we consider differ based on the behaviour of the relay(s), source(s), and destination. We consider two major types of cooperative protocols: decode-and forward (DCF), and demodulate-and-forward (DMF). Each of these protocols in its turn is analysed with and without combining mechanisms at the destination. We derive the soft decoders at the destination side for each respective case, and compare the performances of these protocols at the MAC layer. The following quality of service metrics are evaluated: frame error rate, delay, efficiency, goodput. The analysis is done evaluating the steady-state, using finite state Markov chains and a combinatorial approach. The analysis, however, becomes very complex as the number of transmissions and/or nodes in the network increases. The fourth chapter introduces a class of probabilistic communication protocols, where the devices retransmit with a given probability. We prove the existence of an equivalent class of protocols, with the same performances as the deterministic class. Using proofs of concept it is shown that the probabilistic protocol class allows for tractable steady-state analysis, even for many nodes in the network. Based on this, we then derive the QoS metrics and evalute them also by simulations. The derived performance evaluation metrics are then optimized by constraining the frame error rate, and trying to find the most optimal transmissions number and code rates which maximize the goodput. It is furthermore shown, that the equivalent protocol has larger optimal region than the deterministic one.

Cette thèse est consacrée à l'étude théorique et à la conception pratique de schémas de codage conjoint réseau/canal adaptés à différents scénarii de communications dans les réseaux sans fil. Contrairement aux hypothèses conventionnelles retenues dans la littérature (accès multiple orthogonal, absence d'erreurs sur certains liens), les caractéristiques de diffusion et de superposition des signaux propres au canal radio et la présence d'évanouissements lents et de bruit sur tous les liens sont prises en compte dans la formulation du problème et exploitées. Différentes stratégies de coopération au niveau du ou des relais sont examinées et comparées. Le point commun entre toutes ces stratégies est que le système doit fonctionner même en absence de coopération. Seuls le ou les relais et la destination sont informés d'une coopération. Ni les sources, ni le ou les relais ne connaissent l'état du canal à l'émission.
Le premier volet de la thèse porte sur le canal à accès multiple avec relais unique (slow fading MARC). Le problème du codage et décodage conjoint canal/réseau (JNCC/JNCD) est étudié sur un plan théorique et pratique. Différentes hypothèses au niveau de l'accès multiple (semi-orthogonal et non-orthogonal) et différents modes de fonctionnement du relais (half-duplex et full-duplex) sont envisagés. Une nouvelle stratégie de coopération adaptative (SDF pour selective decode and forward) est définie dans laquelle le relais calcule et retransmet une fonction déterministe des messages de sources qu'il a pu décoder sans erreur. Le ré-encodage, défini sur un corps fini (corps binaire), est également conçu de manière à assurer que la performance finale au niveau de la destination atteint bien un ordre de diversité 2.
Le modèle de canal MARC est par la suite étendu à plusieurs relais (slow fading MAMRC). Une analyse théorique est conduite et des nouveaux schémas JNCC/JNCD permettant de s'approcher des limites théoriques sont décrits. Afin d'assurer la diversité pleine, nous proposons de combiner un codage canal binaire et un codage réseau non-binaire.
Pour les deux types de canaux, nous montrons que l'interférence naturellement induite par la diffusion des signaux dans un environnement sans fil, n'est pas un inconvénient mais bien un avantage dès lors qu'on est en mesure de la traiter via des techniques de codage et de décodage sophistiquées (turbo codes et leur décodage, turbo détection). Les gains en termes de capacité (rapportée à une certaine probabilité de coupure) obtenus avec un accès multiple semi-orthogonal ou non-orthogonal sont substantiels comparés à un accès multiple orthogonal (référence).
Dans la dernière partie de la thèse, la stratégie de coopération SDF est comparée à deux autres stratégies de coopération s'appuyant sur un procédé de décodage-et-retransmission "souple" (sans prise de décisions intermédiaires) : l'une basée sur les rapports logarithmiques de probabilité a posteriori sur les bits codés et l'autre basée sur l'estimation de l'erreur quadratique moyenne (MSE). Nous vérifions que la stratégie de coopération SDF fonctionne bien dans la plupart des configurations, les stratégies de coopération souples n'améliorant légèrement les performances que dans certains cas extrêmes. / With the rapid growth of wireless technologies, devices and mobile applications, the quest of high throughput and ubiquitous connectivity in wireless communications increases rapidly as well. Relaying is undoubtedly a key concept to provide coverage extension and capacity increase in wireless networks. Network coding, which allows the intermediate nodes to share their computation capabilities in addition to their resource and their power, has grabbed a significant research attention since its inception in information theory. It has become an attractive candidate to bring promising performance improvement, especially in terms of throughput, in relay-based cellular networks. Substantial research efforts are currently focused on theoretical analysis, implementation and evaluation of network coding from a physical layer perspective. The question is, what is the most efficient and practical way to use network coding in wireless relay-based networks, and whether it is beneficial to exploit the broadcast and multiple-access properties of the wireless medium to perform network coding. It is in such a context, that this thesis proceeds. In the first part of the thesis, the problem of Joint Network-Channel Coding (JNCC) for a Multiple Access Relay Channel (MARC) is investigated in the presence of multiple access interferences and for both of the relay operating modes, namely, half-duplex and full-duplex. To this end, three new classes of MARC, referred to as Half-Duplex Semi-Orthogonal MARC (HD-SOMARC), Half-Duplex Non-Orthogonal MARC (HD-NOMARC), and Full-Duplex Non-Orthogonal MARC (FD-NOMARC) have been introduced and studied. The relaying function in all of the classes is based on a Selective Decode-and-Forward (SDF) strategy, which is individually implemented for each source, i.e, the relay forwards only a deterministic function of the error-free decoded messages. For each class, an information-theoretic analysis is conducted, and practical coding and decoding techniques are proposed. The proposed coding schemes, perform very close to the outage limit for both cases of HD-SOMARC and HD-NOMARC. Besides, in the case of HD-NOMARC, the optimal allocation of the transmission time to the relay is considered. It is also verified that exploiting multiple access interferences, either partially or totally, results in considerable gains for MARC compared to the existing interference-avoiding structures, even in the case of single receive antenna. In the second part of the thesis, the network model is extended by considering multiple relays which help multiple sources to communicate with a destination. A new class of Multiple Access Multiple Relay Channel (MAMRC), referred to as Half-Duplex Semi-Orthogonal MAMRC (HD-SOMAMRC) is then proposed and analyzed from both information theoretic and code design perspective. New practical JNCC schemes are proposed, in which binary channel coding and non binary network coding are combined, and they are shown to perform very close to the outage limit. Moreover, the optimal allocation of the transmission time to the sources and relays is considered. Finally, in the third part of the thesis, different ways of implementing cooperation, including practical relaying protocols are investigated for the half-duplex MARC with semi-orthogonal transmission protocol and in the case of JNCC. The hard SDF approach is compared with two Soft Decode and Forward (SoDF) relaying functions: one based on log a posterior probability ratios (LAPPRs) and the other based on Mean Square Error (MSE) estimate. It is then shown that SDF works well in most of the configurations and just in some extreme cases, soft relaying functions (based on LAPPR or MSE estimate) can slightly outperform the hard selective one.

Le codage réseau est apparu comme une technique alternative au routage au niveau de la couche réseau permettant d'améliorer le débit et d'optimiser l'utilisation de la capacité du réseau. Récemment, le codage réseau a été appliqué au niveau de la couche physique des réseaux sans-fil pour profiter de la superposition naturelle des signaux effectuée par le lien radio. Le codage réseau peut être vue comme un traitement interne du réseau pour lequel différentes techniques de relayage peuvent être utilisées. Cette thèse étudie un ensemble de traitements ayant des compromis variés en terme de performance et complexité. Nous considérons le canal bidirectionnel à relais, un modèle de canal de communication typique dans les réseaux coopératifs, où deux terminaux s'échangent mutuellement des messages par l'intermédiaire d'un relais. La communication se déroule en deux phases, une phase à accès multiple et une phase de broadcast. Pour ce scénario, nous analysons, dans une première partie, une stratégie de "decode-and-forward". Nous considérons, pour cette étude, des alphabets de taille finie et nous calculons les probabilités moyennes d'erreur de bout-en-bout en se basant sur la métrique d'exposant d'erreur du codage aléatoire. Puis, nous dérivons les régions des débits atteignables par rapport à une probabilité d'erreur maximale tolérable au niveau de chaque nœud. Dans une deuxième partie de la thèse, nous proposons deux schémas de codage réseau pratiques, avec complexité réduite, qui se basent sur la stratégie de relayage "compress-and-forward" (CF). Le premier schéma utilise un codage en réseau de points imbriqués (nested lattices). Le deuxième schéma est une version améliorée qui permet d'atteindre des débits de données supérieurs pour l'utilisateur qui a les meilleures conditions canal. Nous construisons les régions des débits atteignables par les deux schémas proposés tout en optimisant la répartition du temps alloué à chacune des deux phases de transmission. Après l'étude du régime asymptotique, nous analysons le schéma de codage CF avec des réseaux de points de dimension finie. Nous nous concentrons sur le problème de la transmission analogique où la distorsion est optimisée. Enfin, nous étudions l'application d'un schéma de codage, basé sur la stratégie CF avec des réseaux de points imbriqués, pour le canal bidirectionnel à canaux parallèles. Ainsi, nous présentons deux régions de débits atteignables selon la technique de traitement, conjoint ou séparé, des sous-canaux par le relais. / Network coding has emerged as an alternative technique to routing that enhances the throughput at the network layer. Recently, network coding has been applied at the physical layer to take advantage of the natural signal superposition that occurs in the radio link. In this context, the physical-layer network coding can be seen as an in-network processing strategy for which multiple forwarding schemes can be proposed. This thesis investigates a set of processing schemes tailored to the network coding at the physical layer with various compromises between performance and complexity. We consider a two-way relay channel, a typical communication system in cooperative networks, where two terminals communicate with each other via a relay node. This communication occurs during two transmission phases, namely a multiple-access phase and a broadcast phase. For TWRC scenario, we first analyze a decode-and-forward strategy with finite size alphabets. We calculate the end-to-end average error probabilities based on random coding error exponents. Then, we derive the achievable rate regions with respect to a maximal probability of error allowed at each terminal. Next, we propose two low-complexity and practical schemes based on compress-and-forward relaying strategy. The first scheme employs nested lattice coding. The second is an improved version which enables higher data rates for the user experiencing the best channel conditions. We present an information-theoretic framework to reconstruct the achievable rate regions of both schemes by considering optimal time division between both transmission phases. After the asymptotic regime analysis, we study single-layer lattice coding scheme with finite dimension lattices. We focus on the analog transmission problem where the distortion is optimized. Finally, we investigate single-layer lattice coding scheme for parallel Gaussian two-way relay channel. We present two achievable rate regions based on whether the relay processes all the sub-channels jointly or separately.

There has recently been growing interest in using physical layer network coding techniques to facilitate information transfer in wireless relay networks. The physical layer network coding technique takes advantage of the additive nature of wireless signals by allowing two terminals to transmit simultaneously to the relay node. This technique has several performance benefits, such as improving utilization and throughput of wireless channels and reducing delay. In this thesis, we present an algorithm for joint decoding of two unsynchronized transmitters to a modulo-2 sum of their transmitted messages. We address the problems that arise when the boundaries of the signals do not align with each other and when their phases are not identical. Our approach uses a state-based Viterbi decoding scheme that takes into account the timing offsets between the interfering signals. As a future research plan, we plan to utilize software-defined radios (SDRs) as a testbed to show the practicality of our approach and to verify its performance. Our simulation studies show that the decoder performs well with the only degrading factor being the noise level in the channel.

Cooperative relay communication is a promising means of wireless communication in which cooperation is used to create a virtual transmit array between the source and the destination, thereby providing spatial diversity for combating the fading channel. In this thesis we develop cooperative communication protocols namely the orthogonal amplify-and-forward (OAF), non-orthogonal and orthogonal selection decode-and-forward (NSDF and OSDF) protocols. The diversity-multiplexing gain tradeoff (DMT) of the three protocols is determined and DMT-optimal distributed space-time code constructions are provided. The code construction is based on Cyclic Division Algebras. The codes constructed are sphere decodable and in some instances incur minimum possible delay. Included in our results is the perhaps surprising finding that the OAF and NAF protocols have identical DMT when the time durations of the broadcast and cooperative phases are optimally chosen to suit the respective protocol. Two variants of the NSDF protocol are considered: fixed-NSDF and variable-NSDF protocol. In the variable-NSDF protocol, the fraction of time occupied by the broadcast phase is allowed to vary with multiplexing gain. In the two-relay case, the variable-NSDF protocol is shown to improve on the DMT of the best previously-known static protocol for higher values of multiplexing gain. Our results also establish that the fixed-NSDF protocol has a better DMT than the NAF protocol for any number of relays.

In the wireless channel, cooperative communications allow one or many relays to assist the communication between the source and the destination. The aim of this thesis is the development of tools for the analysis of cooperative systems, when HARQ techniques are employed to provide cross-layer error protection. The first chapter of the thesis gives background information on network coding in cooperative relay networks, and introduces the motivation for this work. The second chapter is devoted to the analysis of the energetic-fair performance evaluations of FEC, ARQ-STBC and HARQ schemes at the MAC and IP layers. New analytical framework is derived and applied to a point-to-point network scenario. This framework allows to make energetic fair comparisons between the schemes with and without retransmissions. We determine under which channel conditions the cross-layer error protection is energetically more efficient than the simple channel coding. In the third chapter of this thesis we study the cooperative deterministic protocols. The protocols that we consider differ based on the behaviour of the relay(s), source(s), and destination. We consider two major types of cooperative protocols: decode-and forward (DCF), and demodulate-and-forward (DMF). Each of these protocols in its turn is analysed with and without combining mechanisms at the destination. We derive the soft decoders at the destination side for each respective case, and compare the performances of these protocols at the MAC layer. The following quality of service metrics are evaluated: frame error rate, delay, efficiency, goodput. The analysis is done evaluating the steady-state, using finite state Markov chains and a combinatorial approach. The analysis, however, becomes very complex as the number of transmissions and/or nodes in the network increases. The fourth chapter introduces a class of probabilistic communication protocols, where the devices retransmit with a given probability. We prove the existence of an equivalent class of protocols, with the same performances as the deterministic class. Using proofs of concept it is shown that the probabilistic protocol class allows for tractable steady-state analysis, even for many nodes in the network. Based on this, we then derive the QoS metrics and evalute them also by simulations. The derived performance evaluation metrics are then optimized by constraining the frame error rate, and trying to find the most optimal transmissions number and code rates which maximize the goodput. It is furthermore shown, that the equivalent protocol has larger optimal region than the deterministic one.

Abstract The goal of this thesis is to provide a unified concept of lossy-forwarding from the theoretical analysis to practical scheme design for the decode-and-forward-based multiple access relay channel (MARC) system. To improve the performance of MARC with the relay subject to resources or/and time constraints, the erroneous estimates output from simple detection schemes are used at the relay are forwarded and exploited. A correlation is then found between two sequences: one is the network-coded sequence sent from the relay, and the other is their corresponding exclusive-OR-ed information sequence. Several joint network-channel coding (JNCC) techniques are provided in which the correlation is utilized to update the log-likelihood ratio sequences during the iterative decoding process at the destination. As a result, the bit error rate (BER) and frame error rate (FER) are improved compared with those of MARC with select DF strategy (SDF-MARC). The MARC proposed above is referred to as erroneous estimates-exploiting MARC (e-MARC). To investigate the achieved FER performance of the e-MARC system, the outage probability for e-MARC with two source nodes is theoretically derived. We re-formulate the e-MARC system and identify its admissible rate region according to the Slepian-Wolf theorem with a helper. Then, the outage probability is obtained by a set of integral over the rate region with respect to the probability density functions of all the links' instantaneous signal-to-noise power ratios. It is found through simulations that, as one of the source nodes is far away from both the relay and destination, e-MARC is superior to SDF-MARC in terms of outage performance. Furthermore, a joint adaptive network-channel coding (JANCC) technique is then proposed to support e-MARC with more source nodes. A vector is constructed at the destination in JANCC to identify the indices of the incorrectly decoded source node(s), and re-transmitted to the relay for requesting additional redundancy. The relay performs network-coding only over the estimates specified by the vector upon receiving the request. Numerical results show that JANCC-aided e-MARC is superior to e-MARC in terms of FER and goodput efficiency. In addition, compared iterative decoding is performed at relay with SDF-MARC, the use of differential detection with JANCC-aided e-MARC significantly reduces the computational complexity and latency with only a small loss in the FER. / Tiivistelmä Tämän väitöskirjan tarkoituksena on tuottaa yhtenäinen kokonaisuus häviöllisestä lähetyksestä pura-ja-lähetä (DF) -pohjaisessa monikäyttörelejärjestelmässä (MARC) sekä teoreettisesta että käytännöllisestä näkökulmasta. Parantaakseen resurssi- tai aikarajoitetun MARC-järjestelmän suorituskykyä, vastaanotin hyödyntää riippuvuussuhdetta releen välittämien informaatiosekvenssien virheellisten estimaattien ja suoraan lähteestä tulevien informaatiosekvenssien välillä (e-MARC). Työssä ehdotetaan useita yhdistetyn verkko -ja kanavakoodauksen menetelmiä (JNCC), joissa log-uskottavuussuhdesekvenssit iteratiivisen purkamisprosessin aikana päivitetään hyödyntämällä sekvenssien riippuvuussuhdetta vastaanottimessa. Tämän tuloksena sekä bittivirhe- että kehysvirhesuhdetta saadaan parannettua verrattuna selektiiviseen pura-ja-lähetä menetelmää käyttävään MARC-strategiaan (SDF-MARC). Kehysvirheen suorituskyvyn tarkastelua varten työssä johdetaan teoreettinen epäkäytettävyyden todennäköisyys e-MARC-menetelmälle kahden lähettimen tapauksessa. Lisäksi e-MARC-menetelmälle määritetään tiedonsiirtonopeusalue Slepian-Wolf -teoreeman mukaisesti. Tämän jälkeen saadaan epäkäytettävyyden todennäköisyys kaikkien linkkien signaalikohinasuhteen todennäköisyystiheysfunktion integraalina tiedonsiirtonopeusalueen yli. Simulointitulokset osoittavat e-MARC-menetelmän paremman epäkäytettävyyden todennäköisyyden verrattuna SDF-MARC-menetelmään silloin kun yksi lähettimistä on kaukana sekä releestä että vastaanottimesta. Mahdollistaakseen useamman lähteen käytön e-MARC-menetelmässä, työssä ehdotetaan lisäksi adaptiivinen yhdistetyn verkko-ja kanavakoodauksen menetelmä (JANCC). Siinä vastaanotin määrittää väärin purettujen sekvenssien lähettimet ja ilmoittaa ne vektorimuodossa takaisin releelle pyytääkseen näiden lähettimien informaation uudelleenlähetystä. Tämän jälkeen rele suorittaa verkkokoodauksen vain tunnistusvektorin määrittämien informaatiosekvenssien estimaatteihin perustuen. Tulokset näyttävät, että JANCC-menetelmää käyttävä e-MARC saavuttaa paremman kehysvirheen ja hyödyllisen läpäisyn tehokkuuden verrattuna e-MARC-menetelmään.

The importance of cooperative relaying communication in substituting for, or complementing, multiantenna systems is described, and a brief literature review is presented. Amplify-and-forward (AF) and decode-and-forward (DF) relaying are investigated and compared for a dual-hop relay channel. The optimal strategy, source and relay optimal power allocation, and maximum cooperative gain are determined for the relay channel. It is shown that while DF relaying is preferable to AF relaying for strong source-relay links, AF relaying leads to more gain for strong source-destination or relay-destination links. Superimposed and selection AF relaying are investigated for multirelay, dual-hop relaying. Selection AF relaying is shown to be globally strictly outage suboptimal. A necessary condition for the selection AF outage optimality, and an upper bound on the probability of this optimality are obtained. A near-optimal power allocation scheme is derived for superimposed AF relaying. The maximum instantaneous rates, outage probabilities, and average capacities of multirelay, dual-hop relaying schemes are obtained for superimposed, selection, and orthogonal DF relaying, each with parallel channel cooperation (PCC) or repetition-based cooperation (RC). It is observed that the PCC over RC gain can be as much as 4 dB for the outage probabilities and 8.5 dB for the average capacities. Increasing the number of relays deteriorates the capacity performance of orthogonal relaying, but improves the performances of the other schemes. The application of rateless codes to DF relaying networks is studied by investigating three single-relay protocols, one of which is new, and three novel, low complexity multirelay protocols for dual-hop networks. The maximum rate and minimum energy per bit and per symbol are derived for the single-relay protocols under a peak power and an average power constraint. The long-term average rate and energy per bit, and relay-to-source usage ratio (RSUR), a new performance measure, are evaluated for the single-relay and multirelay protocols. The new single-relay protocol is the most energy efficient single-relay scheme in most cases. All the multirelay protocols exhibit near-optimal rate performances, but are vastly different in the RSUR. Several future research directions for fixed-rate and rateless coded cooperative systems, and frameworks for comparing these systems, are suggested. / Communications