Dissertations / Theses on the topic 'Two-way channels'
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1
Zhong, Peng. "Coding schemes for the two-way relay channels." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110709.
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In modern transmission networks, relay plays an important role for cooperative strategies.Several relaying strategies, such as decode-forward, compress-forward and amplify-forward,have been proposed for relay channels and networks. However, the capacity for the generalrelay channel and network is still unknown. In this thesis, we propose several relay schemesfor dierent relay models.In the rst part of the thesis, we propose novel partial decode-forward (PDF) schemesfor the two-way relay channel with direct link. Dierent from pure decode-forward, eachuser divides its message into two parts and the relay decodes only one part of each. Therelay then generates its codeword as a function of the two decoded parts and forwards tothe two users. We propose PDF schemes for both the full- and half-duplex modes. Analysisand simulation show that if for one user, the direct link is stronger than the user-to-relaylink, while for the other, the direct link is weaker, then PDF can achieve a rate regionstrictly larger than the time-shared region of pure decode-forward and direct transmissionfor both full- and half-duplex modes.The second part of the thesis is based on noisy network coding, which is recently proposedfor the general multi-source network by Lim, Kim, El Gamal and Chung. Thisscheme builds on compress-forward (CF) relaying but involves three new ideas, namely noWyner-Ziv binning, relaxed simultaneous decoding and message repetition. In this part,using the one-way and two-way relay channel as the underlining example, we analyze theimpact of each of these ideas on the achievable rate region of relay networks.In the third part of the thesis, we propose two coding schemes combining decode-forward(DF) and noisy network coding (NNC) with dierent avors. The rst is a combined DFNNCscheme for the one-way relay channel which includes both DF and NNC as specialcases by performing rate splitting, partial block Markov encoding and NNC. The secondcombines two dierent DF strategies and layered NNC for the two-way relay channel.Analysis and simulation show that both proposed schemes supersede each individual schemeand take full advantage of both DF and NNC.Dans les reseaux de transmission modernes, les relais jouent un r^ole important dans lesstrategies cooperatives. Plusieurs strategies de relai, telles que decode-forward, compressforwardet amplify-forward, ont ete proposees pour les canaux et reseaux a relais. Cependant,la capacite du canal a relai general et de tels reseaux reste toujours inconnue. Danscette these, nous proposons plusieurs strategies de relai pour dierents modeles.Dans un premier temps, nous proposons de nouvelles strategies de decode-forward partiel(PDF) pour le canal a relai bidirectionnel avec lien direct. A la dierence du decodeforwardclassique, chaque utilisateur divise son message en deux parties, mais le relai nedecode que l'une d'entre elles pour chacun. Le relai genere alors un mot de code en fonctionde ces deux parties decodees et les transmet aux deux utilisateurs. Nous proposonsune stratgie PDF a la fois pour les liaisons half- et full-duplex. Comme le montrent lesanalyses et simulations realisees, si, pour l'un des utilisateurs, le lien direct est meilleur quele lien utilisateur-relai alors que, pour l'autre utilisateur, le lien direct est plus faible, dansce cas, la strategie PDF permet d'accro^tre strictement la region des debits atteignablespar rapport a la region atteinte par le partage de temps avec la strategie decode-forwardclassique et la transmission directe, a la fois pour les liaisons half- et full-duplex.La deuxieme partie de cette these s'interesse au codage de reseau avec bruit, qui a eteaborde recemment pour les reseaux multi-sources generiques par Lim, Kim, El Gamal etChung. Cette strategie se base sur le relayage par compress-forward (CF), mais utilise troisnouvelles idees, a savoir le binning de Wyner-Ziv, le decodage simultane moins contraignantet la repetition de message. Dans cette partie, nous prenons pour exemple les canaux arelai mono- et bidirectionnels, et nous analysons l'impact de chacune de ces idees sur laregion des debits atteignables pour les reseaux a relais.Dans la troisieme partie de cette these, nous proposons deux strategies de codage quicombinent le decode-forward (DF) et le codage de reseau avec bruit (NNC), avec dierentesnuances. La premiere est une strategie combinee DF-NNC pour le canal a relai monodirectionnel,pour laquelle DF et NNC representent des cas particuliers par partage de debit,de m^eme que lencodage partiel en bloc de Markov et NNC. La deuxieme strategie combinedeux strategies DF dierentes au codage NNC en couches pour le canal a relai bidirectionnel.Les analyses et les simulations montrent que les deux strategies proposees remplacentchaque strategie individuelle et prennent pleinement avantage des strategies DF et NNC.
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Li, Lun. "Blind detection with unique identification in two-way relay channels." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/5183.
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This thesis considers a two-way relay system whereby two nodes exchange information
via a relay node. Amplify-and-forward (AF) is applied as a relaying strategy.The channel
information is not available at both receivers. The generalized likelihood ratio test (GLRT)
and least squares error (LSE) detectors are derived in order to achieve blind unique recovery
of the transmitted symbol. It is also proven that full diversity can be achieved. A constellation
selection algorithm is designed to optimize the symbol error rate (SER) performance.
This thesis also analyzes both theoretical procedures and simulation results of an existing differential
detection scheme for two-way relay channels. Monte Carlo simulations demonstrate
the performance of the proposed algorithm.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science.
3
Heindlmaier, Michael [Verfasser]. "Network Coding for Two-Way Relay Channels and Broadcast Erasure Channels with Feedback / Michael Heindlmaier." München : Verlag Dr. Hut, 2015. http://d-nb.info/1080754334/34.
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Olausson, Nathalie. "Kommunikationsverksamhet i ett föränderligt samhälle : En studie om hur Gällivare kommun bör kommunicera med sin befolkning under samhällsomvandlingen." Thesis, Umeå universitet, Institutionen för kultur- och medievetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-67934.
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The purpose of this study is to analyze which communication strategies andinformation- and communication channels that Gällivare municipality should useunder the urban transformation to communicate with the citizens. The studyconcentrates on the age-groups 16 – 24, 25 – 44, 45 – 64 and people that are 65 yearsand older. This selection has been made as a segmentation of the citizens and is oneof the essay questions which refers to study the channels that each age-groups prefer.The study is a quantitative one and is based on a questionnaire survey directed to thecitizens and it’s 85 people who participated. The result of the survey have beenanalyzed with theories like Grunigs two-way symmetrical model, theories forcommunication in public sector and theories for the most common media channels asface-to-face communication and internet.The analysis shows that Gällivare municipality should use a communication strategythat is intended to surprise the citizens, becase the survey showed that there’s a fairlylow commitment for questions of the urban transformation. The strategy is alsouseful when the survey showed that the citizens believe that the promises in theinformation of Gällivare municipality aren’t kept, which could have resulted that theybecame passive and now they have to wake up from that state of mind. It also showsthat the age-group 16-24 years concider internet as a channel for information andsocial media as the most popular communication channel. Rest of the age-gropusprefer printed information. But the opinion for the communication channels differsbetween the group 25 – 44 years and the two others. The first mentioned considers emailas the channel they want to communicate with the municipality unlike the agegroups45 – 64 and 65 and older that prefers face-to-face communication.
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Chen, H. "Beamforming optimization for two-way relay channel." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1421150/.
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In this thesis, we focus on the optimization of the two-way relay channel (TWRC), which can double the data rate of communications comparing to the traditional one-way relay channel (OWRC). Because of the broadcasting nature of wireless transmissions, secure transmission is an appealing research topic. We take secrecy rate consideration into the optimization of the TWRC. Overall we provide near-optimal solutions for the secrecy rate maximization problems of the TWRC with imperfect channel state information (ICSI). A much lower complexity optimal SOCP solution is provided for SNR balancing of the TWRC without secrecy consideration. We first look at a flat fading TWRC network model with a multiple-input multiple-output (MIMO) relay where perfect channel state information (CSI) is assumed available. We then formulate an optimization problem, with the objective to minimize the relay’s power usage under the constraints that the signal-to-noise ratio (SNR) of the two transceivers should exceed a preset threshold. A low-complexity optimal beamforming solution is provided to this optimization problem by reformulating it in the form of second-order cone programming (SOCP). Later in the thesis, we consider the presence of an eavesdropper and address the beamforming optimization for minimizing the relay’s power with the constraints of the secrecy rates of the two transceivers. A semi-definite programming (SDP) based searching algorithm is proposed to find a near-optimal solution. For each search of the proposed approach, the previous non-convex optimization problem is transferred into an SDP problem, which can guarantee the optimality of the beamforming matrix. Afterwards, more realistic imperfect CSI (ICSI) situations are considered for the TWRC network models. As ICSI completely changes the structure and the property of the optimization problems, we reformulate the optimization problems into two scenarios. For the first case, we consider that the relay is an untrusted eavesdropper and in this case an SDP solution is provided to maximize the joint-decoding sum-secrecy rate. For the second case, we investigate the robust beamforming problems where the relay is trusted but there is an external eavesdropper, another SDP solution is provided to maximize the sum-secrecy rate.
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Reyneke, Annerie. "Expectations on the use of Facebook for employee engagement / Annerie Reyneke." Thesis, North-West University, 2013. http://hdl.handle.net/10394/10007.
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In order to engage employees effectively, organisations need to practice two-way
communication within a symmetrical worldview. This will encourage employees to feel valued,
to participate in decision-making and contribute to obtaining organisational goals. Practising
two-way communication will help to build stronger relationships between employees and
managers, leading to increased employee engagement. Thus, the better the communication
between managers and employees, the more engaged employees will be. Furthermore, the
selection of communication channels can impact on the success of the message that is sent.
Research has shown that if the inappropriate communication channel is selected when
communicating with employees, the message might not be effectively received and
understood. New technology, specifically Facebook can be introduced to provide an open and
transparent channel for communication. Facebook can also facilitate two-way communication,
which can lead to increased employee engagement.
The literature study conducted informed the interview schedules that were developed and used
to conduct semi-structured interviews with managers and focus group interviews with
employees within two organisations in the South African financial sector. This was done in
order to understand their expectations regarding the use of Facebook as an internal
communication channel to enhance employee engagement.
In terms of the conclusions derived from the empirical research, it seems evident that
Facebook could be used as an additional internal communication channel to enhance
employee engagement. Trust remains a very important factor in that managers should trust
employees to use the channel in an ethical manner and employees should trust the
organisation and its managers that they may voice their opinion freely, without the fear of
victimisation. Facebook can be used to promote engagement on a social level to build
relationships inside the organisation.
However, managers and employees can together create a contract of understanding that will
form the outline for a policy that will govern the use of Facebook. The parties involved can then
negotiate the terms of this contract of understanding to ensure that all expectations regarding
the use Facebook are met.MA (Communication Studies), North-West University, Potchefstroom Campus, 2013
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Leijonklo, Lovisa. "Lägg märke till varumärket : En kvantitativ undersökning kring hur varumärket Hollister jobbar med kommunikation för att stärka sitt varumärke." Thesis, Umeå universitet, Institutionen för kultur- och medievetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-85118.
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The purpose of the case study is to research whether the brand Hollister can establish themselves to their target audience working with communication. To achieve the goal with the study, the following theories has been applied: brand building, visual communication, two-way symmetrical communication and communication channels. The study was conducted by a quantitative online questionnaire survey. The online survey was aimed at teenagers aged 15-18 years old living in Täby or Umeå where one question was "What difference can be discerned between Täby, where there is a shop, and Umeå where there is no shop". The material was collected during a period of eight days between december 11th to december 19th 2013. The online survey was answered by 90 units which means a response rate of 90 percent. The results of the study showed that it differed somewhat between the cities and above all it showed that the units from Täby had more knowledge about the brand's visual identity, and visited the store to a larger extent. The analysis also showed that branding is an important part to reach out and influence Hollister’s target audience where the work of visual communication is vital.Syftet med studien är att undersöka om varumärket Hollister kan etablera sig hos sin målgrupp med hjälp av kommunikation. För att uppnå syftet har följande teorier tillämpats: varumärkesbyggande, visuell kommunikation, tvåvägs-symmetrisk kommunikation samt kommunikationskanaler. Studien har genomförts genom en kvantitativ enkätundersökning på webben. Webbenkäten riktade sig till tonåringar i åldern 15-18 år som bor i Täby eller Umeå då bland annat en frågeställning har varit ”Vilken skillnad går att utläsa mellan Täby, där det finns en butik, respektive Umeå där det inte finns någon butik”. Materialet samlades in under en period på åtta dagar mellan 11-19 december 2013. Webbenkäten svarades av 90 enheter vilket innebär en svarsfrekvens på 90 procent. Resultatet av studien visade att det skiljde en del mellan städerna framförallt går det att utläsa att enheterna från Täby hade mer kännedom kring varumärkets visuella identitet samt besökt butiken i större utsträckning. Analysen visade även att varumärkesbyggande är en viktig del för att nå ut och påverka sin målgrupp och bland annat att arbetet med den visuella kommunikationen är betydelsefull.
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Schedler, Stephan [Verfasser]. "Generalized Frequency Division Multiplexing in the Two-Way-Relay Channel / Stephan Schedler." Aachen : Shaker, 2016. http://d-nb.info/1120863880/34.
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Xu, Ning. "Physical-Layer Network Coding for MIMO Systems." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc68065/.
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The future wireless communication systems are required to meet the growing demands of reliability, bandwidth capacity, and mobility. However, as corruptions such as fading effects, thermal noise, are present in the channel, the occurrence of errors is unavoidable. Motivated by this, the work in this dissertation attempts to improve the system performance by way of exploiting schemes which statistically reduce the error rate, and in turn boost the system throughput. The network can be studied using a simplified model, the two-way relay channel, where two parties exchange messages via the assistance of a relay in between. In such scenarios, this dissertation performs theoretical analysis of the system, and derives closed-form and upper bound expressions of the error probability. These theoretical measurements are potentially helpful references for the practical system design. Additionally, several novel transmission methods including block relaying, permutation modulations for the physical-layer network coding, are proposed and discussed. Numerical simulation results are presented to support the validity of the conclusions.
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Abdallah, Saeed. "Spectrally-efficient approaches to channel estimation for amplify-and-forward two-way relay networks." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119426.
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Relay networks constitute one of the key technologies that are being developed for use in next generation wireless systems. In relay networks, the communication between the source and the destination is aided by dedicated nodes (relays) that convey the source's message to the destination. The use of relays improves the coverage, capacity and reliability in the network. Two-way relay networks (TWRNs) have recently been proposed to support bidirectional communication and have attracted the attention of many researchers because of their high spectral efficiency. In particular, TWRNs employing the amplify-and-forward (AF) protocol are appealing because of the minimal processing requirements at the relay. Effective operation of AF TWRNs requires accurate channel state information for self-interference cancellation and coherent decoding. The majority of works on channel estimation for AF TWRNs follow the training-based approach, which requires the transmission of pilots known to both terminals. The training-based approach consumes much needed bandwidth resources, which undermines the spectral efficiency of TWRNs. Blind channel estimation avoids the costly training burden by relying only on the received data samples. Another alternative approach is semi-blind estimation, a hybrid of blind and training-based approaches. The main objective of this thesis is to investigate blind and semi-blind channel estimation for AF TWRNs as a means for achieving substantially better tradeoffs between accuracy and spectral efficiency than possible using the training-based approach. In the first part of the thesis, we consider blind channel estimation for flat-fading channel conditions. Using the deterministic maximum likelihood (DML) approach, we propose new algorithms for blind channel estimation in AF TWRNs that employ constant-modulus signalling. Assuming M-PSK modulation, we prove that the proposed estimators are consistent and approach the true channel with high probability at high SNR. Using simulations, we show that the DML estimator offers a superior tradeoff between accuracy and spectral efficiency than the pilot-based LS estimator. Still within the context of flat-fading channels, the second part of the thesis focuses on semi-blind channel estimation. We derive the exact CRB for semi-blind channel estimation in AF TWRNs that employ square QAM. The derived bound is based on the true likelihood function that incorporates the exact statistics of the transmitted data symbols. Using the new bound, we show that the training overhead can be significantly reduced by employing semi-blind estimation. To demonstrate the achievability of these gains, we derive an expectation maximization (EM)-based semi-blind algorithm that performs very closely to the derived CRB. In the last part of the thesis, we consider semi-blind channel estimation for OFDM-based TWRNs operating in frequency selective channel conditions. To assist in the estimation of the individual channels, superimposed training is adopted at the relay. Our proposed semi-blind estimation algorithm is based on the Gaussian ML approach. We design the pilot vectors of the terminals and relay to optimize estimation performance. Our simulations show that the proposed method provides significant improvements in estimation accuracy.Les réseaux à relais constituent l'une des technologies clé de la prochaine génération des systèmes de communication sans fil. Dans les réseaux à relais, la communication entre une source et une destination est assistée par des noeuds dédiés (ou relais) qui relayent lemessage de la source jusqu'à la destination. L'utilisation de relais améliore la couverture, la capacité et la fiabilité des réseaux. Les réseaux à relais bidirectionnels (two-way relay networks ou TWRNs) ont été récemment proposés et ont suscité l'intérêt de nombreux chercheurs à cause de leur grande efficacité spectrale. En particulier, les TWRNs utilisant le protocole de relayage amplifier-et-transférer (amplify-and-forward ou AF) sont attrayants à cause de leurs faibles exigences de traitement aux relais. Le bon fonctionnent des AF TWRNs nécessite une étape d'estimation précise du canal pour la suppression d'auto-interférence et pour le décodage cohérent. La plupart des travaux sur l'estimation du canal pour les AF TWRNs suivent l'approche basée sur l'entrainement, ce qui nécessite la transmission de pilotes connus des deux terminaux .Cette approche consomme de précieuses ressources de communication afin de transmettre les pilotes, ce qui compromet l'efficacité spectrale des TWRNs. L'estimation aveugle évite ce fardeau en se fiant seulement sur les données reçues. Une autre option est l'estimation semi-aveugle, une approche hybride de l'approche aveugle et de celle basée sur l'entrainement. L'objectif de cette thèse est d'examiner l'estimation aveugle et semi-aveugle du canal pour les AF TWRNs afin d'obtenir un meilleur compromi entre l'efficacité spectrale et la précision que que celui offert par l'approche basée sur l'entrainement. Dans la première partie de cette thèse, nous considérons l'estimation aveugle du canal pour des conditions d'évanouissement plat. Employant le principe du maximum de vraisemblance déterminée (deterministic maximum likelihood ou DML), nous proposons de nouveaux algorithmes pour l'estimation et la détection aveugle et conjointe du canal pour les AF TWRNs qui utilisent une signalisation à module constant. Supposant une modulation M-PSK, nous prouvons que les estimateurs proposés sont consistants et se rapprochent du vrai canal avec une grande probabilité lorsque le rapport signal sur bruit est élevé. En utilisant des simulations, nous montrons que le DML offre un meilleur compromis entre l'efficacité spectrale et la précision que l'estimateur LS employant des pilotes. Toujours en rapport avec l'évanouissement plat, la deuxième partie de cette thèse porte sur l'estimation semi-aveugle du canal. Nous établissons la CRB exacte pour l'estimation semi-aveugle du canal pour les AF TWRNs qui utilisent une constellation QAM carrée. Cette borne est basée sur la vraie fonction de vraisemblance qui tient compte des statistiques exactes des symboles de données transmis. En utilisant cette nouvelle borne, nous montrons que la complexité attribuable à l'entrainement peut être considérablement réduite en employant un estimation semi-aveugle. Afin de montrer que ces gains sont réalisables, nous concevons un algorithme semi-aveugle basé sur la méthode d'espérance maximisation (EM), et nous montrons que cet algorithme se rapproche tout près de la CRB. Dans la dernière partie de cette thèse, nous considérons l'estimation semi-aveugle pour les TWRNs qui sont basés sur l'OFDM et qui opèrent dans un environnement sélectif en fréquence. Pour faciliter l'estimation des canaux individuels, un entrainement superposé est adopté aux relais. L'algorithme semi-aveugle que nous proposons est basé sur le principe ML gaussien .Nous concevons des séquences pilotes pour les terminaux et pour les relais de façon à optimiser la performance de l'estimation. Nos simulations révèlent que la méthode proposée fournit une nette amélioration de la précision de l'estimation.
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Richter, Johannes, Elke Franz, Sabrina Engelmann, Stefan Pfennig, and Eduard A. Jorswieck. "Physical Layer Security vs. Network Layer Secrecy: Who Wins on the Untrusted Two-Way Relay Channel?" Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-145086.
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We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.
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Richter, Johannes, Elke Franz, Sabrina Engelmann, Stefan Pfennig, and Eduard A. Jorswieck. "Physical Layer Security vs. Network Layer Secrecy: Who Wins on the Untrusted Two-Way Relay Channel?" Technische Universität Dresden, 2013. https://tud.qucosa.de/id/qucosa%3A28133.
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We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.
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Pierrot, Alexandre Jean Louis J. "Coding techniques for multi-user physical layer security." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53836.
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The fast development of wireless networks, which are intrinsically exposed to eavesdropping, has created a growing concern for confidentiality. While classical cryptographic schemes require a key provided by the end-user, physical-layer security leverages the randomness of the physical communication medium as a source of secrecy. The main benefit of physical-layer security techniques is their relatively low cost and their ability to combine with any existing security mechanisms. This dissertation provides an analysis including the theoretical study of the two-way wiretap channel to obtain a better insight into how to design coding mechanisms, practical tests with experimental systems, and the design of actual codes. From a theoretical standpoint, the study confirms the benefits of combining several multi-user coding techniques including cooperative jamming, coded cooperative jamming and secret key generation. For these different mechanisms, the trade-off between reliability, secrecy and communication rate is clarified under a stringent strong secrecy metric. Regarding the design of practical codes, spatially coupled LDPC codes, which were originally designed for reliability, are modified to develop a coded cooperative jamming code. Finally, a proof-of-principle practical wireless system is provided to show how to implement a secret key generation system on experimental programmable radios. This testbed is then used to assess the realistic performance of such systems in terms of reliability, secrecy and rate.
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Smirani, Sinda. "Étude du codage réseau au niveau de la couche physique pour les canaux bidirectionnels à relais." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00962333.
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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.
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姍, 路., and Shan Lu. "Coding and decoding for multiuser communication systems." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863897/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863897/?lang=0.
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本論文は、多端子通信路に対するマルチユーザ符号化および復号の研究成果をまとめたものである。多重接続加算通信路による情報伝送において、複数ユーザの稼働状態を識別するための誤り訂正可能なシグネチャ符号の構成を論ず,全伝送率の高いシグネチャ符号の一般的な構成法を解明する.双方向中継通信路では、2ユーザターボ符号に対する復号の演算量を低減させる復号法を提案する。加法性白色ガウス雑音環境下では復号性能を劣化することなく、レイリーフェージング環境下では僅かな劣化にとどめながら、復号の演算量を約半分程度に低減することができる.Coding and decoding for multiuser communication systems are investigated. For MAAC, we propose a coding scheme of (k + 1)-ary error-correcting signature codes. We give binary and non-binary signature codes. They are the best error-correcting signature codes for MAAC, in the sense that they have highest sum rates known. For TWRC, we propose a low-complexity two-user turbo decoding scheme when turbo codes are applied in two users. The approximate decoding algorithm preserves low decoding complexity over the Gaussian TWRC, without much performance degradation.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Abadi, Tarla. "Design and performance analysis of cooperative relay systems." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/design-and-performance-analysis-of-cooperative-relay-systems(8edce5bc-1518-4df2-aa49-36bf5386036a).html.
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Cooperative relay systems have emerged as promising techniques to boost the performance of wireless systems. Recent studies have confirmed that interferences, co-channel interferences (CCIs) and self-interferences, have a huge impact on cooperative relay systems and can cause significant performance degradation. Two problems were observed in this research. Firstly, previous studies on performance analysis of Amplify-and-Forward (AF) relay systems in presence of CCIs have only focused on a specific interference channel model. However, in practical design scenarios, such an assumption is not a realistic proposition. Secondly, analyses of overheads introduced by a time-based relay selection protocol in distributed cooperative systems have been based on an over-pessimistic assumption where all packets involved in a collision are destroyed. Nevertheless, collisions due to the protocol overheads cause the system performance to be degraded but this does not mean that the failure of end-to-end transmission certainly occurs. The thesis aims to analyse the performance of practical cooperative relay systems in the presence of CCIs and self-interferences, by developing exact mathematical methods. A new unified mathematical method for AF relay systems in presence of a random number of arbitrary non-identical CCIs was developed. The obtained new approach derived in terms of a moment generating function of the aggregate interferences' power led to the derivation of new explicit expressions. The new results greatly simplify evaluation of average error rates over diverse practical interference scenarios. Moreover, a new exact mathematical analysis for distributed cooperative relay systems employing a time-based relay selection protocol based on an accurate interference model was presented. This approach led to the derivation of new exact expressions for the spectral efficiency which accounts for both self-interferences and the protocol overheads as well as for different fading scenarios and arbitrary relay locations. This approach provided several advantages over direct approaches, one of which is that it significantly simplified averaging-out the joint random variables involved.
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Sandes, Fábio Shimabukuro. "Um estudo empírico sobre o uso do boca a boca gerado na internet como comunicação com o cliente." reponame:Repositório Institucional do FGV, 2010. http://hdl.handle.net/10438/4744.
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Previous issue date: 2010-02-22T00:00:00ZO impacto do boca a boca na Imagem da Marca e no julgamento de produtos (bens e serviços) tem sido estudado há tempos na disciplina de comportamento do consumidor. Com o crescimento da internet como mídia social e meio de comunicação entre consumidores e empresas, o boca a boca ganhou força junto a profissionais e pesquisadores de Marketing. Uma revisão da literatura permitiu traçar um paralelo entre o boca a boca tradicional e o eletrônico. É preciso compreender cientificamente a influência do boca a boca eletrônico no comportamento do consumidor. Para isto, foram realizados dois estudos nesta dissertação, sendo o primeiro um estudo exploratório a partir da realização de entrevistas e aplicação de questionários a consumidores, profissionais de Marketing e especialistas do assunto com o intuito de levantar percepções gerais sobre o tema. Para avaliar estatisticamente as hipóteses propostas nesta dissertação, o segundo estudo foi a realização de um experimento com 168 estudantes, contando com cinco cenários e três tipos de produtos (Vestuário, Cosméticos e Lojas Online). A variável independente foi o Comentário Postado pelo consumidor. Duas foram as variáveis dependentes: Imagem da Marca e Intenção de Compra dela. Para a mensuração da Imagem da Marca se utilizou a escala de Personalidade de Marca de Aaker (1997). No tocante à Intenção de Compra, um concurso foi elaborado para os sujeitos. No início e no final da coleta de dados, os participantes escolhiam as empresas das quais ganhariam um prêmio (vale compra), caso fossem os vencedores. Mediu-se a Intenção de Compra em função da escolha dos consumidores antes e depois do estímulo, sendo comparados, ainda, os resultados dos diferentes cenários. Constatou-se que os comentários negativos e positivos que os consumidores postam na internet têm um impacto significante na Imagem da Marca para outros consumidores nos produtos Vestuário e Loja Online. Mas não foram percebidos impactos destes comentários na Imagem da Marca no produto Cosmético e na Intenção de Compra dos outros consumidores nos três tipos de produtos testados. O Gerenciamento dos Comentários negativos (resposta da empresa a comentário postado pelo consumidor) apresentou uma redução no impacto do comentário na Imagem da Marca para os outros consumidores no produto Loja Online. Contudo, os tons alinhados com Foco Regulatório do consumidor nas respostas das empresas não provocaram diferenças significativas, contra indicando essa concepção teórica como meio de aprimorar os resultados do Gerenciamento dos Comentários. Várias implicações científicas e profissionais interessantes decorrem da pesquisa. Para o praticante, se viu que a internet 2.0 é uma mídia a ser considerada no esforço de comunicação da empresa e que ela deve ser considerada como um canal de comunicação bidirecional.
The impact of Word of Mouth Communication on Brand Image and the evaluation of products (goods and services) has been studied for some time in the discipline of consumer behavior. With the growth of the Internet as a social media and as a means of communication between consumers and enterprises, Word of Mouth has gained strength with Marketing professionals and researchers. A review of the literature draws a parallel between traditional Word of Mouth and its electronic version. It is essential to understand scientifically the influence of Electronic Word of Mouth on consumer behavior. In order to do this, two main studies were made: the first one was an exploratory stage conducted with interviews and questionnaires applied to consumers, marketers, and experts on the subject in order to raise general perceptions on the issue. The second study aims to evaluate statistically the hypotheses proposed in this work and involves an experiment applied to 168 students, considering five scenarios and three types of products (clothing, cosmetics and Online Stores). The independent variable was the Comment Posted by the consumer on the internet. Two were the dependent variables: Brand Image and Purchase Intention. To measure Brand Image, the scale "The Brand Personality" by Aaker (1997) was used. To measure Purchase Intention subjects participated in a contest where they chose, at the beginning and end of data collection, the companies from which they would gain a gift certificate, if they won the contest. Purchase Intention was measured depending on the choice of consumers before and after the stimulus, and compared also the results of different scenarios. It was found that the positive and negative comments that consumers posted on the internet have a significant impact on Brand Image for other consumers of products in Clothing and Online stores. However, there was no perceived impact based on these comments regarding Cosmetic products. No impact was found on other consumers' Purchase Intention. Management of Negative Comments (company's response to comments posted by the consumer on the internet) decreased the negative impact of comments on other consumer's Brand Image on product Online Store and the use of Regulatory Focus Theory on companies' responses did not cause significant differences, counter indicating this theoretical concept as a mean to improve the results of managing the comments posted by the consumer on the internet. Several implications of scientific and professional interest arise from this research. For a Marketing professional, it is evident that internet 2.0 should be considered in the media plan of a company and that it should be treated as a two-way communication channel with consumers.
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"Exploiting channel symmetry in two-way channels." Thesis, 2010. http://hdl.handle.net/1911/61968.
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Wireless communication is frequently employed for the bi-directional exchange of information between devices with disparate capabilities. Mobile devices such as cellular phones and laptops are subject to stringent size weight and power constraints relative to the base stations or access points they communicate with. Asymmetry of constraints results in asymmetry of the cost of computation. This disparity in cost motivates efforts to shift signal processing such as channel estimation and equalization from cost sensitive devices to those with more relaxed constraints. In this work we develop a two-way training channel estimation and precoding scheme that shifts all the computation involved in dealing with multiplicative channel gain as well as frequency selective channels to the base station. This work demonstrates the first tractable implementation of a precoding based transceiver scheme of this class on the Rice University Wireless Open Access Research Platform (WARP).
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Steger, Christopher B. "Cooperative communication over two-way channels." Thesis, 2008. http://hdl.handle.net/1911/22269.
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In this thesis, we define and analyze communication scenarios in which the source and destination cooperate across noncoherent two-way fading channels. As in practical communication systems, we constrain the bandwidth and power resources available at both nodes. By constraining resources, we automatically produce situations in which neither the source nor the destination knows the fading state perfectly, and the nodes are unable to perfectly share knowledge with one another. Thus, not only is the channel state information imperfect, but the ability to cooperate in a coordinated fashion is also impaired. As a result, performance predictions based on perfect channel state information and perfect coordination can prove highly unrealistic. However, we have discovered that even in the presence of imperfect channel state information and imprecise coordination, cooperative communication over two-way channels offers significant performance gains over comparable one-way systems, and we have developed novel schemes to leverage cooperative gains in the presence of uncertainty.
In the first part of this work, we analyze the reliability of a system that uses channel inversion power control to combat the effects of fading. We demonstrate that a simplistic approach to training leaves the system crippled by channel estimation errors. As an alternative, we propose a novel two-way training scheme that limits the impact of estimation error and provides the best known performance of any system subjected to full resource accounting. We then show that the benefits of two-way training extend to systems with multiple transmit antennas and two-way systems in which the data flow is bidirectional.
In the second part, we employ a more general system model and study the precise amount of mutual information lost to uncertain channel state information at the destination. Our results illuminate the relationship between the loss of mutual information and the entropy of the channel. We also capture the effect of coherence time and the degree to which data-aided estimation can mitigate channel estimation errors. We then apply our results to quantify the performance of a number of practical systems and demonstrate the effectiveness of two-way cooperation in realistic scenarios.
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"Fundamental Limits of Two-pair Two-Way Relay Channels." 2016. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1292194.
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In this thesis, we study the fundamental limits of the multipair two-way relay channel (TWRC) system, consisting of one relay and multiple pairs of users. Each user only exchanges information with the other user of the same pair via help of the relay. The information exchange consists of two phases. In the uplink phase, all the users simultaneously transmit signals to the relay; in the downlink phase, the relay broadcasts the processed signals to all the users. For simplicity and concreteness, we focuses on the multipair TWRC system with two pairs; the general principles expounded here can be extended to the case of more pairs.The first part of this thesis investigates the downlink transmission phase. For the downlink phase, each user is only interested in its partner’s message and treats the message for the other pair as interference. Suppose that the relay encodes messages for user pairs sequentially, i.e., message for one pair followed by message for the other pair. Then, the first message becomes noncausal interference for the remaining message, i.e., the encoder knows such interference prior to the encoding of the remaining message. Hence, the downlink transmission can be modeled as a broadcast channel with noncausal interference at the transmitter (i.e., the relay) and side information at the receivers (i.e., the users). We first obtain an achievable rate region of this system by extending Gelfand and Pinsker’s (GP’s) random binning method. We then apply the result to Gaussian scalar and vector channels, and consider the design of the auxiliary random variable used in the GP’s approach. Asymptotic analysis shows that our scheme is asymptotically capacityachieving at high signal-to-noise ratio (SNR) for both scalar and vector channels. We further investigate the system optimization in the finite SNR regime. Numerical results
show that our scheme can achieve a sum-rate close to the cut-set bound over a wide SNR range, and significantly outperforms the schemes that do not exploit the knowledge of noncausal interference at the transmitter.
The second part of this thesis studies the capacity of the Gaussian two-pair TWRC system, where each node is equipped with single antenna. For the Gaussian TWRC, the noises at the relay and the user nodes are Gaussian and independent of each other. Our main contribution is a message-reassembling strategy to decouple the coding design for the uplink and downlink transmissions. This strategy provides flexibility to fully exploit the channel randomness of both uplink and downlink. For the uplink transmission, each user transmits a superposition of Gaussian random codeword and nested lattice codeword, and the relay employs successive interference cancellation to decode signals. For the downlink transmission, the relay first reassembles and re-encodes messages, and then transmits a superposition of the resulting codewords. Finally, each user decodes the other user’s message of the same pair with the help of self-information. The analytical results show that the capacity region is achievable to within 1/2 bit per user.
The third part of this thesis extends our studies to the Gaussian two-pair multiinput multi-output (MIMO) TWRC system, where each node is equipped with multiple antennas. In the uplink phase, the relay’s received signal space is divided into two subspaces for each pair: in one subspace, the signals of the two users are near-parallel, and physical-layer network coding (PNC) decoding is applied to retrieve network-coded messages; in the other subspace, the two user signals are near-orthogonal, and complete decoding (CD) is applied to retrieve individual user messages. In the downlink phase, the relay’s transmit signal space is split into orthogonal subspaces for each pair, and in each subspace a common message is broadcasted to the two users. Our main contribution is to establish a critical link between the transmission scheme and the concept of principal angle in linear algebra. In particular, principal angle provides a way to quantify the degree of orthogonality between the user signals and helps determining how to partition the relay’s received signal space into PNC decoding subspace and CD decoding subspace. Building on that, we provide a near-optimal design of user/relay precoders for both uplink and downlink phases to maximize the asymptotic sum-rate of our scheme at high signal-tonoise ratio (SNR). The analysis and numerical results indicate that our scheme performs close to the cut-set bound and significantly outperforms existing schemes in the literature.
Xin, Haiyang.
Thesis Ph.D. Chinese University of Hong Kong 2016.
Includes bibliographical references (leaves ).
Abstracts also in Chinese.
Title from PDF title page (viewed on …).
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"Transmission Strategies for Two-Way Relay Channels." Doctoral diss., 2015. http://hdl.handle.net/2286/R.I.36464.
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abstract: The recent proposal of two-way relaying has attracted much attention due to its promising features for many practical scenarios. Hereby, two users communicate simultaneously in both directions to exchange their messages with the help of a relay node. This doctoral study investigates various aspects of two-way relaying. Specifically, the issue of asynchronism, lack of channel knowledge, transmission of correlated sources and multi-way relaying techniques involving multiple users are explored.
With the motivation of developing enabling techniques for two-way relay (TWR) channels experiencing excessive synchronization errors, two conceptually-different schemes are proposed to accommodate any relative misalignment between the signals received at any node. By designing a practical transmission/detection mechanism based on orthogonal frequency division multiplexing (OFDM), the proposed schemes perform significantly better than existing competing solutions. In a related direction, differential modulation is implemented for asynchronous TWR systems that lack the channel state information (CSI) knowledge. The challenge in this problem compared to the conventional point-to-point counterpart arises not only from the asynchrony but also from the existence of an interfering signal. Extensive numerical examples, supported by analytical work, are given to demonstrate the advantages of the proposed schemes.
Other important issues considered in this dissertation are related to the extension of the two-way relaying scheme to the multiple-user case, known as the multi-way relaying. First, a distributed source coding solution based on Slepian-Wolf coding is proposed to compress correlated messages close to the information theoretical limits in the context of multi-way relay (MWR) channels. Specifically, the syndrome approach based on low-density parity-check (LDPC) codes is implemented. A number of relaying strategies are considered for this problem offering a tradeoff between performance and complexity. The proposed solutions have shown significant improvements compared to the existing ones in terms of the achievable compression rates. On a different front, a novel approach to channel coding is proposed for the MWR channel based on the implementation of nested codes in a distributed manner. This approach ensures that each node decodes the messages of the other users without requiring complex operations at the relay, and at the same time, providing substantial benefits compared to the traditional routing solution.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2015
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Rao, Yan-Ciao, and 饒硯喬. "A Study on Efficient Detection Techniques for Two-Way Relaying Channels." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/98308966448401301483.
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碩士國立暨南國際大學
電機工程學系
102
Two way relaying cooperative communications have recently been proved for improving the spectral efficiency successfully. Conventionally, minimum mean-squared error (MMSE) criterion and its successive interference cancellation (SIC) companion are used for detecting the signals at the relay. In this research, to achieve a better trade-off between the error rate performance and computational complexity, we propose to use a method learned from double space-time transmit diversity (DSTTD) systems for extracting the signals received. Simulations show that with our proposed scheme, a similar error rate can be achieved with less computation.
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Su, Huan-Yu, and 蘇桓瑜. "Capacity Based Antenna Selection Scheme for Two Way AF MIMO Systems in Correlated Channels." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55252778706201360783.
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碩士國立中正大學
通訊工程研究所
101
Multiple-input multiple-output (MIMO) wireless communication systems combining with relay networks can obviously improve spatial diversity, transmission reliability and cover range without any further power consumption. However, MIMO communication system requires many radio frequency (RF) chains which are known to be quite expensive. Antenna selection schemes have been proposed in order to not only maintain system performance but also control the cost. In the thesis, a layered relay antenna selection algorithm is proposed based on the maximization of sum-rate in two-hop amplify-and-forward (AF) two-way MIMO multiple-relay systems under correlated channels. Finally, simulations results indicate that the proposed antenna selection algorithm compared with other existing antenna selection algorithms provides better sum-rate performance for half-duplex AF MIMO relay networks.
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Lu, Keng-ju, and 呂庚儒. "Joint Transceiver/Relay Design for Two-Way AF-MIMO Relaying Transmission with Correlated Channels." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/38818135552747275504.
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碩士國立中正大學
通訊工程研究所
101
In the thesis, the relay-precoder and the equalizer combined optimization is proposed in a two-way amplify-and-forward (AF) multiple-input multiple-output (MIMO) single-relay system with Gaussian random and correlated channel in both hops. With the aid of taking the correlated channel into account, a transceiver joint optimization design is developed based on the minimum mean-squared error (MMSE) criterion under power constraint at the relay. This optimization belongs to non-convex so that an iterative precoding design is applied to explore local optimal solutions. Simulation results demonstrate a better performance of the proposed iterative precoding design compared with other transceiver design with correlated channels.
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Hsieh, Wei-Hsuan, and 謝維軒. "Blind estimation of channels for OFDM-based amplify-and-forward two-way relay network." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/gct4mg.
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碩士國立臺灣大學
電信工程學研究所
106
Orthogonal frequency division multiplexing (OFDM) systems has recently received considerable interest for its advantages in high-bit-rate transmissions over frequency selective fading channels. In the last decade, wireless relay network becomes an active research due to its reliability, effective spectral and power efficiency. In particular, two-way relay network (TWRN) has drawn a lot of attention because its overall communication rate is approximately twice of that achieved in the conventional one-way relay network (OWRN). This thesis studies the blind channels estimation for amplify-and-forward (AF) TWRN in cyclic-prefixed OFDM (CP-OFDM) and in zero-padded OFDM (ZP-OFDM) systems. For CP-OFDM systems, we propose three methods to estimate the first cascaded channel resulting in self-interference. These methods are circular repetition method, incorporation of cyclic-prefixed into estimation method and subspace method. Then, we investigate the estimation accuracy of the first cascaded channel when there exist virtual carriers (VC) for different methods. Also we propose a least-squares carrier frequency offset (CFO) estimation method by using VC. After that, the second cascaded channel which is from the source to destination is estimated by nulling method. The algorithm for the second cascaded channel can use repetition method to handle the case of few received blocks. In addition, we also extend our channel estimation methods to the case of ZP-OFDM systems. Simulation results are carried out to verify the performance of the proposed methods.
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Lee, Yu-Ru, and 李玉如. "Joint Power Allocation and Relay Selection Schemes for Two-Way AF Relay Systems with Nonreciprocal Channels." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/96617162812033092747.
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碩士國立清華大學
通訊工程研究所
102
In this thesis, we present two suboptimal joint power allocation (PA) and relay selection (RS) schemes with different design objectives for two-way amplify-and-forward relay systems with nonreciprocal channels, where multiple single-antenna relays are considered and only one relay is selected for cooperation with two sources. The first approach is to maximize the smaller received signal-to-noise ratios (SNRs) at the two sources under a total transmit power constraint, where closed-form PA expressions are derived to make the received SNRs at the two sources equal for each relay, and the relay resulting in the largest balanced received SNR at the two sources is selected for cooperation. The second approach is to minimize the total transmit power under received SNR constraints at the two sources, where closed-from PA expressions are obtained based on a standard convex optimization procedure for each relay, and the relay resulting in the minimum total transmit power is selected for cooperation. It is shown that earlier works relating to these two approaches for reciprocal channels are special cases of the proposed joint PA-RS schemes. Moreover, computer simulation results show that both the proposed PA schemes without RS provide better performance than the equal PA scheme, and that using the proposed RS schemes with their own corresponding proposed PA schemes further enhances the system performance.
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Tang, Kang-Tsao, and 湯剛造. "Capacity-Based Relay-and-Antenna Joint Selection Schemes for Two-Way AF-MIMO Multiple-Relay Systems in Correlated Channels." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/29e6pd.
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碩士國立中正大學
通訊工程研究所
102
The relay and antenna joint selection algorithms are proposed for the two-way amplify-and-forward (AF) multiple-input multiple-output (MIMO) multiple-relay systems in the thesis. Based on the maximization of system sum-rate capacity, both the layered distributed orthogonal relay selection (LDORS) and the singular value decomposition (SVD) based selection strategies are investigated. The LDORS scheme operates in a layered selection manner to sieve out the antenna pairs on relays by making full use of the Gram-Schmidt (GS) orthogonalization procedure and the DORS algorithm. In addition, the 2-stage SVD-based antenna selection algorithm is proposed to alleviate the complexity cost incurred by the SVD-based exhaustive search method. Finally, simulation results demonstrate that the proposed relay-and-antenna selection techniques are capable of providing the superior sum-rate performance for the two-way AF-MIMO multiple-relay systems.
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Wu, Hong-Syuan, and 吳鴻軒. "Performance Analysis of Relay Selection Using Enhanced Static Decode and Forward With Network Coding in Two-Way Relay Channels." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/46336680336315147994.
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碩士國立中正大學
通訊工程研究所
101
Along with the development of mobile communications, we have more usage in wireless transmission. Consequently, we need high quality in transmission, and the influence of fading channel will be an important factor. In this thesis, we adopt the relay selection which use Enhanced Static Decode and Forward with Network Coding (RS-ESDF-NC) in tow-way relay channels. We assume all nodes are in the half-duplex mode. Our scheme first select the optimal relay from a set of L relays. By using Min-Max relay selection criterion, we can find the optimal relay, and then uses this optimal relay. So that users exchange their information with the help of best relay.We consider three different fading channels (Rayleigh、Rician、Nakagami). The outage probability is improved when the number of relay stations increases, and The outage probability of RS-ESDF-NC is better than that ESDF-NC. The simulation results show that our system has lower outage probability which means the improvement of the reliability of the system.
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Liu, Yu-Chen, and 劉祐蓁. "Performance Analysis of Relay Selection With Enhanced Dynamic Decode-and-Forward and Network Coding in Two-Way Relay Channels." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/25357093764916564589.
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碩士國立中正大學
通訊工程研究所
101
In this thesis, we adopt the relay selection (RS) protocol proposed by Bletsas,Khisti, Reed and Lippman (2006) with Enhanced Dynamic Decode-and-Forward(EDDF) and network coding (NC) system in a two-hop two-way multi-relay network.All nodes are single-input single-output (SISO) and half-duplex, i.e., they cannot transmit and receive data simultaneously. The outage probability is analyzed and we show comparisons of outage probability with various scenarios under Rayleigh, Rician and Nakagami fading channels. Our results show that the relay selection with EDDF and network coding (RS-EDDF&NC) scheme has the best performance in the sense of outage probability upon the considered decode-and-forward (DF) relaying if there exist sufficiently relays. In addition, the performance loss is large if we select a relay at random. This shows the importance of relay selection strategies.
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Tsai, Kai-Chu, and 蔡凱竹. "Blind Estimation of Channels, CFO, I/Q Imbalance and STO for OFDM-Based Amplify-and-Forward Two-Way Relay Network." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/fxnq38.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
105
Orthogonal frequency division multiplexing (OFDM) has recently received considerable interest for its advantages in high-bit-rate transmissions over frequency-selective fading channels. Lately, wireless relay network becomes an active research due to its reliability, effective spectral and power efficiency. In particular, two-way relay network (TWRN) has become popular because its throughput is twice that of the conventional one-way relay network (OWRN). This thesis studies the blind channels, carrier frequency offset (CFO), in-phase and quadrature-phase (I/Q) imbalance and symbol timing offset (STO) estimation for amplify-and-forward (AF) TWRN CP-OFDM systems. Firstly, we use power reduction method to estimate the first cascaded channel resulting in self-interference. Secondly, we will show how to apply cyclic-prefix based algorithm to estimate CFO and I/Q imbalance jointly. After compensation of CFO and I/Q imbalance, we utilized subspace based method to estimate the second cascaded channel from source to destination. Moreover, the proposed method can be applied to multiple relay nodes. In addition, the effect of STO in self-interference signals is investigated. A blind algorithm is proposed for the estimation of STO. Simulations are carried out to verify the performance of the proposed method.
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Hsu, Ching-Hao, and 徐慶豪. "Network Coding and Distributed Space-Time Block Codes with Adaptive AAF/DAF Elements for Two-Way Relay in Impulsive Noise Channels." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/sq9te6.
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碩士國立臺北科技大學
電腦與通訊研究所
102
In the two-way relay networks with two relays between two nodes, the previous scheme proposed a two-way relay network coding system using all Decode-and-Forward (DAF) elements without STBC. In our proposed scheme, we transmit using Alamouti DSTBC with adaptive AAF/DAF elements. The simulation result shows that at 10-2 BER our proposed scheme is better than the previous scheme by 1.2dB,1.8dB,2dB and 2.2dB forδ = 2,1.44,1 and 0.8, respectively.
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Wang, Ping-Chung, and 王品中. "Channel Estimation for Two Way Relay Networks." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38187850388539477354.
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Banijamali, Seyedershad. "Gaussian Two-Way Channel with Constellation-based Input." Thesis, 2013. http://hdl.handle.net/10012/7272.
Full textAbstract:
Achieving a higher transmission rate had always been a goal in the field of communications. Having a two-way channel in which two nodes transmit and receive data at the same time, is an important tool to achieve this goal. A two-way channel is the first step from point-to-point communication channel toward multi-user networks. In its ideal form, we can transmit data two times faster by using a perfect two-way channel. However, the area of two-way channels had not been of interest of researchers during the past years and number of articles on this area is considerably low comparing to other types of multi-user communication networks, such as multiple-access channel, broadcast channel and interference channel.
On the other hand, use of analog-to-digital converters (ADC) is a must in modern systems to enable us to analyze data faster; nevertheless, presence of ADC add some other difficulties to the system.
In this thesis, different scenarios about two-way channel are studied. The Shannon's model of two-way channel and his inner and outer bounds on the capacity of this channel are presented. For the Gaussian Two-Way Channel with quantized output, in which the ambient noise has a Gaussian distribution, the expression of Shannon's inner bound for both Gaussian and discrete inputs are derived.
The best uniform quantizer to obtain the maximum achievable rate for Gaussian input is found numerically. Then we will evaluate the additive noise model for the quantizer from an information theoretic point of view.
For the discrete input, the method of rotating one input with respect to other one is employed to enlarge the achievable rate region.
At last, two scenarios will be studied in which, minimizing the power of interference, does not necessarily maximizes the transmission rate.
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Nwaekwe, Chinwe M. "Channel estimation in a two-way relay network." Thesis, 2011. http://hdl.handle.net/10155/174.
Full textAbstract:
In wireless communications, channel estimation is necessary for coherent symbol detection.
This thesis considers a network which consists of two transceivers communicating
with the help of a relay applying the amplify-and-forward (AF) relaying scheme. The
training based channel estimation technique is applied to the proposed network where
the numbers of the training sequence transmitted by the two transceivers, are different.
All three terminals are equipped with a single antenna for signal transmission and reception.
Communication between the transceivers is carried out in two phases. In the
first phase, each transceiver sends a transmission block of data embedded with known
training symbols to the relay. In the second phase, the relay retransmits an amplified
version of the received signal to both transceivers. Estimates of the channel coefficients
are obtained using the Maximum Likelihood (ML) estimator. The performance analysis
of the derived estimates are carried out in terms of the mean squared error (MSE) and
we determine conditions required to increase the estimation accuracy.UOIT
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Zhang, Haoyuan. "Cross-layer design for multi-hop two-way relay network." Thesis, 2017. http://hdl.handle.net/1828/8307.
Full textAbstract:
Physical layer network coding (PNC) was proposed under the two-way relay hannel (TWRC) scenario, where two sources exchange information aided by a relay. PNC allows the two sources to transmit to the relay simultaneously, where superimposed signals at the relay can be mapped to network-coded symbols and then be broadcast to both sources instead of being treated as interference. Concurrent transmissions using PNC achieve a higher spectrum efficiency compared to time division and network coding solutions. Existing research mainly focused on the symmetric PNC designs, where the same channel coding and modulation configurations are applied by both sources. When the channel conditions of the two source-relay links are asymmetric or unequal amount of data are exchanged, heterogeneous modulation PNC designs are necessary. In additional, the design and optimization of multi-hop PNC, where multiple relays forming a multi-hop path between the two sources, remains an open issue. The above issues motivate the study of this dissertation.
This dissertation investigates the design of heterogeneous modulation physical
layer network coding (HePNC), the integration of channel error control coding into HePNC, the combination of HePNC with hierarchical modulation, and the design and generalization of multi-hop PNC. The contributions of this dissertation are four-fold.
First, under the asymmetric TWRC scenario, where the channel conditions of
the two source-relay links are asymmetric, we designed a HePNC protocol, including the optimization of the adaptive mapping functions and the bit-symbol labeling, to minimize the end-to-end BER. In addition, we developed an analytical framework to derive the BER of HePNC. HePNC can substantially enhance the throughput compared to the existing symmetric PNC under the asymmetric TWRC scenario.
Second, we investigated channel coded HePNC and integrated the channel error
control coding into HePNC in a link-to-link coding, where the relay tries to decode the superimposed codewords in the multi-access stage. A full-state sum-product decoding algorithm is proposed at the relay based on the repeat-accumulate codes to guarantee reliable end-to-end communication.
Third, we proposed hierarchical modulation PNC (H-PNC) under asymmetric TWRC, where additional data exchange between the relay and the source with the relatively better channel condition is achieved in addition to that between the two end sources, benefiting from superimposing the additional data flow on the PNC transmission. When the relay also has the data exchange requirement with the source with a better source-relay channel, H-PNC outperforms HePNC and PNC in terms of the system sum throughput.
Fourth, we designed and generalized multi-hop PNC, where multiple relays located in a linear topology are scheduled to support the data exchange between two end sources. The impact of error propagation and mutual interference among the nodes are addressed and optimized. The proposed designs outperform the existing ones in terms of end-to-end BER and end-to-end throughout.Graduate
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Dash, Debashis. "Bounds and protocols for a two-way multiple node channel." Thesis, 2007. http://hdl.handle.net/1911/20499.
Full textAbstract:
Often in multiuser wireless systems like cellular networks, data is present in both directions (uplink and downlink). One way to formulate protocols for such networks, is to design the uplink and downlink independently. But such a design ignores the two-way nature of data. We show that by jointly designing the uplink and downlink, we get rate gains as long as there is data in both the directions. We make a distinction between data being two-way and the channel being two-way and show that for the case where only the channel is two-way, a disjoint design is optimal. The rate gains can be attributed to the inherent feedback in two-way schemes which enables cooperation in all topologies (including hidden node topologies). Furthermore, in near-far situations, the weak user gains appreciably from such cooperation. Finally we demonstrate that several well known inner bounds can be derived as special cases of our rate region.
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Hern, Brett Michael. "Coding Schemes for Physical Layer Network Coding Over a Two-Way Relay Channel." Thesis, 2013. http://hdl.handle.net/1969.1/151149.
Full textAbstract:
We consider a two-way relay channel in which two transmitters want to exchange information through a central relay. The relay observes a superposition of the trans- mitted signals from which a function of the transmitted messages is computed for broadcast. We consider the design of codebooks which permit the recovery of a function at the relay and derive information-theoretic bounds on the rates for reliable decoding at the relay.
In the spirit of compute-and-forward, we present a multilevel coding scheme that permits reliable computation (or, decoding) of a class of functions at the relay. The function to be decoded is chosen at the relay depending on the channel realization. We define such a class of reliably computable functions for the proposed coding scheme and derive rates that are universally achievable over a set of channel gains when this class of functions is used at the relay. We develop our framework with general modulation formats in mind, but numerical results are presented for the case where each node transmits using 4-ary and 8-ary modulation schemes. Numerical results demonstrate that the flexibility afforded by our proposed scheme permits substantially higher rates than those achievable by always using a fixed function or considering only linear functions over higher order fields.
Our numerical results indicate that it is favorable to allow the relay to attempt both compute-and-forward and decode-and-forward decoding. Indeed, either method considered separately is suboptimal for computation over general channels. However, we obtain a converse result when the transmitters are restricted to using identical binary linear codebooks generated uniformly at random. We show that it is impossible for this code ensemble to achieve any rate higher than the maximum of the rates achieved using compute-and-forward and decode-and-forward decoding.
Finally, we turn our attention to the design of low density parity check (LDPC) ensembles which can practically achieve these information rates with joint-compute- and-forward message passing decoding. To this end, we construct a class of two-way erasure multiple access channels for which we can exactly characterize the performance of joint-compute-and-forward message passing decoding. We derive the processing rules and a density evolution like analysis for several classes of LDPC ensembles. Utilizing the universally optimal performance of spatially coupled LDPC ensembles with message passing decoding, we show that a single encoder and de- coder with puncturing can achieve the optimal rate region for a range of channel parameters.
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Chang, Yuan-ann, and 張元安. "Using Two-Way Partition Method for Multi-Channel Broadcasting in Mobile Environment." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/71635284198968750807.
Full textAbstract:
碩士南華大學
資訊管理學研究所
93
Owing to the advance of wireless communication techniques, a mobile user can access the desired data anytime anywhere. Due to the limit of mobile device, data broadcasting is an efficient method for save bandwidth. In the multi-channel, the data can be equally distributed to different channels for reduce the broadcast cycle and reduce the client which access data item. When a mobile user submits an issue for a data set that it distributed to different broadcast channels, the state called data competition. When the numbers of data competition increase, the data collision increase also, therefore, the mobile user must wait for next broadcast cycle, and thus the mobile user needs more time to access data set. The state called data collision. In this article, we propose the Two-Way Partition Algorithm and apply it to data partition of multi-channel. We use the result of data partition to reduce the data competition. Finally, we evaluate the performance of the algorithm and compare the data competition times that influence with initial states’ and using our algorithm. The result shows that our approach significantly reduces the data competition times.
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Huang, Chao-Wei, and 黃昭瑋. "Two-Way Training Design for Discriminatory Channel Estimation in Wireless MIMO Systems." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39052366661285591678.
Full textAbstract:
碩士國立清華大學
通訊工程研究所
99
Thisworkexaminestheuseoftwo-waytraininginmultiple-inputmultiple-output(MIMO)wirelesssystemstodiscriminatethechannelestimationperformancesbetweenalegitimatereceiver(LR)andanunauthorizedreceiver(UR).Thisthesisextendsuponthepreviouslyproposeddiscriminatorychannelestimation(DCE)schemethatallowsonlythetransmittertosendtrainingsignals.ThegoalofDCEistominimizethechannelestimationerroratLRwhilerequiringthechannelestimationerroratURtoremainbeyondacertainlevel.Ifthetrainingsignalissentonlybythetransmitter,theperformancediscriminationbetweenLRandURwillbelimitedsincethetrainingsignalshelpbothreceiversperformestimatesoftheirdownlinkchannels.Inthiswork,weconsiderinsteadthetwo-waytrainingmethod-ologythatallowsboththetransmitterandLRtosendtrainingsignals.Inthiscase,thetrainingsignalsentbyLRhelpsthetransmitterobtainknowledgeofthetransmitter-to-LRchannel,butdoesnothelpURestimateitsdownlinkchannel(i.e.,thetransmitter-to-URchannel).Withtransmitterknowledgeoftheestimatedtransmitter-to-LRchannel,artificialnoise(AN)canthenbeembeddedinthenullspaceofthetransmitter-to-LRchanneltodisruptUR’schannelestimationwithoutseverelydegradingthechannelestimationatLR.Basedontheseideas,two-wayDCEtrainingschemesaredevelopedforbothreciprocalandnon-reciprocalchannels.TheoptimalpowerallocationbetweentrainingandANsignalsisdevisedunderbothaverageandindividualpowerconstraints.Numericalresultsareprovidedtodemonstratetheefficacyoftheproposedtwo-wayDCEtrainingschemes.
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Shao, Yi-Chi, and 邵貽琦. "On Malicious Behavior in Two-Way Relay Channel withVariable Analog Network Coding." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/65170988734880456941.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
101
The two-way relay channel is a fundamental building block of the cooperative wireless networks, where two sources want to exchange messages via relays. Most works in the literature on the relay networks assume that all terminals are fully cooperative. In this thesis, we consider a two-way relay channel that contains a malicious relay, and a cooperative relay which adopts the celebrated analog network coding (ANC). We aim to understand the optimal strategies of these two relays via mutual information games. The cooperative and malicious relays are two players in our game and the achievable sum rates are adopted as the utilities. The optimal transmission strategies of both types of relays are derived by identifying the Nash equilibrium (NE) of the proposed game. By allowing relays to change transmission actions symbol by symbol in a codeword length, the proposed game generalizes the mutual information games in previous works. With this new game formulation, the pure strategy NE exists where the cooperative relay is suggested to vary the amplifying coefficients of the ANC symbol by symbol even for a fixed channel. However, owing to the non-convex nature of our utilities, it is still hard to explicitly derive the pure strategy NE. To overcome this problem, the utilities are linearized. Furthermore, the special cases of our results also show that the malicious attacks proposed by previous works for the one-way relay channel may not be optimal.
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Yazdan, Panah Ali. "Relay-aided communications with partial channel state information." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4264.
Full textAbstract:
Modern wireless communication systems strive to enable communications at high data rates, over wide geographical areas, and to multiple users. Unfortunately, this can be a daunting task in practice, as natural laws governing the wireless medium may hinder point-to-point transmissions. Communications over large distances (path loss), and physical obstructions in line-of-sight signals (shadowing) are prime examples of such impediments. One promising solution is to deploy intermediary terminals to help reestablish such broken point-to-point communication links. Such terminals are called relay nodes, and the corresponding systems are referred to as being relay-aided.
As in the case of point-to-point communication, design of efficient transmission and reception techniques in relay-aided systems depends on the availability of propagational channel state information. In practice, such information is only accurate to a certain degree which is governed by overhead constraints, feedback delay, and channel fluctuations due to mobility. Understanding the impacts of such partial channel state information, and devising transmission and reception methods based on such understandings, is the main topic of this dissertation.
The transmission protocol classifies relays as either one-way, where the relay receives signals from one terminal, or two-way, where the relay receives signals from more than one terminal. Designs and solutions for both one- and two-way relaying systems are presented in this dissertation. Emphasis is placed on two-way relaying systems given their superior efficiency in utilizing channel resources.
For one-way relaying this dissertation presents power loading strategies for multiuser-multicast systems derived based on the availability of full or partial channel state information at the terminals.
In the case of two-way relaying, both single and multi-user systems are analyzed. For single-user two-way relaying, this dissertation presents optimal methods of acquiring partial channel state information via pilot-aided channel estimation methods. This includes an analysis of the effects of channel estimation upon the system sum-rate. Also, the design of channel equalizers exhibiting robustness to partial channel state information is proposed. For multi-user two-way relaying, this dissertation presents several precoding strategies at the relay terminal(s) to combat the effects co-channel interference in light of the existence of self-interference inherent to two-way relaying operations.text
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Al, Humaidi Fadhel. "Optimal power minimization in two-way relay network with imperfect channel state information." Thesis, 2010. http://hdl.handle.net/10155/113.
Full textAbstract:
We study a two-way amplify and forward relay network with two transceivers which
communicate through a network of nr relays while there is no direct link between the two
transceivers. Each relay is equipped with a single antenna for transmitting and receiving.
We study the minimization of the total transmit power that is used in all of the network
nodes given the condition that the transceiver which calculates the optimal transmitting
power has a full knowledge about the channels between itself and the relays and the
variance with zero mean of the channels between the relays and the other transceiver.
The total average power is minimized subject to a soft constraint which guarantees that
the outage probability is below a certain level. The optimal solution is derived in closed
form and leads to a single relay selection criterion.UOIT
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Lu, Po-Hsun, and 陸柏勳. "Blind Channel Estimation in OFDM Coded Two-Way Amplify-And-Forward Relay Systems." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34553081117451841752.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
102
Orthogonal frequency division multiplexing (OFDM) has recently received considerable interest for its advantages in high-bit-rate transmissions over frequency-selective fading channels. Recently, research on wireless relay networks becomes popular because of the following reasons. When a transmitter and a receiver are unable to communicate with each other because of the distance between them or fading of the channel, they can be connected by one or multiple relay nodes to create an alternate route. Relay transmission can enhance the reliability, increase the rate in wireless networks. Relay transmission provides an effective means of improving spectral and power efficiency. In addition, the use of multiple antennas to achieve transmit diversity in the cellular uplink is impractical due to the size constraints at each mobile. Cooperative communication can overcome this constraint problem. Relay nodes cooperate with terminals of the users when each relay nodes transmit its own information to destination by processing the information from source. This thesis studies the blind channel estimation for amplify-and-forward(AF) TWRN ZP-OFDM systems. We will show how to apply the subspace-based blind channel estimation algorithm for the case of TWRN ZP-OFDM systems. Pilots for estimating the scalar ambiguity in blind channel estimation are also derived. Simulations are carried out to verify the performance of the proposed method. Compared with the existing blind channel estimation method in TWRN, our proposed method has a better performance.
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"Channel Estimation in Half and Full Duplex Relays." Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.50487.
Full textAbstract:
abstract: Both two-way relays (TWR) and full-duplex (FD) radios are spectrally efficient, and their integration shows great potential to further improve the spectral efficiency, which offers a solution to the fifth generation wireless systems. High quality channel state information (CSI) are the key components for the implementation and the performance of the FD TWR system, making channel estimation in FD TWRs crucial.
The impact of channel estimation on spectral efficiency in half-duplex multiple-input-multiple-output (MIMO) TWR systems is investigated. The trade-off between training and data energy is proposed. In the case that two sources are symmetric in power and number of antennas, a closed-form for the optimal ratio of data energy to total energy is derived. It can be shown that the achievable rate is a monotonically increasing function of the data length. The asymmetric case is discussed as well.
Efficient and accurate training schemes for FD TWRs are essential for profiting from the inherent spectrally efficient structures of both FD and TWRs. A novel one-block training scheme with a maximum likelihood (ML) estimator is proposed to estimate the channels between the nodes and the residual self-interference (RSI) channel simultaneously. Baseline training schemes are also considered to compare with the one-block scheme. The Cramer-Rao bounds (CRBs) of the training schemes are derived and analyzed by using the asymptotic properties of Toeplitz matrices. The benefit of estimating the RSI channel is shown analytically in terms of Fisher information.
To obtain fundamental and analytic results of how the RSI affects the spectral efficiency, one-way FD relay systems are studied. Optimal training design and ML channel estimation are proposed to estimate the RSI channel. The CRBs are derived and analyzed in closed-form so that the optimal training sequence can be found via minimizing the CRB. Extensions of the training scheme to frequency-selective channels and multiple relays are also presented.
Simultaneously sensing and transmission in an FD cognitive radio system with MIMO is considered. The trade-off between the transmission rate and the detection accuracy is characterized by the sum-rate of the primary and the secondary users. Different beamforming and combining schemes are proposed and compared.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2018
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Schnurr, Clemens [Verfasser]. "Achievable rates and coding strategies for the two-way relay channel / von Clemens Schnurr." 2008. http://d-nb.info/990689727/34.
Full text
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Li, Sheng-Hung, and 李聖弘. "Performance Analysis of Relay Selection in Two-Way Relay Networks with Channel Estimation Error." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/8msjk8.
Full textAbstract:
碩士國立中山大學
通訊工程研究所
103
The impact of channel estimation errors is investigated in two-way relay networks (TWRNs) with two different channel state information (CSI) estimation schemes, namely, cascaded and separate. In the cascaded scheme, the relay node is selected on the basis of the CSI of the individual channels between the source nodes and the relay node. In the separate scheme, relay node selection is based on the CSI of the cascaded channel between the two source nodes. For both estimation schemes, the effect of the CSI estimation error on the outage probability is examined by Cramer-Rao lower bound. Contrary to previous reports, the source nodes in the TWRN are assumed to yield different estimation errors. Numerical results confirm the validity of the derived expression and indicate that the presence of different estimation errors at the two source nodes can significantly influence the performance of the TWRN. However, we extend the relay selection problem to non-reciprocal TWRNs. We propose a selection scheme based on the concept of censoring rule, in which each relay node can decide whether the received signal should be forwarded. This method can save a level of transmission power and maintain the diversity gain without gathering all of the CSI between the source nodes and relay nodes at a central node. The effectiveness of the proposed scheme is evident in the simulation results.
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Chiu, Po-Chun, and 邱泊鈞. "Joint Time Synchronization and Channel Estimation for Two-Way Amplify-and-Forward Relay Systems." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77686428256542237738.
Full textAbstract:
碩士國立清華大學
通訊工程研究所
101
In this thesis, we consider a two-way relay system where two terminals exchange their information via an amplify-and-forward relay in a bi-directional manner. Due to the two-way relay protocol, signals from both terminals travel through different cascaded channels and this makes synchronization and channel estimation much more complicated than those in conventional one-way relay systems. To cope with these problems, we propose a joint time synchronization and channel estimation scheme based on a specific training sequence arrangement, where each terminal’s training sequence consists of a perfect sequence (with an ideal auto-correlation function) attached by an appropriate cyclic prefix and postfix. The proposed scheme relies on a first channel tap selection process, whose performance is highly dependent on the choice of a threshold to distinguish the signal outputs from noise. By analyzing some possible probability density functions of the correlator output, we derive optimal thresholds for selection of the first channel tap. With these thresholds, the proposed scheme provides better time synchronization performance than the maximum-likelihood approach for low signal-to-noise ratio (SNR) cases; both have similar performance for high SNR cases. It is also shown that the proposed scheme involves much less computational complexity than the maximum-likelihood approach.
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Chen, Chun-Ting, and 陳俊廷. "Analysis of the Degrees of Freedom of Two-Way MIMO Broadcast Channel with Delayed CSIT." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/ddwyu7.
Full textAbstract:
碩士元智大學
通訊工程學系
104
Nowadays, perfect channel state information at transmitters (CSIT) is widely assumed in the study of multiple-input multiple-output (MIMO) systems. All of the transmitters and receivers know the channel state information to support the use of the zero-forcing scheme [1] and interference alignment scheme [2]. Cadambe and Jafar proposed the interference alignment scheme [2] for K-user interference channel with perfect CSIT. However, we hope we can use the completely stale transmitter channel to assist receivers on decoding the message. David Tse and Maddah-Ali proposed a method to decode the receiver messages that uses the delayed CSIT. In this thesis, we modify the channel model that David Tse and Maddah-Ali studied. Finally, we discuss the degrees of freedom and compare channel rate for simulation.
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Chen, Yu-Ching, and 陳予勁. "Artificial Noise Design for Two-Way Training Based Discriminatory Channel Estimation in Wireless MIMO Systems." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80553890200023117660.
Full text
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Wang, Chenyuan. "Performance evaluation and enhancement for AF two-way relaying in the presence of channel estimation error." Thesis, 2012. http://hdl.handle.net/1828/3954.
Full textAbstract:
Cooperative relaying is a promising diversity achieving technique to provide reliable transmission, high throughput and extensive coverage for wireless networks in a variety of applications. Two-way relaying is a spectrally efficient protocol, providing one solution to overcome the half-duplex loss in one-way relay channels. Moreover, incorporating the multiple-input-multiple-output (MIMO) technology can further improve the spectral efficiency and diversity gain. A lot of related work has been performed on the two-way relay network (TWRN), but most of them assume perfect channel state information (CSI). In a realistic scenario, however, the channel is estimated and the estimation error exists. So in this thesis, we explicitly take into account the CSI error, and investigate its impact on the performance of amplify-and-forward (AF) TWRN where either multiple distributed single-antenna relays or a single multiple-antenna relay station is exploited.
For the distributed relay network, we consider imperfect self-interference cancellation at both sources that exchange information with the help of multiple relays, and maximal ratio combining (MRC) is then applied to improve the decision statistics under imperfect signal detection. The system performance degradation in terms of outage probability and average bit-error rate (BER) are analyzed, as well as their asymptotic trend. To further improve the spectral efficiency while maintain the spatial diversity, we utilize the maximum minimum (Max-Min) relay selection (RS), and examine the impact of imperfect CSI on this single RS scheme. To mitigate the negative effect of imperfect CSI, we resort to adaptive power allocation (PA) by minimizing either the outage probability or the average BER, which can be cast as a Geometric Programming (GP) problem. Numerical results verify the correctness of our analysis and show that the adaptive PA scheme outperforms the equal PA scheme under the aggregated effect of imperfect CSI.
When employing a single MIMO relay, the problem of robust MIMO relay design has been dealt with by considering the fact that only imperfect CSI is available. We design the MIMO relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. The optimization problem corresponding to the robust MIMO relay design is shown to be nonconvex. This motivates the pursuit of semidefinite relaxation (SDR) coupled with the randomization technique to obtain computationally efficient high-quality approximate solutions. Numerical simulations compare the proposed MIMO relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty.Graduate