Dissertations / Theses on the topic 'Relayed communication systems'
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Negi, Ansuya. "Analysis of Relay-based Cellular Systems." PDXScholar, 2006. https://pdxscholar.library.pdx.edu/open_access_etds/2668.
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Relays can be used in cellular systems to increase coverage as well as reduce the total power consumed by mobiles in a cell. This latter benefit is particularly useful for mobiles operating on a depleted battery. The relay can be a mobile, a car or any other device with the appropriate communication capabilities. In thesis we analyze the impact of using relays under different situations. We first consider the problem of reducing total power consumed in the system by employing relays intelligently. We find that in a simulated, fully random, mobile cellular network for CDMA (Code Division Multiple Access), significant energy savings are possible ranging from 1.76 dB to 8.45 dB.
In addition to reducing power needs, relays can increase the coverage area of a cell by enabling mobiles located in dead spots to place relayed calls. We note that use of relays can increase the useful service area by about 10% with real life scenarios. We observe that in heavy building density areas there is more need of relays as compared to low building density areas. However, the chance of finding relays is greater in low building density areas. Indeed, having more available idle nodes helps in choosing relays, so we conclude that unlike present day implementations of cellular networks, the base station should admit more mobiles (beyond the capacity of the cell) even if they are not placing calls since they can be used as relays.
One constraint of using relays is the potential to add interference in the same cell and in neighboring cells. This is particularly true if the relays are not under power control. Based on our analysis, we conclude that in interference limited systems like CDMA the relays have to be under power control otherwise we will reduce the total capacity by creating more dead spots. Thus, we believe that either the base station should be responsible to allocate relays or relays should be provided with enough intelligence to do power control of the downlink. Finally, we show how utility of data services can be increased by use of relays.
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Lee, Justine Bing. "Transceiver Designs for MIMO Relay Communication Systems." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/83305.
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Recently, the application of SWIPT in the energy-limited wireless system has attracted much attention from researchers due to the SWIPT technology provide the capability to prolong the limited lifetime of the wireless system. For a wireless communication system, a relay node helps to extend the network coverage, while the MIMO relay technique helps in enhancing the system performance. In this thesis, the investigation concerning the application of SWIPT in the MIMO relay system is investigated.
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Dong, Linhao. "Resource allocation for relay based green communication systems." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/15233/.
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The relay based cooperative network is one of the promising techniques for next generation wireless communications, which can help extend the cell coverage and enhance the diversity. To deploy relays efficiently with limited power and bandwidth under certain performance requirements, resource allocation (RA) plays an increasingly important role in the system design. In recent years, with the fast growth of the number of mobile phone users, great portion of CO2 emission is contributed by wireless communication systems. The combination of relay techniques and RA schemes reveals the solution to green communications, which aims to provide high data rate with low power consumption. In this thesis, RA is investigated for next generation relay based green wireless systems, including the long-range cellular systems, and the short-range point-to-point (P2P) systems. In the first contribution, an optimal asymmetric resource allocation (ARA) scheme is proposed for the decode-and-forward (DF) dual-hop multi-relay OFDMA cellular systems in the downlink. With this scheme, the time slots for the two hops via each of the relays are designed to be asymmetric, i.e., with K relays in a cell, a total of 2K time slots may be of different durations, which enhances the degree of freedom over the previous work. Also, a destination may be served by multiple relays at the same time to enhance the transmission diversity. Moreover, closed-form results for optimal resource allocation are derived, which require only limited amount of feedback information. Numerical results show that, due to the multi-time and multi-relay diversities, the proposed ARA scheme can provide a much better performance than the scheme with symmetric time allocation, as well as the scheme with asymmetric time allocation for a cell composed of independent single-relay sub-systems, especially when the relays are relatively close to the source. As a result, with the optimal relay location, the system can achieve high throughput in downlink with limited transmit power. In the second contribution, the power consumption in relay based 60 GHz cooperative networks is studied, which is based on three-terminal diversity amplify-and-forward (DAF) and diversity DF (DDF) relaying strategies. A total power consumption model including drive power, decoding power, and power consumption of power amplifier (PA) is proposed, excluding the transmit power, as it is relatively small compared to decoding power and PA power in the indoor environment. This model is formulated as a function of drive power, which gives an easy access to the system level power allocation. To minimise the system total power consumption, the optimal drive power can be allocated to the source node by numerical searching method while satisfying the data rate requirement. The impact of relay locations on the total power consumption is also investigated. It is shown that, with the same data rate requirement, in the small source-relay separation case, DAF consumes slightly less power than DDF; while with larger source-relay separation, DAF consumes much more power than DDF. In the future work, multiuser relay-based short-range communication systems will be considered for the 60 GHz communication in the fading channel scenario, which extends the proposed power consumption model in a more practical way. The power consumption model of other components, such as analog-to-digital converter, data buffer, modulation/demodulation could also be considered to provide more details about green P2P communications.
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Gopal, Lenin. "Robust transceiver designs for MIMO relay communication systems." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/643.
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The thesis investigates robust linear and non-linear transceiver design problems for wireless MIMO relay communication systems with the assumption that the partial information of the channel is available at the relay node. The joint source and relay optimization problems for MIMO relay systems are highly nonconvex, in general. We transform the problems into suitable forms which can be efficiently solved using standard convex optimization techniques. The proposed design schemes outperform the existing techniques.
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Nguyen, Khoa Xuan. "Transceiver Optimization for Interference MIMO Relay Communication Systems." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/48822.
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This thesis focuses on transceivers design for interference MIMO relay systems. Based on the MMSE criterion, several iterative algorithms are proposed to jointly optimize the source, relay, and receiver matrices subjecting to the individual power constraints at the source and the relay nodes. These algorithms have better performance than some existing algorithms and provide a better performance-complexity trade-off which is interesting in practical interference MIMO relay communication systems.
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Dai, Gao Yang. "A novel soft forwarding technique for cooperative communication /." View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?ECED%202010%20DAI.
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Yang, Weidong. "Vector channel study and related issues in selective transceiving /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Kawanishi, Kenichi. "Studies on Batch Arrival Models and Related Traffic Issues in Communication Systems." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150627.
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Khandaker, Muhammad Ruhul Amin. "Signal processing algorithms for multiuser MIMO relay communication systems." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1797.
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The increasing demand for mobile applications such as streaming media, software updates, and location-based services involving group communications has prompted the need for wireless communication technologies that can support reliable high data rates. However, wireless channel is subject to signal fading that severely degrades the system spectral efficiency. By exploiting the spatial diversity, multiple-input multiple-output (MIMO) techniques can provide both theoretically attractive and technically practical solutions to combat channel fading. Moreover, in the case of long source-destination distance, single or multiple MIMO relay node(s) is necessary to combat the pathloss and/or shadowing effects of wireless channel and relay signals from the source to the destination.In this thesis, we focus on multiuser MIMO relay systems. We first present joint source, relay, and receiver optimization algorithms for the uplink system based on the minimum mean-squared error (MMSE) criterion subjecting to individual power constraints at the source and the relay nodes. The proposed algorithms outperform the existing techniques in terms of both MSE and bit-error-rate (BER). Next, in the downlink system, we consider multicasting multiple data streams among a group of users with the aid of a relay node, where all the nodes are equipped with multiple antennas. The downlink system performance is optimized subjecting to both power constraints at the source and the relay nodes and quality-of-service (QoS) constraints at the receivers.Then we present the duality between the uplink and the downlink of a multi-hop MIMO relay system. Based on this duality, we propose an optimal design of the source precoding matrix and relay amplifying matrices for multi-hop MIMO relay system with a nonlinear dirty paper coding (DPC)- based transmitter at the source node. The proposed nonlinear transmitter algorithm outperforms the existing decision feedback equalizer (DFE)-based receiver schemes.Multiuser MIMO relaying is then considered in an interference system where a group of transmitters communicate simultaneously with their desired destination nodes with the aid of multiple relay nodes, all equipped with multiple antennas. Transmit-relay-receive beamforming technique is exploited to minimize the total source and relay transmit power in conjunction with transmit power control such that a minimum QoS threshold is maintained at each receiver. The proposed scheme generalizes the existing single-hop MIMO interference systems and the single-antenna, dual-hop interference relay systems to the dual-hop interference MIMO relay systems with any number of source, relay, and destination nodes, all equipped with multiple antennas.The above algorithms are developed assuming that the instantaneous channel state information (CSI) knowledge of both the source-relay link and the relay-destination link is available at the scheduler. However, in practical relay communication systems, the instantaneous CSI is unknown, and therefore, has to be estimated. Hence, we finally propose a bandwidth efficient MIMO channel estimation algorithm that provides the destination node with full knowledge of all channel matrices involved in a dual-hop MIMO communication. The proposed approach attains smaller channel estimation error and is applicable for both one-way and two-way MIMO relay systems.
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Wu, Victor Kai Yuen. "OFDM-based cooperative communications in a single path relay network and a multiple path relay network." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-11092006-152421/.
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To, Duc. "Coded systems and techniques for wireless communications with/without relays." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa43104.
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Muratori, Erik. "Analysis of Space Communication Systems via Satellite Relaying." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22837/.
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È noto che l’uso di bande a RF con frequenze estremamente alte nei sistemi wireless per comunicazione digitale consente potenzialmente di raggiungere velocità di trasmissione dei dati molto elevate, rispetto a quelli ottenibili a frequenze più basse, a parità di tasso di errore. Ciò è vero in particolare per propagazione in spazio libero con antenne direttive. Tali bande di frequenza estremamente elevate sono tuttavia raramente impiegate nelle comunicazioni spaziali deep-space a causa della loro vulnerabilità ai disturbi atmosferici. Tuttavia, esse possono potenzialmente fornire diversi vantaggi nei collegamenti di telemetria deep-space nell'ambito di architetture “two-leg” con relay satellitare orbitante fuori dall'atmosfera terrestre. In tale configurazione, il collegamento da spazio remoto a relay, non influenzato dall’atmosfera terrestre, può utilizzare una banda di frequenze estremamente elevata (compatibilmente con vincoli di carattere tecnologico), mentre il collegamento da relay a ground station può utilizzare una banda più classica, ad esempio una delle bande raccomandate per comunicazioni near-Earth. Lo scopo della tesi è stato quello di confrontare le prestazioni di architetture “two-leg” con quelle ottenibili da un collegamento deep space diretto da spacecraft a ground, in banda X oppure in banda Ka. La valutazione è stata possibile attraverso la creazione di link budget accurati, che includono l'effetto dell'atmosfera e gli errori di puntamento, e analizzando le due diverse comunicazioni, mostrando in che condizioni è possibile avere un miglioramento delle prestazioni.
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Yeung, Wing Lok. "System development with communicating sequential processes : formalisation and related studies." Thesis, Staffordshire University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303217.
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Li, Houmin Thomas Gwynedd A. "Geotextile antenna design for mobile phone cooperative communication relay node." Auburn, Ala., 2008. http://hdl.handle.net/10415/1498.
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Kwon, Bongkyoung Kwon. "Adaptive frame structure and OFDMA resource allocation in mobile multi-hop relay networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31818.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Dr. John A. Copeland; Committee Member: Dr. George F. Riley; Committee Member: Dr. Henry L. Owen; Committee Member: Dr. Mary Ann Ingram; Committee Member: Dr. Patrick Traynor. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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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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Sousa, Igor FlÃvio SimÃes de. "Distributed processing in receivers based on tensor for cooperative communications systems." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12792.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorEricsson Brasil
In this dissertation, we present a distributed data estimation and detection approach for the uplink of a network that uses CDMA at transmitters (users). The analyzed network can be represented by an undirected and connected graph, where the nodes use a distributed estimation algorithm based on consensus averaging to perform joint channel and symbol estimation using a receiver based on tensor signal processing. The centralized receiver, developed for a central base station, and the distributed receiver, developed for micro base stations, have their performances compared in a heterogeneous network. Then, two tensor-based receivers are proposed to be used in a relay-assisted network. In this case, the proposed receiver makes use of collaborative signal processing among relays to recover sources information before forwarding to the base station using a Decode-and-Forward protocol. The first receiver is based on the uncoded transmission of the tensor data reconstructed by the relays from the estimation of their factors matrix. The second one considers a tensor encoding of symbols estimated at the relays before transmission to the base station. The different proposed receivers are compared by means of computer simulations in terms of convergence and bit error rate.
Nesta dissertaÃÃo, apresentamos uma abordagem distribuÃda para a estimaÃÃo e detecÃÃo de dados para uplink em uma rede que emprega CDMA nos transmissores (usuÃrios). A rede analisada pode ser representada por um grafo sem direÃÃo e conectado, em que os nÃs fazem uso de um algoritmo de estimaÃÃo distribuÃda baseado em consenso mÃdio para realizar a estimaÃÃo conjunta de sÃmbolos transmitidos e do canal, utilizando um receptor baseado em processamento tensorial. O receptor centralizado, operando em uma EstaÃÃo RÃdio Base central, e o receptor distribuÃdo, operando em Micro EstaÃÃes RÃdio Base, tÃm seus desempenhos comparados em uma rede heterogÃnea. Em seguida, considerando-se uma rede assistida por repetidores, dois receptores tensoriais sÃo propostos. Neste caso, fazemos uso de um processamento de sinais colaborativo entre os repetidores para a recuperaÃÃo da informaÃÃo transmitida pela fonte, antes de ser encaminhada para estaÃÃo rÃdio base fazendo uso do protocolo Decode-and-Forward. O primeiro receptor à baseado na transmissÃo nÃo codificada do tensor de dados reconstruÃdo pelos repetidores a partir da estimaÃÃo de suas matrizes fatores. O segundo considera uma codificaÃÃo tensorial dos sÃmbolos previamente estimados nos repetidores antes da transmissÃo para estaÃÃo rÃdio base. Os diferentes receptores propostos sÃo comparados atravÃs de simulaÃÃes computacionais em termos de convergÃncia e taxa de erro de bit.
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Musa, Ismail Kalimullah. "Optimal Robust Transceiver Designs for Non-regenerative Multicasting MIMO Relay Communication Systems." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/65944.
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The thesis is investigated the robust transceiver designs of two-hop non-regenerative multicasting multiple-input multiple-output (MIMO) relay communication systems with the assumption that the relay knows the partial channel information of the relay-destination and the source-relay links. The source and relay optimization problems are highly nonconvex, in general. The optimization problems are transformed into suitable forms which can be efficiently solved using standard convex optimization techniques. The proposed design schemes outperform the existing techniques.
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Zhang, Jin. "Relay and routing selection in relay-based wireless networks /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20ZHANG.
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Jayasinghe, L. K. (Laddu Keeth Saliya). "Analysis on MIMO relaying scenarios in wireless communication systems." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526207391.
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Abstract The thesis concentrates on evaluating and improving performances of various multiple-input multiple-output (MIMO) relaying scenarios that are particularly relevant to future wireless systems. A greater emphasis is placed on important practical situations, considering relay deployments, availability of channel state information (CSI), limitations of spectrum, and information secrecy. Initially, the performance of a non-coherent amplify-and-forward (AF) MIMO relaying is analyzed when the relay is deployed with the relay-to-destination channel having a line-of-sight (LoS) path. The main attention is given to analyzing the performance of orthogonal space-time block coded based non-coherent AF MIMO system. Exact expressions of statistical parameters and performance metrics are derived considering the instantaneous signal-to-noise ratio (SNR) received at the destination. These performance metrics reveal that a strong LoS component in relay-destination channel always limits the performance promised by MIMO scattering environment when both nodes have multiple antennas. The thesis also considers scenarios in MIMO two-way relaying (TWR) with physical layer network coding (PNC) mapping at the relay. PNC mapping becomes complex with multiple streams being combined at the relay node. Joint precoder-decoder schemes are considered to ease this, and various studies are carried out depending on the CSI. The zero-forcing criterion is used at the nodes when perfect CSI is available. For the imperfect CSI scenario, a robust joint precoder-decoder design is considered. The precoder and decoder matrices are obtained by solving optimization problems, which are formulated to maximize sum-rate and minimize weighted mean square error (WMSE) under transmit power constraints on the nodes. Next, a precoder-decoder scheme for MIMO underlay device-to-device (D2D) communication system is investigated by considering two D2D modes; PNC based D2D and direct D2D. The joint design is based on minimizing mean square error (MSE) which is useful to mitigate interference, and to improve the performance of both D2D and cellular communications. Distributed and centralized algorithms are proposed considering bi-directional communication in both D2D and cellular communications. System performance is discussed with two transmit mode selection schemes as dynamic and static selection schemes. The results show that the PNC based D2D mode extends the coverage area of D2D communication. Finally, secure beamforming schemes for the PNC based MIMO TWR systems are investigated when multiple eavesdroppers are attempting to intercept the user information. The CSI of the user-to-eavesdropper channels is imperfect at the users. The channel estimation errors are assumed with both ellipsoidal bound and Gaussian Markov uncertainty models. Robust optimization problems are formulated considering both scenarios to design beamforming vectors at the users and relay. Numerical results suggest that the proposed algorithms converge fast and provide higher securityTiivistelmä Tässä väitöskirjassa keskitytään arvioimaan ja parantamaan suorituskykyä useissa moniantennitoistinjärjestelmissä, jotka ovat ajankohtaisia tulevaisuuden langattomissa verkoissa. Erityisesti työssä analysoidaan tärkeitä käytännön tilanteita, sisältäen toistimien sijoittamisen, kanavatiedon saatavuuden, rajoitetun taajuuskaistan ja tiedon salauksen. Aluksi epäkoherentin, vahvistavan ja jatkolähettävän moniantennitoistimen suorituskykyä analysoidaan tilanteessa, jossa toistin on sijoitettu siten, että kohteeseen on suora yhteys. Suorituskyvyn arvioinnin pääkohteena on ortogonaalinen tila-aika-tason lohkokoodattu epäkoherentti vahvistava ja jatkolähettävä moniantennitoistin. Työssä johdetaan tarkat lausekkeet tilastollisille parametreille ja suorituskykymittareille ottaen huomioon hetkellinen signaalikohinasuhde vastaanottimessa. Nämä suorituskykymittarit ilmaisevat, että toistimen ja kohteen välillä oleva vahva suoran yhteyden komponentti rajoittaa sitä suorituskykyä, jota moniantennijärjestelmän hajontaympäristö ennustaa. Työssä tutkitaan myös kahdensuuntaisia moniantennitoistimia, jotka käyttävät fyysisen kerroksen verkkokoodausta. Koodauksesta tulee monimutkaista, kun monia datavirtoja yhdistetään toistimessa. Tämän helpottamiseksi käytetään yhdistettyä esikoodaus-dekoodausmenetelmää, jota tutkitaan erilaisten kanavatietojen tapauksissa. Täydellisen kanavatiedon tapauksessa käytetään nollaanpakotuskriteeriä. Epätäydellisen kanavatiedon tapauksessa käytetään robustia yhdistettyä esikoodaus-dekoodausmenetelmää. Esikoodaus- ja dekoodausmatriisit saadaan ratkaisemalla optimointiongelmat. Nämä ongelmat on muodostettu maksimoimaan summadatanopeus, ja minimoimaan painotettu keskineliövirhe, kun optimointirajoitteina ovat solmujen lähetystehot. Seuraavaksi esikoodaus-dekoodausmenetelmää tutkitaan moniantennijärjestelmässä, jossa käytetään kahdentyyppistä laitteesta-laitteeseen (D2D) kommunikaatiomenetelmää: fyysisen kerroksen verkkokoodaukseen pohjautuvaa D2D- ja suoraa D2D-kommunikaatiota. Yhteissuunnittelu perustuu keskineliövirheen minimointiin, joka on hyödyllistä, kun halutaan vähentää häiriötä ja parantaa molempien verkkojen suorituskykyä. Työssä ehdotetaan hajautettuja ja keskitettyjä algoritmeja tilanteessa, jossa käytetään kaksisuuntaista kommunikaatiota molemmissa verkoissa. Järjestelmän suorituskykyä arvioidaan, kun käytetään kahta eri lähetystilan valintaa, dynaamista ja staattista. Tulokset osoittavat, että fyysisen kerroksen verkkokoodaukseen pohjautuva D2D kasvattaa D2D-kommunikaatiojärjestelmän kantamaa. Lopuksi, turvallisia keilanmuodostustekniikoita arvioidaan fyysisen kerroksen verkkokoodaukseen pohjautuvassa kahdensuuntaisessa moniantennitoistinjärjestelmässä, kun useat salakuuntelijat yritävät siepata käyttäjätiedon. Käyttäjillä on epäideaalinen kanavatieto heidän ja salakuuntelijoiden välisten linkkien kanavista. Kanavatiedon estimointivirheitä arvioidaan ellipsoidisella ja Gauss-Markov-epävarmuusmallilla. Robustit optimointiongelmat, joissa suunnitellaan keilanmuodostusvektorit käyttäjän ja toistimen välille, muodostetaan molemmille malleille. Numeeriset tulokset osoittavat, että ehdotetut algoritmit konvergoituvat nopeasti ja tarjoavat korkeamman turvallisuuden
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Bui, Tuyen Thi Bich Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Superposition coding and modulation technique for wireless relay systems." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/36827.
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Cooperative communication has been considered a promising technique used in wireless network to introduce diversity. Based on distributed architecture, cooperative network enables single-antenna users to share their information as a virtual multiple antenna array, which makes it possible to enhance the user data rates and obtain the diversity gain. Depending on the ways users share and process the information, practical user cooperation is mainly grouped in three modes: Amplify and Forward (AF), Decode and Forward (DF) and Compress and Forward (CF). Generally, DF outperforms AF in most practical implementation and is alternately the best by theoretical analysis. In particular, it is shown in theory that DF outperforms CF when the inter-user link is in good condition and vice versa. Considered as a capacity achieving approach, superposition encoding technique produces approximate Gaussian output signals. It is the power and spectral efficiency of the encoding scheme that make it useful for several wireless communication systems such as MIMO system, relay channels, and so on. The main goal of the thesis is to study how much superposition coding can help when applied to DF user cooperation. In particular, a new DF scheme with soft information relaying technique is proposed to overcome the performance degradation happening when the quality of the inter-user channel is bad. Based on the scheme, soft log-likelihood ratio (LLR) of the relay decoder is quantized, encoded, modulated by superimposition and then forwarded to the destination. The destination receiver employs an iterative superposition decoder and modified maximum a posteriori probability (MAP) decoder to recover the transmitted signal from the source. The performance of the scheme is evaluated by simulation. We show that the new scheme can significantly outperform the conventional DF scheme even in a poor inter-user channel. Furthermore, a new cooperative transmission strategy based on superposition and multiuser detection techniques is also investigated in the thesis. The new scheme is an improved DF scheme in which the two users take turns in being the relay for each other and the signal forwarded by each user is the superimposed data of both users. Here, interleavers are introduced in the superposition process as an efficient user separation tool, providing a large improvement in error performance and also facilitating the decoding process at the destination. Different types of iterative receivers are examined. The performance of the scheme is evaluated by simulation. It is shown that the new transmission scheme outperforms the conventional one in terms of both spectral and power efficiency.
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Zhang, Shunqing. "Cooperative relay in the next generation wireless networks /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20ZHANGS.
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Chen, Yi-Da. "The Dynamics of Task-related Discussion in the Pursuit of Radical Innovation: Innovation Project Teams as Interpretation Systems." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311106.
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As global competition is increasingly intensified, radical innovation has become more and more important for corporations in high-velocity industries. Thanks to the advances of information systems and communication media, corporations can easily reach out to experts all over the world and form project teams dedicated to the innovation effort. However, research shows that while some innovation teams are very successful in achieving significant breakthroughs, many struggle to make their collaborations work. In this dissertation, we aim to provide a comprehensive understanding of the collaboration challenges that an innovation team faces. By considering the simultaneous needs for differentiation and integration in the innovation effort and taking a communication/ interpretive perspective, we develop a theoretical model to investigate how the processes of differentiation and integration are shaped through team communication and influence an innovation team's collaboration outcomes. Specifically, we delineate four structural properties of team communication to capture these two processes - the number of issue streams explored, the number of attention switches initiated, the conceptual linkage between issue streams, and the level of deliberation after each attention switch - and identify four categories of factors that influence the development of these two processes - team composition, semi-structures, communication contexts, and communication environments. We conduct a case study as a preliminary test of our theoretical model, and find that the model provides comprehensive explanations for the collaboration dynamics and issues of these teams. We believe such a theoretical model can contribute to a better understanding of the complexity involved in an innovation project and bring fresh insights to the design of information systems for supporting an innovation team.
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Wang, Hongzheng. "Performance analysis of cooperative systems with spatial random relays and interfering nodes." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B44205041.
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Hinic, Vladimir. "Brain computer interface system for communication and robot control based on auditory evoked event-related potentials." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28226.
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This study evaluates the suitability of the auditory, specifically spoken words, evoked P300 based Brain-Computer Interface (BCI) for the human-computer symbiotic control of Robotic Sensor Agents (RSA). This study is unique in using auditory evoked P300 for BCI communication and control, contrary to currently established P300 BCI research. The general, elaborate, and multi platform software framework BCIILab was developed as a part of BCI laboratory workbench used specifically in the research. Result of this study shows that it is possible to use auditory P300 based BCI for the complementary control of RSA on the strategic level. The problems encountered in classification during experiments were highlighted and suggestion for future research given.
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Beins, Eva Carolina [Verfasser]. "The role of the endocannabinoid system in stress-related disorders and neuroimmune communication / Eva Carolina Beins." Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1218301619/34.
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Abaza, Mohamed. "Cooperative MIMO techniques for outdoor optical wireless communication systems." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0073/document.
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Au cours de la dernière décennie, les communications optiques en espace libre (FSO) ont pris de l’ampleur dans les deux domaines académiques et industriels. L’importance de FSO s’appuie sur la possibilité de faire un système de transmission économique et écologique avec un débit élevé et sans licence à l’opposition des systèmes de transmission radiofréquences (RF). Dans la plupart des travaux antécédents sur les systèmes multi-émetteurs, seulement les canaux décorrélés ont été considérés. Un canal décorrélé nécessite un espace suffisant entre les émetteurs. Cette condition devient difficile et non-réalisable dans certaines applications. Pour cette raison, nos études se focalisent sur les performances des codes à répétition RC (Repitition Codes) et les codes OSTBC (Orthogonal Space-Time Block Codes) dans des canaux log-normaux corrélés en utilisant une modulation d’intensité et une détection directe (IM/DD). En addition, les effets des différentes conditions météorologiques sur le taux d’erreur moyen (ABER) sont étudiés. Les systèmes FSO à multi-entrées/ multi-sorties MIMO (Multiple-Input Multiple-Output) avec une modulation SSK (Space Shift Keying) ont été abordés. Les résultats obtenus montrent que la SSK est supérieure aux RC avec une modulation d’impulsion (Multiple Pulse Amplitude Modulation) pour toute efficacité spectrale égale ou supérieure à 4 bit/s/Hz. Nous avons aussi analysé les performances d’un système à sauts multiples (Multi-Hop) et des relais à transmission directe (forward relays). Nos simulations montrent que le système ainsi considéré est efficace pour atténuer les effets météorologiques et les pertes géométriques dans les systèmes de communication FSO. Nous avons montré qu’un tel système avec plusieurs entrées et une sortie (MISO, i.e. multiple-input single-output) à sauts multiples est supérieur à un système MISO avec un lien direct (direct link) avec une forte atténuation. Pour satisfaire la demande croissante des réseaux de communication à débits élevés, la communauté scientifique s'intéresse de plus en plus aux systèmes FSO avec des relais full-duplex (FD). Pour ces derniers systèmes, nous avons étudié la probabilité d'erreur moyenne (ABER) et nous avons analysé leurs performances. En considérant des différentes conditions de transmission, les performances de relais FD ont été comparées à celles d'un système avec un lien direct ou des relais half-duplex. Les résultats obtenus montrent que les relais FD ont le minimum ABER. En conséquence, les résultats obtenus dans cette thèse sont très prometteurs pour la prochaine génération de FSOFree-space optical (FSO) communication has been the subject of ongoing research activities and commercial attention in the past few years. Such attention is driven by the promise of high data rate, license-free operation, and cheap and ecological friendly means of communications alternative to congested radio frequency communications. In most previous work considering multiple transmitters, uncorrelated channel conditions have been considered. An uncorrelated channel requires sufficient spacing between transmitters. However, this can be difficult and may not be always feasible in some applications. Thereby, this thesis studies repetition codes (RCs) and orthogonal space-time block codes performance in correlated log-normal FSO channels using intensity modulation and direct detection (IM/DD). Furthermore, the effect of different weather conditions on the average bit error rate (ABER) performance of the FSO links is studied. Multiple-input multiple-output (MIMO) FSO communication systems using space shift keying (SSK) modulation have been also analyzed. Obtained results show that SSK is a potential technique for spectral efficiencies equal or greater than 4 bits/s/Hz as compared to RCs with multiple pulse amplitude modulations. The performance analysis of a multi-hop decode and forward relays for FSO communication system using IM/DD is also considered in this thesis. It is shown that multi-hop is an efficient technique to mitigate atmospheric turbulence and different weather attenuation effects and geometric losses in FSO communication systems. Our simulation results show that multiple-input single-output (MISO) multi-hop FSO systems are superior to direct link and MISO systems over links exhibiting high attenuation. Meeting the growing demand for higher data rates communication networks, a system with full-duplex (FD) relays is considered. For such a system, the outage probability and the ABER performance are analyzed under different turbulence conditions, misalignment error and path loss effects. FD relays are compared with the direct link and half-duplex relays. Obtained results show that FD relays have the lowest ABER and the outage probability as compared to the two other systems. Finally, the obtained results in this thesis are very promising towards the next generation of FSO systems
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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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Patel, Chirag S. "Wireless channel modeling, simulation, and estimation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03282006-200818/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Andrew, Alfred, Committee Member ; Durgin, Gregory, Committee Member ; Li, Geoffrey, Committee Member ; Ingram, Mary Ann, Committee Member ; Stuber, Gordon, Committee Chair.
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Duo, Bin. "Polar Coding Schemes for Cooperative Transmission Systems." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14619.
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: In this thesis, a serially-concatenated coding scheme with a polar code as the outer code and a low density generator matrix (LDGM) code as the inner code is firstly proposed. It is shown that that the proposed scheme provides a method to improve significantly the low convergence of polar codes and the high error floor of LDGM codes while keeping the advantages of both such as the low encoding and decoding complexity. The bit error rate results show that the proposed scheme by reasonable design have the potential to approach a performance close to the capacity limit and avoid error floor effectively. Secondly, a novel transmission protocol based on polar coding is proposed for the degraded half-duplex relay channel. In the proposed protocol, the relay only needs to forward a part of the decoded source message that the destination needs according to the exquisite nested structure of polar codes. It is proved that the scheme can achieve the capacity of the half-duplex relay channel while enjoying low encoding/decoding complexity. By modeling the practical system, we verify that the proposed scheme outperforms the conventional scheme designed by low-density parity-check codes by simulations. Finally, a generalized partial information relaying protocol is proposed for degraded multiple-relay networks with orthogonal receiver components (MRN-ORCs). In such a protocol, each relay node decodes the received source message with the help of partial information from previous nodes and re-encodes part of the decoded message for transmission to satisfy the decoding requirements for the following relay node or the destination node. For the design of polar codes, the nested structures are constructed based on this protocol and the information sets corresponding to the partial messages forwarded are also calculated. It is proved that the proposed scheme achieves the theoretical capacity of the degraded MRN-ORCs while still retains the low-complexity feature of polar codes.
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Pendli, Pavan Kumar [Verfasser]. "Contribution of Modelling and Analysis of Wireless Communication for Safety related Systems with Bluetooth Technology / Pavan Kumar Pendli." Kassel : Kassel University Press, 2014. http://d-nb.info/1065688385/34.
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Walldén, Marcus, and Aylin Özkan. "A graph database management system for a logistics-related service." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205184.
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Higher demands on database systems have lead to an increased popularity of certain database system types in some niche areas. One such niche area is graph networks, such as social networks or logistics networks. An analysis made on such networks often focus on complex relational patterns that sometimes can not be solved efficiently by traditional relational databases, which has lead to the infusion of some specialized non-relational database systems. Some of the database systems that have seen a surge in popularity in this area are graph database systems. This thesis presents a prototype of a logistics network-related service using a graph database management system called Neo4j, which currently is the most popular graph database management system in use. The logistics network covered by the service is based on existing data from PostNord, Sweden’s biggest provider of logistics solutions, and primarily focuses on customer support and business to business. By creating a prototype of the service this thesis strives to indicate some of the positive and negative aspects of a graph database system, as well as give an indication of how a service using a graph database system could be created. The results indicate that Neo4j is very intuitive and easy to use, which would make it optimal for prototyping and smaller systems, but due to the used evaluation method more research in this area would need to be carried out in order to confirm these conclusions.Högre krav på databassystem har lett till en ökad popularitet för vissa databassystemstyper i några nischområden. Ett sådant nischområde är grafnätverk, såsomsociala nätverk eller logistiknätverk. Analyser på grafnätverk fokuserar ofta påkomplexa relationsmönster som ibland inte kan lösas effektivt av traditionella relationsdatabassystem, vilket har lett till att vissa specialiserade icke-relationella databassystem har blivit populära alternativ. Många av de populära databassystemen inom detta område är grafdatabassystem. Detta arbete presenterar en prototyp av en logistiknätverksrelaterad tjänst som använder sig av ett grafdatabashanteringssystem som heter Neo4j, vilket är det mest använda grafdatabashanteringssystemet. Logistiknätverket som täcks av tjänsten är baserad på existerande data från PostNord, Sveriges ledande leverantör av logistiklösningar, och fokuserar primärt på kundsupport och företagsrelaterad analys. Genom att skapa en prototyp av tjänsten strävar detta arbete efter att uppvisa vissa av de positiva och negativa aspekterna av ett grafdatabashanteringssystem samt att visa hur en tjänst kan skapas genom att använda ett grafdatabashanteringssystem. Resultaten indikerar att Neo4j är väldigt intuitivt och lättanvänt, vilket skulle göra den optimal för prototyping och mindre system, men på grund av den använda evalueringsmetoden så behöver mer forskning inom detta område utföras innan dessa slutsatser kan bekräftas.
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St, Germain Kenneth W. "Shipboard radio frequency and free space optics communications system using an airborne relay." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FStGermain.pdf.
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Rangavajjula, Santosh Bharadwaj. "Design of information tree for support related queries: Axis Communications AB : An exploratory research study in debug suggestions with machine learning at Axis Communications, Lund." Thesis, Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-16826.
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Context: In today's world, we have access to so much data than at any time in the past with more and more data coming from smartphones, sensors networks, and business processes. But, most of this data is meaningless, if it's not properly formatted and utilized. Traditionally, in service support teams, issues raised by customers are processed locally, made reports and sent over in the support line for resolution. The resolution of the issue then depends on the expertise of the technicians or developers and their experience in handling similar issues which limits the size, speed, and scale of the problems that can be resolved. One solution to this problem is to make relevant information tailored to the issue under investigation to be easily available. Objectives: The focus of the thesis is to improve turn around time of customer queries using recommendations and evaluate by defining metrics in comparison to existing workflow. As Artificial Intelligence applications can have a broad spectrum, we confine the scope with a relevance in software service and Issue Tracking Systems. Software support is a complicated process as it involves various stakeholders with conflicting interests. During the course of this literary work, we are primarily interested in evaluating different AI solutions specifically in the customer support space customize and compare them. Methods: The following thesis work has been carried out by making controlled experiments using different datasets and Machine learning models. Results: We classified Axis data and Bugzilla (eclipse) using Decision Trees, K Nearest Neighbors, Neural Networks, Naive Bayes and evaluated them using precision, recall rate, and F-score. K Nearest Neighbors was having precision 0.11, recall rate 0.11, Decision Trees had precision 0.11, recall rate 0.11, Neural Networks had precision 0.13, recall rate 0.11 and Naive Bayes had precision 0.05, recall rate 0.11. The result shows too many false positives and true negatives for being able to recommend. Conclusions: In this Thesis work, we have gone through 33 research articles and synthesized them. Existing systems in place and the current state of the art is described. A debug suggestion tool was developed in python with SKlearn. Experiments with different Machine Learning models are run on the tool and highest 0.13 (precision), 0.10 (f-score), 0.11 (recall) are observed with MLP Classification Neural Network.
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Choi, Gi Wan. "Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47721.
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In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands for higher data rates and seamless connectivity, one solution is to drastically increase the number of macro base stations in the conventional cellular architecture. However, this results in high deployment costs. Deploying low-power nodes such as relays that do not require a wired backhaul connection within a macrocell is one of cost-effective ways to extend high data rate coverage range. Relays are typically deployed to increase signal strength in poor coverage areas or to eliminate dead spots. But more importantly, relays provide a natural diversity, called cooperative diversity. In addition to a direct signal from a base station, extra copies of the same signal are forwarded from relays. Utilizing this diversity at the destination can yield significant performance enhancements. Thus, cooperative relay strategies need to be considered to enable high data rate coverage in a cost-effective manner.
In this dissertation, we consider a simple single-relay network and present low-complexity and power-efficient cooperative relay designs that can achieve low error rate. We first study decode-and-forward (DF) relay networks with a single antenna at each node, where the relay decodes the received signal and forwards the re-encoded information to the destination. In DF relay scheme, decoding at the relay is not perfect and the error-propagation phenomenon is a detrimental problem, preventing the destination from collecting the cooperative diversity. To enable cooperative diversity in DF relay networks, we adopt link-adaptive power-scaling relay strategies where the relay scales the transmission power of the re-encoded signal based on the reliability of the source-relay link. We generalize power-profile designs and analyze the diversity order enabled by the general power-profile designs. We provide necessary and sufficient conditions for the designs to enable full cooperative diversity at the destination.
In the second part of this dissertation, we extend the power-scaling relay strategy to DF multi-input multi-output (MIMO) relay networks, where multiple antennas are adopted at each node, and show that full cooperative diversity can also be achieved here. To collect spatial diversity provided by multiple antennas without using maximum-likelihood equalizers (MLEs) or near-ML detectors which exhibit high complexity, channel-controlled automatic repeat request (CC-ARQ) scheme is developed for DF MIMO relay networks to enable spatial diversity with linear equalizers (LEs) maintaining low-complexity. We also show that joint cooperative and spatial diversity can be achieved at the destination when the power-scaling strategy and the CC-ARQ with LEs are combined.
Finally, amplify-and-forward (AF) MIMO relay designs, where the relay simply amplifies the received signal and forwards it to the destination, are studied with consideration of peak-power constraints at the relay. One practical concern for AF relaying is that the output signal at the relay may suffer from large peak-to-average power ratio (PAR), which may cause nonlinear distortion and/or saturation in the transmitted signal due to the limited linear range of power amplifiers. Thus, we first investigate peak-power constrained power-scaling strategies and find a sufficient condition to enable joint cooperative and spatial diversity at the destination. Based on this study, we propose simple and practical AF MIMO relay designs with peak-power constraint at the relay. CC-ARQ is also applied to AF MIMO relay networks to reduce the decoding complexity.
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Olson, Kristin. "Water carved out the mountains. Policy communication of Engaged Buddhists related to international development cooperation." Thesis, Malmö högskola, Fakulteten för kultur och samhälle (KS), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-22363.
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Not applicable.The study “Water carved out the mountains. Policy communication of Engaged Buddhists related to international development cooperation” contributes to an understanding of development from perspectives of non-denominational action among so called Engaged Buddhists. Departing from qualitative interviews with nine leaders of socially engaged organizations from five Asian countries, the systemic programming resulting from their ideals are compared to key principles and programming of international development cooperation. Responding to the question:”What policy ideals shape the development programming, and can these be linked to forms of power and the rights-based approach?” this inter-disciplinary and multi-sited study feeds into the increased interest in faith-based expressions within the general public sphere, and specifically in the development industry. Guided by the ontology of critical realism, a mixed method is used shaped by qualitative interviews and participatory observations, enabling both analysis of meanings and development programming. Based on their views on Buddhist ethics and practices, the leaders address development topics common today. Policies expressed are placed within a communication culture for change, yet not necessarily by conventional confrontational advocacy modes. Diverse understandings are at play, such as how to convey meanings of “kindness”. Although not referring to concepts common within the social and cultural structures of contemporary international development cooperation, the actors develop methods based on principles of participation in particular and the work today can also be related to other principles of the Human Rights Based Approach. The policies and programming are linked to invisible, informal and formal forms of power although informants refer to interpretations of compassion, inter-relatedness and non-dualism, among other.From a perspective of development cooperation, a hypothetical argument is advanced suggesting that the informants do not differ at substantial level related to their understanding and practice of Buddhism or their general approaches to development topics, as much as they differ regarding their approach to programming aimed at influencing forms of power. The common criticism of Buddhists not addressing power can then for this group be nuanced, and indicatively suggested not to be valid regarding invisible and informal power, but rather regarding formal power.Academic fields: Communication for development with reference to sociology of religion, political science, global studies and multi-sited ethnography.Key words: Engaged Buddhism, Civil Society Organizations, Faith-Based Organizations, Human Right Based Approach, participation, complexity/systemic approaches, power, Thich Nhath Hanh, Sister Chan Khong, Sulak Sivaraksa, Bikkhuni Dhammananda, A.T. Ariyaratne, Sarvodaya.
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Ozgur, Utku. "Development of a Remotely Accessible Wireless Testbed for Performance Evaluation of AMI Related Protocols." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3177.
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Although smart meters are deployed in many countries, the data collection process from smart meters in Smart Grid (SG) still has some challenges related to consumer privacy that needs to be addressed. Referred to as Advanced Metering Infrastructure (AMI), the data collected and transmitted through the AMI can leak sensitive information about the consumers if it is sent as a plaintext.
While many solutions have been proposed in the past, the deployment of these solutions in real-life was not possible since the actual AMIs were not accessible to researchers. Therefore, a lot of solutions relied on simulations which may not be able to capture the real performance of these solutions. In this thesis, two 802.11s wireless mesh-based SG AMI network testbeds are developed with Beaglebone Black and Raspberry Pi 3 boards to provide a baseline for the simulations. The Raspberry Pi 3 testbed is also configured to be remotely accessible.
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Advaita, Advaita, and Mani Meghala Gali. "Performance Analysis of a MIMO Cognitive Cooperative Radio Network with Multiple AF Relays." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13643.
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With the rapid growth of wireless communications, the demand for the various multimedia services is increasing day by day leading to a deficit in the frequency spectrum resources. To overcome this problem, the concept of cognitive radio technology has been proposed which allows the unlicensed secondary user (SU) to access the licensed spectrum of the primary user (PU), thus improving the spectrum utilization. Cooperative communications is another emerging technology which is capable of overcoming many limitations in wireless systems by increasing reliability and coverage. The transmit and receive diversity techniques such as orthogonal space–time block codes (OSTBCs) and selection combining (SC) in multiple-input multiple-output (MIMO) cognitive amplify and forward relay networks help to reduce the effects of fading, increase reliability and extend radio coverage. In this thesis, we consider a MIMO cognitive cooperative radio network (CCRN) with multiple relays. The protocol used at the relays is an amplify and forward protocol. At the receiver, the SC technique is applied to combine the signals. Analytical expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-noise ratio (SNR) are derived. On this basis, the performance in terms of outage probability is obtained. Mathematica has been used to generate numerical results from the analytical expressions. The system model is simulated in MATLAB to verify the numerical results. The performance analysis of the system model is hence done in terms of outage probability.
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Garcia, Gilbert O. Joseforsky David C. "Transformational communications architecture for the Unit Operations Center (UOC) ; Common Aviation Command and Control System (CAC2S) ; and Command and Control on-the-move Network, Digital over-the-horizon Relay (CoNDOR) /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FGarcia%5FJoseforsky.pdf.
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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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Timilsina, Santosh. "Physical Layer Security in Training-Based Single-Hop/Dual-Hop Massive MIMO Systems." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2376.
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The broadcast nature of wireless medium has made information security as one of the most important and critical issues in wireless systems. Physical layer security, which is based on information-theoretic secrecy concepts, can be used to secure the wireless channels by exploiting the noisiness and imperfections of the channels. Massive multiple-input multiple-output (MIMO) systems, which are equipped with very large antenna arrays at the base stations, have a great potential to boost the physical layer security by generating the artificial noise (AN) with the exploitation of excess degrees-of-freedom available at the base stations. In this thesis, we investigate physical layer security provisions in the presence of passive/active eavesdroppers for single-hop massive MIMO, dual-hop relay-assisted massive MIMO and underlay spectrum-sharing massive MIMO systems. The performance of the proposed security provisions is investigated by deriving the achievable rates at the user nodes, the information rate leaked into the eavesdroppers, and the achievable secrecy rates. Moreover, the effects of active pilot contamination attacks, imperfect channel state information (CSI) acquisition at the base-stations, and the availability of statistical CSI at the user nodes are quantified. The secrecy rate/performance gap between two AN precoders, namely the random AN precoder and the null-space based AN precoder, is investigated. The performance of hybrid analog/digital precoding is compared with the full-dimensional digital precoding. Furthermore, the physical layer security breaches in underlay spectrum-sharing massive MIMO systems are investigated, and thereby, security provisions are designed/analyzed against active pilot contamination attacks during the channel estimation phase. A power-ratio based active pilot attack detection scheme is investigated, and thereby, the probability of detection is derived. Thereby, the vulnerability of uplink channel estimation based on the pilots transmitted by the user nodes in time division duplexing based massive MIMO systems is revealed, and the fundamental trade-offs among physical layer security provisions, implementation complexity and performance gains are discussed.
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Rodr00EDguez, Eric Noel. "Exploration of K-5 Teacher Decision-Making Related to Student Use of Technology." ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/7731.
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Student technology literacy is critical for success in today’s world; however, little is understood about how teachers make the decision for students to use technology for learning due to limited empirical research on the topic of teacher decision-making regarding student use of information communication technologies (ICT). The purpose of this generic qualitative study was to explore the decision-making process of kindergarten to Grade 5 (K-5) teachers regarding implementation of ICT for student use at varying levels. The framework for this study comprised the substitution augmentation modification redefinition model and the technology acceptance model. The research questions focused on how teachers have students use technology in the classroom, the influences on teacher decision-making to have students use technology, and how decision-making compared among K-5 teachers whose students use technology at varying levels of implementation. Interview data were collected from 12 teachers at a public-school district in the southern United States that were analyzed using 2 cycles of coding: a priori and emergent. Key findings were that (a) teachers have students use technology primarily at substitution and augmentation levels, (b) teacher decisions were influenced mostly by student technology readiness, and (c) teachers who used technology at redefinition levels had different factors for decision-making. The results of this study may contribute to positive social change by creating a deeper understanding of the decision-making process of teachers, which can positively affect student engagement, academic growth, and lay the foundations for technology literacy for students.
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Kaufmann, Tobias [Verfasser]. "Brain-Computer Interfaces Based on Event-Related Potentials: Toward Fast, Reliable and Easy-To-Use Communication Systems for People with Neurodegenerative Disease / Tobias Kaufmann." München : Verlag Dr. Hut, 2013. http://d-nb.info/1045988146/34.
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Basharati, Sarhad. "MIMO and Relay Systems Based on Multi-Amplitude Minimum Shift Keying." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8491.
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This thesis describes the use of a multi-amplitude minimum shift keying (MAMSK) signal in various types of wireless communication system. A MAMSK signal is a bandwidth efficient modulation scheme obtained by superimposing ℳ minimum shift keying (MSK) signals with unequal amplitudes. The overall phase of a MAMSK signal is controlled by the phase of the largest component MSK signal which allows the use of a low-complexity differential detector. A closed form expression for the average bit error rate (BER) for coherent detection of an MAMSK in AWGN is derived and is shown to achieve the same BER as that of square constellation quadrature amplitude modulation (QAM) with the same average transmit power.
We describe the design and implementation of a STBC-based MIMO radio system in conjunction with MAMSK modulation. The proposed system provides high capacity data transmission by carrying information not only in the phases but also in the amplitude. Despite using a simple MAMSK differential receiver the system achieves performance within 1 dB of coherent detection. The existing MSK modems in conjunction with STBC could easily be modified to construct the proposed system.
The MAMSK modulation scheme is extended to a multiuser relaying network where two nodes cooperate in a half-duplex environment to achieve diversity gain. The cooperative scheme is based on superposition modulation using a decode-and-forward (DF) strategy. In the proposed scheme, each node simultaneously transmits its own and the relayed signals by superimposing one on the other. A MAMSK signal is an excellent choice for this type of cooperative communication due its being obtained by a superposition technique. The proposed system exploits the overall phase of a MAMSK signal which allows differential detection and as a result it provides the lowest decoding complexity and memory requirements among the existing superposition based cooperation schemes. The performance of the system is evaluated by simulation, where it is shown that the MAMSK cooperative system outperforms a conventional DF scheme in terms of both power and bandwidth efficiency.
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Bentley, Grace Ann. "Neurophysiological Correlates of the Critical Bandwidth in the Human Auditory System." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5619.
Full textAbstract:
The critical bandwidth (CBW) is an auditory phenomenon that has been used to study various aspects of auditory processing, including auditory masking, complex tone processing, and loudness perception. Although the psychoacoustic aspects of the CBW have been well studied, the underlying neurophysiology of the CBW has not been as thoroughly examined. The current study examined the neurophysiology of the CBW in young adults, as well as loudness perception in response to the CBW. Auditory stimuli consisting of complex tones of varying bandwidths were presented to 12 individuals (6 male and 6 female, ages 18-26 years). Complex tones were presented around center frequencies (CFs) of 250, 500, 1000, and 3000 Hz at bandwidths of 2, 5, 8, 10, 20, 50, 100, 200, 500, 1000, and 2000 Hz. Participants made loudness perception judgments while electroencephalography measured and recorded components of the event related potentials (ERPs) in response to the acoustic stimuli. Reaction time (RT) was recorded for each behavioral response, and the latencies of the N1, P2, C3, and C4 components of the ERPs were obtained. The results showed that RT increased with increasing bandwidth followed by a decrease in RT corresponding approximately with the CBW. This indicated that participants perceived a change in loudness at bandwidths greater than the CBW. Significant differences, p < .05, in RT were observed in bandwidths of 5 Hz and greater, although there was not complete consistency in this observation across all CFs and bandwidths. No significant critical band-like behavior amongst ERP latencies was observed. The results indicated that responses to acoustic stimuli originating in the superior temporal gyrus progressed to areas of higher neural function in the mid-temporal lobe. It was observed that each response must be processed temporally and independently to determine if a frequency difference is present for each stimulus. This observation is significant because this type of processing had not been identified prior to the current study.
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Lindkvist, Hannes. "Participation for Sustainable Urban Freight Transport Systems : A Case Study of Freight Receivers in the City of Gothenburg." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324573.
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This thesis is a case study research that look into the difficulty in engaging freight receivers in initiatives related to urban freight transport. The aim of the paper is to investigate how participatory processes could be formed for more successful outcomes and how the freight receivers could become more engaged in the processes. By conducting a qualitative research where primarily interviews with freight receivers and other concerned stakeholder were made, it was possible to distinguish differences and similarities in views and attitudes toward participation in freight related initiatives. The interviewed freight receivers were located in two different areas in the central business district in the city of Gothenburg, Sweden. In one area, the freight receivers have been included in discussions with the traffic and public transport authority regarding a newly implemented restriction for heavy freight vehicles, and thus have experience with participatory processes. These results show that the freight receivers appreciate the possibility to be a part of the discussion even though they are sceptic towards their possibility to influence on decisions. In the other area, the authority is planning on potentially implement the same restrictions, but as they have not started this process, no stakeholders have yet been included in discussions. Thus, the expectations and attitude towards participation in such a process could be studied among freight receivers in this area. Results in this area show that medium sized business, based on turnover, are more enthusiastic in participating meanwhile smaller business and businesses that are part of a chain store or a franchise are less interested in participating. By comparing the views and opinions between these groups with the interview with the authorities, results show that freight receivers and the traffic and public transport authority in Gothenburg have similar views on the importance of participatory processes, but they differ in their views on what influence the freight receivers have in these processes. By analysing the results with the theoretic concepts of participation, engagement and communication it was possible to identify issues in the case that must be considered in order to establish more rewarding participatory processes. It is concluded that freight receivers must be involved already in the process of defining the problem with urban freight transport to close the gap between how the freight receivers and the authorities experience the participatory process. This would enable finding solutions that considerall interests and thus have higher chance of long-lasting implementation rather that creating conflicts on power relations. Further it is stated that with the help of a combination of a scalon plan, quality circle and representative participation is possible to create an altruistic value in participating which could increase the will to engage in participatory processes and creating more sustainable urban freight transport systems.
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Lo, Caleb K. 1981. "Relay-assisted communication : fundamental limits and selection strategies." 2008. http://hdl.handle.net/2152/18163.
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Wireless communication continues to make a profound impact upon our daily lives. The oft-touted benefits of high data rates and improved reliability via wireless communication are limited by its inherent drawbacks, including path loss, fading and interference. One promising strategy for overcoming these problems is to deploy nodes in the region between a transmitter and its intended receiver. These intermediate nodes can improve communication for this transmitter-receiver pair by receiving a transmitted message, processing it and relaying the processed output to the receiver. This transmission strategy, known as relay-assisted communication, can be especially beneficial when the transmitter-receiver pair are either separated by a large distance or when a large obstruction blocks the path between them. In a reasonably dense network, several relays may be available to assist a particular transmitter-receiver pair. Deciding which relays should forward the transmitted message is actually quite difficult. For example, the relay with the best physical-layer channel gain to the destination may also be running low on battery power. Another relay may have a good physical-layer channel gain to the destination and a reasonable amount of remaining battery power, but its queue may be full of messages from other transmitters, so it cannot forward a newly arrived message within a given delay constraint. Thus, optimal relay selection entails carefully balancing all system parameters, which is prohibitively complex in current wireless systems. This dissertation provides novel results for dealing with the relay selection problem in two distinct types of wireless systems. First, several selection algorithms are designed for single-antenna wireless networks, including a decentralized random access-based strategy and centralized methods that are based on throughput maximization and downlink user scheduling. Second, selection algorithms based on transmission hop length are designed for multipleantenna wireless networks. The presented strategies for both single-antenna and multiple-antenna relaying are highly intuitive, as they allow for concise descriptions, making them amenable to practical implementation. Also, the presented strategies illustrate the importance of application-specific design, since each of them yields good performance by focusing on a small set of system parameters. For example, observed latency is of paramount importance for wireless networks that support a significant level of video traffic.text
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Shao, Yunlong. "Precoding for MIMO full-duplex relay communication systems." Thesis, 2018. https://dspace.library.uvic.ca//handle/1828/9213.
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Multiple antennas combined with cooperative relaying, called multiple-input multiple-output (MIMO) relay communications, can be used to improve the reliability and capacity of wireless communications systems. The precoding design is crucial to realize the full potential of MIMO relay systems. Full-duplex (FD) relay communications has become realistic with the development of effective loop interference (LI) cancellation techniques. The focus of this dissertation is on the precoding design for MIMO FD amplify-and-forward (AF) relay communication systems. First, the transceiver design for MIMO FD AF relay communication systems is considered with residual LI, which will exist in any FD system. Then the precoding design is extended to two-way MIMO FD relay communication systems. Iterative algorithms are presented for both systems based on minimizing the mean squared error (MSE) to obtain the source and relay precoders and destination combiner.Finally, the precoding design for MIMO FD relay communication systems with multiple users is investigated.Two systems are examined, namely a multiuser uplink system and a multiuser paired downlink system. By converting the original problems into convex subproblems, locally optimal solutions are found for these systems considering the existence of residual LI. The performance improvement for the proposed FD systems over the corresponding half-duplex (HD) systems is evaluated via simulation.Graduate
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MinhPhuong, Do Thi, and 杜氏明芳. "Relay Selection for D2D Communication Systems inCellular Networks." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/07845248640906555273.
Full textAbstract:
碩士國立成功大學
工程科學系
102
Nowadays, the explosive development on the number of mobile user and multimedia services cause a severe traffic overload problem in the cellular network. Data offloading in the Third-Generation Partnership Project (3GPP) is defined as critical scheme to cope with this issue. Furthermore, device-to-device (D2D) communications have been considered as a new data-offloading solution. The D2D communications underlay cellular networks infrastructure reduces the radio access network load and the core network load. Device-to-device (D2D) communication commonly refers to a technology that enables devices to communicate directly without access points, base stations, and wireless operators. With the application of specific rules and strategies, D2D communications decrease the mobile network load and increase the spectral efficiency. Moreover, relay assisted transmissions are considered in this thesis to efficiently improve the performance of relay assisted D2D communications when D2D user equipments (UEs) are too far away from each other or the quality of the D2D channel is not good enough for direct communications. Thereafter, the relay selection issues on D2D communication in cellular network is studied in this thesis. Finally, a centralized relay selection method for relay assisted D2D communication systems is proposed in this thesis.
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Yen, Chin-Yi, and 顏進益. "Channel Estimation for Relay Based Cooperative Communication Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/71327446104476554469.
Full textAbstract:
碩士淡江大學
電機工程學系碩士班
96
Although many researches on relay-based cooperative coherent communication systems have shown that the benefits of spatial diversity, saying cooperative diversity, can be achieved as the multi-antenna technologies do, the analyses primarily rely on the assumption that the perfect channel state information (CSI) is available at the receiver. In practical scenarios, the CSI has to be estimated and the effect of imperfect CSI on system performance needs to be analyzed. In this thesis, we study the channel estimation problem for amplify-and-forward (AF) relay-based cooperative communication systems. For AF transmission scheme, the relay amplifies the received signal from the source by a fixed or variable gain and forwards it to the destination. Depending on the mobility of the relay, we consider both the fixed-to-mobile channel model and the mobile-to-mobile channel model. To facilitate the channel estimation task, we employ the pilot symbol assisted modulation (PSAM) and consider the linear minimum mean-squared error (LMMSE) as the estimation criterion. Computer simulations are conducted to illustrate the influences of the imperfect CSI on the performance of AF relay-based communication systems.