Dissertations / Theses on the topic 'Channel reciprocity'
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Eichenberg, Neal (Neal Thomas). "Simulating the use of channel reciprocity in laser communication system operations to improve quality of service through varying atmospheric conditions." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118050.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 68-73).
This project's goal was to develop a simulation model to conduct design analysis and to illustrate the positive and negative aspects of utilizing channel reciprocity versus interleaving. There were three project objectives. The first was to create a numerical model of a laser communications system that included either channel reciprocity or interleaving to mitigate the effects of atmospheric turbulence. This model was implemented in MATLAB* and Simulink*. The second task integrated the model with a graphical user interface (GUI), which provides the user a choice of different configurations and solutions based on the user's design specifications. For example, the user may elect to sweep the scintillation index to see the impact that a variety of turbulence levels have on the bit error rate (BER). The user has the ability to sweep each variable and observe the performance. With this model, the user objectively compares optical communication systems with and without the utilization of channel reciprocity. Scenarios may be run to determine which settings provide the most optimized quality of service (QoS) metrics. The third goal was to test the QoS of both cases against theoretical values in order to check the validity of the MATLAB and Simulink models. These three objectives were met, and channel reciprocity techniques were determined to be an excellent choice for specific conditions. Given the same transmit power, channel reciprocity with and without forward error correction (FEC) achieves a far lower BER than a system that utilizes interleaving and FEC. This low BER is achieved by setting the gating threshold for the transmission of information well above the signal to noise (SNR) requirement. Latency issues could arise, but they are managed in this model by setting the buffer input to output ratio such that the output is always at least twice the input. Although reciprocity without FEC is not a viable solution for all scenarios, it was found that it makes sense to utilize reciprocity without FEC for some cases. However, reciprocity with FEC is recommended for all cases that have round trip durations that are less than the coherence time.
by Neal Eichenberg.
S.M.
Kokar, Yvan. "Études de la mise en oeuvre matérielle d’une transmission sans fil combinant retournement temporel et OFDM." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0031/document.
Full textThe spectacular growth of wireless communications systems has led to a sharp increase in data traffic, which should continue to grow over the next few years. The future generation of cellular networks (5G) must be able to support this growth of traffic, while presenting reduced energy consumption compared to existing networks. Among the different studied technologies, time reversal (TR) is a serious candidate to meet these constraints. Indeed, the numerous theoretical studies on the subject have shown that the combination of TR and OFDM has interesting performance, specifically thanks to its temporal compression and spatial focusing properties. However, the assumptions made in the theoretical studies are not always compatible with the practical implementation of a real system. The objective of this thesis is to propose solutions to unrealistic theoritical hypotheses, in order to implement them in a real hardware prototype combining TR and OFDM in a MISO context. First, the implementation of the channel estimation at the transmitter side, and the synchronization of the MISO TR-OFDM system is studied. Then, a calibration solution at the transmitter is proposed to compensate for the non-reciprocal nature of the baseband propagation channel. All these solutions as well as the focusing properties of TR are validated by experimental measurements using the developed prototype. Finally, the implementation of the first TR prototype of spatial modulation at the receiver side is presented
Smets, Michael. "Doing deals in a global law firm : the reciprocity of institutions and work." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:48185e10-6537-4305-8af3-8ccb27a07ebb.
Full textKerimov, Farhad. "Democratic pluralism as engagement and encounter : asymmetric reciprocity, reflexivity, and agonism." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/23298.
Full textchi, coppinger t. "Reciprocity Among All Things: A Personal Endeavor in the Environmental Crisis." Ohio University Honors Tutorial College / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1461341953.
Full textIniesta-Arandia, Irene, Federica Ravera, Stephanie Buechler, Isabel Díaz-Reviriego, María E. Fernández-Giménez, Maureen G. Reed, Mary Thompson-Hall, et al. "A synthesis of convergent reflections, tensions and silences in linking gender and global environmental change research." SPRINGER, 2016. http://hdl.handle.net/10150/622830.
Full textLefort, Sandrine. "Haivaro Fasu Modernity : embodying, Disembodying and Re-embodying Relationships." Thesis, Paris, EHESS, 2017. http://www.theses.fr/2017EHES0087.
Full textThis thesis analyses ways in which the relationships of fatherhood, brotherhood, conjugality, gender and otherness that build the lifeworld of Fasu people of Haivaro (in the northwestern lowlands of Gulf Province, Papua New Guinea) have been and continue to be renegotiated and reconfigured in the context of their engagement with multiple expressions of modernity, in particular with a logging company operating on their land. I show how these transformations entail processes of embodiment, disembodiment and re-embodiment of those relations
Hoof, Pomme van. "Triggering a gift economy." Thesis, Konstfack, Experience Design, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-4191.
Full textNordin, Åsa. "Relationer i ett samiskt samhälle : en studie av skötesrensystemet i Gällivare socken under första hälften av 1900-talet." Doctoral thesis, Umeå universitet, Arkeologi och samiska studier, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-56797.
Full textdigitalisering@umu
Gopala, Kalyana. "Multiple Antenna Communications for 5G." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS352.
Full textTime Division Duplexing (TDD) Massive Multiple Input Multiple Output (MaMIMO) with a massive number of base station (BS) antennas relies on channel reciprocity to obtain Channel State Information at Transmitter (CSIT). However the overall end to end digital channel is not reciprocal due to the presence of Transmit (Tx) and Receive (Rx) chains which need to be corrected using calibration factors. Our work provides a simple and elegant expression of the Cramer Rao Bound (CRB) for calibration parameter estimation. We provide analysis for the existing least squares approaches and propose optimal algorithms to estimate the calibration parameters. We also consider beamforming for a rapidly time-varying point to point MIMO link. In an Orthogonal Frequency Division Multiplexing (OFDM) sytem, this results in inter-carrier interference (ICI). With an assumption of linear channel variation across the OFDM symbol, it is observed that the beamformer design problem is similar to that of a MIMO Interfering Broadcast Channel (IBC) beamforming design. The beamformer design takes into account receive windowing using the excess cyclic prefix and the window is jointly designed with the Tx beamformer. In addition to full CSIT, we also investigate partial CSIT approaches that maximize Expected Weighted Sum Rate (EWSR) where the Tx has only partial knowledge of the channel. First, we use a large system approximation that also works well for a small number of Tx and Rx antennas to derive the beamformers. In our work, we also analyze the possibility of using the Expected-signal- expected-interference-WSR metric instead of the EWSR. Finally, experimental results on the Eurecom MaMIMO testbed are presented
Kouassi, Boris Rodrigue. "Stratégies de coopération dans les réseaux radio cognitif." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00921559.
Full textHaile, Senay. "Investigation of Channel Reciprocity for OFDM TDD Systems." Thesis, 2009. http://hdl.handle.net/10012/4785.
Full textLien, Che-Ying, and 連哲影. "Calibrations for channel reciprocity in MU-MIMO systems." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9xghee.
Full textMarques, João Diogo Madeira Cristina. "Jamming based on channel reciprocity for secrecy in wireless communications." Master's thesis, 2017. http://hdl.handle.net/10316/83111.
Full textNas últimas décadas as comunicações sem fios tiveram um crescimento enorme. Hoje em dia, a maioria das tarefas diárias necessitam da utilização de um dispositivo que recorra a uma comunicação sem fios. Por isso, criou-se uma necessidade de aumentar a segurança nestas comunicações. Recentemente, as técnicas de segurança na camada física têm gerado interesse, pois, permitem complementar, através de uma abordagem diferente, os protocolos de segurança já existente em outras camadas lógicas. Nesta dissertação foi implementado, um método de segurança na camada física num sistema Orthogonal Frequency Division Multiplexing (OFDM). Este método utiliza as características do canal para codificar e descodificar a mensagem transmitida, tendo por base o princípio da reciprocidade do canal que permite obter uma fonte de informação aleatória comum entre transmissor e recetor legítimo. As estimações de canal feitas são utilizadas para criar sinais de interferência que irão mudar a fase dos símbolos modulados e, consequentemente, proteger a mensagem transmitida. O sistema OFDM com o método de segurança foi desenvolvido utilizando a framework GNU Radio. Além disso, cada módulo constituinte do sistema pode ser utilizado com plataformas de rádio definido por software (SDR) para testes em ambiente real. Os testes realizados foram feitos considerando um cenário baseado no canal wiretap onde existem dois utilizadores legítimos (Alice e Bob) e um ilegítimo (Eve); no modelo original a Alice envia uma mensagem para o Bob enquanto a Eve tenta intercetá-la, além disso é assumido que as condições de transmissão do Bob são mais vantajosas do que as da Eve. As simulações realizadas consideraram diferentes condições de canal de forma a determinar os efeitos no desempenho do sistema. Além disso, foi realizada uma experiência em condições reais com SDR para validar a implementação. Os resultados obtidos, constituem evidência que o método usado pode aumentar a segurança mesmo quando o canal ilegítimo tem boas condições, embora, alguma fiabilidade seja comprometida. Isto pode ser importante nas futuras redes de dispositivos de baixa complexidade, como na Internet das coisas, onde é difícil a implementação de técnicas complexas de encriptação, e como os métodos de segurança na camada física podem ter um papel importante.
Wireless communications had an impressive growth in the last decades. Nowadays, most daily tasks require the use of a device that resorts to wireless communications. For these reasons, a necessity to increase security in this type of communications has emerged. Recently, physical-layer security techniques have raised interest, since they allow complementing, through a different approach, the already existent security protocols in higher logical layers. In this dissertation, a method of physical layer security is implemented in an Orthogonal Frequency Division Multiplexing (OFDM) system. This method uses the channel characteristics to encode and decode the transmitted message. Taking as foundation the channel reciprocity principle it grants a common source of random information between the legitimate transmitter and receiver. The channel estimations are used to create a jamming signal that, when applied to the transmitted signal, will shift the modulated symbols phase, and, therefore, protect the message. The OFDM system with the secrecy method was developed using the GNU Radio framework. Also, each module of the built system can be used with Software Defined-Radio (SDR) platforms for testing in a real world environment. Simulation tests were conducted considering a scenario based on the wiretap channel where there are two legitimate users (Alice and Bob) and an illegitimate eavesdropper (Eve); in the original wiretap model Alice sends a message to Bob while Eve tries to intercept it, where it is also assumed that, Bob's reception condition is advantageous over Eve's. The conducted simulations have considered different kinds of channel conditions to determine the effects on the system performance. Also, an actual real world environment experiment with SDR was made. With the obtained results, it was shown that the employed method can increase security even in a configuration with an illegitimate channel with good conditions, although, some reliability may be compromised. The proposed technique may be important for future networks composed of low capability devices, such as in the Internet of Things, where may be difficult to implement complex encryption techniques, and how physical-layer security methods may play an important role.
Vairavanathan, Vinujanan. "FDTD Characterization of Antenna-channel Interactions via Macromodeling." Thesis, 2010. http://hdl.handle.net/1807/24644.
Full textGuo, Yujian. "Underwater wireless optical communication system under reciprocal turbulence." Thesis, 2018. http://hdl.handle.net/10754/629861.
Full textLouw, Gerrit Johannes. "Die manifestasie van organisasietraagheid." 2001. http://hdl.handle.net/10500/17243.
Full textSummaries in English and Afrikaans
Key terms in English and Afrikaans
Die doel van die studie was om organisasietraagheid as stremmende fenomeen te konseptualiseer en die manifestasie daarvan te ondersoek binne 'n tipiese werkorganisasie. Aandag is gegee aan organisasietransformasie binne die raamwerk van 'n diagnostiese model vir organisasie- en individuele ontwikkeling. Die empiriese studie bevestig die manifestasie van organisasietraagheid ten opsigte van die teikenorganisasie. Resultate bevestig dat respondente ten gunste is van veranderingsinisiatiewe, maar ondergeskiktes toon 'n emstige behoefte aan leierskap. Dit blyk ook dat die organisasie nie die vermoe het om vinnig op omgewingsveranderings te reageer nie. Gesonde bestuurspraktyke word nie gevolg nie en kreatiwiteit word nie aangemoedig nie. By ondergeskiktes bestaan ook twyfel oor veranderingsagente se vermoe om verandering te fasiliteer.
The purpose of the study was to conceptualise organisation inertia as a retarding phenomenon and to investigate its manifestation within a typical work organisation. Attention was given to organisational and individual development within the framework of a diagnostic model. The empirical study focussed on the manifestation of organisational inertia within the target organisation. Results confirmed that respondents are in favour of change initiatives but that the stimulation thereof do not exist. Subordinates are not encouraged to show creativity. The organisation demonstrates an incapability to respond to environmental changes and reflects a non-existence of healthy management practices. Little trust exists in the capability of change agents to facilitate change.
Economics and Management Sciences
M.A. (Industrial Psychology)