1,892 research outputs found
Performance enhancement solutions in wireless communication networks
In this dissertation thesis, we study the new relaying protocols for different wireless network systems. We analyze and evaluate an efficiency of the transmission in terms of the outage probability over Rayleigh fading channels by mathematical analyses. The theoretical analyses are verified by performing Monte Carlo simulations.
First, we study the cooperative relaying in the Two-Way Decode-and-Forward (DF) and multi-relay DF scheme for a secondary system to obtain spectrum access along with a primary system. In particular, we proposed the Two-Way DF scheme with Energy Harvesting, and the Two-Way DF Non-orthogonal Multiple Access (NOMA) scheme with digital network coding. Besides, we also investigate the wireless systems with multi-relay; the best relay selection is presented to optimize the effect of the proposed scheme. The transmission protocols of the proposed schemes EHAF (Energy Harvesting Amplify and Forward) and EHDF (Energy Harvesting Decode and Forward) are compared together in the same environment and in term of outage probability. Hence, with the obtained results, we conclude that the proposed schemes improve the performance of the wireless cooperative relaying systems, particularly their throughput.
Second, we focus on investigating the NOMA technology and proposing the optimal solutions (protocols) to advance the data rate and to ensure the Quality of Service (QoS) for the users in the next generation of wireless communications. In this thesis, we propose a Two-Way DF NOMA scheme (called a TWNOMA protocol) in which an intermediate relay helps two source nodes to communicate with each other. Simulation and analysis results show that the proposed protocol TWNOMA is improving the data rate when comparing with a conventional Two-Way scheme using digital network coding (DNC) (called a TWDNC protocol), Two-Way scheme without using DNC (called a TWNDNC protocol) and Two-Way scheme in amplify-and-forward(AF) relay systems (called a TWANC protocol).
Finally, we considered the combination of the NOMA and physical layer security (PLS) in the Underlay Cooperative Cognitive Network (UCCN). The best relay selection strategy is investigated, which uses the NOMA and considers the PLS to enhance the transmission efficiency and secrecy of the new generation wireless networks.V tĂ©to dizertaÄnĂ prĂĄci je provedena studie novĂœch pĆenosovĂœch protokolĆŻ pro rĆŻznĂ© bezdrĂĄtovĂ© sĂĆ„ovĂ© systĂ©my. S vyuĆŸitĂm matematickĂ© analĂœzy jsme analyzovali a vyhodnotili efektivitu pĆenosu z hlediska pravdÄpodobnosti vĂœpadku pĆes RayleighĆŻv kanĂĄl. TeoretickĂ© analĂœzy jsou ovÄĆeny provedenĂœmi simulacemi metodou Monte Carlo.
Nejprve doĆĄlo ke studii kooperativnĂho pĆenosu ve dvoucestnĂ©m dekĂłduj-a-pĆedej (Two-Way Decode-and-ForwardâTWDF) a vĂcecestnĂ©m DF schĂ©matu s vÄtĆĄĂm poÄtem pĆenosovĂœch uzlĆŻ pro sekundĂĄrnĂ systĂ©m, kdy takto byl zĂskĂĄn pĆĂstup ke spektru spolu s primĂĄrnĂm systĂ©mem. KonkrĂ©tnÄ jsme navrhli dvoucestnĂ© DF schĂ©ma se zĂskĂĄvĂĄnĂm energie a dvoucestnĂ© DF neortogonĂĄlnĂ schĂ©ma s mnohonĂĄsobnĂœm pĆĂstupem (Non-orthogonal Multiple AccessâNOMA) s digitĂĄlnĂm sĂĆ„ovĂœm kĂłdovĂĄnĂm. KromÄ toho rovnÄĆŸ zkoumĂĄme bezdrĂĄtovĂ© systĂ©my s vÄtĆĄĂm poÄtem pĆenosovĂœch uzlĆŻ, kde je pĆĂtomen vĂœbÄr nejlepĆĄĂho pĆenosovĂ©ho uzlu pro optimalizaci efektivnosti navrĆŸenĂ©ho schĂ©matu. PĆenosovĂ© protokoly navrĆŸenĂœch schĂ©mat EHAF (Energy Harvesting Amplify and Forward) a EHDF(Energy Harvesting Decode and Forward) jsou spoleÄnÄ porovnĂĄny v identickĂ©m prostĆedĂ z pohledu pravdÄpodobnosti vĂœpadku. NĂĄslednÄ, na zĂĄkladÄ zĂskanĂœch vĂœsledkĆŻ, jsme dospÄli k zĂĄvÄru, ĆŸe navrĆŸenĂĄ schĂ©mata vylepĆĄujĂ vĂœkonnost bezdrĂĄtovĂœch kooperativnĂch systĂ©mĆŻ, konkrĂ©tnÄ jejich propustnost.
DĂĄle jsme se zamÄĆili na zkoumĂĄnĂ NOMA technologie a navrhli optimĂĄlnĂ ĆeĆĄenĂ (protokoly) pro urychlenĂ datovĂ©ho pĆenosu a zajiĆĄtÄnĂ QoS v dalĆĄĂ generaci bezdrĂĄtovĂœch komunikacĂ. V tĂ©to prĂĄci jsme navrhli dvoucestnĂ© DF NOMA schĂ©ma (nazĂœvĂĄno jako TWNOMA protokol), ve kterĂ©m mezilehlĂœ pĆenosovĂœ uzel napomĂĄhĂĄ dvÄma zdrojovĂœm uzlĆŻm komunikovat mezi sebou. VĂœsledky simulace a analĂœzy ukazujĂ, ĆŸe navrĆŸenĂœ protokol TWNOMA vylepĆĄuje dosaĆŸenou pĆenosovou rychlost v porovnĂĄnĂ s konvenÄnĂm dvoucestnĂœm schĂ©matem pouĆŸĂvajĂcĂm DNC (TWDNC protokol), dvoucestnĂœm schĂ©matem bez pouĆŸitĂ DNC (TWNDNC protokol) a dvoucestnĂœm schĂ©matem v zesil-a-pĆedej (amplify-and-forward) pĆenosovĂœch systĂ©mech (TWANC protokol).
Nakonec jsme zvĂĄĆŸili vyuĆŸitĂ kombinace NOMA a zabezpeÄenĂ fyzickĂ© vrstvy (Physical Layer SecurityâPLS) v podpĆŻrnĂ© kooperativnĂ kognitivnĂ sĂti (Underlay Cooperative Cognitive NetworkâUCCN). Zde je zde zkoumĂĄn vĂœbÄr nejlepĆĄĂho pĆenosovĂ©ho uzlu, kterĂœ uĆŸĂvĂĄ NOMA a bere v Ășvahu PLS pro efektivnÄjĆĄĂ pĆenos a zabezpeÄenĂ novĂ© generace bezdrĂĄtovĂœch sĂtĂ.440 - Katedra telekomunikaÄnĂ technikyvyhovÄ
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
A novel equivalent definition of modified Bessel functions for performance analysis of multi-hop wireless communication systems
A statistical model is derived for the equivalent signal-to-noise ratio of the Source-to-Relay-to-Destination (S-R-D) link for Amplify-and-Forward (AF) relaying systems that are subject to block Rayleigh-fading. The probability density function and the cumulated density function of the S-R-D link SNR involve modified Bessel functions of the second kind. Using fractional-calculus mathematics, a novel approach is introduced to rewrite those Bessel functions (and the statistical model of the S-R-D link SNR) in series form using simple elementary functions. Moreover, a statistical characterization of the total receive-SNR at the destination, corresponding to the S-R-D and the S-D link SNR, is provided for a more general relaying scenario in which the destination receives signals from both the relay and the source and processes them using maximum ratio combining (MRC). Using the novel statistical model for the total receive SNR at the destination, accurate and simple analytical expressions for the outage probability, the bit error probability, and the ergodic capacity are obtained. The analytical results presented in this paper provide a theoretical framework to analyze the performance of the AF cooperative systems with an MRC receiver
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