Quasi-orthogonal space-frequency coding in non-coherent cooperative broadband networks

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.So far, complex valued orthogonal codes have been used differentially in cooperative broadband networks. These codes however achieve less than unitary code rate when utilized in cooperative networks with more than two relays. Therefore, the main challenge is how to construct unitary rate codes for non-coherent cooperative broadband networks with more than two relays while exploiting the achievable spatial and frequency diversity. In this paper, we extend full rate quasi-orthogonal codes to differential cooperative broadband networks where channel information is unavailable. From this, we propose a generalized differential distributed quasi-orthogonal space-frequency coding (DQSFC) protocol for cooperative broadband networks. Our proposed scheme is able to achieve full rate, and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of our scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, we derive sufficient conditions for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity.Peer reviewe

Pseudo-random sequencies in UWB systems

Tato práce pojednává o technologii UWB a současném stavu problematiky a trhu. Jsou zmíněny mezníky v historii této technologie, stejně tak jsou popsány principy komunikace a použitelné modulační metody. Dále se práce zabývá metodami mnohonásobného přístupu k médiu a souvislostmi mezi vhodným návrhem pseudonáhodné posloupnosti a obsazením frekvenčního pásma. Simulace obsahuje model kanálu UWB, kde jsou vytvořeny profily pro různé úrovně rušení. Je zde řešena pouze fyzická vrstva komunikace pro modulaci BPSK a metodu mnohonásobného přístupu uživatelů direct sequence. Výsledky simulací jsou na konci práce popsány pomocí chybovosti spoje a diskutovány v závěru.This master´s thesis deals with Ultra-wideband and reveals present stage of this technology and situation on marketplace. In this work I will mention the milestones of its history and describe main fundamentals of communication and modulation methods in UWB systems. This work provides an overview of methods in pseudo-noise code design. The practical part includes UWB system simulation based on BPSK modulation and Directsequence multi-access scenario. This work presents BPSK modulated signal behavior in UWB channel model, where AWGN noise and multi-path energy is taken into account. Only physical layer was tested. At the end of this thesis, the summary and conclusion simulation results will be discussed. Bit error rate characteristic is a product of this testing.