[pt] Este trabalho descreve o projeto de um Sistema Remoto de Entrada e Saída de Dados (Remote Job Entry-RJE). O sistema desenvolvido emula a estação IBM/2780 do RJE. A emulação é obtida por software de microcomputador (MCPUC-80, INTEL 8080). A abordagem teórica inclui, em detalhes, Sistemas de Comunicação de Dados e Protocolos de Comunicação, e em particular, o protocolo BSC (Binary Synchronours Communication) que foi implementado neste projeto. A implementação é descrita em termos de requisitos, adaptações e métodos empregados no processo de emulação do IBM/2780 por sistema de microcomputador. / [en] This paper discribes de development of a Remote Job Entry System. The system developed is an emulation version of do IBM/2780, RJE station. the emulation process is by microcomputer software and hardware (MCPUC-80, INTEL 8080). The paper includes theoretical aspects of Data Communications Systems and Protocols, specialy of the Bunary Synchronous Communications protocol, which was used in this work. The implementation also describes the requirements, methods and adaptations that were necessary in the emulation process.

[pt] Com o advento dos microprocessadores e a crescente diminuição do preço dos circuitos integrados LSI (Large Scale Integration) houve um aumento da utilização de computadores de pequeno porte para a realização de tarefas locais e especificas. Tornou-se, então, economicamente viável a utilização, em número cada vez maior, de redes interligando computadores de pequeno porte. O presente trabalho contém um estudo dos diversos problemas decorrentes do projeto de redes natureza, apresentando soluções adequadas a cada caso. / [en] Theappearance of microprocessors and the lowering costs LSI (Large Scale Integration) technology brought and increaase in the use of low-size computers for dedicated applications. So, it became economically feasible to interconnect such low-size computers, creating a network. A study of various problems arising from the design of such networks is presented, as well as adequated solutions for each case.

Cooperative relay communication is a promising means of wireless communication in which cooperation is used to create a virtual transmit array between the source and the destination, thereby providing spatial diversity for combating the fading channel. In this thesis we develop cooperative communication protocols namely the orthogonal amplify-and-forward (OAF), non-orthogonal and orthogonal selection decode-and-forward (NSDF and OSDF) protocols. The diversity-multiplexing gain tradeoff (DMT) of the three protocols is determined and DMT-optimal distributed space-time code constructions are provided. The code construction is based on Cyclic Division Algebras. The codes constructed are sphere decodable and in some instances incur minimum possible delay. Included in our results is the perhaps surprising finding that the OAF and NAF protocols have identical DMT when the time durations of the broadcast and cooperative phases are optimally chosen to suit the respective protocol. Two variants of the NSDF protocol are considered: fixed-NSDF and variable-NSDF protocol. In the variable-NSDF protocol, the fraction of time occupied by the broadcast phase is allowed to vary with multiplexing gain. In the two-relay case, the variable-NSDF protocol is shown to improve on the DMT of the best previously-known static protocol for higher values of multiplexing gain. Our results also establish that the fixed-NSDF protocol has a better DMT than the NAF protocol for any number of relays.