Millimeter wave technologies present an appealing solution for increasing data throughputs as they provide abundant contiguous channel bandwidths as compared to conventional microwave networks. However, millimeter wave technologies suffer from severe propagation limitations and channel impairments such as atmospheric attenuation and absorption, path and penetration losses, and blockage sensitivity. Therefore, phased arrays and beamforming technologies are necessary to compensate for the degraded signal levels due to the aforementioned factors. Namely, base stations and mobile stations utilize directional transmission in the control- and data- plane for an enhanced channel capacity, which results in initial access challenges due to the absence of omni-directional transmission. Here the base station and mobile station are compelled to exhaustively search the entire spatial domain, i.e., in order to determine the best beamforming and combining vectors that yield the highest received signal level. Overall, a wide range of studies have looked at the initial beam access challenges in millimeter wave networks, with most efforts focusing on iterative and exhaustive search procedures, as well as subarrays schemes and out-of-band beam access. However, these studies suffer from significant signaling overhead attributed to the prolonged beam scanning cycle. In particular, access times here are excessively high that exceed control plane latencies and coherence times. Furthermore, existing work suffer from high computational complexity, power consumption, energy inefficiency, as well as low directivities and high outage probabilities. In light of the above, the contributions in this dissertation propose fast initial beam access schemes based upon novel meta-heuristic search schemes and beamforming architectures. These contributions include modified search procedures inspired by Nelder Mead, Luss-Jaakola, divide-and-conquer with Tabu search, generalized pattern search, and Hooke Jeeves methods. Furthermore, efficient and highly-directive access schemes are also developed in this dissertation levering sidelobe emissions, grating lobes and Hamming codes. The overall performance of the proposed solutions here is extensively evaluated versus traditional access schemes and incorporating different channel and path loss models. Finally, this dissertation addresses the problem of link sensitivity and blockage effects in millimeter wave networks, a subsequent stage to beam access and link association. Nevertheless, a novel link recovery procedure is proposed here that features instantaneous link-recovery and high signal levels.

Submitted by Patrícia Cerveira (pcerveira1@gmail.com) on 2017-06-06T18:58:56Z No. of bitstreams: 1 Felipe Frasson- Dissertação.pdf: 984658 bytes, checksum: 05ae4f112679292aefe890dc2f563010 (MD5) / Rejected by Biblioteca da Escola de Engenharia (bee@ndc.uff.br), reason: Patrícia, o formulário de submissão apresenta vários erros, informações duplicadas e fora da formatação (orientador, coorientador, resumo, dentre outros). Atenciosamente, Catarina Ribeiro Bibliotecária BEE - Ramal 5992 on 2017-06-29T16:53:14Z (GMT) / Submitted by Patrícia Cerveira (pcerveira1@gmail.com) on 2017-06-29T19:32:38Z No. of bitstreams: 1 Felipe Frasson- Dissertação.pdf: 984658 bytes, checksum: 05ae4f112679292aefe890dc2f563010 (MD5) / Approved for entry into archive by Biblioteca da Escola de Engenharia (bee@ndc.uff.br) on 2017-07-03T13:00:12Z (GMT) No. of bitstreams: 1 Felipe Frasson- Dissertação.pdf: 984658 bytes, checksum: 05ae4f112679292aefe890dc2f563010 (MD5) / Made available in DSpace on 2017-07-03T13:00:12Z (GMT). No. of bitstreams: 1 Felipe Frasson- Dissertação.pdf: 984658 bytes, checksum: 05ae4f112679292aefe890dc2f563010 (MD5) / Em um sistema de comunica c~oes, os sinais s~ao transmitidos atrav es de canais de comunica c~ao que, idealmente, deveriam transportar os dados de maneira a n~ao causar distor c~ao alguma. Por em, em sistemas reais, existem limita c~oes que interferem neste processo causando degrada c~ao nas informa c~oes transmitidas, podendo comprometer sua recep c~ao. Tais limita c~oes ocorrem devido a presen ca de ru do aditivo, e principalmente por interfer^encia intersimb olica, esta caracterizada pela sobreposi c~ao de s mbolos gerados por uma mesma fonte transmissora. A equaliza c~ao de canal e uma das t ecnicas existentes que reduzem os efeitos da interfer^encia intersimb olica, dando maior con abilidade e robustez aos sistemas de comunica c~oes. Dentre as t ecnicas utilizadas para equaliza c~ao de canal, o uso de algoritmo adaptativos vem sendo amplamente utilizados devido as suas propriedades de se auto-ajustarem as varia c~oes que ocorrem ao longo do tempo. Este trabalho tem como objetivo veri car o comportamento de diferentes tipos de algoritmos adaptativos cegos ou semicegos, assim denominados por n~ao utilizarem sequ^encias de treinamento, aplicados a equaliza c~ao de canais esparsos. Canais esparsos s~ao encontrados em diversos sistemas de comunica c~oes como, por exemplo, na comunica c~ao sem o (telefonia m ovel, transmiss~ao de r adio e TV), ou, ainda, em canais subaqu aticos. Os algoritmos foram escolhidos com base em recentes estudos desta aplica c~ao, que operam em modo cego ou semicego e utilizam estat sticas de alta ordem, como os algoritmos Bussgang e Matching Pursuit. Os algoritmos foram implementados em ambiente de simula c~ao computacional no qual foram utilizados canais esparsos simples e de resposta ao impulso conhecida, permitindo comparar o comportamento dos diferentes algoritmos, em termos do sinal recuperado, e da inversa da resposta ao impulso do canal original. / In communications systems, information signals are transmitted through communications channels that, ideally, are delivered without distortions. However, on real communications channels there are limitations that interferes on the process, reducing the probability to recover the original signal at receiver. These distortions are basically thermal noise and Intersymbol Interference (ISI), caused by superposition on the received symbols received from the same source. Channel Equalization acts reducing these distortions, bringing more reliability to communications systems. The objective of this work is to verify di erent adaptive algorithms behavior, applied to sparse channel equalization problem. Many communications systems have sparse channels, like broadcast radio, television, mobile telephony and underwater communications. The selected algorithms used in this work includes high order statistics algorithms family, like Bussgang and Matching Pursuit. This kind of algorithms are widely used, with high relevance, for blind channel equalization. The selected algorithms were submitted to computer simulations using simple sparse channels and knowledge about their impulse response, in order to analyze their behavior in therms of bit error rate and the inverse impulse response of the channel.