Channel Fading in Mobile Broadband Systems: Challenges and Opportunities

High-speed data signals transmitted over mobile broadband channels are seriously distorted by both time-varying effect and frequency-selective fading (FSF). These distortions introduce challenges since channel variances in both time-domain and frequency-domain form a two-dimensional channel matrix which is hard to estimate, but meanwhile provide opportunities for information security since all signals are directly encrypted by the channels which are adequately random over time, frequency and space. These challenges and opportunities are studied in this thesis as two parts. In the first part, we propose a novel time-varying channel estimation (TVCE) algorithm named piece-wise time-invariant approximation (PITIA) to estimate a typical type of mobile broadband channels - the high-speed train (HST) channels. PITIA customizes general time-varying channel models according to HST channels' specific features, and outperforms conventional TVCE algorithms by about 3-dB in terms of estimation error. In the second part, we propose the first physical-layer challenge-response authentication mechanism (PHY-CRAM) which uses the mobile broadband channels to prevent eavesdropping during authentication. Since pilots and reference signals are eliminated, eavesdroppers cannot demodulate credential information, while legitimate receivers use the channels' reciprocal property to cancel FSF. PITIA is evaluated by computer based simulations, and the effectiveness of PHY-CRAM is validated by prototyping and real-world experiments. Both pieces of works are built upon a unified system model and orthogonal frequency-division multiplexing (OFDM) modulation.Ph.D.College of Engineering and Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/106584/1/Dissertation_Dan_Shan.pd

Estudo do comportamento de canal em redes 5G: uma análise preditiva

A paramether that begins to be particularly important on the dimensionament of the 5G networks is the communication channel state, mainly considering the new frequencies used, the growing number of connected devices and the necessity of allocate resources efficiently. To dimension the channel effects, the Base Station (BS) receives from the User Equipment (UE) a measurement of the channel quality, called Channel Quality Information/Indicator (CQI), from wich makes the scheduling of the resources to better attend the users. The study developed here wants to generate a reliable data base of a CQI flow along a transmission into a mobile network Long Term Evolution Advanced (LTEA) with some parameters of the Release 15 of the Technical Specification (TS) from 3rd Generation Partnership Project (3GPP) of 5G using Matlab. After this, it is purposed the aplication of a temporal neural network to predict the CQI along a transmission. Lastly, evaluates the reability of the network, comparing the predicted values by the system and the real ones.Trabalho de Conclusão de Curso (Graduação)Um parâmetro que passa a ser particularmente importante no dimensionamento das redes 5G é o estado do canal de comunicação, principalmente ao considerar as novas frequências usadas, o número crescente de dispositivos conectados e a necessidade de alocar recursos de forma eficiente. Para dimensionar os efeitos do canal, a Base Station (BS) recebe do User Equipment (UE) uma medição da qualidade do canal, chamada Channel Quality Information/Indicator (CQI), a partir da qual faz o escalonamento dos recursos para melhor atender os usuários. O estudo aqui desenvolvido visa gerar uma base de dados confiável de um fluxo de CQI ao longo de uma transmissão em uma rede móvel Long Term Evolution Advanced (LTE-A) com alguns parâmetros da Release 15 das Technical Specification (TS) do 3rd Generation Partnership Project (3GPP) para o 5G usando o Matlab. Após isso, propõe-se a aplicação de uma rede neural temporal para prever o CQI ao longo de uma transmissão. Por fim, avalia-se a confiabilidade da rede, comparando os valores preditos pelo sistema e os reais