Efficient implementation of filter bank multicarrier systems using circular fast convolution

In this paper, filter bank-based multicarrier systems using a fast convolution approach are investigated. We show that exploiting offset quadrature amplitude modulation enables us to perform FFT/IFFT-based convolution without overlapped processing, and the circular distortion can be discarded as a part of orthogonal interference terms. This property has two advantages. First, it leads to spectral efficiency enhancement in the system by removing the prototype filter transients. Second, the complexity of the system is significantly reduced as the result of using efficient FFT algorithms for convolution. The new scheme is compared with the conventional waveforms in terms of out-of-band radiation, orthogonality, spectral efficiency, and complexity. The performance of the receiver and the equalization methods are investigated and compared with other waveforms through simulations. Moreover, based on the time variant nature of the filter response of the proposed scheme, a pilot-based channel estimation technique with controlled transmit power is developed and analyzed through lower-bound derivations. The proposed transceiver is shown to be a competitive solution for future wireless networks

Channel estimation and tracking algorithms for vehicle to vehicle communications

The vehicle-to-vehicle (V2V) communications channels are highly time-varying, making reliable communication difficult. This problem is particularly challenging because the standard of the V2V communications (IEEE 802.11p standard) is based on the WLAN IEEE 802.11a standard, which was designed for indoor, relatively stationary channels; so the IEEE 802.11p standard is not customized for outdo or, highly mobile non-stationary channels. In this thesis,We propose Channel estimation and tracking algorithms that are suitable for highly-time varying channels. The proposed algorithms utilize the finite alphabet property of the transmitted symbol, time domain truncation, decision-directed as well as pilot information. The proposed algorithm s improve the overall system performance in terms of bit error rates, enabling the system to achieve higher data rates and larger packet lengths at high relative velocities. Simulation results show that the proposed algorithms achieve improved performance for all the V2V channel models with different velocities, and for different modulation schemes and packet sizes as compared to the conventional least squares and other previously proposed channel estimation techniques for V2V channels

Study and implementation of an advanced transceiver for 5G

With the years passing by, the users of mobile networks present higher needs and demands when it comes to e ective download and upload data rates. The fth generation of mobile communications assumes the concretization of binary rates above 1 Gbps to be achieved by any ordinary user. To ful l this requirement, it was necessary to undertake a study and development of a system using the 4th Generation of Mobile Communications (4G) waveform to lessen the need for adding new modules and increasing the complexity of mobile network systems. The main goal is to develop an Orthogonal Frequency Division Multiplexing (OFDM) waveform simulator for 5th Generation of Mobile Communications (5G) using Quadrature Amplitude Modulation (QAM), simulate its performance to compare with the theoretical one and perform laboratorial tests. In this study the channel estimation is carried out and we evaluated the performance of Bit Error Rate (BER) and Error Vector Magnitude (EVM) as study metrics and parallels the usual transmission loss models for indoor and free-space communications. The study and experiments end in resulting mobile uncoded and convolutional hard decision OFDM communications up to 5.9 Gbps of e ective data rate and the results and measurements were obtained inside the laboratory environment, with a signal carrier of 3.5GHz and 2dB of both antennas gain and 26dB of ampli er gain at distances up to 4 meters between the two antennas. The best result obtained considering the highest data rate achieved was a 256-QAM uncoded OFDM communication at 5.9 Gbps on a 4 meters distance between antennas.A quinta geração de redes móveis prevê a concretização de ritmos binários acima de 1 Gbps ao acesso de qualquer utilizador comum. Para concretizar esse requisito, foi necessário levar a cargo um estudo e desenvolvimento de um sistema que utilize a forma de onda do 4a Geração de Comunicações Móveis (4G) para diminuir eventuais necessidades de adição de novos módulos e aumento da complexidade dos sistemas de redes móveis. O objetivo concreto é o desenvolvimento de um simulador de forma de onda de Multiplexação por Divisão de Frequência Ortogonal (OFDM) que atinja as taxas efetivas de dados para a 5a Geração de Comunicações Móveis (5G) utilizando Modulação de Amplitude em Quadratura (QAM), realizar simulações para averiguar o normal funcionamento de acordo com a teoria e realizar testes laboratoriais. Neste estudo é efetuada a estimação de canal, são avaliadas as performances da Taxa de Erro de Bits (BER) e da Magnitude do Vetor de Erro (EVM) como métricas de estudo e efetuado um paralelismo com os modelos de perdas de transmissão usuais para comunicações indoor e de espaço livre. O estudo e os testes laboratoriais concluem-se em comunicações OFDM não codi cado e com decisão abrupta em códigos convolucionais efetuadas até velocidades efetivas de 5.9 Gbps de dados e foram obtidos os resultados e medições num ambiente de laboratório, com uma portadora de 3.5 GHz, com o ganho de ambas as antenas de 2dB e um ampli cador com um ganho de 26dB em distâncias até aos 4 metros entre as duas antenas. O melhor resultado obtido em termos de velocidade de transmissão de dados foi a comunicação 256-QAM OFDM não codi cado atingindo os 5.9 Gbps com 4 metros de distância entre antenas