Improvement of Multipath Channel Performance for Optical MIMO-OFDM in LED Modulation with Fully Generalized Spatial-Frequency

This paper suggests a scheme to generalize the idea of LED index modulation concept by using the spatial multiplexing principle to relay complex OFDM signals through various channels such as AWGN, Rayleigh and Rician by splitting these signals into their real-imaginary and positive-negative components. In order to combat ISI as well as to increase the channel capacity. The MIMO-OFDM efficiency analysis, taking into account the constraint of the forward current of the LED is extracted. The accuracy of the theoretical results is verified by comparing the Bit Error Ratio (BER) reduction and improvement to the (SNR) results under varying condition of the channel. Using MIMO-OFDM as next-generation techniques, along with QAM aims to provide development of new concepts that will lead to the growth of future optical communication. Simulation results validate data rates gained over optical communication using LED modulation scheme and the pure transmission diversity method.

A Bibliographic review of wideband DTV networks using transmission diversity techniques

Este artigo apresenta resultados do espalhamento de retardo, fornecendo em primeira mão uma revisão bibliográfica completa aplicada à Televisão Digital Terrestre utilizada em esquemas de transmissão distribuída. Um levantamento da situação atual do desenvolvimento da pesquisa é obtido a partir de uma possível tendência recomendada por uma campanha de medição realizada em uma rede de frequência única urbana com dois transmissores sincronizados. A discussão de possíveis questões relacionadas às condições de recepção é considerada e a constante necessidade de atender aos requisitos técnicos modernos, como eficiência espectral e flexibilidade do sistema, também é abordada. Resultados teóricos, de simulação computacional, experimentais e de ensaios de campo são apresentados neste artigo, confirmando as melhorias associadas às redes de diversidade de fontes.

MIMO Sonar DOA Estimation with Joint Matched-Filtering Based on Transmission Diversity Smoothing

There is a class of methods based on transmission diversity smoothing by multiple-input multiple-output(MIMO) sonar called MIMO-TDS which is considered as one of the most effective methods for estimation of direction-of-arrival(DOA) using MIMO sonar systems. MIMO-TDS produced by orthogonal signal transmission for active sonar can be immediately implemented with high resolution algorithms such as MVDR to estimate the direction of received signals. However, the orthogonal transmission mode of MIMO-TDS is doomed to a loss of transmission array gain indirectly leading to the problem that the echoes are not equipped with as high SNR as enough for an accurate target localization, especially in scenarios in which the targets are far away from array. In order to solving the "low SNR" problem, a solution using all transmitted signals simultaneously to design a joint matched-filter intended for received signal is proposed to improve the performance of MIMO-TDS, which is inspired by the match-filtering concept of "MIMO sonar virtual array method" simplified as MIMO-VA. And accordingly, the unit impulse response function of proposed joint matched-filter is the equivalent of linear sum of all orthogonal transmitted signals and the modified MIMO-TDS is named as "joint matched-filtering MIMO sonar transmission diversity smoothing DOA estimation method", which could be simplified as MIMO-TDS-MF. The characteristic of proposed method is analyzed theoretically and compared to MIMO-TDS and MIMO-VA in this paper:Compared with MIMO-TDS, the proposed method not only retains the advantage of transmission diversity smoothing but also improves the SNR by joint match-filtering; What's more, compared with MIMO-VA, MIMO-TDS-MF is equipped with substantially less computation than the former due to an employment of much fewer matched-filters and is in possession of a superior robustness to that of MIMO-VA. Numerical experiments demonstrate the efficiency of proposed MIMO-TDS-MF.

Multi-scale immune selection and the transmission-diversity feedback of Plasmodium falciparum malaria

Antigenic diversity is a key factor underlying the complex epidemiology of Plasmodium falciparum malaria. Within-host clonal antigenic variation limits host exposure to the parasite’s antigenic repertoire, while the high degree of diversity at the population-level requires multiple exposures for hosts to acquire anti-disease immunity. This diversity is predominantly generated through mitotic and meiotic recombination between individual genes and multi-gene repertoires and is therefore expected to respond dynamically to changes in transmission and immune selection. We hypothesised that this coupling creates a positive feedback mechanism whereby infection and disease transmission promotes the generation of diversity, which itself facilitates immune evasion and hence further infection and transmission. To investigate the link between diversity and malaria prevalence in more detail we developed an individual-based model in which antigenic diversity emerges as a dynamic property from the underlying transmission processes. We show that the balance between stochastic extinction and the generation of new antigenic variants is intrinsically linked to within-host and between-host immune selection, which in turn determines the level of diversity that can be maintained in a given population. We further show that the transmission-diversity feedback can lead to temporal lags in the response to natural or intervention-induced perturbations in transmission rates. These results will add to our understanding of the epidemiological dynamics of P. falciparum malaria in different transmission settings and will have important implications for monitoring and assessing the effectiveness of disease control efforts.