João Carlos Silva

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The analytical bit error rate of hierarchical quadrature amplitude modulation formats, which include uniform and nonuniform constellations, over flat Rayleigh fading environments is studied in this paper. The analysis takes into account the effect of imperfect channel estimation and considers diversity reception with both independent identically and(More)
In the Long Term Evolution (LTE) of UMTS the Interactive Mobile TV scenario is expected to be a popular service. By using multi-resolution with hierarchical modulations this service is expected to be broadcasted to larger groups achieving significant reduction in power transmission or increasing the average throughput. In this paper system level simulations(More)
Accurate channel estimation is mandatory for the performance of OFDM modulations (Orthogonal Frequency Division Multiplexing). For this purpose, pilot symbols and/or training sequences are usually multiplexed with data symbols. To avoid the spectral degradation associated to multiplexed pilots, the use of implicit pilots (i.e., pilots superimposed to data)(More)
Among radio technologies, multiple-input multipleoutput (MIMO) systems have attracted wide research interests in recent years. It is widely recognized that MIMO systems can be employed for achieving a high capacity and a high diversity order, for mitigating the effects of various types of interfering signals, and for supporting space-division(More)