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Nowadays, orthogonal frequency division multiplexing (OFDM) systems are widely used for many different purposes, such as wireless broadcasting systems as digital video broadcasting—second generation terrestrial (DVB-T2), mobile networks as fourth generation long term evolution, or even specifications as the already approved by the DVB project, DVB-next generation for handhelds. The two first standards use state-of-the-art technologies that have currently made them two of the most cutting edge communication systems. In this paper, we propose a new diversity technique applicable to OFDM systems that improves the overall system performance. This technique will be evaluated in the frame of the DVB-T2 standard and compared to one of its most innovative diversity technologies: the rotated constellations (RC). Applying the proposed technique a performance improvement up to about 1 dB can be obtained when compared to the same system using RC. However, as RC, the proposed technique introduces a complexity increase in the detecting process. [ABSTRACT FROM AUTHOR]

Nowadays, communication systems need to satisfy very demanding constraints in order to cope with users new necessities. One of the most promising techniques to improve the system capacity is multiple input multiple output (MIMO). However, the use of MIMO implies a huge complexity increase in the detection process. In this paper, a method to reduce the aforementioned complexity is presented. Although the proposed method is analyzed for digital video broadcasting next generation for handhelds, its implementation is useful for any MIMO system that requires the computation of log likelihood ratios (LLRs), used by the low density parity check codes. The presented technique consists of applying a simplification when calculating the Euclidean distances needed by the LLRs. The simplification avoids almost all the multiplications, very area demanding when translated into hardware, and presents a performance loss under 0.1 dB. [ABSTRACT FROM PUBLISHER]

The constellation rotation and cyclic Q-delay technique has been adopted in second generation terrestrial digital video broadcasting to provide signal space diversity, improving the system performance under severe multipath propagation environments. The main drawback of this technique is the hardware complexity introduced in the demapping process compared to non-rotated constellations. In this brief, we present a simplified demapper that reduces up to 78% the number of required operations with almost no performance degradation compared to the results of the ideal max-log demapper. [ABSTRACT FROM PUBLISHER]