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This study proposes a new low-complexity decoding algorithm for low-density parity check codes, which is a variation of the offset min-sum algorithm and achieves a similar performance with lower hardware cost. A finite precision study is presented and the hardware cost of the implementation of three very large scale integration architectures is evaluated. As a conclusion, the proposed algorithm achieves similar performance with an area saving of around 18, 10 and 14% for the memory-based partially parallel, fully parallel and sliced message passing implementations, respectively., This research was supported by Fondo Europeo de Desarrollo Regional (FEDER), the Spanish Ministerio de Ciencia e Innovacion, under grant numbers TEC2008-06787 and TEC2011-27916.

[EN] A new transmission scheme for OFDM systems that uses the odd discrete Fourier transform to provide frequency diversity gain is proposed. Odd DFT allows the transmission of data subcarriers in frequencies that are centred between those employed by the traditional DFT. This fact is exploited to transmit data subcarriers on the group of frequencies that gives better performance using either traditional DFT or odd DFT. As an example, by using this approach a diversity gain up to 5.3 dB at a BER of 10-4 in a typical indoor channel model can be achieved. © 2011 The Institute of Electronics, Information and Communication Engineers., This work was supported by the Spanish Ministerio de Ciencia e Innovacion under grant TEC2008-06787.

This paper presents two algorithms to extend the MIMO-decoding capability of successive projection algorithm (SPA). The algorithms, called Flag-SPA and Relaxed-SPA, are based on different methods to avoid repeating the selected path in each iteration of the algorithm, the first by using a flag matrix, the second by assigning a high weight to a selected path. Equivalences with K-best algorithm in terms of average BER for a SNR range from 25 to 30 dB have been found and it is shown that for low SNR the proposed SPA-based algorithms exhibit lower computational load than their equivalent K-best algorithm.

In this paper a time synchronization algorithm for IEEE 802.11a/g OFDM-WLAN standard is presented and some modifications are proposed to simplify its implementation without sacrifice its performance. To evaluate its feasibility this algorithm is compared with others found in the literature. The comparison of performance has been carried out by simulation in multipath channels, at low signal to noise ratios and with carrier frequency offset. It is shown that the proposed solution has a better performance and a lower computational cost.

This paper presents a software tool to design intermediate frequency and baseband digital transceivers on FPGA. Main characteristic of this tool is that an ad-hoc interpolation or decimation filter chain composed by CIC, polyphase, pulse shaping, matched filters and a CORDIC-based or ROM-based mixer can be selected. The tool allows the software radio designer to develop downconverters and upconverters and, finally, automatically to generate the VHDL code to implement the system on Xilinx FPGAs.