Ana Cinta Oria

Simplified Rotated Constellation Demapper for Second Generation Terrestrial Digital Video Broadcasting

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.

Cubic Metric Reduction for DCO-OFDM Visible Light Communication Systems

Visible light communication (VLC) systems with a direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) architecture suffers from the well-known problem of high peak-to-average power ratio (PAPR). A DCOOFDM signal at the input of the light emitting diode (LED) with high PAPR can experience clipping due to its limited dynamic-range. This causes distortion and degradation of the signal quality, forcing a large power back-off, and so leading to an inefficient use of the LEDs. In order to resolve this problem, we propose to apply a power derating reduction technique at the VLC transmitter based on a modification of the active constellation extension (ACE) method with two important changes: a better predictor of the power derating than the PAPR, the cubic metric (CM), and a more effective clipping stage. With the proposed method, we achieve a significant CM reduction as large as 7.1 dB, which contributes to a noticeable gain in the input power back-off of 2.5 dB or an important reduction of signal distortion, and a greater illumination to communication efficiency (ICE), higher than 30%.

Simplified Detection for DVB-NGH MIMO Decoders

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.

Modeling Airfield Ground Lighting Systems for Narrowband Power-Line Communications

Airfield ground lighting (AGL) systems are responsible for providing visual reference to aircrafts in the airport neighborhood. In an AGL system, a large number of lamps are organized in serial circuits and connected to current regulators that supply energy to the lamps. Controlling and monitoring lamps (including detection and location of burnt-out lamps) are critical for cost-saving maintenance and operation of AGL systems. Power-line Communications (PLC) is an attractive technology to connect elements of the AGL, reusing the power distribution cable as a transmission medium. PLC technologies avoid the installation of new wires throughout the airport infrastructure. This paper proposes a new model for power-line communication links in AGL systems. Every element (isolation transformer, primary circuit cable, and lamps) has been analyzed in laboratory and modeled using SPICE. The resulting models have been integrated to build a complete power-line link model. Simulation results are compared to experimental results obtained in real conditions in the Airport of Seville (Spain).

Reduced complexity ICI cancellation scheme for OFDM DVB-SH receivers

Mitigating the negative effects of Doppler spread is crucial in the future Digital Video Broadcasting Satellite to Handheld (DVB-SH) terminals. The implementation of conventional methods, such us the Decision Feedback Equalization (DFE), to estimate the intercarrier interference is not suitable for low cost DVB-SH terminals. To solve this problem, we propose a new technique, and its hardware architecture, that extremely reduces the consumption of hardware resources. We demonstrate that a reduced implementation of the proposed method, that requires only six multiplications and five additions, performs similar to the DFE method that needs high complexity cells.

Diversity Technique for OFDM Systems: Enhanced Time-Frequency Multiplexing (eTFM)

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.

Low Complexity Intercarrier Interference Cancellation for DVB-SH Receivers

In this paper, the authors survey the system degradation due to mobility and propose a new technique to combat the effects of Doppler spread in Digital Video Broadcasting Satellite to Handheld (DVB-SH) receivers. This paper proposes a very low complexity Intercarrier Interference (ICI) cancellation scheme that performs as other existing methods, while reducing significantly the hardware resources consumption. The proposed method is based on implementing a reduced version of the leakage matrix, that models the ICI in a mobile channel. Simulation results show a gain in the carrier to noise ratio C/N up to 9 dB for a bit error rate BER = 10−5 when compared to a DVB-SH receiver with no ICI compensation. In terms of receiver speed, simulations show an improvement up to 50 % in the best case.

L1 signaling mobility performance in the DVB-T2 receivers intercarrier interference cancellation method applied to L1 signaling

Abstract In this paper, DVB-T2 mobility performance for both payload and signaling is analyzed and a method to improve the L1 signaling behavior in a mobile scenario is presented by means of applying an intercarrier interference (ICI) cancellation algorithm. This method allows the signaling to support a higher Doppler spread and widening the set of configurations that can be supported.

Improved power efficiency for DVB-SH transmitters

Power efficiency is an important criterion for modern communications systems. It is well known that due to its high Peak-to-Average Power Ratio (PAPR) the Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme presents serious power efficiency problems related to the High Power Amplifier (HPA) of the transmitter that are critical in satellite systems like Digital Video Broadcasting Satellite to Handheld (DVB-SH). In order to improve the power efficiency we propose to apply to DVB-SH the Active Constellation Extension (ACE) algorithm as a PAPR reduction method. Additionally we also present a new ACE optimization criterion: the reduction of the cubic metric (CM). The minimization of both metrics provides an important improvement of the out of band distortion and the Output Back Off (OBO) of the amplifiers, and consequently an increase of the HPA power efficiency.