Papers by Antonio García Zambrana
IEEE Communications Letters, 2001
In this letter, the authors conclude that pulse-position modulation (PPM) with Gaussian pulses pr... more In this letter, the authors conclude that pulse-position modulation (PPM) with Gaussian pulses provides better performance than classic PPM schemes with rectangular pulses over unguided optical links operating at high bit rates. In this fashion, both intersymbol interference (ISI), induced by multipath propagation, and the phase distortion effects due to the high-pass filter whose function is to suppress interference, are minimized. However, relevant improvement is not achieved if compared with the OOK format with Gaussian pulses and low duty cycle. The above conclusion is validated by the corresponding bit-error rate (BER) computation using Monte Carlo simulations.
Journal of Gastrointestinal Surgery, 1998
We examine the performance of on-off keying (OOK) formats in indoor unguided optical links, in or... more We examine the performance of on-off keying (OOK) formats in indoor unguided optical links, in order to minimize both intersymbol interference (ISI), induced by multipath propagation, and phase distortion effects, due to interference suppression receiver filter. This study has been realized by means of a direct application of the correlation operator. We conclude that the OOK modulation with return-to-zero (RZ) pulses of variable duty cycle provides better performances than other signaling formats more frequently proposed in reported works, also considered in this study, together with the adoption of a low complexity receiver, lacking baseline restoration and equalizer filters. The above conclusion is validated by corresponding bit-error rate (BER) computation
ABSTRACT In this paper, a novel rate-adaptive transmission scheme using block codes with codeword... more ABSTRACT In this paper, a novel rate-adaptive transmission scheme using block codes with codewords of variable Hamming weight is presented. This coding scheme is based on a multiple-pulse position modulation (MPPM) technique, where codewords with different Hamming weight are allowed, including the all-zero one. The performance analysis of this new scheme has been presented by comparing with on-off keying (OOK) formats with memory and the HHH(1,13) code proposed and specified in the Very Fast Infrared (VFIr) standard by the Infrared Data Association (IrDA), but operating under a rate-adaptive transmission environment. The superiority of the block coding method has been corroborated, being the improvement in performance higher as the length of the data block is increased. Additionally, the use of very simple decoding schemes based on ML detection has been proposed as alternative to the procedure based on the Viterbi algorithm. Finally, an improved rate-adaptive capability is provided by the translation table adopted in the block coding here proposed, leading to an attractive adaptation procedure by swapping between proper translation tables
The simultaneous use of a simple rate-adaptive transmission scheme, based on on-off keying (OOK) ... more The simultaneous use of a simple rate-adaptive transmission scheme, based on on-off keying (OOK) formats with memory, and a new self-orienting receiver, alternative to conventional angle diversity techniques, is proposed in order to mitigate the effect of large variations of the signal-to-noise ratio in indoor wireless infrared communications. In relation to the rate-adaptive transmission technique, variable silence periods are used for modifying the statistics of the amplitude sequence regarding the statistics of the message sequence, allowing an increase of the peak-to-average optical power ratio (PAOPR). With regard to the new diversity technique proposed, this is based on giving a self-orienting capability to the receiver optical front-end, thus optimizing link quality parameters. It is applied to links operating at an initial bit rate of 200 Mb/s, providing a signaling rate with a wide dynamic range and a relevant improvement in performance with a gradual complexity in implementation, compared with the scheme proposed and specified in the advanced infrared (AIr) standard by the Infrared Data Association (IrDA), which is based on repetition coding and pulse-position modulation.
... Communications A. Jurado-Navas, A. Garcıa-Zambrana, A. Puerta-Notario Dpt. ... As a consequen... more ... Communications A. Jurado-Navas, A. Garcıa-Zambrana, A. Puerta-Notario Dpt. ... As a consequence of this phenomenon, the quality of the received signal can be deteriorated and will undergo fluctuations in both the intensity and the phase. ...
The simultaneous use of a simple rate-adaptive transmission scheme based on the use of variable s... more The simultaneous use of a simple rate-adaptive transmission scheme based on the use of variable silence periods and a new self-orienting receiver, as an alternative to conventional angle diversity techniques, is proposed in order to mitigate the effect of large variations of the signal-to-noise ratio (SNR) in indoor wireless infrared communications. In relation to the rate-adaptive transmission technique, variable silence periods are used so as to increase the peak-to-average optical power ratio (PAOPR). With regard to the new diversity technique proposed, this is based on giving a self-orienting capability to the optical front-end, optimizing link quality parameters. We apply it to links operating at high initial bit rates of 50, 100 and 200 Mb/s, providing a signaling rate with a wide dynamic range and a. relevant improvement in performance with a gradual complexity in implementation, compared with the scheme, proposed and specified in the advanced infrared (AIr) standard by the Infrared Data Association (IrDA), which is based on repetition coding and pulse-position modulation.
Optics Express, 2011
Atmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, w... more Atmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, which is known as atmospheric scintillation, severely degrading the performance over free-space optical (FSO) links. Additionally, since FSO systems are usually installed on high buildings, building sway causes vibrations in the transmitted beam, leading to an unsuitable alignment between transmitter and receiver and, hence, a greater deterioration in performance. In this paper, the outage probability as a performance measure for multiple-input/multiple-output (MIMO) FSO communication systems with intensity modulation and direct detection (IM/DD) over strong atmospheric turbulence channels with pointing errors is analyzed. Novel closed-form expressions for the outage probability as well as their corresponding asymptotic expressions are presented when the irradiance of the transmitted optical beam is susceptible to either strong turbulence conditions, following a negative exponential distribution, and pointing error effects, following a misalignment fading model where the effect of beam width, detector size and jitter variance is considered. Obtained results show that the diversity order is independent of the pointing error when the equivalent beam radius at the receiver is at least twice the value of the pointing error displacement standard deviation at the receiver. Simulation results are further demonstrated to confirm the analytical results. Additionally, since proper FSO transmission requires transmitters with accurate control of their beamwidth, asymptotic expressions here obtained for different diversity techniques are used to find the optimum beamwidth that minimizes the outage performance.
Electronics Letters, 2006
A novel rate-adaptive transmission scheme using block coding of variable Hamming weight is presen... more A novel rate-adaptive transmission scheme using block coding of variable Hamming weight is presented for use in indoor optical wireless communications systems. This coding scheme is based on multiple pulse-position modulation, where codewords with different Hamming weight are allowed. The improvement in performance is corroborated by bit error rate computation using Monte Carlo simulation.
Electronics Letters, 2008
ABSTRACT A new upper bound on the channel capacity of power- and bandwidth-constrained optical in... more ABSTRACT A new upper bound on the channel capacity of power- and bandwidth-constrained optical intensity channels corrupted by white gaussian noise is derived when equiprobable binary pulse amplitude modulation is used. a new closed-form upper bound on the capacity is found through a sphere-packing argument, presenting a tighter performance at lower optical signal-to-noise ratio when compared with previously reported bounds.
In this paper, convolutional encoding with Viterbi decoding is applied on on-off keying (OOK) for... more In this paper, convolutional encoding with Viterbi decoding is applied on on-off keying (OOK) formats with different pulse shapes having different duty cycles for use in wireless infrared links at high bit rates, so as to investigate the suitability of this forward error correction technique to the infrared medium when different pulse shapes are employed. Here, by means of a direct application of the input-output crosscorrelation operator and the corresponding bit-effor rate (BER) computation, the authors conclude that the OOK format with Gaussian pulses and low duty cycle provides quite good performance even when no channel coding is considered, obviating the need for increasing the receiver complexity
In this paper, pulse-position modulation (PPM) for indoor unguided optical links are compared in ... more In this paper, pulse-position modulation (PPM) for indoor unguided optical links are compared in terms of performances and required complexity. By means of a direct application of the correlation operator and the corresponding bit error rate (BER) computation, we conclude that Gaussian pulse-position modulation (GPPM) provides better performance than classic PPM schemes, so as to minimize both intersymbol interference (ISI), induced by multipath propagation, and phase distortion effects, due to the interference suppression receiver filter
... Antonio Garcia-Zambrana and Antonio Puerta-Notario ... As a first approach, for taking into a... more ... Antonio Garcia-Zambrana and Antonio Puerta-Notario ... As a first approach, for taking into account post detection high pass filtering, which will induce baseline wander, and upper band limit due to diffuse channel, different schemes could be examined from the point of view of ...
Electronics Letters, 2001
... TJ, and MACLEOD, MD: 'Comparison of quadratic B-spline interpolators', Electron. ..... more ... TJ, and MACLEOD, MD: 'Comparison of quadratic B-spline interpolators', Electron. ... 3 5 6 7 8 Coinprison: If thc spline coefficients ci depended linearly 011 San-ples of x(f), as in the methods (I), (2), (3), and (5) we could use results of 181 to calculate the error E* analytically. ...
Electronics Letters, 2010
The performance evaluation of different rate-adaptive transmission techniques for indoor unguided... more The performance evaluation of different rate-adaptive transmission techniques for indoor unguided optical links is presented. Here, the superiority of the adaptive environment based on the use of variable silence periods and on-off keying (OOK) formats with memory has been corroborated if compared to other rate-adaptive techniques also used in this kind of system. Classical convolutional and rate-compatible punctured convolutional (RCPC) coding have been considered. A new hybrid RCPC scheme, with a puncturing matrix based on the insertion of variable silence periods, is proposed, achieving better bit-error rate (BER) results than conventional RCPC codes. On the other hand, OOK formats with memory have also been analyzed from the point of view of run-length limited (RLL) codes, comparing their performance with the HHH(1,13) code proposed and specified in the very fast infrared (VFIr) standard by the Infrared Data Association (IrDA). Finally, OOK formats with memory have revealed a greater increase of the peak-to-average optical power ratio (PAOPR). PAOPR has shown to be a very efficient parameter for evaluating the suitability of different rate-adaptive transmission techniques to the peculiar characteristics of wireless infrared channels.
Eurasip Journal on Wireless Communications and Networking, 2010
A new upper bound on the capacity of power-and bandwidth-constrained optical wireless links over ... more A new upper bound on the capacity of power-and bandwidth-constrained optical wireless links over gamma-gamma atmospheric turbulence channels with intensity modulation and direct detection is derived when on-off keying (OOK) formats are used. In this free-space optical (FSO) scenario, unlike previous capacity bounds derived from the classic capacity of the well-known additive white Gaussian noise (AWGN) channel with uniform input distribution, a new closed-form upper bound on the capacity is found by bounding the mutual information subject to an average optical power constraint and not only to an average electrical power constraint, showing the fact that the input distribution that maximizes the mutual information varies with the turbulence strength and the signal-to-noise ratio (SNR). Additionally, it is shown that an increase of the peak-to-average optical power ratio (PAOPR) provides higher capacity values. Simulation results for the mutual information are further demonstrated to confirm the analytical results under several turbulence conditions.
A new and simple rate-adaptive transmission scheme for indoor unguided optical links is proposed.... more A new and simple rate-adaptive transmission scheme for indoor unguided optical links is proposed. This scheme is based on the use of variable silence periods, allowing the increase of the peak-average optical power ratio, which is a favorable characteristic in wireless infrared communications using intensity modulation with direct detection. Here, it is applied to links operating at high bit rate initially, providing a signaling rate with a wide dynamic range and requiring a very low-complexity implementation. The authors compare this scheme in terms of performance and complexity with the scheme proposed by the IrDA, which is based on repetition coding and pulse-position modulation
IEEE Communications Letters, 2005
In this letter, the performance evaluation of rateadaptive transmission schemes for indoor unguid... more In this letter, the performance evaluation of rateadaptive transmission schemes for indoor unguided optical links has been analyzed in the context of runlength-limited (RLL) sequences. Here, the superiority of on-off keying (OOK) formats with runlength constraints based on silence periods has been corroborated in terms of code efficiency and peak-to-average optical power ratio (PAOPR) compared to a hybrid HHH(1, 13) code, variable-rate signalling technique obtained by modifying the RLL(1, 13) code specified in the Very Fast Infrared (VFIr) standard by the Infrared Data Association (IrDA). Additionally, the use of very simple decoding schemes based on Boolean logic has been proposed.
IEEE Photonics Technology Letters, 2009
In this letter, transmit laser selection for multiple-input-single-output free-space optical comm... more In this letter, transmit laser selection for multiple-input-single-output free-space optical communication systems with intensity modulation and direct detection over strong atmospheric turbulence channels is analyzed. Assuming channel side information at the transmitter and receiver, a transmit diversity technique based on the selection of the optical path with a greater value of scintillation has shown to be able to extract full diversity as well as providing better performance compared to other alternatives recently proposed such as orthogonal space-time block codes and repetition codes. Simulation results are further demonstrated to confirm the analytical results obtained for a diversity order of two.
Optics Express, 2010
Atmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, w... more Atmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, which is known as atmospheric scintillation, severely degrading the link performance. In this paper, a scheme combining transmit laser selection (TLS) and space-time trellis code (STTC) for multiple-input-single-output (MISO) free-space optical (FSO) communication systems with intensity modulation and direct detection (IM/DD) over strong atmospheric turbulence channels is analyzed. Assuming channel state information at the transmitter and receiver, we propose the transmit diversity technique based on the selection of two out of the available L lasers corresponding to the optical paths with greater values of scintillation to transmit the baseline STTCs designed for two transmit antennas. Based on a pairwise error probability (PEP) analysis, results in terms of bit error rate are presented when the scintillation follows negative exponential and K distributions, which cover a wide range of strong atmospheric turbulence conditions. Obtained results show a diversity order of 2L − 1 when L transmit lasers are available and a simple two-state STTC with rate 1 bit/(s · Hz) is used. Simulation results are further demonstrated to confirm the analytical results.
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Papers by Antonio García Zambrana