Wrong Slot Error Research Articles

Comparison between dicode PPM and offset PPM enhancement with different error correction codes

AbstractOffset pulse position modulation (OPPM) and Dicode pulse position modulation (DiPPM) have been introduced as new attractive modulation techniques, however, they are suffering from erasure, wrong slot, and false alarm errors. in this paper, two types of error correction (EC) codes, Low‐Density Parity Check (LDPC) code and Reed Solomon (RS) code, where paired the OPPM and DiPPM systems to reduce bugs, analyze the best EC parameters, and choose the superlative EC system. In other words, the performance of OPPM engaging LDPC codes and DiPPM employing LDPC codes will be compared against the OPPM engaging RS codes and DiPPM employing RS codes. To systematically carry out this comparison, numbers of photons, transmission efficiency, and the code rate are computed. The evaluation has stated that the data transmission rate at the start has indicated that OPPM with LDPC requires only 1.2 × 103 photons/pulse compared to the necessity of 1.821 × 103 photons/pulse when the DiPPM used LDPC. Accordingly, the transmission efficiency has been increased due to a reduction of number of photons. Also, the coded OPPM with LDPC codes is better than the coded DiPPM with LDPC codes when operating at a code rate that is approximately 0.7.

An anti-noise modem for visible light communication systems using the improved M-ary position phase shift keying

In this paper, we propose an anti-noise modem based on the improved M-ary position phase shift keying (MPPSK) for visible light communication (VLC) systems. The line spectral interferences in the original MPPSK are theoretically analyzed and approximately mitigated by adopting a set of improved waveform samples. Then, within one symbol duration, the peak envelopes of the received signals are captured at each of synchronization bit with a quantity of sampling offsets to improve the proportion of the reliable data tones. In addition, a novel demodulation scheme using an amplitude-position detector based on soft decision is proposed to recover the MPPSK symbols, which can minimize the contamination influence of channel noise on symbol decision. With this scheme, the false alarm error and wrong slot error caused by the multipath fading in VLC channel can be effectively corrected and the bit error rate (BER) performance of the system is significantly improved. Simulation results demonstrate that the proposed scheme reduce the required signal-to-noise ratio (SNR) at least by 2 dB for BER = 10−4, which show the feasibility and validity of this anti-noise modem.

Optimum mapping in an optical multiple pulse position modulation link using a maximum likelihood sequence detection scheme

The performance analysis of any multiple pulse position modulation (PPM) system is extremely time consuming because of the effects of different detection errors on the multiple PPM alphabet. In a small multiple PPM system such as ( 2 12 ), there are 64 codewords and each one can have ten possible false alarms, two possible erasures and four possible wrong-slot errors. The situation is worse if higher-order codes are considered. A novel algorithm, which reduces the time taken to predict the sensitivity of a multiple PPM system from almost 2 h of analysis to under a second, is presented. Results obtained using this method agree with those obtained using a full mathematical model. The authors also present a methodology that obtains a close to optimum mapping for any multiple PPM system. Detailed results show the effectiveness of this mapping routine.

Investigation of an optical multiple PPM link over a highly dispersive optical channel

A performance analysis of (X/Y) multiple pulse position modulation (PPM) systems, in which X denotes the number of data slots and Y the number of pulses, operating over a plastic optical fibre channel has been described. The effects of receiver noise and channel dispersion are accounted for and the manner in which the erasure, wrong-slot and false-alarm errors affect the system performance is examined. The receiver/decoder uses slope detection and a maximum likelihood sequence detector. As the analysis of any (x/y) multiple PPM system is extremely time-consuming, a novel automated solution was designed to predict the equivalent pulse code modulation (PCM) error rates of specific sequences and to simplify the task. A measure of coding quality that accounts for efficiency of coding and bandwidth expansion has also been proposed. Using this measure, original results show that a (12/6) system is the most efficient for a wide range of bandwidths.

Performance analysis of a dicode PPM system, operating over plastic optical fibre, using maximum likelihood sequence detection

Dicode pulse-position modulation (PPM) systems suffer from three types of pulse detection errors: wrong-slot, false-alarm and erasure. The author presents an original maximum likelihood sequence detector (MLSD) algorithm that uses the natural pulse sequences in dicode PPM to completely eliminate wrong-slot errors, and reduce the effects of false alarms and erasures. The error performance of a dicode PPM system using such a detector is analysed, and theoretical results are presented for a system transmitting 1 Gbit/s PCM data over a dispersive medium, such as graded-index plastic optical fibre, with a wide-bandwidth receiver and a classical matched filter. It is shown that little is gained if MLSD is used in a low-dispersion link. However, if the link bandwidth is equal to 0.46 times the PCM bit-rate, an MLSD dicode PPM system requires 4.0×104 photons per pulse, as opposed to 66×104 photons for a system without MLSD. This corresponds to a 12.2 dB increase in sensitivity. It is further shown that an MLSD dicode system can operate down to a bandwidth of 0.29 times the PCM bit-rate, making it an ideal candidate for high-dispersion links.

Performance of a suboptimum PPM presynchronization filtering network

AbstractAn optimum presynchronization filter for the pulse‐position‐modulation (PPM) signal is derived and shown to be comprised of a matched filter in cascade with a derivative network. An original investigation of the performance of the filtered PPM system is presented. The matched filter is realized from a time‐domain specification on the received pulse shape and an RC combination derivative network is used to shape the pulse. The results demonstrate that there exists an optimum value of the differentiating capacitor resulting in performance that is close to the true derivative. The results obtained illustrate a significant improvement in both the timing variance and jitter wrong slot error (JWSE) probability compared to that for the matched filter. © 1995 John Wiley & Sons, Inc.

Performance analysis of self-synchronized optically preamplified PPM

The performance of a hybrid erbium-doped fiber amplifier pulse position modulation (EDFA PPM) system is investigated under self-synchronization. Sensitivity results are presented for a system operating at 622 Mb/s and /spl lambda/=1.53 /spl mu/m. These indicate that EDFA PPM offers 7.9 dB sensitivity improvement over an equivalent EDFA PCM system and is beyond the fundamental PCM limit. An original expression is derived for the EDFA PPM power spectral density (PSD) under jitter. Original results are presented for the timing variance and the jitter wrong slot error (JWSE) probability due to the extracted self-timing. An original analysis and results are given for the system sensitivity penalty due to jitter. The penalty varied between 0.15 and 1.9 dB for the range of parameters considered. The selection of the system parameters that minimizes the penalty is investigated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Timing jitter and its impact on a self‐synchronised optical fibre PPM system

AbstractAn original spectral characterisation for the jitter in optical fibre pulse position modulation (PPM) is developed. The characterisation is used to examine the problem of slot synchronisation in PPM under two distinct cases. First when the PPM system is dominated by the self modulation noise namely the pattern‐dependent jitter. Then when both pattern and receiver‐generated jitter accumulate to impair the PPM system. We present a thorough performance analysis of the system under jitter impairment. Original results are obtained for the slot timing variance and the wrong slot error probability (WSE) in terms of the PPM number of slots, the phase lock loop (PLL) bandwidth and the normalised fibre bandwidth. The results indicate that with proper selection of the system parameters the slot jitter impairment can be minimised and maintained within prespecified levels. Frame synchronisation robustness is examined for a novel class of frame synchronisers previously proposed. Original results are presented for the extracted frame clock timing variance and the system WSE probability due to frame clock jitter when the system is dominated by its self noise. The frame synchronisers performance is shown to be optimisable through proper selection of the PLL bandwidth and the number of natural sequences tracked.

Performance and optimal presynchronisation filtering for direct-detection optical fibre PPM

A thorough performance analysis is presented for a self-synchronised direct-detection optical fibre pulse position modulation (PPM) system. A new hybrid erbium-doped fibre amplifier (EDFA) PPM system is analysed. Sensitivity results are presented for a system operating at 622 Mbit/s and lambda =1.53 µm. These results indicate that EDFA PPM offers 7.9 dB sensitivity improvement over a comparable PCM system and is beyond the PCM fundamental limit. An original expression is presented for the PPM power spectral density under jitter. Original results are given for the extracted-slot clock timing variance and the resultant jitter wrong-slot error probability. The sensitivity penalty associated with self synchronisation is investigated and shown to vary between 0.15 and 1.9 dB for the range of parameters considered. An original presynchronisation filtering strategy is proposed and results are presented demonstrating its effect. The sensitivity penalty was bound to about 0.1 dB when the proposed presynchronisation filter was utilised.

Self‐timed p‐i‐n‐hbt ppm receivers

AbstractAn original analysis and results are presented for the sensitivity and self‐timing of a hybrid p‐i‐n, heterojunction bipolar transistor pulse position modulation (p‐i‐n‐HBT PPM) strategy at 622 Mbit/s and λ = 0.85 μm. The results indicate a significant performance improvement over a comparable p‐i‐n‐HBT PCM system. The proposed strategy can find application in optical signal distribution at high bit rates in areas such as optical back planes and multiprocessor systems. The self‐timing of the hybrid is addressed and original results are presented for the extracted slot clock timing variance and the associated jitter wrong slot error (WSE) probability, resulting in specifications on the optimum PPM order, fiber bandwidth, and phase‐lock loop (PLL) bandwidth under self‐timing. © 1994 John Wiley &amp; Sons, Inc.

A model for timing jitter estimation in optical‐fiber PPM

AbstractAn original model for timing jitter estimation in optical‐fiber PPM is developed and used to examine the performance impairment due to imperfect slot synchronization. An original expression that predicts the spectral properties in the presence of jitter is presented. The extracted slot clock timing variance is evaluated in terms of the PPM parameters such as the number of slots and the modulation index, and the effects of the other parameters such as the phase‐locked loop (PLL) bandwidth and the fiber bandwidth are examined and used to optimize the slot clock timing variance. Original results are presented for the system wrong slot error (WSE) probability due to imperfect synchronization. The results indicate that this probability can be maintained well below the 10−9 system operating error rate. The model enables the identification of the set of optimum PPM, PLL, and fiber parameters for a given required performance. © 1994 John Wiley &amp; Sons, Inc.

A new edge detector for CMI optical fiber transmission with improved jitter tolerance

An edge detecting scheme for coded mark inversion (CMI) line codes which can reject wrong slot errors is proposed. This scheme looks at data transitions over one-and-a-half symbol durations and makes a binary decision based on the most likely transition pattern. An analysis and measurement results for the bit-error-rate performance of this scheme over an optical fiber link which show improvements in the detector tolerance against symbol timing jitters are presented. >

Performance analysis of coded optical ppm system using direct and coherent detection

Monomode optical fibres currently used in optical communication systems usually have bandwidths much greater than the information rate transmitted. This excess bandwidth can be used to improve receiver sensitivity. Pulse-position modulation (PPM) schemes are usually used in optical communication systems to improve receiver sensitivity. The paper analyses the sensitivity of the receiver of an optical PPM system, considering both wrong-slot error and false-alarm error. Coded optical PPM systems with direct and heterodyne detection are analysed. The performances of Reed-Solomon codes with different code rates are considered. Relations between bit-error probability Pb and the optimum efficiency p for the uncoded and coded systems are obtained. It is found that system performance does not necessarily improve with coding. System performance improves only for codes that are capable of reducing the minimum required number of photons sufficiently to compensate for the decrease in system efficiency resulting from coding.

Pulse-Position Modulation for Transmission Over Optical Fibers with Direct or Heterodyne Detection

The best monomode optical fiber links have bandwidths orders of magnitude greater than that of the information currently transmitted over them. This excess bandwidth can be exploited using digital PPM to improve receiver sensitivity. This paper analyzes the receiver sensitivity of an optical PPM system over a slightly dispersive channel, i.e., where both wrong slot and false alarm errors are important. It is shown that receiver sensitivity of better than 100 photons per binary bit-time is theoretically possible using direct detection and uncoded PPM. Ideal heterodyne detection should reduce this to below 5 photons per binary bit-time. Timing extraction and a digital modulation method are discussed.