Ghafour Amouzad Mahdiraji | University of Malaya, Malaysia (original) (raw)

Papers by Ghafour Amouzad Mahdiraji

In this paper, fuzzy logic is applied for identifying and applications especially in PQ diagnosis... more In this paper, fuzzy logic is applied for identifying and applications especially in PQ diagnosis such as harmonic classifying the short duration voltage variations of 8, 32 and 128 source detection [7], classification of transient disturbances [8] cycles waveforms. A program is written in Matlab to determine and the investigation on computer-based load sensitivity to the parameters such as duration, maximum and minimum root voltage sag [14]. mean square voltages of a disturbance by using the fast Fourier transform analysis. Based on these parameters, a fuzzy inference Fuzzy og (Lhas rapidlomeo of themost system has been developed with five fuzzy inputs, three fuzzy successful of today's technologies for developing outputs and 139 fuzzy rules. The inputs are the maximum and sophisticated control systems [9]. It is a powerful variation of minimum voltage magnitudes in per unit and disturbance crisp logic based on the experience and knowledge of human duration in seconds. On the other hand, the outputs are namely operation. In more specific terms, what is central about fuzzy outputl, output2 and output3 in which outputl is for classifying logic is that, unlike classical logical systems, it aims at instantaneous sag, non sag and momentary sag, output2 is for modeling the imprecise modes of reasoning that play an classifying instantaneous swell, non swell and momentary swell essential role in the remarkable human ability to make rational and output3 for classifying instantaneous interruption, non decisions in an environment of uncertainty and imprecision.

Research and Development, 2006. SCOReD 2006. 4th Student Conference on, 2006

In this paper, fuzzy logic is applied for identifying and classifying the short duration voltage ... more In this paper, fuzzy logic is applied for identifying and classifying the short duration voltage variations of 8, 32 and 128 cycles waveforms. A program is written in Matlab to determine the parameters such as duration, maximum and minimum root mean square voltages of a disturbance by using the fast Fourier transform analysis. Based on these parameters, a fuzzy inference system has been developed with five fuzzy inputs, three fuzzy outputs and 139 fuzzy rules. The inputs are the maximum and minimum voltage magnitudes in per unit and disturbance duration in seconds. On the other hand, the outputs are namely outputl, output2 and output3 in which outputl is for classifying instantaneous sag, non sag and momentary sag, output2 is for classifying instantaneous swell, non swell and momentary swell and output3 for classifying instantaneous interruption, non interruption and momentary interruption. The proposed fuzzy expert system has been tested with 1015 recorded voltage disturbances consisting of sags, swells, interruptions, transients, voltage notching and multiple disturbance waveforms. The results have proved that the developed fuzzy system has accurately identified and classified 98.42% of the tested voltage disturbances.

Research and Development, 2006. SCOReD 2006. 4th Student Conference on, 2006

In this article, three digital modulation schemes popular in optical wireless communication syst... more In this article, three digital modulation schemes
popular in optical wireless communication systems (OOK,
PPM and DPIM) are compared based on bandwidth
requirement, power efficiency, transmits-ion capacity and biterror
probability. In OOK, the bandwidth requirement is
roughly equivalent to the data rate (Rb). PPM achieves higher
average power efficiency than OOK at the expense of an
increased bandwidth ( 4) compared to OOK. Besides, the use
of PPM imposes more system complexity compared to OOK
since both slot- and symbol-level synchronizati-ons, critical to
system performance, are required at the receiver. Unlike PPM,
DPIM does not require symbol synchronization since each
symbol is initiated with a pulse. Furthermore, DPIM displays a
higher transmiss-ion capacity by eliminating all the unused
time slots from within each symbol. In terms of BER, 4-DPIM
displays a performance in between that of OOK and PPM. It is
concluded that DPIM is the most efficient scheme in terms of
transmission capacity and band-width requirements. When it
comes to power and error performance, PPM is the best
among the three schemes.

Wireless and Optical Communications Networks, 2007. WOCN'07. IFIP International Conference on, 2007

A new multiplexing and demultiplexing technique based on duty cycle division is proposed, thus t... more A new multiplexing and demultiplexing technique
based on duty cycle division is proposed, thus the name
Duty Cycle Division Multiplexing (DCDM). DCDM can be
applied in both electrical and optical domains. The new
technique allows for more efficient use of time slots as well
as the spectrum, taking advantage of both the conventional
TDM and FDM. In this paper, three channels operating at
the same speed of 10Gbps are multiplexed in the optical
domain and demultiplexed in the electrical domain. The
performance comparison is made against 30Gbps TDM,
and the experimental simulation results show that the
minimum sensitivity achieved is -26dBm and -25.5dBm for
the two systems respectively, thus a 0.5 dB improvement.

Telecommunications and Malaysia International Conference on Communications, 2007. ICT-MICC 2007. IEEE International Conference on, 2007

A new multiplexing technique which is called duty cycle division multiplexing (DCDM) is presente... more A new multiplexing technique which is called duty
cycle division multiplexing (DCDM) is presented in this paper.
Theoretical and simulation studies have been carried out to
evaluate the performance of this technique based on the signal
energy and symbol error rate (SER). A wireless channel based on
free space propagation model is considered for the simulation
study. Two modulation schemes of PSK and QAM are used to
evaluate the technique, against the data rates. Also, the
performance of the multiplexing technique is compared with the
conventional Time Division Multiplexing (TDM) technique as
well as with the multilevel M-ary signaling. The study shows that
the energy per bit in the DCDM technique, unlike that of the
TDM technique increases with the number of users. The
simulation results correspond with the theoretical study in which
the DCDM technique has better SER than that of TDM.

Wireless and Optical Communications Networks, 2007. WOCN'07. IFIP International Conference on, 2007

-A new multiplexing technique which is called Duty Cycle Division Multiplexing (DCDM) is present... more -A new multiplexing technique which is called Duty
Cycle Division Multiplexing (DCDM) is presented in this paper.
Theoretical and simulation studies have been carried out to
evaluate the performance of this technique based on the signal
energy and symbol error rate (SER). A wireless channel based on
free space propagation model is considered for the simulation
study. Two modulation schemes of PSK and QAM are used to
evaluate the technique, against the number of users and data
rates. Also, the performance of the multiplexing technique is
compared with the conventional Time Division Multiplexing
(TDM) technique as well as with the multilevel M-ary signaling.
The study shows that the energy per bit in the DCDM technique,
unlike that of the TDM technique increases with the number of
users. The simulation results correspond with the theoretical
study in which the DCDM technique has better SER than that of
TDM.

Wireless and Optical Communications Networks, 2008. WOCN'08. 5th IFIP International Conference on, 2008

A new multiplexing technique based on duty cycle division is proposed, under the name: Absolute P... more A new multiplexing technique based on duty cycle division is proposed, under the name: Absolute Polar Duty Cycle Division Multiplexing (APDCDM). The new technique allows for more efficient use of time slots as well as the spectrum, taking the advantage of both the conventional TDM and FDM. The basic properties based on theoretical analysis as well as simulation studies have been done to evaluate the performance of this technique based on the signal energy and symbol error rate (SER). In this paper the performance of Absolute Polar Duty Cycle Division Multiplexing is compared with multilevel M-ary as well as with the time division multiplexing (TDM) techniques. The simulation has been set for wireless transmission based on free space propagation model with adaptive white Gaussian noise (AWGN). PSK and QAM are used as modulation schemes to evaluate these techniques against data rates and number of users. The study shows that by increasing the number of users, the energy per bit in APDCDM has better performance than that of TDM technique. The simulation result correspond with the theoretical study shows that Absolute Polar Duty Cycle Division Multiplexing (APDCDM), has better SER than TDM.

Telecommunication Technologies 2008 and 2008 2nd Malaysia Conference on Photonics. NCTT-MCP 2008. 6th National Conference on, 2008

"A new multiplexing technique based on duty cycle division is proposed, thus the name Duty Cycle... more "A new multiplexing technique based on duty cycle
division is proposed, thus the name Duty Cycle Division
Multiplexing (DCDM). DCDM can be applied in both electrical
and optical domains, for wired and wireless systems. The new
technique allows for more efficient use of time slots as well as the
spectrum, taking advantage of both the conventional TDM and
FDM. In this paper, three channels operating at the same speed
of 10 Gbps per channel are multiplexed in the electrical domain.
The performance comparison is made against 3x10 Gbps TDM,
and the experimental simulation results show that the DCDM
system can support higher bit rate than TDM and also, it is less
sensitive to the chromatic dispersion effect."

Telecommunication Technologies 2008 and 2008 2nd Malaysia Conference on Photonics. NCTT-MCP 2008. 6th National Conference on, 2008

In this paper, duty cycle division multiplexing (DCDM) is proposed as an alternative multiplexin... more In this paper, duty cycle division multiplexing (DCDM)
is proposed as an alternative multiplexing technique. It can be
applied in any communication systems, although the focus in this
paper is in optical fiber communications. In this paper, we
examine 3 channels each operating at 10 Gbps modulation rate
over a single optical carrier. The performance comparison is
made against 30 Gbps RZ transmitted pulses, time domain
multiplexed (TDM). The results show that at a fixed transmission
power, DCDM can support longer distance than that with RZ
TDM technique. Also, the results show that RZ-TDM pulses
require 35.5 dB more SNR to support the same distance as that
for DCDM.

Computer and Communication Engineering, 2008. ICCCE 2008. International Conference on, 2008

A new multiplexing and demultiplexing technique for wireless communications which is called Abso... more A new multiplexing and demultiplexing technique
for wireless communications which is called Absolute
Polar Duty Cycle Division Multiplexing (APDCDM) is
presented in this paper. APDCDM can become an
alternative multiplexing technique in wireless
communications. The new technique allows for better
error detection, correction, clock recovery and more
efficient use of time slots as well as spectrum. The
principle of the APDCDM technique has been
discussed in this paper based on theoretical analysis as
well as simulation studies. The performance
comparison is made against time division multiplexing
technique (TDM). The simulation has been set for
wireless transmission, based on free space
propagation model with adaptive white Gaussian noise
(AWGN); QAM is used as modulation scheme to
evaluate this technique against data rate and number
of users. The simulation result correspond with the
theoretical study show that APDCDM has better
performance than TDM for supporting higher number
of multiplexing users and bit rate.

Telecommunication Technologies 2008 and 2008 2nd Malaysia Conference on Photonics. NCTT-MCP 2008. 6th National Conference on, 2008

In this study the author has modeled and characterizes the performance of 3X10 Gbp/s Absolute Po... more In this study the author has modeled and characterizes the
performance of 3X10 Gbp/s Absolute Polar Duty Cycle Division
(APDCDM) Multiplexing in dispersive environments at 1550 nm.
APDCDM technique is examined, with comparison to nonreturn-
to-zero (NRZ) and return-to-zero (RZ) Time Division
Multiplexing. In this paper three channel operating at the same
speed of 10 Gbps are multiplexed in electrical domain. The
experimental simulation results show that the receiver sensitivity
of all users in APDCDM system is similar to that of RZ- TDM
and 3 dB better than NRZ-TDM. The proposed system offer
reduced dispersion sensitivity; this suggests advantages for
APDCDM in optical multiplexing systems. It was also showed
that APDCDM can support higher bit rate than TDM and also, it
is less sensitive to the chromatic dispersion effect.

International Review of Electrical Engineering-Iree, 2008

A novel concepts of decision circuit and Bit-error-rate (BER) estimation method for Absolute Pola... more A novel concepts of decision circuit and Bit-error-rate (BER) estimation method for Absolute Polar Duty Cycle Division Multiplexing (AP-DCDM) is proposed The concepts have significant differences to those used in conventional microwave communication receivers. This is due to the unique characteristics of the multilevel signal produced in AP-DCDM system. The BER estimation method is validated by simulation and compared against bit-to-bit comparison method

Electronic Design, 2008. ICED 2008. International Conference on, 2008

In order to explore the potential of optical multilevel signaling for high speed optical fiber ne... more In order to explore the potential of optical multilevel signaling for high speed optical fiber networks, an absolute polar duty cycle division multiplexing (AP-DCDM) is demonstrated. Three users, each with the data rate of 10 Gb/s were successfully multiplexed and transmitted over a single WDM channel, which can offer a possible transmission rate of 30 Gb/s per WDM channel. The performance of AP-DCDM technique is examined, with comparison to 30 Gb/s Time Division Multiplexing (TDM) . Back-to-back receiver sensitivity of -29.2 dBm with OSNR of 22.5 dB was achieved for the worst user, together with the chromatic dispersion tolerance ranging from 207 ps/nm to 276 ps/nm. A comparison with conventional TDM technique shows a clear advantage of the proposed AP-DCDM technique.

Proceedings of the Fifth IASTED International Conference on Communication Systems and Networks, 2008

A new line encoding for duty cycle division multiplexing is proposed, under the name: Complementa... more A new line encoding for duty cycle division multiplexing is proposed, under the name: Complementary unipolar Division Multiplexing (CUDCDM). The basic properties based on theoretical analysis as well as simulation studies have been done to evaluate the performance of this technique based on the signal energy and symbol error rate (SER). In this paper the performance of Complementary unipolar DCDM compared with unipolar DCDM as well as the time division multiplexing (TDM) techniques. The simulation has been set for wireless transmission based on free space propagation model with adaptive white Gaussian noise (AWGN). PSK and QAM are used as modulation schemes to evaluate these techniques against data rates. The study shows that the energy per bit in complementary unipolar DCDM, unlike that of TDM technique, increases with the number of users. The simulation result shows that complementary unipolar DCDM has better SER than TDM and unipolar DCDM, even in more distances.

Photonic Network Communications, 2009

The performance of ASK over DCDM for up to seven channels is reported. The aggregate bit rate of... more The performance of ASK over DCDM for up to
seven channels is reported. The aggregate bit rate of 70 Gb/s
is achieved with only 160-GHz modulation bandwidth. The
clock and data recovery are realized at 10-GHz clock rate,
which is very economic and efficient. At 7 × 10 Gb/s, the
worst receiver sensitivity of−10 dBm, OSNR of 41.5 dB and
chromatic dispersion tolerance of ±17 ps/nm are achieved.
Whereas, for the best channel, the receiver sensitivity,OSNR,
and chromatic dispersion tolerance are −23.5dBm, 29dB,
and ±36 ps/nm, respectively.

2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009

We show the realization of 40 Gbit/s on-off-keyed system that can be recovered at 5.71 GHz clock ... more We show the realization of 40 Gbit/s on-off-keyed system that can be recovered at 5.71 GHz clock using duty cycle division multiplexing technique with the receiver sensitivity of -22.1 dBm.

Communications (MICC), 2009 IEEE 9th Malaysia International Conference on, 2009

Experimental demonstration of Duty Cycle Division Multiplexing (DCDM) is reported which validate... more Experimental demonstration of Duty Cycle Division
Multiplexing (DCDM) is reported which validates the potential
implementation of the system in communication field. We also
presented the operation of bit error rate (BER) estimation
algorithm, which is specially derived for DCDM. With the
increase of link attenuation, the signal amplitude decreased and
the pulses are distorted. BER estimation on the received signal
was performed and measured against transmission distance of
100 meter until 400 meter copper wire. It is shown that the
channel with the largest duty-cycle value shows the best
performance. The experimental eye diagrams at several distances
are also demonstrated and compared against their back-to-back
counterpart.

International Journal of Information and Communication Technology, 2009

Duty cycle division multiplexing (DCDM) is proposed as an alternative multiplexing technique. In ... more Duty cycle division multiplexing (DCDM) is proposed as an alternative multiplexing technique. In this technique, the channel multiplexing and demultiplexing are performed electrically. This technique allows aggregate bit rate to be recovered at the single channel bit rate, which is very economic. In this paper, we examine three channels system where each channel operates at 10 Gb/s over a single optical carrier. Performance of the system is evaluated based on back-to-back receiver sensitivity, optical signal-to-noise ratio (OSNR) and chromatic dispersion tolerance. The performance comparison is made against return-to-zero (RZ) format. The results show that, DCDM can support higher amount of chromatic dispersion than that RZ. At 3 × 40 Gb/s, a receiver sensitivity and OSNR of −16.8 dBm and 34.6 dB is respectively required for the worst DCDM channel.

Optical Review, Jul 2009

An improved estimation of bit-error-rate (BER) for electrically multiplexed duty-cycle division m... more An improved estimation of bit-error-rate (BER) for electrically multiplexed duty-cycle division multiplexing (E-DCDM), which is based on the probability of error, is presented. Performance of 3 x 10 Gbit/s E-DCDM is investigated in terms of optical signal-to-noise ratio (OSNR) and dispersion tolerance. This technique requires 29.4 dB OSNR and can tolerate +/- 96 ps/nm chromatic dispersion for the worst user.

Optics Communications, Nov 2009

The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength divi... more The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength division multiplexing (WDM) system is presented based on the simulation results. The AP-DCDM signal has narrower bandwidth than conventional time division multiplexing (TDM) signal, which makes its implementation in WDM system advantageous. In this paper, characteristics of AP-DCDM and TDM signals in WDM system are compared at the speed of 40 Gbit/s per channel, for the minimum allowed channel spacing and the chromatic dispersion tolerance. The results clearly show that AP-DCDM performs significantly better than TDM. By using AP-DCDM, 1.28 Tbit/s (32 x 40 Gbit/s) was successfully transmitted over 320 km standard single mode fiber. Spectral efficiency of 0.64 b/s/Hz was achieved by using 10 Gbit/s transmitters and receivers without polarization multiplexing.