Papers presented at international conferences
[1] H. Saghaei and B. Seyfe, “The new approach to closed-loop power control algorithm in cellular wireless CDMA systems under multipath fading,” in Proc. IEEE WiCom’08, pp. 1-4, 2008. DOI: 10.1109/WiCom.2008.66
This paper proposes a new approach to the closed-loop power control algorithm with decision feedback, called the NAPC-DF algorithm. In this algorithm, the step size of the transmitting power by the mobile station (MS) in the uplink channel is variable and adjusted by the received command from the base station (BS) and channel conditions. This algorithm is compared with fixed-step, variable step, and adaptive step closed-loop power control with decision feedback (FSPC-DF, VSPC-DF, and ASPC-DF, respectively). Numerical results indicate that the NAPC-DF algorithm, under fading can significantly improve the radio network capacity without any increase in power control signaling. Also, the speed of convergence and stability against loop delay can be increased and it decreases the outage probability and bit error rate (BER) of the uplink channel in comparison with the mentioned references algorithms.
[2] H. Saghaei and A. A. L. Neyestanak, “Variable step closed-loop power control in cellular wireless CDMA systems under multipath fading,” in Proc. IEEE PACRIM'07, pp. 157-160, 2007. DOI: 10.1109/PACRIM.2007.4313201
Power control has been widely studied and shown to be crucial for the capacity and performance of direct-sequence code-division multiple-access (DS-CDMA) systems. Practical implementations typically employ fast closed-loop power control, where transmitters adjust their transmit powers according to commands received in a feedback channel. The loop delay resulting from the measurements, processing, and transmission of the power control commands can result in oscillations of the transmission powers and lead to degradation in the system performance. In this paper, we present a new variable step closed-loop power control algorithm (VSPC) and fixed-step closed-loop power control with information feedback (FSPC-IF), that are able to increase the speed of convergence and alleviate the effect of the loop delay. We carried out computational experiments on a DS-CDMA network using these algorithms. Fixed-step power control with decision feedback (FSPC-DF) is a reference algorithm. New algorithms are compared with it. The numerical results indicate that new algorithms can significantly improve the radio network capacity without any increase in power control signaling, also increase the speed of convergence, and decrease loop delay.
[3] H. Saghaei and B. Seyfe, “Power control with diversity antenna arrays in CDMA wireless cellular systems under multipath fading,” in Proc. IEEE WiCom’08, pp. 1-4, 2008. DOI: 10.1109/WiCom.2008.15
In this paper, we present numerical results to show the performance of power control (PC) by using antenna arrays at the base station (BS). We show that the diversity generated by the antenna array, decreases the outage probability, the bit error rate (BER), the fluctuations of the received signal to interference ratio (SIR) over the target SIR, the transmitted power level, and finally increases the speed of convergence of power control algorithms in compared without diversity. These results also increase the system capacity and the quality of service (QoS).
[4] A. R. Abadchi, A. Seifi, and H. Saghaei, “Minimizing the Connection Cost in a Real GSM Network,” in Proc. IEEE WiCom’10, pp. 1-4, 2010. DOI: 10.1109/WICOM.2010.5601418
Wise resource allocation is necessary to increase the quality of service (QoS), the system capacity, the network performance, and also decrease the power consumption and connection cost. This paper, first, investigates the located global system for mobile (GSM) network in a region of Tehran province in Iran as a case of study and then proposes a novel approach to minimize the connection cost among different parts and components of the GSM network while considering our network practical constraints. The approach of this paper can also be used for the other network planning problems such as the universal mobile telecommunication system (UMTS) in the third generation of the mobile systems. In order to find an optimal solution for the total network connections cost, we use mathematical programming based on mixed integer programming (MIP) algorithm to minimize the connection cost. At the end, simulation and practical results show us that our proposed algorithm decreases the connection cost and improve the QoS of the GSM network.
[5] M. Ebnali-Heidari, H. Saghaei, C. Monat, C. Grillet, “Four-wave Mixing Based Mid-span Phase Conjugation using slow light engineered Chalcogenide and silicon photonic crystal waveguides,” IEEE., Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), Germany, May, 2011. DOI: 10.1109/CLEOE.2011.5942694
The goal of this paper is to demonstrate numerically, the mid-span phase conjugation using slow light engineered 80 μm Chalcogenide PhC. Mid-span phase conjugation has significant advantages over other methods such as being independent of pulse shape, power, modulation format and bit-rate. We calculate the FWM efficiency for the various waveguides (3mm ridge (black dotted line), 80 μm Si PhC (blue line), and 80 μm Chalcogenide PhC (AMTIR) (red line)) when setting the pump wavelength in the middle of the flatband slow light window.
[6] H. Saghaei, F. Koohi-Kamali, F. Deghan, M. Ebnali-Heidari, and M. K. Moravvej-Farshi “Supercontinuum generation in square lattice photonic crystal fiber using optofluidic infiltration,” The 18th Iranian Conference on Optics and Photonics (ICOP2012), Tabriz, Iran, 2012.
[7] M. Ebnali-Heidari, H. Saghaei, and M. K. Moravvej-Farshi “Design and modeling of a 1×N all-optical Mach_Zehnder switch controlled by wavelength and input power,” The 18th Iranian Conference on Optics and Photonics (ICOP2012), Tabriz, Iran, 2012.
[8] M. Hosseinpour, M. Ebnali-Heidari, H. Saghaei, and M. K. Moravvej-Farshi, “Loss Engineering using Selective Optofluidic Infiltration in the slow light Regime within Photonic Crystal Waveguides,” The 18th Iranian Conference on Optics and Photonics (ICOP2012), Tabriz, Iran, 2012.
[9] F. Koohi-Kamali, H. Saghaei, M. Ebnali-Heidari, and M. K. Moravvej-Farshi, “Supercontinuum generation through honeycomb photonic crystal fiber in the Visible spectral region,” 20th Iranian Conference on Electrical Engineering (ICEE2012), Tehran, Iran, 2012.
[10] F. Koohi-Kamali, H. Saghaei, M. Ebnali- Heidari, and M. K. Moravvej-Farshi, “Design of double-core photonic crystal fiber coupler by means of optofluidic infiltration,” The 19th Iranian Conference on Optics and Photonics (ICOP2013), Zahedan, Iran, 2013.
[11] H. Saghaei, F. Koohi-Kamali, M. K. Moravvej-Farshi, and M. Ebnali-Heidari, “Supercontinuum generation in square lattice photonic crystal fiber using optofluidic infiltration,” The 20th Iranian Conference on Optics and Photonics (ICOP2014), Shiraz, Iran, 2014.
[12] H. Saghaei, M. K. Moravvej-Farshi, and M. Ebnali-Heidari, “Visible supercontinuum generation in silica-based photonic crystal fiber in normal dispersion regime,” The 21th Iranian Conference on Optics and Photonics (ICOP2015), Tehran, Iran, 2015.