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Papers by Syed Iftekhar Ali

International Journal of Electronics, 2021

Memristor-based combinational logic is one of the unique concepts of designing digital circuits t... more Memristor-based combinational logic is one of the unique concepts of designing digital circuits to achieve compact design, faster operation, and lesser power consumption. This work presents a uniqu...

Low Density Parity Check (LDPC) codes have attracted current researchers due to their excellent p... more Low Density Parity Check (LDPC) codes have attracted current researchers due to their excellent performance and capability of parallel decoding. One major criticism concerning LDPC codes has been their apparent high encoding complexity and memory inefficient nature due to large parity check matrix. This led the researchers to move into a memory efficient LDPC called Quasi-Cyclic (QC)-LDPC which shows the similar performance as LDPC does. This review gives a theoretical and analytical survey on different encoding schemes for QC-LDPC codes. The encoding schemes are categorized in three broad categories. These schemes are then analyzed under those three broad fields. Also different encoding schemes are compared. Key-Words: LDPC, QC-LDPC, efficient encoding, Richardson, Low complexity

International Journal of Electronics, 2019

ABSTRACT Memory-resistor (Memristor) has drawn considerable attention of the researchers in the l... more ABSTRACT Memory-resistor (Memristor) has drawn considerable attention of the researchers in the last decade due to its remarkable properties. After the first concept of memristor, proposed by Leon Chua in 1971, almost no research work was conducted in this field for a long time. However, since the revolutionary discovery of the physical structure of memristor and its model of the HP lab in 2008, a tremendous amount of research work has been going on. Researchers are focusing on improving the models for the analysis of the memristor. Different researchers have come up with their model to improve the existing ones. These models can be linear, nonlinear or exponential. To overcome the boundary problem, many window functions have been proposed. Different models have their explanations of voltage-current relationship and state variable derivatives. This paper presents a detailed review and a comparative study of the existing memristor models based on their I-V characteristic curve. Original experimental I–V curve from the HP lab has been used as the reference for comparison.

Journal of Circuits, Systems and Computers, 2019

Network routers use ternary content addressable memory (TCAM) for high-speed table look-up. A mat... more Network routers use ternary content addressable memory (TCAM) for high-speed table look-up. A match-line (ML) sensing scheme for TCAM combining charge-sharing and positive feedback is presented. The objective is to simplify the ML sense amplifier (MLSA) of existing charge-sharing scheme while reducing ML energy consumption during look-up. The look-up has been performed in two steps. In the first step, a segment of each TCAM word is compared with the search key to detect large percentage of the mismatched words. The detected mismatched words are deactivated in the second step to reduce energy consumption. In the second step, the charge stored in a matched ML first segment is shared with second ML segment. Use of positive feedback in this step makes the MLSA circuit simple. Post-layout simulations implemented using 180[Formula: see text]nm 1.8[Formula: see text]V CMOS logic have been performed. In addition to lower scheme complexity and 16.5% reduction in circuit area, the proposed sc...

Journal of Optical Communications, 2018

A novel photonic crystal fiber (PCF) based on TOPAS, consisting only rectangular slots is present... more A novel photonic crystal fiber (PCF) based on TOPAS, consisting only rectangular slots is presented and analyzed in this paper. The PCF promises not only an extremely low effective material loss (EML) but also a flattened dispersion over a broad frequency range. The modal characteristics of the proposed fiber have been thoroughly investigated using finite element method. The fiber confirms a low EML of 0.009 to 0.01 cm−1 in the frequency range of 0.77–1.05 THz and a flattened dispersion of 0.22±0.01 ps/THz/cm. Besides, some other significant characteristics like birefringence, single mode operation and confinement loss have also been inspected. The simplicity of the fiber makes it easily realizable using the existing fabrication technologies. Thus it is anticipated that the new fiber has the potential to ensure polarization preserving transmission of terahertz signals and to serve as an efficient medium in the terahertz frequency range.

Journal of Circuits, Systems and Computers, 2016

Content addressable memory (CAM) can perform high-speed table look-up with bit level masking capa... more Content addressable memory (CAM) can perform high-speed table look-up with bit level masking capability. This feature makes CAMs extremely attractive for high-speed packet forwarding and classification in network routers. High-speed look-up implies all the CAM word entries to be accessed and compared with a search word to find a suitable match in a single clock cycle. This parallel search activity requires large energy consumption which needs to be reduced. In this paper, a review of the energy reduction techniques of CAM is presented. A comparative study of some popular techniques has been made with the help of simulations carried out in this work and published results.

2014 IEEE International Symposium on Circuits and Systems (ISCAS), 2014

ABSTRACT An improved match line (ML) sensing scheme for ternary content addressable memory (TCAM)... more ABSTRACT An improved match line (ML) sensing scheme for ternary content addressable memory (TCAM) is presented in this paper. Selective precharge combined with charge sharing technique reduces ML search energy consumption. Use of lower Vt transistors in the sense amplifier allows further reduction of energy. Series gating transistor eliminates energy consumption associated with increased leakage of lower Vt MOSFETs. Simulations are performed using 180 nm 1.8 V CMOS logic in HSPICE. For similar search speed, the proposed scheme shows minimum 24% and 35% energy reductions compared to two existing similar sensing schemes.

2012 7th International Conference on Electrical and Computer Engineering, 2012

ABSTRACT This paper presents a match line (ML) sensing scheme based on current race (CR) type mat... more ABSTRACT This paper presents a match line (ML) sensing scheme based on current race (CR) type match line sense amplifier (MLSA). The MLSA uses feedback mechanism twice in order to decrease currents to the mismatched MLs. This reduces the energy consumption and increases voltage margin while maintaining high search speed. Simulation using 130nm 1.2V CMOS logic shows large improvement in voltage margin and ~59% reduction in ML energy consumption compared to conventional CR scheme of similar speed. The proposed technique also shows better performance compared to existing CR-type techniques employing single feedback.

International Conference on Electrical & Computer Engineering (ICECE 2010), 2010

This paper presents a match-line architecture to reduce the energy consumption of Ternary content... more This paper presents a match-line architecture to reduce the energy consumption of Ternary content-addressable memory (TCAM) and to increase search speed. The proposed match-line (ML) sensing scheme uses a two-step comparison to filter out most of the mismatched MLs in the first step so that the second step comparison is never activated for those mismatched MLs. Simulation using 130-nm 1.2-V

2011 NORCHIP, 2011

A new match line sensing scheme for ternary content addressable memory (TCAM) is presented in thi... more A new match line sensing scheme for ternary content addressable memory (TCAM) is presented in this paper. Selective precharge is combined with charge sharing technique to reduce the match line (ML) energy consumption. Simulation performed using 130nm 1.2V CMOS logic shows minimum ∼35% dynamic energy reduction compared to current race (CR) scheme. The technique also achieves ∼41% speed improvement. Unlike many existing schemes, the proposed scheme uses minimum number of control signals which need to be generated off-chip. Also, there is no analog control signal requiring manual tuning as has been used in CR or many CR-like schemes.

Microelectronics Journal, 2014

Ternary content addressable memory (TCAM) has become popular in applications requiring high-speed... more Ternary content addressable memory (TCAM) has become popular in applications requiring high-speed table lookup. This paper presents a match-line (ML) sensing scheme to reduce dynamic energy consumption in MLs during the table lookup operation. Positive feedback has been used twice in the ML sense amplifier to achieve improved performance over existing schemes employing single feedback. Post-layout simulation of the scheme implemented using 180 nm 1.8 V CMOS logic shows that it can have match detection time as small as 907 ps. The scheme can also provide large voltage margin of 734 mV. Compared to popular current-race sensing scheme, the proposed scheme offers 83.8% energy reduction. It can achieve 64.5%, 74.7% and 77.8% energy savings compared to existing feedback schemes namely mismatch dependent, active feedback and resistive feedback, respectively. The energy saving is even larger for more advanced technology node.

Journal of Computers, 2012

IETE Journal of Research, 2015

An alternative protocol for in vitro propagation of Picrorhiza scrophulariiflora is described usi... more An alternative protocol for in vitro propagation of Picrorhiza scrophulariiflora is described using bavistin and adenine sulphate. The explants differentiated into multiple shoot buds on MS supplemented with various concentrations of bavistin and adenine sulphate ranging from 0-400 mg/l either alone or in combination. Maximum number of multiple shoots were obtained on MS containing the combination of bavistin (100 mg/l) and adenine sulphate (100 mg/l). In this combination as high as 28 shoots per explant was achieved and also vetrification of the cultures were not recorded. This study also demonstrates that the bavistin has stronger cytokinin-like activity than adenine sulphate. For instance, it was observed that bavistin alone in the concentration of 300 mg/l produced as high as 24 shoots per explant, however, adenine sulphate (100 mg/l) could produce a maximum of 18 shoots per explant. Moreover, higher or lower concentration did not improve the shoot multiplication. The microshoots were separated from the multiple shoots and transferred to MS containing various concentrations of auxins. Among them, NAA (1 mg/l) produced as high as 6 roots per explant. The regenerated plantlets were hardened in plastic cups (6 x 8 cm) containing 9 : 1 virgin soil and soil at Kyongnosla nursery and acclimated for four weeks. A 90% survival rate of the plants was recorded after 60 days.