Ahmed A. S. Dessouki

Read disturbance and temperature variation aware spintronic memristor model

A novel nonvolatile memory technology is needed to meet the increasing demand of large storage elements. Spintronic memristor is a promising candidate for emerging memory technologies. The spintronic memristor combines the non-volatility advantage of memristors, the good scalability, and radiation hardness of spin-transfer torque magnetic random access memories (STT-MRAMs). In this paper, a modified model of the spintronic memristor device is proposed. The model takes into account the read disturbance, and the temperature variation in spintronic memristor-based memory cells.

Low power differential three transistors two memristors based RRAM cell

This paper introduces a scheme of three transistors two memristors based memory cell. The write process connects the two memristors in series and the read process connects them in parallel. It utilizes the slowness property of the OFF memristive switching. The scheme uses the differential method of a sense amplifier. The write and read circuit schematics are shown. Simulation results are provided in terms of power and time delay under the use of 45 nm MOSFETs technology and the exponential memristor model. The proposed scheme is power efficient, and it shows good compatibility with the sub-micron MOSFETs models for both write and read processes.

The Resonant Tunneling Diode characterization for high frequency communication systems

Abstract In this paper, a detailed derivation process is proposed to characterize the Resonant Tunneling Diode (RTD) for high frequency regime. The proposed model is used to design and analyze a simple microwave oscillator based on the RTD using the commercial circuit simulation software, ADS from Agilent Technologies. The simulation is carried out using different equivalent circuit models; the proposed model, the original constant RC model, and the series/parallel double RC model, which is an alternative to the quantum-inductance RLC model. This is performed in terms of oscillation frequency and output power against resonant circuit elements, considering the CPU time. A comparison between the simulation results of the three models indicates that the proposed model is simple, accurate, and appropriate to investigate the behavior of the RTD at high frequency without any singularity and convergence problems. Also, its complexity (CPU time) is less than that of the series/parallel double RC model and higher than that of constant RC model. However, the constant RC model is inaccurate, especially in high frequency regime. In addition, the proposed technique can be easily incorporated into computer aided circuit design software, such as SPICE and ADS software, to simulate circuits containing RTD in high frequency regime. In brief, this work adds important contributions to the accurate characterization and modeling of RTDs and analyzes its based circuits in high frequency regime by addressing the problems of the current RTD equivalent circuit models.

An accurate memristor model based on a novel definition of memristance

A mathematical model of the memristor is introduced. This model presents an explicit definition of memristance and flexible window functions for positive and negative excitation signs to accommodate the highly nonlinear and asymmetric switching behavior. The model addresses issues found with other models, and it improves fitting accuracy with physical data. It combines the exponential tunneling current functions and the dopant drift memristance definition to adopt the theory of their co-participation to the memristive behavior. Also, a PSPICE code for the model is provided, and it shows good convergence and robustness for different simulated memristive structures. A comparison with some experimental results is given, and the proposed model shows good matching to them.

SA and PSO assisted joint scheme of channel estimation and PPIC for MIMO-SDMA/OFDM system

In this paper, a new scheme of Joint Channel Estimation and Partial Parallel Interference Cancellation using Simulating Annealing (SA) or Particle Swarm Optimization (PSO) algorithms is proposed. This scheme is proposed for multiuser Multiple-Input Multiple-Output /Space Division Multiple Access (MIMO-SDMA) Orthogonal Frequency Division Multiplexing (OFDM) systems. The proposed scheme tries to reduce the cancellation error in Conventional Parallel Interference Cancellation (CPIC) detection schemes used in MIMO SDMA-OFDM system. The SA and PSO algorithms are employed in searching the optimal weights of the PPIC for multiple access interference cancellation. The proposed scheme is shown to provide a performance improvement as compared to MMSE and CPIC detectors especially in an overloaded scenario where number of users is high as compared to the Base Station (BS) antennas. In this scenario, channel estimation becomes more challenging, owing to the increased number of independent transmitter-receiver links to be estimated and the constraint imposed by the rank of the MIMO channel matrix. The proposed scheme provides a reasonable solution to the multiuser MIMO channel estimation problem and multiuser detection in the above-mentioned overloaded scenario.

Performance of PSO and SA assisted joint scheme of channel estimation and PPIC in MIMO-SDMA/OFDM over-loaded system

In this paper, a novel Joint Channel Estimation and Partial Parallel Interference Cancellation (PPIC) scheme using Simulating Annealing (SA) or Particle Swarm Optimization (PSO) algorithms is proposed. This scheme is proposed for multiuser Multiple-Input Multiple-Output / Space Division Multiple Access (MIMO-SDMA) Orthogonal Frequency Division Multiplexing (OFDM) systems. The SA and PSO algorithms are employed in searching the optimal weights of the PPIC for multiple access interference cancellation. The proposed scheme is shown to provide a performance improvement as compared to MMSE and CPIC detectors especially in an overloaded scenario where number of users exceeds the Base Station (BS) antennas. In overloaded scenario, the channel coefficients become more difficult to be estimated, due to the difficulties imposed by the MIMO channel matrix rank. The proposed scheme presents an efficient solution to the multiuser detection and the MIMO channel matrix estimation dilemma in overloaded scenario.