Quantum Dot Cellular Automata Check Node Implementation for LDPC Decoders

The quantum dot Cellular Automata (QCA) is an emerging nanotechnology that has gained significant research interest in recent years. Extremely small feature sizes, ultralow power consumption, and high clock frequency make QCA a potentially attractive solution for implementing computing architectures at the nanoscale. To be considered as a suitable CMOS substitute, the QCA technology must be able to implement complex real-time applications with affordable complexity. Low density parity check (LDPC) decoding is one of such applications. The core of LDPC decoding lies in the check node (CN) processing element which executes actual decoding algorithm and contributes toward overall performance and complexity of the LDPC decoder. This study presents a novel QCA architecture for partial parallel, layered LDPC check node. The CN executes Normalized Min Sum decoding algorithm and is flexible to support CN degree dc up to 20. The CN is constructed using a VHDL behavioral model of QCA elementary circuits which provides a hierarchical bottom up approach to evaluate the logical behavior, area, and power dissipation of the whole design. Performance evaluations are reported for the two main implementations of QCA i.e. molecular and magneti

Nanoarchitecture of Quantum-Dot Cellular Automata (QCA) Using Small Area for Digital Circuits

Novel digital technologies always lead to high density and very low power consumption. One of these concepts—quantum-dot cellular automata (QCA), which is one of the new emerging nanotechnologies, is based on Coulomb repulsion. This chapter presents a novel design of 2-input Exclusive-NOR (XNOR)/Exclusive-OR (XOR) gates with 3-input Exclusive-NOR (XNOR) gates which are composed of 10 cells on 0.006 μm2 of area. A novel architecture of 3-input Exclusive-OR (XOR) gate is defined by 12 cells on 0.008 μm2 of area. The proposed design of 2-input XOR/XNOR gate structures provide less area and low complexity than the best reported design. The simulation results of proposed designs have been achieved using QCA Designer tool version 2.0.3

Hybrid Quantum-Dot Cellular Automata Nanocomputing Circuits

Quantum-dot cellular automata (QCA) is an emerging transistor-less field-coupled nanocomputing (FCN) approach to ultra-scale ‘nanochip’ integration. In QCA, to represent digital circuitry, electrostatic repulsion between electrons and the mechanism of electron tunnelling in quantum dots are used. QCA technology can surpass conventional complementary metal oxide semiconductor (CMOS) technology in terms of clock speed, reduced occupied chip area, and energy efficiency. To develop QCA circuits, irreversible majority gates are typically used as the primary components. Recently, some studies have introduced reversible design techniques, using reversible majority gates as the main building block, to develop ultra-energy-efficient QCA circuits. However, this approach resulted in time delays, an increase in the number of QCA cells used, and an increase in the chip area occupied. This work introduces a novel hybrid design strategy employing irreversible, reversible, and partially reversible QCA gates to establish an optimal balance between power consumption, delay time, and occupied area. This hybrid technique allows the designer to have more control over the circuit characteristics to meet different system needs. A combination of reversible, irreversible, and innovative partially reversible majority gates is used in the proposed hybrid design method. We evaluated the hybrid design method by examining the half-adder circuit as a case study. We developed four hybrid QCA half-adder circuits, each of which simultaneously incorporates various types of majority gates. The QCADesigner-E 2.2 simulation tool was used to simulate the performance and energy efficiency of the half-adders. This tool provides numerical results for the circuit input/output response and heat dissipation at the physical level within a microscopic quantum mechanical model.N/

Cellular Automata

Modelling and simulation are disciplines of major importance for science and engineering. There is no science without models, and simulation has nowadays become a very useful tool, sometimes unavoidable, for development of both science and engineering. The main attractive feature of cellular automata is that, in spite of their conceptual simplicity which allows an easiness of implementation for computer simulation, as a detailed and complete mathematical analysis in principle, they are able to exhibit a wide variety of amazingly complex behaviour. This feature of cellular automata has attracted the researchers' attention from a wide variety of divergent fields of the exact disciplines of science and engineering, but also of the social sciences, and sometimes beyond. The collective complex behaviour of numerous systems, which emerge from the interaction of a multitude of simple individuals, is being conveniently modelled and simulated with cellular automata for very different purposes. In this book, a number of innovative applications of cellular automata models in the fields of Quantum Computing, Materials Science, Cryptography and Coding, and Robotics and Image Processing are presented

Asynchronous Solutions for Nano-Magnetic Logic Circuits

In the years to come new solutions will be required to overcome the limitations of scaled CMOS technology. One approach is to adopt Nano-Magnetic Logic Circuits, highly appealing for their extremely reduced power consumption. Despite the interesting nature of this approach, many problems arise when this technology is considered for real designs. The wire is the most critical of these problems from the circuit implementation point of view. It works as a pipelined interconnection, and its delay in terms of clock cycles depends on its length. Serious complications arise at the design phase, both in terms of synthesis and of physical design. One possible solution is the use of a delay insensitive asynchronous logic, Null Convention Logic (NCL TM ). Nevertheless its use has many negative consequences in terms of area occupation and speed loss with respect to a Boolean version. In this article we analyze and compare different solutions: nanomagnetic circuits based on full NCL, mixed Boolean-NCL, and fully Boolean logic. We discuss the advantages of these logics, but also the issues they raise. In particular we analyze feedback signals, which, due to their intrinsic pipelined nature, cause errors that still have not found a solution in the literature. The innovative arrangement we propose solves most of the problems and thus soundly increases the knowledge of this technology. The analysis is performed using a VHDL behavioral model we developed and a microprocessor we designed based on this model, as a sound and realistic test bench. </jats:p