Nasrollahi, Seyed Amirhossein (2022) Input-Layer Neuron Design for Spiking Neural Network Application. Masters thesis, Concordia University.
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Abstract
Artificial Intelligence and Machine Learning algorithms help humans in various applications. Neural Networks systems are one of this area’s most important research topics, inspired by the human brain. In this field, Spiking Neural Networks (SNN) use spikes to communicate between neurons mimicking the brain’s algorithm. The input data produced by sensors has to be converted to spikes for training and testing these systems. Rate encoding is a popular method that encodes the input signal into the spiking frequency.
This work presents two methods to design an analog input encoder that receives the information and converts them to spiking output. Both ways use a ∆Σ modulator to create a digital output from the input signal. The first input encoder, called synchronous ∆Σ analog to spike converter, reads the digital output of the ∆Σ and produces a spike for every ’1’ bit. The second design is called neuromorphic ∆Σ analog to spike converter, which uses a synapse and neuron model to produce the rate-encoded spiking output. The synapse converts the ∆Σ output to a current, and the neuron receives this current at its input.
This thesis is the first design to build a general input encoder that can be used in most SNN systems. A clock signal can change the firing frequency of both encoders. The synchronous ∆Σ A-S converter can perform for clock signals between 1 kHz and 4 MHz, while the neuromorphic one can perform between 1 kHz and 2 MHz. The optimized clock frequency is 50 kHz for both of them. With this clock, the synchronous one’s accuracy is 99.2% encoding a DC input, and its input can have a maximum bandwidth of 120 Hz to achieve an SNR higher than 50 dB. It consumes 13.4 μW average power with 500 μm2 area. The neuromorphic one’s accuracy for DC inputs is 97.3%, and its maximum bandwidth is 65 Hz. It consumes 12.7 μW average power with 0.011 mm2 area.
| Divisions: | Concordia University > Gina Cody School of Engineering and Computer Science > Electrical and Computer Engineering |
|---|---|
| Item Type: | Thesis (Masters) |
| Authors: | Nasrollahi, Seyed Amirhossein |
| Institution: | Concordia University |
| Degree Name: | M.A. Sc. |
| Program: | Electrical and Computer Engineering |
| Date: | 7 December 2022 |
| Thesis Supervisor(s): | Cowan, Glenn |
| Keywords: | ∆Σ modulator, integrate and fire neuron, neuromorphic computing, spiking neural network |
| ID Code: | 991540 |
| Deposited By: | Seyed Amirhossein Nasrollahi |
| Deposited On: | 21 Jun 2023 14:36 |
| Last Modified: | 21 Jun 2023 14:36 |
References:
@article{Mead_1990,doi = {10.1109/5.58356},
url = {https://doi.org/10.1109\%2F5.58356},
year = 1990,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {78},
number = {10},
pages = {1629--1636},
author = {C. Mead},
title = {Neuromorphic electronic systems},
journal = {Proceedings of the {IEEE}}
}
@article{Eliasmith_2012,
doi = {10.1126/science.1225266},
url = {https://doi.org/10.1126\%2Fscience.1225266},
year = 2012,
month = {nov},
publisher = {American Association for the Advancement of Science ({AAAS})},
volume = {338},
number = {6111},
pages = {1202--1205},
author = {Chris Eliasmith and Terrence C. Stewart and Xuan Choo and Trevor Bekolay and Travis DeWolf and Yichuan Tang and Daniel Rasmussen},
title = {A Large-Scale Model of the Functioning Brain},
journal = {Science}
}
@incollection{Lek_2008,
doi = {10.1016/b978-008045405-4.00173-7},
url = {https://doi.org/10.1016\%2Fb978-008045405-4.00173-7},
year = 2008,
publisher = {Elsevier},
pages = {237--245},
author = {S. Lek and Y.S. Park},
title = {Artificial Neural Networks},
booktitle = {Encyclopedia of Ecology}
}
@article{Hodgkin_1952,
doi = {10.1113/jphysiol.1952.sp004764},
url = {https://doi.org/10.1113\%2Fjphysiol.1952.sp004764},
year = 1952,
month = {aug},
publisher = {Wiley},
volume = {117},
number = {4},
pages = {500--544},
author = {A. L. Hodgkin and A. F. Huxley},
title = {A quantitative description of membrane current and its application to conduction and excitation in nerve},
journal = {The Journal of Physiology}
}
@article{Indiveri_2011,
doi = {10.3389/fnins.2011.00073},
url = {https://doi.org/10.3389\%2Ffnins.2011.00073},
year = 2011,
publisher = {Frontiers Media {SA}},
volume = {5},
author = {Giacomo Indiveri and Bernab{\'{e}} Linares-Barranco and Tara Julia Hamilton and Andr{\'{e}} van Schaik and Ralph Etienne-Cummings and Tobi Delbruck and Shih-Chii Liu and Piotr Dudek and Philipp Häfliger and Sylvie Renaud and Johannes Schemmel and Gert Cauwenberghs and John Arthur and Kai Hynna and Fopefolu Folowosele and Sylvain Saighi and Teresa Serrano-Gotarredona and Jayawan Wijekoon and Yingxue Wang and Kwabena Boahen},
title = {Neuromorphic Silicon Neuron Circuits},
journal = {Frontiers in Neuroscience}
}
@book{baker_cmos,
author={R. J. Baker},
booktitle={CMOS: Mixed-Signal Circuit Design},
title ={CMOS: Mixed-Signal Circuit Design},
edition={2nd},
publisher={Wiley-IEEE},
year={2008},
url={http://CMOSedu.com}
}
@inproceedings{Danial_2019,
doi = {10.1109/iscas.2019.8702621},
url = {https://doi.org/10.1109\%2Fiscas.2019.8702621},
year = 2019,
month = {may},
publisher = {{IEEE}},
author = {Loai Danial and Sidharth Thomas and Shahar Kvatinsky},
title = {Delta-Sigma Modulation Neurons for High-Precision Training of Memristive Synapses in Deep Neural Networks},
booktitle = {2019 {IEEE} International Symposium on Circuits and Systems ({ISCAS})}
}
@inproceedings{Mahajan_2011,
doi = {10.1109/cicn.2011.36},
url = {https://doi.org/10.1109\%2Fcicn.2011.36},
year = 2011,
month = {oct},
publisher = {{IEEE}},
author = {Divya Mahajan and Vippan Kakkar and Amit Kumar Singh},
title = {Analysis of Delta Sigma Modulator},
booktitle = {2011 International Conference on Computational Intelligence and Communication Networks}
}
@BOOK{Gerstner2014-gm,
title = "Neuronal dynamics",
author = "Gerstner, Wulfram and Kistler, Werner M and Naud, Richard and
Paninski, Liam",
publisher = "Cambridge University Press",
month = jul,
year = 2014,
address = "Cambridge, England"
}
@inproceedings{DhanyaE2015,
doi = {10.1109/erect.2015.7499056},
url = {https://doi.org/10.1109/erect.2015.7499056},
year = {2015},
month = dec,
publisher = {{IEEE}},
author = {Dhanya E and N. Pradhan and Sunitha R and A. Sreedevi},
title = {Analysis of the dynamic behaviour of a single Hodgkin-Huxley neuron model},
booktitle = {2015 International Conference on Emerging Research in Electronics, Computer Science and Technology ({ICERECT})}
}
@article{Izhikevich2003,
doi = {10.1109/tnn.2003.820440},
url = {https://doi.org/10.1109/tnn.2003.820440},
year = {2003},
month = nov,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {14},
number = {6},
pages = {1569--1572},
author = {E.M. Izhikevich},
title = {Simple model of spiking neurons},
journal = {{IEEE} Transactions on Neural Networks}
}
@article{vanSchaik2001,
doi = {10.1016/s0893-6080(01)00067-3},
url = {https://doi.org/10.1016/s0893-6080(01)00067-3},
year = {2001},
month = jul,
publisher = {Elsevier {BV}},
volume = {14},
number = {6-7},
pages = {617--628},
author = {A. van Schaik},
title = {Building blocks for electronic spiking neural networks},
journal = {Neural Networks}
}
@article{Abbott1999,
doi = {10.1016/s0361-9230(99)00161-6},
url = {https://doi.org/10.1016/s0361-9230(99)00161-6},
year = {1999},
month = nov,
publisher = {Elsevier {BV}},
volume = {50},
number = {5-6},
pages = {303--304},
author = {L.F Abbott},
title = {Lapicque's introduction of the integrate-and-fire model neuron (1907)},
journal = {Brain Research Bulletin}
}
@inproceedings{Indiveri2010,
doi = {10.1109/iscas.2010.5536980},
url = {https://doi.org/10.1109/iscas.2010.5536980},
year = {2010},
month = may,
publisher = {{IEEE}},
author = {Giacomo Indiveri and Fabio Stefanini and Elisabetta Chicca},
title = {Spike-based learning with a generalized integrate and fire silicon neuron},
booktitle = {Proceedings of 2010 {IEEE} International Symposium on Circuits and Systems}
}
@article{Chicca2014,
doi = {10.1109/jproc.2014.2313954},
url = {https://doi.org/10.1109/jproc.2014.2313954},
year = {2014},
month = sep,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {102},
number = {9},
pages = {1367--1388},
author = {Elisabetta Chicca and Fabio Stefanini and Chiara Bartolozzi and Giacomo Indiveri},
title = {Neuromorphic Electronic Circuits for Building Autonomous Cognitive Systems},
journal = {Proceedings of the {IEEE}}
}
@article{Hazan2021,
doi = {10.3389/fnins.2021.627221},
url = {https://doi.org/10.3389/fnins.2021.627221},
year = {2021},
month = feb,
publisher = {Frontiers Media {SA}},
volume = {15},
author = {Avi Hazan and Elishai Ezra Tsur},
title = {Neuromorphic Analog Implementation of Neural Engineering Framework-Inspired Spiking Neuron for High-Dimensional Representation},
journal = {Frontiers in Neuroscience}
}
@article{Rabii1997,
doi = {10.1109/4.585245},
url = {https://doi.org/10.1109/4.585245},
year = {1997},
month = jun,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {32},
number = {6},
pages = {783--796},
author = {S. Rabii and B.A. Wooley},
title = {A 1.8-V digital-audio sigma-delta modulator in 0.8-$\upmu$m {CMOS}},
journal = {{IEEE} Journal of Solid-State Circuits}
}
@inproceedings{Krishna2021,
doi = {10.1109/icses52305.2021.9633907},
url = {https://doi.org/10.1109/icses52305.2021.9633907},
year = {2021},
month = sep,
publisher = {{IEEE}},
author = {Mikhili Murali Krishna and M Vadivel},
title = {Design and Analysis of First Order Sigma-Delta Modulator Based on Switched Capacitor Integrator (130nm)},
booktitle = {2021 International Conference on Innovative Computing, Intelligent Communication and Smart Electrical Systems ({ICSES})}
}
@inproceedings{Nasrollahi2022,
doi = {10.1109/newcas52662.2022.9842225},
url = {https://doi.org/10.1109/newcas52662.2022.9842225},
year = {2022},
month = jun,
publisher = {{IEEE}},
author = {Seyed Amirhossein Nasrollahi and Anatoly Syutkin and Glenn Cowan},
title = {Input-Layer Neuron Implementation Using Delta-Sigma Modulators},
booktitle = {2022 20th {IEEE} Interregional {NEWCAS} Conference ({NEWCAS})}
}
@article{Sharifshazileh2021,
doi = {10.1038/s41467-021-23342-2},
url = {https://doi.org/10.1038/s41467-021-23342-2},
year = {2021},
month = may,
publisher = {Springer Science and Business Media {LLC}},
volume = {12},
number = {1},
author = {Mohammadali Sharifshazileh and Karla Burelo and Johannes Sarnthein and Giacomo Indiveri},
title = {An electronic neuromorphic system for real-time detection of high frequency oscillations ({HFO}) in intracranial {EEG}},
journal = {Nature Communications}
}
@article{SubbulakshmiRadhakrishnan2021,
doi = {10.1038/s41467-021-22332-8},
url = {https://doi.org/10.1038/s41467-021-22332-8},
year = {2021},
month = apr,
publisher = {Springer Science and Business Media {LLC}},
volume = {12},
number = {1},
author = {Shiva Subbulakshmi Radhakrishnan and Amritanand Sebastian and Aaryan Oberoi and Sarbashis Das and Saptarshi Das},
title = {A biomimetic neural encoder for spiking neural network},
journal = {Nature Communications}
}
@article{Liu2020,
doi = {10.1002/aisy.202000150},
url = {https://doi.org/10.1002/aisy.202000150},
year = {2020},
month = dec,
publisher = {Wiley},
volume = {3},
number = {2},
pages = {2000150},
author = {Dingbang Liu and Hao Yu and Yang Chai},
title = {Low-Power Computing with Neuromorphic Engineering},
journal = {Advanced Intelligent Systems}
}
@inproceedings{Han2016,
doi = {10.1109/ijcnn.2016.7727303},
url = {https://doi.org/10.1109/ijcnn.2016.7727303},
year = {2016},
month = jul,
publisher = {{IEEE}},
author = {Bing Han and Abhronil Sengupta and Kaushik Roy},
title = {On the energy benefits of spiking deep neural networks: A case study},
booktitle = {2016 International Joint Conference on Neural Networks ({IJCNN})}
}
@article{Indiveri2015,
doi = {10.1109/jproc.2015.2444094},
url = {https://doi.org/10.1109/jproc.2015.2444094},
year = {2015},
month = aug,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {103},
number = {8},
pages = {1379--1397},
author = {Giacomo Indiveri and Shih-Chii Liu},
title = {Memory and Information Processing in Neuromorphic Systems},
journal = {Proceedings of the {IEEE}}
}
@article{Aamir2018,
doi = {10.1109/tbcas.2018.2848203},
url = {https://doi.org/10.1109/tbcas.2018.2848203},
year = {2018},
month = oct,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {12},
number = {5},
pages = {1027--1037},
author = {Syed Ahmed Aamir and Paul Muller and Gerd Kiene and Laura Kriener and Yannik Stradmann and Andreas Grubl and Johannes Schemmel and Karlheinz Meier},
title = {A Mixed-Signal Structured {AdEx} Neuron for Accelerated Neuromorphic Cores},
journal = {{IEEE} Transactions on Biomedical Circuits and Systems}
}
@article{Guo2021,
doi = {10.3389/fnins.2021.638474},
url = {https://doi.org/10.3389/fnins.2021.638474},
year = {2021},
month = mar,
publisher = {Frontiers Media {SA}},
volume = {15},
author = {Wenzhe Guo and Mohammed E. Fouda and Ahmed M. Eltawil and Khaled Nabil Salama},
title = {Neural Coding in Spiking Neural Networks: A Comparative Study for Robust Neuromorphic Systems},
journal = {Frontiers in Neuroscience}
}
@article{Lecun1998,
doi = {10.1109/5.726791},
url = {https://doi.org/10.1109/5.726791},
year = {1998},
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {86},
number = {11},
pages = {2278--2324},
author = {Y. Lecun and L. Bottou and Y. Bengio and P. Haffner},
title = {Gradient-based learning applied to document recognition},
journal = {Proceedings of the {IEEE}}
}
@article{Sengupta_2017,
doi = {10.1016/j.ins.2017.04.017},
url = {https://doi.org/10.1016\%2Fj.ins.2017.04.017},
year = 2017,
month = {sep},
publisher = {Elsevier {BV}},
volume = {406-407},
pages = {133--145},
author = {Neelava Sengupta and Nikola Kasabov},
title = {Spike-time encoding as a data compression technique for pattern recognition of temporal data},
journal = {Information Sciences}
}
@article{Fotouhi2001,
doi = {10.1109/4.896241},
url = {https://doi.org/10.1109/4.896241},
year = {2001},
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {36},
number = {1},
pages = {147--151},
author = {B. Fotouhi},
title = {All-{MOS} voltage-to-current converter},
journal = {{IEEE} Journal of Solid-State Circuits}
}
@article{MuChenHuang2009,
doi = {10.1109/tcsii.2009.2019166},
url = {https://doi.org/10.1109/tcsii.2009.2019166},
year = {2009},
month = may,
publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
volume = {56},
number = {5},
pages = {369--373},
author = {Mu-Chen Huang and Shen-luan Liu},
title = {A Fully Differential Comparator-Based Switched-Capacitor Delta-Sigma Modulator},
journal = {{IEEE} Transactions on Circuits and Systems {II}: Express Briefs}
}
@article{Christensen2022,
doi = {10.1088/2634-4386/ac4a83},
url = {https://doi.org/10.1088/2634-4386/ac4a83},
year = {2022},
month = may,
publisher = {{IOP} Publishing},
volume = {2},
number = {2},
pages = {022501},
author = {Dennis V Christensen and Regina Dittmann and Bernabe Linares-Barranco and Abu Sebastian and Manuel Le Gallo and Andrea Redaelli and Stefan Slesazeck and Thomas Mikolajick and Sabina Spiga and Stephan Menzel and Ilia Valov and Gianluca Milano and Carlo Ricciardi and Shi-Jun Liang and Feng Miao and Mario Lanza and Tyler J Quill and Scott T Keene and Alberto Salleo and Julie Grollier and Danijela Markovi{\'{c}} and Alice Mizrahi and Peng Yao and J Joshua Yang and Giacomo Indiveri and John Paul Strachan and Suman Datta and Elisa Vianello and Alexandre Valentian and Johannes Feldmann and Xuan Li and Wolfram H P Pernice and Harish Bhaskaran and Steve Furber and Emre Neftci and Franz Scherr and Wolfgang Maass and Srikanth Ramaswamy and Jonathan Tapson and Priyadarshini Panda and Youngeun Kim and Gouhei Tanaka and Simon Thorpe and Chiara Bartolozzi and Thomas A Cleland and Christoph Posch and ShihChii Liu and Gabriella Panuccio and Mufti Mahmud and Arnab Neelim Mazumder and Morteza Hosseini and Tinoosh Mohsenin and Elisa Donati and Silvia Tolu and Roberto Galeazzi and Martin Ejsing Christensen and Sune Holm and Daniele Ielmini and N Pryds},
title = {2022 roadmap on neuromorphic computing and engineering},
journal = {Neuromorphic Computing and Engineering}
}
@article{Mainen1995,
doi = {10.1016/0896-6273(95)90020-9},
url = {https://doi.org/10.1016/0896-6273(95)90020-9},
year = {1995},
month = dec,
publisher = {Elsevier {BV}},
volume = {15},
number = {6},
pages = {1427--1439},
author = {Zachary F. Mainen and Jasdan Joerges and John R. Huguenard and Terrence J. Sejnowski},
title = {A model of spike initiation in neocortical pyramidal neurons},
journal = {Neuron}
}
@article{Yamazaki2022,
doi = {10.3390/brainsci12070863},
url = {https://doi.org/10.3390/brainsci12070863},
year = {2022},
month = jun,
publisher = {{MDPI} {AG}},
volume = {12},
number = {7},
pages = {863},
author = {Kashu Yamazaki and Viet-Khoa Vo-Ho and Darshan Bulsara and Ngan Le},
title = {Spiking Neural Networks and Their Applications: A Review},
journal = {Brain Sciences}
}
@article{Sengupta2019,
doi = {10.3389/fnins.2019.00095},
url = {https://doi.org/10.3389/fnins.2019.00095},
year = {2019},
month = mar,
publisher = {Frontiers Media {SA}},
volume = {13},
author = {Abhronil Sengupta and Yuting Ye and Robert Wang and Chiao Liu and Kaushik Roy},
title = {Going Deeper in Spiking Neural Networks: {VGG} and Residual Architectures},
journal = {Frontiers in Neuroscience}
}
@article{Wang2021,
doi = {10.3390/electronics10192441},
url = {https://doi.org/10.3390/electronics10192441},
year = {2021},
month = oct,
publisher = {{MDPI} {AG}},
volume = {10},
number = {19},
pages = {2441},
author = {Yihao Wang and Danqing Wu and Yu Wang and Xianwu Hu and Zizhao Ma and Jiayun Feng and Yufeng Xie},
title = {A Low-Cost Hardware-Friendly Spiking Neural Network Based on Binary {MRAM} Synapses, Accelerated Using In-Memory Computing},
journal = {Electronics}
}
@article{Diehl2015,
doi = {10.3389/fncom.2015.00099},
url = {https://doi.org/10.3389/fncom.2015.00099},
year = {2015},
month = aug,
publisher = {Frontiers Media {SA}},
volume = {9},
author = {Peter U. Diehl and Matthew Cook},
title = {Unsupervised learning of digit recognition using spike-timing-dependent plasticity},
journal = {Frontiers in Computational Neuroscience}
}
@inproceedings{Zeng2021,
doi = {10.1145/3477145.3477153},
url = {https://doi.org/10.1145/3477145.3477153},
year = {2021},
month = jul,
publisher = {{ACM}},
author = {Yuan Zeng and Terrence C Stewart and Zubayer Ibne Ferdous and Yevgeny Berdichevsky and Xiaochen Guo},
title = {Temporal Learning with Biologically Fitted {SNN} Models},
booktitle = {International Conference on Neuromorphic Systems 2021}
}
@article{Amari1993,
doi = {10.1016/0925-2312(93)90006-o},
url = {https://doi.org/10.1016/0925-2312(93)90006-o},
year = {1993},
month = jun,
publisher = {Elsevier {BV}},
volume = {5},
number = {4-5},
pages = {185--196},
author = {Shun-ichi Amari},
title = {Backpropagation and stochastic gradient descent method},
journal = {Neurocomputing}
}
@article{Auge2021,
doi = {10.1007/s11063-021-10562-2},
url = {https://doi.org/10.1007/s11063-021-10562-2},
year = {2021},
month = jul,
publisher = {Springer Science and Business Media {LLC}},
volume = {53},
number = {6},
pages = {4693--4710},
author = {Daniel Auge and Julian Hille and Etienne Mueller and Alois Knoll},
title = {A Survey of Encoding Techniques for Signal Processing in Spiking Neural Networks},
journal = {Neural Processing Letters}
}
@article{Zhang2022,
doi = {10.3390/app12115338},
url = {https://doi.org/10.3390/app12115338},
year = {2022},
month = may,
publisher = {{MDPI} {AG}},
volume = {12},
number = {11},
pages = {5338},
author = {Danni Zhang and Zhongwei Tan},
title = {A Review of Optical Neural Networks},
journal = {Applied Sciences}
}
@article{Merolla2014,
doi = {10.1126/science.1254642},
url = {https://doi.org/10.1126/science.1254642},
year = {2014},
month = aug,
publisher = {American Association for the Advancement of Science ({AAAS})},
volume = {345},
number = {6197},
pages = {668--673},
author = {Paul A. Merolla and John V. Arthur and Rodrigo Alvarez-Icaza and Andrew S. Cassidy and Jun Sawada and Filipp Akopyan and Bryan L. Jackson and Nabil Imam and Chen Guo and Yutaka Nakamura and Bernard Brezzo and Ivan Vo and Steven K. Esser and Rathinakumar Appuswamy and Brian Taba and Arnon Amir and Myron D. Flickner and William P. Risk and Rajit Manohar and Dharmendra S. Modha},
title = {A million spiking-neuron integrated circuit with a scalable communication network and interface},
journal = {Science}
}
@article{Ambrogio2018,
doi = {10.1038/s41586-018-0180-5},
url = {https://doi.org/10.1038/s41586-018-0180-5},
year = {2018},
month = jun,
publisher = {Springer Science and Business Media {LLC}},
volume = {558},
number = {7708},
pages = {60--67},
author = {Stefano Ambrogio and Pritish Narayanan and Hsinyu Tsai and Robert M. Shelby and Irem Boybat and Carmelo di Nolfo and Severin Sidler and Massimo Giordano and Martina Bodini and Nathan C. P. Farinha and Benjamin Killeen and Christina Cheng and Yassine Jaoudi and Geoffrey W. Burr},
title = {Equivalent-accuracy accelerated neural-network training using analogue memory},
journal = {Nature}
}
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