Capacity, Fidelity, and Noise Tolerance of Associative Spatial-Temporal Memories Based on Memristive Neuromorphic Network

TL;DR

This paper analyzes the capacity, fidelity, and noise tolerance of associative spatial-temporal memories built with neuromorphic networks called CrossNets, highlighting promising recording methods and their hardware implementation potential.

Contribution

It introduces two effective information recording methods for CrossNets, comparing their performance and hardware feasibility, and demonstrates their superior capacity over traditional ternary memories.

Findings

Both methods outperform Ternary Content-Addressable Memories in capacity.

The quadratic programming method offers higher capacity than the gradient descent approach.

Local recording method enables easier hardware implementation in nanoelectronic circuits.

Abstract

We have calculated the key characteristics of associative (content-addressable) spatial-temporal memories based on neuromorphic networks with restricted connectivity - "CrossNets". Such networks may be naturally implemented in nanoelectronic hardware using hybrid CMOS/memristor circuits, which may feature extremely high energy efficiency, approaching that of biological cortical circuits, at much higher operation speed. Our numerical simulations, in some cases confirmed by analytical calculations, have shown that the characteristics depend substantially on the method of information recording into the memory. Of the four methods we have explored, two look especially promising - one based on the quadratic programming, and the other one being a specific discrete version of the gradient descent. The latter method provides a slightly lower memory capacity (at the same fidelity) then the former one, but it allows local recording, which may be more readily implemented in nanoelectronic hardware. Most importantly, at the synchronous retrieval, both methods provide a capacity higher than that of the well-known Ternary Content-Addressable Memories with the same number of nonvolatile memory cells (e.g., memristors), though the input noise immunity of the CrossNet memories is somewhat lower.