ICE: a scalable, low-cost FPGA-based telescope signal processing and networking system

TL;DR

The ICE system provides a scalable, cost-effective FPGA-based hardware and software framework for high-bandwidth telescope signal processing, supporting advanced digital processing needs in modern radio and millimeter/sub-millimeter telescopes.

Contribution

This paper introduces the ICE hardware and software framework, enabling economical, scalable, and flexible FPGA-based data acquisition and processing for large telescope arrays with high data rates.

Findings

Supports data rates exceeding one terabyte per second.

Successfully implemented in SPT, Simons Array, CHIME, and HIRAX telescopes.

Provides a low-cost, high-bandwidth interconnection network for telescope arrays.

Abstract

We present an overview of the 'ICE' hardware and software framework that implements large arrays of interconnected FPGA-based data acquisition, signal processing and networking nodes economically. The system was conceived for application to radio, millimeter and sub-millimeter telescope readout systems that have requirements beyond typical off-the-shelf processing systems, such as careful control of interference signals produced by the digital electronics, and clocking of all elements in the system from a single precise observatory-derived oscillator. A new generation of telescopes operating at these frequency bands and designed with a vastly increased emphasis on digital signal processing to support their detector multiplexing technology or high-bandwidth correlators---data rates exceeding a terabyte per second---are becoming common. The ICE system is built around a custom FPGA motherboard that makes use of an Xilinx Kintex-7 FPGA and ARM-based co-processor. The system is specialized for specific applications through software, firmware, and custom mezzanine daughter boards that interface to the FPGA through the industry-standard FMC specifications. For high density applications, the motherboards are packaged in 16-slot crates with ICE backplanes that implement a low-cost passive full-mesh network between the motherboards in a crate, allow high bandwidth interconnection between crates, and enable data offload to a computer cluster. A Python-based control software library automatically detects and operates the hardware in the array. Examples of specific telescope applications of the ICE framework are presented, namely the frequency-multiplexed bolometer readout systems used for the SPT and Simons Array and the digitizer, F-engine, and networking engine for the CHIME and HIRAX radio interferometers.