An FPGA-based lossless data-compression scheme for high-energy underwater neutrino telescope (HUNT)
摘要
The high-energy underwater neutrino telescope, proposed by the Institute of High Energy Physics of the Chinese Academy of Sciences, aims to detect ultra-high-energy neutrinos exceeding 100 TeV by deploying a 30 km3 detector array in a deep-sea environment. The use of 20-inch photomultiplier tubes (PMTs) in this massive array necessitates the frontend readout electronics system capable of performing real-time processing and long-distance transmission.
PurposeWith a sampling rate of 1 Gsps and an average background counting rate per PMT channel of 60 kHz, the frontend readout electronics system generates a raw data bandwidth of approximately 2.9 Gbps per board. To alleviate the long-distance transmission burden of waveform data selected by the global trigger based on arrival time (T) and charge (Q) information, and to conserve on-board storage resources, this paper presents an efficient lossless data-compression architecture implemented within the frontend FPGA.
MethodsThis paper proposes an FPGA-based heterogeneous lossless compression architecture. For trigger data streams with stringent real-time requirements, a dynamic coarse–fine timestamp remapping strategy is developed for arrival time (T), coupled with a physical threshold-based range saturation strategy for charge (Q). For waveform data (W) intended for offline analysis, a hybrid compression strategy integrating Bitshuffle preprocessing with Zstd customized using pretrained static FSE tables is designed to exploit baseline-dominated waveforms containing sparse pulses.
ResultsThe dynamic remapping algorithm for timing information achieves a 3.24× compression ratio under an 18-bit fine timestamp configuration. Simultaneously, the range saturation strategy for charge information attains a 1.5× compression ratio without compromising the integrity of the trigger logic. For waveform data, the hardware-accelerated algorithm implemented on the Xilinx Kintex-7 FPGA realizes a 2.99× compression ratio and a throughput of 1 GB/s at a 250 MHz clock frequency, ensuring lossless reconstruction. Ultimately, the proposed scheme reduces the data bandwidth requirement to within the capacity of the existing transmission links.