SPEAR+: Streaming-Based Multi-Channel SDR Implementation Using the RFSoC Platform

Welcome to the SPEAR+ repository! This project presents an enhanced software-defined radio (SDR) platform built on the Xilinx RFSoC ZCU216 board, designed for real-time streaming of wideband, multi-channel signals.

SPEAR+ (Streaming-Based Python-Enhanced RFSoC) enables experimental research in wideband MIMO, D-band communications, and high-resolution sensing by providing a flexible, high-performance, and open-source SDR framework.

Overview

SPEAR+ bridges the gap in wideband multi-channel research by providing a real-time streaming architecture that supports:

• High Aggregated Bandwidth: Up to 1.2 GHz real-time bandwidth across multiple channels.
• Scalable MIMO Configurations: Ready-to-use designs for 2T2R, 4T4R, 8T8R, and 16T16R.
• Deterministic Data Transfer: Hardware-assisted streaming DMA using custom FSMs to ensure reliable data movement between DRAM and RF data converters.
• Multi-Tile Synchronization (MTS): Precise timing and phase synchronization across all 16 DACs and 16 ADCs.
• D-band Integration: Proven performance at 135 GHz using the CHARM D-band transceiver modules.
• Pythonic Interface: A high-level software stack based on PYNQ for rapid prototyping and signal processing.

System Architecture

The core of SPEAR+ is a DRAM-centric architecture that decouples timing-critical DMA control from the CPU, offloading it to custom PL-based finite state machines (FSMs).

Key Components:

• Hardware-Assisted Streaming DMA: Built on Xilinx's AXI Data Mover IP, ensuring deterministic, high-speed data transfer (up to 42.6 Gbps) without CPU busy-waiting.
• Multi-Channel Datapath: Optimized AXIS combiner/de-combiner logic to distribute memory bandwidth across multiple RF channels.
• MTS Mechanism: Utilizes the CLK104 daughter board and LMK04828/LMX2594 chips for cross-tile synchronization.

Experimental Setup

The platform has been validated across five major configurations (C1–C5), including wired, sub-6 GHz OTA, and 135 GHz D-band OTA links. For D-band experiments, SPEAR+ is integrated with the Berkeley CHARM modules.

Config	Setup	Bandwidth	Carrier Frequency	Front-End
C1	1T1R	600 MHz	800 MHz	Wired Loopback
C2	1T1R	600 MHz	800 MHz	Sub-6 GHz Antennas
C3	1T1R	600 MHz	135 GHz	CHARM D-band Module
C4	2T2R	600 MHz	800 MHz	Sub-6 GHz Antennas
C5	4T4R	300 MHz	800 MHz	Sub-6 GHz Antennas

Performance Highlights

1. 1T1R Link Performance (Wired, OTA, CHARM)

SPEAR+ supports modulations from QPSK to 256-QAM. At 135 GHz (CHARM), the system meets 3GPP EVM requirements for wideband links, sustaining real-time performance with 600 MHz bandwidth.

2. Multi-Channel MIMO Performance

Real-time 2x2 and 4x4 MIMO streaming is demonstrated with successful EVM and BER measurements across various Modulation and Coding Schemes (MCS).

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Technical Instructions

System Requirements

• Hardware: Xilinx RFSoC ZCU216, CLK104 Clock Board, TI Balun Boards (ADC-LD-BB).
• Software: Vivado 2021.1 (or newer), PYNQ v2.7+ for ZCU216.

Getting Started

1. Clone the Repository:

   git clone https://github.com/functions-lab/SPEAR_plus.git

2. Hardware Generation: Navigate to hw_design/ZCU216/ and use the provided Makefile to generate bitstreams:

   # Generate 4T4R 300MHz bandwidth design
   make bd DESIGN=rfsoc_rfdc_v45_rt_4ch_mts
   make bit DESIGN=rfsoc_rfdc_v45_rt_4ch_mts

3. Running Notebooks: Upload the repository to your RFSoC board and run the provided Jupyter Notebooks for experiments:

   • MILCOM_2025_2ch.ipynb: 2T2R real-time experiments.
   • MILCOM_2025_4ch.ipynb: 4T4R real-time experiments.
   • rfsoc_rfdc_v45_rt_16ch_mts.ipynb: Scalability test for 16-channel MTS.

Repository Structure

• rfsoc_rfdc/: Core Python library for RFSoC control.
• hw_design/: Vivado project scripts and IP cores.
• figures/: Hardware diagrams and experimental results.
• utils/: Benchmarking and plotting utilities.

Citation

If you use SPEAR+ in your research, please cite our MILCOM 2025 paper:

@inproceedings{SPEAR+,
  author    = {Cheng, Wei and Gao, Zhihui and Guajardo, Jose and Beshary, Hesham and Niknejad, Ali and Chen, Tingjun},
  title     = {Streaming-based multi-channel {SDR} implementation using the {RFSoC} platform},
  booktitle = {IEEE MILCOM},
  year      = {2025}
}