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The Only Open-Source WiFi Stack That Can Send ACKs on Time

“The Viterbi decoder in your WiFi chip responds in 10 millionths of a second — and this is the only open-source hardware that actually does that, not just simulates it.”

The Only Open-Source WiFi Stack That Can Send ACKs on Time
Source · github.com

“"Individuals, SMEs, opensource communities and big companies have shown big interests on the openwifi project." — openwifi project team, quoted via rtl-sdr.com coverage”

You know that feeling when you are researching WiFi security or protocol timing and you hit a wall because the chip firmware is closed and the driver is a black box? Every open-source WiFi implementation built on GNU Radio hits the same hard architectural limit: the 10µs ACK window required by IEEE 802.11 is physically impossible to meet when your timing goes through an Ethernet cable and a CPU. The gr-ieee802-11 README explicitly states 'RTS/CTS and CSMA/CA are not currently implemented' as a direct consequence of this. You end up with a monitoring and injection tool, not a real two-way WiFi stack. openwifi solves this by enforcing MAC timing in FPGA fabric, where clock cycles are deterministic.

fpgawifisdr802.11linuxopen-sourcewireless-security

openwifi runs on a Xilinx Zynq SoC — a chip that pairs an ARM Cortex-A9 CPU with a programmable FPGA on the same die. The FPGA handles the time-critical parts: OFDM modulation and demodulation, CSMA/CA backoff timers, and ACK responses at exactly 10µs — all enforced in hardware. The AD9361 RF transceiver handles the actual radio signal from 70 MHz to 6 GHz. The ARM CPU runs embedded Linux with a mac80211 kernel driver, which registers openwifi as a standard wireless network interface. Your OS sees it as a normal WiFi card, so hostapd, wpa_supplicant, iw, and tcpdump all work unmodified. The split between FPGA (timing and radio) and CPU (protocol management and applications) lets you patch the FPGA Verilog to change MAC behavior, then flash the bitstream without touching Linux userspace.

01
Hardware-enforced 10µs SIFS timing — you get real CSMA/CA, which means two-way ACK exchange works correctly. GNU Radio alternatives explicitly document this as architecturally impossible on CPU and Ethernet paths.
02
Linux mac80211 compatibility — openwifi registers as a standard WiFi NIC, so hostapd, wpa_supplicant, iw, iwconfig, and tcpdump all work without modification.
03
CSI extraction and fuzzing — you read Channel State Information per packet and inject artificial channel responses, enabling sensing research (radar, localization, breathing detection) alongside normal communication.
04
Configurable MAC parameters at runtime — SIFS, DIFS, CW min/max, slot time, RTS/CTS duration, and per-MAC-address time-gated TX queues are all adjustable via the sdrctl tool without an FPGA rebuild.
05
Packet injection and protocol fuzzing — you inject arbitrary 802.11 frames to test edge cases; the repo is documented as compatible with fragattacks and krackattacks security research toolchains.
06
12 supported board configurations — ranging from entry-level Zynq 7020 boards ($200–$300, no paid Vivado license needed) to high-end ZCU102 hardware for demanding PHY experiments.
Who it’s for

This is for wireless protocol researchers, PhD students, and security engineers who need to modify or observe IEEE 802.11 below the driver level — protocol timing experiments, CSI-based sensing, custom MAC schedulers, or hands-on WiFi security testing with real hardware timing. If you are building applications on top of WiFi or need a production access point, this gives you nothing useful. Not practical if you need 802.11ac/ax throughput or multi-stream MIMO — those are gated behind the commercial subscription at openwifi.tech.

Worth exploring

Worth exploring if you do academic or industrial wireless protocol research and need a standards-compliant, modifiable MAC/PHY. The 40+ peer-reviewed publications confirm it works for research purposes. Not ready for any sustained deployment: the Xilinx evaluation Viterbi decoder halts after approximately 2 hours (documented in the README Quick Start), and no commercial production deployments have been confirmed.

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