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demo/send_packet: env-gated 40 MHz RX + HT STBC/LDPC TX radiotap #105

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Merged
josephnef merged 2 commits into from
Jun 25, 2026
Merged

demo/send_packet: env-gated 40 MHz RX + HT STBC/LDPC TX radiotap #105

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e65f59d
demo: env-gated 40 MHz RX (DEVOURER_BW) + PHY flags on corrupt-any dump
josephnef Jun 25, 2026
4c84908
send_packet: honour STBC + FEC=LDPC on the HT radiotap path
josephnef Jun 25, 2026
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22 changes: 19 additions & 3 deletions demo/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -166,11 +166,13 @@ static void packetProcessor(const Packet &packet) {
static const bool dump_all = std::getenv("DEVOURER_RX_DUMP_ALL") != nullptr;
if (dump_all) {
printf("<devourer-corrupt-any>len=%zu crc_err=%u icv_err=%u "
"rate=%u rssi=%d,%d evm=%d,%d snr=%d,%d\n",
"rate=%u bw=%u stbc=%u ldpc=%u sgi=%u rssi=%d,%d evm=%d,%d snr=%d,%d\n",
packet.Data.size(),
packet.RxAtrib.crc_err ? 1u : 0u,
packet.RxAtrib.icv_err ? 1u : 0u,
packet.RxAtrib.data_rate,
packet.RxAtrib.bw, packet.RxAtrib.stbc,
packet.RxAtrib.ldpc, packet.RxAtrib.sgi,
packet.RxAtrib.rssi[0], packet.RxAtrib.rssi[1],
packet.RxAtrib.evm[0], packet.RxAtrib.evm[1],
packet.RxAtrib.snr[0], packet.RxAtrib.snr[1]);
Expand Down Expand Up @@ -444,10 +446,24 @@ int main() {
channel = std::atoi(ch_env);
logger->info("DEVOURER_CHANNEL set — tuning to channel {}", channel);
}
/* RX bandwidth: 20 MHz by default. DEVOURER_BW=40 selects a 40 MHz monitor
* channel (for receiving HT40 frames); DEVOURER_CHOFFSET picks the secondary
* half (1 = secondary above the primary, 2 = secondary below). */
ChannelWidth_t width = CHANNEL_WIDTH_20;
uint8_t ch_offset = 0;
if (const char *bw_env = std::getenv("DEVOURER_BW")) {
if (std::atoi(bw_env) == 40) {
width = CHANNEL_WIDTH_40;
ch_offset = 1; // default: secondary channel above the primary
if (const char *off_env = std::getenv("DEVOURER_CHOFFSET"))
ch_offset = static_cast<uint8_t>(std::atoi(off_env));
logger->info("DEVOURER_BW=40 — 40 MHz RX, channel-offset {}", ch_offset);
}
}
rtlDevice->Init(packetProcessor, SelectedChannel{
.Channel = static_cast<uint8_t>(channel),
.ChannelOffset = 0,
.ChannelWidth = CHANNEL_WIDTH_20,
.ChannelOffset = ch_offset,
.ChannelWidth = width,
});

rc = libusb_release_interface(dev_handle, 0);
Expand Down
13 changes: 13 additions & 0 deletions src/RtlJaguarDevice.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,19 @@ bool RtlJaguarDevice::send_packet(const uint8_t *packet, size_t length) {
sgi = 0;
}

/* STBC (radiotap MCS known bit5 / flags bits5-6) and FEC=LDPC (known bit4 /
* flags bit4). The HT branch previously read neither, so an HT frame tagged
* STBC/LDPC in radiotap silently transmitted as BCC SISO -- only the VHT
* branch honoured them. Reading them here lets WiFiDriverTxDemo emit a real
* HT STBC / HT LDPC frame (needed as a chip reference for the gr-ieee802-11
* fork's modern-format TX). */
if (mcs_known & 0x20) {
stbc = (mcs_flags >> 5) & 0x3;
}
if ((mcs_known & 0x10) && (mcs_flags & 0x10)) {
ldpc = 1;
}

/* DEVOURER_TX_HT_MCS=1: honour the HT MCS index from radiotap byte 2
* and set fixed_rate accordingly. Without this knob the historic
* behaviour kicks in — fixed_rate stays at the MGN_1M default and the
Expand Down
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