{"id":4313,"date":"2025-10-29T01:52:24","date_gmt":"2025-10-29T01:52:24","guid":{"rendered":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/?p=4313"},"modified":"2025-10-29T01:53:46","modified_gmt":"2025-10-29T01:53:46","slug":"cognitive-radio-applications-of-rapid-rf-triage-fft-only-wins-at-the-edge","status":"publish","type":"post","link":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/?p=4313","title":{"rendered":"Cognitive Radio Applications of Rapid RF Triage: FFT-Only Wins at the Edge"},"content":{"rendered":"\n<h3 class=\"wp-block-heading\"><em>How a 1.5 ms FFT + Hybrid Gate Enables Real-Time Dynamic Spectrum Access<\/em><\/h3>\n\n\n\n<p><strong>By Benjamin J. Gilbert<\/strong><br><em>Spectrcyde RF Quantum SCYTHE<\/em><br><a href=\"mailto:bgilbert2@com.edu\">bgilbert2@com.edu<\/a><br><a href=\"https:\/\/gilbert1984.com\/papers\/rf-triage-rev2.pdf\">Full Paper PDF<\/a> \u00b7 <a href=\"https:\/\/github.com\/bgilbert1984\/rf-triage-benchmark\">Reproducible Code<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Cognitive Radio in 2025: The Core Loop<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>graph TD\n    A&#91;RF Environment] --&gt; B&#91;Sense Spectrum]\n    B --&gt; C{Triage: Digital or Analog?}\n    C --&gt;|Analog (FM, AM)| D&#91;Vacate Band]\n    C --&gt;|Digital (BPSK, QPSK...)| E&#91;Share \/ Opportunistic TX]\n    E --&gt; F&#91;Transmit]\n    F --&gt; A<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Triage must be &lt;10 ms, &lt;1M FLOPs, &gt;0.7 AUROC at 0 dB SNR.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Application 1: <strong>CBRS-Style Dynamic Spectrum Access (DSA)<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Band<\/th><th>Primary User<\/th><th>Secondary User<\/th><\/tr><\/thead><tbody><tr><td>3.55\u20133.7 GHz<\/td><td>DoD Radar<\/td><td>LTE\/5G-NR (CBRS)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Triage Role<\/strong>:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Detect radar (analog)<\/strong> \u2192 <strong>evacuate in &lt;60 s<\/strong> (FCC rule)<\/li>\n\n\n\n<li><strong>Detect LTE\/5G (digital)<\/strong> \u2192 <strong>coexist<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Why FFT Wins<\/strong>:<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Metric<\/th><th>FFT+Filter<\/th><th>Tiny CNN<\/th><\/tr><\/thead><tbody><tr><td>p99 Latency @ 0 dB<\/td><td><strong>1.5 ms<\/strong><\/td><td>6.0 ms<\/td><\/tr><tr><td>Compute<\/td><td><strong>0.25M FLOPs<\/strong><\/td><td>12M<\/td><\/tr><tr><td>AUROC<\/td><td><strong>0.754<\/strong><\/td><td>0.671<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>FFT meets 60 s evacuation with 40\u00d7 margin.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Application 2: <strong>6G Unlicensed Shared Spectrum<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Sub-7 GHz + mmWave<\/strong><\/li>\n\n\n\n<li><strong>AI-Native Air Interface<\/strong><\/li>\n\n\n\n<li><strong>Zero-touch spectrum arbitration<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Hybrid Gate in Action<\/strong>:<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>def triage(iq):\n    fft_mag = normalize(fft(iq, n=1024))\n    conf, label = light_filters(fft_mag)  # 1.5 ms\n\n    if conf &gt; 0.9:\n        return label                       # Fast path\n    else:\n        return cnn(fft_mag)               # Slow path (rare)<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Gate Rate<\/th><th>Avg Compute<\/th><th>p99 Latency<\/th><th>Use Case<\/th><\/tr><\/thead><tbody><tr><td><strong>5%<\/strong><\/td><td><strong>0.8M FLOPs<\/strong><\/td><td><strong>1.5 ms<\/strong><\/td><td><strong>6G Edge Node<\/strong><\/td><\/tr><tr><td>20%<\/td><td>2.6M FLOPs<\/td><td>1.5 ms<\/td><td><strong>Dense Urban<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>5% gate rate = 15\u00d7 savings vs pure CNN, same tail latency.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Application 3: <strong>Anti-Jamming in Contested Environments<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Jammer Type<\/th><th>Spectral Signature<\/th><\/tr><\/thead><tbody><tr><td><strong>FM Sweep<\/strong><\/td><td>Smooth, wideband<\/td><\/tr><tr><td><strong>BPSK Pulse<\/strong><\/td><td>Sharp tones<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Triage \u2192 Countermeasure<\/strong>:<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Detected<\/th><th>Action<\/th><\/tr><\/thead><tbody><tr><td><strong>Analog (FM)<\/strong><\/td><td>Frequency hop away<\/td><\/tr><tr><td><strong>Digital (BPSK)<\/strong><\/td><td>Null the beam<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>FFT peak spacing detects symbol rate in &lt;2 ms.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Application 4: <strong>Federated Spectrum Sensing Networks<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>1000s of IoT sensors<\/strong><\/li>\n\n\n\n<li><strong>Each runs FFT triage locally<\/strong><\/li>\n\n\n\n<li><strong>Only ambiguous samples \u2192 cloud CNN<\/strong><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>graph LR\n    S1&#91;Sensor 1] --&gt;|FFT: 0.95 conf| Local Decision\n    S2&#91;Sensor 2] --&gt;|FFT: 0.70 conf| Cloud CNN\n    Cloud --&gt; Fusion&#91;Global Map]<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>&gt;95% decisions stay on-device \u2192 near-zero backhaul.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Real-World Integration: <strong>USRP + GNU Radio Block<\/strong><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ gr-fft_triage.cc\nclass fft_triage : public gr::sync_block {\n    float compute_confidence(float* mag) {\n        float energy = band_energy(mag);\n        float spacing = peak_spacing(mag);\n        return sigmoid(energy * spacing);  \/\/ &lt;1 ms\n    }\n};<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Input<\/strong>: 1024 IQ samples<\/li>\n\n\n\n<li><strong>Output<\/strong>: <code>0<\/code> (analog) or <code>1<\/code> (digital) + confidence<\/li>\n\n\n\n<li><strong>Latency<\/strong>: <strong>1.5 ms on E312<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Performance in Cognitive Radio Scenarios<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Scenario<\/th><th>Required p99<\/th><th>FFT+Filter<\/th><th>Hybrid (f=0.1)<\/th><th>Pure CNN<\/th><\/tr><\/thead><tbody><tr><td><strong>CBRS SAS<\/strong><\/td><td>&lt;50 ms<\/td><td>Pass<\/td><td>Pass<\/td><td>Pass<\/td><\/tr><tr><td><strong>6G Zero-Touch<\/strong><\/td><td>&lt;5 ms<\/td><td><strong>Pass<\/strong><\/td><td><strong>Pass<\/strong><\/td><td>Fail<\/td><\/tr><tr><td><strong>EW Triage<\/strong><\/td><td>&lt;2 ms<\/td><td><strong>Pass<\/strong><\/td><td><strong>Pass<\/strong><\/td><td>Fail<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Only FFT-based methods meet sub-5 ms budgets.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Open Challenge to the Community<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Can you beat 0.754 AUROC with &lt;1M FLOPs at 0 dB SNR?<\/strong><\/p>\n<\/blockquote>\n\n\n\n<pre class=\"wp-block-code\"><code>git clone https:\/\/github.com\/bgilbert1984\/rf-triage-benchmark\nmake challenge<\/code><\/pre>\n\n\n\n<p>Submit your model \u2192 leaderboard.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">TL;DR: Cognitive Radio Stack in 2025<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Layer<\/th><th>Technique<\/th><th>Latency<\/th><th>Compute<\/th><\/tr><\/thead><tbody><tr><td><strong>L0<\/strong><\/td><td>Energy Detection<\/td><td>0.1 ms<\/td><td>10k FLOPs<\/td><\/tr><tr><td><strong>L1<\/strong><\/td><td><strong>FFT + Light Filters<\/strong><\/td><td><strong>1.5 ms<\/strong><\/td><td><strong>0.25M FLOPs<\/strong><\/td><\/tr><tr><td><strong>L2<\/strong><\/td><td>Hybrid Gate \u2192 Tiny CNN<\/td><td>1.5 ms (p99)<\/td><td><strong>0.8M FLOPs (f=0.1)<\/strong><\/td><\/tr><tr><td><strong>L3<\/strong><\/td><td>Full DL<\/td><td>Offline<\/td><td>Cloud<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>FFT is the new cognitive radio baseline.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><strong>Read the paper<\/strong>: <a href=\"https:\/\/gilbert1984.com\/papers\/rf-triage-rev2.pdf\">FFT-Only vs Learned Spectral Proxies (PDF)<\/a><br><strong>Run the code<\/strong>: <a href=\"https:\/\/github.com\/bgilbert1984\/rf-triage-benchmark\">github.com\/bgilbert1984\/rf-triage-benchmark<\/a><br><strong>Cite<\/strong>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>@article{gilbert2025fft,\n  title={FFT-Only vs Learned Spectral Proxies for Rapid RF Triage},\n  author={Gilbert, Benjamin J.},\n  journal={arXiv preprint},\n  year={2025}\n}<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><em>Published October 29, 2025<\/em><br><em><a href=\"https:\/\/grok.com\/share\/bGVnYWN5LWNvcHk%3D_bce46726-d28f-4e94-9a28-e37699a5fb9e\">Share if you&#8217;re building the next-generation cognitive radio.<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>How a 1.5 ms FFT + Hybrid Gate Enables Real-Time Dynamic Spectrum Access By Benjamin J. GilbertSpectrcyde RF Quantum SCYTHEbgilbert2@com.eduFull Paper PDF \u00b7 Reproducible Code Cognitive Radio in 2025: The Core Loop Triage must be &lt;10 ms, &lt;1M FLOPs, &gt;0.7 AUROC at 0 dB SNR. Application 1: CBRS-Style Dynamic Spectrum Access (DSA) Band Primary User&hellip;&nbsp;<a href=\"https:\/\/172-234-197-23.ip.linodeusercontent.com\/?p=4313\" rel=\"bookmark\"><span class=\"screen-reader-text\">Cognitive Radio Applications of Rapid RF Triage: FFT-Only Wins at the Edge<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":4316,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"","neve_meta_content_width":0,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","footnotes":""},"categories":[6,10],"tags":[],"class_list":["post-4313","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-signal-science","category-signal_scythe"],"_links":{"self":[{"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/posts\/4313","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4313"}],"version-history":[{"count":1,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/posts\/4313\/revisions"}],"predecessor-version":[{"id":4315,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/posts\/4313\/revisions\/4315"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=\/wp\/v2\/media\/4316"}],"wp:attachment":[{"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4313"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4313"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/172-234-197-23.ip.linodeusercontent.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}