T hacks: add ofdm-plot

Used to... surprise... plot OFDM data as output (or input) by gnb! Limitation: only one antenna.
2025-07-11 10:51:59 +02:00
parent 17b5941367
commit a10420e015
2 changed files with 360 additions and 2 deletions
@@ -3,7 +3,7 @@ CFLAGS=-Wall -g -pthread -DT_TRACER -I. -I..

 LIBS=-lX11 -lm -lpng -lXft

-all: dump_nack_signal time_meas timeplot multi-rru-clean ant0
+all: dump_nack_signal time_meas timeplot multi-rru-clean ant0 plot-ofdm

 dump_nack_signal: ../utils.o ../database.o ../configuration.o ../event.o \
                  dump_nack_signal.o
@@ -26,6 +26,13 @@ ant0: ant0.o ../utils.o ../database.o ../configuration.o ../event.o
 ant0.o: ant0.c
 	$(CC) $(CFLAGS) -c -o $@ $< -march=native -ffast-math -O3

+plot-ofdm: plot-ofdm.o ../utils.o
+	$(CC) $(CFLAGS) -o $@ $^ $(LIBS) -lfftw3f
+
+#plot-ofdm needs good compilation
+plot-ofdm.o: plot-ofdm.c
+	$(CC) $(CFLAGS) -c -o $@ $< -march=native -ffast-math -O3
+
 .PHONY: all

 %.o: %.c
@@ -33,4 +40,4 @@ ant0.o: ant0.c

 clean:
 	rm -f *.o core dump_nack_signal time_meas timeplot multi-rru-clean \
-              ant0
+              ant0 plot-ofdm
@@ -0,0 +1,351 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <X11/Xlib.h>
+#include <stdint.h>
+#include <pthread.h>
+#include <complex.h>
+#include <fftw3.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+const int width = 14 * 20 * 4;
+int height;
+
+/* when vzoom = 1 each pixel represents 1 RE
+ * when 2, it is max of 2 vertical REs
+ * useful if height of plot is to big
+ * (with 106 RB we already reach 106*12 = 1272 pixels, so with even bigger
+ * bandwidths...)
+ */
+int vzoom = 1;
+/* when hzoom = 1 each pixel represents 1 RE
+ * when 2, it is max of 2 horizontal REs
+ * useful to slow down display
+ */
+int hzoom = 1;
+/* intensity is to scale the input
+ * normally, as float, cabs(input) is in [0..1]
+ * to get pixel color we *255
+ * but maybe it's too intense, or not enough,
+ * so let's have a control the user can set at will
+ */
+float intensity = 255;
+
+pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
+
+void lock(void)
+{
+  pthread_mutex_lock(&m);
+}
+
+void unlock(void)
+{
+  pthread_mutex_unlock(&m);
+}
+
+typedef struct {
+  Display *d;
+  Window w;
+  XImage *img;
+  unsigned char *img_data;
+  int img_pos;
+} gui_t;
+
+/* delay management begin */
+
+long double frame_time;
+
+void time_start(void)
+{
+  struct timespec l;
+  if (clock_gettime(CLOCK_REALTIME, &l)) abort();
+  frame_time = l.tv_sec * 1000000000. + l.tv_nsec;
+}
+
+void delay(int fps)
+{
+  struct timespec t;
+  struct timespec delay;
+  long double cur_time;
+
+  frame_time += 1000000000. / fps;
+
+  if (clock_gettime(CLOCK_REALTIME, &t)) abort();
+
+  cur_time = t.tv_sec * 1000000000. + t.tv_nsec;
+
+  if (frame_time < cur_time) { fprintf(stderr, "ERROR: we late\n"); return; }
+
+  delay.tv_nsec = ((uint64_t)(frame_time-cur_time)) % 1000000000;
+  delay.tv_sec = ((uint64_t)(frame_time-cur_time)) / 1000000000;
+
+  if (pselect(0, NULL, NULL, NULL, &delay, NULL)) { fprintf(stderr, "ERROR: pselect fails\n"); exit(1); }
+}
+
+/* delay management end */
+
+static void *gui_thread(void *_g)
+{
+  time_start();
+
+  gui_t *g = _g;
+  while (1) {
+    XEvent e; while (XPending(g->d)) XNextEvent(g->d, &e);
+    lock();
+    XPutImage(g->d, g->w, DefaultGC(g->d, DefaultScreen(g->d)), g->img, 0, 0, 0, 0,
+              width, height/vzoom);
+    unlock();
+    delay(10);
+  }
+  return 0;
+}
+
+unsigned char re_to_pixel(float re)
+{
+  float v = fminf(255, re * intensity);
+  return v;
+}
+
+unsigned char mix(unsigned char a, unsigned char b)
+{
+  return a > b ? a : b;
+}
+
+void usage(void)
+{
+  printf("options:\n");
+  printf("    -f                      input is float, not s16\n");
+  printf("    -srate <sampling rate>  set sampling rate (default 61440000)\n");
+  printf("    -prb <prb>              set number of PRBs (default 106)\n");
+  printf("    -mu <mu>                set mu (default 1, 0 is for 15KHz, 1 for 30KHz, etc.)\n");
+  printf("    -no-fft                 don't do fft, input is in frequency domain\n");
+  printf("    -vzoom <zoom>           add some sort of vertical zoom, default 1, passing 2 divides height by 2, etc.\n");
+  printf("    -hzoom <zoom>           add some sort of speed control, default 1, passing 2 means 2 REs per pixel, etc.\n");
+  printf("    -delay <delay>          delay 'delay' microseconds between processing of each symbol\n");
+  printf("    -intensity <intensity>  set intensity of data pixel (default 255.)\n");
+  printf("    -skip <count>           skip 'count' samples at beginning\n");
+  exit(0);
+}
+
+int main(int n, char **v)
+{
+  int input_is_float = 0;
+  int no_fft = 0;
+  int delay = 0;
+  int skip = 0;
+  int symbols_per_subframe;
+  long sampling_rate = 61440000;
+  int mu = 1;
+  int prb = 106;
+
+  /* parse command line arguments */
+  for (int i = 1; i < n; i++) {
+    if (!strcmp(v[i], "-f")) { input_is_float = 1; continue; }
+    if (!strcmp(v[i], "-no-fft")) { no_fft = 1; continue; }
+    if (!strcmp(v[i], "-vzoom")) { if (i>n-2) usage(); vzoom = atoi(v[++i]); continue; }
+    if (!strcmp(v[i], "-hzoom")) { if (i>n-2) usage(); hzoom = atoi(v[++i]); continue; }
+    if (!strcmp(v[i], "-delay")) { if (i>n-2) usage(); delay = atoi(v[++i]); continue; }
+    if (!strcmp(v[i], "-intensity")) { if (i>n-2) usage(); intensity = atof(v[++i]); continue; }
+    if (!strcmp(v[i], "-srate")) { if (i>n-2) usage(); sampling_rate = atol(v[++i]); continue; }
+    if (!strcmp(v[i], "-prb")) { if (i>n-2) usage(); prb = atoi(v[++i]); continue; }
+    if (!strcmp(v[i], "-mu")) { if (i>n-2) usage(); mu = atoi(v[++i]); continue; }
+    if (!strcmp(v[i], "-skip")) { if (i>n-2) usage(); skip = atoi(v[++i]); continue; }
+    usage();
+  }
+
+  symbols_per_subframe = 14 * (1 << mu);
+
+  /* compute durations from sampling rate and mu (scs) */
+  /* this is 38.211 5.3.1, a bit simplified/reordered */
+  int ofdm_duration = sampling_rate / 15000 / (1 << mu);
+  int l0_cycle_prefix = sampling_rate / 480000 * (144*64 / (1 << mu) + 16*64) / 4096;
+  int cycle_prefix = sampling_rate / 480000 * (144*64 / (1 << mu)) / 4096;
+
+  /* small sanity check */
+  if (prb * 12 > ofdm_duration) {
+    printf("fatal: too many PRBs for this sampling rate / mu\n");
+    exit(1);
+  }
+
+  height = prb * 12;
+
+  if (height % vzoom) { fprintf(stderr, "bad vzoom for this height, try 1, 2, 4, ...\n"); return 1; }
+
+  gui_t g = { 0 };
+
+  /* open X11 display */
+  g.d = XOpenDisplay(0);
+  if (!g.d) {
+    fprintf(stderr, "could not open display\n");
+    return 1;
+  }
+
+  /* create window */
+  g.w = XCreateSimpleWindow(g.d, DefaultRootWindow(g.d), 0, 0,
+                            width, height / vzoom, 0, WhitePixel(g.d, DefaultScreen(g.d)),
+                            WhitePixel(g.d, DefaultScreen(g.d)));
+  XStoreName(g.d, g.w, "IQ");
+  /* enable backing store */
+  {
+    XSetWindowAttributes att;
+    att.backing_store = Always;
+    XChangeWindowAttributes(g.d, g.w, CWBackingStore, &att);
+  }
+  XSelectInput(g.d, g.w,
+               KeyPressMask      |
+               ButtonPressMask   |
+               ButtonReleaseMask |
+               PointerMotionMask |
+               ExposureMask      |
+               StructureNotifyMask);
+  XMapWindow(g.d, g.w);
+
+  g.img_data = calloc(1, width * height/vzoom * 4); if (!g.img_data) abort();
+  g.img = XCreateImage(g.d, DefaultVisual(g.d, DefaultScreen(g.d)), 24 /*depth*/,
+                   ZPixmap, 0 /*offset*/, (char*)g.img_data, width, height/vzoom, 8, 0);
+
+  new_thread(gui_thread, &g);
+
+  /* fft data */
+  int fft_size = ofdm_duration;
+  float complex *in = fftwf_malloc(sizeof(float complex) * fft_size);
+  float complex *out = fftwf_malloc(sizeof(float complex) * fft_size);
+  fftwf_plan p_fft = fftwf_plan_dft_1d(fft_size, in, out,
+                                       FFTW_FORWARD, FFTW_ESTIMATE);
+  memset(in, 0, sizeof(float complex) * fft_size);
+  fftwf_execute(p_fft);
+
+  int symbol = 0;
+  int back_color = 0;
+  int hpixel = 0;
+
+  if (skip) {
+    if (input_is_float) {
+      float intime[skip * 2];
+      if (fread(intime, skip * 8, 1, stdin) != 1) abort();
+    } else {
+      short intime[skip * 2];
+      if (fread(intime, skip * 4, 1, stdin) != 1) abort();
+    }
+  }
+
+  while (1) {
+    int cur_cycle_prefix;
+    if (symbol == 0 || symbol == 7 * (1 << mu))
+      cur_cycle_prefix = l0_cycle_prefix;
+    else
+      cur_cycle_prefix = cycle_prefix;
+
+    if (no_fft) goto without_fft;
+
+    /* input signal is in time domain, timing aligned, do FFT */
+
+    /* read time domain data */
+    if (input_is_float) {
+      float intime[(ofdm_duration + cur_cycle_prefix) * 2];
+      if (fread(intime, (ofdm_duration + cur_cycle_prefix) * 8, 1, stdin) != 1) break;
+
+      for (int i = 0; i < fft_size; i++)
+        /* skip cycle prefix */
+        in[i] = intime[(cur_cycle_prefix + i) * 2] + I * intime[(cur_cycle_prefix + i) * 2 + 1];
+    } else {
+      short intime[(ofdm_duration + cur_cycle_prefix) * 2];
+      if (fread(intime, (ofdm_duration + cur_cycle_prefix) * 4, 1, stdin) != 1) break;
+
+      for (int i = 0; i < fft_size; i++)
+        /* skip cycle prefix */
+        in[i] = intime[(cur_cycle_prefix + i) * 2] / 2048. + I * intime[(cur_cycle_prefix + i) * 2 + 1] / 2048.;
+    }
+
+    /* go to freq domain */
+    fftwf_execute(p_fft);
+
+    goto after_fft;
+
+without_fft:
+    /* input data is symbols, each containing full FFT data */
+    if (input_is_float) {
+      float infreq[fft_size * 2];
+      if (fread(infreq, fft_size * 2 * 4, 1, stdin) != 1) break;
+
+      for (int i = 0; i < fft_size; i++)
+        out[i] = infreq[i * 2] + I * infreq[i * 2 + 1];
+    } else {
+      short infreq[ofdm_duration * 2];
+      if (fread(infreq, fft_size * 2 * 2, 1, stdin) != 1) break;
+
+      for (int i = 0; i < fft_size; i++)
+        out[i] = infreq[i * 2] / 2048. + I * infreq[i * 2 + 1] / 2048.;
+    }
+
+after_fft:
+    lock();
+
+    /* extract data of this ofdm symbol */
+    unsigned char *p = g.img_data + g.img_pos * 4;
+    int front_pos = (g.img_pos + 8) % width;
+    unsigned char *pfront = g.img_data + front_pos * 4;
+    for (int i = prb * 12 - 1; i >= 0; i -= vzoom) {
+      /* take the max */
+      float out_val = 0;
+      for (int j = 0; j < vzoom; j++) {
+        int start = - prb * 12 / 2;
+        int pos = start + i + j;
+        /* neg freq are at the end of fft data array */
+        int pos_in_fft = pos >= 0
+                         ? pos
+                         : pos + fft_size;
+        float v = cabs(out[pos_in_fft]);
+        if (v > out_val) out_val = v;
+      }
+      int color = re_to_pixel(out_val);
+      /* grey level image mixed with some background changing every slot */
+      unsigned char back_col[2][3] = {
+        { 100, 90, 90 },
+        { 100, 60, 60, }
+      };
+      if (hpixel == 0) {
+        p[0] = p[1] = p[2] = color;
+      } else {
+        p[0] = mix(p[0], color);
+        p[1] = mix(p[1], color);
+        p[2] = mix(p[2], color);
+      }
+      if (hpixel == hzoom - 1) {
+        p[0] = mix(p[0], back_col[back_color][0]);
+        p[1] = mix(p[1], back_col[back_color][1]);
+        p[2] = mix(p[2], back_col[back_color][2]);
+      }
+      p[3] = 255;
+      p += width * 4;
+      pfront[0] = 255;
+      pfront[1] = 128;
+      pfront[2] = 128;
+      pfront[3] = 255;
+      pfront += width * 4;
+    }
+
+    unlock();
+
+    hpixel++;
+    if (hpixel == hzoom) {
+      hpixel = 0;
+      g.img_pos++;
+      if (g.img_pos == width) g.img_pos = 0;
+    }
+
+    symbol++;
+    if (symbol == symbols_per_subframe) symbol = 0;
+
+    /* switch back color every slot */
+    if (symbol % 14 == 0)
+      back_color = 1 - back_color;
+
+    if (delay) usleep(delay);
+  }
+
+  return 0;
+}