Trying to debug issues with carrier estimation

channel.py

@@ -4,13 +4,13 @@ import scipy.interpolate
 import matplotlib.pyplot as plt
 
 # Dirac delta function response, no change
-#channel_response = np.array([0, 0, 0, 1, 0, 0, 0])
-channel_response = np.array([-1 + 1j, 0, 1, 0.5, 0.25])
+channel_response = np.array([0, 0, 0, 1, 0, 0, 0])
+#channel_response = np.array([-1 + 1j, 0, 1, 0.5, 0.25])
 
 
 # How do I sync this across two files?
 # figure it out later
-pilot_value = 1 + 1j
+pilot_value = 5 + 5j
 
 # 15dB seems to be around the minimum for error-free transmission
 snr_db = 300
@@ -65,6 +65,8 @@ def estimate(in_data, pilots=0):
     every time. This also has the advantage of being able to synchronise the symbols. Since I
     will be implementing some sort of protocol anyways, I think this will be a good idea. As well,
     we move slow enough that the channel will not likely change significantly over a single packet.
+
+    Actually maybe not? Looked at a paper, check the drive.
     """
 
     all_carriers = np.arange(len(in_data[0]))
@@ -73,24 +75,50 @@ def estimate(in_data, pilots=0):
         pilot_carriers = all_carriers[::(len(all_carriers)) // pilots]
         pilot_carriers = np.delete(pilot_carriers, 0)
 
+        print(pilot_carriers)
+
         # start averaging
         H_est = 0
 
-        for i in range(len(in_data)):
-            # Obtain channel response at pilot carriers
-            H_est_pilots = in_data[i][pilot_carriers] / pilot_value
+        # for i in range(len(in_data)):
+        #     # Obtain channel response at pilot carriers
+        #     H_est_pilots = in_data[i][pilot_carriers] / pilot_value
 
-            # Interpolate estimates based on what we get from the few pilot values
-            H_est_abs = scipy.interpolate.interp1d(pilot_carriers, abs(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
-            H_est_phase = scipy.interpolate.interp1d(pilot_carriers, np.angle(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
 
-            # Take angular form and turn into rectangular form
-            H_est += H_est_abs * np.exp(1j*H_est_phase)
+        #     # Interpolate estimates based on what we get from the few pilot values
+        #     H_est_abs = scipy.interpolate.interp1d(pilot_carriers, abs(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
+        #     H_est_phase = scipy.interpolate.interp1d(pilot_carriers, np.angle(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
 
-        H_est = H_est / len(in_data)
+        #     # Take angular form and turn into rectangular form
+        #     H_est += H_est_abs * np.exp(1j*H_est_phase)
+
+        H_est_pilots = np.ndarray((len(pilot_carriers)), dtype=np.csingle)
+
+        j = 0
+        # Obtain channel response at pilot carriers
+        for i in pilot_carriers:
+            H_est_pilots[j] = in_data[0][i] / pilot_value
+            j += 1
+
+
+        # Interpolate estimates based on what we get from the few pilot values
+        H_est_abs = scipy.interpolate.interp1d(pilot_carriers, abs(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
+        H_est_phase = scipy.interpolate.interp1d(pilot_carriers, np.angle(H_est_pilots), kind='linear', fill_value='extrapolate')(all_carriers)
+
+        # Take angular form and turn into rectangular form
+        H_est += H_est_abs * np.exp(1j*H_est_phase)
+
+        # for an average channel estimate
+        # H_est = H_est / len(in_data)
 
         # Exact channel response
         H_exact = np.fft.fft(channel_response, len(in_data[0]))
+
+        for i in range(3):
+            plt.plot(abs(in_data[i]), "b")
+            plt.plot(np.abs(in_data[i]), "r")
+            plt.show(block=True)
+
         plt.plot(all_carriers, np.real(H_exact), "b")
         plt.plot(all_carriers, np.real(H_est), "r")
         plt.plot(pilot_carriers, np.real(H_est_pilots), "go")
@@ -101,6 +129,9 @@ def estimate(in_data, pilots=0):
         plt.plot(pilot_carriers, np.imag(H_est_pilots), "go")
         plt.show(block=True)
 
+        print(H_est_pilots)
+        print(H_exact[pilot_carriers])
+
         return H_est
 
 

main.py

@@ -20,7 +20,6 @@ Right now though it's just proof of concept to see if I can get a reliable signa
 
 import numpy as np
 import matplotlib.pyplot as plt
-plt.ion()
 
 import channel
 import qam
@@ -69,7 +68,7 @@ if __name__ == '__main__':
     parallel = parallelise(64, bytes)
 
     # modulate data with a QAM scheme
-    modulated = qam.modulate(parallel, pilots=20)
+    modulated = qam.modulate(parallel, pilots=10)
 
     # Run IFFT to get a time-domain signal to send
     ofdm_time = np.fft.ifft(modulated)
@@ -87,13 +86,13 @@ if __name__ == '__main__':
     to_equalize = np.fft.fft(ofdm_cp_removed)
 
     # Find an estimate for channel effect
-    H_est = channel.estimate(to_equalize, pilots=20)
+    H_est = channel.estimate(to_equalize, pilots=10)
 
     # Equalise based on estimated channel
     to_decode = channel.equalize(to_equalize, H_est)
 
     # Demodulate symbol into output data
-    to_serialise = qam.demodulate(to_decode, pilots=20)
+    to_serialise = qam.demodulate(to_decode, pilots=10)
 
     # Turn data back into string
     data = serialise(64, to_serialise)

modem.py

@@ -0,0 +1,9 @@
+"""
+The modem for communications.
+
+I need to define my protocol here first.
+
+Packet:
+
+Prefix
+"""

qam.py

@@ -1,7 +1,7 @@
 import numpy as np
 from scipy.spatial.distance import euclidean
 
-pilot_value = 1 + 1j
+pilot_value = 5 + 5j
 
 qam_mapping_table = {
     0 : 1 + 1j,
@@ -36,6 +36,7 @@ def modulate(in_data, pilots=0):
         pilot_carriers = all_carriers[::(num_data_carriers + pilots)//pilots]
         pilot_carriers = np.delete(pilot_carriers, 0) # not sure how to not have this line
         data_carriers = np.delete(all_carriers, pilot_carriers)
+        print(pilot_carriers)
     else:
         data_carriers = all_carriers
 

serpar.py

@@ -67,7 +67,10 @@ def serialise(n, in_data):
             new_byte = np.uint8(0)
 
             for k in range(4):
+                #try:
                 new_byte |= in_data[i][(j*4) + k] << (k * 2)
+                #except:
+                 #   print(i)
 
             out_data.append(new_byte)