Use 4 carriers wit QAM16 to achieve 16kbps.

errors.py

@@ -0,0 +1,17 @@
+import common
+import sys
+
+tx, rx = sys.argv[1:]
+tx = open(tx).read()
+rx = open(rx).read()
+
+L = min(len(tx), len(rx))
+rx = list(common.to_bits(rx[:L]))
+tx = list(common.to_bits(tx[:L]))
+indices = [index for index, (r, t) in enumerate(zip(rx, tx)) if r != t]
+
+if indices:
+    total = L*8
+    errors = len(indices)
+    print('{}/{} bit error rate: {:.3f}%'.format(errors, total, (100.0 * errors) / total))
+    sys.exit(1)