Added calculator utility

docs/utilities/rns_audio_call_calc.py

@@ -0,0 +1,122 @@
+import os
+import math
+import RNS
+import RNS.vendor.umsgpack as mp
+
+def simulate(method="msgpack"):
+    # Simulated on-air link speed
+    LINK_SPEED = 9600
+
+    # Packing method, can be "msgpack" or "protobuf"
+    PACKING_METHOD = method
+
+    # The target audio slot time
+    TARGET_MS = 70
+
+    # Packets needed per second for half-duplex audio
+    PACKET_PER_SECOND = 1000/TARGET_MS
+
+    # Effective audio encoder bitrate
+    CODEC2_RATE = 1200
+
+    # Maximum number of supported audio modes
+    MAX_ENUM = 127
+
+    # Per-packet overhead on a established link is 19
+    # bytes, 3 for header and context, 16 for link ID
+    RNS_OVERHEAD = 19
+
+    # Physical-layer overhead. For RNode, this is 1
+    # byte per RNS packet.
+    PHY_OVERHEAD = 1
+
+    # Total transport overhead
+    TRANSPORT_OVERHEAD = PHY_OVERHEAD+RNS_OVERHEAD
+
+    # Calculate parameters
+    AUDIO_LEN = int(math.ceil(CODEC2_RATE/(1000/TARGET_MS)/8))
+    PER_BYTE_LATENCY_MS = 1000/(LINK_SPEED/8)
+
+    # Pack the message with msgpack to get real-
+    # world packed message size
+
+    if PACKING_METHOD == "msgpack":
+        # Calculate msgpack overhead
+        PL_LEN = len(mp.packb([MAX_ENUM, os.urandom(AUDIO_LEN)]))
+        PACKING_OVERHEAD = PL_LEN-AUDIO_LEN
+    elif PACKING_METHOD == "protobuf":
+        # For protobuf, assume the 8 bytes of stated overhead
+        PACKING_OVERHEAD = 8
+        PL_LEN = AUDIO_LEN+PACKING_OVERHEAD
+    else:
+        print("Unsupported packing method")
+        exit(1)
+
+    # Calculate required encrypted token blocks
+    BLOCKSIZE = 16
+    REQUIRED_BLOCKS = math.ceil((PL_LEN+1)/BLOCKSIZE)
+    ENCRYPTED_PAYLOAD_LEN = REQUIRED_BLOCKS*BLOCKSIZE
+    BLOCK_HEADROOM = (REQUIRED_BLOCKS*BLOCKSIZE) - PL_LEN - 1
+
+    # The complete on-air packet length
+    PACKET_LEN     = PHY_OVERHEAD+RNS_OVERHEAD+PL_LEN
+    PACKET_LATENCY = round(PACKET_LEN*PER_BYTE_LATENCY_MS, 1)
+
+    # TODO: This should include any additional
+    # airtime consumption such as preamble and TX-tail.
+    PACKET_AIRTIME = round(PACKET_LEN*PER_BYTE_LATENCY_MS, 1)
+    AIRTIME_PCT = round( (PACKET_AIRTIME/TARGET_MS) * 100, 1)
+
+    # Calculate latencies
+    TRANSPORT_LATENCY  = round((PHY_OVERHEAD+RNS_OVERHEAD)*PER_BYTE_LATENCY_MS, 1)
+
+    PAYLOAD_LATENCY    = round(PL_LEN*PER_BYTE_LATENCY_MS, 1)
+    RAW_DATA_LATENCY   = round(AUDIO_LEN*PER_BYTE_LATENCY_MS, 1)
+    PACKING_LATENCY    = round(PACKING_OVERHEAD*PER_BYTE_LATENCY_MS, 1)
+    
+    DATA_LATENCY       = round(ENCRYPTED_PAYLOAD_LEN*PER_BYTE_LATENCY_MS, 1)
+    ENCRYPTION_LATENCY = round((ENCRYPTED_PAYLOAD_LEN-PL_LEN)*PER_BYTE_LATENCY_MS, 1)
+    if ENCRYPTION_LATENCY == PER_BYTE_LATENCY_MS:
+        E_OPT_STR = "(optimal)"
+    else:
+        E_OPT_STR = "(sub-optimal)"
+
+    TOTAL_LATENCY      = round(TARGET_MS+PACKET_LATENCY, 1)
+
+    print( "\n  === Simulation Parameters ===")
+    print(f"  Packing method       : {method}")
+    print(f"  Sampling delay       : {TARGET_MS}ms")
+    print(f"  Audio data           : {AUDIO_LEN} bytes")
+    print(f"  Packing overhead     : {PACKING_OVERHEAD} bytes")
+    print(f"  Payload length       : {PL_LEN} bytes")
+    print(f"  AES blocks needed    : {REQUIRED_BLOCKS}")
+    print(f"  Encrypted payload    : {ENCRYPTED_PAYLOAD_LEN} bytes")
+    print(f"  Transport overhead   : {TRANSPORT_OVERHEAD} bytes ({RNS_OVERHEAD} from RNS, {PHY_OVERHEAD} from PHY)")
+    print(f"  On-air length        : {PACKET_LEN} bytes")
+    print(f"  Packet airtime       : {PACKET_AIRTIME}ms")
+
+    print( "\n  === Results for "+RNS.prettyspeed(LINK_SPEED)+" Link Speed ===")
+    print(f"  Final latency        : {TOTAL_LATENCY}ms")
+    print(f"    Recording latency  : contributes {TARGET_MS}ms")
+    print(f"    Packet transport   : contributes {PACKET_LATENCY}ms")
+    print(f"      Payload          : contributes {PAYLOAD_LATENCY}ms")
+    print(f"        Audio data     : contributes {RAW_DATA_LATENCY}ms")
+    print(f"        Packing format : contributes {PACKING_LATENCY}ms")
+    print(f"        Encryption     : contributes {ENCRYPTION_LATENCY}ms {E_OPT_STR}")
+    print(f"      RNS+PHY overhead : contributes {TRANSPORT_LATENCY}ms")
+    print(f"")
+    print(f"  Half-duplex airtime  : {AIRTIME_PCT}% of link capacity")
+    print(f"  Full-duplex airtime  : {AIRTIME_PCT*2}% of link capacity")
+
+    if BLOCK_HEADROOM != 0:
+        print("")
+        print(f"  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
+        print(f"  Unaligned AES block! Each packet could fit")
+        print(f"  {BLOCK_HEADROOM} bytes of additional audio data")
+        print(f"  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
+
+print(  "\n= With mspack =================")
+simulate("msgpack")
+
+print("\n\n= With protobuf ===============")
+simulate("protobuf")