Teledesign TS4000C - Page 39

TS4000 Radio Modem User’s Manual AirNet Packet Protocol 33
Tx Index - ACK Packets = 1
Tx Index - Relay Packets = 1
Tx Index - Data Packets = Estimated Backlogged Nodes / Attempt Rate
Where:
Estimated Backlogged Nodes (number of nodes that simultaneously want
to transmit) = the greater of
A) Average Number of Backlogged Nodes or
B) 1/4 Maximum Possible Number of Backlogged Nodes
Attempt Rate Packet Detection Ratio=
Packet Detection Ratio = Slot Time / Total Packet Time
Total Packet Time = Attack Time + Packet Transmit Time + Decay Time
Packet Transmit Time = Packet Length / Channel Rate
Packet Length = (Data Bits + Overhead Bits)
x Framing Overhead x Coding Overhead
= (Data Bits + 112) x 1.1 { x 1.5 }
Overhead Bits = 14 bytes x 8 bits per byte = 112 bits
Framing Overhead = 1.1
Coding Overhead (optional) = 1.5
Packet Timeout = Relay Delays for Data Packet
+ Ack Packet Delay at Destination Node
+ Relay Delays for ACK Packet
Where:
Relay Delays for Data Packet = Relay #1Data Packet Delay
+ Relay #2 Data Packet Delay
...
...
+ Relay #Y Data Packet Delay
Relay #Y Data Packet Delay = Decay Time
+ (Y x Slot Time)
+ Attack Time
+ Data Packet Transmit Time
Data Packet Transmit Time = Data Packet Length / Channel Rate
Data Packet Length = (Data Bits + Overhead Bits)
x Framing Overhead x Coding Overhead
Overhead Bits = 14 bytes x 8 bits per byte = 112 bits
Framing Overhead = 1.1
Coding Overhead (optional) = 1.5
ACK Packet Delay at Destination Node = Decay Time
+ Attack Time
+ ACK Packet Transmit Time
Relay Delays for ACK Packet = Relay #1ACK Packet Delay
+ Relay #2 ACK Packet Delay
...
...
+ Relay #Y ACK Packet Delay
Tx Index
Packet Timeout