Teledesign Systems Inc TS4000D User Manual
TS4000 Radio Modem User’s Manual
AirNet Packet Protocol
30
Where:
Decay Time = Tx Decay Time + Additional Transmit Attack Time
Attack Time = Tx Attack Time + Additional Transmit Attack Time
Attack Time = Tx Attack Time + Additional Transmit Attack Time
Tx Decay Time and Tx Attack Time are fixed values that are preset
for the radio in the TS4000. These values can be read out of the
TS4000 using the retrieve radio configuration menu or button. The
Additional Transmit Attack Time is the value set on the radio tab of
the modem configuration.
for the radio in the TS4000. These values can be read out of the
TS4000 using the retrieve radio configuration menu or button. The
Additional Transmit Attack Time is the value set on the radio tab of
the modem configuration.
ACK Packet Transmit Time = ACK Packet Length / Modulation Rate
An ACK packet fits in one data frame (16 bytes) of data. If coding is
used then 50% coding overhead is added to this.
used then 50% coding overhead is added to this.
ACK Packet Length
-Uncoded = 16 bytes x 8 bits per byte = 128 bits
-Coded = 128 bits x 1.5 = 192 bits
-Coded = 128 bits x 1.5 = 192 bits
Tx Attack Time = 20 ms
Tx Decay Time = 12 ms
Additional Transmit Attack Time = 0 ms
Over air channel rate = 9600 bps
Coding = Enabled
Tx Decay Time = 12 ms
Additional Transmit Attack Time = 0 ms
Over air channel rate = 9600 bps
Coding = Enabled
ACK Packet Transmit Time = 192 / 9600 = 20 ms
Packet Timeout Time = 12ms + 20 ms + 20 ms = 52 ms
Packet Timeout Time = 12ms + 20 ms + 20 ms = 52 ms
For a master-slave system, the data packet transmit time is constant for a given
packet size. As long as the channel is not busy, a data packet will be sent
immediately upon becoming available for transmission.
packet size. As long as the channel is not busy, a data packet will be sent
immediately upon becoming available for transmission.
Calculating the delay is very similar to the calculation for the packet timeout time
above.
above.
Total Packet Delay Time = Attack Time + Packet Transmit Time
Where:
Attack Time = Tx Attack Time + Additional Transmit Attack Time
Note that the packet delay time does not include the transmit decay time. This is
because the packet is available at the receiving modem as soon as all the data is
transmitted.
because the packet is available at the receiving modem as soon as all the data is
transmitted.
Packet Transmit Time = Packet Length / Channel Rate
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
Framing Overhead = 1.1
Coding Overhead (optional) = 1.5
Packet Length = (Data Bits + 112) x 1.1 { x 1.5 }
Example:
Data Packet Transmit
Time
Time