Teledesign Systems Inc TS4000GL Manuel D’Utilisation

 
A master-slave system is one where the host application is designed so that only 
one node will ever attempt to transmit at a given time.  An example of this type of 
system is a polled system with a base station that sequentially poles a number of 
remote nodes.  In this case the base always initiates a pole and the remotes 
respond with the desired data. 
 
To set up AirNet for this type of system, select the Master-Slave selection in the 
Packet General tab of the modem configuration.  With this selection, the modem 
transmits waiting packets as soon as it detects an idle channel.  The master-
slave setting should not be used with systems that use store and forward 
repeaters. 
 
 
The packet timeout timer is used for only for individually addressed packets that 
expect an acknowledgment (ACK).  The packet timeout timer is started after a 
data packet is sent.  If an ACK is not received before the timer expires, then a 
retry transmission of the data packet is sent.  This timer should be set longer 
than the worst case time it takes to receive an ACK packet. 
 
For a master-slave system, an ACK packet is sent as soon as the data packet is 
received and the channel is idle.  This can start as soon as the decay time of the 
originating modem is finished. 
 
 

 

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 Hardware menu or button.  The 
Additional Transmit Attack Time is the value set on the radio tab of 
the modem configuration. 

 
 

 

An ACK packet fits in one data frame (16 bytes) of data.  If coding is 
used then 50% coding overhead is added to this. 

 

 
Tx Attack Time = 20 ms 
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