Specifications

10.2.2. Time division of responses in Bridge mode
There is also the Tx delay setting in the menu. It shall be used in Bridge mode if multiple RTUs connected
to slave stations reply to a broadcast query from the centre. It is necessary to spread out their replies
to the radio channel in terms of time, otherwise a massive collision occurs. It can be achieved by setting
the TX delay parameter to an adequate sequence of TX delays (e.g. 0, 100, 200 ms as in the example
below) in individual remote RipEXes. The slave RipEXes will enter the radio channel successively and
no collisions will occur.
Note: The TX delay applies to every packet that is sent out to the radio channel.
Example:
The Centre broadcasts request and the RTUs 1, 2 and 3 generate the response and send it out to their
respective RipEX.
Radio
Radio1
Radio2
RTU1
Centre
Radio3
RTU2
RTU3
Request
Radio
Radio1
Radio2
RTU1
Radio3
RTU2
RTU3
Response
A
B
C
Centre
Radios 1, 2 and 3 have the TX delay parameter set to 0, 100 and 200 ms, respectively. Therefore,
Radio 1 starts transmitting just after reception of the frame from COM port. Upon 100 ms later, when
Radio 1 has completed transmission, Radio2 starts transmitting. Finally, 200 ms after the reception of
the packet from RTU, Radio 3 starts its transmission. All three responses are thus sequentially sent to
the Centre and no collision happens.
Tx
Radio1
RadioTransmission
RadioReceiving
A
Radio2
B
COM
COM
Radio3
Rx Rx Rx
A B C
Centre
A
C
time0
Tx
B
Tx
C
A B C
Txdellay2
Txdellay3
Txdellay1=0
The TX delay parameter coresponds to multiples of maximum packet length expected and shall be set
in miliseconds. The packet transmission time through radio channel can be calculated as follows:
t = (n + 12). 8/(b . fec)
where:
RipEX Application notes – © RACOM s.r.o.56
Channel access