User's Manual

19
Document Number: 0100SM1401 Issue: 10-14
ARQs
Automatic Repeat reQuests (ARQs): When enabled, ARQs confirm successful reception of data transmitted over the air.
Each time a radio (originator) transmits data, the receiving radio replies with an acknowledgement back to the originator,
confirming successful reception of the data. If an acknowledgement is not received by the originator within an acceptable
time frame, the originator declares the data lost and retransmits the data. The number of retransmit attempts is user
configurable (i.e. when ARQ = 2, there will be a maximum of two retransmit attempts per message).
When Ethernet data is not successfully transmitted over a radio network (i.e. due to a data collision), Ethernet devices can
interpret this as network congestion, resulting in unnecessary slow down of SCADA polling. ARQs increase the probability of
successful transportation of data over the radio link. However, when ARQs are enabled, the capacity of the radio network is
reduced, due to the ARQ acknowledgements. As only one device can generate an acknowledgement for received data, ARQs
are not applicable to broadcast or multicast traffic
RF Speeds and Sensitivity
The Trio Q data radios use continuous phase
modulation (CPM) which supports up to 10 Watts
of transmitter output power, even at the fastest RF
data rate.
This avoids the need to compromise on range
when operating at the fastest speeds. Two
different radio variants and modulation types
are available, depending on the regulatory
requirements (FCC or ACMA/ETSI).
•TBURQx4xx-E00xxxxxx: ‘E’ denotes ACMA/ETSI
•TBURQx4xx-F00xxxxxx: ‘F’ denotes FCC
Note: Contact your local sales representative if
you need to confirm the applicable model for your
regulatory region.
Efficiency and Bandwidth
Regulatory
Region
Channel Bandwidth
(KHz)
RF Speed (Kbps)
BER threshold
(10^6)
FCC/IC
12.5
8
16
24
32
-113
-110
-107
-100
ACMA/
ETSI
12.5
8
16
24
32
-113
-110
-107
-100
25
14
28
42
56
-111
-109
-106
-99
Host Application to Entry
Point
Entry Point to Remote Remote to RTU
SCADA POLL SCADA POLL SCADA POLL
ARQ ACK
(ARQ flag enabled)
RTU RESPONSE
RTU RESPONSE RTU RESPONSE
(ARQ flag enabled)
ARQ ON
Typical data transaction with ARQ enabled
ARQ ON
ARQ ACK
The example below shows the ARQ behavior between a pair of radios during a typical data transaction.
Part D – Feature Detail