User's Manual

COMPANY CONFIDENTIAL
RF-TWACS Based AMR System DCSI CUSTOMER PRODUCT SPECIFICATION
May 30, 2003 Application Notes – Rev. 1 13
The transmission of data from the RMTR to the EMTR follows this sequence:
1. The RMTR wakes up once an hour and attempts to create a session with an EMTR in
order to upload readings and tamper information. The RMTR attempts to create a
session on a quiet channel using a low-power amplifier-gain. After each Request-to-
Send (RTS) packet is transmitted, the RMTR listens on the return frequency of the
same channel for an acknowledgment to indicate acquisition by a suitable EMTR.
The acknowledgment contains the EMTR’s serial number so that a certified link can
be established.
Acquisition Sequence:
The RMTR attempts to acquire a session by transmitting an RTS packet on the
clearest channel at the same power level of the last successful session (in the case
of a first time acquisition, it begins with the lowest power level). If this
acquisition fails, it tries each of the remaining 4 acquisition channels at that power
level, then, if the attempt on each channel fails, it will increase power to the next
higher power level. After cycling through each of the channels and escalating up
to the highest power level (attempting as many as 15 retries), it will go back to
“sleep” and reattempt later.
2. If the link is accepted by the EMTR, it replies with a confirmation packet including
the RMTR’s serial number in the transmission, forming a “source - destination”
routing packet.
3. The data field in all packets is encrypted for security purposes.
4. After the EMTR accepts the link, it takes control of the session and issues commands
to harvest data.
5. The EMTR informs the RMTR that it is has completed all necessary exchanges by
sending a “completion” message to the RMTR. This message is important to the
RMTR, without it the RMTR must assume that a jam has occurred and that the data
upload must be retried at a later time on another channel beginning with the first
exchange.
Figure 9 below shows a state diagram that summarizes the described operations.