N O V A T E L W I R E L E S S T E C H N O L O G I E S L T D .
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A T C o m m a n d S p e c i f i c a t i o n - E x p e d i t e a n d M e r l i n
W i r e l e s s I P M o d e m s
Query Network Connection Status
Description:
The command to determine the current network connection status is used to determine is it is acceptable
for the host to go into a data mode and reliably exchange data over the CDPD network. The status
message returned is encoded using a string of five letters. Each letter position indicates the current status
of a particular condition or phase in the modems operation.
A or I
RSSI, received signal
strength intensity,
A = >-100 dBm
I = <-100 dBm
. “A” indicates a signal strength in excess of –100 dBm while an “I”
indicates a signal strength below –100 dBm. It is generally found that
modem operation is most reliable when the signal strength is above –
100 dBm.
B or J
Current
forward
channel error rate
B = < 3%
J = > 3%
The second letter is used to indicate the current error rate on the
forward channel (modem receiver). The letter “B” indicates an error rate
lower than 3%, which is considered acceptable in most applications
since it can be easily corrected within the Reed Solomon coding
scheme. The letter “J” is used to indicate an error rate above 3%.
Errors above 3% can cause delays in data reception and may require
retransmission of data between the modem and the base station.
C or K
Found CDPD Service
C = Service found
K = No Service yet
The third letter is used to indicate that the modem has found a cellular
channel with CDPD service. The modem indicates the existence of the
available channel using a “C”. Until a channel is found the modem will
issue a “K” in the third letter position. Should the modem not establish a
connection it will hunt for another channel, putting out a “K” until a new
channel is found.
D or L
Registration indicator
D = Registered
L = Not Registered
The fourth letter is the registration indicator. A “D” indicates that the
modem has successfully acquired a channel and registered with the
network. Data modes can then be used. An “L” in this position indicates
that the modem has not yet registered.
E or M
Scan Mode
E = Set on Channel
M = Scanning
The fifth and final letter is used to indicate when the modem is scanning
and when the modem is fixed on a channel. An “E” indicates that the
modem is fixed on a channel while an “M” indicates the modem is
searching for channels. As defined within the CDPD specification the
modem will periodically scan other channels trying to find a stronger
signal or one that is not as heavily used.
Format:
ATS57?
To determine current network status
Validity:
This command is valid in AT Command mode only.
Other Considerations:
