I have surveyed an area to measure signal strength for GSM coverage in that area. I used the command AT+CSQ to poll for signal strength after every minute....... I have generated a log file containing Latitude,Longitude and Received Signal Strength Indicator (RSSI)...... Now I need to know the generate a report that will tell that in which area we can have reliable voice call, data call, and sms.....
So my question is
1) What is the minimum value of rssi for a confirmed sms delivery?
2) What is the minimum value of rssi for a confirmed sms reception?
3) What is the minimum value of rssi for a ring to occur?
4) What is the minimum value of rssi for a reliable data call?
Searching the Internet I have found only a value of 12 which is reliable for data call but nothing for SMS........
Any help will be greatly appreciated
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NB: You shouldn't use the RSSI parameter as the measure for data call quality. The second value returned by +CSQ is the BER (bit error rate), is a much better estimate.
0: less than 0.2%
1: 0.2-0.4%
2: 0.4-0.8%
3: 0.8-1.6%
4: 1.6-3.2%
5: 3.2-6.4%
6: 6.4-12.8%
7: more than 12.8%
(99: not known or not detectable)
joghurt:
Basically I am surveying the availabilty of GSM Network coverage.....and the BER value is used only when you are connected through Data or Voice call...... the Log file I have obtained has BER 99 for all the records.....
My Log looks like this......
lat,long,RSSI,BER
and all the BER values are 99.......
SO I can only use RSSI values (They range from 0-31 and 99) to represent the availabilty of GSM Coverage.......
On some sites I have found a value 12 for a reliable data call but what about sending an SMS..... (My understanding is that SMS can be send even when a reliable Data or voice call can be made ) I have practically observed this phenemenon.....
So what is the Minimum RSSI (or dBm or mW) for SMS delivery and SMS reception ?
AT+CSQ[Enter]
Show field strength. field strength in dBm = -112 dBm+(2*X). When X gets bigger, field strength gets stronger. -104 dBm is the lowest number for voice call. Data calls are faulty because of noise. The radio-link-protocoll RLP corrects faults at transmission. By selecting the Z-Modem protrocoll the transmission is ensured all the way. Because Z-Modem sends in so called "blocks" you can see how good the RLP correction is by watching the net. transfer rate and repeatedly sent blocks. A GSM device reports +CR: Rel ASYNC on data transmission with RLP (for more infos refer to manual). RLP is supported by German operators. Foreign networks are only partial working at transparent mode without RLP. Please ask your network operator about the necessary parameters.
Source of this text on my website http://www.gsm-modem.de/gs
Regards
Meff
Sorry 'bout the delay i'm having ADSL woes....
SMS's are sent on the supervisory channel rather than a bearer channel.
If your device is registered on the network at all you should be able to send SMS's. this may have no relation to the signal strength returned by +CSQ.
Instead you can use the +CREG command to determine whether you are registered on the network.
Unfortunatly +CREG is not particularly dynamic it can take quite some time for the phone to de-register in a low signal condition (to allow for temporary singal loss eg when driving through a tunnel).
The best way to know if you can send an SMS is to check +CREG for registration and then try sending the SMS (which may fail).
Furthermore determining GSM signal strength is notoriously error prone, don't take +CSQ as anything more than an indication.
Thanks guys for your help.............
drelectro :
This is exactly what I am doing now.....
I check the Network availability with the AT+CREG command and then check the signal strength with AT+CSQ command.....
>>Unfortunatly +CREG is not particularly dynamic it can take quite some time for the phone to de-register in a low signal condition (to allow for temporary singal loss eg when driving through a tunnel).
(Good Information)
puuiup:
I will use the values you have suggested after checking for network registeration......
Thanks to all the Experts that have posted.....
Imran Arshad
Business Accounts
Answer for Membership
by: imarshadPosted on 2004-06-26 at 00:24:00ID: 11404434
I know dBm and mW values( and conversion from rssi) so if anyone can suggest these values as well it might prove helpful to me...... I think someone who has developed a GSM Engine will be the best to help me :)
Imran Arshad