Normal tests on IP Modem

Date: 2014-01-17   Hits:1149

Since GRPS IP Modem is mostly used in remote sites, the stability of IP Modem is very important.

Some simple tests before installing the modems to the sites are not enough. Widely used unstable modems will cause big trouble for the monitoring system.

This is the modem stability test procedure. It will help you identify the modem performance and stability in a short time.


1. Online Idle State Test

Test reason: To test modem’s ability to maintain the established link itself. When there is no data transmission, modem maintains the link with heart beat. Modem can maintain the link as long as 1 hour without dropping out or reconnection.

Test method: After the modem is connected to the Data Service Center(DSC), don’t send any data between the modem and DSC to check how long the modem will maintain the connection. The longer, the better. At the end of the test, you should send some packets between the modem and the DSC to verify the idle link is still valid If neither of the modem nor DSC receives the packets, test fails.


2. DSC Close and Restart Test

Test reason: DSC may be closed temporarily for the system maintenance, so we need to test if the modem will recover connection after DSC recovers.

Test method: Keep the the DSC closed for a short time, such as 1 minute, and then restart DSC to check if the modem will be reconnected quickly. It’s should be less than 5 minutes. The sooner,the better. After several times of test, the modem must be always reconnected to DSC. Otherwise, test fails.


3. Frequent Two-way Small Packets Test

Test reason: To test modem’s ability to send and receive small packets frequently. This is how the modem works normally.

Test method: Send a packet of 100 bytes every 10 seconds from the modem and the DSC. Test like that for 30 minutes and calculate if modem loses connection or suffers from data loss. The best result is that neither of these two cases occurs. Otherwise, test fails.

In addition, you can observe if much data loss or data received error occurs. If so, test fails.

Tips: You can make pin 2 and pin 3 of modem RS232 shorted to make it loop circuit. So you only need to send data from the DSC to implement two-way communication .


4. Two-way Large Amount of PacketsTest

Test: sometimes the modem need to transfer large amount of data. So we need to test if the modem can handle it.

Test method: Send a packet of 1000 bytes every 2 seconds from the DSC to the modem., as well as from the modem to DSC. Test like that for 30 minutes and calculate if modem loses connection or both ways suffer from data loss. In general, in the pressure test, modem may drops out and reconnects or suffer from data loss. The reconnect times should be no more that 10. The less, the better. If modem fails to be reconnected to the DSC after dropping out or two-way communication fails after modem reconnects, test fails.

Besides, it’s normal for the modem to transfers data at a speed of 300 to 1500 bytes/s. If modem has a worse performance than that, test fails.


5. Antenna Unplugged Test

Test reason: In some sites, GPRS/GSM signal may get weak temporarily. The modem should reconnects after signal recovers and transfers data to DSC.

Test method:

(1) Unplug the antenna for a short time. While the modem is online, unplug the antenna for 1 minute, and send 3 packets of 100 bytes from the modem. After plug the antenna back , modem should reconnects to the DSC quickly and transfer the 3 packets to DSC. The sooner,the better. If the 3 packets are lost, test fails.

(2) Unplug the antenna for a longtime. While the modem is online, unplug the antenna for 30 minutes. After plug the antenna back, modem should reconnects to DSC and take less than 10 minutes to be reconnected. If it takes longer than 30 minutes, or even longer, test fails.


6. Power-on Repeat Test

Test reason: Sometimes power failure would occur. Modem should be reconnected to the DSC when power is on again.

Test method: Power the modem 20 times. The modem should be connected to the DSC within 2 minutes each time. If modem fails to be connected to the DSC for one time, test fails.


7. Call and Message Interference Test

Test reason: SMS message and call While the modem is connecting to the server and online shouldn’t influence the modem.

Test method: Power the modem and send two messages to the modem and call it twice in 10 seconds or so. The modem should be connected to the DSC as normal. After it’s connected, send two message and call it twice, wait 5 minutes and see if it’s still online. And then send 10 packets both ways to check if communication is OK.


8. SIM Card Unplugged Test( Optional)

Test reason: Bad environment in the sites, such as vibration and corrosive gas may cause short-time bad connection of the SIM card.

Test method: Firstly, when the modem is online, unplug the SIM card for 3 seconds and then plug it back.to check if the modem will be reconnected to the DSC and if communication is OK. Secondly,when the modem is online, unplug the SIM card for 60 seconds and check it again. If modem fails to be reconnected to the DSC after SIM card is plugged back, installing the modem in the sites with vibration and corrosive gas is not suggested


9.Power Supply Fluctuation Test( Optional)

Test reason: Battery or solar energy power supply in the sites may cause comprehensive power fluctuation. Modem should be able to adjust to this fluctuation.

Test method: Take 12V DC for example,there may be a voltage fluctuation from 5V to 14V. When the modem is connecting to the DSC, keep the voltage arranging between 3V and 16V to simulate charge and discharge. It’s normal for the modem to reset to factory settings during the test. If modem fails to be connected to the DSC after the power supply fluctuation, it’s not suggested to install the modem in the sites with battery power supply.


10. SIM Card Owing Fee Test(Optional)

Test reason: SIM card may become owing fee while modem is running. Modem should be reconnected to the DSC after SIM card is available.

Test method: Insert a SIM card owing fee in the modem and wait 10 minutes. Modem won’t be connected to the DSC due to owing fee. Meanwhile, call the SIM card number. You will get a prompt of out of service or restriction to call in. And then recharge the SIM card. Call the SIM card number again. If you hear it ringing, GSM service recovers. Wait 10 minutes to check if modem will be connected to the DSC. If modem isn’t connected to the DSC until reset the modem manually, test fails.


11. DDNS Test(Optional)

Test reason: DDNS is used instead offixed IP in some systems. DDNS may become invalid temporarily. In this cause,we need to make the test below.

Test method:

(1) Simulate an invalid domain. Point the domain to an invalid IP manually, and configure the domain in the modem instead of fixed IP. In this case, modem will fail to be connected to DSC. And then repoint the domain to the correct IP to check if modem will be online. The less time it takes, the better. If modem fails to be connected to the DSC, test fails.

(2)While the modem with domain configured in it online, unplug the antenna. Refer to the fifth test(Antenna Unplugged Test) to check if test passes.

(3)While the modem with domain configured in it online, refer to the second test(DSC Close and Restart Test)to check if test passes.

If DDNS test fails, it’s not suggested to use DDNS in the system.

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