Solving poor GSM signal in the server room to deliver text message alerts

Cell phone signal is often weakened or even blocked in the server room because of the building construction elements. Learn how you can use external antenna or repeater to fix it and effectively send text messages (SMS) from NetCrunch.

If you experience a weak or dropping cell signal in your server room, it may be the result of the building construction elements or server room walls blocking it. To amplify the cell signal, you can use an external antenna or a repeater/amplifier device for UMTS/HSPA+ bandwidth. Please remember that this device should support the same frequency bands as your local GSM provider.

There are two simple ways to fix weak or dropping GSM signal, and we have tested both of them.

modem

1. the external antenna option

When we have first measured the signal strength, the RSSI (Received Signal Strenght Indication) equaled -96 dB in the server room. It was insufficient for the NetCrunch Notification Service to correctly send text message (SMS). We have assumed that the signal strength must be at least -85 dB.

In order to increase the cell signal strength on modem, we have plugged an external antenna and positioned it outside of the server room, in the area of the office where we found out the cell signal to be better. The signal strength was only slightly improved - by just 3 dB (RSSI). Still not enough to send SMS message (radio noise). So we have extended the antenna cable to 10 m and have put it outside of the building. The cell signal strength had increased to -87 dB and NetCrunch was able to send SMS messages properly.

2. the repeater/amplifier of the cell signal

For our testing purposes we have used the cell signal booster - Diginity 3G UMTS/HSPA+ repeater/amplifier together with two omnidirectional antennas (see picture below).
repeater_and_antenna

We have plugged the first antenna to the outdoor port, and the second antenna to the indoor port of the repeater. Then we have placed the antenna near the window outside of the server room - near the window or somewhere where the signal strength is better. The strength of the RSSI cell signal has increased to -52 dB!

antenna As you can see, this has proved to be the best method for increasing the strength of cell signal and has successfully resolved the problem of failed dispatching of the text messages from the NetCrunch Server. This signal amplifier has strengthened the signal throughout the server room. repeater

If for the security reasons you don't want to amplify the cell signal in the server room, you can alternatively connect the indoor port of the repeater to the antenna outdoor port of the modem (by cable), thus amplifying the signal only for the NetCrunch Notification Service.

Please remember to always verify that both the repeater and the modem have the conforming values of electrical resistance - you can easily check it in the devices' specification docs.*


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