GSM Network: Dialout to mobile networks is down

Added by Konrad Meier over 7 years ago

At the moment calls to mobile telephony network (O2, Vodafone, T-Mobile, E-Plus) are not possible. We are working on a solution, but it will take some days to solve this problem. Calls to landline and University internal are still possible.

GSM Network: Small change for the outgoing lines to the mobile networks

Added by Konrad Meier almost 8 years ago

We changed the dial out to the mobile phone networks (Vodafone, E-Plus, T-Mobile, O2). Until today your connection was dropped if the outgoing line was busy. This was not an optimal solution since you did not know when the line was free again. We now changed the system to accept every call and wait for a free outgoing line. This means you will be connected once the line is free. If the line is free from the beginning, the dial out procedure is as before. If the line is busy you will hear "all circuits busy now" and will be connected when the line is free again.

GSM Network: SMS is now working

Added by Konrad Meier about 8 years ago

I am happy to report that sending SMS is now possible. You should be able to send SMS to every subscriber of the RZ-GSM network. Just write some text and send it to the three-digit subscriber number. If your phone asks you for the number of the message center (Kurzmitteilungszentrale), enter 44444.

GSM Network: Second BTS and Handover

Added by Konrad Meier about 8 years ago

The second BTS at the faculty is now up and running. This means the coverage of the area is now increased by the factor of two. The second BTS was important due to the signal shielding of buildings 51 and 52. The first measurements are promising, showing that there is a good signal in nearly the whole area. The only "weak" spot is building 82. This is kind of strange because the second BTS is not far away. But since this is one of the most important places, we are going to improve the situation. If necessary we will install a small third BTS in this building.

With the second BTS we are now able to do handover between the two BTS. Normally this should work without problems. If you happen to have problems, please feel free to send us your bug report.

Here is the new measurement:

green = good signal; red = bad signal

GSM Network: Statistics about the network usage

Added by Konrad Meier about 8 years ago

Two weeks after the announcement of the network, the network usage has cooled down a bit.
The peak was on 20.1.2011 with over 300 calls. This was really a heavy load for the network and we had some problems that day due to insufficient outgoing lines. Now we have about 40 calls each day, which should be ok. If you have problems don't hesitate to contact us.

Here is a new graphic about the network usage:

GSM Network: Received signal strength

Added by Konrad Meier about 8 years ago

Here is a new graphic showing the received signal strength at the faculty.

We are trying to improve the coverage based on this information.

green = good signal; red = bad signal

GSM Network: Feedback / status of the network

Added by Konrad Meier about 8 years ago

After making the project public to the members of the Faculty of Engineering, we received a lot of response. We were a bit overwhelmed by the huge interest in our project. It was probably caused by the title of the e-mail "free phone calls via RZ-GSM" ;-) The day after going public we were busy fixing some bugs and answering a lot of e-mails. However, I was happy about every person who contacted us, and I still am glad to hear from you.
Some users were asking about privacy within this network. The main question was: "Do you record or store the speech data of a call?" The answer simply is: NO.(I added this to the FAQs).

Here's a graphic that shows the usage of the network:

Here is the current status of the network:
  • The software is running stable after we fixed some null pointers.
  • SMS is not working
  • Speech calls are working
  • Incoming calls from the university telephony network are not working.

Since we are dealing with a lot more subscribers than during our tests, it is possible that you will not be able to reach anyone due to insufficient outgoing channels. Especially the channels to the mobile telephony networks are very limited at the moment.
The status quo is:
- German land line telephony network: 3 channels
- Mobile telephony networks: Vodafone, T-Mobile, O2, E-Plus: 1 channel per provider
- University internal telephones: 2 channels
- RZ-GSM internal: at most 3 calls at the same time

The basestation we are using supports up to 6 channels at the same time. This also explains why only 3 internal calls are possible at the same time (every internal call needs two channels).

We do recommend using a second mobile phone for the RZ-GSM network. This way you are still reachable on your ordinary number and at the same time you can use our free network.

We are planning to install a second basestation at the faculty to cover the whole area. The second basestation will be located in building 79. At the moment we are also measuring the received signal strength at different points to get some data on the coverage.
You can see the first results in this graphic:

green = good signal; red = bad signal


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