Thursday 22 June 2017

Brief report about our four radio tests:

We have done four radio tests. Our communication works via WiFi and therefore we need a WiFi adapter for the ground station. The CanSat has an already integrated WiFi module.

The results we got from these tests were interestingly varied.

The first test, where the range between the CanSat and the ground station was 230m, was performed in a park. During this test, we faced some problems. We were not able to establish a connection or even get the ad-hoc network to work between the CanSat and the ground station. Instead of the normal infrastructure mode of the WiFi, where an access point is needed, which is working as an intermediary, we used the ad hoc mode, where our two peers, CanSat and ground station, can communicate directly.

The test result is an error rate of 20.04%, which means we received only ~80% of the data.

The operating system Linux that we are using back at the ground station, does not have a native support of the WiFi adapter. To get the WiFi to perform, we needed to install a driver. Nevertheless, it is not fully compatible with Linux.

Because of the problems and the test result, we decided to change the WiFi adapter. We replaced the adapter with a new one, which has another chipset (Atheros). The new one should have a better compatibility with Linux, which was the case.

We continued our radio tests with the new WiFi adapter.

The second test was performed / made at the same location of the first test with the old WiFi adapter. (Range 230m).

Luckily, we had no problems at this test and had no difficulties with establishing a connection between the CanSat and the ground station.

The test went well and the error rate was here comparatively small: 0.92%. Therefore, we could receive all data that the CanSat has sent.

The second and last test (with the new adapter) has been done with the range of 570m. At this test, we have also had difficulties. We could not get the CanSat connected to the ground station, and so received no packets, the cause of this problem is unfortunately unknown, it may be that we were out of range with the ground station.

We will perform more tests to determine the cause, and if we were really out of range.


In the past days we have completed our fourth radio test. Therefore we used a WiFI adapter with a chipset that is nativly supported by the Linux kernel.
The test location was the Werdersee. We had a range from 1 km.

Error rate: 7.85% Total received packets: 2114 Packets lost: 180 
Time difference: 689.0 Test duration: 1657.282

The test shows an error rate of 7.85%, which is a good result for such a long range. We also tried to directly access our CanSat through SSH and it worked!
This gives us the option to secure the data of the CanSat remotely, should our CanSat be not recoverable (for example if our CanSat lands on a tree).
Overall this test exceeded our expectations and we are positive that we’ll have a stable connection during the launch.

No comments:

Post a Comment

Note: only a member of this blog may post a comment.