Need help troubleshooting LTE Connection issues with 2 eNodeBs

[Brian O'Neill]

Hi,

I'm having some trouble with my LTE connection when working with 28 or 30 nodes. My simulation has two EnB nodes placed at 0,0,0 and 0,200,0 with the nodes placed with a RandomDiscPositionAllocator between them. The LTE setup was done using the LteHelper and the PointToPointEpcHelper.  (Code)

I'm interested in any additional troubleshooting tips that anyone might have. I describe my analysis so far below and could use some help determining additional troubleshooting steps. Thank you for taking the time to read this!

When 30 nodes are present 4 will not connect to the remote host. I tried connecting over UDP sockets and TCP sockets. When enabling packet capture on the remote host I do not see any traffic at all coming from these 4 nodes. 

Ue nodes attach to the closest Enb, however when attaching all nodes to a single Enb, I get success from only 29 of the 30 nodes.

The below screenshot from netanim shows the position of the nodes with the ones that are not connecting circled in white. Sorry for the poor contrast, but there are light blue arrows coming from the two enbs one above and one below, so 2 nodes are not connecting from each enb.

Using the following line, I'm able to test that each Ue established a connection to a Enb and confirmed that all nodes have connected.

Config::Connect ("/NodeList/*/DeviceList/*/LteEnbRrc/ConnectionEstablished", MakeCallback (&NotifyConnectionEstablishedEnb))

Thank you!

-Brian O'Neill

[Zoraze Ali]

Hi Brian, 

If you are able to confirm that each UE is connecting successfully then you can try the following:

1. Make sure you are installing the application correctly for all the UE nodes.

2. From the application level traces make sure that all the UEs are transmitting the packets.

3. Increase the bandwidth (for example, see the LTE module example lena-radio-link-failure.cc).

4. Make sure the problematic nodes are not facing radio link failure. You can use the trace "RadioLinkFailure" of LteUeRrc class. See the example lena-radio-link-failure.cc.

5. If you do not want to simulate radio link failure, disable it by: Config::SetDefault ("ns3::LteUePhy::EnableRlfDetection", BooleanValue (false));

If you want us to try the example, please provide a simple script (only LTE). 

Kind regards,

Zoraze

[Brian O'Neill]

Zoraze,

Thank you so much for the steps! It looks like the issue was related to the bandwidth and increasing it has resolved my issue. 

- Brian O'Neill