VoIP Received Throughput becomes lower with each new UE

[ChristophPargfrieder]

Hey,

I have an issue with a simulation where UEs are created according to their corresponding vehicle in SUMO (co-simulation setup using Veins): These are created according to flows (in total 100 vehicles are created over some defined time). Consequently, most of the UEs are created not at simulation start, but during the simulation. My setup involves a server, router, the UPF and 15 gNBs forming micro cells (carrier frequency is 3.5 GHz) and I use VoIP as app. When evaluating the results, I noticed that the first UEs have some voIPReceivedThroughput:mean larger than 1.3 kbps, but the throughput on application-level quickly gets lower for UEs that are created later on. The app configuration is as follows:

Server configuration

*.server.numApps = 100
.server.app[].typename = "VoIPSender"
.server.app[].localPort = 3000 + ancestorIndex(0)
.server.app[].destAddress = "UE[" + string(ancestorIndex(0)) + "]"
.server.app[].startTime = 1s
.server.app[].stopTime = 2500s

Client configuration

.UE[].numApps = 1
.UE[].app[0].typename = "VoIPReceiver"

Can someone identify any issue with my configuration? What could be the cause of the decreasing throughput over simulation time?