Barrier to implement 4k resolution

Hi,
I tried 4k resolution (3840x2160) with mediasoup (Broadcast mode 1:N).
Configuration:

  1. One publisher
  2. One subscriber
  3. min fps 8 and maximum 25
  4. Server AWS ec2 c6g.8xlarge (which guaranteed 10 Gbps network bandwidth)
  5. Publisher and subscriber side local network with 150 Mbps bandwidth

Issue is that on subscriber side maximum resolution achieved 1920 x 1080
Any idea where is the issue?
Is there any webrtc limitation?