Congestion notification and rate-adaptation for real-time services in All-IP radio networks

This Master thesis investigates solutions for handling congestion in All-IP radio networks. A mixed traffic scenario including a video and voice conversation has been studied using an advanced radio network simulator. The preventive measures investigated in this thesis are a bit rate adaptation scheme together with a congestion detection and notification mechanism, for real time video traffic using the UDP protocol. The adaptation scheme is divided into two different stages. The first stage use packet losses as an indication of congestion and does bit rate adaptation based on this. The second stage uses congestion information received from the network as basis for adapting the video bit rate. The congestion detection mechanism implemented trigger congestion notifications by monitoring packet's buffer delay in radio transmitter. To transfer congestion notification from the radio transmitter to end-users, a new mechanism similar to ECN (Explicit Congestion Notification) has been implemented using the RTP protocol (header) instead of the IP protocol which is the case for ECN over TCP/IP. The implemented algorithms have been tested in a 3GPP SAE/LTE (Systems Architecture Evolution/Long-Term Evolution) system simulator. Simulation results show that radio resource management can be improved when congestion detection and notification is enabled in eNode B. Results also show that it is better in terms of radio resource management, to use congestion information received from eNode B than detecting congestion based on amount of packet loss.Validerat; 20101217 (root