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

University essay from LuleƄ tekniska universitet/Systemteknik/Datorkommunikation

Abstract: This Master thesis investigates solutions for handling congestion in All-IPradio networks. A mixed traffic scenario including a video and voiceconversation has been studied using an advanced radio network simulator. Thepreventive measures investigated in this thesis are a bit rate adaptationscheme together with a congestion detection and notification mechanism, forreal time video traffic using the UDP protocol. The adaptation scheme isdivided into two different stages. The first stage use packet losses as anindication of congestion and does bit rate adaptation based on this. Thesecond stage uses congestion information received from the network as basisfor adapting the video bit rate. The congestion detection mechanismimplemented trigger congestion notifications by monitoring packet's bufferdelay in radio transmitter. To transfer congestion notification from theradio transmitter to end-users, a new mechanism similar to ECN (ExplicitCongestion 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 (SystemsArchitecture Evolution/Long-Term Evolution) system simulator. Simulationresults show that radio resource management can be improved when congestiondetection and notification is enabled in eNode B. Results also show that itis better in terms of radio resource management, to use congestioninformation received from eNode B than detecting congestion based on amountof packet loss.