IMS-Based Performance Analysis of a MANET Controlled by the Delay-Aware NUM System Andrzej Szwabe, Pawel Misiorek and Przemyslaw Walkowiak Institute of Control and Information Engineering Poznan University of Technology M. Curie-Sklodowskiej 5, 60-965 Poznan, Poland email: {Andrzej.Szwabe, Pawel.Misiorek, Przemyslaw.Walkowiak}@put.poznan.pl Abstract—This paper presents the results of the performance evaluation concerning 3G/3GPP IP Multimedia Subsystem (IMS) applications deployed in a wireless multi-hop network con- trolled by the Delay-Aware Network Utility Maximization Sys- tem (DANUMS). The main purpose of the DANUM system is simultaneous service of files and multimedia streams, i.e., types of traffic of different delay requirements. DANUMS combines a queue-level-based approximation of Max Weight Scheduling with a multi-path backpressure-oriented extension of the Optimized Link State Routing (OLSR) protocol. In order to evaluate DANUMS in a 3G videoconferencing scenario, we have integrated an Open IMS Core wired network installation with a wireless DANUMS testbed (playing the role of an IMS access network). The results of experiments presented in the paper show that by applying the DANUMS virtual queuing system, we can achieve a utility-aware coexistence of IMS audiovisual streams and non- IMS flows of different delay requirements. Index Terms—IP Multimedia Subsystem, NUM, wireless multi- hop testbeds. I. I NTRODUCTION The traffic of future wireless multi-hop networks is expected to be a mix of file-traffic and media streaming traffic. The former class may be realistically represented by audiovisual applications based on IP Multimedia Subsystem (IMS) [1] technology. However, multi-hop wireless networks proposed so far are not suitable to provide reliable access to IMS services [2], [4]. The results of the experiments presented in this paper were obtained on the basis of the Delay-Aware NUM system [5], [6], which was used to provide delay-aware resource allocation in a wireless access network. A DANUMS-controlled network was employed to access heterogeneous services, including IMS-based videoconferencing. DANUMS combines the lead- ing techniques of modern theory-driven network control such as the Network Utility Maximization (NUM) [7] framework, the backpressure-based network control [8] and Max-Weight Scheduling (MWS) [9]. DANUMS is implemented as a system logically located above the MAC layer of the protocol stack. It consists of a delay-aware indirect flow control mechanism based on a distributed queuing system (transporting virtual utility units) and a packet forwarding component aimed at providing an approximation of MWS. Moreover, DANUMS is integrated with dynamic (fully proactive) routing based on a multi-path extension of the OLSR protocol [10], [11] - recently proposed by the authors of this paper as IETF Internet Drafts. We have chosen the OLSR protocol, the leading proactive routing protocol for MANETs as the basis of our multi-path extension. Our choice was motivated by the fact that OLSR enables higher efficiency of the MANETs serving multimedia streams [3]. The DANUM framework is designed to provide NUM- driven resource management to serve heterogeneous traffic, which - in the application scenario presented in this paper - includes IMS/SIP-based media streams. MANETs are known to be problematic as far as meeting delay constraints is concerned [8]. DANUMS is a wireless network control system which uniquely features the ‘awareness’ of different delay requirements of multiple applications served simultaneously in a single network. Therefore, DANUMS is worth investigating as a potential enabler for the real-world deployment of stream- ing media applications in wireless multi-hop networks. The presented system is interoperable with widely used protocols of the most typical wireless networking stack, such as TCP, UDP, IP, and 802.11 MAC [6]. From this perspective, testing IMS-readiness is a natural next step of development and experimental evaluation of DANUMS. The objective of this paper is to present the performance evaluation results concerning the application of IMS-based services over a wireless multi-hop network. In particular, the paper is aimed at showing that the reliable DANUMS-based access to IMS-based applications in MANETs is possible without the need of introducing additional mechanisms. The present contribution includes the results of experiments per- formed in a testbed in which the Open Source IMS Core Sys- tem [2] served as a tool for the wireless network performance measurement at the application layer. To our knowledge, DANUMS is the first implementation of NUM-derived scheduling and flow control which applies NUM-derived priorities both to the file traffic and multi- media streaming. Despite the fact that several other NUM- based implementations of systems for wireless network control have already been designed [12], [13], [14], all of them assume that queue-based NUM-derived control can be applied only to elastic (i.e., non-real-time) traffic. At the same time, some research on the application of the IMS technology over wireless networks has already been conducted [2], [4]. This paper presents the first results of experiments on IMS performance over a wireless multi-hop network controlled by 978-1-4577-0454-3/11/$26.00 ©2011 IEEE