Real-time Demonstration of MPEG-4 based Video Telephony over Wireless Systems using WiNe2 1 Thomas STOCKHAMMER (1) , Hrvoje Jenkac (2) , Peter STRASSER (3) , Günther LIEBL (4) , Daniel PFEIFER (5) , Joachim HAGENAUER (6) , Tobias HINZ (7) , and Thomas WIEGAND (8) (1) Institute for Communications Engineering (LNT), Munich University of Technology (TUM), D-80290 Munich, Germany, E- mail: stockhammer@ei.tum.de (2) see (1), E-Mail: jenkac@ei.tum.de (3) see (1), E-Mail: peter.strasser@gmx.de (4) see (1), E-Mail: liebl@ei.tum.de (5) see (1), E-Mail: pfeifer@lnt.ei.tum.de (6) see (1), E-Mail: hagenauer@ei.tum.de (7) Image Processing Department, Heinrich-Hertz-Institute (HHI) D-10587 Berlin, Germany, E-Mail: hinz@hhi.de (8) see (7), E-Mail: wiegand@hhi.de Abstract In this work we present a flexible and fast, but yet accurate simulation environment for wireless sys- tems, which satisfies real-time constraints imposed by the respective applications and protocols of interest. We take into account system and demonstration aspects and concentrate on real-time video- conferencing services. The presented wireless network simulation and demonstration environment (WiNe2) includes several audio-visual applications, the corresponding transport protocols, a network- level simulator, and appropriate server and client software and hardware. We will present details in this work and show the suitability of this environment to test, evaluate, and assess video-conferencing applications over GSM GPRS and EGPRS. Video coding is based on MPEG-4, audio coding uses GSM AMR. Appropriate parameters to allow rate adaptation and error resilience are integrated in the multimedia encoding and decoding algorithms. Screenshots and subjective observations are dis- cussed in the paper, while the entire demonstration platform for this specific application will be pre- sented online at the conference. 1 WiNe2: Wireless Network Simulator based on ns-2; Phonetic spelling: [winetu]. 1 Introduction Applications like video telephony, video conferencing, mul- timedia streaming, or multimedia messaging for mobile terminals will be important features in emerging 2.5G, 3G, and future mobile systems and may be a key factor to their success. The video-capable displays and enhanced proc- essing power, as well as additional storage and memory capacity of new mobile devices, pave the road for these new applications. In addition, most current and future cellular networks, like GSM-GPRS, UMTS, or CDMA-2000, contain a variety of packet-oriented transmission modes: The latter allow transporting practically any type of IP-based traffic to and from mobile terminals, thus providing users with a sim- ple and flexible transport interface. However, compared to wireline networks, radio links exhibit some specific proper- ties, which often cause problems in combination with stan- dard network protocols: The residual bit error rate is often non-negligible, and the maximum attainable bit rate per user is significantly lower and time-variant. Furthermore, since multiple users with different applications and channel condi- tions share the costly resources power and bandwidth, sophisticated resource allocation strategies are required. Therefore, it is important to investigate the impact of cellular links on the end-to-end quality of real-time multimedia applications. This constitutes the need for a flexible and fast, but yet ac- curate simulation environment, which satisfies the real-time constraints imposed by the respective applications and protocols of interest. Concepts to realize these needs have previously been presented for the General Packet Radio Service (GPRS) in [1] and for Enhanced GPRS (EGPRS) in [2]. While [1] and [2] focus on the real-time wireless net- work level simulator part, in [3] the work in [1] has been extended by taking into account the system and demonstra- tion aspects for several IP-based applications with concen- tration to real-time services over GPRS. In this work we will first review the wireless network simula- tion and demonstration environment (WiNe2). We will pre- sent concepts and realization details and show the suitabil- ity of this environment to test, evaluate, and assess wire- less real-time multimedia applications with a focus on MPEG-4 based video-telephony. Next, we extend the work of [3] by including several new components in the modular WiNe2 concept: Among others, the GSM system is up- graded from GPRS to EGPRS, simple audio coding will be replaced by GSM AMR, and Robust Header Compression (RoHC) is integrated in WiNe2. Whereas simple screen- shots are used to explain the WiNe2 concepts, the entire demonstration platform will be presented at the conference. 2 The WiNe2 Concept Multimedia transmission over mobile systems requires huge design, implementation, and realization flexibility on