Video transmission adaptation on mobile devices Julien Bourgeois, Emmanuel Mory * , Francois Spies Laboratoire d’Informatique de l’Universit e de Franche-Comt e (LIFC), IUT Belfort-Montb eliard BP 71427, pl. Tharradin, 25211 Montb eliard Cedex, France Abstract The development of multimedia streaming over wireless network is facing a lot of challenges. Taking into account mobility and highly variable bandwidth are the two major ones. Using scalable video content can solve the variable bandwidth problem only if the streaming architecture is able to react without latency. In this article, we present NetMoVie, an intermediate architecture based on real-time protocol which is able to adapt streams to the constraints of the wireless channel. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Scalable content; Wireless networks; Multimedia streaming; Mobile clients; Real-time protocol 1. Introduction The development of wireless networks band- width is changing the way people access multime- dia contents [1]. Three technologies are emerging: 2.5G (GPRS) [2], 3G (UMTS and FOMA) [3,4] and WLAN (802.11a, 802.11g and HiperLan2) [5] for private places called ‘‘hot spots’’. This success can be explained by the freedom of use induced by wireless networks. However, this freedom implies a greater management complexity for the under- lying multimedia architecture. Indeed, three clas- ses of constraints must be taken into account: network-related, operator-related and client-re- lated constraints. The management of multimedia contents on wireless networks is facing four challenges: mo- bility, shared, limited and variable bandwidth. When a client moves, it may change wireless access points (Base Transceiver Station or WLAN Access Point) and multimedia contents must be redirected as quickly as possible. As bandwidth always fluc- tuates, multimedia contents have to be adaptable according to the available bandwidth at a given moment. This quality modification must be as smooth as possible in order to avoid wide quality variations. For the moment, clients need to pay for access to wide wireless networks and operators need to optimize the utilization of their network. The ideal situation for an operator is when its network can be used by the maximum number of clients. The constraint here consist in optimizing the utilization of the wireless channel in order to allow the * Corresponding author. Tel.: +33-3-8199-4776; fax: +33-3- 8199-4791. E-mail addresses: julien.bourgeois@univ-fcomte.fr (J. Bour- geois), emmanuel.mory@univ-fcomte.fr (E. Mory), franc- ois.spies@univ-fcomte.fr (F. Spies). 1383-7621/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S1383-7621(03)00091-2 Journal of Systems Architecture 49 (2003) 475–484 www.elsevier.com/locate/sysarc