The OPTIMIX project will focus on studying innovative solutions enabling enhanced video streaming in an IP based wireless heterogeneous system, based on cross layer adaptation of the whole transmission chain.To achieve this goal, it is proposed to develop a scheme including all elements of major importance in a point to multi point video streaming chain, in particular video coding, networking modules, MAC layer and physical layer, efficiently communicating together through the use of joint controllers (at the server side) and mobile unit observers (at the client side).Innovative techniques will be considered to improve the efficiency of scalable video codecs when used in a wireless multi user environment with respect to robustness, efficient dynamic compression and intelligent use of scalability schemes. The design of novel controlling strategies will be of main interest in the scope of point to multi-point scenarios, taking in consideration the aggregation of multiple feedbacks and the overall optimisation criteria in a multi user contextCross-layer mechanisms will be investigated, enabling the communication between application world and transmission world through the use of enhanced transport and network protocols. The network architecture of the system will be designed with respect to joint optimisation principles, bandwidth efficiency and real time constraints.Finally, the overall system will be validated with respect to end to end quality optimization, and innovative techniques developed in all the fields of interest of the project will be evaluated. Efficient bandwidth use, real time constraints, robustness and video quality will be amongst the major evaluation criteria .