The technological set-up of the Mobile Unit comprises a set of different network, multimedia and presentation components, integrated in a logical multimedia system organised in a simple three-layer modular structure. The unit can be used for video/audio streaming, multimedia-based presentations or as a connectivity tool. The whole concept of the mobile unit can be based on three main parts: network module, presentation module, multimedia module. This modular structure can be shown as a layered system where two layers directly depend on the third one.
Network module includes all the equipment necessary for the communication and enables free computers’ location in the presentation module. Its main components are 10/100 MB Ethernet switch, router and wireless LAN base station (Apple Airport). Internet connection can be made using several possibilities: direct connection in situations where it is possible (fairs, universities); satellite connection (two-way) in occasions where we need fast and stabile Internet connections (i2TV streaming) and finally ISDN connection which can be used in situation where only some presentations need to be held without need for higher bandwidth. Wireless LAN makes possible dislocation of presentation module in an area approximately 50 meters from its base station. Satellite Internet connection works at bit rates up to 1 Mbps (uplink). Most of our servers are located at the FhG, so this solution guarantees that the connection between Mobile Unit and FhG´s network will be fast enough. ISDN router is configured to make Internet connection using FhG’s dial up callback service.
This module also includes a laptop, which is used for local data storage, web server and configuration of network devices (router, wireless LAN, MPEG encoder etc).
Multimedia Module consists of video camera, wireless microphone unit, audio/video mixer, hardware MPEG-1/MPEG-2 encoder, audio amplifier, DAT recorder, VCR, DVD player and a PC workstation or laptop with good multimedia capabilities. High multimedia performance of this component enables real time audio/video encoding and live video/audio feed to the media server. In our case, media server is located at the FhG. The Mobile Unit delivers the streams to the FhG located media server, which distributes the streams using FhG network infrastructure. The audio signal from wireless microphones goes through wireless microphone base station directly to the audio/video mixer. Both, video and audio signals from the camera can be transmitted using wireless technology. This part of the Multimedia Module is necessary because of the usually very poor quality of audio signal, when using microphone integrated in video camera.
Very important software part of this module is video/audio encoding solution. In our case, Kasenna MediaBase media server with 100 additional RealMedia streams has been chosen. Video recorder should support as many video formats (PAL, NTSC, SECAM) as possible. Different tape storage formats (VHS, S-VHS, DV) capabilities are of great importance as well.
Presentation module was not thought to be very compact. It consists of several client computers (in our case iMacs) which can be easily administrated and have internal WLAN cards (AirPort, Apple). Presentations laptop should also have high performance (Dell, Latitude, 800 MHz, 512MB RAM or Apple G4 PowerBook, 500 MHz, 512 MB RAM)) so it could also be used as a supplemental encoder for Multimedia Module in case that we need more then one stream transmission. Network color printer is also a part of this module. It has to support Mac as well as PC printing.