Tampere University of Technology has built a fully-operational DVB-H broadcasting channel. By transmitting suitable test streams and recording them with a portable receiver, it is possible to collect real-life transmission error traces covering various different mobile use cases.
There are two transmitter setups at TUT. The one shown below consists of proprietary broadcasting equipment. It is equipped with 50W power amplifiers and is capable of delivering DVB-H broadcasts within the town district of Hervanta.
The DVB-H playout server (Cardinal) is used for creating timesliced transport streams of A/V content in MPEG-4 files or live IP streams. File delivery over FLUTE data carousels is also supported. The playout server can create all the PSI/SI tables as well as Electronic Service Guide (ESG) files needed for a complete DVB-H service. Transmitting complete, pre-generated or recorded transport streams is also possible.
The DVB-H exciter takes the transport stream as its input and creates an OFDM modulated DVB signal to be broadcasted by the power amplifier and rooftop antenna. Optionally, it is possible to utilize also a diversity unit that prepares the RF signal for two-antenna transmitter diversity broadcasting.
For small-scale transmission experiments there is also a PC based transmitter setup that consists of a DekTec DTA-115 modulator card for creating the DVB signal. A set of open-source software tools (FATCAPS, JustDVB-IT) is used for creating the transport stream. Currently, this does not offer as full-featured solution as the Cardinal playout server because the ESG data cannot be automatically created. On the other hand, the open-source tools offer more flexibility in experimenting with new source/channel coding or content delivery schemes.
The DVB-H terminal devices available on consumer market can be used for viewing the broadcast as long as it contains the full ESG data. At TUT, we have Nokia models N92 and N77.
For research and development work a PC based receiver offers greater flexibility. For this, we use Linux computers equipped with DVB-H/T frontends. Linux operating system has built-in support for decapsulating the IP data in DVB-H transport streams (dvbnet). Alternatively, the streams can be decoded using the Decaps software developed within this project. Compared to dvbnet, it adds several features such as MPE-FEC error correction and collection of error rate statistics. Video players with RTP support can be used to view the decapsulated broadcasts.
The DVB-H monitor station developed in PLUTO project is used to collect reception statistics in moving vehicles and other mobile settings.
Transmission simulation environment
The simulation environment is based on the same open-source tools, Fatcaps and Decaps, as the Linux based transmitter and receiver setups. When the transport stream is passed through a channel model, the system forms an end-to-end simulation of the DVB-H transmission chain. The simulator can be used for both online and offline simulations. In the online case, live IP streams are encapsulated in transport streams and sent back to IP network by decapsulator. In offline simulations the different phases can be separated from each other and it is not necessary to use live IP streams as input and output. For instance, one can first generate a transport stream that is then passed through various different channel conditions.
For simulating the transmission channel we have a MATLAB/Simulink tool that models the OFDM modulation process and the physical transmission channel. This tool can generate error traces for DVB-H transmission simulations. Following physical channel models are supported:
- COST 207
- Typical Urban
- Bad Urban
- Rural Area
- Hilly Terrain
- Indoor Commercial
- Outdoor Residential
- Pedestrian Indoor
- Pedestrian Outdoor
- Vehicular Urban