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Mobile multimedia broadcasting technologies
Several mobile multimedia broadcasting technologies have emerged during recent years. Traditionally, broadcasting has consisted of television and radio transmissions. Nowadays mobile broadcasting is more than just mobile TV. The transmission is general IP datacast (IPDC), which can carry any services such as streaming media or file delivery.
Broadcasting technologies can offer very high date rates to users because the whole (fixed) bandwidth is available for all users all the time. Broadcasting is especially suitable for reaching large number of users within small geographical area, where the capacity of systems like UMTS and WLAN cannot serve all users. When several users require the same content, the point-to-point delivery is a waste of scarce resources. The drawback is that the return channel has to be implemented with some other technology. Mobile broadcasting receivers are implemented typically in mobile phones, thus the return channel is easily available. Current competing standards include DVB-H, MediaFLO, T-DMB and ISDB-T. Also, 3GPP and 3GPP2 have developed broadcasting and multicasting extensions to UMTS (MBMS) and cdma2000 (BCMCS).
Our project focuses on second generation multimedia broadcasting standards, which is currently under active development. The aim is to provide HDTV transmission for terrestrial receivers and to match the capacity offered by state-of-the-art systems like WiMAX and 3G LTE. The project can be divided to two parts:
1. Analysis and enhancement of DVB-H
DVB-H defines a wide set of parameters that affect the performance of the system. Therefore, simultaneous tuning to achieve target data rate and error performance is of essence. For example, three-level error correction coding is defined in the standard, such as concatenated convolutional code and Reed-Solomon code in the physical layer and Reed-Solomon with optional cyclic redundancy check in the link layer. Thus, identical total code rate can be achieved with different code combinations.
The performance of DVB-H could be enhanced with efficient FEC decoding in the receiver. One possibility would be the utilization of soft-decision Reed-Solomon decoding. On the other hand, in broadcasting networks transport layer coding improve the transmission fidelity of video stream, since lost or corrupted data packets cannot be requested for retransmission due to the lack of return channel.
2. Design of future broadcasting systems
As the work for the next generation broadcasting system has started, it is important to find out efficient ways of data encapsulation, protocol stacking, error protection and modulation providing an adequate level of reception quality. The key issues to be dealt with include, but are not limited to, the following:
- How to choose efficient error correction mechanisms in combination with the packet structures used on each sublayer;
- What information should be transmitted in packet headers and how to protect this information in the most economical way;
- What are the best solutions, taking into consideration the limits of equipment complexity;
- What reasonable trade-offs exist between the quality of service and the commercial viability.
Research results are utilized in enhancing the performance of current state-of-the-art systems and offering novel solutions for future technologies. Following topics can be identified:
- Information theoretic aspects of broadcast channels
- Combination of framing (data encapsulation) with error coding
- Comparison of different multicarrier methods
- Combination of multicarrier modulation and MIMO
Advanced receiver algorithms for multicarrier systems (to be added later)
Team leader: Jarkko Paavola
Team supervisor: Valery Ipatov
Students involved in the project: Tero Jokela, Piritta Hakala, Jari Tissari, Eero Lehtonen