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Diplom-Vortrag: Digital Fountain Codes for Future Mobile Communication Systems
Wilfried Winkelhüsener
24. Oktober 2011
11:30 Uhr
Hörsaal 4G IKS
The usage of mobile communication systems has been going through a heavy change in the recent years. Mobile devices have made a transition from cellular phones to handheld devices that support a large variety of applications. The increasing computational power of mobile communication systems led to a fast rise of data traffic. Due to this tremendous expansion of data traffic, the limited amount of radio resources runs short so that a more and more efficient usage is inevitable. One possibility to increase the efficiency of data distribution is point-to-multipoint (PTM) distribution like broadcast or multicast. The increasing importance of distributing files via PTM transmission led to a definition of the Multimedia Broadcast/Multicast Service (MBMS) by the 3rd Generation Partnership Project (3GPP). MBMS consists of IP based multicast flows and generally reuses the existing signal processing and network infrastructure from UMTS. The reliable delivery of data requires a capable error correcting scheme at a layer above the physical layer (PHY). An appropriate and powerful solution for PTM transmissions is the usage of application layer forward error correction (AL-FEC) on basis of digital fountain (DF) codes that possess a high flexibility due to their rateless property and do not require feedback information. Besides the necessity of AL-FEC in order to facilitate reliable data delivery a system can further profit from the usage of a capable AL-FEC code. The additional FEC on the application layer on top of the physical layer FEC (PHY-FEC) enables the operating on higher PHY loss rates from which the whole system can benefit in terms of energy and complexity savings.
This work deals with the usage of digital fountain codes as AL-FEC codes for the distribution of MBMS data in combination with PHY-FEC. The focus is on the so-called Raptor 10 code which is currently the most popular raptor code and is considered in various broadcast/multicast standards. After the analysis of Raptor 10 and its usage within MBMS, the combined AL- and PHY-FEC is analyzed with respect to saving transmission energy and PHY-FEC complexity. Furthermore, the combined AL- and PHY-FEC performance within a radio cell is determined for different modulation and coding schemes.
