Abstract
We investigate the use of application layer FEC protection in DVB-T (Digital Video Broadcasting-Terrestrial) networks for the provision of mobile services. Mobile reception is characterized by variations of the received signal caused by fast fading and shadowing. DVB-T was originally designed for fixed and portable reception, and generally does not provide enough quality in mobile environments. The link layer protection mechanism MPE-FEC (Multi Protocol Encapsulation-Forward Error Correction) was standardized in DVB-H (Digital Video Broadcasting-Handheld) for the protection of mobile TV services. Although DVB-T itself does not incorporate any link or application layer protection mechanism, AL-FEC (Application layer Forward Error Correction) protection can be introduced in DVB-T in a backwards compatible way. By means of AL-FEC, it is possible to improve the robustness of DVB-T services for the provision of mobile TV. In this paper, we explain the concept of AL-FEC protection in DVB-T and evaluate its performance by means of laboratory measurements and dynamic simulations with shadowing. We study different configurations of AL-FEC and compare its performance with MPE-FEC. In this paper, we discuss some implementation aspects of AL-FEC in real scenarios and propose an implementation based on Raptor codes and hash sequences. We also present results obtained by a first AL-FEC prototype for DVB-T that demonstrates the feasibility of the approach.
Highlights
Digital Terrestrial TV (DTT) networks are being deployed worldwide, and it is planned that DTT services completely replace analogue TV in many European countries by latest 2012
AL-FEC has been configured to a protection period of 1 second in order to be comparable to the DVB-H service in terms of channel switching time
DVB-T and DVB-H employ the same physical layer, and the performance difference is due to the source packet size (528 bytes in the case of MPE-FEC and 184 bytes in the case of AL-FEC)
Summary
Digital Terrestrial TV (DTT) networks are being deployed worldwide, and it is planned that DTT services completely replace analogue TV in many European countries by latest 2012. A link layer protection mechanism called MPE-FEC (Multi Protocol Encapsulation-Forward Error Correction) [2] increases the robustness in mobile environments whereas a bursty transmission technique referred to as time slicing reduces the power consumption in receivers up to 90%. We study the use of AL-FEC protection in DVB-T in order to increase the robustness of the transmitted information and to achieve reception in mobile channels. Different codes may be used in order to provide AL-FEC protection for DVB-T services, in this paper we consider the use of Raptor codes [6], as they are efficient and lightweight in terms of decoding complexity This permits the FEC decoding to be done in generic software processors even on low-complexity devices and does not require any upgrades in hardware.
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