Abstract-This paper proposes the use of Adaptive LDPC AL-FEC codes for content download services over erasure channels. In Adaptive LDPC codes, clients inform the content download server of the losses they are experiencing. Using this information, the server makes FEC parity symbols available to the client at an optimum code rate. This paper presents an analytical model of the proposed Adaptive LDPC codes. The model is validated through measurements realized with an application prototype. Additionally, results show the performance of these codes in different scenarios, compared to the performance of nonadaptive AL-FEC, Optimum LDPC AL-FEC codes and an almost ideal rateless code. Adaptive LDPC AL-FEC codes achieve download times similar to almost ideal rateless codes with less coding complexity, at the expense of an interaction channel between server and clients.

De Fez Lava, I.; Fraile Gil, F.; Belda Ortega, R.; Guerri Cebollada, JC. (2012). Performance evaluation of AL-FEC LDPC codes for push content applications in wireless unidirectional environments. Multimedia Tools and Applications. 60(3):669-688. doi:10.1007/s11042-011-0841-y. that depends on the packet loss rate.

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This paper describes how FLUTE (File Delivery over Unidirectional Transport) and DASH (Dynamic Adaptive Streaming over HTTP) can be used to provide mobile video streaming services over broadcast wireless networks. FLUTE is a multicast protocol for multimedia file download. In this proposal, the protocol is adapted to provide video streaming services in crowded environments. Thus, video is delivered over a single connection to all viewers, reducing the traffic in the network. FLUTE incorporates an AL-FEC (Application Layered -Forward Error Correction) mechanism in order to improve the reliability of the broadcast communication channel. For streaming applications, AL-FEC improves the relationship between the PSNR (Peak Signal-to-Noise Ratio) of the received video and the bandwidth allocated to the broadcast connection. The AL-FEC hereby presented applies simple unequal error protection schemes to favor the download of key frames. Furthermore, the proposal is based on the same video segmentation mechanism as DASH and therefore, clients can connect to a DASH repository to repair errors in the segments. This paper shows that FLUTE and DASH can be seamlessly integrated into a hybrid broadcast/unicast streaming technology, providing flexibility to trade off PSNR and bandwidth depending on the conditions of the mobile network. KEYWORDSFile delivery over unidirectional transport (FLUTE), dynamic adaptive streaming over HTTP (DASH), media presentation description (MPD), video streaming, mobile wireless networks, unequal error protection (UEP).

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