Cedric Marin

Robust MAC-lite and soft header recovery for packetized multimedia transmission

This paper presents an enhanced permeable layer mechanism useful for highly robust packetized multimedia transmission. Packet header recovery at various protocol layers using MAP estimation is the cornerstone of the proposed solution. The inherently available intra-layer and inter-layer header correlation proves to be very effective in selecting a reduced set of possible header configurations for further processing. The best candidate is then obtained through soft decoding of CRC protected data and CRC redundancy information itself. Simulation results for WiFi transmission using DBPSK modulated signals over AWGN channels show a substantial (4 to 12 dB) link budget improvement over classical hard decision procedures. We also introduce a sub-optimal and hardware realizable version of the proposed algorithm.

Robust header recovery based enhanced permeable protocol layer mechanism

This paper presents an enhanced permeable layer mechanism useful for reliable packetized multimedia transmission. Packet header recovery at various protocol layers using MAP estimation is the cornerstone of the proposed solution. The available intra-layer and inter-layer header correlation is used to define a reduced set of header configurations for further processing. The best candidate is then obtained through soft decoding based on CRC redundancy. Simulation results for a WiFi transmission scheme using DBPSK modulated signals over an AWGN channel show a substantial (4 to 12 dB) link budget improvement. A sub-optimal and hardware realizable version of the proposed algorithm is also presented.

Robust Video Decoding through Simultaneous Usage of Residual Source Information and MAC Layer CRC Redundancy

This paper presents a MAP estimation method of CAVLC (Context Adaptive Variable Length Coding) encoded sequences for robust decoding of H.264/AVC video stream. A sequential decoding algorithm jointly exploiting the residual source information (related to VLC codes and source characteristics) along with the MAC layer CRC redundancy in the transmission scheme is proposed. The branch selection metric in the decoding trellis incorporates the usually considered APP weighted by a CRC dependent factor. We also introduce a sub-optimal but hardware realizable version of the proposed algorithm. Significant link budget improvement results have been demonstrated for transmission schemes using BPSK modulated signals sent over AWGN channels.

Joint Exploitation of Residual Source Information and MAC Layer CRC Redundancy for Robust Video Decoding

This paper presents a MAP estimation method allowing the robust decoding of compressed video streams by exploiting the bitstream structure (Le., information about the source, related to variable-length codes and source characteristics) together with the knowledge of the MAC layer CRC (here considered as additional redundancy on the MAC packet). This method is implemented via a sequential decoding algorithm in which the branch selection metric in the decoding trellis incorporates a CRC-dependent factor, and the paths which are not compatible with the source constraints are pruned. A first implementation of the proposed algorithm performs exact computations of the metrics, and is thus computationally expensive. Therefore, we also introduce a suboptimal (with tunable complexity) version of the proposed metric computation. This technique is then applied to the robust decoding of sequences encoded using the H.264/AVC standard based on CAVLC and transmitted using a WiFi-like packet structure. Significant link budget improvement results are demonstrated for BPSK modulated signals sent over AWGN channels, even in the presence of channel coding.

Improved retransmission scheme for video communication systems

This paper defines a retransmission scheme for transmitting video data which allows the use of robust decoding (such as joint source and channel decoding) jointly with acknowledgement procedures. Conventional video communications use CRC-based retransmissions to obtain a nominal quality of the video (defined by the source coder). A lot of work has also been done on robust video transmission, which aims at providing a video of the best possible quality, for a given channel. However, robust techniques are not compatible with CRC-based retransmissions, and the quality of the received signal cannot really be controlled. As a result, the throughput is the best possible one, at the cost of a reduced quality. The scheme we define allows the use of robust decoding together with retransmissions, thus improving the throughput of the system while trying to keep the nominal quality. As a result, the proposed scheme is compatible with most actual mechanisms. The method is based on an evaluation of the quality of the robust estimate, followed by an hypothesis testing to decide whether a retransmission is necessary or not. Simulations evaluate the quality and the average number of retransmissions.

Robust MAC-Lite and Header Recovery Based Improved Permeable Protocol Layer Scheme

This paper presents an improved permeable layer mechanism useful for highly robust packetized multimedia transmission. MAP estimation-based packet header recovery at various protocol layers is the cornerstone of the proposed solution. This header-correction technique exploits the available intra-layer and inter-layer header correlation to define a reduced set of header configurations. The best candidate is then selected in the pre-defined set through a soft decoding based on CRC redundancy. To improve the decoding performance, we also generalize the principle of UDP-Lite and propose a robust MAC layer, called MAC-Lite. Simulation results for WiFi transmission over AWGN channels assess a substantial (12 dB) link budget improvement.