An Efficient NVoD Scheme Using Implicit Error Correction and Subchannels for Wireless Networks

TL;DR

The paper addresses packet-loss-prone wireless nVoD by extending the implicit error correction (IEC) framework with subchannels (IEC-S) to boost decoding efficiency and early playback quality without fundamentally changing the implicit redundancy model. IEC-S partitions each segment into $\lambda$ subsegments transmitted over $\lambda$ subchannels, trading some encoding/decoding complexity for substantial gains in initial decoding performance and subjective quality, while preserving reliability through implicit redundancy and potential network coding integration. The authors derive analytical bounds and asymptotic behavior for packet loss protection with subchannels, provide complexity estimates $O(\lambda^2 I M)$, and validate the approach via simulations showing improved Y-PSNR and robustness under varying $p_e$ and $\lambda$. The work demonstrates that IEC-S can achieve better early playback and sustained performance in wireless cooperative networks, making nVoD more scalable for large audiences without requiring proportional bandwidth growth.

Abstract

Implicit Error Correction (IEC) is a near Video-on-Demand (nVoD) scheme that trades bandwidth utilization for initial playback delay to potentially support an infinite number of users. Additionally, it provides error protection without any further bandwidth increase by exploiting the implicit redundancy of nVoD protocols, using linear combinations of the segments transmitted in a given time slot. However, IEC packet loss protection is weaker at the beginning of the playback due to the lack of implicit redundancy and lower decoding efficiency, resulting in worse subjective playback quality. In tackling this issue, this paper contributes with an extension of the original nVoD architecture, enhancing its performance by adding a new element namely, subchannels. These subdivisions of the original channels do not provide further packet loss protection but significantly improve the decoding efficiency, which in turn increases playback quality, especially at the beginning. Even for very high packet loss probabilities, subchannels are designed to obtain higher decoding efficiency which results in greater packet loss protection than that provided by IEC. The proposed scheme is especially useful in wireless cooperative networks using techniques such as network coding, as content transmissions can be split into different subchannels in order to maximize network efficiency.

Figures (18)

• Figure 1: Illustrative example of a suboptimal HB scheme (constant number of channels per time slot and a single segment size).
• Figure 2: The same scheme as in Figure \ref{['fig1']} with implicit error correction and a redundancy channel.
• Figure 3: Maximum admissible $p_{n,b,R}$ as new original segments become available for $M=8$ and $R=0$.
• Figure 4: Maximum admissible $p_{n,b,R}$ as new original segments become available for $M=7$ and $R=1$.
• Figure 5: Relationship between admissible lower bound ($p_{n,b,R}$, $b=1$) and initial playback delay for content duration=$120min$ and $I=8$.