689 research outputs found
Predictive Encoder and Buffer Control for Statistical Multiplexing of Multimedia Contents
International audienceStatistical multiplexing of video contents aims at transmitting several variable bit rate (VBR) encoded video streams over a band-limited channel. Rate-distortion (RD) models for the encoded streams are often used to control the video encoders. Buffering at the output of encoders is one of the several techniques used to smooth out the fluctuating bit rate of compressed video due to variations in the activity of video contents. In this paper, a statistical multiplexer is proposed where a closed-loop control of both video encoders and buffers is performed jointly. First, a predictive joint video encoder controller accounting for minimum quality, fairness, and smoothness constraints is considered. Second, all buffers are controlled simultaneously to regulate the buffering delays. This delay is adjusted according to a reference delay constraint. The main idea is to update the encoding rate for each video unit according to the average level of the buffers, to maximize the quality of each program and effectively use the available channel rate. Simulation results show that the proposed scheme yields a smooth and fair video quality among programs thanks to the predictive control. A similar buffering delay for all programs and an efficient use of the available channel rate are ensured thanks to the buffer management and to the predictive closed-loop control
Source-Channel Diversity for Parallel Channels
We consider transmitting a source across a pair of independent, non-ergodic
channels with random states (e.g., slow fading channels) so as to minimize the
average distortion. The general problem is unsolved. Hence, we focus on
comparing two commonly used source and channel encoding systems which
correspond to exploiting diversity either at the physical layer through
parallel channel coding or at the application layer through multiple
description source coding.
For on-off channel models, source coding diversity offers better performance.
For channels with a continuous range of reception quality, we show the reverse
is true. Specifically, we introduce a new figure of merit called the distortion
exponent which measures how fast the average distortion decays with SNR. For
continuous-state models such as additive white Gaussian noise channels with
multiplicative Rayleigh fading, optimal channel coding diversity at the
physical layer is more efficient than source coding diversity at the
application layer in that the former achieves a better distortion exponent.
Finally, we consider a third decoding architecture: multiple description
encoding with a joint source-channel decoding. We show that this architecture
achieves the same distortion exponent as systems with optimal channel coding
diversity for continuous-state channels, and maintains the the advantages of
multiple description systems for on-off channels. Thus, the multiple
description system with joint decoding achieves the best performance, from
among the three architectures considered, on both continuous-state and on-off
channels.Comment: 48 pages, 14 figure
40 Gbps Access for Metro networks: Implications in terms of Sustainability and Innovation from an LCA Perspective
In this work, the implications of new technologies, more specifically the new
optical FTTH technologies, are studied both from the functional and
non-functional perspectives. In particular, some direct impacts are listed in
the form of abandoning non-functional technologies, such as micro-registration,
which would be implicitly required for having a functioning operation before
arrival the new high-bandwidth access technologies. It is shown that such
abandonment of non-functional best practices, which are mainly at the
management level of ICT, immediately results in additional consumption and
environmental footprint, and also there is a chance that some other new
innovations might be 'missed.' Therefore, unconstrained deployment of these
access technologies is not aligned with a possible sustainable ICT picture,
except if they are regulated. An approach to pricing the best practices,
including both functional and non-functional technologies, is proposed in order
to develop a regulation and policy framework for a sustainable broadband
access.Comment: 10 pages, 6 Tables, 1 Figure. Accepted to be presented at the
ICT4S'15 Conferenc
Statistical Multiplexing of H.264 programms
The advent of H.264/AVC is going to change the way Digital Television programs are broadcast. Each program can be independently encoded or jointly encoded resulting thus
in a more efficient way to distribute the available channel bandwidth. This paper presents a combined coding scheme for
multi-program video transmission in which the channel capacity is distributed among the programs according to the program complexities. A complexity bit rate control algorithm based on the Structural Similarity Index (SSIM) is proposed.
SSIM metric is presented under the hypothesis that the Human Visual System (HSV) is very specialized in extracting structural information from a video sequence but not in extracting the errors. Thus, a measurement on structural distortion should
give a better correlation to the subjective impression. Current simulations have demonstrated very promising results showing
that the algorithm can effectively control the complexity of the multi-program encoding process whilst improving overall subjective
Turbo trellis-coded hierarchical modulation assisted decode-and-forward cooperation
Hierarchical modulation, which is also known as layered modulation, has been widely adopted across the telecommunication industry. Its strict backward compatibility with single-layer modems and its low complexity facilitate the seamless upgrading of wireless communication services. The potential employment of hierarchical modulation in cooperative communications has the promise of increasing the achievable throughput at a low power consumption. In this paper, we propose a single-relay aided hierarchical modulation based cooperative communication system. The source employs a pair of Turbo Trellis-Coded Modulation schemes relying on specially designed hierarchical modulation, while the relay invokes the Decode-and-Forward protocol. We have analysed the system’s achievable rate as well as its bit error ratio using Monte-Carlo simulations. The results demonstrate that the power consumption of the entire system is reduced to 3.62 dB per time slot by our scheme
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