2,780 research outputs found
Joint Wyner-Ziv/Dirty Paper coding by modulo-lattice modulation
The combination of source coding with decoder side-information (Wyner-Ziv
problem) and channel coding with encoder side-information (Gel'fand-Pinsker
problem) can be optimally solved using the separation principle. In this work
we show an alternative scheme for the quadratic-Gaussian case, which merges
source and channel coding. This scheme achieves the optimal performance by a
applying modulo-lattice modulation to the analog source. Thus it saves the
complexity of quantization and channel decoding, and remains with the task of
"shaping" only. Furthermore, for high signal-to-noise ratio (SNR), the scheme
approaches the optimal performance using an SNR-independent encoder, thus it is
robust to unknown SNR at the encoder.Comment: Submitted to IEEE Transactions on Information Theory. Presented in
part in ISIT-2006, Seattle. New version after revie
Capacity Bounds for a Class of Diamond Networks
A class of diamond networks are studied where the broadcast component is
modelled by two independent bit-pipes. New upper and low bounds are derived on
the capacity which improve previous bounds. The upper bound is in the form of a
max-min problem, where the maximization is over a coding distribution and the
minimization is over an auxiliary channel. The proof technique generalizes
bounding techniques of Ozarow for the Gaussian multiple description problem
(1981), and Kang and Liu for the Gaussian diamond network (2011). The bounds
are evaluated for a Gaussian multiple access channel (MAC) and the binary adder
MAC, and the capacity is found for interesting ranges of the bit-pipe
capacities
Disjoint LDPC Coding for Gaussian Broadcast Channels
Low-density parity-check (LDPC) codes have been used for communication over a
two-user Gaussian broadcast channel. It has been shown in the literature that
the optimal decoding of such system requires joint decoding of both user
messages at each user. Also, a joint code design procedure should be performed.
We propose a method which uses a novel labeling strategy and is based on the
idea behind the bit-interleaved coded modulation. This method does not require
joint decoding and/or joint code optimization. Thus, it reduces the overall
complexity of near-capacity coding in broadcast channels. For different rate
pairs on the boundary of the capacity region, pairs of LDPC codes are designed
to demonstrate the success of this technique.Comment: 5 pages, 1 figure, 3 tables, To appear in Proc. IEEE International
Symposium on Information Theory (ISIT 2009), Seoul, Korea, June-July 200
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
Achievable Rate Regions for Two-Way Relay Channel using Nested Lattice Coding
This paper studies Gaussian Two-Way Relay Channel where two communication
nodes exchange messages with each other via a relay. It is assumed that all
nodes operate in half duplex mode without any direct link between the
communication nodes. A compress-and-forward relaying strategy using nested
lattice codes is first proposed. Then, the proposed scheme is improved by
performing a layered coding : a common layer is decoded by both receivers and a
refinement layer is recovered only by the receiver which has the best channel
conditions. The achievable rates of the new scheme are characterized and are
shown to be higher than those provided by the decode-and-forward strategy in
some regions.Comment: 27 pages, 13 figures, Submitted to IEEE Transactions on Wireless
Communications (October 2013
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