54 research outputs found
Analysis and Design of Binary Message-Passing Decoders
Binary message-passing decoders for low-density parity-check (LDPC) codes are
studied by using extrinsic information transfer (EXIT) charts. The channel
delivers hard or soft decisions and the variable node decoder performs all
computations in the L-value domain. A hard decision channel results in the
well-know Gallager B algorithm, and increasing the output alphabet from hard
decisions to two bits yields a gain of more than 1.0 dB in the required signal
to noise ratio when using optimized codes. The code optimization requires
adapting the mixing property of EXIT functions to the case of binary
message-passing decoders. Finally, it is shown that errors on cycles consisting
only of degree two and three variable nodes cannot be corrected and a necessary
and sufficient condition for the existence of a cycle-free subgraph is derived.Comment: 8 pages, 6 figures, submitted to the IEEE Transactions on
Communication
Delay-Exponent of Bilayer Anytime Code
In this paper, we study the design and the delay-exponent of anytime codes
over a three terminal relay network. We propose a bilayer anytime code based on
anytime spatially coupled low-density parity-check (LDPC) codes and investigate
the anytime characteristics through density evolution analysis. By using
mathematical induction technique, we find analytical expressions of the
delay-exponent for the proposed code. Through comparison, we show that the
analytical delay-exponent has a close match with the delay-exponent obtained
from numerical results.Comment: Accepted for presentation in ITW-2014. 5 Pages, 3 Figure
Multi-Way Relay Networks: Orthogonal Uplink, Source-Channel Separation and Code Design
We consider a multi-way relay network with an orthogonal uplink and
correlated sources, and we characterise reliable communication (in the usual
Shannon sense) with a single-letter expression. The characterisation is
obtained using a joint source-channel random-coding argument, which is based on
a combination of Wyner et al.'s "Cascaded Slepian-Wolf Source Coding" and
Tuncel's "Slepian-Wolf Coding over Broadcast Channels". We prove a separation
theorem for the special case of two nodes; that is, we show that a modular code
architecture with separate source and channel coding functions is
(asymptotically) optimal. Finally, we propose a practical coding scheme based
on low-density parity-check codes, and we analyse its performance using
multi-edge density evolution.Comment: Authors' final version (accepted and to appear in IEEE Transactions
on Communications
Finite Length Analysis of LDPC Codes
In this paper, we study the performance of finite-length LDPC codes in the
waterfall region. We propose an algorithm to predict the error performance of
finite-length LDPC codes over various binary memoryless channels. Through
numerical results, we find that our technique gives better performance
prediction compared to existing techniques.Comment: Submitted to WCNC 201
The Three-User Finite-Field Multi-Way Relay Channel with Correlated Sources
This paper studies the three-user finite-field multi-way relay channel, where
the users exchange messages via a relay. The messages are arbitrarily
correlated, and the finite-field channel is linear and is subject to additive
noise of arbitrary distribution. The problem is to determine the minimum
achievable source-channel rate, defined as channel uses per source symbol
needed for reliable communication. We combine Slepian-Wolf source coding and
functional-decode-forward channel coding to obtain the solution for two classes
of source and channel combinations. Furthermore, for correlated sources that
have their common information equal their mutual information, we propose a new
coding scheme to achieve the minimum source-channel rate.Comment: Author's final version (accepted and to appear in IEEE Transactions
on Communications
- …