1 research outputs found
Buffer-Based Distributed LT Codes
We focus on the design of distributed Luby transform (DLT) codes for erasure
networks with multiple sources and multiple relays, communicating to a single
destination. The erasure-floor performance of DLT codes improves with the
maximum degree of the relay-degree distribution. However, for conventional DLT
codes, the maximum degree is upper-bounded by the number of sources. An
additional constraint is that the sources are required to have the same
information block length. We introduce a -bit buffer for each source-relay
link, which allows the relay to select multiple encoded bits from the same
source for the relay-encoding process; thus, the number of sources no longer
limits the maximum degree at the relay. Furthermore, the introduction of
buffers facilitates the use of different information block sizes across
sources. Based on density evolution we develop an asymptotic analytical
framework for optimization of the relay-degree distribution. We further
integrate techniques for unequal erasure protection into the optimization
framework. The proposed codes are considered for both lossless and lossy
source-relay links. Numerical examples show that there is no loss in erasure
performance for transmission over lossy source-relay links as compared to
lossless links. Additional delays, however, may occur. The design framework and
our contributions are demonstrated by a number of illustrative examples,
showing the improvements obtained by the proposed buffer-based DLT codes.Comment: 14 pages, 17 figures, submitte