4 research outputs found
A New Coding Paradigm for the Primitive Relay Channel
We consider the primitive relay channel, where the source sends a message to
the relay and to the destination, and the relay helps the communication by
transmitting an additional message to the destination via a separate channel.
Two well-known coding techniques have been introduced for this setting:
decode-and-forward and compress-and-forward. In decode-and-forward, the relay
completely decodes the message and sends some information to the destination;
in compress-and-forward, the relay does not decode, and it sends a compressed
version of the received signal to the destination using Wyner-Ziv coding. In
this paper, we present a novel coding paradigm that provides an improved
achievable rate for the primitive relay channel. The idea is to combine
compress-and-forward and decode-and-forward via a chaining construction. We
transmit over pairs of blocks: in the first block, we use compress-and-forward;
and in the second block, we use decode-and-forward. More specifically, in the
first block, the relay does not decode, it compresses the received signal via
Wyner-Ziv, and it sends only part of the compression to the destination. In the
second block, the relay completely decodes the message, it sends some
information to the destination, and it also sends the remaining part of the
compression coming from the first block. By doing so, we are able to strictly
outperform both compress-and-forward and decode-and-forward. Note that the
proposed coding scheme can be implemented with polar codes. As such, it has the
typical attractive properties of polar coding schemes, namely, quasi-linear
encoding and decoding complexity, and error probability that decays at
super-polynomial speed. As a running example, we take into account the special
case of the erasure relay channel, and we provide a comparison between the
rates achievable by our proposed scheme and the existing upper and lower
bounds.Comment: 10 pages, 4 figures, in Proc. of ISIT'18 (short version) and in
Algorithms (full version