  Block-fading (BF) channel, also known as slow-fading channel, is a type of
simple and practical channel model that can characterize the primary feature of
a number of wireless-communication applications with low to moderate mobility.
Although the BF channel has received significant research attention in the past
twenty years, designing low-complexity outage-limit-approaching
error-correction codes (ECCs) is still a challenging issue. For this reason, a
novel family of protograph low-density parity-check (LDPC) codes, called
root-protograph (RP) LDPC codes, has been conceived recently. The RP codes can
not only realize linear-complexity encoding and high-speed decoding with the
help of a quasi-cyclic (QC) structure, but also achieve near-outage-limit
performance in a variety of BF scenarios. In this article, we briefly review
the design guidelines of such protograph codes with the aim of inspiring
further research activities in this area.
