  In this paper, we investigate the performance of a three-node dual-hop
cognitive radio network (CRN) with a half-duplex (HD) decode-and-forward (DF)
buffer-aided relay. We derive expressions for the average rate and symbol error
rate (SER) performance of an adaptive link selection based channel-aware
buffer-aided relay (CABR) scheme that imposes peak-power and peak-interference
constraints on the secondary nodes, and compare them with those of conventional
non-buffer-aided relay (CNBR) and conventional buffer-aided relay (CBR) schemes
for a delay-tolerant system. For finite-delay systems, we analyze the
performance of a modified threshold-based scheme for fixed-rate transmission,
and demonstrate that use of a last-in-first-out buffer is advantageous in some
situations. We bring out the trade-offs between delay, throughput and SER.
Computer simulation results are presented to demonstrate accuracy of the
derived expressions.
