  In this paper, we present bandwidth efficient retransmission method employong
selective retransmission approach at modulation layer under orthogonal
frequency division multiplexing (OFDM) signaling. Our proposed cross-layer
design embeds a selective retransmission sublayer in physical layer (PHY) that
targets retransmission of information symbols transmitted over poor quality
OFDM sub-carriers. Most of the times, few errors in decoded bit stream result
in packet failure at medium access control (MAC) layer. The unnecessary
retransmission of good quality information symbols of a failed packet has
detrimental effect on overall throughput of transceiver. We propose a
cross-layer Chase combining with selective retransmission (CCSR) method by
blending Chase combining at MAC layer and selective retransmission in PHY. The
selective retransmission in PHY targets the poor quality information symbols
prior to decoding, which results into lower hybrid automatic repeat reQuest
(HARQ) retransmissions at MAC layer. We also present tight bit-error rate (BER)
upper bound and tight throughput lower bound for CCSR method. In order to
maximize throughput of the proposed method, we formulate optimization problem
with respect to the amount of information to be retransmitted in selective
retransmission. The simulation results demonstrate significant throughput gain
of the proposed CCSR method as compared to conventional Chase combining method.
