Codes for half duplex relay channels

In this paper, we study LDPC code constructions for the half-duplex relay channels. Our work is motivated by the observation that half-duplex relaying - where the relay cannot simultaneously transmit and receive in the same band - yields substantially higher rate than both direct and two-hop communication with the same average power constraint. The profile optimization technique and the resulting LDPC codes prove to be very effective in fading environments. The performance thresholds determined using Gaussian approximation are extremely close to theoretical limits.