%0 Journal Article %T Protocols and Performance Limits for Half-Duplex Relay Networks %A Peter Rost %A Gerhard Fettweis %J Mathematics %D 2009 %I arXiv %X In this paper, protocols for the half-duplex relay channel are introduced and performance limits are analyzed. Relay nodes underly an orthogonality constraint, which prohibits simultaneous receiving and transmitting on the same time-frequency resource. Based upon this practical consideration, different protocols are discussed and evaluated using a Gaussian system model. For the considered scenarios compress-and-forward based protocols dominate for a wide range of parameters decode-and-forward protocols. In this paper, a protocol with one compress-and-forward and one decode-and-forward based relay is introduced. Just as the cut-set bound, which operates in a mode where relays transmit alternately, both relays support each other. Furthermore, it is shown that in practical systems a random channel access provides only marginal performance gains if any. %U http://arxiv.org/abs/0907.2309v2