Cooperation in a half-duplex Gaussian diamond relay channel

A half-duplex relay channel consisting of two relays in a diamond topology is studied. In contrast to full-duplex systems, it is shown that time should be optimally allocated among different states. In contrast to the classical three-node relay channel, it is shown that spatial reuse can be utilized to allow communication without interference. Both achievable rate and upper bound on capacity are studied. Several communication schemes such as multihop with spatial reuse, scale-forward, broadcast-multiaccess with common message, compress-forward, as well as hybrid ones are characterized, some of which are novel. It is also shown that simple multihop with spatial reuse achieves the capacity of certain symmetric diamond channels.