On the capacity of the half-duplex diamond channel
Hossein Bagheri, Seyed Abolfazl Motahari, Amir Keyvan Khandani · 2010
In this paper, a dual-hop communication system composed of a source S and a destination D connected through two non-interfering half-duplex relays, R1and R2, is considered. In the literature of Information Theory, this configuration is known as the diamond channel. In this setup, four transmission modes are present, namely: 1) S transmits, and R1and R2listen (broadcast mode), 2) S transmits, R1listens, and simultaneously, R2transmits and D listens. 3) S transmits, R2listens, and simultaneously, R1transmits and D listens. 4) R1, R2transmit, and D listens (multiple-access mode). Assuming a constant power constraint for all transmitters, a parameter Δ is defined, which captures some important features of the channel. It is proven that for Δ=0 the capacity of the channel can be attained by successive relaying, i.e, using modes 2 and 3 defined above in a successive manner. This strategy may have an infinite gap from the capacity of the channel when Δ≠0. To achieve rates as close as 0.71 bits to the capacity, it is shown that the cases of Δ >0 and Δ0, respectively. Furthermore, it is established that under average power constraints the aforementioned strategies achieve rates as close as 3.6 bits to the capacity of the channel.