Realization and capacity analysis of cooperative communications based on multiplexing

Cooperative communication (CC) techniques, which form virtual multiple input multiple output (MIMO) systems through cooperation among users, have been prevailing in current academic research. Two scenarios that have been mostly considered are one source to one destination with help from a classic relay node and two sources to one destination with cooperation among sources, i.e. cooperation for multiple access channels. In either case, single antenna is employed at each node. In this paper, I propose to realize cooperation based on multiplexing for a broadcast channel where there is one source equipped with multiple antennas and two destinations with single antenna. One of the destinations experiencing better channels helps the other destination under worse channel conditions by serving as a relay. Such a channel is referred to as a multiple input single output (MISO) cooperative broadcast channel (CBC). Further, I consider the capacity analysis for the MISO CBC where additive white Gaussian noise (AWGN) presents (MISO AWGN CBC), which is not easy because MISO AWGN channel, as a vector Gaussian channel, is generally not degraded. I derive an outer bound on the capacity region of MISO AWGN CBC to provide insights into its information transmission limit.