Achieving multiuser diversity under hard fairness constraints

The focus of this study is an extension of [1] where the concept of multiuser diversity was introduced in the context of a single-cell multiuser channel. The primary result of this work is that using proper dynamic resource allocation strategies on Rayleigh fading channels can yield a non-negligible power boost which can be as high as 5 or 6 dB, for a moderate number of users employing a joint resource allocation policy. This gain grows logarithmically with the number of users. The results were extended in [2] where the complete fading multiuser channel capacity region was found. It was shown in [3] and [4] that similar results hold for the fading broadcast channel. The main practical issue arising from these results is fairness. Users must wait (or the basestation in the case of the broadcast channel) until their channel conditions are favourable enough to transmit. We show in this work that multiuser diversity can still be achieved in a multi-carrier system using simple orthogonal multiplexing even under the constraint that each user receives the same constant bandwidth resource at any time instant.