Multiuser switched diversity transmission

In this paper, a set of multiuser access schemes are proposed based on switched diversity algorithms originally devised to select between antennas in a spatial diversity system. Instead of relying on feedback from all the users in a multiuser communication system to identify the best user on a time-slot basis (having the best channel quality among all the users), the proposed multiuser access schemes are performed in a sequential manner, looking not for the best user but for an acceptable user. A user qualifies as an acceptable user and is selected by the base station when the reported channel quality is above a predefined switching threshold. The proposed schemes result in a lower average spectral efficiency (ASE) than using the optimal selective diversity scheme, but a gain is obtained by reducing the feedback load. Numerical results that quantify the trade-off between ASE and average feedback load (AFL) are presented, showing that the AFL can be reduced significantly compared to the optimal selective diversity scheme without experiencing a big performance loss. In addition, it is argued that the proposed multiuser access schemes can be quite attractive also from a fairness perspective.