Dense interference-limited wireless networks can rely coordinated multipoint transmission (such as Network MIMO) as a way to improve on spectral efficiency. Unfortunately, Network MIMO requires global channel state information (CSI) at all transmitters, hence places stringent requirements on backhaul rate and even more on latency. As a solution, this paper investigates an emerging design philosophy for CSI that exploits the broadcast nature of wireless which is well suited to dense networks. In our design, feedback is broadcast from each terminal and decoded opportunistically by any overhearing base station which in turn must design opportunistic interferencecancelling precoders. The corresponding precoder design is shown to be equivalent to a decentralized decision problem whose general solution is challenging, yet for which heuristic schemes can be derived. The obtained algorithms are able to capitalize on the opportunistic feedback without the need for global CSI sharing.
['Sandeep Kottath', 'David Gesbert', 'Eric Hardouin']
Opportunistic feedback mechanisms for decentralized Network MIMO systems