  We consider online wireless network virtualization (WNV) in a multi-cell
multiple-input multiple output (MIMO) system with delayed feedback of channel
state information (CSI). Multiple service providers (SPs) simultaneously share
the base station resources of an infrastructure provider (InP). We aim at
minimizing the accumulated precoding deviation of the InP's actual precoder
from the SPs' virtualization demands via managing both inter-SP and inter-cell
interference, subject to both long-term and short-term per-cell transmit power
constraints. We develop an online coordinated precoding solution and show that
it provides provable performance bounds. Our precoding solution is fully
distributed at each cell, based only on delayed local CSI. Furthermore, it has
a closed-form expression with low computational complexity. Finally, simulation
results demonstrate the substantial performance gain of our precoding solution
over the current best alternative.
