  This paper presents a new virtualization method for the downlink of a
multi-cell multiple-input multiple-output (MIMO) network, to achieve service
isolation among multiple Service Providers (SPs) that share the base station
resources of an Infrastructure Provider (InP). Each SP designs a virtual
precoder for its users in each cell, as its service demand to the InP, without
the need to be aware of the existence of the other SPs or to know the channel
state information (CSI) outside the cell. The InP performs network
virtualization to meet the SPs' service demands while managing both the
inter-SP and inter-cell interference. We consider coordinated multi-cell
precoding at the InP and formulate an optimization problem to minimize a
weighted sum of signal leakage and precoding deviation, with per-cell transmit
power constraints. We propose a fully distributed semi-closed-form solution at
each cell, without any CSI exchange across cells. We further propose a
low-complexity scheme to allocate the virtual transmit power, for the InP to
regulate between interference elimination and virtual demand maximization.
Simulation results demonstrate that our precoding solution for network
virtualization substantially outperforms the traditional spectrum isolation
alternative. It can approach the performance of fully cooperative precoding
when the number of antennas is large.
