However, there is a lack of capacity solutions for the outdoor environment that can also support good mobility and connectivity. Thus, we propose a macro-assisted small cell, called the Phantom cell, as a capacity solution that offers good mobility support while capitalizing on the existing LTE network. In the Phantom cell solution, the control (C)-plane/user data (U)-plane are split as shown in Fig. 5. The C-plane of UE in small cells is provided by a macrocell in a lower frequency band, while for UE in macrocells both the C-plane and U-plane are provided by the serving macrocell, the same as in a conventional system. On the other hand, the U-plane of UE in small cells is provided by a small cell using a higher frequency band. Hence, these macroassisted small cells are called Phantom cells, as they are intended to transmit UE-specific signals only, and the radio resource control (RRC) connection procedures between the UE and a Phantom cell, such as channel establishment and release, are managed by the macrocell. The Phantom cells are not conventional cells in the sense that they are not configured with cell-specific signals and channels, that is, primary/secondary synchronization signals (PSSs/SSSs), cell-specific reference signals (CRSs), master information block and system information blocks (MIB/SIBs), and so on. Their visibility to the UE relies on macrocell signaling. The Phantom cell solution comes with a range of benefits. One important benefit of macro assistance of small cells is that control signaling due to frequent handover between small cells and macrocell and among small cells can be significantly reduced, and connectivity can be maintained even when using small cells and higher frequency bands. In addition, by applying the new carrier type (NCT) that contains no or reduced legacy cell-specific signals, the Phantom cell is able to provide further benefits such as efficient energy savings, lower interference transmissions (and thus higher spectrum efficiency), and reduction in cell planning efforts for dense small cell deployments since Phantom cells do not rely on legacy cell-specific signals.