Efficient small cell discovery.
Small cells operate on licensed spectrum and provide an excellent user experience by providing better coverage for voice and very high data throughputs. When a mobile camping on a macro-only frequency approaches a small cell, it is essential that the mobile searches and reselects the small cell in order to facilitate efficient offloading of macro traffic. However, in good macrocell coverage, the mobile may not perform an inter-frequency search of other cells thus, not triggering the reselection procedure which may cause the user to not be able to discover and camp on its own small cell. The objective of an efficient discovery scheme is not only to find the femtocells quickly but also to minimize any potential impact on the battery life of all the mobile devices served both by macro and femtocells.
The UltraSON™ Mobility Management Suite provides the following features:
Idle Mode Femto Discovery
This feature provides a fast and reliable discovery via beacon transmission with minimal impact on macro mobile performance.
This feature provides a reliable method to handover from macro to femto in active mode via beacon and target femtocell disambiguation.
This feature implements dual femto transmit antennas to reduce the number of handovers and improve voice quality especially in indoor environments.
To address the femtocell discovery issue, an innovative approach based on cell-reselection-beacons is proposed in which the femtocell transmits a beacon on macro–only frequencies. The beacon is designed to trigger mobile device to search the small cell carrier and reselect to a small cell.
Further, beacon transmission is used to facilitate inter-frequency hand-in of macro users to small cells in active mode. Beacons solve key challenges of active hand-in namely (1) the absence of a reliable inter-frequency hand-in trigger and (2) the presence of PSC confusion arising from PSC reuse among small cells.
The Small Cells R&D group has performed extensive research in the area of femto mobility management, and conducted numerous simulations and lab experiments to demonstrate the effectiveness of these innovations in addressing the femtocell discovery issue in both idle and active modes.
As the density of NSCs can be very high and network configuration and topology may change rapidly, it is essential to have UltraSON (add link to UltraSON subpage) features to ensure robust operations of the small cells.