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LTE Advanced: HetNet eICIC/IC

LTE Advanced Heterogeneous Networks (HetNets) use a mix of macro, pico, femto and relay base stations, effectively bringing the network closer to the user. To deliver high spectral efficiency per unit area, advanced techniques are needed to manage and control interference when low power small cells are added to macro cells in the same channel. Qualcomm has developed two LTE Advanced techniques, enhanced inter-cell interference coordination and advanced terminal receivers with interference cancellation (eICIC/IC) to provide a performance leap for heterogeneous networks in LTE.

LTE Advanced HetNets will support Range Expansion and Resource Partitioning with an eICIC software upgrade to a LTE-R8 network. Range Expansion allows more user terminals to benefit directly from low-power basestations such as picos, femtos and relays. Adaptive inter-cell interference coordination uses Almost-Blank Subframes (ABS) to provide smart resource allocation amongst interfering cells and improves inter-cell load balancing in heterogeneous networks. Advanced terminal receivers cancel interference of legacy overhead channels in ABS from interfering cells to enable full Range Expansion of low-power small cells.

The LTE Advanced eICIC feature has been standardized in 3GPP Rel. 10 while the device requirements for interference cancellation receivers have been specified in Further enhanced ICIC (FeICIC) of Rel. 11. Qualcomm Research and other 3GPP participants have been leading the standardization of HetNets features. Qualcomm Research has also built a prototype to demonstrate and test these features in OTA heterogeneous networks in San Diego.

Voice over LTE (VoLTE) allows LTE systems to deliver high-quality, high-capacity voice calls using packet switching core. The VoLTE service including features such as Transmission Time Interval (TTI) bundling can coexist with LTE HetNets using eICIC/IC. Qualcomm OTA networks in San Diego have implemented and demonstrated the coexistence operation.

For an LTE operator that needs to significantly increase network capacity, deploying LTE Advanced HetNets and using 802.11 Wi-Fi access points (APs) in unlicensed spectrum offers two complementary options to offload macro user traffic. Based on our study, with the same number of low-power nodes, pico cells offer a superior performance to Wi-Fi APs due to expanded coverage of LTE Advanced pico cells. Wi-Fi is effective in improving the user experience when a significant portion of users are located in the vicinity of hotspots.