Pradeepa Ramachandra

Performance evaluation & SON aspects of vertical sectorisation in a realistic LTE network environment

The advent of Active Antenna Systems has provided new ways and features for increasing the capacity of mobile networks in order to cope with the ever increasing traffic demand. One such feature is the vertical sectorisation (VS) technique where a cell is divided into an inner and an outer sector by using a second downtilted beam from one antenna. The two sectors use the same spectrum resources but share the electrical power available. The limitation in available power per sector, raises the question whether there is gain in using VS, and if so, how much and under which circumstances. This paper presents some new numerical results on the performance gains of VS in a realistic LTE network environment, especially for the case of independent activation of the feature across cells in the network. We also present a framework for the design of a SON controller enabling the smart (de)activation of the feature based on the estimated/observed traffic distribution. The controller design follows two steps: first the functional form of the controller is derived based on analytical modelling, and then this functional form is calibrated using realistic measurements in a statistical learning fashion.

On Heterogeneous Networks Mobility Robustness

Heterogeneous network 3GPP LTE deployments are considered as a prime candidate to meet increasing demand for mobile broadband service coverage and capacity. Such deployments also need to support mobility that is as robust as in traditional macro deployments. In this paper, we analyze the handover performance in heterogeneous deployments to better understand potential behavior of automatic handover parameter adjustments. Such a Self-Organizing Network (SON) feature is commonly known as Mobility Robustness Optimization (MRO). The analyses indicate difficult challenges with handovers from low power to high power base stations, and an evolved handover procedure that improves the user experience during such times is presented. These results are key for developing an MRO algorithm for heterogeneous networks.

Self-optimisation of Vertical Sectorisation in a realistic LTE network

Vertical Sectorisation (VS) is a feature that exploits the capabilities of Active Antenna Systems (AAS) to improve service performance and network capacity, by splitting a single cell into an inner and outer sector. The attained gains primarily depend on the suitable and timely (de)activation of VS in response to the observed/estimated traffic distribution within the cell, while further gains can be achieved by properly adjusting VS parameters such as the transmit power distribution. Considering a realistic LTE (Long Term Evolution) network environment, in this paper a SON (Self Organizing Network) algorithm is proposed and evaluated, which dynamically (de)activates the VS feature and sets the transmit power split. The results show that the (de)activation of VS through a suitably tuned SON algorithm achieves significant throughput gains, while the dynamic adaptation of the transmit power distribution is mostly beneficial when operating in interference-limited environments.

On automatic establishment of relations in 5G radio networks

One of the first key self-organizing features introduced in LTE was Automatic Neighbor Relations (ANR), a function for automatically generating relations between radio network entities that is needed for many features such as active-mode mobility, load balancing and dual connectivity. Given the benefits of ANR in LTE, we foresee that procedures for relations establishment will be an important integrated part of 5G systems as well. Moreover, the new emerging technology components of 5G such as massive beamforming expand the scope of relations beyond the neighbor relations of LTE. In this paper, we give an overview of key 5G radio access components, discuss the need for different types of identifiers and relations, and comment on the impact from the ultra-lean design principle of 5G. The paper also discusses some possible procedures for automatic relation establishment in consideration of the specific 5G aspects.