Torsten Dudda

Capacity of cellular networks deployed in TV White Space

This paper investigates how suitable TV White Space (TVWS) is for use by cellular networks. Unlike in licensed bands, transmit power in TVWS is limited and considerable interference from TV towers exists. This suggests that evaluating TVWS only in terms of available bandwidth can be misleading, since performance of wireless networks in TVWS is likely lower than in the same amount of dedicated spectrum. We quantify TVWS at the example of Germany, using the European methodology developed in CEPT ECC SE 43. In the second step, we determine the performance of a cellular network operating in TVWS using a calibrated multi-cell and multi-user system level simulation tool. This way we also consider interference between TVWS users, which in previous TVWS studies has not been investigated in detail. Not all locally available TV channels are equally useful. We thus compare different channel selection algorithms a TVWS operator could apply to select from the set of available TVWS channels. We found that while the available spectrum for TVWS usage is in theory quite high, its actual utility strongly depends on the channel selection method and the requirements it is based on. Due to the high interference from TV towers, cellular networks based on frequency re-use one (like LTE) have difficulties finding channels that allow good performance at the cell edge. The inner part of a cell can however considerably benefit from TVWS. This indicates that for cellular networks TVWS is primarily suitable for traffic offloading and spotty coverage rather than for building large contiguous coverage networks.

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.

LTE-WLAN aggregation (LWA) in 3GPP Release 13 & Release 14

Integrating different radio access technologies (RATs) is one effective method to meet the demand to provide ever increasing data rates to the users. For integrating LTE and WLAN in particular, the purpose is to enhance the operators control of when the UE uses WLAN. Another aim, in addition to better network control on which RAT is used, is the possible data aggregation which enables simultaneous utilization of both resources. In this paper, we present LTE-WLAN Aggregation (LWA) as specified in 3GPP and compare it to the LTE-WLAN Radio Level Integration with IPsec tunnel (LWIP), also specified in 3GPP. In addition, we provide simulation results comparing the schemes in an example scenario.