QoS of Mobile Broadband Users in Heterogeneous Networks

Initial deployments of LTE networks are based on so called homogeneous networks consisting of only Macro base stations for basic coverage. As the number of users increases, especially in densely populated areas, the macro base stations are believed to lack sufficient capacity to bear the load of traffic increase for mobile broadband users. To overcome this problem the macro network will be complemented with low power nodes, such as Pico and Femto eNBs, will improve the system capacity.This Master thesis study comprises an investigation on how quality of service can be maintained for video telephony users in heterogeneous networks when considering different configurations, user patterns, user distributions, and user loads.Three heterogeneous configurations specified by 3GPP were compared to a reference case; a pure macro network. Firstly, the simulation results show that when introducing low power nodes (LPN), the video telephony capacity increases with the increase in the number of users clustered around the hot-spots for all configurations. Also, in the heterogeneous network users in the macro cells experience slightly lower interference when more users are absorbed by the low power nodes. The video telephony tail latency experiences a sharp increase for all configurations. The reason for this is that the worst cells become congested and the users will compete for the available resources. It is observed that the tail latency in uplink, already at low load, is higher than in downlink due to that the scheduler is located at eNodeB.Secondly, a scenario investigating the gain of Low power nodes range extension showed that signal to interference and noise ratio (SINR) problems arise if the range of the low power nodes is extended, however the system as a whole observes increased throughput. The main reasons are macro layer offloading and reduced interference created by the macro layer. Finally, a scenario investigating the addition of multiple Low power nodes cells with range extension showed that video telephony capacity will be further improved when multiple Low power nodes are combined with range-extension.The combination of range extension and multiple low power nodes (LPN) will reduce the interference originating from the macro cells as a result of the offloading of the macro cells. This since more users will be served by the LPN cells. As a result, the macro physical resource block utilization will be reduced. It was shown also that the throughput of the LPN cells is not related to the number of deployed LPNs, but it depends on the size of the LPN cell increase of RSRP offset.Validerat; 20120118 (anonymous