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But the quality of service as perceived by real 3G customers will actually be the quality of their own call (from the start to the end). Therefore, it is difficult to plan 3G networks for QoS with Monte-Carlo-only based simulators. The DS-CDMA system is intrinsically dynamic, through mechanisms like power control, addition of new calls, soft handover decisions, etc.. Any event on the physical radio layer has an immediate impact on all the active links in the system. In Monte-Carlo simulators, for a given position of a mobile station, the optimum content of its active set may not be achieved in practice, due to delays in the RRM loops, the asymmetry in handover windows, or the unavailability of radio ressource due to poor code packing in OVSF trees, or poor resource packing in the Node B. As a result, mobiles are sometimes connected to worse cells than expected, then best cells get more interfered. For all these reasons, Monte-Carlo simulators are quite optimistic.
Dynamo brings a new methodology for true QoS planning Facing the highest challenges introduced with 3G systems, Mitsubishi Electric developed the concept of Dynamo, which simulates the fully dynamic behavior of the physical radio layer of 3G mobile networks. Dynamo introduces correlation between successive snapshots of the system. This correlation enables a true assessment of the observed quality of service along the lifetime of each call. Dynamo simulates dynamic generation of new calls, the evolution of RRM resource mapping, and most of all, the dynamic nature of the co-channel interference. Dynamo can thus track the quality of each call with a surrounding interference fluctuating during the lifetime of a call. In Dynamo, no biasing assumption is made on this fluctuation. It is directly due to dynamic events, such as user mobility, addition of new calls, soft handover decision, power control, speech codec activation, … Moreover, Dynamo simulates any kind of environment, mixing a variety of different services, a variety of user mobility models, and the possibility to simulate 3G networks deployed over existing site databases. Dynamo : Multi Dynamic 3G System Level Simulator (W-CDMA, TS-CDMA) Features
One single simulation can support any kind of scenario combining various service types (packet, circuit, voice). Assignment of the call on a specific frequency layer Mapping of the call on multicode/multislot entities Mapping of calls on modular CE and CM in the Node B.
The evolution of the received interference level for each mobile station depends on the traffic situation and on the radio propagation for the surrounding mobile stations.
The QoS considered by Dynamo is understood as quality integrated along the whole duration of the calls. A good quality call is a call not blocked, non dropped and which instantaneous quality has been good during a predefined ratio of the call duration. The instantaneous quality is computed by observing the Eb/Io levels of uplink and downlink after power control, and by comparing them with those of the target Eb/Io levels corresponding to the target quality of the service in a given environment.
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