Due to the intrinsic characteristics of WCDMA and the great number of services offered by UMTS, its radio channel is much more dynamic compared with GERAN systems. The traffic fluctuations and users mobility can cause the impairment of the network performance and of the quality of service (QoS) in certain cells. In the worst case a significant degradation of the QoS may be observed and as a result the operator defined targets are not met.
Nowadays UMTS operators have fixed, and usually uniform, settings for their network parameters. This static configuration is not able to adapt automatically to the changes that occur in the network. A fixed parameter setting then gives a non optimal solution for the network optimization process and thus the utilization of the radio interface is not maximized. The goal of the automated tuning is to adjust dynamically these parameters in a continuous way without human intervention, which is only required in definition of the reference QoS.
The current PFC aims at validating the feasibility of automated optimization of certain UMTS RRM parameters. The main tasks to be developed by the students are:
- Simulator developement (Matlab programmed). A basic static Montecarlo simulator is available as a reference.
- Study of UMTS handover algorithm and study of potential parameters to be automatically tuned.
- Proposal of algorithm to tune the previously selected parameters, and evaluation of achieved gains.
- Study of UMTS CAC algorithm and study of potential parameters to be automatically tuned. Development of first and basic ideas to propose tuning algorithm.The present PFC is located inside the framework of the UMTS networks, and more specifically
in the development of new Radio Resource Management (RRM) algorithms capable
to maximize the capacity and the performance of the network. In this sense a powerful
simulation tool capable to analyze in depth the behavior of the UMTS network under different
simulation scenarios has been developed. It has been focused in the study of the
main algorithms that manage the allocation of radio resources in UMTS networks: Power
Control (PC), Admission Control (AC) and Soft/Softer Handover (SHO).
The problem observed in classical SHO strategies is the rigidity of the mechanism, which
cannot adapt to variations in the traffic patterns. The improvements on SHO procedures
are based on dynamic automated tuning of SHO parameters. A three blocks based functional
architecture is described to adapt parameters to service mix dynamics and overcome
capacity problems. Several tests have been done over different traffic situations in order
to demonstrate the feasibility of the Auto-Tuning System (ATS). The results obtained show
a considerable increment in the network capacity. In this sense ATS is considered as an
effective pre-congestion-control strategy.
Referring now to AC strategies, it is necessary to underline that three new AC algorithms
have been implemented: Dynamic AC, Complete Partitioning AC (CP-AC) and Complete
Sharing AC (CS-AC) strategies have been developed with the same goal, enhance the
capacity of the network. Dynamic AC was proposed to provide flexibility to the current AC
algorithm. This strategy is based on the ATS philosophy where a dynamic AC threshold
is fixed to the optimum threshold in real time according to the current service mix. On
the other hand, CS-AC and CP-AC are complex strategies based on static algorithms
where fixed thresholds or load margins were applied in order to note their advantages and
drawbacks depending on the users distribution, uniform or mostly close to the cell edge.
As a result of this project a scientific publication inside the context of COST european
projects has been carried out. In special, is about the COST 2100 ”Pervasive Mobile &
Ambient Wireless Communications” and the title of the publication is ”Automatic Tuning of
Soft Handover Parameters in UMTS Networks”. The paper was presented in the meeting
number 3, held in Duisburg (Germany) between 10th and 12th of September 2007
