1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June, 2007 An automatic Procedure for Neighbor Cell List Definition in Cellular Networks Flavio Parodi, Juan Li, Jose Pradas – Helsinki University of Technology Mikko Kylväjä, Gordon Alford – Nokia Siemens Networks
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1st IEEE WoWMoM Workshop on Autonomic Wireless AccesS 2007 (IWAS07) - 18 June, 2007 An automatic Procedure for Neighbor Cell List Definition in Cellular.
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• In future years, network operators will have to face an increasing number of technological challenges:
• The simultaneous operation of different technologies (GSM, (E)GPRS, WCDMA, Next Generation Mobile Network)
• The need to provide a widespread coverage with high bandwidth requirements (i.e. Home base stations)
• A tremendous increase in the number of operated network nodes
• A diversified range of services, potentially requiring seamless connectivity
• Furthermore, developed countries will be characterized by an almost saturated market, with strong competition among operators forcing a reduction in tariffs
• In such a context, management systems are a potential bottleneck for a successful network operation
• The reduction of operating expenditures (OPEX) and management complexity are vital for network operators in the years to come
• More efficient and autonomous management systems are crucial to achieve such targets
• The application of autonomic self-management functionalities would allow for
• A reduced need for human control and intervention• The capability of adaptation in presence of new nodes (self-configuration)• The possibility of increasing performances, by optimizing network
parameters (self-optimization)• A more efficient and well-timed report, diagnosing and fixing of
malfunctions (self-testing and self-healing)
• At present, 3GPP LTE standards define the support for the the self-configuration and self-optimization functionalities [1]:
• The self-configuration takes place in the pre-operational state• The self-optimization takes place during the operational state
NCL configuration: coverage area approximation• In case the NCL is calculated during the self-configuration process, the
coverage areas of all potential neighbors are considered
• Two cells are identified as neighbors if their coverage areas overlap
• Depending on the available amount of information, the coverage areas can be approximated in different ways, each corresponding to a specific class of algorithms:
• Class 1 only geographical information available (cell coordinates)
• Class 2 coordinates and antenna parameters available
• Class 3 coordinates, antenna parameters and power values available
Coverage Area Approximation: class 2 algorithms• The detection of overlap is carried out by checking if the coverage
area perimeters of two cells intersect
• Circle approximation: the perimeters intersectif the sum of the radiuses is less than the distance between the centers
• Sector approximation: the following intersectionsare checked: between sector sides, between sector side and circumference arc, between circumference arcs
Coverage Area Approximation: class 3 algorithms• The availability of the radiated power value allows to fix the maximum
coverage range r, i.e. the size of the coverage areas• On the coverage area border, the following equation holds:
where Ptx indicates the radiated power, G the antenna gain, AF the antenna factor, LP the path loss, SMT the sensitivity of the mobile terminal
• Fixing the mobile terminal sensitivity, the path loss value at the perimeter of the coverage area can be calculated
• The Okumura-Hata formula is used to model the link loss• Once the path loss value is known, the maximum range is calculated
solving the O-H formula with respect to r [2]:
• As far as the coverage area shape is concerned, the same methods of approximation as algorithms 2 are used (and, therefore, the same rules for overlap detection apply)
• The NCL configuration algorithm provides the NCL for a new cell• In the autonomic framework defined in [3], the presented algorithm is
used to determine the neighbors of a cell once it joins the network
• The calculated NCL may include cells which are not actual neighbors• The best NCL is the one made up by only the actual neighbors of the new
cell
• The goal of the NCL definition algorithms is not to find the best NCL, as the following optimization phase should take care of dropping the neighbors with low HO share
• If the initial NCL includes all the actual neighbors, the best NCL can be found simply by pruning the unused NCL entries [3]
• The required computational load depends on the type of approximation for the coverage area
[1] 3GPP TS 36.300 v8.0.0, Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2
[2] J. Laiho, A. Wacker, T. Novosad, editors. Radio Network Planning and Optimisation for UMTS, 1st ed., John Wiley & Sons, 2002.
[3] D. Soldani, G. Alford, F. Parodi, M. Kylväjä. An Autonomic Framework for Self-optimizing Next Generation Mobile Netwoks. IEEE, WoWMoM IWAS, Helsinki, Finland, June 2007.
[4] R.Guerzoni, I. Ore, K.Valkealahti, D.Soldani. Automatic Neighbor Cell List Optimization for UTRA FDD Networks: Theoretical approach and Experimental Validation, IWS/WPMC, Aalborg, Denmark, 2005
[5] 3GPP TR 25.912 v7.0.0, Feasibility study for evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN)
[6] 3GPP TR 25.814 v7.0.0, Physical layer aspects for evolved Universal Terrestrial Radio Access (UTRA)
[7] 3GPP TR 23.822 v1.2.3, 3GPP System Architecture Evolution: Report on Technical Options and conclusions