Absfrucf --A simulator (GSMSIM) of the digital cellular radiotelephone network, GSM, is described. The simulator is used as a tool for network design. The GSMSIM supplies: the load of the cells, the frequency and length of the calls in the cells, the number and place of the handovers and their reasons, and also power control parameters. The GSMSIM's ability to simulate the GSM radio telephone network gave us an excellent chance to study the system performance as the functions of the BSS parameter sets.
I.Introducto i nThe Global System for Mobile Communication (GSM), digital cellular radiotelephone system, is just under introduction in sevcral European countries. To gct thc radiotclcphone network in operation, scvcral base stations should be installed. Tremendous effort has been spcnt in the design of base station installations all over Europe. In some aspects, circuits-based test systems or --cvcn more --prototype systems could help the designer. On the othcr hand there are existing software design tools deveiopcd for dcsigning radio systems (e.g., NMT (Nordic Mobile Telephone)), which are capable of calculating thc covcrage area of radio transmitters, that arc applicable and uscful to this problem too. For cxamplc TELECOM FINLAND, has dcvcloped the MONICA program package [ l ] for riidio nctwork planning and data managemcnt. It offcrs il widc range of services and a databasc for ccllular network planning. MONICA'S database holds thc raslcr map oC the planning area, and can apply differcnt sophisticatcd radio wave propagation models.For thc tools mcntioncd abovc thcrc arc fcaturcs dependent on a large number of indcpendcnt uscrs' actions that arc oul of scope. Howcvcr, thesc characteristics arc thc most complicated ones. Onc major part of GSM supcriority over the prcscnt generation of the ccllular phonc systcm comes from its flexibility for fulfilling the changing dcmand of users. The BSS's (Base Station System) paramctcrs, which determine how telephone calls arc handled while thc customers are moving, are dependent on the specific location and the surroundings of the BSS. Thc numbcr of these parameters is around 100 contradictory, with fcw parameters for the present generation of radio telephone networks [2]. The goal is to find a parameter set, that the GSM system can work with, moreover can optimally work. Ovcr and above that, the GSM system givcs the possibility to the PLMN (Public Land Mobile Network) operator to follow changing customer needs, in time by controlling thc transmitted power, changing the handover (HO) parameters, thc ccll size and by dynamic channel allocation. All of these arc rcalizcd with variation of the BSS's parameter set. It is csscntial for the PLMN operator to offer a service with the smallest number of call failures, good quality and the widest availability. The only way to support these efforts of the PLMN operator is to write a computer simulator of the GSM system.On thc basis of these needs, we have developed GSMSIM, a network simulator for GSM digital radio tclcphone systcm.
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