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1.00E-00 1.00E-01 1.00E-02 case I case II case III 1.00E-03 1.00E-04 case IV case V - new case V - handover 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Figure 17 Space element blocking probabilities for mobile stations of class 3 in element [4,2,1]. The different cases are indicated. In case V, new calls and handover calls will experience different blocking/time-out as queuing is allowed 118 Abbreviations ADC American Digital Communications system AMPS Advanced Mobile Phone System CDMA Code Division Multiple Access CT Cordless Telephone DECT Digital European Cordless Telecommunications ETE Equivalent Telephone Erlang ETSI European Telecommunications Standards Institute FDMA Frequency Division Multiple Access FPLMTS Future Public Land Mobile Telecommunication Systems GSM Global System for Mobile communications HIPERLAN High Performance LAN IN Intelligent Network ITU International Telecommunication Union JDC Japan Digital Communications system LAN Local Area Network MAN Metropolitan Area Network MT Mobile Termination ned negative exponentially distributed NMT Nordic Mobile Telephone PABX Private Automatic Branch Exchange PCS Personal Communication System SIM Subscriber Identity Module SMG Special Mobile Group TACS Total Access Communications System TDMA Time Division Multiple Access TGMS Third Generation Mobile Systems UMTS Universal Mobile Telecommunications System References 1 Andermo, P G, Larsson, G. Code Division Testbed, CODIT. I: 2nd international conference on universal personal communications, Ottawa, Canada. 12 – 15 Oct. 1993, 397–401. 2 Baier, A. Multi-Rate DS-CDMA : a promising access technique for thirdgeneration mobile radio systems. I: 4th international symposium on personal, indoor and mobile radio communications, Yokohama, Japan. 8 – 11 Sep. 1993, 114–118. 3 Calhoun, G. Digital cellular radio. Artech House, USA, 1988. 4 Grillo, D et al. A simulation testbed for the analysis of short-term adaption mechanisms in the ATDMA system. I: Mobile and personal communications : IEE conference publication, 387, 1993, 216–220. 5 Goodman, D J. Trends in cellular and cordless communications. IEEE communication magazine, June 1991, 31–40. 6 Guèrin, R A. Channel occupancy time distribution in a cellular radio system. IEEE transactions on vehicular techn., VT-35, 3, 1987, 8999. 7 Jensen, T, Myskja, A, Larsen, E. Performance of dynamic capacity allocation in future wireless communication systems. Wireless computer networks (WCN-94). The Hague, The Netherlands, 21 – 23 Sep. 1994, 1014–1018. 8 Kuehn. P J. Approximate analysis of general queuing networks by decomposition. IEEE transactions on communications. COM-27, 1, 1979, 113–126. 9 Nanda, S, Dravida, S, Samadi, B. Handoff management and performance for wireless access using metropolitan area networks. I: 8th ITC Specialist Seminar on UPT, Santa Margherita Ligure, Italy, 1992, 191–199. 10 Nanda, S. Teletraffic models for urban and suburban microcells: cell sizes and handoff rates. I: 8th ITC Specialist Seminar on UPT, Santa Margherita Ligure, Italy, 1992, 251–260. 11 Peritsky, M M. Traffic engineering of combined mobile telephone and dispatch systems. IEEE transactions on vehicular techn., VT-22, 4. Nov. 1973, 223–225. 12 Samadi, B, Wong, W S. Optimisation techniques for location area partitioning. I: 8th ITC Specialist Seminar on UPT, Santa Margherita Ligure, Italy, 12 – 14 Oct. 1992, 141–147.
Analysis of external traffic at UNIT/SINTEF’s MD110 telephone exchange BY BONING FENG AND ARNE MYSKJA 1 Introduction Since the 1950s three generations of automatic telephone exchanges have been installed at the University of Trondheim (UNIT): 1 A main exchange of type AGF (delivered by Ericsson), electromechanical type, together with 17 smaller exchanges geographically distributed both in and outside the main campus area. The exchanges covered UNIT and the research institute SINTEF, and was in service until May 1977. 2 A Metaconta 10R exchange (delivered by LMT Paris), a computerised system with mechanical contacts. It covered UNIT and SINTEF except some remote units. From 1982 the Regional Hospital of Trondheim (RiT) was also connected to the same exchange. This exchange was in service from May 1977 to January 1990. 3 In January 1990 a new telephone exchange, MD110 (delivered by Ericsson) was installed at UNIT/SINTEF. The exchange is fully electronic, digital, and distributed. It consists of 36 switching units (LIMs) on 16 different sites which are connected by a star network with altogether 54 internal 2 Mb/s leased circuits. The new exchange covers all the units of UNIT and SINTEF, but not RiT. This paper presents some results from the traffic analysis at the new exchange. Due to the limitations of the registration functions implemented in the MD110 it is not possible to make detailed studies of the incoming traffic. Another type of registration mechanism which MD110 lacks, is the possibility to register the distribution of the internal traffic. Therefore our study is focused on direction-based analysis of outgoing external traffic at the telephone exchange. The results presented here cover - number of calls - traffic volume, and - duration of calls. The study includes traffic profiles of 24 hour and full week periods, and how they are distributed among the different service types and charging groups. We also look at the number of calls and the traffic to the other universities in Norway. The number of incoming call attempts was also registered in order to get an indication of the relation between incoming and outgoing calls. In addition to averages, distributions are also included. Histograms are given for some distributions. In most cases mean, standard deviation and coefficient of variation are calculated. 2 Traffic observations 2.1 Overview of the telephone exchange at UNIT/SINTEF At the time of observation the system consisted of the following parts: - 36 LIMs - 54 leased circuits, each with thirty 64 kb/s channels - 2 group selectors in load-sharing mode - 7 two-way ISDN primary access with a total of 210 channels - 2 outgoing PCM groups with a total of 60 channels - 40 outgoing analogue reserve lines - 6500 extensions. 2.2 The data registration system Traffic observations have been undertaken on all three generations of telephone exchanges: - on AGF exchange by analysis of the charging data stored on magnetic tapes, collected by a charging system developed by NTH (The Norwegian Institute of Technology) [1] - on Metaconta 10R by analysis of the automatic registrations made by the system, and by corresponding analysis of the charging data [2, 3, 4] - on MD110 by data registered by the supporting system TELMAX, and by analysis of the charging data [6]. Despite the limitations mentioned above, the traffic registration in MD110 is still quite extensive, and they are made available through the supporting system TEL- MAX. Combined with the charging data generated by TELMAX, the data sets for the following types of analysis are available: - number of call attempts, traffic intensity and volume at all server groups, internal and external trunk groups - number and holding times of calls, traffic intensity and volume, distributed on arbitrary external traffic directions, defined by the numbers called (direction-based analysis). The direction-based analysis is based on the charging data. In order to secure the privacy of the employees, all the calling numbers have been deleted during our analysis. Neither is any analysis based on particular numbers. The supporting system TELMAX is also distributed, using the broadband network already installed in UNIT/SINTEF and local Ethernet-segments. The system is PC-based (at UNIT/SINTEF IBM PS2 are used). There are altogether 21 PCs in the TELMAX system. The traffic module in TELMAX generates directly graphical curves showing the number of call attempts and the traffic. The output data are averages, i.e. measurements of load on server groups like leased circuits, signalling equipment, etc. For incoming traffic there is no direct registration mechanism. However, it is possible to measure - number of call attempts - number of calls which are set up manually (through the exchange switchboard) - total traffic (sum of incoming- and outgoing traffic). These registrations are not done automatically; they must be initiated manually. The information of outgoing calls are given by the charging data, which supply detailed information of every single successful call, including B-numbers. A typical record in a charging file is shown in Figure 1. It is possible to make analysis as detailed as desired. This kind of analysis has been performed earlier for the purpose of studying the statistics for repeated calls [1]. In the present study all the A-numbers have been deleted, so the direction-based analysis gives collective results for the whole exchange. 2.3 Arrangement of the observations 2.3.1 The observation periods The charging files from two observation periods in the 4th quarter of 1991 have been collected: - Period 1: Monday 1991.10.07 – Sunday 1991.10.20 - Period 2: Monday 1991.11.25 – Sunday 1991.12.08 Both periods have a two week duration. Since October is considered a “normal 119
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Contents Feature Guest editorial, A
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14 Table 2 Survey of some distribut
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20 j k λ ij µji λ ik µ ki λ ir
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22 14 Disturbed and shaped traffic
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40 3 Gaaren, S. LAN interconnection
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48 Telephone Systems” (published
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50 The life and work of Conny Palm
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56 Architectures for the modelling
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