ELECTROTECHNICA & ELECTRONICA E+E Vol. 52. No 11-12/2017 Monthly scientific and technical journal Published by: The Union of Electronics, Electrical Engineering and Telecommunications /CEEC/, BULGARIA Editor-in-chief: C O N T E N T S Prof. Ivan Yatchev, Bulgaria TELECOMMUNICATIONS SCIENCE Deputy Editor-in-chief: Prof. Seferin Mirtchev, Bulgaria Seferin Mirtchev Editorial Board: Link throughput evaluation in telecommunication networks 1 Prof. Anatoliy Aleksandrov, Bulgaria Acad. Prof. Chavdar Rumenin, Bulgaria ELECTRONICS Prof. Christian Magele, Austria Dimiter Badarov Prof. Georgi Stoyanov, Bulgaria Assoc. Prof. Evdokia Sotirova, Bulgaria Teaching methodology for signature analysis Prof. Ewen Ritchie, Denmark and cyclic redundancy check 6 Prof. Hannes Toepfer, Germany Dr. Hartmut Brauer, Germany APPLICATION IN PRACTICE Prof. Marin Hristov, Bulgaria Prof. Maurizio Repetto, Italy Willian Dimitrov Prof. Mihail Antchev, Bulgaria GDPR entrapments. Proactive Prof. Nikolay Mihailov, Bulgaria and reactive (re)design thinking. 11 Prof. Radi Romansky, Bulgaria Prof. Rosen Vasilev, Bulgaria Krassimira Schwertner Prof. Takeshi Tanaka, Japan Towards autonomous hardware and software Prof. Ventsislav Valchev, Bulgaria in data base management systems 20 Dr. Vladimir Shelyagin, Ukraine Acad. Prof. Yuriy I. Yakymenko, Ukraine Filip Andonov, Georgi Petrov Assoc. Prof. Zahari Zarkov, Bulgaria Weather station for smart home applications 27 Advisory Board: Prof. Dimitar Rachev, Bulgaria UP-TO-DATE INFORMATION ON SCIENCE Prof. Emil Sokolov, Bulgaria IN BULGARIA Corr. Member Prof. Georgi Mladenov, Bulgaria Prof. Ivan Dotsinski, Bulgaria Ministry of Education and Science, Republic of Bulgaria Assoc. Prof. Ivan Vassilev, Bulgaria National strategy for development of scientific research Assoc. Prof. Ivan Shishkov, Bulgaria in the republic of Bulgaria 2017 – 2030 Prof. Jecho Kostov, Bulgaria (Better science for better Bulgaria). Prof. Lyudmil Dakovski, Bulgaria 5. Organization and control Prof. Mintcho Mintchev, Bulgaria on the strategy implementation, pp. 55-59. 32 Prof. Nickolay Velchev, Bulgaria Assoc. Prof. Petar Popov, Bulgaria Ministry of Education and Science, Republic of Bulgaria Prof. Sava Papazov, Bulgaria Bulgaria national roadmap for research Prof. Rumena Stancheva, Bulgaria infrastructure 2017-2023 Prof. Stefan Tabakov, Bulgaria Appendix №5: Profile of the RI in the national roadmap Technical editor: Zahari Zarkov in the republic of Bulgaria, pp. 65-87. 39 Corresponding address: 108 Rakovski St. Sofia 1000 BULGARIA Tel. +359 2 987 97 67 e-mail: [email protected] http://epluse.fnts.bg ISSN 0861-4717 TELECOMMUNICATIONS SCIENCE Link throughput evaluation in telecommunication networks Seferin Mirtchev When planning telecommunication networks it is important to determine the link throughput to provide quality of services, to avoid overloading and bottlenecks in the network. In this paper, a meth- od for evaluating the link throughput in modern telecommunications networks with packet switching based on the classic teletraffic system M/M/1/k is proposed. It is shown the dependence of the carried traffic from the queue length at a defined loss probability, and the dependence of the carried traffic from the defined waiting time, normalized to the average service time at a certain probability to wait more than a defined waiting time and a queue length. Presented graphic dependencies allow at de- fined quality of service, namely the probability of packet loss and admissible delays, to determine the allowable carried traffic of the lines. Determining the link throughput allows for efficient mechanisms operation of the congestion management in the modern telecommunications networks with packet switching. Оценка на пропускателната способност на линиите в телекомуникационните мрежи (Сеферин Т. Мирчев). При планиране на телекомуникационните мрежи е важно да се опреде- ли пропускателната способност на линиите, за да се предоставят качествени услуги, да не се допуска претоварване в мрежата и да се избягват тесните места. В този доклад е предло- жен метод за оценка на пропускателната способност на линиите в съвременните телекому- никационни мрежи с пакетна комутация на основата на класическата телетрафична систе- ма M/M/1/k. Показана е зависимостта на обслужения трафик от размера на опашката при зададена вероятност за загуби, а също и зависимостта на обслужения трафик от зададено време за чакане, нормирано спрямо средното време за обслужване, при определена вероят- ност да се чака повече от зададеното време и размер на опашката. Представените графични зависимости дават възможност при зададено качество на обслужване, а имено вероятност за загуба на пакети и допустими закъснения, да се определи допустимия обслужен трафик на линиите. Определянето на пропускателната способност на линиите дава възможност за ефективна работа на механизмите за управление на претоварванията в съвременните теле- комуникационни мрежи с пакетна комутация. 1. Introduction son arrival flow and exponentially distributed service The stochastic processes in the modern telecom- time, which simplifies the analysis. This assumption is munication networks with packet switching are typi- also accepted in the link throughput evaluation in this cally described by single-channel waiting systems. article. When planning telecommunication networks it The packet switching requires the packets to be stored is important to determine the bandwidth of lines to in memory and subsequent transmission to the corre- provide quality services, to prevent overloading and to sponding output. The behavior of the outputs of the avoid bottlenecks in the network. switches and routers is described by single channel The purpose of this article is to propose a method waiting systems with finite queues. The throughput of for the link throughput evaluation in modern tele- the outputs, defined by the maximum service traffic at communication networks with packet switching based a given service quality, determines the bandwidth of on the classical teletraffic system M/M/1/k. the lines connecting the switching nodes in the net- work. The throughput depends on line capacity or, in 2. State the problem in literature other words, on bandwidth. The teletraffic engineering provides useful tools In the core networks is typically accepted a Pois- for modeling random processes in telecommunication “Е+Е”, 11-12/2017 1 networks [1]. Usually the queueing models are widely queues can often be used to obtain comprehensive used in the network planning and for the quality of results, e.g., to predict global traffic behaviour [11]. service evaluation [2]. The queueing systems are used We look at the single server delay system M/M/1/k to evaluate the parameters of the quality of service as with a Poisson arrival process, exponentially distribut- probability of packet loss, average packet delay and ed service time and finite queue (Fig.1) [1,12]. throughput. The M/M/1/k queue is described with the follow- In [3] are presented formulas for the system ing arrival end departure intensities M/G/1/k. The results are compared with the formulas λ = λ when i= 0,1,2,...,k+ 1 for the M/M/1/k queue and with the simulation model- i (1) μ= μ = + , ing. The characteristics of the M/G/1/k system are j j 1,2,3,...,k 1 evaluated and the applicability of the practical design, optimization and management approach is demon- whare λ is the packet arrival intensity; strated. μ is the departure intensity; A new analytical model of the IEEE 802.11 net- k is the queue size. work is presented in [4] with a distributed channel The finite state-transition diagram of the investi- access coordinate function based on the M/M/1/k sin- gated single server queue with Poisson arrival process, gle channel system. The proposed model makes it exponentially distributed service time and finite queue possible to evaluate the throughput, delays and loss of is shown in Fig. 2. frames. The steady state probabilities Pj of the single server In [5], the characteristics of a finite capacity queue are obtained through thehe general solution of femtocell network are evaluated using the single- the birth and death processes channel M/M/1/k waiting system through the proba- j − bility of packet loss, average packet delays and usabil- = A (1 A ) = + (2) Pj + when j 0,1,2,...,k 1 , ity. 1− Ak 2 In [6] a wireless mesh network is studied by load whare A = λ/μ is the offered traffic, which is equal to balancing and node modeling based on the single- the ratio of the arrival and departure intensities. channel waiting system M/M/1. The algorithms for the traffic distribution in wireless mesh networks 4. Performance measures M/M/1/k through the model of the lines based on the waiting teletraffic system M/D/1 is presented in [7]. The carried traffic is equivalent to the probability In [8] the wireless mesh networks nodes are mod- that the system is busy eled as a combination of two single channel teletraffic (3) A= 1 − P . systems M/M/1/k distinguish between retransmitted o 0 and local generated traffic. With the developed analyt- The time congestion probability B describes the ical model is evaluated the throughput and the delays fraction of time for which all waiting rooms are busy of a clustered FiWi network. = In [9] is analyzed the continuous time system (4) BPk+ 1 . M/M/1 in which the server operates at two different The mean number of packets in the system is speeds. The behavior of the single-channel system k+ 1 determines the behavior of a fluid buffer, which ena- = bles this model to describe the process of traffic shap- (5) L j Pj = ing with two levels in an ATM network. j 1 In [10] a relatively complex single-channel system From the Little formula, we have the mean time in M(N)/G/1/k with state-dependent arrivals, generally the system distributed service time and service interruptions is = λ studied. (6) WL In the cited publications based on the single chan- The queue size for given probability of losses and nel waiting system, there is no direct task to evaluate offered traffic can be determined by the following the link throughput in modern telecommunication formula obtained from (2) and (4) networks ln [ B (1− A − AB ) 3.