A contribution to modeling sensor communication networks by using finite-source queueing systems Tam´ as B´ erczes, B´ ela Alm´ asi, J´ anos Sztrik, Attila Kuki Faculty of Informatics, University of Debrecen Debrecen, Hungary, {berczes.tamas,almasi.bela,sztrik.janos,kuki.attila}@inf.unideb.hu Abstract—In this paper we introduce a finite source retrial queueing model to investigate the performance characteristics of the wireless transmission problem in sensor networks. We divide the sensors into two classes. The first one is the ”Emergency” class, which performs the notification of special emergency situations (eg. fire alarms). The second one is the ”Normal” class, which measures and transmits environmental data (eg. temperature). For the performance evaluation of the wireless transmission we study and compare two cases: In the first model the RF transmission possibility will be available randomly for the sensor nodes (Non Controlled case) and in the second model the RF transmission requests coming from the emergency class, will access the wireless channel immediately (Controlled case). Our main interest is to give the main steady-state performance measures of the system computed by the help of the MOSEL tool. I. I NTRODUCTION Wireless sensor networks are widely used to implement low cost unattend monitoring of different environments. Baronti et al. [1] showed that the technology limits are far beyond the current usage. Chiany [2] represented the wireless sensor networks as a system containing three main components see Figure 1. Buchmann showed [3] that the operation mechanisms depending on the vendor implementations can be totally dif- ferent, but also common features are observable. For example, power saving is a standard requirement to achieve long time operation of the wireless nodes. Similarly, a common feature that the wireless data transmission can appear as a bottleneck in the operation (see. [4]). The retrial queueing systems are widely used to model wireless communication systems (see. [5], [6], [7]). In this paper we introduce a retrial queueing model to investigate the performance characteristics of the wireless transmission problem in the sensor networks. We divide the sensors into two classes. The first one is the ”Emergency” class, which performs the notification of special emergency situations (eg. fire alarms). The second one is the ”Normal” class, which measures and transmits environmental data (eg. temperature). The emergency class has priority over the normal class in the operation. For the performance evaluation of the wire- less transmission we study and compare two cases: In the first model the RF transmission possibility will be available randomly for the sensor nodes (Non Controlled case). In the second model the RF transmission requests coming from the Fig. 1. Wireless sensor network. Fig. 2. A retrial queue with components emergency class will access the wireless channel immediately (Controlled case). The rest of this paper is organized as follows. In Section 2 we present the corresponding queueing model. Numerical results and their discussion are provided in Section 3. Finally, Section 4 concludes the paper. II. SYSTEM MODEL Let’s see a queueing model with a single server unit (RF unit), where the jobs come from two groups of finite sources. These sources represent the sensors. The first class of sensors cor- responds to the emergency case alerts (eg. fire alarms), while the second one refers to the normal case (eg. temperature, humidity measurement). The number of sensors of the first class is denoted by N , and the number of sensors of the second class is denoted by K. The sensors send a new service request (ie. to send the measured value through the radio interface). The distribution of the inter-request times is exponential with parameter λ 1 for the emergency sensors and with parameter – 89 – 8th IEEE International Symposium on Applied Computational Intelligence and Informatics • May 23–25, 2013 • Timisoara, Romania 978-1-4673-6400-3/13/$31.00 ©2013 IEEE