Performance Analysis of a Wireless Sensor Network for Seism Detection in an Overlay Cognitive Radio System Hassel Aurora Alcalá Garrido 2 , Mario Eduardo Rivero-Angeles 1 , Izlian Yolanda Orea-Flores 2 , Ramsés Rodríguez 3 1 Communication Networks Laboratory, CIC-IPN. Av. Juan de Dios Bátiz, Col. Nueva Industrial Vallejo, Gustavo A. Madero, Mexico City, 07738. 2 Telematics Department, UPIITA-IPN. 2580 Instituto Politécnico Nacional Avenue, Barrio La Laguna Ticomán, Gustavo A. Madero, Mexico City, 07340. 3 SEPI ESIA-IPN Zacatenco. Luis Enrique Erro Avenue, Zacatenco, Gustavo A. Madero. Mexico City, 07738 Abstract. This paper studies the performance of a wireless sensor network (WSN) with cognitive radio (CR) capabilities to gather information about structural health monitoring (SHM) of buildings in case of seismic activity. The system performance is evaluated in terms of energy consumption and average packet delay using a discrete event simulator. In order to efficiently use the resources of the network and considering that the WSN will be installed in office or home buildings, we propose the use of the empty (white) spaces in a conventional cellular system. Thus, the WSN will act as secondary network, which do not affect the quality of service of the primary network, since it will work in an overlay structure. The main performance parameter of the primary network is the blocking probability since a Blocked Call Cleared (BCC) system is considered. By using the data collected in the WSN and transmitted through the unused channels of the cellular system, it is possible evaluate the damage caused by the seismic activity in a certain building. The major benefit of using a WSN with CR capabilities compared to the traditional approach, i.e., only one sensor per building floor or even per building is that with the WSN it is possible to collect much more information related to both the seism and the effects on the monitored building without the additional traffic in the already crowded unlicensed spectrum. Keywords: Wireless Sensor Networks (WSN), Cognitive Radio (CR), Blocked Calls Cleared (BCC) system, Seism detection, Structural Health Monitoring (SHM) 1 Introduction Wireless sensor networks (WSN) are composed of a large number of small sensor nodes with limited computing power, which are limited by their size and lifetime; usually they have a single omnidirectional antenna [1] to communicate with each 79 Research in Computing Science 75 (2014) pp. 79–86; rec. 2014-06-12; acc. 2014-07-21