Sensores para seguridad y fiabilidad en sistemas de comunicaciones

Abstract

The boom in wireless communications has been signlficant in recent decades, promoting the deveiopment of different standards and their use in muitiple applications, but on the other hand, wlred communications are still widely used in certaln sectors. Currentiy, security and reliability in any communications system has become a top priority in al! areas: consumption, domestic, industrial, defense, etc. In this line. this thesis addresses asoects of securitv and rellabilitv in both wireless and wired communications. To do this, three applications have been chosen to study sorne problems in this type of communications and provide solutions to them. In a first line of work the IEEE standard 802.15.4 has been studied anda new mechanism has been proposed to solve the problem related to the high association time of mobile nodes, where their continuous associations affect the activity time. The proposed procedure allows the transmission of data from a mobile node and the receptlon of data from static nodes with a mínimum activity time and high communication reliability, also reducing power consumptlon and data loss. Continuing with this line, a network of wireless sensors has been deployed to detect failures In engines facilitating their preventive maintenance. On the one hand, the reiiability in the detection Is ensured by the comblnation of severa! parameters (vibrations, currents and temperature); and on the other hand, the use of the beacon mode with guaranteed time interval (GTS) ensures the correct transmisslon of the data. Taking into account that in this type of wireless appllcations it is mandatory to reduce the power consumption, a hardware and software strategy has been developed so that the nodes reach a high degree of autonomy. In a second line of work, a wired communication based on the I2C protocol has been considered. In this case, vulnerability in the communication associated with the use of high impedance as one of the logical levels has been studled. Thls fact, whlch guarantees greater scalability on the bus, can introduce failures in communications, whether intentional or unintentional. In the first place, the effect of these failures on the trajectory followed by a mobile robot has been studled, showing that this trajectory can be altered. Second, a defense strategy has been developed to identify these types of situations and act accordingly. The strategy is based on the use of a frequency sensor that detects anomalies in the bus timing line.