# Secure and Time-Aware Communication of Wireless Sensors Monitoring Overhead Transmission Lines
## 2 Related Work  
The smart grid can provide efficient, reliable, and safe energy automation service with two-way communication and electricity flows. The use of WSN helps in capturing and analyzing data related to power usage, delivery, and generation. The energy usage and management information, including the energy usage frequency, phase angle and the values of voltage, can be read in real time from remote devices. Therefore, utility companies can manage electricity demand efficiently. They can reduce operational costs by eliminating the need for human readers and provide an automatic pricing system for customers, who can enjoy highly reliable, flexible, readily accessible and cost-effective energy services. However, in order to achieve a trade-off between the performance and potential time delays, the analyzed architecture should be carefully examined. Given the vast geographical expanse of the transmission grid architecture, delivering monitoring information to the control center in a cost efficient and timely manner is a critical challenge to be addressed in order to build an intelligent smart grid. Since WSNs present a feasible and effective solution for transmission of monitoring data, there exist many works dealing with the possibility of adopting WSN for the purposes of monitoring the operational parameters of power lines [9; 10; 11; 12]. Although optimization of WSN architectures monitoring transmission lines has been examined many times before [2; 3; 13; 14], there was no exact analysis concerning security of provided solutions. In [13] the authors propose a hybrid (combined of wired (copper cable/optical fiber and wireless (cellular/IEEE 802.15.4) standards) hierarchical network to provide cost optimized delay and bandwidth constrained data transmission. They formulate a placement problem in order to optimize the number and location of the cellular enabled towers (base stations) to significantly reduce the operational and installation costs while respecting effective data transmission, bandwidth, delay and connectivity constraints. Their goal was to minimize the installation and operational cost while satisfying the latency and bandwidth constraints of the data flows. Researchers evaluate proposed solution (using the ILOG CPLEX 12.2 software for the simulation), considering an example transmission line network with defined number of towers, average span, data packet length and bandwidth. They examine different scenarios, including variation in flow bandwidth, network size and compare obtained results. Although scientists claim that their method is generic and encompasses variation in several factors, they consider neither the security of the transmission, nor the routing algorithms responsible for traversing the data to the base station. Another paper, which deals with a problem of efficient communication of sensors monitoring transmission power lines, is presented in [3]. Here, the researchers propose a network model, in which wireless sensors, deployed all over transmission line, communicate with each other in order to (if needed) reconfigure (based on the application requirements) to deliver information to substations efficiently and effectively. The authors examine the performance of the linear network model, providing calculations using sensors with defined characteristics. Then, they present an example reconfigurable network model and illustrate its usage with a simple case study. In the article, scientists emphasize on transmission time delays, mentioning neither energy consumption, nor security. [2] consists of extended research proposed in [3]. In this paper, authors study how the data measured on transmission power lines can be delivered efficiently to substations. They try to find the optimal placement of direct wireless links, aiming at minimizing the delay in information delivery.