## 1 Introduction
We want to demonstrate that the traditional AODV routing protocol designed without considering the relationship between communication and control cannot be appropriately used in wireless networked control applications. * The proposed routing solution is simple, but it can improve both energy consumption and control system output. Its routing decision is developed based on the information from physical, MAC, and routing layers within the network protocol stack. However, it does not require any modification at physical and MAC layers. For the first contribution, AODV routing over IEEE 802.15.4 are the communication protocols evaluated in this study. A building temperature control [3; 4; 5] is modeled as a control application. Additionally, we intend to generate constant bit rate (CBR) background traffic at different rates on one link of our network scenario. On increasing of the CBR rates, the failure of route establishment process and the possibility of the data packet loss are getting higher. Thus, how the AODV handles this situation and how AODV routing procedure influences control output performances are investigated. The simulation result demonstrates that the original AODV routing algorithm establishes the freshest and the shortest routes for data transmission. It can select a path with a high traffic load although it experiences the high rate of collisions or the unsuccessful transmission of routing and data messages caused by the CBR traffic interruption. The failure of the path-setup and the loss of data messages result in the uncontrollable system and the waste of energy consumption. For the second contribution, we propose a routing solution by enhancing the original AODV routing mechanism to address such research problems. The modified algorithm can automatically avoid any paths with high traffic loads by using a delay-time of a routing message transmission compared to a predefined threshold. On a high-loaded link, messages in queues will wait for a longer time before they are sent in comparison with the case of low loads [28]. Thus, the link is considered to be congested if the delay-time of routing messages is greater than the predefined threshold. The predefined threshold is the average delay of routing message transmissions in the IEEE 802.15.4 wireless network. By this proposed solution, the path with low traffic interruption among possible routes will be often chosen for delivering measured data. This can lead to reduce the failure of path-setup and the loss of data messages. The simulation results also confirm that both the energy consumption and the control system response are improved. The remainder of this paper is organized as follows: Section 2 discusses related works. Section 3 develops WSAN control system models; the control system model, the WSAN communication model, and the performance metrics are described in details. Section 4 demonstrates the problems of the disjoint communication and control design in WSANs; energy consumption and control response evaluations of the traditional AODV and the proposed routing protocols over IEEE 802.15.4 for building temperature control are investigated. Finally, Section 5 concludes this paper.