# Low Power Multi-Hop Networking Analysis in Intelligent Environments
## 1 Introduction  
Intelligent systems are usually included in environments where not only sensing and recognition capabilities are required, but also the collection, processing, changing and sharing of the available context information. Such environments represent a new information technology paradigm and they are also called intelligent environments or ambient intelligence. They consist of the integration of information technologies into everyday objects in order to improve the quality of life. Intelligent systems are a multidisciplinary approach [1], as they require the convergence of many areas of Computer Science in order to fulfill their purpose. Many devices are usually added to intelligent environments. Specifically, such environments include electronic systems to interconnect nodes and communicate the measured data. Every intelligent device should be able to transmit and receive the context information that is collected by the sensors. The information is usually processed and/or zipped before its transmission [2; 3] because the radio transmission at the node consumes more energy than any other operation at the node [4; 5]. However, since in many environments the context information usually changes at a low pace, the continuous sensing of that information is not necessary, so it is possible to make the nodes sleep at regular intervals. In fact, intelligent environments composed of wireless multi-hop networks usually require long-life sensor nodes to be interconnected through a communication network. Hence, it is not only possible but also mandatory to work with devices in low power mode in such intelligent environments. In order to extend the life of nodes, they can be connected to the mains so that there would be no need to care about the power consumption of the nodes. Moreover, when a battery is added to the node, the node would still be fully operational in case of blackouts. When there is no chance to connect the nodes to the mains, they should have a battery power supply and, besides, they must work in low power mode so that the life-cycle of the node is as long as possible. The inactivity intervals of the gateway and sensor nodes can be scheduled to reduce their power consumption and, hence, the consumption of the whole network. However, the inactivity intervals have a deep influence in the degradation of the time performance of the network. Thus, even if the nodes included in the network might be connected to the mains, it is important to reduce the power bill of the whole network without degrading significantly its performance in terms of response time or latency. Generally speaking, any application that needs to share the measured data for their collaborative use is considered here. There is a wide range of applications with this feature. Some examples of such wireless networks are intelligent environments (smart cities or homes, augmented reality, or ubiquitous computing systems), or some monitoring networks such as environmental (air or water quality monitoring, and landslide or forest fire detection), health care (at hospitals, homes for the Elderly or by means of wearable devices), industrial (structural health monitoring, or machine health monitoring) and area monitoring networks (geo-fencing of pipelines, and enemy intrusion detection). This paper focuses on intelligent environment applications. In wireless networks, the achievement of the specific Quality of Service (QoS) through the allocation of the limited resources among users is still an open challenge [6]. The allocation of resources [7] can take place according to some performance metrics, such as throughput and fairness [8; 9; 10; 11; 12] or according to the traffic types [13; 14; 15]. However, there are other metrics to evaluate the performance of the network, as the latency in the communication. In fact, the analysis of the time performance of wireless networks is a key point due to many facts [16]. First, there is an increasing use of wireless networks for limited response time applications.