This last case refers to the use of WiFi access points (APs) [10,16] or GSM/UMTS base stations (BS) identifiers [5,17] that can be used to represent the coverage area under that AP or BS. The location technology used has effects on the location accuracy as well as on the location information retrieval process. GPS allows to obtain the location with www.selleckchem.com/products/Tipifarnib(R115777).html an error lower than 50 m [18], but its use entails two main problems. The first one is related to coverage, since there is no GPS coverage inside buildings, where users spend most of their daily lives. The second problem derived from using GPS is its high energy consumption, which drains the terminal battery really fast. Although the accuracy of WiFi system (lower than 100 m, i.e.
, the AP coverage area [19]) and GSM/UMTS network (from 100 m in urban areas to several kilometers in rural areas [20]) are worse than that of GPS, both of them avoid the problems exposed above. Since GSM/UMTS network has global coverage, we will be using this technology in order to locate users.We can also classify location prediction algorithms depending on where the prediction is made. Some works [5,6] propose all the processing to be made by the system or the network, so that the terminal is not involved in the process. However, this approach has several drawbacks, as pointed out in [13]. Tracking mobility from the network means to have a central element where all the tracking information will be stored. If this database fails or is compromised, all the data would be lost, or even worse, very sensitive personal information would be disclosed.
Moreover, if the terminal needs these location data, some kind of connection must be used in order to retrieve such information. However, it could be the case of needing this information during offline situations. Therefore, many approaches have switched to make the prediction on the terminal itself [13,21]. Nevertheless, it must be noticed that this option has also a drawback. Anacetrapib Mobile devices have limited resources, both memory
Compared to conventional glass fibers, polymer optical fibers (POFs) have a larger core diameter, greater flexibility, lighter weight, and a lower cost [1], and as a result, POFs have attracted intensive interest for sensing applications in recent years [2�C18]. Arrue et al. [2] showed that the power loss induced in bent POFs increases as the bend radius is reduced. Zubia et al. [3] proposed a POF-based barrier sensor for detecting the wind speed in a wind generator. Lomer selleck chemicals et al. [4] developed a quasi-distributed system for level sensing based on a bent side-polished POF cable. Kuang et al. [5] presented a POF sensor for crack detection and vertical deflection monitoring in concrete beams under flexural loading conditions. Kulkarni et al.