{'fraction_non_alphanumeric': 0.02102803738317757, 'fraction_numerical': 0.0032710280373831778, 'mean_word_length': 5.117142857142857, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Chapter 3 A cross-layer environmental approach to monitoring with WSNs 3 . 1

The PRISM protocol described in the previous chapter is a viable solution for real-time structural monitoring of structures. For example, one of its foreseeable applications is the monitoring of the vibrations produced in a power plant when the generators start or stop. Their switch-on instant is known, and it is possible to determine also when one or more elements will stop, for example for periodic maintenance or due to a reduction in the network load. In this scenario, continuous monitoring is not required – structural engineers are not interested in the vibrations produced during normal operation, and they need the data acquired during specific events only. However, this is not the case for other scenarios, such as home automation, agricultural monitoring, and environmental preservation. In these contexts, the data rates involved are limited, the hard real-time constraints may be relaxed, and new samples can be acquired after minutes instead of seconds or less [3, 4]. On the other side, such a system is supposed to acquire samples continuously during time. In addition, compared to the scenarios considered for PRISM, typical environmental applications are much more dynamic: nodes can enter or leave the network after the initial deployment, and the routing algorithm should be able to survive the sudden loss of one or more sensors. In other words, a more efficient solution is needed for ruling both channel access and data delivery. As far as the MAC layer is concerned, the scheduled approaches previously described in Section 1.2 are those best suited for environmental applications, although some preamble sampling methods might be applied too. Obviously, the selected channel access technique should be coupled with a proper routing layer and an efficient node activation protocol. According to the traditional design principles of communication networks, the protocols running at different levels in the stack are independent and interact through static interfaces. However, the traditional layered design approach is not well suited