## 5 Comparative Analysis based on the Design Guidelines
For instance, Dust Networks, a leading company in WSNs for the industrial sector (which was recently acquired by Linear Technology [61]) offers proprietary hardware and software highly compatible with WirelessHART, 6 LoWPAN and ISA technologies. However, the cost of its products is up to 30% higher than those provided for example by MEMSIC [62], world-wide manufacturer of wireless sensor hardware (TelosB, MicaZ and Iris platforms) addressed to programming most of the WMSN approaches discussed in this work, or higher than those provided by other small companies and manufacturers [63, 64, 65] that market a low-cost and ultra-low energy WSN platforms, offering straightforward solutions for a large number of applications. In addition, the lack of flexibility is another problem associated to these proprietary solutions. This is due to the fact that usually manufacturers offer the user an API at the application level which is insufficient for accessing the full protocol stack, which in turn restricts the possibility of modifying Physical or MAC design parameters, for example. Under these circumstances, WirelessHART and ISA SP100.11a are solutions that follow these concerns, requiring, on the one hand, specific hardware which is capable of supporting all the functionality defined by these standards, and, on the other hand, a fee payment to have free access to the documentation and API implementation. Therefore, the rest of proposalspresented in this work are cheaper and more flexible. This implies that their different layers can be programmed and installed in the majority of available wireless sensor platforms of the market. The next design concern is referred to the number and importance of additional services/functionalities offered by the different proposals which are out of the scope of the requirements exposed in Section 2. In this framework, the IEEE 805.15.5 is the WMSN standard that must allow to design and develop, in our opinion, a larger amount of real-world applications mainly due to its non-mandatory functions (multicast, reliable broadcast or network synchronization, among others). So, for the first time, all these features are integrated in a same recommendation, what makes IEEE 805.15.5 more advantageous against the other proposals that only solve specific concerns of the WMSN communications as, for instance, the message latency. Another important matter to be addressed by the end-user is the possibility of deploying large-scale networks, which is directly associated to the concept of scalability of the network. In this context, the scalability of 6 LoWPAN/RPL, IP500, WirelessHART, ISA SP100.11a and IEEE 802.15.4e is not completely demonstrated due to the lack of studies that assess and validate this issue (for instance, solutions performed over IEEE 802.15.4e only consider, as a maximum value, 25 nodes in their evaluations [45]). However, one of the primary design objectives of the IEEE 802.15.5 standard is related to the scalability, being its performance studied and evaluated in detail in [8]. In particular, authors in [8] compare the IEEE 802.15.5 and Zigbee (AODV) routing schemes in WMSNs composed of topologies ranging from 49 nodes to 784 nodes, revealing a better behavior/network performance for the IEEE 802.15.5. Furthermore, these results confirm the well-known lack of scalability of the AODV protocol. Finally, as regards power consumption, Zigbee Pro does not currently provide any energy saving mechanism to extend the nodes's lifetime. For WirelessHART and ISA SP100.11a, energy-efficiency is tightly associated to the TDMA scheduling. Nevertheless, the employment of a central node (Network Manager) implies a noticeable increase in the network overhead, which in turn degrades network lifetime, especially for the case of large-scale network deployments.