## 5 Comparative Analysis based on the Design Guidelines
In this sense, with the exception of ISA SP100.11a and WirelessHART whose documentation (standards) can only be accessed by fee-payment, or IP500 Alliance whose specification has not been published up to date, the remaining approaches presented here are open-standards, which implies that, in principle, any user/researcher has full access to their documentation. On the other hand, Zigbee Pro (through its open-implementation called Open-ZB [58]) and 6 LoWPAN/RPL (available for TinyOS [59] and Contiki OS [60]) specifications can be freely downloaded, allowing the users to get their software modules including all their facilities for programming the resource-constrained network devices. In particular, it should be mentioned that Open-ZB solution is fully compliant with the Zigbee Pro specification, although it is not the one provided by Zigbee(r) Alliance (their implementations are only accessible by fee payment). The remaining proposals do not offer free source-code, excluding the IEEE 802.15.4e and IEEE 802.15.5 standard, which have not had any available implementation yet. On the other hand, new developments and extensions are currently restricted by fee-payment in Zigbee Pro, ISA SP100.11a and WirelessHART standards. This is a clear disadvantage in comparison with the rest of free source-code recommendations, as it may delay the expansion of these fee-payment solutions in the market. The memory and Central Processing Unit (CPU) utilization is another significant design issue to take into account. WirelessHART and ISA SP100.11a demand a larger amount of computing resources than the remaining solutions here presented in order to implement their entire protocol stack and to achieve the complete functionality of both standards. In the same line, the operation of IEEE 802.15.4e (both TSCH and DSME mechanisms [18]) requires a greater waste in memory and processing capabilities than Zigbee Pro, 6 LoWPAN/RPL, IP500, and IEEE 802.15.5 due to the higher complexity of implementation of the TDMA mechanism together with the channel hopping and adaptation techniques. In addition, the operation of the AODV protocol deteriorates the performance of Zigbee Pro through its reactive nature, which forces the nodes to be continuously processing routing information. Furthermore, in the 6 LoWPAN/RPL, IP500, and ISA SP100.11a proposals, the implementation of IPv6 connectivity and its associated compression and fragmentation processes entail a higher consumption of hardware resources in the devices comparing with approaches that do not use these functionalities. Finally, IEEE 802.15.5 solves the communications in mesh networks more efficiently, since all mandatory and non-mandatory functions are designed to be implemented in a simple manner (for instance this issue can be demonstrated by means of the synchronization algorithm proposed by SES) into a single layer. This assures, a priori, less utilization of computational and memory resources than the rest of proposals. The cost and the flexibility of the deployment are two key design decisions which, in many occasions, define the proposal to be employed by the end-user. Both have a strong dependence with other design issues such as the accessibility of the standard or the memory and computing utilization. In this regard, different WMSN manufacturers provide their proprietary hardware/software solutions in accordance with the specifications that they have selected for their implementations. The goal is to penetrate in a specific client-oriented market segment. In particular, specific software and hardware are addressed to non-specialized end-users in WSNs/WMSNs who can easily access this technology, or to experts who can quickly develop their implementations. To enjoy these advantages means an increase in costs because the devices (with its associated software modules) are exclusively provided by the manufacturer.