## 5 Comparative Analysis based on the Design Guidelines  
The valuable benefits of wireless mesh sensor networks have led to the emergence of many standards and proposals promoted not only by the scientific community but also by the commercial and industrial sectors to support real deployments. Among all of them, we agree with the On World study [3] that the most appropriate solution must be a standard validated by the scientific community and commercial sector which satisfies the strict requirements of the low-rate WPAN. In this context and having into account the different WMSN solutions presented in Section 3 together with the IEEE 802.15.5 standard described in Section 4, developers and users should select the approach that best adapts to the necessities of their application. In order to aid the end-user to make the best technological selection, we propose diverse _design guidelines_ in accordance with the main WMSN requirements identified in this work (Section 2). These rules are detailed in the next paragraphs and summarized in Table 2.  
Figure 5: Examples of ASES transmission: (**a**) unicast without extending the receiver’s AD; (**b**) unicast by extending the receiver’s AD; and (**c**) broadcast. Firstly, several researchers and task groups, namely 6 LoWPAN, ROLL, IP500 Alliance and ISA, have decided on adapting the IPv6 protocol to the IEEE 802.15.4 MAC and PHY layers, mainly to carry out the tasks of addressing and routing. However, the traditional IP protocol stack was designed to be executed on devices such as computers, laptops or tablet-PCs, which have much more hardware and energy resources than sensor nodes. This is the reason why we argue that the operation of WPAN nodes under the IPv6 protocol stack can be inefficient, due to its associated higher implementation complexity and, as a consequence, higher computational and memory costs. On the other hand, one of the major reasons why IPv6 was included in the LR-WPAN field was because it confers the ability to connect nodes directly to external IP-based technologies (e.g., Internet) without considering, a priori, a gateway or proxy device. However, although this facility allows to intercommunicate heterogonous technologies (e.g., Wi-Fi/Ethernet with 6 LoWPAN by means of IPv6 addresses) at network layer, the implementation of additional software to adapt the information dispatched by other technologies to WMSNs under the message format defined by IEEE 802.15.4 MAC and PHY layers [8] is not eliminated. This means that part of the gateway functionality must unavoidably be included in each WPAN device, what demands more processing, memory and energy resources. The next consideration is aimed at selecting the proper addressing scheme for the mesh network (in-network). It is tightly coupled with the routing protocol employed because the type of addressing scheme may imply more complexity of the routing tasks and, as a result, more memory, processing and energy resources in the WPAN devices. In this sense, most of the proposals reviewed in this work have 16-bits logical addresses in their configuration. This value allows us to scale networks up to 65536 devices. Using other addressing schemes (e.g., 64-bit IEEE or IPv6), the maximum number of devices that may form the network sharply increase, so the addressing scheme selected by the user will be closely associated with the scalability of the network to deploy. However, selecting 16-bit IEEE means that routing tables reserve less memory space than in the case of 64-bit or IPv6 addresses and, therefore, the devices are more agile when they handle these tables. Another important issue is the accessibility and availability of implementations that accelerate the development of new designs and improvements.