# Reliable Link Level Routing Algorithm in Pipeline Monitoring Using Implicit Acknowledgements
## 2 Related Work
The Stream Control Transmission Protocol-WAN (SCTP-WSN) [24] adopts the concept of Multihoming and adopts the SCTP transport protocol combined with the AODV routing protocol to provide network reliability with eACK. GARUDA [25] studies the reliability of the delivery of point-to-multipoint data in the downstream direction, from a sink to the sensor nodes using NACK. The Aggregation and Transmission Protocol (ATP) transport protocol [26] includes an end-to-end feedback control algorithm assisted by the receiving node and the network to counteract packet loss, using selective ACK. Nevertheless, using end-to-end mechanisms for reliability has also drawbacks, such as a higher delay because of the end-to end retransmissions. In [27], the authors study the advantage of using hop-to-hop, instead of end-to-end acknowledgment, and in [28; 29] the authors study the advantage of using iACK, instead of eACK in wireless sensor networks. Based on these conclusions, our proposal decreases the energy consumption and minimizes the delays using iACK for the communication. It provides the same reliability, end-to-end connectivity, and scalability as previous proposals that implement high level routing protocols and eACK mechanisms. We take advantage of the previous work and we propose a new cross-layer algorithm for LWSNs, which unifies MAC, routing, and address assignation. This algorithm also provides end-to-end reliability and solves the hidden nodes problem without requiring ACK, RTS, or CTS signaling. Nevertheless, our proposal combines several advantages compared with previous proposals, such as the presented in [12], where the authors review different LPWAN protocols considering static and mobile nodes. Table 1 compares our proposal with the protocols presented for static nodes and some other proposals specifically designed for large scale linear infrastructures. It is important to note that all the studied protocols at the link level use eACK, while our proposal uses iACKs because of the benefits provided for linear infrastructures. Thus, our work is essential to facilitate the deployment of simple and cheap LWSNs, pave the way for the implementation of new services and applications [30] and take advantage of new paradigms such as fog computing [31], cloud computing [32], and the analysis of large amounts of data [33] also in LWSNs. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline  & \begin{tabular}{c} **Address** \\ **Autocon-** \\ **fig-** \\ \end{tabular}  & \begin{tabular}{c} **Same Net.** \\ **and Link** \\ **Addc.** \\ \end{tabular}  & **aACK** & **iACK** & **Linear** & \begin{tabular}{c} **End-to-** \\ **Topology** \\ \end{tabular}  & \begin{tabular}{c} **Topology** \\ **Clustering** \\ **Relail-** \\ \end{tabular}  & \begin{tabular}{c} **Energy** \\ **Discovery** \\ **\end{tabular}  & \begin{tabular}{c} **End-to-** \\ **End** \\ **Delay** \\ \end{tabular}  & \ \begin{tabular}{c} **Large** \\ **Scale** \\ \end{tabular}  & \begin{tabular}{c} **Access** \\ **channel** \\ **and Node** \\ **Failure** \\ \end{tabular}  \\ \hline This proposal & yes & yes & yes & no & yes & yes & no & yes & yes & yes & yes & yes & CSMA/CA & yes \\ \hline \multicolumn{11}{c}{Application and transport level} \\ \hline RCRT [23] & no & no & yes & no & no & No & yes & no & No & yes & no & n.a & yes \\ GARUDA [25] & no & no & yes & no & no & Yes & yes & no & n.a. & no & yes & n.a & yes \\ ATP [26] & no & no & yes & no & No & yes & no & No & yes & yes & yes & n.a & no \\ SCTWSN [24] & no & no & yes & no & no & No & yes & yes & n.a. & no & yes & n.a. & yes \\ \hline \multicolumn{11}{c}{Network level} \\ \hline SimpleMode [34] & no & yes & no & no & yes & No & no & yes & yes & no & yes & n.a. & yes \\ MERR [35] & no & no & no & yes & No & no & yes & no & yes & no & yes & n.a. & no \\ LDG [36] & no & no & no & no & No & Yes & no & yes & yes & yes & yes & n.a.