# An Accuracy-Aware Energy-Efficient Multipath Routing Algorithm for WSNs
## 6 Evaluation
### Comparison with Other Algorithms  
In this section, we conduct a comparative analysis of the EMRAR algorithm against three other algorithms: CADC proposed in [15], AMRBEC proposed in [29], and IQMRP proposed in [35]. Figure 5 presents a performance comparison of these four algorithms in terms of AAL, PDR, and NRE under different data transmission rates with a fixed \(\Delta\) value of 3% and an adjacent node density of 20. The NRE is calculated after running each algorithm for 500 rounds. From these three figures, we can see that as the data transmission rate increases from 50 bps to 100 bps, all four algorithms exhibit a similar trend on AAL, PDR, and NRE. However, for different densities of adjacent nodes, EMRAR consistently outperforms the other three algorithms in most scenarios. The rationale behind this can be explained as follows. For the AAL in Figure 5a, CADC establishes a tree-based topology rooted at the sink node. It gives upper bounds for estimation error and estimation distortion, which are used to evaluate the accuracy of the data. Although it employs lossy compression to mitigate congestion, it primarily focuses on meeting these upper bounds, potentially resulting in a relatively high AAL if the bounds are not stringent. In contrast, IQMRP adopts an Ant Colony Optimization (ACO) technique to choose the multipath, which, while reducing the number of intersection nodes to some extent, has limited effectiveness in minimizing AAL. For AMRBEC, it consistently establishes a disjointed multipath, and the data are only aggregated at the sink of the node, leading to the lowest data accuracy loss among the four algorithms. For the PDR in Figure 5b, as the data transmission rate increases, the PDRs of all four algorithms decline because of heightened packet congestion. Among them, CADC does not adopt multipath routing. The single transmission route results in a lower transmission reliability compared to the others. IQMRP chooses multipath based on QoS parameters such as residual energy, bandwidth, and next-hop accessibility. It improves the PDR but with a predefined threshold for path quality evaluation, which is less adaptive. The metrics for AMRBEC to choose the multipath are similar to IQMRP. It is based on the residual energy, distance, hops, and the balance of energy consumption, which are less related to channel quality, leading to more pronounced errors or packet losses than those of IQMRP. EMRAR treats reliability as an optimization objective directly, which can improve the PDR effectively. For the NRE in Figure 5c, CADC exhibits poor NRE performance due to two primary reasons. First, the routing algorithm is not power-aware, and second, it uses a tree-based topology to transmit data to the sink, which is known to have a disadvantage in balancing energy consumption at the nodes near the sink. IQMRP chooses the multipath by balancing the residual energy, bandwidth, and next-hop accessibility, with residual energy just one of the considerations. AMRBEC initially has the highest residual energy at a lower data transmission rate (<50 kbps), but it degrades as the data transmission rates increase. There are two reasons. First, it must establish the node-disjointed multipath, which involves selecting more nodes, and it is difficult to find shorter paths while adhering to the energy constraints. Second, AMRBEC establishes the multipath without considering the quality of the paths, such as error and packet loss. Thus, the retransmission will consume more energy when dealing with higher offered loads. EMRAR considers both node residual energy and path energy consumption while adhering to the transmission reliability constraint. As a result, it has the best residual energy performance, especially in scenarios with higher offered loads. Figure 6 provides the comparison of the convergence times under different densities of adjacent nodes.