Introduction
In the era of the Internet of Things (IoT), the widespread adoption of low-power and lossy network (LLN) applications has led to the generation of vast amounts of data, posing a critical challenge in terms of efficient data routing within these networks. The Routing Protocol for Low-Power and Lossy Networks (RPL) was designed to address the limitations often observed in LLN environments, which are particularly prevalent in IoT networks.
The RPL protocol is optimized for static networks that do not involve mobility or topological changes. While it ensures continuous connectivity between nodes and mitigates the risk of data loss in stationary IoT applications, it struggles to manage the displacement of nodes and alterations in network structure, which are common in many LLN applications. As a result, nodes may experience disconnection, leading to packet loss and energy depletion.
To address these limitations, researchers have proposed various approaches to enhance the routing capabilities of RPL, with a focus on improving network performance, stability, and energy efficiency. One such solution is the Network Performance Stability using the Intelligent Routing protocol (nPSIR), which builds upon the RPL framework to enable unrestricted mobility of nodes within the Directed Acyclic Graph (DAG) while ensuring seamless and uninterrupted connectivity.
In this article, we delve into the details of the nPSIR protocol, exploring its unique features and how it addresses the challenges faced by traditional RPL in dynamic IoT environments. We will also examine the performance of nPSIR in comparison to other state-of-the-art routing protocols, such as mPRL, GI-RPL, Mobi-RPL, and ARMOR, through extensive simulations and analysis.
The Limitations of RPL in Mobile IoT Networks
The RPL protocol has been widely adopted in the IoT domain due to its ability to maintain continuous connectivity and mitigate data loss in stationary applications. However, its limitations become apparent when dealing with mobile nodes and dynamic network topologies.
One of the key challenges is the protocol’s inability to effectively manage the displacement of nodes and changes in network configuration. When nodes move or the network structure is altered, RPL may experience issues such as node disconnection, packet loss, and energy depletion. This is particularly problematic in IoT applications that involve mobile devices or scenarios with changing environments, such as smart cities, vehicular networks, and industrial automation.
Additionally, RPL’s tree-like structure, known as the Directed Acyclic Graph (DAG), is designed to work best in static networks. The protocol’s routing mechanisms, which rely on the selection of preferred parent nodes, struggle to adapt to the frequent changes in network topology, leading to suboptimal routing decisions and decreased overall performance.
The nPSIR Protocol: Addressing Mobility and Energy Efficiency
To overcome the limitations of RPL in mobile IoT networks, researchers have proposed the Network Performance Stability using the Intelligent Routing (nPSIR) protocol. nPSIR is designed to provide seamless and uninterrupted connectivity during node mobility while also optimizing energy consumption.
The key features of the nPSIR protocol include:
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Unrestricted Mobility: Unlike RPL, which limits node mobility to leaf nodes, nPSIR allows the unrestricted movement of any node within the DAG, as long as it remains within the boundaries of the low-power and lossy network.
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Seamless Connectivity: The nPSIR protocol employs a dynamic trickle timer mechanism and a neighbor link quality table to ensure that the network maintains continuous connectivity during node mobility, minimizing the risk of data loss and disconnection.
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Efficient Parent Selection: nPSIR utilizes a sophisticated parent node selection algorithm that considers factors such as link quality, node confidence, and critical region identification to choose the most beneficial parent node, even in the event of node migration.
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Multipath Routing: The nPSIR protocol establishes multiple alternative paths between the source and destination nodes, ensuring that data can be transmitted through diverse routes. This approach enhances reliability, load balancing, and congestion control.
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Energy-Aware Design: nPSIR incorporates energy-efficient mechanisms, such as a blacklist and a genetic fitness-based approach, to minimize energy consumption and prolong the network’s lifetime.
Performance Evaluation and Comparison
To assess the effectiveness of the nPSIR protocol, the researchers conducted extensive simulations using the NS2 simulator, comparing its performance with other state-of-the-art routing protocols, including mPRL, GI-RPL, Mobi-RPL, and ARMOR.
The performance evaluation focused on several key metrics, including:
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Packet Delivery Ratio (PDR): The nPSIR protocol demonstrated a higher PDR compared to the other routing protocols, particularly in high-speed mobile scenarios. The PDR of nPSIR surpassed mPRL, GI-RPL, Mobi-RPL, and ARMOR by 5.97%, 10.7%, and 7.79%, respectively.
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End-to-End Delay (E2ED): The nPSIR protocol exhibited a significantly lower E2ED, with a 48.9%, 53.05%, and 51.5% reduction compared to mPRL, GI-RPL, Mobi-RPL, and ARMOR, respectively.
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Throughput: The nPSIR protocol outperformed the other routing protocols in terms of throughput, achieving a 13.1%, 9.28%, and 22.5% improvement over mPRL, GI-RPL, and Mobi-RPL, respectively.
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Routing Overhead: The nPSIR protocol demonstrated a lower Network Routing Overhead (NRO) as the number of nodes increased, indicating its ability to efficiently manage network traffic and control signaling.
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Energy Consumption: The nPSIR protocol’s energy-aware design, including the use of a blacklist and a genetic fitness-based approach, resulted in lower average energy consumption compared to the other routing protocols, especially in high-speed scenarios.
The simulation results clearly showcased the superior performance of the nPSIR protocol in terms of packet delivery, end-to-end delay, throughput, routing overhead, and energy efficiency, making it a compelling choice for IoT applications with dynamic network topologies and mobility requirements.
Conclusion and Future Directions
The nPSIR protocol addresses the key limitations of the RPL routing protocol in mobile IoT networks. By enabling unrestricted node mobility, ensuring seamless connectivity, implementing efficient parent selection mechanisms, and incorporating multipath routing and energy-aware design, nPSIR has demonstrated its effectiveness in improving the overall performance and reliability of IoT sensor networks.
The comprehensive simulation results highlight the advantages of nPSIR over other state-of-the-art routing protocols, such as mPRL, GI-RPL, Mobi-RPL, and ARMOR, in terms of critical parameters like packet delivery ratio, end-to-end delay, throughput, routing overhead, and energy consumption.
As the IoT landscape continues to evolve, with increasing demands for mobile and real-time applications, the nPSIR protocol presents a promising solution to the challenges faced by traditional routing protocols. By seamlessly integrating mobility support, energy efficiency, and reliable data transmission, nPSIR paves the way for enhanced performance and longevity in IoT sensor networks.
Future research directions may focus on further optimizing the nPSIR protocol, exploring its applicability in diverse IoT use cases, and investigating its integration with emerging technologies, such as edge computing and 5G/6G networks, to address the ever-growing demands of the IoT ecosystem.
