NS-3 is well-known for its strong capabilities in handling multiple network interface cards and its efficient IP addressing strategies. To enhance the performance of MANET routing protocols, the NS-3 simulation tool is utilized to analyze these protocols and provide a detailed guide on building an NS-3 simulation platform. The study compares the end-to-end average delay and delivery rate of AODV, DSDV, and OLSR routing protocols from the perspectives of network scale and dynamic topology. The simulation results offer a solid foundation for future protocol optimization and improvements.
0. Preface
With the rapid advancement of network and communication technologies, researchers face challenges in studying large-scale networks without physical hardware, designing new protocols quickly, and comparing old and new systems without costly real-world implementations. In recent years, network simulation has become a popular approach, allowing researchers to simulate network protocols, topologies, and performance through software. This method reduces costs, increases flexibility, and improves research efficiency. Mainstream tools include OPNET, QualNet, and NS-2. However, OPNET and QualNet are commercial, with limited model libraries and less focus on network layering. NS-2, while powerful, is complex and difficult to expand due to tight module coupling. To address these limitations, Professor Thmos R. Henderson and his team at the University of Washington developed NS-3, an open-source alternative. NS-3 excels in multi-NIC processing and IP addressing, features a clearer architecture, and allows direct migration to real network nodes, making it highly customizable for researchers.
1. MANET Routing Protocol Analysis
Mobile Ad Hoc Networks (MANETs) are decentralized, self-organized, multi-hop wireless networks that are widely used in scenarios like disaster relief and military operations. The quality of the routing protocol significantly impacts overall network performance. This paper briefly introduces three commonly used flat routing protocols: DSDV, AODV, and OLSR.
DSDV is a table-driven protocol based on the traditional Distance Vector (DV) algorithm. It adds a destination sequence number to distinguish between old and new routing information. Nodes compare received data and update their routing tables accordingly. Periodic broadcasts maintain routes across the network.
AODV is a source-initiated protocol that combines elements of DSR and DSDV. When a node needs to send data, it first checks its routing table. If no route exists, it broadcasts a Route Request (RREQ) packet. Neighbors forward the RREQ until a path is found, after which a Route Reply (RREP) is sent back. AODV also uses Hello packets for route maintenance and sends Error messages when links break.
OLSR is an optimized link-state protocol that uses Multi-Point Relays (MPRs) to reduce overhead. Only MPR nodes broadcast control packets, while others do not participate in routing calculations. HELLO and Topology Control (TC) messages help nodes detect neighbors and build the network topology. Each node then calculates the shortest path using the Dijkstra algorithm.
2. Building the NS-3 Simulation Platform
2.1 NS-3 Simulation Architecture
NS-3 is a discrete-event simulator composed of two main components: the simulator core and network components. The core includes a time scheduler and a network simulation support system, which is the heart of the tool. Unlike NS-2, NS-3 supports both the default and real-time schedulers, offering greater flexibility.
The network simulation support system includes attribute management, logging, and tracing systems, ensuring transparency and scalability. The network components consist of nodes, applications, protocol stacks, network devices, channels, and topology builders. These components are designed with low coupling and high cohesion, enabling accurate modeling of real-world networks.
Figure 1 shows the NS-3 architecture, while Figure 2 illustrates the relationship between the number of nodes and delay.
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