# Vortex: Network-Driven Opportunistic Routing for Ad Hoc Networks
## 4 Performance Evaluation  
### Simulation Setups  
In this paper, we evaluate the performance of VORTEX by comparing it to other routing protocols using simulations. The comparison is made with AODV [3], ExOR [18; 19], HRAN [16], LCAR [20], SOAR [11], OxDSR [17], and CHOR [14]. Here, AODV and ExOR are chosen as benchmark protocols since they are the fundamental protocols in ad hoc networks, and HRAN, LCAR, SOAR, OxDSR, and CHOR are chosen since they use a strategy similar to VORTEX that creates a guide for packet forwarding. The simulation setups are described in the following. Note that we use UDP traffic and IEEE 802.11b as the wireless medium to evaluate mainly routing performance since TCP's performance  
Figure 2: Forwarding in VORTEX. in MANET is strongly affected by its vulnerable wireless communication nature and its recovery mechanisms blur the pure routing performance. Thus, we avoid the use of rich protocols in other layers to focus on the routing performance. **Common environment:** We use QualNet [28] 6.1 as the network simulator. In the simulations, terminals are randomly placed in 1000 m \(\times\) 1000 m square simulation areas and each terminal uses IEEE 802.11b and disabled RTS/CTS mechanism for broadcast-based ORs. The transmission rate is set to 11 Mbps, and the radio range is approximately set to a radius of 100 m. Note that, radio signals attenuate as the distance between the source and receiver increases, and the former radius indicates the threshold at which terminals can correctly receive the packet. Source and destination terminal pairs are randomly chosen from the entire network and bidirectional UDP traffic for 1000 packets of 1024 kbytes is forwarded between the pair terminals in a single forwarding attempt. The traffic generation rate is set to two pairs per second for the duration of the simulations, namely 1000 s. The mobility is defined by RWP (random waypoint) strategy with the pause time set to 0 s. In addition, we use the default values defined in AODV for the HELLO message broadcast interval, route timeout, and allowed HELLO message loss. In other words, HELLO messages are broadcasted every 1 s, and the update interval \(i\) of VORTEX is set to \(i=5\). The rebroadcast probability \(p\) in VORTEX is set to \(p=0.5\) in all simulations. In this performance evaluation, we conducted the following three simulations. **Simulation 1** and **2** are conducted to evaluate general routing performance varying terminal density and mobility, and **Simulation 3** evaluates the routing performance varying an information distribution. **Simulation 1:** In **Simulation 1**, we evaluate the performance of each protocol in terms of terminal density. In this simulation, the number of terminals in the area is changed from 100 to 1000 terminals every 100 steps. The moving speed of the terminals is randomly chosen from 0 m/s to 5 m/s. **Simulation 2:** In **Simulation 2**, we evaluate the performance from the viewpoint of topology dynamics. In this simulation, 1000 terminals are randomly placed in the simulation area and the moving speed of terminals is fixed and set to 0 m/s to 10 m/s at every 1 m/s step. **Simulation 3:** In **Simulation 3**, we adopt an information distribution scenario to evaluate the routing performance in a specific application environment. In this simulation, 1000 terminals are randomly placed in the simulation area and the moving speed of the terminal is randomly chosen from 0 m/s to 2 m/s to simulate ambulation. The distribution source is randomly chosen from the whole terminal and the ratio of the source to the entire terminal is changed from 1% to 10%, that is, from 10 terminals to 100 terminals. Through these simulations, we evaluate the routing protocols from the following aspects: (a) packet delivery ratio, (b) average end-to-end delay, (c) average hop count, and (d) energy consumption. The packet delivery ratio represents the reliability of the routing protocols and is calculated as a percentage of the successful packet delivery to the total packet forwarding.