This paper presents the results of a performance comparison between 4 multi-hop wireless ad hoc network routing protocols. This paper also proposed and implemented changes to ns so that it could be used to study multi-hop ad hoc networks.
The 4 protocols that were tested were:
- Destination-Sequenced Distance Vector (DSDV)
- Temporally-Ordered Routing Algorithms
- Dynamic Source Routing (DSR)
- Ad Hoc On-Demand Distance Vector (AODV)
The changes that were made to ns included a model of the physical and data link layer. The link layer implements the MAC protocol. There was also an implementation of ARP to resolve IP address to link layer addresses. Finally, each protocol has a packet buffer of max size 50 packets.
The authors ran a simulation of 50 nodes on ns to see how each protocol would react to changes in the network topology. The simulation was run using 3 different CBR sources in order to approximate 3 different data sending rates.
They chose the following 3 metrics to evaluate the simulation results:
- packet delivery rate
- routing overhead
- path optimality
When evaluating path delivery rate, DSR and AODV-LL were found to have the best performance at all pause times. TORA performs a little worse, and while DSDV-SQ performs better than TORA when pause time is over 300 ms, it fails to converge at pause times below 300 ms.
When evaluating routing overhead, DSR was found to have the lowest number of overhead packets while AODV-LL was found to have a slightly higher number of overhead packets. However, when looking at the number of overhead bytes, AODV-LL actually has the smallest number of total overhead bytes.
When evaluating path optimality, DSR and DSDV-SQ were found to use routes close to the optimal, while AODV-LL and TORA used routes that were sometimes 4 hops longer than optimal.
Criticism & Questions
I think this paper was interesting to read. The simulation results do suggest many differences between the 4 protocols and would be informative to those choosing between them. However, since these are purely simulation results, I wonder how accurate they are. One of the features of ad-hoc networks is their unpredictability, and without doing a real deployment, I'm not sure how accurately you can test the various protocols.
The authors didn't include a future works section, but I would really like to see the results of a real deployment as the next step.
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