Hi Ricardo, the obvious answer - the number of events to process is very different. But why? First of all, the different propagation models result in different transmission ranges. And greater transmission range results in a larger number of nodes receiving an event and hence more processing time required. You can check this by counting the number of events in the event trace. Second, when you start your simulation it should print a line containing "distCST_ = 550.0". This is the maximum range one node can affect another one (carrier sense). If it is unknown you will see a really huge number. This value is used to optimize the propagation computation because nodes further away do not need to be considered during the transmission of a packet. So, larger values will increase computation time. Third, even if you set the transmission range of different models to the same value you will get different event counts. The reason is that all models produce different carrier sense to transmission range ratios. That means, equal transmission ranges will result in different carrier sense ranges that obviousely results in a different behavior of your simulation.
Daniel. Ricardo Ulisses schrieb: > Hi all, > > I've been doing research on large mobile ad hoc network simulation, so > far using Two-Ray Ground radio wave propagation model. I suppose I was > achieving a reasonable amount of time to fully complete a simulation > run with 10k nodes with 3k connections between them during 300 seconds > of simulation time (about 2 days and a half). > > Now I've switched to the FreeSpace propagation model and I've noticed > that the time to process the simulation largely increased. > > Let me show some small scale network examples: > > 1) Simulating 10 nodes, 3 connections between them, 300s simulation time: > > FreeSpace..............1m3.232s > TwoRayGround........0m0.500s > > 2) Simulating 100 nodes, 30 connections between them, 300s simulation time: > > FreeSpace..............more than 30 minutes > TwoRayGround........1m11.207s > > I've also made some simulations using the Shadowing model and the time > spent was very close to the ones obtained when using the TwoRayGround > model. > > I am really surprised with the high time consumption of the simulation > run using FreeSpace model as it is a much less complex model than > TwoRayGround and Shadowing. > > Does anyone have any clue about the reason why this is happening? > > Yes, I've read the FAQ, ns-problems page, and manual and I couldn't > find the answer there neither in any other document or website. > > Please, ask me if more information about how the simulation is > configured is needed. > > Thanks in advance. > > Ricardo J. Ulisses Filho > ================================================= > Departamento de Sistemas e Computacão - DSC > Universidade de Pernambuco - UPE > Recife - Pernambuco - Brazil > [EMAIL PROTECTED] > [EMAIL PROTECTED] > >
