Re: [ns] [Ns-developers] transmission range in wifi network
Hi all, Thank you Mathieu. * * 2009/4/9 Mathieu Lacage mathieu.lac...@sophia.inria.fr On Mon, 2009-04-06 at 19:34 +0200, ichrak amdouni wrote: Hi all, I need to fix the transmission range for access points and mobile stations in an infrastructure wifi network. I mean, how to manage to let communication restricted to a given distance? I know that in the ns3.3 version, this parameter is not explicitly set, but affected by others like the TxPower and the channel loss model, but actually, I experimented multiple matching between those parameters but I have always stange results (a sta can affiliate with an APdistant of thousands of meters!!). I doubt that is the case with the default values of all parameters. Maybe you changed some parameters ? Yes, it is the case, the mac association succeed between an access point and one mobile station distant of 3000m, connectivity is however not maintained. Note that my nodes simulates vehicles running at 50km/h. Having distinct results from those of the wifi-phy-test.cc example, I wonder if this issue has a relation with other layers other than the Physical one? No, it's all a PHY layer thing. I find the hypothesis very stange but I really reproduced the same scenario as in wifi-phy-test.cc. What kind of scenario ? Could you be more explicit about what you, what you get, and what you expect from wifi-phy-test ? I am expecting to have nodes that can't see each other beyond the theoretical coverage area. For example I used the following setting: *channel.AddPropagationLoss(ns3::LogDistancePropagationLossModel,Exponent, DoubleValue(1.70)); channel.SetPropagationDelay (ns3::ConstantSpeedPropagationDelayModel); PtrYansWifiChannel chan = channel.Create (); ** wifiPhy.SetChannel (chan);* * wifiPhy.SetErrorRateModel (ns3::ErrorRateModel); wifiPhy.Set (TxPowerStart,DoubleValue(5)); wifiPhy.Set (TxPowerEnd,DoubleValue(5)); wifiPhy.Set (TxPowerLevels,UintegerValue (1)); wifiPhy.Set (TxGain,DoubleValue (2)); wifiPhy.Set (RxGain,DoubleValue (2)); *This make connection impossible beyond 250m, but the problem now is that packet transfert failure is important due to the condition:* (m_random.GetValue () snrPer.per** ) *at the physical layer when sending probe responses.* * May I missing something? - Did someone experiment this issue especially in high mobiliy network? or have an idea to deal with it differently? - Is the transmission range explicitly set in ns 3.4? If yes, which files were modified? No, ns-3.4 has no support for this. A patch to add a range-based PHY model would be welcome. Mathieu Best Regards. Ichrak.
Re: [ns] [Ns-developers] transmission range in wifi network
On Thu, 2009-04-09 at 15:59 +0200, ichrak amdouni wrote: I doubt that is the case with the default values of all parameters. Maybe you changed some parameters ? Yes, it is the case, the mac association succeed between an access point and one mobile station distant of 3000m, connectivity is however not maintained. Note that my nodes simulates vehicles running at 50km/h. As I said, I don't believe that the default parameter values allow any kind of packet reception at 3000m. Here is what I get with ns-3-dev from today: [mlac...@diese ns-3-dev]$ ./build/debug/src/devices/wifi/wifi-phy-test Psr --PacketSize=40 --TxMode=wifia-6mbs --Distance=3000 0 or: [mlac...@diese ns-3-dev]$ ./build/debug/src/devices/wifi/wifi-phy-test SizeVsRange --TargetPsr=0.0001 --TxMode=wifia-6mbs 10 199.125 50 189.214 90 182.218 130 177.554 170 174.639 210 171.918 250 172.307 290 170.947 330 169.586 370 168.226 ... To summmarize, the default parameter setup and values ensure that the probability of successful reception of packets 10bytes-long by the PHY with mode 6mbs is close to zero after 200m. If you don't get this, then, either you have a very broken version of ns-3 or you have changed some default parameter, but I have no idea which. Or, I could be wrong, but I don't have enough information to reproduce the behavior you are describing. Having distinct results from those of the wifi-phy-test.cc example, I wonder if this issue has a relation with other layers other than the Physical one? No, it's all a PHY layer thing. I find the hypothesis very stange but I really reproduced the same scenario as in wifi-phy-test.cc. What kind of scenario ? Could you be more explicit about what you, what you get, and what you expect from wifi-phy-test ? I am expecting to have nodes that can't see each other beyond the theoretical coverage area. For example I used the following setting: what is the 'theoretical' coverage area ? channel.AddPropagationLoss(ns3::LogDistancePropagationLossModel,Exponent, DoubleValue(1.70)); channel.SetPropagationDelay (ns3::ConstantSpeedPropagationDelayModel); PtrYansWifiChannel chan = channel.Create (); wifiPhy.SetChannel (chan); wifiPhy.SetErrorRateModel (ns3::ErrorRateModel); wifiPhy.Set (TxPowerStart,DoubleValue(5)); wifiPhy.Set (TxPowerEnd,DoubleValue(5)); wifiPhy.Set (TxPowerLevels,UintegerValue (1)); wifiPhy.Set (TxGain,DoubleValue (2)); wifiPhy.Set (RxGain,DoubleValue (2)); This make connection impossible beyond 250m, but the problem now is that packet transfert failure is important due to the condition: (m_random.GetValue () snrPer.per ) at the physical layer when sending probe responses. I am not sure what you are trying to achieve. Theoretically, all you need to do to adjust the transmission range is to change the tx power. Mathieu
