Acknowledgements in 802.11p

[D G]

Hello everyone,
I have a rather simple question.
And maybe I am missing something that would help me, but is the current 802.11p model regarding acknowledgements properly?
Because I see any backup or resend happening when an ack is missing.
Or do I have to explicitly set this behaviour?

Best Regards
D. G.

[D G]

I probobly held some usefull information back.
I used in this scenario the QosWaveMacHelper for mac layer - which should actually support acks due to the fact that inherits from WifiMac.
And of course I am using the Wifi80211pHelper.
Channel and Phy are bot YansWifi...Helper even though I guess it is not necessary.

[Konstantinos]

Hi,

What type of traffic do you sent? Broadcast is not acknowledged by design! 

Regards

K

[D G]

I send packets to a specific IP address (10.1.1.2) not to the bc address (255.255.255.255)
The receiver is - or should be - a sink with the assigned address.

And ,what I just found out, there are some arp requests but it seems that there is no answer to the request.

Do I need to fill the arp cache beforehand?

And thank you for your help again Konstantinos :)

[Konstantinos]

If the node is not in range, hence the ARP is not resolved, then there is no traffic. 

Please provide the scenario (attach).

[D G]

Here is the whole scenario.

If there are further questions I will gladly provide the answers :)

[Konstantinos]

Hi,

Two issues:

1) You have modified the PHY only at one node

 // generate wifiphy for frequency and channelwidth
 Ptr<WifiNetDevice> wifiNetDevice = DynamicCast<WifiNetDevice>(devices.Get(0) );
 Ptr<WifiPhy> wifiPhy = wifiNetDevice->GetPhy();

 // wifiPhy->SetAttribute("ChannelNumber", UintegerValue(172));
 wifiPhy->SetAttribute("Frequency", UintegerValue(5890) );
 wifiPhy->SetAttribute("ChannelWidth", UintegerValue(10) );

Here you modify the PHY only at one NetDevice, which will create disparity among the two nodes. 

There is no need for such configuration, as the 802.11p helper you use sets the appropriate values

41 Wifi80211pHelper

42 Wifi80211pHelper::Default (void)

43 {

44  Wifi80211pHelper helper;

45  helper.SetStandard (WIFI_PHY_STANDARD_80211_10MHZ);

46  helper.SetRemoteStationManager ("ns3::ConstantRateWifiManager",

47  "DataMode", StringValue ("OfdmRate6MbpsBW10MHz"),

48  "ControlMode",StringValue ("OfdmRate6MbpsBW10MHz"),

49  "NonUnicastMode", StringValue ("OfdmRate6MbpsBW10MHz"));

50  return helper;

51 }

2) The second issue is with your packet sink. Currently it only listens to a single unicast IP. Hence the broadcast messages are not received (correctly).

If you want to receive those as well, try the Anycast address when setting up your PacketSink.

[D G]

You are a kind of hero to me.

Learning ns3 is really fun in this community, thank you!