给出一个基于NS-3的WIFI性能仿真的代码

以下是一个基于NS-3的WIFI性能仿真代码示例：

#include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/wifi-module.h"
#include "ns3/mobility-module.h"
#include "ns3/internet-module.h"
#include "ns3/applications-module.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE ("WifiPerformance");

int main (int argc, char *argv[])
{
  // Enable logging
  LogComponentEnable ("WifiPerformance", LOG_LEVEL_INFO);

  // Create nodes
  NodeContainer nodes;
  nodes.Create (2);

  // Create wifi channel
  WifiHelper wifi;
  wifi.SetStandard (WIFI_PHY_STANDARD_80211n_5GHZ);
  wifi.SetRemoteStationManager ("ns3::ConstantRateWifiManager",
                                "DataMode", StringValue ("HtMcs7"),
                                "ControlMode", StringValue ("HtMcs0"));

  // Create wifi devices
  NetDeviceContainer devices;
  devices = wifi.Install (WifiHelper::CreateWifiPhyMac (nodes));

  // Set wifi channel attributes
  Ptr<YansWifiChannel> channel = CreateObject<YansWifiChannel> ();
  channel->SetPropagationDelayModel (CreateObject<ConstantSpeedPropagationDelayModel> ());
  channel->SetPropagationDelay (NanoSeconds (500));
  channel->SetChannelNumber (36);

  // Create mobility model
  MobilityHelper mobility;
  Ptr<ListPositionAllocator> positionAlloc = CreateObject<ListPositionAllocator> ();
  positionAlloc->Add (Vector (0.0, 0.0, 0.0));
  positionAlloc->Add (Vector (50.0, 0.0, 0.0));
  mobility.SetPositionAllocator (positionAlloc);
  mobility.SetMobilityModel ("ns3::ConstantPositionMobilityModel");
  mobility.Install (nodes);

  // Create internet stack
  InternetStackHelper stack;
  stack.Install (nodes);

  // Assign IP addresses
  Ipv4AddressHelper address;
  address.SetBase ("10.1.1.0", "255.255.255.0");
  Ipv4InterfaceContainer interfaces = address.Assign (devices);

  // Create UDP application
  uint16_t port = 10000;
  UdpServerHelper server (port);
  ApplicationContainer serverApps = server.Install (nodes.Get (0));
  serverApps.Start (Seconds (0.0));
  serverApps.Stop (Seconds (10.0));

  UdpClientHelper client (interfaces.GetAddress (0), port);
  client.SetAttribute ("MaxPackets", UintegerValue (100));
  client.SetAttribute ("Interval", TimeValue (Seconds (0.1)));
  client.SetAttribute ("PacketSize", UintegerValue (1024));
  ApplicationContainer clientApps = client.Install (nodes.Get (1));
  clientApps.Start (Seconds (1.0));
  clientApps.Stop (Seconds (10.0));

  // Configure tracing
  AsciiTraceHelper ascii;
  wifi.EnableAsciiAll (ascii.CreateFileStream ("wifi-performance.tr"));

  // Run simulation
  Simulator::Stop (Seconds (10.0));
  Simulator::Run ();
  Simulator::Destroy ();

  return 0;
}

该示例包括创建节点、设置WIFI通道、创建移动模型、设置IP地址、创建UDP应用程序和配置跟踪等步骤。其中，通过设置不同的参数，可以模拟不同的WIFI性能情况。