NS3 LTE基于X2接口的内部切换

相比较上一篇含有EPC网络的LTE仿真程序，本文又增加了基于X2接口的内部切换仿真流程。下面将是这样的网络拓扑：

一个UE，两个eNB，一个作为源基站，一个作为切换基站

#include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/internet-module.h"
#include "ns3/mobility-module.h"
#include "ns3/lte-module.h"
#include "ns3/applications-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/config-store-module.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE ("LenaX2HandoverExample");
//Define Trace sinks function
void
NotifyConnectionEstablishedUe (std::string context,
                               uint64_t imsi,
                               uint16_t cellid,
                               uint16_t rnti)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " UE IMSI " << imsi
            << ": connected to CellId " << cellid
            << " with RNTI " << rnti
            << std::endl;
}

void
NotifyHandoverStartUe (std::string context,
                       uint64_t imsi,
                       uint16_t cellid,
                       uint16_t rnti,
                       uint16_t targetCellId)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " UE IMSI " << imsi
            << ": previously connected to CellId " << cellid
            << " with RNTI " << rnti
            << ", doing handover to CellId " << targetCellId
            << std::endl;
}

void
NotifyHandoverEndOkUe (std::string context,
                       uint64_t imsi,
                       uint16_t cellid,
                       uint16_t rnti)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " UE IMSI " << imsi
            << ": successful handover to CellId " << cellid
            << " with RNTI " << rnti
            << std::endl;
}

void
NotifyConnectionEstablishedEnb (std::string context,
                                uint64_t imsi,
                                uint16_t cellid,
                                uint16_t rnti)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " eNB CellId " << cellid
            << ": successful connection of UE with IMSI " << imsi
            << " RNTI " << rnti
            << std::endl;
}

void
NotifyHandoverStartEnb (std::string context,
                        uint64_t imsi,
                        uint16_t cellid,
                        uint16_t rnti,
                        uint16_t targetCellId)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " eNB CellId " << cellid
            << ": start handover of UE with IMSI " << imsi
            << " RNTI " << rnti
            << " to CellId " << targetCellId
            << std::endl;
}

void
NotifyHandoverEndOkEnb (std::string context,
                        uint64_t imsi,
                        uint16_t cellid,
                        uint16_t rnti)
{
  std::cout << Simulator::Now ().GetSeconds () << " " << context
            << " eNB CellId " << cellid
            << ": completed handover of UE with IMSI " << imsi
            << " RNTI " << rnti
            << std::endl;
}


/**
 * Sample simulation script for a X2-based handover.
 * It instantiates two eNodeB, attaches one UE to the 'source' eNB and
 * triggers a handover of the UE towards the 'target' eNB.
 */
int
main (int argc, char *argv[])
{
  // LogLevel logLevel = (LogLevel)(LOG_PREFIX_FUNC | LOG_PREFIX_TIME | LOG_LEVEL_ALL);

  // LogComponentEnable ("LteHelper", logLevel);
  // LogComponentEnable ("EpcHelper", logLevel);
  // LogComponentEnable ("EpcEnbApplication", logLevel);
  // LogComponentEnable ("EpcX2", logLevel);
  // LogComponentEnable ("EpcSgwPgwApplication", logLevel);

  // LogComponentEnable ("LteEnbRrc", logLevel);
  // LogComponentEnable ("LteEnbNetDevice", logLevel);
  // LogComponentEnable ("LteUeRrc", logLevel);
  // LogComponentEnable ("LteUeNetDevice", logLevel);

  uint16_t numberOfUes = 1;
  uint16_t numberOfEnbs = 2;
  uint16_t numBearersPerUe = 2;
  double simTime = 0.300;
  double distance = 100.0;

  // change some default attributes so that they are reasonable for
  // this scenario, but do this before processing command line
  // arguments, so that the user is allowed to override these settings
  Config::SetDefault ("ns3::UdpClient::Interval", TimeValue (MilliSeconds (10)));
  Config::SetDefault ("ns3::UdpClient::MaxPackets", UintegerValue (1000000));
  Config::SetDefault ("ns3::LteHelper::UseIdealRrc", BooleanValue (false));

  // Command line arguments
  CommandLine cmd;
  cmd.AddValue ("numberOfUes", "Number of UEs", numberOfUes);
  cmd.AddValue ("numberOfEnbs", "Number of eNodeBs", numberOfEnbs);
  cmd.AddValue ("simTime", "Total duration of the simulation (in seconds)", simTime);
  cmd.Parse (argc, argv);


  Ptr lteHelper = CreateObject ();
  Ptr epcHelper = CreateObject ();
  lteHelper->SetEpcHelper (epcHelper);//告诉lte 含有epc
  lteHelper->SetSchedulerType ("ns3::RrFfMacScheduler");
  lteHelper->SetHandoverAlgorithmType ("ns3::NoOpHandoverAlgorithm"); // disable automatic handover,选择切换算法,A2A4RsrpHandoverAlgorithm A3RsrpHandoverAlgorithm
//epcHelper自动创建和配置PGW，下面取出PGW
  Ptr pgw = epcHelper->GetPgwNode ();

  // Create a single RemoteHost
  NodeContainer remoteHostContainer;
  remoteHostContainer.Create (1);
  Ptr remoteHost = remoteHostContainer.Get (0);
  InternetStackHelper internet;
  internet.Install (remoteHostContainer);

  // Create the Internet
  PointToPointHelper p2ph;
  p2ph.SetDeviceAttribute ("DataRate", DataRateValue (DataRate ("100Gb/s")));
  p2ph.SetDeviceAttribute ("Mtu", UintegerValue (1500));
  p2ph.SetChannelAttribute ("Delay", TimeValue (Seconds (0.010)));
  NetDeviceContainer internetDevices = p2ph.Install (pgw, remoteHost);//在remoteHost pgw安装P2P设备
  Ipv4AddressHelper ipv4h;
  ipv4h.SetBase ("1.0.0.0", "255.0.0.0");
  Ipv4InterfaceContainer internetIpIfaces = ipv4h.Assign (internetDevices);//为 remoteHostStaticRouting pgw分配IP
  Ipv4Address remoteHostAddr = internetIpIfaces.GetAddress (1);//取得remotehost IP


  // Routing of the Internet Host (towards the LTE network)
  Ipv4StaticRoutingHelper ipv4RoutingHelper;
  Ptr remoteHostStaticRouting = ipv4RoutingHelper.GetStaticRouting (remoteHost->GetObject ());
  // interface 0 is localhost, 1 is the p2p device
  remoteHostStaticRouting->AddNetworkRouteTo (Ipv4Address ("7.0.0.0"), Ipv4Mask ("255.0.0.0"), 1);//UE默认在网络7.0.0.0
//创建LTE接入网节点
  NodeContainer ueNodes;
  NodeContainer enbNodes;
  enbNodes.Create (numberOfEnbs);
  ueNodes.Create (numberOfUes);

  // Install Mobility Model
  Ptr positionAlloc = CreateObject ();
  for (uint16_t i = 0; i < numberOfEnbs; i++)
    {
      positionAlloc->Add (Vector (distance * 2 * i - distance, 0, 0));//enb初始位置（distance*2i-distance,0,0）
    }
  for (uint16_t i = 0; i < numberOfUes; i++)
    {
      positionAlloc->Add (Vector (0, 0, 0));//UE初始位置（0,0,0）
    }
  MobilityHelper mobility;
  mobility.SetMobilityModel ("ns3::ConstantPositionMobilityModel");
  mobility.SetPositionAllocator (positionAlloc);
  mobility.Install (enbNodes);
  mobility.Install (ueNodes);

  // Install LTE Devices in eNB and UEs
  NetDeviceContainer enbLteDevs = lteHelper->InstallEnbDevice (enbNodes);
  NetDeviceContainer ueLteDevs = lteHelper->InstallUeDevice (ueNodes);

  // Install the IP stack on the UEs
  internet.Install (ueNodes);
  Ipv4InterfaceContainer ueIpIfaces;
  ueIpIfaces = epcHelper->AssignUeIpv4Address (NetDeviceContainer (ueLteDevs));
  //建立网关在下面循环里

  // Attach all UEs to the first eNodeB
  for (uint16_t i = 0; i < numberOfUes; i++)
    {
      lteHelper->Attach (ueLteDevs.Get (i), enbLteDevs.Get (0));//指定所有UE关联到enbdev(0)
    }
//未指定承载则默认EPS承载将会建立

  NS_LOG_LOGIC ("setting up applications");//控制台输出提醒开始安装app

  // Install and start applications on UEs and remote host
  uint16_t dlPort = 10000;
  uint16_t ulPort = 20000;

  // randomize a bit start times to avoid simulation artifacts
  // (e.g., buffer overflows due to packet transmissions happening
  // exactly at the same time)
  Ptr startTimeSeconds = CreateObject ();
  startTimeSeconds->SetAttribute ("Min", DoubleValue (0));
  startTimeSeconds->SetAttribute ("Max", DoubleValue (0.010));

  for (uint32_t u = 0; u < numberOfUes; ++u)
    {
      Ptr ue = ueNodes.Get (u);
      // Set the default gateway for the UE
      Ptr ueStaticRouting = ipv4RoutingHelper.GetStaticRouting (ue->GetObject ());
      ueStaticRouting->SetDefaultRoute (epcHelper->GetUeDefaultGatewayAddress (), 1);

      for (uint32_t b = 0; b < numBearersPerUe; ++b)
        {
          ++dlPort;
          ++ulPort;

          ApplicationContainer clientApps;
          ApplicationContainer serverApps;

          NS_LOG_LOGIC ("installing UDP DL app for UE " << u);
          UdpClientHelper dlClientHelper (ueIpIfaces.GetAddress (u), dlPort);//dl 目的 Usr
          clientApps.Add (dlClientHelper.Install (remoteHost));//客户端是remotehost
          PacketSinkHelper dlPacketSinkHelper ("ns3::UdpSocketFactory",
                                               InetSocketAddress (Ipv4Address::GetAny (), dlPort));
          serverApps.Add (dlPacketSinkHelper.Install (ue));

          NS_LOG_LOGIC ("installing UDP UL app for UE " << u);
          UdpClientHelper ulClientHelper (remoteHostAddr, ulPort);//ul 目的 remoteHost
          clientApps.Add (ulClientHelper.Install (ue));
          PacketSinkHelper ulPacketSinkHelper ("ns3::UdpSocketFactory",
                                               InetSocketAddress (Ipv4Address::GetAny (), ulPort));
          serverApps.Add (ulPacketSinkHelper.Install (remoteHost));

          Ptr tft = Create ();
          EpcTft::PacketFilter dlpf;
          dlpf.localPortStart = dlPort;
          dlpf.localPortEnd = dlPort;
          tft->Add (dlpf);
          EpcTft::PacketFilter ulpf;
          ulpf.remotePortStart = ulPort;
          ulpf.remotePortEnd = ulPort;
          tft->Add (ulpf);
          EpsBearer bearer (EpsBearer::NGBR_VIDEO_TCP_DEFAULT);
          lteHelper->ActivateDedicatedEpsBearer (ueLteDevs.Get (u), bearer, tft);//不再是默认EPS承载而是专用承载

          Time startTime = Seconds (startTimeSeconds->GetValue ());//随机开始
          serverApps.Start (startTime);
          clientApps.Start (startTime);

        } // end for bearer
    }//end for Usr


  // Add X2 inteface
  lteHelper->AddX2Interface (enbNodes);//至少两个enb，每两个之间加入X2

  // X2-based Handover
  lteHelper->HandoverRequest (Seconds (0.100), ueLteDevs.Get (0), enbLteDevs.Get (0), enbLteDevs.Get (1));//人工触发切换

  // Uncomment to enable PCAP tracing
  //p2ph.EnablePcapAll("lena-x2-handover");

  lteHelper->EnablePhyTraces ();
  lteHelper->EnableMacTraces ();
  lteHelper->EnableRlcTraces ();
  lteHelper->EnablePdcpTraces ();
  Ptr rlcStats = lteHelper->GetRlcStats ();
  rlcStats->SetAttribute ("EpochDuration", TimeValue (Seconds (0.05)));
  Ptr pdcpStats = lteHelper->GetPdcpStats ();
  pdcpStats->SetAttribute ("EpochDuration", TimeValue (Seconds (0.05)));


  // connect custom trace sinks for RRC connection establishment and handover notification
  Config::Connect ("/NodeList/*/DeviceList/*/LteEnbRrc/ConnectionEstablished",
                   MakeCallback (&NotifyConnectionEstablishedEnb));
  Config::Connect ("/NodeList/*/DeviceList/*/LteUeRrc/ConnectionEstablished",
                   MakeCallback (&NotifyConnectionEstablishedUe));
  Config::Connect ("/NodeList/*/DeviceList/*/LteEnbRrc/HandoverStart",
                   MakeCallback (&NotifyHandoverStartEnb));
  Config::Connect ("/NodeList/*/DeviceList/*/LteUeRrc/HandoverStart",
                   MakeCallback (&NotifyHandoverStartUe));
  Config::Connect ("/NodeList/*/DeviceList/*/LteEnbRrc/HandoverEndOk",
                   MakeCallback (&NotifyHandoverEndOkEnb));
  Config::Connect ("/NodeList/*/DeviceList/*/LteUeRrc/HandoverEndOk",
                   MakeCallback (&NotifyHandoverEndOkUe));
//利用类Config的一个静态成员函数Connect将二者关联source sink ,MakeCallback 使参数函数变成回调函数

  Simulator::Stop (Seconds (simTime));
  Simulator::Run ();

  // GtkConfigStore config;
  // config.ConfigureAttributes ();

  Simulator::Destroy ();
  return 0;

}

以上实现了通过默认EPS承载建立起UE到远程网络remotehost之间的通信。