A Discrete-Event Network Simulator
API
lte-test-rr-ff-mac-scheduler.cc
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1 /* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
2 /*
3  * Copyright (c) 2011, 2012 Centre Tecnologic de Telecomunicacions de Catalunya (CTTC)
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation;
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17  *
18  * Author: Marco Miozzo <marco.miozzo@cttc.es>
19  * Nicola Baldo <nbaldo@cttc.es>
20  */
21 
22 #include <ns3/object.h>
23 #include <ns3/spectrum-interference.h>
24 #include <ns3/spectrum-error-model.h>
25 #include <ns3/log.h>
26 #include <ns3/test.h>
27 #include <ns3/simulator.h>
28 #include <ns3/packet.h>
29 #include <ns3/ptr.h>
30 #include <iostream>
31 #include "ns3/radio-bearer-stats-calculator.h"
32 #include <ns3/constant-position-mobility-model.h>
33 #include <ns3/eps-bearer.h>
34 #include <ns3/node-container.h>
35 #include <ns3/mobility-helper.h>
36 #include <ns3/net-device-container.h>
37 #include <ns3/lte-ue-net-device.h>
38 #include <ns3/lte-enb-net-device.h>
39 #include <ns3/lte-ue-rrc.h>
40 #include <ns3/lte-helper.h>
41 #include "ns3/string.h"
42 #include "ns3/double.h"
43 #include <ns3/lte-enb-phy.h>
44 #include <ns3/lte-ue-phy.h>
45 #include <ns3/boolean.h>
46 #include <ns3/enum.h>
47 #include <ns3/config-store-module.h>
48 
50 
51 using namespace ns3;
52 
53 NS_LOG_COMPONENT_DEFINE ("LenaTestRrFfMacScheduler");
54 
56  : TestSuite ("lte-rr-ff-mac-scheduler", SYSTEM)
57 {
58  NS_LOG_INFO ("creating LenaRrFfMacSchedulerTestCase");
59 
60  bool errorModel = true;
61 
62 
63  // DOWNLINK- DISTANCE 0 -> MCS 28 -> Itbs 26 (from table 7.1.7.2.1-1 of 36.213)
64  // 1 user -> 24 PRB at Itbs 26 -> 2196 -> 2196000 bytes/sec
65  // 3 users -> 8 PRB at Itbs 26 -> 749 -> 749000 bytes/sec
66  // 6 users -> 4 PRB at Itbs 26 -> 373 -> 373000 bytes/sec
67  // 9 user -> 2 PRB at Itbs 26 -> 185 -> 185000 bytes/sec
68  // 12 users -> 2 PRB at Itbs 26 -> 185 -> 185000 bytes/sec
69  // 15 users -> 2 PRB at Itbs 26 * 0.8 -> 148 -> 148000 bytes/sec
70  // UPLINK- DISTANCE 0 -> MCS 28 -> Itbs 26 (from table 7.1.7.2.1-1 of 36.213)
71  // 1 user -> 25 PRB at Itbs 26 -> 2292 -> 2292000 bytes/sec
72  // 3 users -> 8 PRB at Itbs 26 -> 749 -> 749000 bytes/sec
73  // 6 users -> 4 PRB at Itbs 26 -> 373 -> 373000 bytes/sec
74  // after the patch enforcing min 3 PRBs per UE:
75  // 9 users -> 3 PRB at Itbs 26 -> 277 bytes * 8/9 UE/TTI -> 246220 bytes/sec
76  // 12 users -> 3 PRB at Itbs 26 -> 277 bytes * 8/12 UE/TTI -> 184670 bytes/sec
77  // 15 users -> 3 PRB at Itbs 26 -> 277 bytes * 8/15 UE/TTI -> 147730 bytes/sec
78  AddTestCase (new LenaRrFfMacSchedulerTestCase (1,0,2196000,2292000,errorModel), TestCase::EXTENSIVE);
79  AddTestCase (new LenaRrFfMacSchedulerTestCase (3,0,749000,749000,errorModel), TestCase::QUICK);
80  AddTestCase (new LenaRrFfMacSchedulerTestCase (6,0,373000,373000,errorModel), TestCase::EXTENSIVE);
81  AddTestCase (new LenaRrFfMacSchedulerTestCase (9,0,185000,246220,errorModel), TestCase::EXTENSIVE);
82  AddTestCase (new LenaRrFfMacSchedulerTestCase (12,0,185000,184670,errorModel), TestCase::EXTENSIVE);
83  AddTestCase (new LenaRrFfMacSchedulerTestCase (15,0,148000,147730,errorModel), TestCase::EXTENSIVE);
84 
85  // DOWNLINK - DISTANCE 4800 -> MCS 22 -> Itbs 20 (from table 7.1.7.2.1-1 of 36.213)
86  // 1 user -> 24 PRB at Itbs 20 -> 1383 -> 1383000 bytes/sec
87  // 3 users -> 8 PRB at Itbs 20 -> 469 -> 469000 bytes/sec
88  // 6 users -> 4 PRB at Itbs 20 -> 233 -> 233000 bytes/sec
89  // 9 user -> 2 PRB at Itbs 20 -> 113 -> 113000 bytes/sec
90  // 12 users -> 2 PRB at Itbs 20 -> 113 -> 113000 bytes/sec
91  // 15 users -> 2 PRB at Itbs 20 * 0.8 -> 90.4 -> 90400 bytes/sec
92  // UPLINK - DISTANCE 4800 -> MCS 14 -> Itbs 13 (from table 7.1.7.2.1-1 of 36.213)
93  // 1 user -> 25 PRB at Itbs 13 -> 807 -> 807000 bytes/sec
94  // 3 users -> 8 PRB at Itbs 13 -> 253 -> 253000 bytes/sec
95  // 6 users -> 4 PRB at Itbs 13 -> 125 -> 125000 bytes/sec
96  // after the patch enforcing min 3 PRBs per UE:
97  // 9 users -> 3 PRB at Itbs 13 -> 93 bytes * 8/9 UE/TTI -> 82667 bytes/sec
98  // 12 users -> 3 PRB at Itbs 13 -> 93 bytes * 8/12 UE/TTI -> 62000 bytes/sec
99  // 15 users -> 3 PRB at Itbs 13 -> 93 bytes * 8/15 UE/TTI -> 49600 bytes/sec
100  AddTestCase (new LenaRrFfMacSchedulerTestCase (1,4800,1383000,807000,errorModel), TestCase::EXTENSIVE);
101  AddTestCase (new LenaRrFfMacSchedulerTestCase (3,4800,469000,253000,errorModel), TestCase::EXTENSIVE);
102  AddTestCase (new LenaRrFfMacSchedulerTestCase (6,4800,233000,125000,errorModel), TestCase::EXTENSIVE);
103  AddTestCase (new LenaRrFfMacSchedulerTestCase (9,4800,113000,82667,errorModel), TestCase::EXTENSIVE);
104  AddTestCase (new LenaRrFfMacSchedulerTestCase (12,4800,113000,62000,errorModel), TestCase::EXTENSIVE);
105  AddTestCase (new LenaRrFfMacSchedulerTestCase (15,4800,90400,49600,errorModel), TestCase::EXTENSIVE);
106 
107  // DOWNLINK - DISTANCE 6000 -> MCS 20 -> Itbs 18 (from table 7.1.7.2.1-1 of 36.213)
108  // 1 user -> 24 PRB at Itbs 15 -> 1191 -> 1191000 bytes/sec
109  // 3 users -> 8 PRB at Itbs 15 -> 389 -> 389000 bytes/sec
110  // 6 users -> 4 PRB at Itbs 15 -> 193 -> 193000 bytes/sec
111  // 9 user -> 2 PRB at Itbs 15 -> 97 -> 97000 bytes/sec
112  // 12 users -> 2 PRB at Itbs 15 -> 97 -> 97000 bytes/sec
113  // 15 users -> 2 PRB at Itbs 15 * 0.8 -> 77.6 -> 77600 bytes/sec
114  // UPLINK - DISTANCE 6000 -> MCS 12 -> Itbs 11 (from table 7.1.7.2.1-1 of 36.213)
115  // 1 user -> 25 PRB at Itbs 11 -> 621 -> 621000 bytes/sec
116  // 3 users -> 8 PRB at Itbs 11 -> 201 -> 201000 bytes/sec
117  // 6 users -> 4 PRB at Itbs 11 -> 97 -> 97000 bytes/sec
118  // 9 users -> 3 PRB at Itbs 11 -> 73 bytes * 8/9 UE/TTI -> 64889 bytes/sec
119  // 12 users -> 3 PRB at Itbs 11 -> 73 bytes * 8/12 UE/TTI -> 48667 bytes/sec
120  // 15 users -> 3 PRB at Itbs 11 -> 73 bytes * 8/15 UE/TTI -> 38993 bytes/sec
121  AddTestCase (new LenaRrFfMacSchedulerTestCase (1,6000,1191000,621000,errorModel), TestCase::EXTENSIVE);
122  AddTestCase (new LenaRrFfMacSchedulerTestCase (3,6000,389000,201000,errorModel), TestCase::EXTENSIVE);
123  AddTestCase (new LenaRrFfMacSchedulerTestCase (6,6000,193000,97000,errorModel), TestCase::EXTENSIVE);
124  AddTestCase (new LenaRrFfMacSchedulerTestCase (9,6000,97000,64889,errorModel), TestCase::EXTENSIVE);
125  AddTestCase (new LenaRrFfMacSchedulerTestCase (12,6000,97000,48667,errorModel), TestCase::EXTENSIVE);
126  AddTestCase (new LenaRrFfMacSchedulerTestCase (15,6000,77600,38993,errorModel), TestCase::EXTENSIVE);
127 
128  // DOWNLINK - DISTANCE 20000 -> MCS 8 -> Itbs 8 (from table 7.1.7.2.1-1 of 36.213)
129  // 1 user -> 24 PRB at Itbs 8 -> 421 -> 421000 bytes/sec
130  // 3 users -> 8 PRB at Itbs 8 -> 137 -> 137000 bytes/sec
131  // 6 users -> 4 PRB at Itbs 8 -> 67 -> 67000 bytes/sec
132  // 9 user -> 2 PRB at Itbs 8 -> 32 -> 32000 bytes/sec
133  // 12 users -> 2 PRB at Itbs 8 -> 32 -> 32000 bytes/sec
134  // 15 users -> 2 PRB at Itbs 8 * 0.8 -> 25.6 -> 25600 bytes/sec
135  // UPLINK - DISTANCE 20000 -> MCS 2 -> Itbs 2 (from table 7.1.7.2.1-1 of 36.213)
136  // 1 user -> 25 PRB at Itbs 2 -> 137 -> 137000 bytes/sec
137  // 3 users -> 8 PRB at Itbs 2 -> 41 -> 41000 bytes/sec
138  // 6 users -> 4 PRB at Itbs 2 -> 22 -> 22000 bytes/sec
139  // after the patch enforcing min 3 PRBs per UE:
140  // 9 users -> 3 PRB at Itbs 2 -> 18 bytes * 8/9 UE/TTI -> 16000 bytes/sec
141  // 12 users -> 3 PRB at Itbs 2 -> 18 bytes * 8/12 UE/TTI -> 12000 bytes/sec
142  // 15 users -> 3 PRB at Itbs 2 -> 18 bytes * 8/15 UE/TTI -> 9600 bytes/sec
143  AddTestCase (new LenaRrFfMacSchedulerTestCase (1,20000,421000,137000,errorModel), TestCase::EXTENSIVE);
144  AddTestCase (new LenaRrFfMacSchedulerTestCase (3,20000,137000,41000,errorModel), TestCase::EXTENSIVE);
145  AddTestCase (new LenaRrFfMacSchedulerTestCase (6,20000,67000,22000,errorModel), TestCase::EXTENSIVE);
146  AddTestCase (new LenaRrFfMacSchedulerTestCase (9,20000,32000,16000,errorModel), TestCase::EXTENSIVE);
147  AddTestCase (new LenaRrFfMacSchedulerTestCase (12,20000,32000,12000,errorModel), TestCase::EXTENSIVE);
148  AddTestCase (new LenaRrFfMacSchedulerTestCase (15,20000,25600,9600,errorModel), TestCase::EXTENSIVE);
149 
150  // DOWNLINK - DISTANCE 100000 -> CQI == 0 -> out of range -> 0 bytes/sec
151  // UPLINK - DISTANCE 100000 -> CQI == 0 -> out of range -> 0 bytes/sec
152  AddTestCase (new LenaRrFfMacSchedulerTestCase (1,100000,0,0,errorModel), TestCase::QUICK);
153 }
154 
156 
157 std::string
159 {
160  std::ostringstream oss;
161  oss << nUser << " UEs, distance " << dist << " m";
162  return oss.str ();
163 }
164 
165 LenaRrFfMacSchedulerTestCase::LenaRrFfMacSchedulerTestCase (uint16_t nUser, double dist, double thrRefDl, double thrRefUl, bool errorModelEnabled)
166  : TestCase (BuildNameString (nUser, dist)),
167  m_nUser (nUser),
168  m_dist (dist),
169  m_thrRefDl (thrRefDl),
170  m_thrRefUl (thrRefUl),
171  m_errorModelEnabled (errorModelEnabled)
172 {
173 }
174 
176 {
177 }
178 
179 void
181 {
182  NS_LOG_FUNCTION (this << m_nUser << m_dist);
183  if (!m_errorModelEnabled)
184  {
185  Config::SetDefault ("ns3::LteSpectrumPhy::CtrlErrorModelEnabled", BooleanValue (false));
186  Config::SetDefault ("ns3::LteSpectrumPhy::DataErrorModelEnabled", BooleanValue (false));
187  }
188  Config::SetDefault ("ns3::LteHelper::UseIdealRrc", BooleanValue (false));
189 
190  // This is needed as the RR scheduler does not allocate resources properly for retransmission
191  Config::SetDefault ("ns3::LteRlcAm::TxOpportunityForRetxAlwaysBigEnough", BooleanValue (true));
192 
193  //Disable Uplink Power Control
194  Config::SetDefault ("ns3::LteUePhy::EnableUplinkPowerControl", BooleanValue (false));
195 
200  Ptr<LteHelper> lteHelper = CreateObject<LteHelper> ();
201 
202  lteHelper->SetAttribute ("PathlossModel", StringValue ("ns3::FriisSpectrumPropagationLossModel"));
203 
204  // Create Nodes: eNodeB and UE
205  NodeContainer enbNodes;
206  NodeContainer ueNodes;
207  enbNodes.Create (1);
208  ueNodes.Create (m_nUser);
209 
210  // Install Mobility Model
212  mobility.SetMobilityModel ("ns3::ConstantPositionMobilityModel");
213  mobility.Install (enbNodes);
214  mobility.SetMobilityModel ("ns3::ConstantPositionMobilityModel");
215  mobility.Install (ueNodes);
216 
217  // Create Devices and install them in the Nodes (eNB and UE)
218  NetDeviceContainer enbDevs;
219  NetDeviceContainer ueDevs;
220  lteHelper->SetSchedulerType ("ns3::RrFfMacScheduler");
221  enbDevs = lteHelper->InstallEnbDevice (enbNodes);
222  ueDevs = lteHelper->InstallUeDevice (ueNodes);
223 
224  // Attach a UE to a eNB
225  lteHelper->Attach (ueDevs, enbDevs.Get (0));
226 
227  // Activate an EPS bearer
228  enum EpsBearer::Qci q = EpsBearer::GBR_CONV_VOICE;
229  EpsBearer bearer (q);
230  lteHelper->ActivateDataRadioBearer (ueDevs, bearer);
231 
232 
233  Ptr<LteEnbNetDevice> lteEnbDev = enbDevs.Get (0)->GetObject<LteEnbNetDevice> ();
234  Ptr<LteEnbPhy> enbPhy = lteEnbDev->GetPhy ();
235  enbPhy->SetAttribute ("TxPower", DoubleValue (30.0));
236  enbPhy->SetAttribute ("NoiseFigure", DoubleValue (5.0));
237 
238  // Set UEs' position and power
239  for (int i = 0; i < m_nUser; i++)
240  {
242  mm->SetPosition (Vector (m_dist, 0.0, 0.0));
243  Ptr<LteUeNetDevice> lteUeDev = ueDevs.Get (i)->GetObject<LteUeNetDevice> ();
244  Ptr<LteUePhy> uePhy = lteUeDev->GetPhy ();
245  uePhy->SetAttribute ("TxPower", DoubleValue (23.0));
246  uePhy->SetAttribute ("NoiseFigure", DoubleValue (9.0));
247  }
248 
249 
250  double statsStartTime = 0.300; // need to allow for RRC connection establishment + SRS
251  double statsDuration = 0.4;
252  double tolerance = 0.1;
253  Simulator::Stop (Seconds (statsStartTime + statsDuration - 0.0001));
254 
255  lteHelper->EnableRlcTraces ();
256  Ptr<RadioBearerStatsCalculator> rlcStats = lteHelper->GetRlcStats ();
257  rlcStats->SetAttribute ("StartTime", TimeValue (Seconds (statsStartTime)));
258  rlcStats->SetAttribute ("EpochDuration", TimeValue (Seconds (statsDuration)));
259 
260  Simulator::Run ();
261 
265  NS_LOG_INFO ("DL - Test with " << m_nUser << " user(s) at distance " << m_dist);
266  std::vector <uint64_t> dlDataRxed;
268  {
269  m_thrRefDl *= 0.95; // for couting the Vienna AMC behavior: BLER between 0% and 10%
270  }
271  for (int i = 0; i < m_nUser; i++)
272  {
273  // get the imsi
274  uint64_t imsi = ueDevs.Get (i)->GetObject<LteUeNetDevice> ()->GetImsi ();
275  uint8_t lcId = 3;
276  dlDataRxed.push_back (rlcStats->GetDlRxData (imsi, lcId));
277  NS_LOG_INFO ("\tUser " << i << " imsi " << imsi << " lcid " << (uint16_t) lcId << " bytes rxed " << (double)dlDataRxed.at (i) << " thr " << (double)dlDataRxed.at (i) / statsDuration << " ref " << m_thrRefDl);
278  NS_TEST_ASSERT_MSG_EQ_TOL ((double)dlDataRxed.at (i) / statsDuration, m_thrRefDl, m_thrRefDl * tolerance, " Unfair Throughput!");
279  }
280 
281  NS_LOG_INFO ("UL - Test with " << m_nUser << " user(s) at distance " << m_dist);
282  std::vector <uint64_t> ulDataRxed;
284  {
285  m_thrRefUl *= 0.95; // for couting the Vienna AMC behavior: BLER between 0% and 10%
286  }
287  for (int i = 0; i < m_nUser; i++)
288  {
289  // get the imsi
290  uint64_t imsi = ueDevs.Get (i)->GetObject<LteUeNetDevice> ()->GetImsi ();
291  // get the lcId
292  uint8_t lcId = 3;
293  ulDataRxed.push_back (rlcStats->GetUlRxData (imsi, lcId));
294  NS_LOG_INFO ("\tUser " << i << " imsi " << imsi << " lcid " << (uint16_t) lcId << " bytes rxed " << (double)ulDataRxed.at (i) << " thr " << (double)ulDataRxed.at (i) / statsDuration << " ref " << m_thrRefUl << " txed " << rlcStats->GetUlTxData (imsi, lcId) / statsDuration);
295  NS_TEST_ASSERT_MSG_EQ_TOL ((double)ulDataRxed.at (i) / statsDuration, m_thrRefUl, m_thrRefUl * tolerance, " Unfair Throughput!");
296  }
297 
298  Simulator::Destroy ();
299 }
Ptr< NetDevice > Get(uint32_t i) const
Get the Ptr<NetDevice> stored in this container at a given index.
#define NS_LOG_FUNCTION(parameters)
If log level LOG_FUNCTION is enabled, this macro will output all input parameters separated by "...
uint16_t m_nUser
number of UE nodes
AttributeValue implementation for Boolean.
Definition: boolean.h:36
NetDeviceContainer InstallEnbDevice(NodeContainer c)
Create a set of eNodeB devices.
Definition: lte-helper.cc:474
Hold variables of type string.
Definition: string.h:41
A suite of tests to run.
Definition: test.h:1342
Mobility model for which the current position does not change once it has been set and until it is se...
void Attach(NetDeviceContainer ueDevices)
Enables automatic attachment of a set of UE devices to a suitable cell using Idle mode initial cell s...
Definition: lte-helper.cc:957
#define NS_LOG_COMPONENT_DEFINE(name)
Define a Log component with a specific name.
Definition: log.h:202
void EnableRlcTraces(void)
Enable trace sinks for RLC layer.
Definition: lte-helper.cc:1431
#define NS_LOG_INFO(msg)
Use NS_LOG to output a message of level LOG_INFO.
Definition: log.h:278
encapsulates test code
Definition: test.h:1155
void ActivateDataRadioBearer(NetDeviceContainer ueDevices, EpsBearer bearer)
Activate a Data Radio Bearer on a given UE devices (for LTE-only simulation).
Definition: lte-helper.cc:1310
void SetSchedulerType(std::string type)
Set the type of scheduler to be used by eNodeB devices.
Definition: lte-helper.cc:279
mobility
Definition: third.py:101
This class contains the specification of EPS Bearers.
Definition: eps-bearer.h:71
double m_dist
the distance between nodes
double m_thrRefDl
the DL throughput reference
AttributeValue implementation for Time.
Definition: nstime.h:1076
void AddTestCase(TestCase *testCase, TestDuration duration=QUICK)
Add an individual child TestCase to this test suite.
Definition: test.cc:299
uint64_t GetDlRxData(uint64_t imsi, uint8_t lcid)
Gets the number of received downlink data bytes.
holds a vector of ns3::NetDevice pointers
Ptr< LteEnbPhy > GetPhy(void) const
#define NS_TEST_ASSERT_MSG_EQ_TOL(actual, limit, tol, msg)
Test that actual and expected (limit) values are equal to plus or minus some tolerance and report and...
Definition: test.h:380
double m_thrRefUl
the UL throughput reference
Ptr< T > GetObject(void) const
Get a pointer to the requested aggregated Object.
Definition: object.h:459
Every class exported by the ns3 library is enclosed in the ns3 namespace.
keep track of a set of node pointers.
static std::string BuildNameString(uint16_t nUser, double dist)
Builds the test name string based on provided parameter values.
Ptr< LteUePhy > GetPhy(void) const
Get the Phy.
bool m_errorModelEnabled
indicates whether the error model is enabled
void SetPosition(const Vector &position)
Test suite for RrFfMacScheduler test.
Ptr< RadioBearerStatsCalculator > GetRlcStats(void)
Definition: lte-helper.cc:1568
NetDeviceContainer InstallUeDevice(NodeContainer c)
Create a set of UE devices.
Definition: lte-helper.cc:489
Helper class used to assign positions and mobility models to nodes.
uint64_t GetUlTxData(uint64_t imsi, uint8_t lcid)
Gets the number of transmitted uplink data bytes.
uint64_t GetUlRxData(uint64_t imsi, uint8_t lcid)
Gets the number of received uplink data bytes.
This system test program creates different test cases with a single eNB and This system test program ...
Time Seconds(double value)
Construct a Time in the indicated unit.
Definition: nstime.h:1014
LenaRrFfMacSchedulerTestCase(uint16_t nUser, double dist, double thrRefDl, double thrRefUl, bool errorModelEnabled)
Constructor.
void SetDefault(std::string name, const AttributeValue &value)
Definition: config.cc:782
Ptr< Node > Get(uint32_t i) const
Get the Ptr<Node> stored in this container at a given index.
void Create(uint32_t n)
Create n nodes and append pointers to them to the end of this NodeContainer.
static LenaTestRrFfMacSchedulerSuite lenaTestRrFfMacSchedulerSuite
virtual void DoRun(void)
Implementation to actually run this TestCase.
This class can be used to hold variables of floating point type such as &#39;double&#39; or &#39;float&#39;...
Definition: double.h:41
void SetAttribute(std::string name, const AttributeValue &value)
Set a single attribute, raising fatal errors if unsuccessful.
Definition: object-base.cc:185
The eNodeB device implementation.
Qci
QoS Class Indicator.
Definition: eps-bearer.h:77
The LteUeNetDevice class implements the UE net device.