LTE Principles Virtual Lab

Explore Long Term Evolution (4G) architecture, frame structures, OFDMA/SC-FDMA modulation, and radio resource management through interactive simulations.

E-UTRAN Architecture
OFDMA Downlink
SC-FDMA Uplink
MIMO Technology

Laboratory Objectives

Architecture Understanding

Understand the EPS architecture including E-UTRAN and EPC components (eNodeB, MME, SGW, PGW)

Frame Structure

Analyze LTE frame structure, subframes, slots, symbols, and resource block allocation

Modulation Techniques

Compare OFDMA (downlink) vs SC-FDMA (uplink) modulation schemes and their characteristics

Resource Management

Understand Resource Blocks (RB), Resource Elements (RE), and bandwidth allocation strategies

Physical Channels

Identify PDSCH, PUSCH, PDCCH, PBCH, and synchronization signals (PSS/SSS)

Performance Analysis

Analyze throughput, spectral efficiency, and latency characteristics of LTE systems

Theoretical Background

1. LTE Architecture (EPS)

The Evolved Packet System (EPS) consists of two main components: E-UTRAN (Evolved UMTS Terrestrial Radio Access Network) and EPC (Evolved Packet Core).

eNodeB (evolved NodeB): Base station handling radio resource management, scheduling, and compression. No RNC exists in LTE.
MME (Mobility Management Entity): Signaling entity for bearer management, authentication, and mobility.
SGW (Serving Gateway): Local mobility anchor for inter-eNB handover, packet routing.
PGW (PDN Gateway): Connects to external networks, IP allocation, policy enforcement.

EPS Architecture Diagram

UE eNodeB MME SGW PGW Internet Uu S1-MME S1-U S5/S8 SGi X2 eNodeB

2. Frame Structure & Physical Resources

Time Domain

  • • Frame: 10 ms
  • • Subframe: 1 ms (10 per frame)
  • • Slot: 0.5 ms (2 per subframe)
  • • Symbol: 66.7 μs (7 per slot, normal CP)

Frequency Domain

  • • Subcarrier spacing: 15 kHz
  • • Resource Block: 12 subcarriers (180 kHz)
  • • Resource Element: 1 subcarrier × 1 symbol
  • • Bandwidths: 1.4, 3, 5, 10, 15, 20 MHz

Resource Block Config

  • • 20 MHz: 100 RBs (1200 subcarriers)
  • • 10 MHz: 50 RBs (600 subcarriers)
  • • 5 MHz: 25 RBs (300 subcarriers)
  • • RE per RB: 84 (7×12) normal CP

LTE Frame Structure (FDD)

Frame (10ms)
System Frame Number (SFN)
Subframes
0
1
2
3
4
5
6
7
8
9
Slots (0.5ms)
0
1
2
3
...
19
Normal
PSS/SSS

3. Modulation Techniques

OFDMA (Downlink)

Orthogonal Frequency Division Multiple Access uses different subcarriers for different users simultaneously. High PAPR but efficient for broadcast.

Access Method Multi-carrier
Subcarrier Mapping Distributed
PAPR High
Suitable for Broadcast (DL)

SC-FDMA (Uplink)

Single Carrier FDMA uses DFT precoding before OFDM modulation. Lower PAPR improves power amplifier efficiency in mobile devices.

Access Method Single-carrier
DFT Precoding Yes (M-point)
PAPR Low
Suitable for Mobile (UL)

4. Physical Channels & Signals

Downlink Channels

PDSCH Physical Downlink Shared Channel - User data
PDCCH Physical Downlink Control Channel - Scheduling info
PBCH Physical Broadcast Channel - MIB information
PCFICH Physical Control Format Indicator Channel

Synchronization & Reference

PSS Primary Synchronization Signal - Slot timing, Cell ID (0-2)
SSS Secondary Synchronization Signal - Frame timing, Cell ID
CRS Cell-Specific Reference Signals - Channel estimation
PRACH Physical Random Access Channel - Initial access

Interactive Simulations

EPS Architecture Explorer

UE eNodeB E-UTRAN MME Control Plane SGW User Plane PGW External GW Internet Uu S1-MME S1-U S5/S8 SGi X2

Component Details

Click on a component in the diagram to view details

Interface Legend
Solid: User/Control Plane
Dashed: X2 Interface

Laboratory Procedure

1

EPS Architecture Analysis

Steps:

  1. Navigate to the Architecture simulation tab
  2. Click on each network component (UE, eNodeB, MME, SGW, PGW) to view detailed functions
  3. Click "Control Traffic" to visualize signaling path (UE → eNodeB → MME)
  4. Click "User Traffic" to visualize data path (UE → eNodeB → SGW → PGW → Internet)
  5. Click "Handover" to observe X2 interface usage between eNodeBs
  6. Record the interface names (Uu, S1-MME, S1-U, S5/S8, SGi, X2)

Expected Observations

  • • Control plane traffic flows through MME
  • • User plane traffic bypasses MME after setup
  • • X2 interface enables inter-eNB handover without core network involvement
  • • SGW serves as local mobility anchor
2

Frame Structure Analysis

Steps:

  1. Select the Frame Structure simulation tab
  2. Set bandwidth to 5 MHz (25 RBs) initially
  3. Observe the resource grid structure (12 subcarriers × 7 symbols per RB)
  4. Change cyclic prefix from Normal to Extended and observe symbol count change
  5. Navigate through different subframes (0-9) using the slider
  6. Identify special subframes containing PSS/SSS (subframes 0 and 5)
  7. Increase bandwidth to 20 MHz and observe increased RB count

Expected Observations

  • • Normal CP: 7 OFDM symbols per slot
  • • Extended CP: 6 OFDM symbols per slot
  • • PSS located in last OFDM symbol of slots 0 and 10
  • • SSS located in second-to-last symbol of slots 0 and 10
  • • 20 MHz = 100 RBs = 1200 subcarriers
3

OFDMA vs SC-FDMA Comparison

Steps:

  1. Select the Modulation simulation tab
  2. Observe the transmitter block diagrams for both schemes
  3. Note the DFT precoding block present only in SC-FDMA
  4. Adjust the number of subcarriers slider (4 to 64)
  5. Observe PAPR values for both schemes
  6. Compare spectral shapes in the spectrum plots
  7. Record PAPR difference between OFDMA and SC-FDMA

Expected Observations

  • • OFDMA has higher PAPR (typically 10-13 dB)
  • • SC-FDMA has lower PAPR (typically 6-8 dB)
  • • SC-FDMA spectrum has steeper roll-off
  • • Both use OFDM for actual transmission
  • • DFT precoding spreads data across subcarriers
4

Resource Allocation Strategies

Steps:

  1. Select the Resource Allocation simulation tab
  2. Set bandwidth to 10 MHz (50 RBs)
  3. Set number of users to 4
  4. Observe localized allocation (contiguous RBs per user)
  5. Switch to distributed allocation strategy
  6. Observe interleaved RB assignment pattern
  7. Vary number of users and observe RB distribution
  8. Record utilization percentage for different configurations

Expected Observations

  • • Localized: Better for frequency-selective fading channels
  • • Distributed: Better frequency diversity
  • • Each user gets approximately equal RB allocation
  • • Some RBs reserved for control channels
  • • 20 MHz provides 100 RBs for allocation
5

Throughput Analysis

Steps:

  1. Select the Throughput Calculator tab
  2. Set bandwidth to 10 MHz, MIMO 2x2, MCS 16
  3. Record the calculated throughput
  4. Increase bandwidth to 20 MHz and observe change
  5. Change MIMO to 4x4 and observe throughput scaling
  6. Vary MCS from 0 (QPSK) to 28 (64QAM high rate)
  7. Plot throughput vs MCS index
  8. Calculate spectral efficiency for each configuration

Expected Observations

  • • 20 MHz provides ~2x throughput of 10 MHz
  • • 4x4 MIMO provides ~2x throughput of 2x2
  • • Higher MCS increases throughput but requires better SNR
  • • Typical LTE peak: ~150 Mbps DL (20 MHz, 2x2)
  • • Overhead accounts for ~25% of resources

Report Writing Guidelines

Required Report Structure

1

Title Page

Experiment title, student name, ID, date, course code

2

Objectives

List the specific learning objectives for this experiment

3

Theory

Brief explanation of LTE architecture, frame structure, and modulation

4

Procedure

Step-by-step description of simulations performed

5

Results & Observations

Screenshots, tables, graphs with proper labels and captions

6

Analysis & Discussion

Interpretation of results, comparison with theoretical values

7

Conclusion

Summary of key findings and learning outcomes

8

References

3GPP specifications, textbooks, technical papers

Data Tables Template

Table 1: Architecture Interfaces

InterfaceBetweenProtocol
UuUE-eNodeBPHY/MAC/RLC/PDCP/RRC
S1-MMEeNodeB-MMES1-AP/SCTP
S1-UeNodeB-SGWGTP-U/UDP

Table 2: Throughput Measurements

BandwidthMIMOMCSThroughput
10 MHz2x216___ Mbps
20 MHz2x216___ Mbps
20 MHz4x428___ Mbps

Grading Rubric

Completeness of simulations 20%
Quality of observations 25%
Data analysis & graphs 25%
Discussion & conclusions 20%
Report presentation 10%

Submission Requirements

  • • Submit PDF report via learning management system
  • • Include screenshots of all simulation results
  • • Maximum 20 pages (excluding appendices)
  • • Use IEEE citation format for references
  • • Due date: Check course schedule