Presentation of Webinar on LTE by NetSim, with focus on research. For further details: http://www.tetcos.com

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NetSim v9Network Simulation/Emulation Platform
TM
Webinar: Architecture, Working
and Simulation of LTE Networks
28th July 2016
15:30 IST
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Twitter.com/tetcos linkedin.com/company/tetcos youtube.com/tetcos
NetSim Webinar
Architecture, Working and
Simulation of LTE Networks

3. NetSim
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AGENDA
LTE Introduction
Devices and Interfaces in LTE
LTE Protocol Stack
OFDM PHY in LTE & Data rate calculation
Working of MME and eNB
LTE Association
LTE Hand over
What’s next ? LTE Advanced and R & D Areas in LTE
Q & A

4. NetSim
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LTE INTRODUCTION
• LTE stands for Long Term Evolution
• It is a standard for high speed wireless communication
• Standardized by 3GPP (36 Series)
• First proposed in 2004 by NTT DoCoMo
• Marketed as 4G LTE (4.5G is LTE – Advanced)
• All IP flat architecture
• NetSim simulations are based on LTE Rel 12
2G-GSM
3G-UMTS
4G-LTE

5. NetSim
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CIRCUIT SWITCHED VS. PACKET SWITCHED
GSM
• GSM - Circuit
Switching, very low
rate for data
GPRS
• IP based packet
Switching
UMTS
• IP based Data
services, Circuit
switched core for
incoming data
services
EPS
• Purely IP based for
both real time and
datacom services

6. NetSim
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DEVICE AND INTERFACES
Air Interface
10.1.1.310.1.1.2
Air Interface
S1 - MME
NetSim Example – LTE Network Design in LTE
10.1.1.1
Devices
MME - Mobility Management Entity
ENB - Evolved Node B
UE - User Equipment
Interfaces
Air Interface - Between ENB and UE(Interface_LTE)
S1-MME - Between ENB and MME(Interface_LTE_S1)
Addressing - IPv4

7. NetSim
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LTE STACK

8. NetSim
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LTE PHY LAYER
Downlink: OFDMA
OFDMA solution leads to high Peak-to-Average Power Ratio (PAPR) requiring
expensive power amplifiers.
This is no problem in the eNB, but would lead to very expensive handsets.
Hence a different solution was selected for the UL.
To enable possible deployment around the world, LTE is developed for a
number of frequency bands
• Ranging from 700 MHz up to 2.7GHz.
• Available bandwidths are also flexible starting with 1.4 MHz up to
20 MHz.
Uplink: SC-FDMA

9. NetSim
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SPEED OF LTE AIR INTERFACE
Resource Element (RE):
• 1 subcarrier x 1 symbol period
• Theoretical minimum capacity allocation unit.
• Equivalent to 1 modulation symbol on a subcarrier.
• 2 bits for QPSK, 4 bits for 16 QAM and 6 bits for 64 QAM
Resource Block (RB):
• Capacity allocation is based on Resource Blocks.
• 12 subcarriers each of 15 kHz = 180 kHz in frequency
domain and one slot (0.5 ms) in time domain
RE

10. NetSim
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PHY RATE CALCULATION THEORETICAL
Example: PHY rate calculation for 20MHz band, using 64-QAM and 4*2
MIMO
• For 20 MHz there are 100 Resource blocks (20 MHz / 200 KHz)
• Each resource block has 12*7 = 84 symbols
• 100 resource blocks have 8400 symbols
• 1 sub frame = 1 ms = 2 time slots
• 16800 symbols per subframe (or per ms)
• 64-QAM can transmit 6 bits per symbol
• 1 subframe using 64-QAM modulation can transmit 100800 bits/ms
• 100.8*106 bits per second or 100.8 Mbps
• This is for a 1*1 and for 4*2 MIMO 100.8*4 = 403.2 Mbps
• Of this typically 25 % is overhead => ~ 300 Mbps capacity

11. NetSim
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PHY RATE CALCULATION IN NETSIM
Calculation for PHY Data rate in NetSim is based on the Transport
Block Size (TBS) which is specified in the standard.
1. Any signal received at the receiver has a SNR (signal to noise
ratio)
2. Based on the SNR a Channel Quality Indicator (CQI) value is
calculated
3. The SNR - CQI Table is available in LTE.h in NetSim and is per
the LTE standard
4. Based on the SNR and the CQI an Modulation & Coding
Scheme (MCS) value is calculated
5. The SNR CQI MCS table is available in LTE.h in NetSim and is
per the LTE standard
6. Based on the MCS the TBS Index is calculated, again from a
table available in LTE.h which is per the LTE Standard
7. Based on the TBS Index the TBS Table is looked up and the
transport block size is retrieved
CQI = 15
64 QAM
CQI = 8
16 QAM
CQI = 1
QPSK
Packet
Scheduler
UE
UE
UE

12. NetSim
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PHY RATE CALCULATIONS IN NETSIM
NetSim Example
1. PHY Data Rate & Application throughput at different distances
2. SNR, CQI, MCS Index and TBS Index Value Printed to File
Code is modified in the LTE_Phy.c file, so as to write SNR, CQI, MCS Index and TBS Index Value to a LTE_PARAMETERS.txt .

13. NetSim
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WHAT DOES AN MME DO?
• Network Access control to UE
• IP connectivity to UE
• Mobility Management including roaming
• Contains the Home Location Register
• UE Reachability
• Route the packets to different eNB depending on
where end UE is
• Connects via S1 Interface with the ENB.
• NetSim Example
• Printing the HLR to a file
• Code is modified in the NAS.c file, so as to
write the HLR table to a HLR.txt file before
and after the event of an Handover occurs.

14. NetSim
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WHAT DOES AN ENB DO ?
1. The LTE eNB manages radio resources
2. Key function - Runs the packet Scheduler
• Round Robin
• Proportional Fair Scheduling
• Max CQI
3. Hand over management
4. NetSim Example - MAC Scheduling algorithms
NetSim White Paper

15. NetSim
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ANALYSIS OF MAC SCHEDULING
Example 1 Example 2

16. NetSim
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PLOTS FOR ROUND ROBIN OF EXAMPLE 1 & 2
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
DIFFRENT DISTANCE
ROUND ROBIN
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
EQUIVALENT DISTANCE
ROUND ROBIN

17. NetSim
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PLOTS FOR PROPORTIONAL FAIR OF EXAMPLE 1 & 2
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
DIFFRENT DISTANCE
PROPORTIONAL FAIR
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
EQUIVALENT DISTANCE
PROPORTIONAL FAIR

18. NetSim
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PLOTS FOR MAX THROUGHPUT OF EXAMPLE 1 & 2
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
DIFFRENT DISTANCE
MAX-THROUGHPUT
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
EQUIVALENT DISTANCE
MAX-THROUGHPUT

19. NetSim
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CUMULATIVE PLOTS OF EXAMPLE 1 AND 2
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
VARIED DISTANCE
ROUND ROBIN
PROPORTIONAL FAIR
MAX-THROUGHPUT
0
2
4
6
8
10
12
1 2 3 4 5
THROUGHPUT(Mbps)
APPLICATION ID
EQUIVALENT DISTANCE
ROUND ROBIN
PROPORTIONAL FAIR
MAX-THROUGHPUT

20. NetSim
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LTE ASSOCIATION
LTEPacket_RRC_CONNECTION_REQUEST
LTEPacket_RRC_CONNECTION_SETUP_COMPLETE
LTEPacket_RRC_CONNECTION_SETUP
NetSim Example – LTE Association
User Equipment (UE)
eNB

21. NetSim
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HAND OVER IN LTE
NetSim Example – LTE Hand Over
Source eNB Target eNB
MME
• Hand over decision is made based on SNR
• Decision is made by eNB and not MME
• Frequency & time allocation is done by MAC scheduler
User Equipment
After this association occurs
with Target eNB

22. NetSim
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WHAT’S NEXT IN LTE IN NETSIM AND SOME R & D AREAS
• Carrier aggregation
• 8*8 MIMO
• Relays
LTE Advanced
D2D Communication
MAC Scheduling
Mobility and hand over modelling
Header compression
Spectrum and bandwidth management
Spectrum sharing
What’s next in LTE ? R & D Areas

23. NetSim
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1. Since there are a large number of participants we request you to write your questions via chat
2. Depending on the available time, we will try to answer all questions. In case your query is not answered, we will
answer your question via email.
Q & A Session

24. NetSim
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