Basics on LTE

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Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
Basics on LTE
HCIA-5G UFRN
Page 1 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
Contents
• LTE Targets
• LTE Architecture
• LTE Protocol Stack
• LTE Resource Allocation
• Final Remarks
Page 2 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Targets
• Fulfill the 4G requirements
– Optimized throughput to support 100Mbps to 1Gbps;
– Lower packet delivery delay (latency).
• Main enablers
– OFDMA Multiple Access;
– All-IP architecture;
– Radio Resource Management features on Node B (renamed to eNB);
– New flat architecture based on EPC (Evolved Packet Core Network);
– Interworking with other RANs, 3GPP e non-3GPP (2G/3G e Wi-Fi).
Higher-data-rate, Lower-latency, Packet-optimized
system
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LTE Architecture
• Flat architecture
– Fewer elements and less 
bureaucratic;
– Changes start on Release 
7 wit HSPA+.
Release 7: direct path to the GGSN for user plane and the fusion of RNC and NodeB.
Source: 
https://onlinelibrary.wiley.com/doi/book/10.1002/9
781119992943
GGSN: Gateway GPRS Support Node 
(or P-GW: Packet Data Network Gateway)
SGSN: Serving GPRS Support Node
(or S-GW: Serving Gateway)
RNC: Radio Network Controller
SAE: System Architecture Evolution.
Page 4 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Architecture
Source: https://onlinelibrary.wiley.com/doi/book/10.1002/9781119992943
GGSN: Gateway GPRS Support Node 
(or P-GW: Packet Data Network Gateway)
SGSN: Serving GPRS Support Node
(or S-GW: Serving Gateway)
RNC: Radio Network Controller
SAE: System Architecture Evolution.
Page 5 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Architecture
• Main changes and new elements
– New Uu interface; 
– New X2 interface (between eNBs);
– EPC (Evolved Packet Core) without the
traditional CS core (all-IP net);
– S1-U and S1-MME interfaces (between RAN 
and EPC);
– SAE GW: P-GW + S-GW;
– MME: Mobility Management Entity;
– PCRF: Policy and Charging Rules Function.
Source: 
https://onlinelibrary.wiley.com/doi/book/10.1002/9781119992943
Evolved Packet System (EPS)
GGSN: Gateway GPRS Support Node 
(or P-GW: Packet Data Network Gateway)
SGSN: Serving GPRS Support Node
(or S-GW: Serving Gateway)
RNC: Radio Network Controller
SAE: System Architecture Evolution.
Page 6 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Protocol Architecture
• RRC (L3)
• Control Plane signalling by which the RAN controls the UE behavior 
(mobility and measurements control and reporting);
• RRC states;
• PDCP (L2): header compression, security (integrity protection and 
ciphering); Radio Bearers (user plane);
• RLC (L2): 
– Segmentation and reassembly of packets and retransmistion handling;
– Defines the kind of information through logical channels (traffic and
control channels);
• MAC (L2): 
– Data transmission scheduling through transport channels;
– Control HARQ retransmission and link adaptation;
– Control random access and DRX (discontinuous reception);
– Defines who, when and how the information will be transmitted.
• PHY (L1): 
– Raw data transmission (OFDMA signal) over a physical link (air).
– Subframe Building.
Source: https://onlinelibrary.wiley.com/doi/book/10.1002/9781119992943
RRC: Radio Resource Control
PDCP: Packet Data Convergence Protocol.
RLC: Radio Link Control.
MAC: Medium Access Control.
Physical Channels
Page 7 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Protocol Architecture
Source: http://pt.slideshare.net/Netmanias/netmanias20130215lte-protocol-stack-ue-sidee
Page 8 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
Source: http://pt.slideshare.net/Netmanias/netmanias20130215lte-protocol-stack-ue-sidee
Source: https://www.freescale.com/files/wireless_comm/doc/white_paper/LTEPTCLOVWWP.pdf
Page 9 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
Source: http://lteuniversity.com/get_trained/expert_opinion1/b/lauroortigoza/archive/2012/08/07/frame-structures-in-lte-tdd-and-lte-fdd.aspx
• OFDMA transmission based on 
frames;
• Frames:
– Duration: 10 ms;
– 10 subframes of 1 ms each;
• Subframes
– Time Transmission Interval (TTI): 
transmission granularity;
– 2 Resource Elements (RB) of 0,5 ms
each.
Page 10 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
Fonte: http://lteuniversity.com/get_trained/expert_opinion1/b/lauroortigoza/archive/2012/08/07/frame-structures-in-lte-tdd-and-lte-fdd.aspx
180 kHz
Time
F
re
q
u
e
n
c
y
Page 11 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
Source: http://lteuniversity.com/get_trained/expert_opinion1/b/lauroortigoza/archive/2012/08/07/frame-structures-in-lte-tdd-and-lte-fdd.aspx
Largura de banda 1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz
Duração do Sub-frame 1 ms
Espaço entre sub-
portadoras 15 kHz
Tamanho da FFT 128 256 512 1024 1536 2048
Número de 
subportadoras
ocupadas
72 150 300 600 900 1200
Número de Resource 
Block (RB) 6 18 25 50 75
100
Page 12 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
F
re
q
u
ê
n
c
ia
Source: http://dhagle.in/LTE
Page 13 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
LTE Resource Allocation
Fonte: http://www.sharetechnote.com/html/Handbook_LTE_RAType.html
Page 14 Copyright © 2021 Huawei Technologies Co., Ltd. All rights reserved. 
Final Remarks
• LTE is an evolution of 3GPP systems towards 4G;
• LTE is based on
• A flat architecture (latency);
• Flexible OFDMA multiple access with several bandwidths options;
• Flexible resource allocation by means of time/frequency allocation trhough Resources
Blocks (RBs);
• A 1 ms PHY layer acess (subframe), providing:
• End-to-end latency of 50 ms (4G LTE-advanced);
• 1 Gbps throughtput (4G LTE-advanced).
• LTE is still evolving even in 5G era.
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