1. LTE – Long Term Evolution
Introduction

2. Outline Evolution and Adoption Features Architecture Radio Interface
Overview of Protocols and Channels
LTE-Advanced

3. Evolution TDMA EDGE GSM GPRS WCDMA PDC cdmaOne 2G evolved 2G 3G
CDMA x
GPRS
HSPA
WCDMA
PDC
LTE
LTE-A
CDMA x EV/DO
cdmaOne 2G
evolved 2G
64–144 kbps 3G
384 kbps - 2 Mbps
evolved 3G 4G
kbps
384 kbps Mbps
>1 Gbps
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4. LTE Adoption (as of May 2012)
Red – countries with LTE service
Dark Blue – planned or ongoing deployment
Light Blue – LTE system trials (pre-commitment)

5. Features All IP Network (VoIP for voice) Spectrum Flexibility
Can also use other 3GPP technologies for voice
Spectrum Flexibility
(1.25MHz – 20MHz)
TDD/FDD (full-duplex and half-duplex)
Multi-antenna transmissions (4 MIMO on downlink, 2 MIMO on uplink)
300 Mbps peak downlink in 20MHz x 4 MIMO x 64 QAM
75 Mbps peak uplink

6. Features (cont) 100 km macro cells (5 km with optimal performance)
Up to 200 active users in a cell
OFDM downlink and Single Carrier FDMA (SC-FDMA) uplink
HARQ (Hybrid ARQ)
Co-existence with existing technologies (calls can be started in LTE and transferred to GSM/GPRS, WCDMA)

7. Architecture UE – User Equipment eNodeB – evolved NodeB (BS)
S-GW – Serving Gateway
P-GW – PDN Gateway
MME – Mobility Management Entity
HSS – Home Subscriber Server
PCRF – Policy Rules and Charging Control Function

8. Elements
HSS – Home Subscriber Server – stores subscriber information, roaming capabilities, QoS profiles, current registration; may integrate AUC functionality
P-GW – PDN Gateway – allocates UE IP address, QoS enforcement, filters downlink packets in different QoS bearers
S-GW – Serving Gateway local mobility anchor as UE switches between eNodeBs, buffers downlink data until paging completes, charging for visiting users
MME – Mobile Management Entity controls flow between UE and CN (corresponding node) – handles idle mobility
PCRF – Policy Control and Charging Rules Function – charging, policy control, QoS authorization

9. Standardized QoS Class Identifiers (QCI)
GBR – Guaranteed Bit-Rate

10. Radio Interface Multiple Access Scheme Adaptive Modulation and Coding
Downlink uses QPSK, 16QAM and 64QAM
Uplink uses QPSK and 16QAM
Multiple Access Scheme
Downlink uses OFDMA
Uplink uses Single Carrier FDMA (SC-FDMA)
BLER – Block Error Rate

11. Generic Frame Structure
Allocation of physical resource blocks (PRBs) is handled by a scheduling function at the 3GPP base station (eNodeB)
Frame 0 and frame 5 (always downlink)

12. Resource Blocks
2D – Time x Frequency

13. Common Physical RB (PRB) Formats
Channel Bandwidth (MHz)
NRBDL/NRBUL
Typical IDFT size
Number of Non-Zero Sub-carriers (REs)
1.25 6
128 72 5 25
512
300 10 50
1024
600 15 75
1024 or 2048
900 20
100
2048
1200
PRBs are mapped onto contiguous OFDMA/SC-FDMA symbols in the time-domain (6 or 7)
Each PRB is chosen to be equivalent to 12 (15 kHz spacing) sub-carriers of an OFDMA symbol in the frequency-domain
Because of a common PRB size over different channel bandwidths, the system scales naturally over different bandwidths
UEs determines cell bandwidth during initial acquisition and can be any of above

14. Example: 300 REs, 25 RBs (5 MHz channel)
PRB13
PRB24
“Normal” Cyclic Prefix Mode
(7 symbols)
PRB23
PRB22
PRB21
PRB20
PRB19
PRB18
PRB17
PRB16
“Extended” Cyclic Prefix Mode
(6 symbols)
PRB15
PRB14
PRB13
PRB12
NRBDL/NRBUL
PRB12
PRB11
PRB10
PRB9
PRB8
PRB7
PRB6
PRB5
PRB4
PRB3
NSCRB
PRB2
PRB1
PRB0
PRB11
l=0
l=6
NULsymb /NULsymb

15. Sub-frame and Frame One frame = 10ms Tslot=500ms 1 2 3 18 191 2 3 18 19
One subframe
71.3ms
71.9ms
Normal Prefix
4.69ms
5.2ms
Frequency
Domain
View
83ms
Extended Prefix
Time-domain
View
13.9ms

16. OFDM
LTE uses OFDM for the downlink – that is, from the base station to the terminal. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. OFDM uses a large number of narrow sub-carriers for multi-carrier transmission.
The basic LTE downlink physical resource can be seen as a time-frequency grid. In the frequency domain, the spacing between the subcarriers, Δf, is 15kHz. In addition, the OFDM symbol duration time is 1/Δf + cyclic prefix. The cyclic prefix is used to maintain orthogonality between the sub-carriers even for a time-dispersive radio channel.
One resource element carries QPSK, 16QAM or 64QAM. With 64QAM, each resource element carries six bits.
The OFDM symbols are grouped into resource blocks. The resource blocks have a total size of 180kHz in the frequency domain and 0.5ms in the time domain. Each 1ms Transmission Time Interval (TTI) consists of two slots (Tslot).
In E-UTRA, downlink modulation schemes QPSK, 16QAM, and 64QAM are available.

17. SC-FDMA
The LTE uplink transmission scheme for FDD and TDD mode is based on SC-FDMA (Single Carrier Frequency Division Multiple Access).
This is to compensate for a drawback with normal OFDM, which has a very high Peak to Average Power Ratio (PAPR). High PAPR requires expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and also drains the battery faster.
SC-FDMA solves this problem by grouping together the resource blocks in such a way that reduces the need for linearity, and so power consumption, in the power amplifier. A low PAPR also improves coverage and the cell-edge performance.
Still, SC-FDMA signal processing has some similarities with OFDMA signal processing, so parameterization of downlink and uplink can be harmonized.

18. SC-FDMA
Localized Mapping and Distributed Mapping

19. User Plane Protocol Stack
PDCP – Packet Data Convergence Protocol
RLC – Radio Link Control
GTP-U – GPRS Tunneling Protocol – User Plane

20. Control Plane Protocol Stack
NAS – Non-Access Stratum
RRC – Radio Resource Control
PDCP – Packet Data Convergence Protocol
RLC – Radio Link Control
STCP – Stream Transport Control Protocol

21. Layer 2
The service access points between the physical layer and the MAC sublayer provide the transport channels.
The service access points between the MAC sublayer and the RLC sublayer provide the logical channels.
Radio bearers are defined on top of PDCP layer. Multiplexing of several logical channels on the same transport channel is possible.
There are two levels of re-transmissions for providing reliability, namely, the Hybrid Automatic Repeat request (HARQ) at the MAC layer and outer ARQ at the RLC layer. The outer ARQ is required to handle residual errors that are not corrected by HARQ. A N-process stop-and-wait HARQ is employed that has asynchronous re-transmissions in the DL and synchronous re-transmissions in the UL. Synchronous HARQ means that the re-transmissions of HARQ blocks occur at pre-defined periodic intervals. Hence, no explicit signaling is required to indicate to the receiver the retransmission schedule. Asynchronous HARQ offers the flexibility of scheduling re-transmissions based on air interface conditions. ARQ retransmissions are based on RLC status reports and HARQ/ARQ interaction.
The three sublayers are Medium access Control(MAC) Radio Link Control(RLC) Packet Data Convergence Protocol(PDCP)
[Source: E-UTRAN Architecture(3GPP TR ]

22. Layer 2 MAC (media access control) protocol
handles uplink and downlink scheduling and HARQ signaling.
Performs mapping between logical and transport channels.
RLC (radio link control) protocol
focuses on lossless transmission of data.
In-sequence delivery of data.
Provides 3 different reliability modes for data transport. They are
Acknowledged Mode (AM)-appropriate for non-RT (NRT) services such as file downloads.
Unacknowledged Mode (UM)-suitable for transport of Real Time (RT) services because such services are delay sensitive and cannot wait for retransmissions
Transparent Mode (TM)-used when the PDU sizes are known a priori such as for broadcasting system information.

23. Layer 2 PDCP (packet data convergence protocol)
handles the header compression and security functions of the radio interface
RRC (radio resource control) protocol
handles radio bearer setup
active mode mobility management
Broadcasts of system information, while the NAS protocols deal with idle mode mobility management and service setup

24. Three Types of Channels in LTE
In GMS only logical and physical
In LTE:
Logical Channels – what type of information is transported
Control x 5
Traffic x 2
Transport Channels – how is the information transported
Modulation, coding, antenna port
Physical Channels – where is the information transported
What resource blocks are allocated

25. LTE Downlink Channels Paging Control Channel Paging Channel
Physical Downlink Shared Channel

26. LTE Uplink Channels CQI report Random Access Channel
Physical Uplink Shared Channel
Physical Radio Access Channel

27. LTE Downlink Logical Channels

28. LTE Downlink Transport Channel

29. LTE Downlink Transport Channel

30. LTE Downlink Physical Channels

31. LTE Downlink Physical Channels

32. LTE Uplink Logical Channels

33. LTE Uplink Transport Channel

34. LTE Uplink Physical Channels

35. LTE Advanced Features 100MHz Bandwidth supported 1Gbps DL, 500 Mbps UL
Carrier Aggregation
Relays

36. Carrier Aggregation

37. Carrier Aggregation

38. Enhanced Techniques to Extend Coverage Area and/or Data Rates

39. LTE vs. LTE-Advanced