Ttalteoverview 100923032416 Phpapp01 (1)

3GPP R8 LTE Overview

조봉열, Bong Youl (Brian) Cho
brian.cho@intel.com
Intel Corporation

Contents
Technology Evolution

OFDM(A) and SC-FDMA

LTE Overview
LTE Radio Interface Architecture
LTE Downlink Transmission
LTE Uplink Transmission
LTE Cell Search

Summary

LTE/MIMO 표준기술 2

Worldwide Mobile Users
Number Percentage
cdmaOne 2,512,409 0.06%
CDMA2000 1X 309,507,900 7.18%
CDMA2000 1xEV-DO 121,821,983 2.83%
CDMA2000 1xEV-DO Rev. A 13,912,386 0.32%
Subtotal for 3GPP2 447,754,678 10.39%
GSM 3,449,010,903 80.02%
WCDMA 255,773,412 5.93%
WCDMA HSPA 132,079,727 3.06%
TD-SCDMA 825,044 0.02%
Subtotal for 3GPP 3,837,689,086 89.03%
Subtotal for 3GPP except GSM 388,678,183 9.02%
TDMA 753,411 0.02%
PDC 2,752,436 0.06%
iDEN 21,361,981 0.50%
Total 4,310,311,592
* Data supplied by GSMA Mobile Infolink on Aug/07/2009


3GPP Standards Evolution
Ongoing GERAN Evolution
GERAN
GPRS EGPRS GERAN Evolution
DL PDR: 50 kbps DL PDR: 236 kbps SAIC
MSRD
UL PDR: 21 kbps UL PDR: 118 kbps PS Handover
Dual Carrier

Ongoing
UMTS R5 HSDPA R6 HSUPA R7 HSPA R8 HSPA HSPA Evolution
WCDMA (5MHz) (5 MHz) Evolution Evolution
(5MHz) DL PDR: 14 Mbps DL PDR: 14 Mbps (5 MHz) (5 MHz)
DL PDR: 384 kbps UL PDR: 384 kbps UL PDR: 5.7 Mbps DL PDR: 28.8 Mbps DL PDR: 43.2 Mbps
UL PDR: 64 kbps UL PDR: 11.5 Mbps UL PDR: 11.5 Mbps

R7 LTE R8
LTE/SAE R9 &
Feasibility LTE-Adv
Study (1.4-20MHz)
(1.4-
(1.25-20MHz)
(1.25-
DL PDR: ≥ 100 Mbps (R10)…
UL PDR: ≥ 50 Mbps

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009+


Technology Evolution Path
3G 3.5G~3.99G IMT-Adv?

2005 2006 2007-2009 2010+
3G Technology Evolution

HSPA+ (R7/R8)
WCDMA (R99) HSDPA (R5) LTE-Adv ?
3GPP LTE (R8)

EVDO R.B
EVDO R.0 EVDO R.A ?
3GPP2 UMB

Wi-Fi 802.16e 802.16e
802.16m ?
OFDM OFDMA MIMO-OFDMA (WiMAX R2.0)
(WiMAX R1.0)

Broadband Wireless Technology Evolution


Advancement For High Data Rate

3.5G 4G
2G, 3G
(HSDPA,EVDO) (LTE,WiMAX)

Access Scheme CDMA OFDM(A)

QPSK,16QAM,
Modulation QPSK Up to 16QAM
64QAM
Link Adaptation Mainly PC Mainly AMC with channel-aware scheduler
ARQ without soft
ARQ HARQ with soft combining
combining
Handover SHO HHO
FDD,
Duplexing FDD
TDD is emerging

Antenna Various Antenna
Rx Antenna Diversity
Technology Diversity, MIMO, BF


ISI Prevents High Data Rate?
In general, ISI prevents “HIGH DATA RATE”
Symbol rate increase Ts decrease severe ISI
Symbol rate decrease Ts increase less ISI

Multipath profile in the wireless channel
(which is already given)

time

System#1 s1 s2

Ts
System#2 s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 s11 s12 s13 s14 s15 s16

Ts

• System#2 achieves 10x higher data rate by using 10x more spectrum (BW)
• However, at the same time, system#2 suffers 10x more severe ISI due to
short symbol duration compared to the multipath profile in the time domain

Multicarrier to “Minimize” ISI Effect
Ways to “minimize” inter-symbol interference:
Reduce the symbol rate, but data rate goes down too
Equalizers, but equalization is processor intensive & expensive

We are talking about
“Broadband Wireless” which
requires high data rate

Solution:
Transmit data over multiple carrier frequencies in parallel
Narrow, slower channels are MUCH LESS vulnerable to ISI thanks to long symbol duration compared to
the multipath delay in time domain
OFDM splits data into parallel, independent, narrowband channels (“subcarriers”)
Expensive adaptive equalizers are not required


Guard Interval To “Remove” ISI


Cyclic Prefix for Guard Interval


More on CP (Cyclic Prefix)

OFDM guarantee no interference ‘between’ subsequent OFDM symbols
OFDM allows ISI ‘within’ one OFDM symbol

Then, how can we remove ISI ‘within’ each OFDM symbol?


Circular Convolution
Circular convolution

where is a periodic version of x[n] with period L.

DFT

The duality b/w circular convolution in the time domain and simple multiplication
in the frequency domain is a property unique to DFT
The above simple formula describes an ISI-free channel in the frequency
domain, where each input symbol X[m] is simply scaled by a complex value
H[m]
It is trivial to recover the input symbol by simply computing


Frequency Domain Model of OFDM Tx/Rx

One-tap EQ


OFDMA: (1) Better BW Utilization
Cell center area: mostly BW-limited region
Cell edge area: mostly power-limited region
To better utilize the resource FDM-based access is required on top of TDM-based access

Enhance uplink link budget!
Active subcarriers are divided into subsets called “resource block”
When subscriber uses very few resource blocks,
It can concentrate all transmitting power (e.g. 200mW) in the used resource blocks
It will have additional gain on uplink
10*log10(Fs), where Fs is the power concentration factor

200mW

200mW

Total System BW


OFDMA: (2) Freq. Domain Scheduling
Loading gain by “frequency selective scheduling”

Localized subcarrier assignment Distributed subcarrier assignment


DL Channel Dependent Scheduling
in time and frequency domains


OFDMA: (3) Interference Coordination
Flexible Fractional Frequency Reuse

Cell-A

Power
A1 A2 A3 A4 A5 B1 B2 B3 B4 C1 C2 C3 C4

B5 C5

weak users good users

A1 A2 A3 A4 A5 B2 B3 B4 B5 C1 C2 C3 C4 C5
Cell-B
B1

good user weak user

C1 C2 C3 C4 C5
Cell-C
A1 A2 A3 A4 A5 B1 B2 B3 B4 B5

good users weak users


A Brief History of OFDM*
1966: Chang shows that multicarrier modulation can solve the multipath
problem without reducing data rate
R. W. Chang, “Synthesis of band-limited orthogonal signals for multichannel
data transmission”, Bell Systems Technical Journal, 45:1775-1796, Dec. 1966
1971: Weinstein and Ebert show that multicarrier modulation can be
accomplished using a DFT
S. Weinstein and P. Ebert, “Data Transmission by frequency-division
multiplexing using the discrete Fourier transform”, IEEE Transactions on
Communications, 19(5): 628-634, Oct. 1971
1985: Cimini at Bell Labs identifies many of the key issues in OFDM
transmission and does a proof-of-concept design
L. J. Cimini, “Analysis and simulation of a digital mobile channel using
orthogonal frequency division multiplexing”, IEEE Transactions on
Communications, 33(7): 665-675, July 1985
1993: DSL adopts OFDM
1999: IEEE 802.11 releases the 802.11a standard for OFDM

LTE/MIMO 표준기술 * Jeffrey Andrews, et al., Fundamentals of WiMAX, Prentice Hall, 2007
20

OFDM in Communication Systems
3GPP LTE
3GPP2 UMB
IEEE 802.16e Mobile WiMAX
DAB, DVB-T, DVB-H
T-DMB
MediaFlo
IEEE 802.11a WLAN
xDSL
PLC
Etc…

SC-FDMA Transmitter
SC-FDMA is a new hybrid modulation technique combining the low PAR
single carrier methods of current systems with the frequency allocation
flexibility and long symbol time of OFDM
SC-FDMA is sometimes referred to as Discrete Fourier Transform Spread
OFDM = DFT-SOFDM
Signal at each subcarrier is linear combination of all M symbols

Coded symbol rate= R Spreading

Sub-carrier CP
DFT Mapping IFFT insertion

Msymbols Size-M

Low High Low
Size-N
PAPR PAPR PAPR


CM of OFDMA & SC-FDMA

OFDMA

SC-FDMA
16QAM

SC-FDMA
QPSK

SC-FDMA
pi/2-BPSK


R8 LTE DL OFDMA


R8 LTE UL SC-FDMA (LFDMA)


Comparing OFDM and SC-FDMA*
QPSK example using N=4 subcarriers
How OFDM and SC-FDMA would be used to transmit a sequence of 8
QPSK symbols

* Moray Rumney (Agilent), “Concepts of 3GPP LTE”, Live Webinar, Sep. 20th, 2007.

Comparing OFDM and SC-FDMA


Time Domain Equalizer

In general, the complexity of time-discrete equalizer with linear equalization
implementation (as above) grows relatively rapidly with the bandwidth of the
signal to be equalized
A more wideband signal is subject to relatively more frequency selectivity or,
equivalently, more time dispersion. This implies the equalizer needs to have a larger
span.
A more wideband signal leads to a correspondingly higher sampling rate for the
received signal. Thus, also the receiver-filter processing needs to be carried out with
a correspondingly higher rate.


Frequency Domain Equalizer

Frequency domain equalization basically consists of
A size-N DFT/FFT
N complex multiplications (the frequency-domain filter)
A size-N inverse DFT/FFT
Especially in extensive frequency selective channel, the complexity of the
frequency domain equalization can be significantly less than that of time
domain equalization
* D. Falconer, et al., “Frequency domain equalization for single-carrier broadband
LTE/MIMO 표준기술 wireless systems,” IEEE Communication Magazine, vol.40, no.4, April 2002 29

3GPP Specifications
LTE Study Phase (Release 7)
TR 25.813, E-UTRA and E-UTRAN: Radio interface protocol aspects
TR 25.814, Physical layer aspects for E-UTRA
TR 25.912, Feasibility study for E-UTRA and E-UTRAN
TR 25.913, Requirements for E-UTRA and E-UTRAN
LTE Specifications (Release 8)
TS 36.101, E-UTRA: UE radio transmission and reception
TS 36.104, E-UTRA: BS radio transmission and reception
TS 36.201, E-UTRA: LTE Physical Layer - General Description
TS 36.211, E-UTRA: Physical channels and modulation
TS 36.212, E-UTRA: Multiplexing and channel coding
TS 36.213, E-UTRA: Physical layer procedures
TS 36.214, E-UTRA: Physical layer – Measurements
TS 36.300, E-UTRA and E-UTRAN: Overall description; Stage 2
TS 36.302, E-UTRA: Services provided by the physical layer
TS 36.306, E-UTRA: UE Radio Access Capabilities
TS 35.321, E-UTRA: Medium Access Control (MAC) protocol specification
TS 36.323, E-UTRA: Packet Data Convergence Protocol (PDCP) specification
TS 36.331, E-UTRA: Radio Resource Control (RRC); Protocol specification
TS 36.401, E-UTRAN: Architecture description
TR 36.938, E-UTRAN: Improved network controlled mobility between LTE and 3GPP2/mobile
WiMAX radio technologies
TR 36.956, E-UTRA; Repeater planning guidelines and system analysis


3GPP LTE
LTE focus is on:
enhancement of the Universal Terrestrial Radio Access (UTRA)
optimisation of the UTRAN architecture
With HSPA (downlink and uplink), UTRA will remain highly competitive for
several years
LTE project aims to ensure the continued competitiveness of the 3GPP
technologies for the future (started at Nov. 2004)
Motivations
Need for PS optimized system
Evolve UMTS towards packet only system
Need for higher data rates
Can be achieved with HSDPA/HSUPA and/or new air interface defined by 3GPP LTE
Need for high quality of services
Use of licensed frequencies to guarantee quality of services
Always-on experience (reduce control plane latency significantly)
Reduce round trip delay
Need for cheaper infrastructure
Simplify architecture, reduce number of network elements
Most data users are less mobile


Detailed Requirements*
Peak data rate
Instantaneous downlink peak data rate of 100 Mb/s within a 20 MHz downlink
spectrum allocation (5 bps/Hz)
Instantaneous uplink peak data rate of 50 Mb/s (2.5 bps/Hz) within a 20MHz
uplink spectrum allocation)
Control-plane latency
Transition time of less than 100 ms from a camped state, such as Release 6
Idle Mode, to an active state such as Release 6 CELL_DCH
Transition time of less than 50 ms between a dormant state such as Release 6
CELL_PCH and an active state such as Release 6 CELL_DCH
Control-plane capacity
At least 200 users per cell should be supported in the active state for spectrum
allocations up to 5 MHz
User-plane latency
Less than 5 ms in unload condition (ie single user with single data stream) for
small IP packet

* 3GPP TR 25.913, Technical Specification Group RAN: Requirements for Evolved
LTE/MIMO 표준기술 UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN), Release 8, Version 8.0.0, Dec. 2008
33

Detailed Requirements
Average user throughput
Downlink: average user throughput per MHz, 3 to 4 times Release 6 HSDPA
Uplink: average user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink
Cell edge user throughput
Downlink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 HSDPA
Uplink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 Enhanced Uplink
Spectrum efficiency
Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3 to 4
times Release 6 HSDPA )
Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to 3 times
Release 6 Enhanced Uplink
Mobility
E-UTRAN should be optimized for low mobile speed from 0 to 15 km/h
Higher mobile speed between 15 and 120 km/h should be supported with high
performance
Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350
km/h (or even up to 500 km/h depending on the frequency band)
Coverage
Throughput, spectrum efficiency and mobility targets above should be met up to 5 km
cells, and with a slight degradation up to 30 km cells. Cells range up to 100 km should
not be precluded.


Detailed Requirements
Spectrum flexibility
E-UTRA shall operate in spectrum allocations of different sizes, including 1.25 MHz, 2.5
MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplink and downlink. Operation
in paired and unpaired spectrum shall be supported
Co-existence and Inter-working with 3GPP RAT (UTRAN, GERAN)
Architecture and migration
Single E-UTRAN architecture
The E-UTRAN architecture shall be packet based, although provision should be made
to support systems supporting real-time and conversational class traffic
E-UTRAN architecture shall support an end-to-end QoS
Backhaul communication protocols should be optimized
Radio Resource Management requirements
Enhanced support for end to end QoS
Support of load sharing and policy management across different Radio Access
Technologies
Complexity
Minimize the number of options
No redundant mandatory features


LTE System Performance
Peak Data Rate

150.8 baseline
302.8
51.0
75.4 baseline


LTE System Performance – cont’d
Downlink Spectral Efficiency

Uplink Spectral Efficiency


LTE Key Features
Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)
Less critical AMP efficiency in BS side Making MS cheap as
Concerns on high RX complexity in terminal side much as possible by
Uplink: SC-FDMA (Single Carrier-FDMA) moving all the burdens
Less critical RX complexity in BS side from MS to BS
Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage)
Single node RAN (eNB)
Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA) <cf> H-FDD MS
User data rates
DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO
UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO
Radio frame: 10 ms (= 20 slots)
Sub-frame: 1 ms (= 2 slots)
Slot: 0.5 ms
TTI: 1 ms
HARQ
Incremental redundancy is used as the soft combining strategy
Retransmission time: 8 ms
Modulation
DL/UL data channel = QPSK/16QAM/64QAM


LTE Key Features – cont’d
MIMO SM (Spatial Multiplexing), Beamforming, Antenna Diversity
Min requirement: 2 eNB antennas & 2 UE rx antennas
DL: Single-User MIMO up to 4x4 supportable
UL: 1x2 MU-MIMO, Optional 2x2 SU-MIMO
Resource block
12 subcarriers with subcarrier BW of 15kHz “180kHz”
24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS)
Subcarrier operation
Frequency selective by localized subcarrier
Frequency diversity by distributed subcarrier & frequency hopping
Frequency hopping
Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol)
Inter-TTI: across retransmissions
Bearer services
Packet only – no circuit switched voice or data services are supported
Voice must use VoIP
MBSFN
Multicast/Broadcast over a Single Frequency Network
To support a Multimedia Broadcast and Multicast System (MBMS)
Time-synchronized common waveform is transmitted from multiple cells for a given duration
The signal at MS will appear exactly as a signal transmitted from a single cell site and subject to multi-path
Not only “improve the received signal strength” but also “eliminate inter-cell interference”


E-UTRAN Architecture*

LTE/MIMO 표준기술 * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall description; Stage 2, Release 9, V9.0.0, June 2009
40

Functional Split b/w E-UTRAN and EPC*

LTE/MIMO 표준기술 * 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall description; Stage 2, Release 9, V9.0.0, June 2009
41

3GPP Architecture Evolution
Towards Flat Architecture


E-UTRA Frequency Band*

Japan, Korea?

Korea?

Europe
Korea?

US

US

China?

* 3GPP TS 36.101, E-UTRA: UE radio transmission
LTE/MIMO 표준기술 and reception, Release 9, V9.0.0, June 2009 43

E-UTRA Channel Bandwidth*
1RB = 180kHz 6RBs = 1.08MHz, 100RBs = 18MHz
6RBs (72 subcarriers) with 128 FFT, 100RBs (1200 subcarriers) with 2048 FFT

* 3GPP TS 36.101, E-UTRA: UE radio transmission
LTE/MIMO 표준기술 and reception, Release 9, V9.0.0, June 2009 44

TS 36.101 for UE, 36.104 for eNB
Transmitter characteristics
Transmit power
Output power dynamics
Transmit signal quality
Output RF spectrum emissions
Transmit intermodulation
Receiver characteristics
Reference sensitivity power level
Maximum input level
Adjacent Channel Selectivity (ACS)
Blocking characteristics
Intermodulation characteristics
Spurious emissions
Performance requirement (below is examples for UE)
Dual-antenna receiver capability
Simultaneous unicast and MBMS operations
Demodulation of PDSCH (Cell-Specific Reference Symbols)
Minimum Requirement QPSK/16QAM/64QAM
Transmit diversity performance
Open-loop spatial multiplexing performance
Closed-loop spatial multiplexing performance
MU-MIMO


Conformance Test
TS 36.141 Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS) conformance
testing
TS 36.143 Evolved Universal Terrestrial Radio Access (E-UTRA); FDD repeater conformance testing

TS 36.508 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC);
Common test environments for User Equipment (UE) conformance testing
TS 36.509 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC);
Special conformance testing functions for User Equipment (UE)

TS 36.521-1 Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE)
conformance specification; Radio transmission and reception; Part 1: Conformance testing
conformance specification; Radio transmission and reception; Part 2: Implementation Conformance
Statement (ICS)
conformance specification; Radio transmission and reception; Part 3: Radio Resource Management
(RRM) conformance testing
TS 36.523-1 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC);
User Equipment (UE) conformance specification; Part 1: Protocol conformance specification
User Equipment (UE) conformance specification; Part 2: ICS
User Equipment (UE) conformance specification; Part 3: Test suites


LTE Radio Interface Architecture

LTE Protocol Architecture (DL)


Logical Channels: “type of information it carries”
Control Channels
Broadcast Control Channel (BCCH)
used for transmission of system information from the network to all UEs in a cell
Paging Control Channel (PCCH)
used for paging of UEs whose location on cell level is not known to the network
Common Control Channel (CCCH)
used for transmission of control information in conjunction with random access, i.e.,
used for UEs having no RRC connection
Dedicated Control Channel (DCCH)
used for transmission of control information to/from a UE, i.e., used for UEs having
RRC connection (e.g. handover messages)
Multicast Control Channel (MCCH)
used for transmission of control information required for reception of MTCH
Traffic Channels
Dedicated Traffic Channel (DTCH)
used for transmission of user data to/from a UE
Multicast Traffic Channel (MTCH)
used for transmission of MBMS services

* 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall
LTE/MIMO 표준기술 description; Stage 2, Release 9, V9.0.0, June 2009 49

Transport Channels: “how”, “with what characteristics”
Downlink
Broadcast Channel (BCH)
A fixed TF
Used for transmission of parts of BCCH, so called MIB
Paging Channel (PCH)
Used for transmission of paging information from PCCH
Supports discontinuous reception (DRX)
Downlink Shared Channel (DL-SCH)
Main transport channel used for transmission of downlink data in LTE
Used also for transmission of parts of BCCH, so called SIB
Supports discontinuous reception (DRX)
Multicast Channel (MCH)
Used to support MBMS
Uplink
Uplink Shared Channel (UL-SCH)
Uplink counterpart to the DL-SCH
Random Access Channel(s) (RACH)
Transport channel which doesn’t carry transport blocks
Collision risk

* 3GPP TS 36.300, E-UTRA and E-UTRAN; Overall
LTE/MIMO 표준기술 description; Stage 2, Release 9, V9.0.0, June 2009 50

DL Physical Channels
Physical Downlink Shared Channel (PDSCH)
실제 downlink user data를 전송하기 위한 transport channel인 DL-SCH와 paging 정보를 전송
하기 위한 transport channel인 PCH가 매핑
동적 방송 정보인 SI (System Information) 값들도 RRC 메시지 형태로 DL-SCH를 통해 전송되
므로 이 역시 PDSCH로 매핑
이 경우는 전체 셀 영역으로 도달될 수 있는 능력이 요구되기도 함
Physical Broadcast Channel (PBCH)
UE가 cell search과정을 마친 후에 최초로 검출하는 채널로서, 다른 물리 계층 채널들을 수신하
기 위하여 반드시 필요한 기본적인 시스템 정보들인 MIB (Master Information Block)를 전송하
기 위한 transport channel인 BCH가 매핑
Physical Multicast Channel (PMCH)
방송형 데이터를 전송하기 위한 transport channel 인 MCH가 매핑
Physical Control Format Indicator Channel (PCFICH)
매 subframe마다 전송, only one PCFICH in each cell
Informs UE about CFI which indicates the number of OFDM symbols used for PDCCHs
transmission
Physical Downlink Control Channel (PDCCH)
Informs UE about resource allocation of PCH and DL-SCH
HARQ information related to DL-SCH
UL scheduling grant
Physical HARQ Indicator Channel (PHICH)
Carries HARQ ACK/NACKs in response to UL transmission


UL Physical Channels
Physical Uplink Shared Channel (PUSCH)
Uplink counterpart of PDSCH
Carries UL-SCH
Physical Uplink Control Channel (PUCCH)
Carries HARQ ACK/NAKs in response to DL transmission
Carries Scheduling Request (SR)
Carries channel status reports such as CQI, PMI and RI
At most one PUCCH per UE
Physical Random Access Channel (PRACH)
Carries the random access preamble


LTE Channel Mapping

Downlink

Uplink


Terminal States

RRC_CONNECTED
Active state where UE is connected to a specific cell
One or several IP addresses as well as an identity of the terminal, Cell Radio-Network Temporary
Identifier (C-RNTI), used for signaling purposes b/w UE and network, have been assigned
Two substates: IN_SYNC & OUT_OF_SYNC whether or not uplink is synchronized to the network
RRC_IDLE
Low activity state where US sleeps most of the time to reduce battery consumption
Uplink synchronization is not maintained and hence only uplink transmission that may take place is
random access
In downlink, US can periodically wake up to be paged for incoming calls
UE keeps its IP address(es) and other internal info to rapidly move to RRC_CONNECTED


Example of LTE Data Flow


Frame Structure: Type 1 for FDD

One radio frame, Tf = 307200×Ts=10 ms

One slot, Tslot = 15360×Ts = 0.5 ms

#0 #1 #2 #3 #18 #19

One subframe

where, Ts = 1/(15000 x 2048) seconds “the smallest time unit in LTE”
Tf = 307200 x Ts = 10 ms


Frame Structure: Type 2 for TDD


Frame Structure: FDD/TDD


DL Slot Structure Tslot

DL
N RB : Downlink bandwidth configuration,
RB
expressed in units of N sc DL
N symb

RB
N sc : Resource block size in the k = N RB N sc − 1
DL RB

frequency domain, expressed as a
number of subcarriers
N symb × N sc
DL RB

DL
N symb: Number of OFDM symbols in an
downlink slot

(k , l )

RB
N RB × N sc
RB
N sc
DL

The minimum RB the eNB uses for LTE
scheduling is “1ms (1subframe) x 180kHz
(12subcarriers @ 15kHz spacing)”

k =0
l=0 l= DL
N symb −1

Definitions
Resource Grid
DL RB DL
Defined as N RB N sc subcarriers in frequency domain and N symb OFDM symbols in time domain
DL
The quantity N RB depends on the DL transmission BW configured in the cell and shall fulfill
6 ≤ N RB ≤ 110
DL

DL
The set of allowed values for N RB is given by TS 36.101, TS 36.104
Resource Block (1 RB = 180 kHz)
Defined as N sc “consecutive” subcarriers in frequency domain and N symb “consecutive” OFDM
RB DL

symbols in time domain
Corresponding to one slot in the time domain and 180 kHz in the frequency domain

Resource Element
Uniquely defined by the index pair (k, l ) in a slot where k = 0,..., N RB N sc − 1 and l = 0,..., N symb − 1
DL RB DL

are the indices in the frequency and time domain, respectively


Normal CP & Extended CP


PRB and VRB (LVRB, DVRB)
Physical resource blocks are numbered from 0 to N RB − 1 in the frequency domain.
DL

The relation between the physical resource block number nPRB in the frequency domain
and resource elements (k , l ) in a slot is given by
⎢ k ⎥
nPRB = ⎢ RB ⎥
⎢ N sc ⎥
⎣ ⎦
A virtual resource block is of the same size as a physical resource block.
Two types of virtual resource blocks are defined: LVRB and DVRB
Virtual resource blocks of localized type are mapped directly to PRBs such that virtual
resource block nVRB corresponds to physical resource block nPRB = nVRB .
Virtual resource blocks are numbered from 0 to N VRB − 1 , where N VRB = N RB .
DL DL DL


DVRB
Virtual resource blocks of distributed type are mapped to PRBs as follows
Consecutive VRBs are not mapped to PRBs that are consecutive in the frequency domain
Even a single VRB pair is distributed in the frequency domain
The exact size of the frequency gap depends on the overall downlink cell BW


Resource-element groups (REG)

n+5
n+6
n+7
Basic unit for mapping of PCFICH,
PHICH, and PDCCH
Resource-element groups are used
for defining the mapping of control

n+3
n+4
channels to resource elements.
Mapping of a symbol-quadruplet

n+0
n+1
n+2
z (i), z (i + 1), z (i + 2), z (i + 3) onto a resource
-element group is defined such that
elements z (i) are mapped to resource
elements (k , l ) of the resource-element

n+5
n+4

n+6
group not used for cell-specific
reference signals in increasing order
of l and k

n+3
n+0
n+1
n+2


DL Physical Channel Processing
code words layers antenna ports

Modulation Resource OFDM signal
Scrambling element mapper
Mapper generation
Layer
Precoding
Mapper
Modulation Resource OFDM signal
Scrambling element mapper
Mapper generation

scrambling of coded bits in each of the code words to be transmitted on a
physical channel
modulation of scrambled bits to generate complex-valued modulation symbols
mapping of the complex-valued modulation symbols onto one or several
transmission layers
precoding of the complex-valued modulation symbols on each layer for
transmission on the antenna ports
mapping of complex-valued modulation symbols for each antenna port to
resource elements
generation of complex-valued time-domain OFDM signal for each antenna port


Channel Coding

Turbo code
PCCC (exactly the same as in WCDMA/HSPA)
QPP (quadratic polynomial permutation) interleaver


Modulation


DL Layer Mapping and Precoding
Explained in MIMO session


DL OFDM Signal Generation
OFDM Parameters
0 ≤ t < (N CP ,l + N )× Ts
N = 2048 for ∆f=15kHz
N = 4096 for ∆f=7.5kHz

Check with resource block parameters
(160+2048) x Ts = 71.88us
(144+2048) x Ts = 71.35us
71.88us + 71.35us x 6 = 0.5ms
Normal Cyclic Prefix = 160 Ts = 5.2 us
Normal Cyclic Prefix = 144 Ts = 4.7 us
Extended Cyclic Prefix = 512 Ts = 16.7 us
Extended Cyclic Prefix for MBMS = 1024 Ts = 33.3 us


DL Physical Channels & Signals
Physical channels
Physical Downlink Shared Channel (PDSCH)
Physical Broadcast Channel (PBCH)
Physical Multicast Channel (PMCH)
Physical Control Format Indicator Channel (PCFICH)
Physical Downlink Control Channel (PDCCH)
Physical HARQ Indicator Channel (PHICH)
Physical signals
Reference Signals
Cell-specific RS, associated with non-MBSFN transmission
Aid coherent detection (pilot)
Reference channel for CQI from UE to eNB
MBSFN RS, associated with MBSFN transmission
UE-specific RS
Synchronization Signals
Carries frequency and symbol timing synchronization
PSS (Primary SS) and SSS (Secondary SS)


DL Reference Signals
Cell-specific reference signals
Are transmitted in every downlink subframe, and span entire cell BW
Can be used for coherent demodulation of any downlink transmission
“except” when so-called non-codebook-based beamforming is used
Using antenna ports {0, 1, 2, 3}
MBSFN reference signals
Are used for channel estimation for coherent demodulation of signals being
transmitted by means of MBSFN
Using antenna port 4
UE-specific reference signals
Is specifically intended for channel estimation for coherent demodulation of
DL-SCH when non-codebook-based beamforming is used.
Are transmitted only within the RB assigned for DL-SCH to that specific UE
Using antenna port 5


Cell-Specific Reference Signals
When estimating the channel for a certain RB, UE may not only use the
reference symbols within that RB but also, in frequency domain, neighbor
RBs, as well as reference symbols of previously received slots/subframes
Pseudo-random sequence generation

rl ,ns (m) =
1
(1 − 2 ⋅ c(2m)) + j 1 (1 − 2 ⋅ c(2m + 1)), m = 0,1,...,2 N RB DL − 1
max,
2 2
is the slot number within a radio frame.
is the OFDM symbol number within the slot.
The pseudo-random sequence c(i) is a length-31 Gold sequence.
The complex values of reference symbols will vary b/w different reference-
symbol position and also b/w different cells. Thus, RS of a cell can be seen as
a cell-specific two-dimensional sequence with the period of one frame.
Regardless of cell BW, the reference signal sequence is defined assuming the
maximum possible LTE cell BW corresponding to 110 RBs in frequency
domain


Relationship with Cell Identity
504 unique Cell ID:
168(N1) Cell ID groups, 3 (N2) Cell ID within each group
Cell ID = 3xN1+N2 = 0 ~ 503 index
504 pseudo-random sequences
One to one mapping between the Cell ID and Pseudo-random sequences
Cell-specific Frequency Shift (N1 mod 6)
1 RE shift from current RS position in case of next Cell ID index
Each shift corresponds to 84 different cell identities, that is 6 shifts jointly cover all
504 cell identities.
Effective with RS boosting to enhance reference signal SIR by avoiding the collision
of boosted RSs from neighboring cells (assuming time synchronization)


Cell-Specific RS Mapping
R0 R0
One antenna port

R0 R0

R0 R0

R0 R0
l=0 l =6 l=0 l=6

Resource element (k,l)

R0 R0 R1 R1
Two antenna ports

R0 R0 R1 R1
Not used for transmission on this antenan port

R0 R0 R1 R1
Reference symbols on this antenna port

R0 R0 R1 R1
l =0 l=6 l =0 l =6 l =0 l =6 l =0 l =6

R0 R0 R1 R1 R2 R3 R3
Four antenna ports

R0 R0 R1 R1 R2

R0 R0 R1 R1 R2 R3 R3

R0 R0 R1 R1 R2
l =0 l =6 l =0 l =6 l=0 l =6 l=0 l=6 l=0 l =6 l=0 l=6 l =0 l=6 l =0 l=6

LTE/MIMO 표준기술
even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots even-numbered slots odd-numbered slots
75
Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3

MBSFN RS Mapping


UE-specific RS on top of Cell-specific RS
UE-specific RS (antenna port 5)
12 symbols per RB pair
DL CQI estimation is always based on cell-specific RS (common RS)


PCFICH
The number of OFDM symbols used for control channel can be varying per TTI
CFI (Control Format Indication)
Information about the number of OFDM symbols (1~4) used for transmission of PDCCHs in a
subframe
PCFICH carries CFI

2 bits 32 bits (block coding) 32 bits (cell specific scrambling) 16 symbols (QPSK)
Mapping to resource elements: 4 REG (16 RE excluding RS) in the 1st OFDM symbol
Spread over the whole system bandwidth
To avoid the collisions in neighboring cells, the location depends on cell identity
Transmit diversity is applied which is identical to the scheme applied to BCH


PCFICH REG Mapping Cell ID

Example for 5 MHz BW LTE
DL
N RB = 25 (number of REGs = 50)
RB
N sc = 12

REG


PCFICH Processing


PHICH
HARQ ACK/NAK in response to UL transmission
HI codewords with length of 12 REs = 4 (Walsh spreading) x 3 (repetition)
3 groups of 4 contiguous REs (not used for RS and PCFICH)
BPSK modulation with I/Q multiplexing
SF4 x 2 (I/Q) = 8 PHICHs in normal CP

Cell-specific scrambling
Tx diversity, the same antenna ports as PBCH
Typically, PHICH is transmitted in the first OFDM symbol only
For FDD, an uplink transport block received in subframe n should be acknowledged on the
PHICH in subframe n+4


PHICH REG Mapping Cell ID

⎧
⎪
(⎣N cell
ID ⎦ )
⋅ nli′ n1 + m' mod nli′ i=0
⎪
ni = ⎨ (⎣N cell
ID ⋅ nli′ n1 ⎦ + m'+ ⎣nl ′ 3⎦)mod nl ′
i i
i =1
⎪
⎪
⎩
(⎣N cell
ID ⋅ nli′ n1 ⎦ + m'+ ⎣2 nl ′ 3⎦)mod nl ′
i i
i=2
DL
N RB

DL
N RB = 25 (number of REGs = 50)
RB
N sc = 12

REG


PHICH Processing


symbol

PCFICH/PHICH RE Mapping

LTE/MIMO 표준기술 Subcarrier 85

PDCCH DCI Format
PDCCH is used to carry DCI where DCI includes;
Downlink scheduling assignments, including PDSCH resource indication, transport format, HARQ-
related information, and control information related to SM (if applicable).
Uplink scheduling grants, including PUSCH resource indication, transport format, and HARQ-
related information.
Uplink power control commands

DCI
Usage Details
Formats
0 UL grant For scheduling of PUSCH
1 For scheduling of one PDSCH codeword (SIMO, TxD)
For compact scheduling of one PDSCH codeword (SIMO, TxD) and random access procedure
1A
initiated by a PDCCH order
1B For compact scheduling of one PDSCH codeword with precoding information (CL single-rank)
DL
For very compact scheduling of one PDSCH codeword (paging, RACH response and dynamic
1C assignment
BCCH scheduling)
1D For compact scheduling of one PDSCH codeword with precoding & power offset information
2 For scheduling PDSCH to UEs configured in CL SM
2A For scheduling PDSCH to UEs configured in OL SM
3 Power For transmission of TPC commands for PUCCH/PUSCH with 2-bit power adjustment
3A control For transmission of TPC commands for PUCCH/PUSCH with single bit power adjustment


Downlink Assignment
Major contents of different DCI formats: not exhaustive
DCI format 0/1A indication [1 bit]
Distributed transmission flag [1 bit]
Resource-block allocation [variable]
For the first (or only) transport block
MCS [5 bit]
New-data indicator [1 bit]
Redundancy version [2 bit]
For the second transport block (present in DCI format 2 only)
MCS [5 bit]
Redundancy version [2 bit]
HARQ process number [3 bit for FDD]
Information related to SM (present in DCI format 2 only)
Pre-coding information [3 bit for 2 antennas, 6 bit for 4 antennas in CL-SM]
Number of transmission layer
HARQ swap flag [1 bit]
Transmit power control (TPC) for PUCCH [2 bit]
Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit]


Uplink Grants
Major contents of DCI format 0 for UL grants: not exhaustive
DCI format 0/1A indication [1 bit]
Hopping flag [1 bit]
Resource-block allocation [variable]
MCS [5 bit]
Phase rotation of UL demodulation reference signal [3 bit]
Channel-status request flag [1 bit]
Transmit power control (TPC) for PUSCH [2 bit]
Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit]
The time b/w reception of an UL scheduling grant on a PDCCH and the
corresponding transmission on UL-SCH are fixed
For FDD, the time relation is the same as for PHICH
Uplink grant received in downlink subframe n applies to uplink subframe n+4


PDCCH Processing
First n OFDM symbols
< 10RB: 2~4 OFDMA symbols
> 10RB: 1~3 OFDMA symbols 1/14~3/14 (10~20%) overhead
PDCCH format based on # of CCE (Control Channel Element, = 9 REGs)
Depending on the payload size of control information (DCI payload) & coding rate
Number of CCEs for each of PDCCH may vary and is not signaled, so UE has to blindly
determine this
search space: a set of candidate control channels formed by CCEs on a given aggregation
level {1, 2, 4, 8}, which UE is supposed to attempt to decode

User identification is based on “UE specific CRC (normal CRC with UE ID masking)”
Cell-specific scrambling, QPSK with tail-biting Conv. Code
Tx diversity, the same antenna ports as PBCH
Mapped to REG not assigned to PCFICH or PHICH


PDCCH Processing


System Information
Master information block (MIB) includes the following information:
Downlink cell bandwidth [4 bit]
PHICH duration [1 bit]
PHICH resource [2 bit]
System Frame Number (SFN) except two LBSs
Etc…
LTE defines different SIBs:
SIB1 includes info mainly related to whether an UE is allowed to camp on the cell. This includes info about the
operator(s) and about the cell (e.g. PLMN identity list, tracking area code, cell identity, minimum required Rx
level in the cell, etc), DL-UL subframe configuration in TDD case, and the scheduling of the remaining SIBs.
SIB1 is transmitted every 80ms.
SIB2 includes info that UEs need in order to be able to access the cell. This includes info about the UL cell
BW, random access parameters, and UL power control parameters. SIBs also includes radio resource
configuration of common channels (RACH, BCCH, PCCH, PRACH, PDSCH, PUSCH, PUCCH, and SRS).
SIB3 mainly includes info related to cell-reselection.
SIB4-8 include neighbor-cell-related info. (E-UTRAN, UTRAN, GERAN, cdma2000)
SIB9 contains a home eNB identifier
SIB10/11 contains ETWS (Earthquake and Tsunami Warning System) notification
More to be added
MIB mapped to PBCH
Other SIBs mapped to PDSCH


BCH on PBCH
To broadcast a certain set of cell and/or system-specific information
Requirement to be broadcast in the entire coverage area of the cell
BCH transmission
The coded BCH transport block is mapped to four subframes (slot #1 in subframe #0)
within a 40ms interval
40ms timing is blindly detected (no explicit signaling indicating 40ms timing)
Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from a
single reception, assuming sufficiently good channel conditions


BCH on PBCH – cont’d
Single (fixed-size) transport block per TTI (40 ms)
No HARQ
Cell-specific scrambling, BPSK with ½ tail-biting Conv. Code, Tx diversity(1,2,4)
BCH mapped to 4 OFDM symbols within a subframe in time-domain at 6 RBs
(72 subcarriers) excluding DC in freq-domain
PBCH is mapped into RE assuming RS from 4 antennas are used at eNB,
irrespective of the actual number of TX antenna
Different transmit diversity schemes per # of antennas
# of ant=2: SFBC
# of ant=4: SFBC + FSTD (Frequency Switching Transmit Diversity)
No explicit bits in the PBCH to signal the number of TX antennas at eNB
PBCH encoding chain includes CRC masking dependent on the number of
configured TX antennas at eNB
Blind detection of the number of TX antenna using CRC masking by UE


PBCH Processing


PDSCH Processing

1) RS
2) PSS & SSS
and BCH
3) PCFICH
4) PHICH
5) PDCCH
6) PDSCH


DL constellation & frame summary


LTE Uplink Key Features
SC-FDMA 사용
단말의 PAPR을 낮추어 커버리지를 증가시키기에 적합함
DFT size is limited to products of the integers 2, 3, and 5
(e.g. DFT sizes of 60, 72, and 96 are allowed but a DFT size of 84 is not allowed.)
No unused DC-subcarrier is defined
CAZAC (Constant Amplitude Zero Autocorrelation) sequence 사용
Reference signal 및 제어 정보 채널 전송 시 각 단말들의 신호를 구분하기 위하여 CDM
을 수행하는 경우 CAZAC sequence를 주로 사용
CAZAC sequence는 시간/주파수 차원에서 일정한 amplitude를 유지하는 특성을 가지
므로 단말의 PAPR을 낮추어 커버리지를 증가시키기에 적합함
MU-MIMO 지원
QPSK/16QAM/64QAM modulation 지원


UL Slot Structure Tslot

UL
N RB : Uplink bandwidth configuration,
RB
expressed in units of N sc UL
N symb

RB
N sc : Resource block size in the k = N RB N sc − 1
UL RB

frequency domain, expressed as a
number of subcarriers N symb × N sc
UL RB

UL
N symb : Number of SC-FDMA symbols in
an uplink slot
(k , l )

RB
N RB × N sc
RB
N sc
UL

k =0
l=0 l= UL
N symb −1

Definitions
Resource Grid
UL RB UL
Defined as N RB N sc subcarriers in frequency domain and N symb SC-FDMA symbols in time domain
UL
The quantity N RB depends on the UL transmission BW configured in the cell and shall fulfill
6 ≤ N RB ≤ 110
UL

UL
The set of allowed values for N RB is given by TS 36.101, TS 36.104
Resource Block
Defined as N sc “consecutive” subcarriers in frequency domain and N symb “consecutive” SC-
RB UL

FDMA symbols in time domain
Corresponding to one slot in the time domain and 180 kHz in the frequency domain

Resource Element
Uniquely defined by the index pair (k, l ) in a slot where k = 0,..., N RB N sc − 1 and
UL RB
l = 0,..., N symb − 1
UL

are the indices in the frequency and time domain, respectively


UL Physical Channels & Signals
UL physical channels
Physical Uplink Shared Channel (PUSCH)
Physical Uplink Control Channel (PUCCH)
Physical Random Access Channel (PRACH)

UL physical signals
An uplink physical signal is used by the physical layer but does not
carry information originating from higher layers
Two types of reference signals
UL demodulation reference signal (DRS) for PUSCH, PUCCH
UL sounding reference signal (SRS) not associated with PUSCH,
PUCCH transmission


UL Reference Signals
UL RS should preferably have the following properties:
Favorable auto- and cross-correlation properties
Limited power variation in freq-domain to allow for similar channel-estimation quality for all
frequencies
Limited power variation in time-domain (low cubic metric) for high PA efficiency
Sufficiently many RS sequences of the same length to avoid an unreasonable planning effort
Zadoff-Chu Sequence
Appeared in IEEE Trans. Inform. Theory in 1972
Poly-phase sequence
Constant amplitude zero auto correlation (CAZAC) sequence의 일종
Cyclic autocorrelations are zero for all non-zero lags, Non-zero cross-correlations
Constant power in both the frequency and the time domain
No restriction on code length N
π
⎧ − j 2N pn 2
⎪ e , when N is even
g p ( n) = ⎨ 2π
⎪ e − j N pn ( n +1) , when N is odd
⎩
- Sequence number p is relatively prime to N
- Sequence length: N
- Number of sequences: N-1


DRS
DRS is made from Z-C sequence*, and the DRS sequence length is the same
with the number of subcarriers in an assigned RBs
DRS is defined with the following parameters
Sequence group (30 options): cell specific parameter
Sequence (2 options for sequence lengths of 6PRBs or longer): cell specific
parameter
Cyclic shift (12 options): both terminal and cell specific components
Sequence length: given by the UL allocation
Typically,
Cyclic shifts are used to multiplex RSs from different UEs within a cell.
Different sequence groups are used in neighboring cells.


DRS Location within a Subframe
DM RS for PUSCH
Normal CP 적용 시 PUSCH RS는 한 슬롯 당 중앙의 SC-FDMA 심볼에 위치
Extended CP 적용 시 PUSCH RS는 한 슬롯 당 3번째 SC-FDMA 심볼에 위치

DM RS for PUCCH
Format 1x

Format 2x


SRS
기지국이 각 단말의 상향링크 채널 정보를 추정할 수 있도록 단말이 전송하는 RS
Reference for channel quality information
CQ measurement for frequency/time aware scheduling
CQ measurement for link adaptation
CQ measurement for power control
CQ measurement for MIMO
Timing measurement
Reference signal sequence is defined by a cyclic shift of a base sequence (ZC)
r SRS (n ) = ru(,α ) (n )
v ru(,α ) (n) = e jαn ru ,v (n), 0 ≤ n < M sc
v
RS

SRS 전송주기/대역폭은 각 단말마다 고유하게 할당
From as often as once in every 2ms to as infrequently as once in every 160ms (320ms)
At least 4 RBs
SRS는 서브프레임의 마지막 SC-FDMA 심볼로 전송
SRS multiplexing by
Time, Frequency, Cyclic shifts, and transmission comb (2 combs distributed SC-FDMA)
To avoid the collision b/w SRS and PUSCH transmission from other UEs, SRS
transmissions should not extend into the frequency band reserved for PUCCH.


SRS – cont’d
Non-frequency-hopping (wideband) SRS and frequency-hopping SRS

Multiplexing of SRS transmissions from different UEs


Uplink L1/L2 Control Signaling
Uplink L1/L2 control signaling consists of:
HARQ acknowledgements for received DL-SCH transport blocks
UE reports downlink channel conditions including CQI, PMI, and RI
Scheduling requests
Two different methods for transmission of UL L1/L2 control signaling
No simultaneous transmission of UL-SCH
UE doesn’t have a valid scheduling grant, that is, no resources have been assigned for UL-SCH
in the current subframe
PUCCH is used for transmission of UL L1/L2 control signaling
Simultaneous transmission of UL-SCH
UE has a valid scheduling grant, that is, resources have been assigned for UL-SCH in the
current subframe
UL L1/L2 control signaling is time multiplexed with the coded UL-SCH onto PUSCH prior to SC-
FDMA modulation
Only HARQ acknowledgement and channel-status reports are transmitted
No need to request a SR. Instead, in-band buffer status reports are sent in MAC headers
The basis for channel-status reports on PUSCH is aperiodic reports
If a periodic report is configured to be transmitted on PUCCH in a frame when US is scheduled
to transmit PUSCH, then the periodic report is rerouted to PUSCH resources


Periodic/Aperiodic Channel Info Feedback
Periodic reporting Aperiodic reporting
When to send Periodically every 2-160 ms When requested by eNB

Normally on PUCCH, PUSCH used
Where to send Always on PUSCH
when multiplexed with data

Payload size of the reports 4-11 bits Up to 64 bits

Channel coding Linear block codes RM coding or tail-biting CC

CRC protection No Yes, 8 bit CRC

Sent in separate subframes at lower Sent separately encoded in the
RI
periodicity same subframe

Only very limited amount of Detailed frequency selective reports
Freq. selectivity of CQI
frequency info are possible

Frequency selective PMI reports are
Freq. selectivity of PMI Only wideband PMI
possible


UL L1/L2 control signaling on PUCCH
The reasons for locating PUCCH resources at the edges of the spectrum
To maximize frequency diversity
To retain single-carrier property
Multiple UEs can share the same PUCCH resource block
Format 1: length-12 orthogonal phase rotation sequence + length-4 orthogonal cover
Format 2: length-12 orthogonal phase rotation sequence
PUCCH is never transmitted simultaneously with PUSCH from the same UE
2 consecutive PUCCH slots in Time-Frequency Hopping at the slot boundary


Changing UL System BW Via PUCCH Config


PUCCH Formats
Multiplexing
PUCCH Modulation Number of bits
Usage capacity
format scheme per subframe
(UE/RB)
1 N/A N/A SR 36, 18*, 12
1a BPSK 1 ACK/NACK 36, 18*, 12
1b QPSK 2 ACK/NACK 36, 18*, 12
2 QPSK 20 CQI 12, 6*, 4
2a QPSK+BPSK 21 CQI + ACK/NACK 12, 6*, 4
2b QPSK+QPSK 22 CQI + ACK/NACK 12, 6*, 4

* Typical value with 6 different rotations (choosing every second cyclic shift)

PUCCH Format 2/2a/2b is located at the outermost RBs of system BW
ACK/NACK for persistently scheduled PDSCH and SRI are located next
ACK/NACK for dynamically scheduled PDSCH are located innermost RBs


PUCCH Resource Mapping
Format 1

4 symbols are modulated by BPSK/QPSK
BPSK/QPSK symbol is multiplied by a length-4 orthogonal cover sequence (a length-3
orthogonal cover when there is SRS), and then it modulates the rotated length-12
sequence.
Reference signals also employ one orthogonal cover sequence
PUCCH capacity: up to 3 x 12 = 36 different UEs per each cell-specific sequence
(assuming all 12 rotations being available Practically, only 6 rotations.)
Format 2

5 symbols are modulated by QPSK after being multiplied by a phase rotated length-12
cell specific sequence.
Resource consumption of one channel-status report is 3x of HARQ acknowledgement


More on PUCCH Multiplexing
CDM and FDM
Two ways for CDM
CDM by means of cyclic shifts of a CAZAC sequence
CDM by means of block-wise spreading with the orthogonal cover sequences
Two main issues with CDM
Channel delay spread limits the orthogonality between cyclically shifted
CAZAC sequences
Channel Doppler spread limits the orthogonality between block-wise spread
sequences


PUCCH Format1 Processing


PUCCH Format2 Processing


UL L1/L2 control signaling on PUSCH


More on Control Signalling on PUSCH
CQI/PMI transmitted on PUSCH uses the same modulation scheme as data.
ACK/NACK and RI are transmitted so that the coding/scrambling/ modulation
maximize the Euclidean distance at the symbol level.
The outermost constellation points are used to signal these for 16QAM and
64QAM.
Different channel coding
1-bit ACK/NACK: repetition coding
2-bit ACK/NACK/RI: simplex coding
CQI/PMI < 11bits: (32,N) Reed-Muller coding
CQI/PMI > 11bits: tail-biting CC (1/3)
How to keep the performance of control signaling on PUSCH?
Different power offset? No! Because SC properties are partially destroyed.
Variable coding rate? Yes! The size of physical resources for control is scaled.


PUSCH Processing (1)


UL SC-FDMA Signal Generation
This section applies to all uplink physical signals and physical channels
except the physical random access channel
SC-FDMA parameters
0 ≤ t < (N CP ,l + N )× Ts where N = 2048

Check with numbers in Table 5.2.3-1.
{(160+2048) x Ts} + 6 x {(144+2048) x Ts} = 0.5 ms
6 x {(512+2048) x Ts} = 0.5 ms


PUSCH Frequency Hopping
PUSCH transmission
Localized transmission w/o frequency hopping
Frequency Selective Scheduling Gain
Localized transmission with “frequency hopping”
Frequency Diversity Gain, Inter-cell Interference Randomization
Two types of PUSCH frequency hopping
Subband-based hopping according to cell-specific hopping patterns
Hopping based on explicit hopping information in the scheduling grant


Hopping based on cell-specific patterns
Subbands are defined
In 10 MHz BW case, the overall UL BW corresponds to 50 RBs and there are a total of 4 subbands, each consisting
of 11 RBs. The remaining 6 RBs are used for PUCCH transmission.

The resource defined by a scheduling grant (VRBs) is not the actual set of RBs for transmission.
The resource to use for transmission (PRBs) is the resource provided in the scheduling grant “shifted” a
number of subbands according to a cell-specific hopping pattern.


More on hopping w/ cell-specific patterns
Example for predefined hopping for PUSCH with 20 RBs and M=4
(subband hopping + mirroring)


Hopping based on explicit information
Explicit hopping information provided in the scheduling grant is about the “offset” of the
resource in the second slot, relative to the resource in the first slot
Selection b/w hopping based on cell-specific hopping patterns or hopping based on explicit
information can be done dynamically.
Cell BW less than 50 RBs
1 bit in scheduling grant indicating to specify which scheme is to be used
When hopping based on explicit information is selected, the offset is always half of BW
Cell BS equal or larger than 50 RBs
2 bits in scheduling grant
One of the combinations indicate that hopping should be based on cell-specific hopping patterns
Three remaining combinations indicate hopping of 1/2, +1/4, and -1/4 of BW


PRACH
PRACH는 RA 과정에서 단말이 기지국으로 전송하는 preamble이다
6RB를 차지하며 부반송파 간격은 1.25kHz (format #4는 7.5kHz)
64 preamble sequences for each cell 64 random access opportunities per PRACH resource
Sequence부분은 길이 839의 Z-C sequence로 구성 (format #4는 길이 139)
Phase modulation: Due to the ideal auto-correlation property, there is no intra-cell interference from multiple
random access attempt using preambles derived from the same Z-C root sequence.
Five types of preamble formats to accommodate a wide range of scenarios
Higher layers control the preamble format

넓은 반경의 셀 환경과 같이 시간 지연이 긴 경우
SINR이 낮은 상황을 고려하여 sequence repetition
SINR이 낮은 상황을 고려하여 sequence repetition
TDD 모드용


Different Preamble Formats


PRACH Location


UL 16QAM SC-FDMA


Synchronization Signals
504 unique physical-layer cell identities
168 unique physical-layer cell-identity groups (0~167)
3 physical-layer identity within physical-layer cell-identity group (0~2)
SS is using single antenna port
However, SS can be with UE-transparent transmit antenna scheme (e.g.
PVS, TSTD, CDD)
Primary SS (PSS) and Secondary SS (SSS)


Primary Synchronization Signal
The sequence used for the primary synchronization signal is generated from a frequency-
domain Zadoff-Chu sequence (Length-62)
⎧ − j πun ( n +1)
⎪ e 63 n = 0,1,...,30
d u (n) = ⎨ πu ( n +1)( n + 2)
⎪e − j 63 n = 31,32,...,61
⎩
For frame structure type 1, PSS is mapped to the last OFDM symbol in slots 0 and 10
No need to know CP length
The sequence is mapped to REs (6 RBs) according to
DL RB
ak ,l = d (n ),
N RB N sc
k = n − 31 + , l = N symb − 1,
DL
n = 0,...,61
2

Cell ID detection within a cell ID group (3 hypotheses)
Half-frame timing detection (Repeat the same sequence twice)


Secondary Synchronization Signal
The sequence used for the second synchronization signal is an interleaved concatenation
of two length-31 binary sequences (X and Y)
The concatenated sequence is scrambled with a scrambling sequence given by PSS
The combination of two length-31 sequences defining SSS differs between slot 0 (SSS1)
and slot 10 (SSS2) according to
⎧s0m0 ) (n)c0 (n ) in subframe 0
⎪
(
d ( 2 n) = ⎨ ( m )
⎪s1 1 (n)c0 (n ) in subframe 5
⎩
⎧s1 m1 ) (n)c1 (n )z1 m0 ) (n ) in subframe 0
⎪
( (
d (2n + 1) = ⎨ ( m )
⎪s0 0 (n)c1 (n )z1 1 (n ) in subframe 5
(m )
⎩

where 0 ≤ n ≤ 30
Blind detection of CP-length (2 FFT operations are needed)
The same antenna port as for the primary sync signal
Mapped to 6 RBs


Structure of SSS


Synchronization Signals – cont’d
Cell ID group detection (the set of valid combination of X and Y for SSS are 168)
Frame boundary detection (the m-sequences X and Y are swapped b/w SSS1 and SSS2)


LTE Cell Search
Primary SS
Symbol timing acquisition
Frequency synchronization
Cell ID detection within a cell group ID (3
hypotheses)
Half-frame boundary detection

Secondary SS
Cell group ID detection (168 hypotheses)
Frame boundary detection (2 hypotheses)
CP-length detection (2 hypotheses)

Check Cell ID with cell-specific RS

BCH
40ms BCH period timing detection
eNB # of tx antenna detection
MIB acquisition
(Operation BW, SFN, etc…)

PDCCH reception

SIB acquisition within PDSCH

(cf) WCDMA Cell Search Procedure
Terminal power on

Detect strongest PSCH

Get slot synch from P-SCH

Get PICH code group info from S-SCH
8 PN codes per group.
64 code groups have
512 PN codes in total. Get PN code info by evaluating
all 8 PN codes in code group

Get system info from PCCPCH

Wait while monitoring SCCPCH


LTE Cell Search – cont’d*

PSS/SSS, BCH

3

1.4


LTE Frame & Slot Structure

LTE/MIMO 표준기술 * 윤상보 (삼성), “3GPP LTE & LTE-Advanced System”, 제5차 차세대이동통신 단기강좌, Aug. 2008
138

DL Frame Structure Type 1*


UL Frame Structure Type 1*

1 RB


E-UTRA UE Capabilities*

* 3GPP TS 36.306, E-UTRA; UE Radio Access Capabilities,
LTE/MIMO 표준기술 Release 8, V8.4.0, June 2009 141

LTE with Voice?
Long-term
Maybe through IMS
Near-term
CS Fallback
NTT DoCoMo pushed the industry to include CS Fallback as part of the 3GPP standard.
With CS Fallback the operator accepts the notion that its brand new LTE network won’t support voice and
SMS services. Instead, a control signal is sent to the LTE device indicating an incoming voice call/SMS
message at which point the device falls back to the legacy 2G/3G network to receive the call/message.
Largely comparable to 1xEV-DO/1X
Won’t work for 3GPP2 operators (e.g. Verizon, KDDI, and LGT)
VoLGA
Leverage the operator’s existing circuit switched CN to carry voice calls and SMS messages over the LTE air
interface.
In many respects VoLGA is comparable to GAN/UMA, which is how operators like Orange UK and T-Mobile
USA leverage Wi-Fi access points to offload voice traffic from their macro cellular networks.
In other words VoLGA = GAN/UMA – Wi-Fi.
Has been ruled out as from Release 8 or Release 9 of 3GPP
The driver for LTE is the rapid acceleration of mobile data traffic, thus it would be counter
productive to use LTE for voice services.
What about SR-VCC (Single Radio Voice Call Continuity) to GSM/WCDMA/CDMA?
What about coverage?


CS Fallback
Mobile terminated call

Mobile originated call


Evolution Beyond Release 8
LTE MBMS
SON enhancements
Further improvements for enhanced VoIP support in LTE
The requirements for the multi-bandwidth and multi-radio access
technology base station
Enhanced mobility support for LTE
Enhanced positioning support for LTE
Dual layer beam forming for Rel.9
Enhanced DL transmission for LTE
Home-(e)NB

And… LTE-Advanced with Release 10


LTE and WiMAX
What is 4G (through LTE and WiMAX)?
New Technology: OFDM + MIMO
New Biz Model: Mobile Broadband

LTE is justifying WiMAX and WiMAX is justifying LTE
They are using the same fundamental technologies
They are targeting the same market

Convergence??
In technical area: 3GPP LTE-Adv & IEEE 802.16m are getting more
and more similar
In biz area: Ecosystem??


Final Message* * Signals Ahead


References
[1] 3GPP homepage: www.3gpp.org
[2] Hannes Ekström, Anders Furuskär, Jonas Karlsson, Michael Meyer, Stefan Parkvall, Johan Torsner, and Mattias
Wahlqvist (Ericsson), “Technical Solutions for the 3G Long-Term Evolution”, IEEE Communications Magazine,
March 2006
[3] Erik Dahlman, Hannes Ekstrom, Anders Furuskar, Ylva Jading, Jonas Karlsson, Magnus Lundevall, and Stefan
Parkvall (Ericsson), “The 3G Long-Term Evolution - Radio Interface Concepts and Performance Evaluation”, IEEE
VTC 2006
[4] Leonard J. Cimini Jr. and Ye (Geoffrey) Li, “Orthogonal frequency division multiplexing for wireless channels”,
AT&T Labs – Research
[5] Richard van Nee and Ramjee Prasad, OFDM for Wireless Multimedia Communications, Artech House Publishers
[6] D. Falconer, et al., “Frequency domain equialization for single-carrier broadband wireless systems,” IEEE
Communication Magazine, vol.40, no.4, April 2002
[7] Hyung G. Myung, Junsung Lim, and David J. Goodman, “Single Carrier FDMA for Uplink Wireless Transmission”,
IEEE Vehicular Technology Magazine, Sep. 2006
[8] 오민석 (LGE), “3GPP LTE”, KRnet 2007, June 29 2007
[9] 김학성 (LGE), “3GPP LTE PHY Layer Specification and Technology”, 제4차 차세대이동통신 단기강좌, Feb. 2008
[10] Moray Rumney (Agilent), “Concepts of 3GPP LTE”, Live Webinar, Sep. 2007
[11] 이상근, 조봉열, 여운영, 쉽게 설명한 3G/4G 이동통신 시스템 (2nd edition), 홍릉과학출판사, 2009
[12] Erik Dahlman, et al, 3G Evolution: HSPA and LTE for Mobile Broadband (2nd edition), Academic Press, 2008
[13] Harri Holma and Antti Toskala, LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Wiley, 2009
[14] Stefania Sesia, Issam Toufik, and Matthew Baker, LTE, The UMTS Long Term Evolution: From Theory to
Practice, Wiley, 2009
[15] David Astély, et al, “LTE: The Evolution of Mobile Broadband,” IEEE Commun. Mag. April 2009
[16] Anna Larmo, et al, “The LTE Link-Layer Design,” IEEE Commun. Mag. April 2009
[17] LSTI, “Latest Results from the LSTI,” Feb. 2009;
http://www.lstiforum.com/file/news/Latest_LSTI_Results_Feb09_v1.pdf


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