LTE by Bruno Melis
Transcript of LTE by Bruno Melis
-
7/30/2019 LTE by Bruno Melis
1/69
-
7/30/2019 LTE by Bruno Melis
2/69
Telecom Italia Proprietary
Outline LTE Study Item
Rationale & Objectives
Requirements
LTE Key enabling Technologies
OFDM
MIMO
All IP Flat Architecture
LTE peak rates and UE categories
LTE radio interface and procedures
LTE Advanced overview
Requirements with respect to Release 8
Additional features
-
7/30/2019 LTE by Bruno Melis
3/69
Telecom Italia Proprietary
LTE Study Item (2004): Rationale & objectivesFROM 3GPP TR 25.913:
to ensure competitiveness in an even longer time frame, i.e. for the next 10 years and
beyond, a long-term evolution of the 3GPP radio-access technology needs to be considered.
Important parts of such a long-term evolution include reduced latency, higher user data
rates, improved system capacity and coverage, and reduced cost for the operator. In order to
achieve this, an evolution of the radio interface as well as the radio network architecture should
be considered.
.Considering a desire for even higher data rates and also taking into account future
additional 3G spectrum allocations the long-term 3GPP evolution should include an evolution
towards support for wider transmission bandwidth than 5 MHz. At the same time, support for
transmission bandwidths of 5 MHz and less than 5 MHz should be investigated in order to allow
for more flexibility in whichever frequency bands the system may be deployed.
-
7/30/2019 LTE by Bruno Melis
4/69
Telecom Italia Proprietary
FROM 3GPP TR 25.913
The objective of Evolved UTRA and UTRAN is to develop a framework for the
evolution of the 3GPP radio-access technology towards a high-data-rate, low-
latency and packet-optimized radio-access technology. Thus the study should focus
on supporting services provided from the PS-domain. In order to achieve this,
studies should be carried out in at least the following areas:
Related to the radio-interface physical layer (downlink and uplink): e.g. means to support flexible transmission bandwidth up to 20 MHz, introduction
of new transmission schemes and advanced multi-antenna technologies
Related to the radio interface layer 2 and 3: e.g. signalling optimization
Related to the UTRAN architecture: identify the most optimum UTRAN network architecture and functional split
between RAN network nodes, not precluding considerations on the functional
split between UTRAN and CN
LTE Study Item (2004): Rationale & objectives
-
7/30/2019 LTE by Bruno Melis
5/69
Telecom Italia Proprietary
FROM 3GPP TR 25.913 The targets for the evolution of the radio-interface and radio-access network
architecture should be: Significantly increased peak data rate e.g. 100 Mbps (downlink) and 50 Mbps (uplink)
Increase "cell edge bitrate" whilst maintaining same site locations as deployed today
Significantly improved spectrum efficiency ( e.g. 2-4 times over UMTS/HSPA Release 6)
Possibility for a Radio-access network latency (user-plane UE RNC (or corresponding
node above Node B - UE) below 10 ms
Significantly reduced C-plane latency (e.g. including the possibility to exchange user-
plane data starting from camped-state with a transition time of less than 100 ms
(excluding downlink paging delay)
Scalable bandwidth
5, 10, 20 and possibly 15 MHz
allow flexibility in narrow spectral allocations where the system may be
deployed
LTE Study Item (2004): Rationale & objectives
-
7/30/2019 LTE by Bruno Melis
6/69
Telecom Italia Proprietary
FROM 3GPP TR 25.913
The targets for the evolution of the radio-interface and radio-access networkarchitecture should be: Support for inter-working with existing 3G systems and non-3GPP specified systems
Reduced CAPEX and OPEX including backhaul
Cost effective migration from Release 6 UTRA radio interface and architecture
Reasonable system and terminal complexity, cost, and power consumption.
Support of further enhanced IMS and core network
Backwards compatibility is highly desirable, but the trade off versus performance and/orcapability enhancements should be carefully considered.
Efficient support of the various types of services, especially from the PS domain (e.g.Voice over IP, Video streaming, Gaming, etc.)
System should be optimized for low mobile speed but also support high mobile speed
Operation in paired and unpaired spectrum should not be precluded
Possibility for simplified co-existence between operators in adjacent bands as well ascross-border co-existence
LTE Study Item (2004): Rationale & objectives
-
7/30/2019 LTE by Bruno Melis
7/69
Telecom Italia Proprietary
Requirements of LTE (1/3)
100 Mbit/s DL and 50 Mbit/s UL within a 20 MHz bandwidth
Peak data rate
Downlink: in a loaded network, target for spectrum efficiency (bits/sec/Hz/site)is 3 to 4 times Release 6 HSDPA.
Uplink: in a loaded network, target is 2 to 3 times Release 6 HSUPA
Spectral Efficiency
Optimized for low mobile speed from 0 to 15 km/h
Higher speeds between 15 and 120 km/h supported with high performance
Mobility shall be maintained at speeds from 120 km/h to 350 km/h (or even upto 500 km/h depending on the frequency band)
Mobility
* Details in 3GPP TR 25.913
-
7/30/2019 LTE by Bruno Melis
8/69
Telecom Italia Proprietary
Requirements of LTE (2/3)
Performance should be met for 5 km cells, with slight degradation for 30 kmcells. Cells range up to 100 km should not be precluded
Coverage
At least 200 users per cell supported in the active state for spectrum allocationsup to 5 MHz
Control plane capacity
User plane : less than 5 ms in unload condition (i.e. single user with single datastream) for small IP packet
Control plane : transition time of less than 100 ms from a camped state to anactive state
Latency
-
7/30/2019 LTE by Bruno Melis
9/69
Telecom Italia Proprietary
Requirements of LTE (3/3)
Support for spectrum allocations of different sizes (1.4 MHz - 20 MHz). Operation in paired (FDD) and unpaired (TDD) spectrum shall be supported
Spectrum flexibility
Provision of simultaneous dedicated voice and MBMS services to the user
MBMS (Multimedia Broadcast Multicast Service)
The E-UTRAN architecture shall be packet based, but should support real-timeand conversational class traffic
Enhanced support for end-to-end QoS
Architecture
-
7/30/2019 LTE by Bruno Melis
10/69
Telecom Italia Proprietary
to summarise the main ones:
RANUE
Coverage:
5 km: full performance
30 km: some degradations
100 km: not prevented
DL
Peak data rate: 100Mbps
UL
Peak data rate: 50Mbps
UL
DL
Mobility:
0-15 km/h: optimized
15-120 km/h: high performance
120-500 km/h: supported
Scalable BW:
1.4 3 5 10 15 - 20 MHz
User Plane Latency: 5ms
Control Plane Latency:
50-100 ms
http://www.google.it/imgres?imgurl=http://www.silviaraggi.it/wp-content/uploads/2009/05/telefonino.gif&imgrefurl=http://www.silviaraggi.it/2009/05/20/arriva-in-giappone-il-primo-cellulare-ibrido/&usg=__QqDds89gQF18FwMIKT3WugFu4O8=&h=180&w=166&sz=9&hl=it&start=18&zoom=1&tbnid=ucw8UExb-swyCM:&tbnh=101&tbnw=93&ei=5uTwTcOPMsPHswbAluGHBw&prev=/search%3Fq%3Dtelefonino%26hl%3Dit%26gbv%3D2%26tbm%3Disch&itbs=1http://www.google.it/imgres?imgurl=http://www.silviaraggi.it/wp-content/uploads/2009/05/telefonino.gif&imgrefurl=http://www.silviaraggi.it/2009/05/20/arriva-in-giappone-il-primo-cellulare-ibrido/&usg=__QqDds89gQF18FwMIKT3WugFu4O8=&h=180&w=166&sz=9&hl=it&start=18&zoom=1&tbnid=ucw8UExb-swyCM:&tbnh=101&tbnw=93&ei=5uTwTcOPMsPHswbAluGHBw&prev=/search%3Fq%3Dtelefonino%26hl%3Dit%26gbv%3D2%26tbm%3Disch&itbs=1 -
7/30/2019 LTE by Bruno Melis
11/69
Telecom Italia Proprietary
Key enabling technologies for Long Term Evolution
x1
x2
x3
y1
y2
y3
MIMO Network Evolution
eNBeNB
eNB
MME/UPE MME/UPE
S1
X2
X2
X2
Evolved
Packet
Core
E-UTRAN
OFDMScalable Bandwidth
RECIPES
-
7/30/2019 LTE by Bruno Melis
12/69
Telecom Italia Proprietary
Orthogonal Frequency Division Multiplexing (OFDM) is a particular form of multi-
carrier modulation (MCM).
MCM is a parallel transmission method which divides a high bandwidth signal intoseveral narrower bandwidth subcarriers and transmits data simultaneously on each
subcarrier.
Orthogonal Frequency Division Multiplexing
-
7/30/2019 LTE by Bruno Melis
13/69
Telecom Italia Proprietary
It is possible to demonstrate that the signal sent on the channel is the reverse FFT
(or IFFT, Inverse Fast Fourier Transform) of the source signal. A reverse FFT is then
carried out within the transmitter from the N input parallel flows. High spectral efficiency is guaranteed being the sub-carrier orthogonal to each
other.
Orthogonal Frequency Division Multiplexing
OFDM is well suited for high data rate systems
which operate in multi-path environmentsbecause of its robustness to delay spread.
0
1
2
1
2
0
1
2
0
1
2
1
2
0
1
2
1
2
0
1
2
0
1
2
-
7/30/2019 LTE by Bruno Melis
14/69
Telecom Italia Proprietary
OFDM: Orthogonal Frequency Division ModulationOFDM as modulation
Spectrum is divided in several orthogonal sub-carriers : f=1/Ts
Information flow is divided over the sub-carriers
Mo-demodulation by FFT/iFFT
OFDM as mulitple access (OFDMA)
A group of sub-carriers can be allocated to different users inside the available
bandwidth
ffsingle-carrier mod.
fconventional multi-
carrier modulation
OFDM
-
7/30/2019 LTE by Bruno Melis
15/69
Telecom Italia Proprietary
OFDM: Characteristics
Sub-carriers
FFT
Time
Symbols
N subcarriers in W
Bandwidth
Guard Intervals
Frequency
f=1/Ts
-
7/30/2019 LTE by Bruno Melis
16/69
Telecom Italia Proprietary
High resistance to multipath propagation
Low implementation complexity (IFFT/FFT)
Sharp power spectrum decrease at the band edges
Inter-Symbol Interference (ISI) is eliminated at the receiver by removing the cyclic prefix
(i.e. no need for channel equalizers or Rake receivers)
Space-time processing operations performed independently for each sub-carrier (lower
receiver complexity that single carrier transmission)
High Peak to Average Power Ratio (PAPR)
Power amplifiers with high linearity are required (critical issue on the terminal side)
Sensitivity to frequency offset and phase noise
Advantages
Disadvantages
Orthogonal Frequency Division Multiplexing (OFDM)
frequency
sub-carriers
f
Power spectrum)( fX
-
7/30/2019 LTE by Bruno Melis
17/69
Telecom Italia Proprietary
In 3GPP Long Term Evolution:
Orthogonal Frequency Division Multiple Access (OFDMA) is used in downlink direction
Single Carrier Frequency Division Multiple Access (SC-FDMA) is used in the uplinkdirection
OFDM in 3GPP Long Term Evolution
Downlink Multiple access is achieved in OFDMA by assigning subsets of subcarriers to
individual users. The subcarrier spacing in the OFDM downlink is 15 kHz and there is
a maximum of 2048 subcarriers available. The transmission is divided in time into
time slots of duration 0.5 ms and subframes of duration 1.0 ms. A radio frame is 10
ms long. Supported modulation formats on the downlink data channels are QPSK,
16-QAM and 64-QAM.
Uplink SC-FDMA was chosen in order to reduce Peak to Average Ratio (PAR), which has been
identified as a critical issue for use of OFDMA in the uplink where power efficient
user-terminal amplifiers are required. Another important requirement was to
maximize the coverage. For each time interval, the base station scheduler assigns aunique time-frequency interval to a terminal for the transmission of user data,
thereby ensuring intra-cell orthogonality.
-
7/30/2019 LTE by Bruno Melis
18/69
Telecom Italia Proprietary
Multi-Antenna techniques
x1
x2
x3
y1
y2
y3
Multiple input multiple output (MIMO) antenna techniques are required to achieve the
higher LTE bit-rate targets.
MIMO is simpler to implement with OFDMA than with CDMA, and it is more effective,
since OFDMA is more robust to multipath and MIMO can exploit rich scattering
environment without being negatively affected by multipath.
For this reason, MIMO schemes up to 4x4 are defined in the LTE Release 8 standard.
MIMO can be used to provide both spatial multiplexing and space-time coding.
Spatial Multiplexing Space Time Coding
-
7/30/2019 LTE by Bruno Melis
19/69
Telecom Italia Proprietary
E-UTRAN architecture
The E-UTRAN consists of eNBs, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and
control plane (RRC) protocol terminations towards the UE.
The eNBs are interconnected with each other by means of the X2 interface. The eNBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core),
more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to
the Serving Gateway (S-GW) by means of the S1-U.
internet
eNB
RB Control
Connection Mobility Cont.
eNB MeasurementConfiguration & Provision
Dynamic ResourceAllocation (Scheduler)
PDCP
PHY
MME
Serving Gateway
S1
MAC
Inter Cell RRM
Radio Admission Control
RLC
E-UTRAN EPC
RRC
Mobility Anchoring
SAE Bearer Control
Idle State MobilityHandling
NAS Security
Logical Nodes
Radio Protocol Layers
Functional Entities of Control Plane
-
7/30/2019 LTE by Bruno Melis
20/69
Telecom Italia Proprietary
eNB functionalities
The eNB hosts the following functions:
Functions for RRM: Radio Bearer Control, Radio Admission Control, ConnectionMobility Control, Dynamic allocation of resources to UEs in both uplink and
downlink (scheduling)
IP header compression and encryption of user data stream
Selection of an MME at UE attachment
Routing of User Plane data towards S-GW Scheduling and transmission of paging messages (originated from the MME)
Scheduling and transmission of broadcast information (originated from the MME orO&M)
Measurement and measurement reporting configuration for mobility and scheduling
-
7/30/2019 LTE by Bruno Melis
21/69
Telecom Italia Proprietary
MME and S-GW functionalities
The MME hosts the following functions:
Distribution of paging messages to the eNBs Security control
Idle state mobility control
SAE bearer control
Ciphering and integrity protection of NAS signalling
The Serving Gateway hosts the following functions:
Termination of U-plane packets for paging reasons
Switching of U-plane for support of UE mobility
NAS = Non-Access Stratum
SAE = System Architecture Evolution
-
7/30/2019 LTE by Bruno Melis
22/69
Telecom Italia Proprietary
Radio protocol architecture
User plane: the protocol stack comprises PDCP, RLC, MAC
and PHY sublayers (terminated in eNB on the network side)The PDCP, RLC and MAC perform the functions of header
compression, ciphering, ARQ, scheduling and HARQ.
Control plane: the protocol stack comprises NAS,
(terminated in MME), RRC, PDCP, RLC, MAC and PHY
sublayers (terminated in eNB).
eNB
PHY
UE
PHY
MAC
RLC
MAC
PDCPPDCP
RLC
eNB
PHY
UE
PHY
MAC
RLC
MAC
MME
RLC
NAS NAS
RRC RRC
PDCP PDCP
* Details in 3GPP TS 36.300
-
7/30/2019 LTE by Bruno Melis
23/69
Telecom Italia Proprietary
Layer 3 radio protocol
Layer 3 is composed by the RRC (Radio Resource Control) that is terminated in the eNB on
the network side
Broadcast of System Information related to the non-access stratum (NAS) and tothe the access stratum (AS)
Paging Establishment, maintenance and release of an RRC connections
Security functions including key management Establishment, configuration, maintenance and release of point to point Radio
Bearers (RB)
Mobility functions including: Inter-cell handover, UE cell selection and reselection QoS management functions
UE measurement reporting and control of the reporting
The main layer 3 functions are:
-
7/30/2019 LTE by Bruno Melis
24/69
Telecom Italia Proprietary
Layer 2 radio protocol
Layer 2 is split into Medium Access Control (MAC), Radio Link Control (RLC) and Packet Data
Convergence Protocol (PDCP).
The multiplexing of several logical channels (i.e. radio bearers) on the same transportchannel (i.e. transport block) is performed by the MAC sublayer.
In uplink and downlink, only one transport block is generated per TTI in the non-MIMO case.
Layer 2 Structure for DL(user plane)
Segm.
ARQ
Multiplexing UE1
Segm.
ARQ...
HARQ
Multiplexing UEn
HARQ
BCCH PCCH
Scheduling / Priority Handling
Logical Channels
Transport Channels
MAC
RLCSegm.
ARQ
Segm.
ARQ
PDCP
ROHC ROHC ROHC ROHC
Radio Bearers
Security Security Security Security
...
ROHC = robust header compression
Ciphering
-
7/30/2019 LTE by Bruno Melis
25/69
-
7/30/2019 LTE by Bruno Melis
26/69
Telecom Italia Proprietary
LTE numerology
An Orthogonal Frequency Division Multiple Access (OFDMA) scheme is employed for
downlink (DL) transmission.
Scalable-OFDM (S-OFDM) technology is employed: the sub-carrier spacing f is fixed andequal to 15 KHz, independently from the transmission bandwidth so that the number
NFFT of subcarriers is proportional to the transmission bandwidth (BW).
The clock frequency can be derived from the W-CDMA chip-rate (3.84 MHz)
Channel Bandwidth (BW) 1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz
Subframe duration 1.0 ms
Sub-carrier spacing (f) 15 kHz
Sampling frequency1.92 MHz
(1/2 3.84 MHz)3.84 MHz
7.68 MHz
(2 3.84 MHz)
15.36 MHz
(4 3.84 MHz)
23.04 MHz
(6 3.84 MHz)
30.72 MHz
(8 3.84 MHz)
FFT size (NFFT) 128 256 512 1024 1536 2048
Number of used
sub-carriers72 180 300 600 900 1200
Number of
OFDM symbols
per sub frame
(Normal/Extended CP)
7/6
CP length
(s/samples)
Normal(4.69/9) 6,
(5.21/10) 1*
(4.69/18) 6,
(5.21/20) 1
(4.69/36) 6,
(5.21/40) 1
(4.69/72) 6,
(5.21/80) 1
(4.69/108) 6,
(5.21/120) 1
(4.69/144) 6,
(5.21/160) 1
Extended (16.67/32) (16.67/64) (16.67/128) (16.67/256) (16.67/384) (16.67/512)
LTE peak data rates (theoretical calculation)
-
7/30/2019 LTE by Bruno Melis
27/69
Telecom Italia Proprietary
LTE peak data rates (theoretical calculation)
Downlink (20 MHz, code rate 0.95, 64-QAM) 150 Mbit/s with 22 MIMO 300 Mbit/s with 44 MIMO
Uplink (20 MHz, code rate 0.95, Single transmit antenna) 50 Mbit/s with 16-QAM 75 Mbit/s with 64-QAM
BUT with 2x2 MIMO in the 5 MHz bandwidth the DL
peak throughput would be similar to HSPA+
LTE bandwidth [MHz] 1.4 3 5 10 15 20
Number of PRB 6 15 25 50 75 100
Number of OFDM symbols for PDCCH 2 2 2 2 2 2
Number of data subcarriers per TTI 132 132 132 132 132 132
Modulation 6 6 6 6 6 6
Number of TX antennas 2 2 2 2 2 2
Maximum Code Rate 0.95 0.95 0.95 0.95 0.95 0.95
DL Peak Throughut [Mbit/s] 9.0 22.6 37.6 75.2 112.9 150.5
LTE bandwidth [MHz] 1.4 3 5 10 15 20
Number of PRB 6 15 25 50 75 100
Number of PRBs used for UL control CH 2 2 4 6 8 8
Number of OFDM symbols for RS 2 2 2 2 2 2
Number of data subcarriers per TTI 144 144 144 144 144 144
Modulation 6 6 6 6 6 6
Number of TX antennas 1 1 1 1 1 1
Maximum Code Rate 0.95 0.95 0.95 0.95 0.95 0.95
UL Peak Throughut [Mbit/s] 3.3 10.7 17.2 36.1 55.0 75.5
-
7/30/2019 LTE by Bruno Melis
28/69
Telecom Italia Proprietary
UE categories
* Details in 3GPP TS 36.306
Downlink capabilities
Uplink capabilities
16-QAM only
Support of 64-QAM
4 Rx antennas
UE Category Maximum number of
DL-SCH transportblock bits received
within a TTI
Peak Throughput
supported by theUE [Mbit/s]
Maximum number
of supportedlayers for spatial
multiplexing in DL
Category 1 10296 10.296 1
Category 2 51024 51.024 2
Category 3 102048 102.048 2
Category 4 150752 150.752 2
Category 5 299552 299.552 4
UE Category Maximum number of
bits of an UL-SCH
transport block
transmitted within a
TTI
Peak Throughput
supported by the
UE [Mbit/s]
Support for
64QAM in UL
Category 1 5160 5.16 No
Category 2 25456 25.456 NoCategory 3 51024 51.024 No
Category 4 51024 51.024 No
Category 5 75376 75.376 Yes
LTE f
-
7/30/2019 LTE by Bruno Melis
29/69
Telecom Italia Proprietary
LTE frame structures
Downlink and uplink transmission are organized into radio frames with duration Tf = 10 ms.
Two radio frames structures are supported
Type 1 frame structure Applicable to FDD and HD-FDD duplexing
Type 2 frame structure Applicable to TDD duplexing
Type 1 frame structureType 2 frame structure
The alternative frame structure has been defined to facilitate the coexistence with the 1.28
Mchip/s UTRA TDD system (i.e. the TD-SCDMA standard primarily adopted in China).
#0 #1 #18 #19#2
Sub-frame
slot
One radio frame = 10ms
0.5 msOne radio frame = 10 ms
Half-frame = 5 ms
Subframe = 1 ms
#0 #2 #3 #4
DwPTS
GP
UpPTS* Details in 3GPP TS 36.211
T 1 f t t
-
7/30/2019 LTE by Bruno Melis
30/69
Telecom Italia Proprietary
Each radio frame consists of 20 slots each of length Tslot = 0.5 ms.
A subframe is defined as two consecutive slots where subframe j consists of slots 2j and 2j+1
For FDD duplexing, downlink and uplink transmission are separated in the frequency domain
and both the downlink and uplink frame is composed by 10 subframes of 1 ms each.
Type 1 frame structure
2048
1
2048
f
TT
symb
s
sampling time = 32.6 ns
f = subcarrier spacing = 15 KHz
symbT = OFDM symbol duration = 66.6 s
sT
#0 #1 #2 #3 #19#18
One radio frame, Tf= 307200Ts = 10 ms
One slot, Tslot = 15360Ts = 0.5 ms
One subframe
* Details in 3GPP TS 36.211
Sl t t t
-
7/30/2019 LTE by Bruno Melis
31/69
Telecom Italia Proprietary
Slot structure
Slot period equal to 0.5 ms and TTI= 1ms
Two cyclic prefix lengths : normal and extended
Number of OFDM symbols per slot : 7 (normal CP) or 6 (extended CP)
Normal cyclic prefix: TCP = 160Ts (OFDM symbol #0) , TCP = 144Ts (OFDM symbol #1 to #6)
Extended cyclic prefix: TCP-e = 512Ts (OFDM symbol #0 to OFDM symbol #5)
Symb 0 Symb 1 Symb 2 Symb 3 Symb 4 Symb 5
Tslot = 0.5 ms
Tsymb = 66.7 sTCP = 16.6 s
Extended CP
Symb 6 Normal CPymb 5ymb 4ymb 3ymb 2ymb 1ymb 0
TCP = 4.69 sTCP = 5.21 s
Ph i l R bl k (PRB) (1/2)
-
7/30/2019 LTE by Bruno Melis
32/69
Telecom Italia Proprietary
Physical Resource block (PRB) (1/2)
Physical Resource Block : is the smallest unit of bandwidth assigned by the scheduler at
physical level. One PRB is composed by a set of 12 adjacent subcarriers allocated on a slot-
by-slot basis. Resource element : each subcarrier in the resource grid
Physical Resource Block (PRB)Resource Element (k,l)
RB
SCN subcarriers
RB
SC
DL
RB NN subcarriers
DL
symbN
OFDM
symbols
l=0
l = 1D L
sy m bN
k=0 k= 1RB
SC
DL
RB NN
Slot
freq
time
* Details in 3GPP TS 36.211
Physical Resource block (PRB) (2/2)
-
7/30/2019 LTE by Bruno Melis
33/69
Telecom Italia Proprietary
Channel bandwidth
BW [MHz]1.4 3 5 10 15 20
Number of active PRBs
per slot (NRB)6 15 25 50 75 100
The following symbols are introduced in the 3GPP standard (TS 36.211)
DL
RBN = downlink bandwidth configuration, expressed in number of resource blocks
RB
SCN = resource block size in the frequency domain, expressed as a number of subcarriers
The quantity depends on the downlink transmission bandwidth configured in the cellDLRBN
The quantities and depend on the frame structure and on the cyclic prefix typeRBSCN
DL
symbN
DL
symbN = number of OFDM symbols in a downlink slot
Physical Resource block (PRB) (2/2)
ConfigurationRBscN
DLsymbN
Normal cyclic prefix kHz15f 7
kHz15f 12
6Extended cyclic prefix
kHz5.7f 24 3
LTE Physical Channels (DL) (1/2)
-
7/30/2019 LTE by Bruno Melis
34/69
Telecom Italia Proprietary
LTE Physical Channels (DL) (1/2)
Physical broadcast channel (PBCH)
Mapped to four subframes within a 40 ms interval
Each subframe is self-decodable
Timing is blindly detected (i.e. no explicit signalling indicating 40 ms timing)
Physical control format indicator channel (PCFICH)
Informs the UE about the number of OFDM symbols used for the PDCCHs
Transmitted in every subframe
Physical downlink control channel (PDCCH)
Informs the UE about the resource allocation and H-ARQ information related to
DL-SCH and PCH
Carries the uplink scheduling grant.
eNB
UE
PBCH
PCFICH
PDCCH
LTE Physical Channels (DL) (2/2)
-
7/30/2019 LTE by Bruno Melis
35/69
Telecom Italia Proprietary
LTE Physical Channels (DL) (2/2)
Physical downlink shared channel (PDSCH)
Carries the DL-SCH
Physical multicast channel (PMCH)
Carries the MCH
Physical Hybrid ARQ Indicator Channel (PHICH)
Carriers ACK/NAKs in response to uplink transmissions
eNB
UE
PDSCH
PMCH
PHICH
LTE Physical Channels (UL)
-
7/30/2019 LTE by Bruno Melis
36/69
Telecom Italia Proprietary
LTE Physical Channels (UL)
Physical uplink shared channel (PUSCH)
Carries the UL-SCH
Physical uplink control channel (PUCCH)
Carries ACK/NAKs in response to downlink transmission
Carries Scheduling Request (SR)
Carries CQI reports
Physical random access channel (PRACH)
Carries the random access preamble
eNB
UE
PUSCH
PUCCH
PRACH
DL Reference Signals
-
7/30/2019 LTE by Bruno Melis
37/69
Telecom Italia Proprietary
DL Reference Signals
The Reference Signal (RS) consist of known reference symbols inserted in the first and third
last OFDM symbol of each slot (in case of normal CP)
Cell-specific reference signals are transmitted on one or several of antenna ports from 0 to 3
Cell-specific reference signals are defined for f=15 kHz only
The reference-signal sequence is defined by
There are 504 unique cell IDs
Code Division Multiplexing (CDM) is used for distinguishing RSs of sectors belonging to the
same eNB
Frequency Division Multiplexing (FDM) is used for distinguishing RSs of each antenna in case
of MIMO
* Details in 3GPP TS 36.211
12,...,1,0,)12(212
1)2(21
2
1)( DLmax,RB, s Nmmcjmcmr nl
)(s,mr nl
where nS is the slot number within a radio frame and l is the OFDM symbol number within the
slot. The pseudo-random sequence c(i) is initialised at the start of each OFDM symbol with a
function that depends on nS , l and the cell ID
DL Reference Signals (SISO)
-
7/30/2019 LTE by Bruno Melis
38/69
Telecom Italia Proprietary
DL Reference Signals (SISO)
pR reference signal transmitted on antenna port p
Time
Frequency
1 ms
180
kHz
Normal CP Extended CP
1 ms
Pilot pattern for a SISO system
DL Reference Signals (MIMO)
-
7/30/2019 LTE by Bruno Melis
39/69
Telecom Italia Proprietary
DL Reference Signals (MIMO)
Pilot pattern for a MIMO system (normal CP)
1 ms
180
kHz
Antenna port 0 Antenna port 1
MIMO 22
MIMO 44
DL Control Channels (1/2)
-
7/30/2019 LTE by Bruno Melis
40/69
Telecom Italia Proprietary
DL Control Channels (1/2)
DL control signalling is located in the first n OFDM symbols (n 3) of a subframe and
consists of:
Downlink control channels and data are transmitted on different OFDM symbols
Number n of control OFDM symbols per subframe (PCFICH)
Transport format, resource allocation, and hybrid-ARQ information (PDCCH)
Uplink scheduling grant (PDCCH)
ACK/NAK in response to uplink transmission (PHICH)
Time
Frequency
180
kHz
Control Data
DL Control Channels (2/2)
-
7/30/2019 LTE by Bruno Melis
41/69
Telecom Italia Proprietary
DL Control Channels (2/2)
Multiple physical downlink control channels are supported and a UE monitors a set of
control channels.
Control channels are formed by aggregation of control channel elements (CCE), each
control channel element consisting of a set of resource elements
QPSK modulation is used for all control channels
Control information is decodable without using the 2nd RS symbol (UE micro-sleep)
H-ARQ
-
7/30/2019 LTE by Bruno Melis
42/69
Telecom Italia Proprietary
H ARQ
UL/DL H-ARQ characteristics:
N-process Stop-And-Wait
H-ARQ transmits and retransmits Transport Blocks (TBs) H-ARQ retransmissions have lower priority than measurement gaps
UL H-ARQ principles:
Synchronous adaptive / non adaptive HARQ
Adaptive retransmissions are scheduled through PDCCH
Non-adaptive retransmissions are triggered by a NACK on PHICH only DL ACK / NACK in response to UL (re)transmissions are sent on PHICH
Maximum number of retransmissions configured per UE
DL H-ARQ principles:
Asynchronous adaptive H-ARQ
UL ACK/NAKs in response to DL (re)transmissions are sent on PUCCH or PUSCH
PDCCH signals the H-ARQ process number and if it is a transmission or retransmission
Retransmissions are always scheduled through PDCCH
Modulation
-
7/30/2019 LTE by Bruno Melis
43/69
Telecom Italia Proprietary
Modulation
For each code word q, the block of scrambled bits is modulated resulting in a block of
complex-valued modulation symbols
Modulation schemes for DL physical channels
Modulation schemes for UL physical channels
* Details in 3GPP TS 36.212
Physical
channel
Definition Modulation scheme
PDSCH Physical Downlink Shared Channel QPSK, 16-QAM, 64-QAM
PBCH Physical Broadcast Channel QPSK
PMCH Physical Multicast Channel QPSK, 16-QAM, 64-QAM
PCFICH Physical Control Format Indicator Channel QPSK
PDCCH Physical Downlink Control Channel QPSKPHICH Physical Hybrid ARQ Control Channel BPSK
Physical
channel
Definition Modulation scheme
PUSCH Physical Uplink Shared Channel QPSK, 16-QAM, 64-QAM
PUCCH Physical Uplink Control Channel BPSK, QPSK, BPSK + QPSK
PRACH Physical Random Access Channel Specific Zadoff-Chu sequences
Single Carrier FDMA
-
7/30/2019 LTE by Bruno Melis
44/69
Telecom Italia Proprietary
Single Carrier FDMA
Single carrier FDMA (SC-FDMA) accommodates multiple-user access
Also known as DFT-precoded OFDMA
Similarities with OFDMA:
Block-based modulation
Divides the transmission bandwidth into smaller subcarriers
Channel equalization done in the frequency domain
CP added to overcome ISI (Inter Symbol Interference) and to convert
linear convolution of the channel impulse response to circular one
Advantages over OFDMA:
Lower PAPR than OFDMA (efficient UE transmitter, improved cell-edge performance)
DFT
Sub-
carrierMapping
IFFT CPinsertion
(size M) (size NM)
Uplink Transmission Scheme
-
7/30/2019 LTE by Bruno Melis
45/69
Telecom Italia Proprietary
Uplink Transmission Scheme
Based on single-carrier FDMA
Uplink sub-carrier spacing f = 15 kHz. The sub-carriers are grouped into sets of 12
adjacent sub-carriers
One PRB corresponds to 12 adjacent sub-carriers during one slot period (0.5 ms). The
number of resource blocks can range from 6 (1.25 MHz) to 100 (20 MHz)
There are two cyclic-prefix lengths defined: normal cyclic prefix and extended cyclic
prefix corresponding to seven and six SC-FDMA symbols per slot respectively
Normal cyclic prefix: TCP = 160Ts (OFDM symbol #0) , TCP = 144Ts (OFDM symbol #1 to #6)
Extended cyclic prefix: TCP-e = 512Ts (OFDM symbol #0 to OFDM symbol #5)
Uplink reference signals (for channel estimation and coherent demodulation) are
transmitted in the 4-th symbol of the slot
* Details in 3GPP TS 36.211
Subcarrier mapping
-
7/30/2019 LTE by Bruno Melis
46/69
Telecom Italia Proprietary
Subcarrier mapping
Two subcarrier mapping schemes analyzed during the standardization
Distributed: inherent frequency diversity, lower PAPR in case of IFDMA
Localized: better performance with frequency domain scheduling and H-ARQ,
higher PAPR than the case of IFDMA
3GPP decided to use only the localized mapping for LTE uplink with support for inter-TTI
FH and intra-TTI FH (RAN1 #46bis - R1-063613)
Distributed Mapping Localized Mapping
Uplink Transmission Scheme
-
7/30/2019 LTE by Bruno Melis
47/69
Telecom Italia Proprietary
Based on single-carrier FDMA, UL sub-carrier spacing f = 15 kHz.
While the maximum transmission bandwidth is up to 20 MHz, the minimum transmission
bandwidth is down to 180 kHz, equal to the 12 x 15 kHz sub-carriers in the downlink
direction or, rather, one resource block.
One PRB corresponds to 12 adjacent sub-carriers during one slot period (0.5 ms). The
number of resource blocks can range from 6 (1.4 MHz) to 100 (20 MHz)
-
7/30/2019 LTE by Bruno Melis
48/69
Telecom Italia Proprietary
LTE Physical Layer procedures
Transmission Time Adjustment
-
7/30/2019 LTE by Bruno Melis
49/69
Telecom Italia Proprietary
j
Upon reception of a timing advance command, the UE shall adjust its uplink
transmission timing
The timing advance command is expressed in multiples of 16Ts ( 521 ns) and is relative
to the current uplink timing
For a timing advance command received on subframe n, then corresponding adjustment
occurs at the beginning of subframe n+x
* Details in 3GPP TS 36.213
CyclicPrefixUser A
User B
User C
TD max
Selected sampling window
for users A, B and CT
CyclicPrefix
CyclicPrefix
eNB
UE C
UE A
UE B
S1
S-GW
Random Access Channel (RACH)
-
7/30/2019 LTE by Bruno Melis
50/69
Telecom Italia Proprietary
( )
RACH is an uplink common transport channel
Two random access procedures : contention based and non-contention based (for HO)
The PRACH preamble consists of a CP of length TCP and a sequence part of length TSEQ
In the frequency domain the PRACH occupies a bandwidth corresponding to 6 PRB
RACH preambles are generated from Zadoff-Chu sequences with zero correlation zone.
The network configures the set of preamble sequences the UE is allowed to use
Normal cells
Extended format : large cells
Repeated format : very large cells (up to 30 km)
Repeated format : very large cells (up to 100 km)
sampling time = 32.6 nssT
* Details in 3GPP TS 36.213
Random Access Channel (RACH)
-
7/30/2019 LTE by Bruno Melis
51/69
Telecom Italia Proprietary
( )
CQI definition
-
7/30/2019 LTE by Bruno Melis
52/69
Telecom Italia Proprietary
The CQI table is defined in terms of channel coding rate and modulation scheme
A UE reports a CQI index corresponding to a transport format with 10% BLER target at
the first H-ARQ transmission, over the set of PRBs corresponding to the CQI value.
CQI index modulation code rate x 1024 efficiency
0 out of range
1 QPSK 78 0.1523
2 QPSK 120 0.2344
3 QPSK 193 0.3770
4 QPSK 308 0.6016
5 QPSK 449 0.87706 QPSK 602 1.1758
7 16QAM 378 1.4766
8 16QAM 490 1.9141
9 16QAM 616 2.4063
10 64QAM 466 2.7305
11 64QAM 567 3.3223
12 64QAM 666 3.9023
13 64QAM 772 4.523414 64QAM 873 5.1152
15 64QAM 948 5.5547
CQI reporting
-
7/30/2019 LTE by Bruno Melis
53/69
Telecom Italia Proprietary
CQI reporting is periodic or aperiodic
UE transmits CQI reporting on the PUCCH for subframes with no PUSCH transmission and
on the PUSCH for those subframes with scheduled PUSCH transmissions
Three reporting methods:
* Details in 3GPP TS 36.213
Wideband CQI
Higher Layer-configured subband feedback
UE-selected subband feedback (best-M algorithm)
A subband is a set of k contiguous PRBs, where k is semi-statically configured by higher
layersSystem Bandwidth Subband Size
DLRBN
(k)
6 - 7 (wideband CQI only)
8 - 10 411 - 26 4
27 - 64 6
64 - 110 4, 8
Downlink Power Allocation
-
7/30/2019 LTE by Bruno Melis
54/69
Telecom Italia Proprietary
Downlink power allocation determines the Energy Per Resource Element (EPRE)
The EPRE denotes the energy prior to CP insertion and averaged over all constellation
points
A UE assumes downlink RS EPRE is constant across the downlink system bandwidth and
constant across all subframes until different RS boosting information is received
For each UE, the PDSCH-to-RS EPRE ratio in all the OFDM symbols containing RS is equal
to P_A, whereas in the OFDM symbols not containing RS is equal to P_B
The cell-specific ratio between P_A and P_B is determined by eNB based on the cell-
specific RS boosting value
P_A(EPRE)RS
(EPRE)PDSCH P_B
(EPRE)RS
(EPRE)PDSCH
OFDM symbols with RS OFDM symbols without RS
Uplink Power Control (1/2)
-
7/30/2019 LTE by Bruno Melis
55/69
Telecom Italia Proprietary
Uplink power control determines the average power over a DFT-SOFDM symbol in which
the physical channel is transmitted
The setting of the UE Transmit power for the physical uplink shared channel (PUSCH)
transmission in subframe i is defined by
)}())(()())((log10,min{)( MCSO_PUSCHPUSCH10MAXPUSCH ifiMCSPLjPiMPiP
where:
= maximum allowed power that depends on the UE power class
= bandwidth of the PUSCH transmission expressed in number of PRB
= parameter with 1 dB resolution signalled by higher layers
MAXP
)(PUSCH iM
)(O_PUSCH jP
Uplink Power Control (2/2)
-
7/30/2019 LTE by Bruno Melis
56/69
Telecom Italia Proprietary
= 3-bit cell specific parameter signalled by HL
= downlink pathloss estimate calculated in the UE
= cell specific values function of MCS and signalled by RRC
= UE specific correction value
1,9.0,8.0,7.0,6.0,5.0,4.0,0
PL
))((MCS iMCS
)( if
)()1()( P U S C HP U S C H Kiifif
= is a UE specific correction value, also referred to as a TPC command and
transmitted on PDCCH
P U S C H
* Details in 3GPP TS 36.213
Static ICIC: Fractional Frequency Reuse
-
7/30/2019 LTE by Bruno Melis
57/69
Telecom Italia Proprietary
f
P
f
P
f
P
P
P
PbN N
bN N
bN N
b
Static ICIC: Soft Frequency Reuse
-
7/30/2019 LTE by Bruno Melis
58/69
Telecom Italia Proprietary
f
P
P
f
P
P
f
P
P
Semi static ICIC
-
7/30/2019 LTE by Bruno Melis
59/69
Telecom Italia Proprietary
eNB
eNB
eNB
Reactive ICIC
Reactive ICIC
Release 8Proactive ICIC messages over X2:UL: HII (High Interference Indicator)DL: RNTP (Relative Narrow band Transmit Power)Reactive ICIC messages over X2:UL: OI (Overload Indicator)
LTE Standard Specifications
-
7/30/2019 LTE by Bruno Melis
60/69
Telecom Italia Proprietary
Physical layer specifications: TS 36.201: Physical layer General description
TS 36.211: Physical channels and modulation
TS 36.212: Multiplexing and channel coding
TS 36.213: Physical layer procedures
TS 36.214: Physical layer Measurements
36.211Physical Channels and
Modulation
36.212Multiplexing and channel
coding
36.213Physical layer procedures
36.214Physical layer
Measurements
To/From Higher Layers
Stage 2 specification:
TS 36.300: E-UTRA and E-UTRAN Overall description
LTE Standard Specifications
-
7/30/2019 LTE by Bruno Melis
61/69
Telecom Italia Proprietary
Layer 2 specifications:
TS 36.304: User Equipment (UE) procedures in idle mode
TS 36.306: User Equipment (UE) radio access capabilities
TS 36.321: Medium Access Control (MAC) protocol specification
TS 36.322: Radio Link Control (RLC) protocol specification
TS 36.323: Packet Data Convergence Protocol (PDCP)
Radio Resource Control (RRC)
Medium Access Control
Transport channels
Physical layerControl/Measurements
Layer 3
Logical channels
Layer 2
Layer 1
Radio interface protocol
architecture around physical layer
Layer 3 specifications:
TS 36.331: Radio Resource Control (RRC) protocol specification
-
7/30/2019 LTE by Bruno Melis
62/69
Telecom Italia Proprietary
LTE Advanced overview
LTE-A requirements: R8 and beyond
-
7/30/2019 LTE by Bruno Melis
63/69
Telecom Italia Proprietary
The Table summarizes some requirements of the Release 8 LTE system and of the LTE-Advanced (LTE-A)(1)
(1)3GPP TR 36.913 , Requirements for LTE-Advanced
(2) Achievable by means of Carrier Aggregation
(3) R1-072444, Summary of Downlink Performance Evaluation. Ericsson, TSG-RAN WG1 #49
(4) R1-072261, LTE Performance Evaluation - Uplink Summary. Vodafone, TSG-RAN WG1 #49
Release 8 LTE Next Releases LTE-A (3GPP targets in TR 36.913)
Downlink Uplink Downlink Uplink
Peak data rate300 Mbps (4x4 MIMO)
150 Mbps (2x2 MIMO)
75 Mbps (1x2 SIMO)
150 Mbps (Virtual MIMO)
3 Gbps (8x8 MIMO, low
mobility)
1.5 Gbps (4x4 MIMO, low
mobility)
Bandwidth Up to 20 MHz Up to 20 MHz Up to 100 MHz (2) Up to 100 MHz (2)
Peak Spectrum
efficiency 16.3 bit/s/Hz
4.3 bit/s/Hz (1x2 SIMO)
8.6 bit/s/Hz (Virtual MIMO)
30 bit/s/Hz 15 bit/s/Hz
Average
Spectrum
efficiency
[bit/s/Hz/cell]
1.69 (2x2 MIMO) (3)
1.87 (4x2 MIMO)
2.67 (4x4 MIMO)
0.74 (1x2 SIMO) (4)
2.4 (2x2 MIMO) (1)
2.6 (4x2 MIMO)
3.7 (4x4 MIMO)
1.2 (1x2 SIMO) (1)
2.0 (2x4 MIMO)
LatencyData plane : 10 ms (round trip delay)
Control plane : 100 ms (idle to active state)
Data plane :
-
7/30/2019 LTE by Bruno Melis
64/69
Telecom Italia Proprietary
Carrier Aggregation
Carrier aggregation, where two or more component carriers, each with a bandwidth up to 20 MHz, are
aggregated, is considered for LTE-Advanced in order to support downlink transmission bandwidths larger than
20 MHz
Extended Multi-Antenna configurations
Extension of LTE downlink spatial multiplexing to up to eight layers is considered. For the uplink spatial
multipexing with up to four layers is considered.
Coordinated Multiple Point transmission and reception
This feature is considered as a tool to improve the coverage of high data rates, the cell-edge throughput and/or
to increase system throughput
Relaying functionality
Relaying is considered for LTE-Advanced as a tool to improve e.g. the coverage of high data rates, temporarynetwork deployment, cell-edge throughput and/or to provide coverage in new areas.
Carrier Aggregation
Carrier aggregation, where two or more component carriers are aggregated, is considered for LTE-Advanced in
-
7/30/2019 LTE by Bruno Melis
65/69
Telecom Italia Proprietary
gg g , p gg g ,
order to support wider transmission bandwidths (e.g. up to 100 MHz) and for spectrum aggregation.
A terminal may simultaneously receive or transmit one or multiple component carriers depending on its
capabilities:
An LTE-Advanced terminal with reception and/or transmission capabilities for carrier aggregation can
simultaneously receive and/or transmit on multiple component carriers.
An LTE Rel-8 terminal can receive and transmit on a single component carrier only, provided that the structure
of the component carrier follows the Rel-8 specifications.
The L1 specification shall support carrier aggregation for both contiguous and non-contiguous component carriers
with each component carrier limited to a maximum of 100 RBs (using the Release 8 numerology)
It will be possible to configure a UE to aggregate a different number of component carriers of possibly different
bandwidths in the UL and the DL.
frequency
Case A : Contiguous components Case B : Non-Contiguous components
MIMO techniques for LTE (downlink)
-
7/30/2019 LTE by Bruno Melis
66/69
Telecom Italia Proprietary
The Release 8 LTE downlink standard supports both SU-MIMO (where the data are transmitted to a single UE)
and MU-MIMO (where the data are transmitted to multiple UEs that are co-scheduled in the same resources).
Release 8 Release 10 and beyond
Max. Num. of codewords 2 2
Max. Num. of layers 4 8
MIMO Configurations Up to 4x4 Up to 8x8
Support of SU-MIMO Yes Yes
SU-MIMO Techniques
Spatial Multiplexing
Space Frequency Block Coding (SFBC)
Closed Loop Precoding
Cyclic Delay Diversity (CDD)
Single Layer Beamforming
All the Release 8 techniques plus double
layer beamforming and 8 layer
transmission
Support of MU-MIMO Yes Yes
MU-MIMO features
Codebook based precoding
Maximum two co-scheduled UEs
Single layer for each UE
Non-codebook based precoding
Maximum of four co-scheduled UEs
Multiple layers for each UE
MIMO techniques for LTE (uplink)
-
7/30/2019 LTE by Bruno Melis
67/69
Telecom Italia Proprietary
The Release 8 LTE uplink standard supports the receive antenna diversity at the eNode B.
The antenna selection at the UE is an optional feature for all UE categories.
The standard also supports the so-called Virtual MIMO that is the equivalent of the downlink MU-
MIMO where two UEs can be simultaneously scheduled in the same uplink resources.
Release 8 Release 10 and beyond
Multiple access method SC-FDMA (contiguous RB mapping) SC-FDMA (clustered RB mapping)
Max. Num. of codewords 1 2
Max. Num. of layers 1 4
MIMO Configurations Up to 1 x 4 Up to 4 x 4
Support of Spattial Multiplexing No Yes
SU-MIMO Techniques Only Rx diversity supported at the eNB
UE antenna selection is optional
Spatial Multiplexing
Precoding for data channels
TX diversity for control channels
Support of MU-MIMO Yes Yes
Coordinated Multipoint Transmission (CoMP)
Coordinated multipoint (CoMP) transmission/reception is considered for LTE-Advanced as a tool to improve the
-
7/30/2019 LTE by Bruno Melis
68/69
Telecom Italia Proprietary
Coordinated multipoint (CoMP) transmission/reception is considered for LTE Advanced as a tool to improve the
coverage of high data rates, the cell-edge throughput and/or to increase system throughput.
Downlink coordinated multi-point transmission implies dynamic coordination among multiple geographically
separated transmission points.
3GPP currently considers two types of downlink CoMP:
Joint Processing (JP): data is available at each point in CoMP cooperating set.
Joint Transmission: transmission from multiple points at a time to a single UE to
improve the received signal quality and/or cancel actively interference for other
UEs.
Dynamic cell selection: transmission from one point at a time (within CoMP
cooperating set).
Coordinated Scheduling/Beamforming (CS/CB): data is only available at serving cell
(data transmission from that point) but user scheduling/beamforming decisions are made
with coordination among cells corresponding to the CoMP cooperating set. controldata
MME/S-GWMME/S-GW
Relaying functionality
-
7/30/2019 LTE by Bruno Melis
69/69
Telecom Italia Proprietary
Relaying is considered for LTE-Advanced as a tool to improve e.g. the coverage of high data rates, temporary
network deployment, cell-edge throughput and/or to provide coverage in new areas.
The Relay Node (RN) is wirelessly connected to radio-access network via a donor cell. There are two bi-
directional radio links/interfaces:
the RN / UE interface access link
the eNB / RN interface backhaul link eNB
RN
UE
Access linkBackhaul link
Donor cellDirect link
eNB
RN
UE
Access linkBackhaul link
Donor cellDirect link
eNodeB
Relay
Node
Relay
Node
UEUE
UE
UE
UE
LOS/NLOS link
NLOS link
eNodeB
Relay
Node
Relay
Node
UEUE
UE
UE
UE
LOS/NLOS link
NLOS link
Backhaul links may employ
directional antennas.
Source: R1-090593, 3GPP RAN1#56