Sect.03 - Basic technologies and concepts (m004) - 16-02-04-1.pptx

Introduction to
Long Term Evolution (LTE)
Technologies
Basic technologies
and concepts

BASIC TECHNOLOGIES and CONCEPTS
Basic technologies and concepts
 Traffic direction
 Bidirectional transmission modes
 Radio medium sharing modes
 Antenna basics
 Directivity / Gain
 Radiation patterns
 MIMO technologies
 Diversity
 Spatial multiplexing
 Beam forming
 OFDM vs. OFDMA
 Errors handling
 FEC
 ARQ
 H-ARQ
 Operation flow
 APN (Access Point Name)
 AS / NAS (Access Stratum / Non-Access
Stratum)

BASIC TECHNOLOGIES
Traffic direction
Up link (UL)
 UE to eNB
Down link (DL)
 eNB to UE
Bidirectional transmission modes
HD - Half Duplex
 Nodes can not transmit and receive simultaneously
 A half duplex eNB can communicate only with half duplex UE
FD - Full Duplex
 Nodes can transmit and receive simultaneously
 A full duplex eNB can support both half duplex and full duplex UE
Radio medium sharing modes (Duplex modes)
FDD - Frequency Division Duplex
 Uplink traffic occurs on one frequency, downlink traffic occurs on a different frequency
 Supports both half duplex and full duplex operation of nodes
 Efficient for symmetric traffic (similar data amounts in UL and DL)
TDD - Time Division Duplex
 Uplink traffic and downlink traffic occur on same frequency
 Supports only half duplex operation of nodes
 Efficient for asymmetric traffic (e.g. DL data amount significantly greater than UL data amount)
SAE GW
eNB
eNB
Uu
S11
S5/S8
Uu
S6a
Gxc
Gx/S7
Rx
X2
MME
S10
E-UTRAN Evolved Packet Core (EPC)
UE
UE
PCRF
HSS
S
GW
PDN /
IMS
SGi
P
GW
UL
DL
R

BASIC TECHNOLOGIES
Antennas basics
Definitions
Generator
 l[m] = wavelength =
 f = 2.4 GHz  l = 12.5 cm
 f = 700 MHz  l = 43 cm
 Transmission line
 The device used to guide RF energy from one point to another one, with minimum
attenuation, heat and radiation losses
 Guides the energy
 Radio antenna
 The structure associated with the region of transition between a guided wave and a free
space wave, or vice versa
 Radiates/receives energy
 Transmission line
(spacing between
wires is only a fraction
of the wave length)
 Antenna
(separation between
wires is in the range
of one or more wave
lengths)
c [3*108m/s]
f [Hz]

BASIC TECHNOLOGIES
Antennas basics
Directivity / Gain
 The energy fed into the antenna is radiated
in the whole space.
 A receiver RCV, located in the far field of the
transmitter, gets the basic element of energy
generated by the presence of 17dBm (50mW)
in the whole space.
 The energy fed into the antenna is radiated
only in part of the space.
 A receiver RCV, located in the far field of the
transmitter, gets the basic element of energy
generated by the presence of 17dBm (50mW)
in the defined volume, which is equivalent
with the presence of much more energy
isotropically distributed.
 Isotropic antenna (theoretical)
 Non-isotropic antenna (real)
Generator
17dBm (50mW)
Generator
17dBm (50mW)
RCV
RCV

BASIC TECHNOLOGIES
Antennas basics
Directivity / Gain
 For same amount of energy fed into the
antenna, a non-isotropic antenna will
transmit its signal over longer distances.
 Non-isotropic antennas are characterized by
their capability to focus the transmitted
energy, expressed by the antenna gain
 An antenna with 3dBi gain, radiates its
energy into 50% of the space
 A 3dBi antenna fed with 17dBm (50mW)
behaves (in its active field) as an isotropic
antenna fed with 20dBm (100mW)
 Even if, in fact, the antenna radiates only
17 dBm (50mW), it is said that it radiates
20 dBm (100mW) EIRP (Equivalent
Isotropically Radiated Power)
Antenna gain = [dBi]
volume (radiation) of subject antenna
volume (radiation) of isotropic antenna
Generator
17dBm (50mW)
RCV
Generator
17dBm (50mW)
RCV
Powerinput [dBm] + Gain [dBi] = Poweroutput [dBm EIRP]

Type
Gain
[dBi]
Radiation pattern
Half Power Beam Width (HPBW)
Horizontal Vertical
Omni-directional 2 dBi
± 180º
(omni directional)
± 60º
Omni-directional 6 dBi
± 180º
(omni directional)
± 10º
BASIC TECHNOLOGIES
Antennas basics
Radiation patterns - Concept
Powerout [dBm EIRP] = Powerin [dBm] + Gain [dBi]
Half Powerout [dBm EIRP]
+ 60º

Type
Gain
[dBi]
Radiation pattern
Horizontal Vertical
Uni-directional 8.5 dBi
± 37º
(uni directional)
± 37º
Uni-directional 12 dBi
± 11º
(uni directional)
± 11º
BASIC TECHNOLOGIES
Antennas basics

Type
Gain
[dBi]
Radiation pattern
Horizontal Vertical
± 7º
(uni directional)
± 7º
± 3.7º
(uni directional)
± 3.7º
BASIC TECHNOLOGIES
Antennas basics

Type
Gain
[dBi]
Radiation pattern
Horizontal Vertical
Sectorial 17 dBi ± 32.5º ± 3.6º
Sectorial 12 dBi ± 31.5º ± 10.5º
BASIC TECHNOLOGIES
Antennas basics

BASIC TECHNOLOGIES
Antennas basics
Radiation patterns - Actual examples
Horizontal pattern Vertical pattern

BASIC TECHNOLOGIES
Antennas basics
Multiple antennas technologies (MIMO - Multiple Input, Multiple Output)
 MIMO - Multiple Input Multiple Output
 Generic name relating to technologies using multiple antennas for
transmission / reception
 The name relates to the transmission channel (into which multiple
signals (from multiple antennas) are injected, while delivering multiple
output signals (toward multiple receiving antennas)
 Differentiation of signals generated by different antennas is achieved
via signals' orthogonality obtained via:
 antennas space diversity (antennas mechanically separated by a
few λ (signal wavelength) (could be done in BS but can not be done in UEs
which have small form factor ... ), or
 antennas space polarization
The antennas can handle SAME or DIFFERENT data streams (layers)
Multi-antenna mode
Number of simultaneously transmitted data streams
over multiple antennas (= number of layers)
(same frequencies, same time, different polarization)
Gain
Diversity
Tx
one layer
Higher gain (greater distance
and/or higher modulation order)
Rx
Spatial multiplexing
SU-MIMO
multiple layers
User throughput:
increased
MU-MIMO
Aggregate throughput:
increased
Beam forming one / multiple layer(s) Distance, Capacity
SU - Single User
MU - Multi User
MIMO - Multiple In, Multiple Out
Maximum values - up to rel.10
eNB
antennas
Data
streams
(layers)
UE
antennas
DL 4 (Tx) 2 2 (Rx)
UL 4 (Rx) 1 1 (Tx)
Maximum values - rel.10
eNB
antennas
Data
streams
(layers)
UE
antennas
DL 8 (Tx) 8 8 (Rx)
UL 8 (Rx) 4 4 (Tx)
2
1
8
4

BASIC TECHNOLOGIES
Antennas basics
Multiple antennas technologies
Diversity
 Scope - reducing the amount of fading by combining - at receiver - multiple copies of same signal
 The multiple copies of same signal have to encounter different fading over the channel, i.e. the
different propagation channels have to have low mutual correlation
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Tx entity
T1
Rx entity
R1
Nt Nr
mode
data streams
(same freq, same time)
Diversity one
Spatial muxing multiple
Beam forming one / multiple
4 x 1 1 x 4 4 x 4
Rx entity
R1
Tx entity Nt Nr
T1
Tx entity Rx entity
Nt Nr
T1 R1

Tx entity Rx entity
Nt Nr
T1 R1
BASIC TECHNOLOGIES
Antennas basics
Diversity
Rx entity
R1
Tx entity
T1
Tx entity
T1
Rx entity
R1
Transmit diversity
 Same signal transmitted on multiple antennas
 Gain: 10log(Nt) (e.g. for 2 Tx antennas => 3dB gain)
 Increase in gain can be used for:
 Distance increase and / or
 Throughput increase (higher modulation order)
 Risk of destructive interference at the receiving antenna; solution to avoid it:
 Alamouti technique; defined for two antennas and two subcarriers only
 antenna#1 transmits symbol#1 and symbol#2 on different sub-carriers
 antenna#2 transmits phase modified versions of symbol#1 and symbol#2 on
different sub-carriers
 the receiver is not involved in the decision (logical open loop operation)
Nt Nr
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Nt Nr
mode
data streams
Diversity one
 One layer
(one block/stream)(blue)
 4 antennas
4 x 1 MISO
MISO - Multiple
Input Single Output
1 x 4 SIMO 4 x 4 MIMO

BASIC TECHNOLOGIES
Antennas basics
Diversity
Rx entity
R1
Tx entity
T1
Tx entity
T1
Rx entity
R1
Receive diversity
 Same signal received on multiple antennas
 Gain: 10log(Nr) (e.g. for 2 Rx antennas => 3dB gain)
Transmit and Receive diversity
 Same signal transmitted on multiple antennas and received on multiple antennas
(Nt and Nr could have different values)
 Gain: 10log(Nt) + 10log(Nr)
Nt Nr
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Nt Nr
mode
data streams
Diversity one
1 x 4 SIMO 4 x 4 MIMO
Tx entity Rx entity
Nt Nr
T1 R1
4 x 1 MISO
MISO - Multiple
Input Single Output
SIMO - Single INput
Multiple Output

 Nt = 2; Nr = 2; Nr of layers, RI= 2
BASIC TECHNOLOGIES
Antennas basics
Spatial multiplexing (a.k.a. multi-layer transmission, MIMO)
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Tx entity
T1
Nt Nr
T2
Rx entity
R1
R2
Single User spatial multiplexing (SU-MIMO)
 Multiple different streams
(multiple layers, Rank Indicator - RI = nrs) over multiple antennas
(same frequencies, same time, different antennas with different polarization)
 Aggregate capacity: Capacitysingle-stream * RI
 Gain per stream: 10log(Nt-stream) + 10log(Nr-stream)
 Throughput increase (higher modulation order, per stream)
 Correct recovery occurs if the signals received at the two antennas
are different (not good in clear Line Of Sight - LOS)
UE
eNB
mode
data streams
Diversity one
Requires calibration, to calculate channel influence on
each transmitter to receiver path; executed via a priori
known Reference Signals transmitted periodically by eNB
During calibration
Known elements: T1, T2, R1, R2
Calculated elements: x11, x12, x21, x22
During operation
Known elements: R1, R2, x11, x12, x21, x22
Calculated elements: T1, T2
R1 = x11*T1 + x21*T2
R2 = x12*T1 + x22*T2
Channel
T1
T2
R1
R2
x11
x12
x21
x22
Tx entity
T1
Nt Nr
T2
Rx entity
R1
R2
UE
eNB
RI - Rank Indicator
nrs - nr of streams
 Nt-stream = 2; Nr = 2; Nr of layers, RI= 2

BASIC TECHNOLOGIES
Antennas basics
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Tx entity
T1
Nt Nr
T2
Rx entity
R1
R2
 If the signals received at the antennas are not different enough for decoding, then:
 Open loop operation
 UE may ask eNB to switch to diversity mode, i.e. to transmit one single stream over
multiple antennas (instead of two streams on multiple antennas) => lower capacity, higher
resilience
 UE request is done by indicating desired RI - Rank Indicator (number of layers, number of
simultaneous streams that Rx-er can receive)
 RI = 2 - Spatial Multiplexing (high capacity)
 RI = 1 - Diversity (high resilience)
UE
eNB
mode
data streams
Diversity one
During calibration
During operation
R1 = x11*T1 + x21*T2
R2 = x12*T1 + x22*T2
Channel
T1
T2
R1
R2
x11
x12
x21
x22
RI - Rank Indicator

BASIC TECHNOLOGIES
Antennas basics
Nt - nr of Tx ant.
Nr - nr of Rx ant.
Tx entity
T1
Nt Nr
T2
Rx entity
R1
R2
 If the signals received at the antennas are not different enough for decoding, then:
 Closed loop operation
 UE sends to eNB the desired RI
 UE sends to eNB the desired Precoding Matrix Indicator (PMI) to be used by eNB (phase,
amplitude modifications so that the signals will arrive correctly at UE) to minimize the
effect of fading
Fading is function of frequency, so PMI is function of frequency... UE may report PMIs for
different frequencies, helping BS to select the right frequencies for transmission
(OFDMA!)
 Closed loop needs time => not good for fast moving UEs, where the conditions change
fast and the reporting mechanism brings to transmitter information that is not relevant
anymore...
UE
eNB
mode
data streams
Diversity one
During calibration
During operation
R1 = x11*T1 + x21*T2
R2 = x12*T1 + x22*T2
Channel
T1
T2
R1
R2
x11
x12
x21
x22
RI - Rank Indicator
PMI- Precoding
Matrix Indicator
UE - User Equip.
BS - Base Station

BASIC TECHNOLOGIES
Antennas basics
Transmission modes (LTE) - Down Link (DL)
Transmission Modes (TM) - DL TS 36.213
TM 1
Single transmit
antenna
SISO or SIMO
TM 2
Transmit
diversity
 Transmit diversity - One stream over multiple antennas
 Used as fall back option, when spatial multiplexing (multiple streams over multiple
antennas) cannot be used
TM 3
Open loop
spatial
multiplexing
with CDD
 Spatial multiplexing - Multiple streams over multiple antennas
 All streams to same UE
 Open loop - UE does not request from eNB specific transmission parameters for
efficient reception (as function of radio channel conditions)
 Used when no channel info is available, or when channel parameters are changing very
fast (e.g. UE high speed movement)
 To increase frequency diversity, the signals are presented to different antennas with
different delays (CDD) (equivalent to phase modification in frequency domain)
TM 4
Closed loop
spatial
multiplexing
 All streams to same UE
 Closed loop - UE requests from eNB specific transmission parameters for efficient
reception (as function of radio channel conditions)
 The request uses an index referring to a table listing precoding matrixes (Precoding
Matrix Index - PMI)
 The table lists precoding for both the case of one stream and the case of two streams
 Fall back to transmit diversity
CDD - Cyclic Delay Diversity
PMI - Precoding Matrix Index
RI - Rank Indicator
SU-MIMO - Single User MIMO
MU-MIMO - Multi User MIMO
CoMP - Coordinated Multi-Point
SISO - Single In Single Out
SIMO - Single In Multiple Out

BASIC TECHNOLOGIES
Antennas basics
RI - Rank Indicator
SISO - Single In Single Out
SIMO - Single In Multiple Out

BASIC TECHNOLOGIES
Antennas basics
RI - Rank Indicator
Transmission modes (TM) - DL MIMO type
Nr of
streams
Nr of
antennas
Streams direction
UE request for
precoding (loop)
TM 1 Single transmit antenna - 1 1 to single UE -
TM 2 Transmit diversity Diversity 1 up to 8 to single UE -
TM 3
Open loop spatial
multiplexing (SU-MIMO)
Spatial mux 2 or 4 2 or 4 all to same UE no
TM 4
Closed loop spatial
multiplexing (SU-MIMO)
Spatial mux 2 or 4 2 or 4 all to same UE yes
TM 5
Multi-user MIMO (MU-
MIMO)
Spatial mux 2 or 4 2 or 4 one stream per UE yes
TM 6
Closed loop spatial
multiplexing with RI=1
Spatial mux 1 2 or 4 to single UE yes
TM 7 One layer beamforming Beamforming 1 2 or 4 to single UE -
TM 8 Dual layer beamforming Beamforming 2 2 or 4
all to same UE (SU-MIMO) -
one per UE (MU-MIMO) -
TM 9 8 layer transmission Spatial mux up to 8 up to 8
all to same UE (SU-MIMO) -
one per UE (MU-MIMO) -
TM 10
Support for CoMP
(Coordinated Multi-Point)
- - - - -

BASIC TECHNOLOGIES
Antennas basics
Transmission modes (LTE) - Up Link (UL)
RI - Rank Indicator
Transmission Modes (TM) - UL TS 36.213
TM 1
Single transmit
antenna
-
TM 2
(Rel.10)
Closed loop
spatial
multiplexing
 Closed loop - eNB requests from UE specific transmission parameters for efficient
reception (as function of radio channel conditions)
 The request uses an index referring to a table listing precoding matrixes (Precoding
Matrix Index - PMI)

BASIC TECHNOLOGIES
OFDM vs. OFDMA
f
user G
traffic
user R
traffic
user B
traffic
user P
traffic
t
t
f
user V
traffic
 OFDM - Orthogonal Frequency Division Multiplexing
 Radio technology carrying traffic over multiple sub-carriers simultaneously
 OFDMA - Orthogonal Frequency Division Multiple Access
 Multiple stations access method, allowing stations to transmit/receive using OFDM over limited
amount of frequencies and for limited time
OFDM OFDM sub-channelization OFDMA
Frequency
allocation
per user
all sub-carriers some sub-carriers some sub-carriers
Time
allocation
per user
all the time all the time limited time
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
OFDM - Orthogonal Frequency
Division Multiplexing
OFDMA - Orthogonal Frequency
Division Multiple Access

BASIC TECHNOLOGIES
OFDM vs. OFDMA
 In LTE OFDMA
 Frequency axis has granularity of groups of 12 sub-carriers
 Time axis has granularity of 0.5 ms
 The block of 12 sub-carriers * 0.5ms is known as a Resource Block (RB)
 1 RB = 12 sub-carriers * 0.5ms
 Resource allocation in LTE OFDMA is executed
with the granularity of
 12 subcarriers in frequency domain (1 RB)
 1 ms in time domain (1 sub-frame, 1 RB pair)
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
1ms
0.5ms
1
RB
1
RB pair
OFDM - Orthogonal Frequency
Division Multiplexing
OFDMA - Orthogonal Frequency
Division Multiple Access
RB - Resource Block

BASIC TECHNOLOGIES
Channel / carrier / band / site / sector / multicarrier
Channel
A group of RBs (frequencies) allocated to operator (used by eNB) for radio communication
For data transfer to/from users, eNB can allocate to each UE from 1 to all RBs, depending on
the amount of data to be transferred
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
1ms
0.5ms
LTE channel
widths
Nr. of
RBs
Channel
width
[MHz]
6 1.4
15 3
25 5
50 10
75 15
100 20
Channel
(6 RBs, 1.4 MHz)
Carrier
The frequency around which a channel is located (i.e. the central frequency of a channel)
Carrier
(2.340 GHz)

BASIC TECHNOLOGIES
Band
A range of frequencies allocated for LTE usage
f
1ms
0.5ms
user R
traffic
user B
traffic
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
Channel
(6 RBs, 1.4 MHz)
Carrier
(2.340 GHz)
(EARFCN - 39050)
Band
40
(2.3
GHz
-
2.4
GHz)
2.3 GHz
2.4 GHz
E-UTRA
Operating
Band
Uplink (UL) operating band
BS receive
UE transmit
Downlink (DL) operating band
BS transmit
UE receive
1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz
2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz
3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz
4 1710 MHz – 1755 MHz 2110 MHz – 2155 MHz
5 824 MHz – 849 MHz 869 MHz – 894MHz
6 830 MHz – 840 MHz 875 MHz – 885 MHz
7 2500 MHz – 2570 MHz 2620 MHz – 2690 MHz
8 880 MHz – 915 MHz 925 MHz – 960 MHz
9 1749.9 MHz – 1784.9 MHz 1844.9 MHz – 1879.9 MHz
10 1710 MHz – 1770 MHz 2110 MHz – 2170 MHz
11 1427.9 MHz – 1447.9 MHz 1475.9 MHz – 1495.9 MHz
12 699 MHz – 716 MHz 729 MHz – 746 MHz
13 777 MHz – 787 MHz 746 MHz – 756 MHz
14 788 MHz – 798 MHz 758 MHz – 768 MHz
15 Reserved Reserved
16 Reserved Reserved
17 704 MHz – 716 MHz 734 MHz – 746 MHz
18 815 MHz – 830 MHz 860 MHz – 875 MHz
19 830 MHz – 845 MHz 875 MHz – 890 MHz
20 832 MHz – 862 MHz 791 MHz – 821 MHz
21 1447.9 MHz – 1462.9 MHz 1495.9 MHz – 1510.9 MHz
22 3410 MHz – 3490 MHz 3510 MHz – 3590 MHz
23 2000 MHz – 2020 MHz 2180 MHz – 2200 MHz
24 1626.5 MHz – 1660.5 MHz 1525 MHz – 1559 MHz
25 1850 MHz – 1915 MHz 1930 MHz – 1995 MHz
26 814 MHz – 849 MHz 859 MHz – 894 MHz
27 807 MHz – 824 MHz 852 MHz – 869 MHz
28 703 MHz – 748 MHz 758 MHz – 803 MHz
29 N/A 717 MHz – 728 MHz
30 2305 MHz – 2315 MHz 2350 MHz – 2360 MHz
31 452.5 MHz – 457.5 MHz 462.5 MHz – 467.5 MHz
...
33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz
34 2010 MHz – 2025 MHz 2010 MHz – 2025 MHz
35 1850 MHz – 1910 MHz 1850 MHz – 1910 MHz
36 1930 MHz – 1990 MHz 1930 MHz – 1990 MHz
37 1910 MHz – 1930 MHz 1910 MHz – 1930 MHz
38 2570 MHz – 2620 MHz 2570 MHz – 2620 MHz
39 1880 MHz – 1920 MHz 1880 MHz – 1920 MHz
40 2300 MHz – 2400 MHz 2300 MHz – 2400 MHz
41 2496 MHz 2690 MHz 2496 MHz 2690 MHz
42 3400 MHz – 3600 MHz 3400 MHz – 3600 MHz
43 3600 MHz – 3800 MHz 3600 MHz – 3800 MHz
44 703 MHz – 803 MHz 703 MHz – 803 MHz
 Carriers are located on specific grids within the band
 Possible carrier frequencies are defined by EARFCN -
E-UTRA Absolute Radio Frequency Channel Number
(0 to 65,535)
 TS 36.101 defines conversion of EARFCN into actual frequency
EARFCN - E-UTRA Absolute
Radio Frequency
Channel Number

Band
40
(2.3
GHz
-
2.4
GHz)
BASIC TECHNOLOGIES
Site
Geographical location of a tower
f
1ms
0.5ms
user R
traffic
user B
traffic
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
Channel
Carrier
2.3 GHz
2.4 GHz
Site
Sector
Geometry entity / direction
Cell
The radio entity covering a sector
Each cell uses one carrier / channel
(except the case of carrier aggregation)
Sector
Sector

Band
40
(2.3
GHz
-
2.4
GHz)
BASIC TECHNOLOGIES
f
1ms
0.5ms
user R
traffic
user B
traffic
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
Channel
2.3 GHz
2.4 GHz
Site
Multicarrier systems
Systems able to use multiple carriers
Adjacency
contiguous
non-contiguous
Bands
same
different
Timing
At different moments in time
(e.g. UE adapting itself to its serving eNB)
Sector
Sector
Simultaneously
Multi sector eNB, each sector using a different carrier (one device equivalent to multiple devices)
Single sector using multi-carrier aggregation; equivalent to a wider channel. Aggregate
capacity is same as the sum of the components; However, with carrier aggregation, a UE
can get the WHOLE aggregate channel width resulting in higher throughput per UE.
Carrier

BASIC TECHNOLOGIES
Radio frame structure - Type 1: FDD
 FDD division entities
 frame - 10 ms
 subframe - 1 ms
 slot - 0.5 ms
 Two identical structures are present
on different frequencies, for each direction (UL, DL)
frame 10 ms
subframe
# 1
1 ms
subframe
# 2
1 ms
subframe
# 3
1 ms
subframe
# 4
1 ms
subframe
# 5
1 ms
subframe
# 6
1 ms
subframe
# 7
1 ms
subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
frame 10 ms .
me subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
ot
5
s
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
3 14 15 16 17 18 19
frame 10 ms
subframe
# 1
1 ms
subfram
# 2
1 ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slo
0.5
m
0 1 2 3
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
1ms
0.5ms
frame 10 ms
subframe
# 1
1 ms
subframe
# 2
1 ms
subframe
# 3
1 ms
subframe
# 4
1 ms
subframe
# 5
1 ms
subframe
# 6
1 ms
subframe
# 7
1 ms
subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
frame 10 ms .
me subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
ot
5
s
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
3 14 15 16 17 18 19
frame 10 ms
subframe
# 1
1 ms
subfram
# 2
1 ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slo
0.5
m
0 1 2 3

frame 10 ms
subfr. # 1
1 ms
subfr. # 2
1 ms
subfr. # 3
1 ms
subfr. # 4
1 ms
subfr. # 5
1 ms
subfr. # 6
1 ms
subfr. # 7
1 ms
subfr. # 8
1 ms
subfr. # 9
1 ms
subfr. #10
1 ms
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
frame 10 ms .
me subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
ot
5
s
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
3 14 15 16 17 18 19
frame 10 ms .
me subframe
# 8
1 ms
subframe
# 9
1 ms
subframe
# 10
1 ms
ot
5
s
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
slot
0.5
ms
3 14 15 16 17 18 19
frame 10 ms
subfr. # 1
1 ms 1 ms
0 1 2 3
f
user R
traffic
t
user V
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user P
traffic
user B
traffic
1ms
0.5ms
user B
traffic
user V
traffic
user G
traffic
user P
traffic
user G
traffic
user O
traffic
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
1ms
0.5ms
frame 10 ms
subfr. # 1
1 ms
subfr. # 2
1 ms
subfr. # 3
1 ms
subfr. # 4
1 ms
subfr. # 5
1 ms
subfr. # 6
1 ms
subfr. # 7
1 ms
subfr. # 8
1 ms
subfr. # 9
1 ms
subfr. #10
1 ms
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
frame 10 ms
subfr. # 1
1 ms 1 ms
0 1 2 3
BASIC TECHNOLOGIES
Radio frame structure - Type 1: FDD
f
UL
DL
 Two identical structures are present
on different frequencies, for each direction (UL, DL)

BASIC TECHNOLOGIES
Radio frame structure - Type 2: TDD
 TDD division entities
 frame - 10 ms
 half frame - 5 ms
 subframe - 1 ms
 standard
 special
 dwPTS - DL Pilot Time Slot
 GP - Guard Period
 upPTS - UL Pilot Time Slot
 slot - 0.5 ms
 One single structure is present allowing UL and DL
traffic to share one single frequency (half duplex)
 The amount of subframes allocated to each
direction can be dynamically changed by eNB,
based on load conditions
frame 10 ms
half frame 0 half frame 1
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
frame 10 ms
half frame 1
me subframe
1 ms
subframe
1 ms
subframe
1 ms
ot slot slot slot slot slot slot
14 15 16 17 18 19
frame 10 ms
subframe
1 ms
subfram
1 ms
slot slot slot slo
0 1 1
Frame structure TDD (format for DL + UL, on same frequency)
dwPTS - DL Pilot Time Slot
upPTS - UL Pilot Time Slot
GP- Guard Period
f
user R
traffic
user B
traffic
t
user V
traffic
user G
traffic
RB #4 = 12 freq
RB #5 = 12 freq
RB #3 = 12 freq
RB #2 = 12 freq
RB #1 = 12 freq
RB #0 = 12 freq
user O
traffic
user B
traffic
user O
traffic
user P
traffic
user V
traffic
user B
traffic
1ms
0.5ms

UL / DL allocation configurations
0
1
2
3
4
5
6
BASIC TECHNOLOGIES
Radio frame structure - Type 2: TDD
D S U D D D S U D D
D S U U U D D D D D
D S U U D D D D D D
D S U D D D D D D D
D S U U U D S U U D
D S U U D D S U U D
D S U U U D S U U U
dwPTS Guard Period upPTS
 dwPTS - DL Pilot Time Slot - synchro and
user data + DL Control ch (scheduling and
control info)
 GP - Guard Period
 upPTS - UL Pilot Time Slot - for transmission
of PRA.CH and Sounding Ref Signal SRS
TS 36.211
frame 10 ms
half frame 0 half frame 1
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
subframe
1 ms
slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot slot
0 1 2 3 4 5 6 7 8 9
frame 10 ms
half frame 1
me subframe
1 ms
subframe
1 ms
subframe
1 ms
ot slot slot slot slot slot slot
7 8 9
frame 10 ms
subframe
1 ms
subfram
1 ms
slot slot slot slo
0 1
 The amount of subframes allocated to each
direction can be dynamically changed by eNB,
based on load conditions
 7 UL/DL allocation configurations are defined
dwPTS - DL Pilot Time Slot
upPTS - UL Pilot Time Slot
GP- Guard Period
U / D - UL / DL subframe
S - Special subframe

BASIC TECHNOLOGIES
Errors handling
 Errors over the air link are detected / corrected using:
 Forward Error Correction (FEC)
 Automatic Repeat Request (ARQ)
 Hybrid ARQ (H-ARQ)
Errors handling
 FEC
 ARQ
 H-ARQ

BASIC TECHNOLOGIES
Errors handling
Forward Error Correction (FEC)
 For error detection and correction
purposes, FEC transmits instead
of the original data bits, a bigger
quantity of OTHER bits
 Coding rate = amount of data bits / total amount of bits transmitted
actual bits transmitted (different and more than the original data)
Errors handling
 FEC
 ARQ
 H-ARQ
 Two major FEC techniques are used in LTE:
 Convolutional encoding (at transmission) with Viterbi decoding (at reception)
 Used for control channels
 Turbo convolutional encoding
 Used for data channels
Coding
rate value
Efficiency
Error
protection
level
High High Low
Low Low High
data bits (info to be transmitted)
actual bits transmitted (different and more than the original data)
data bits (info to be transmitted)

BASIC TECHNOLOGIES
Errors handling
Convolutional Encoding / Viterbi Decoding (for control channels)
 Basic coding rate is 1/3
 In order to improve coding
efficiency, some of the A, B, C
bits may be omitted while
transmitting (puncturing), and
reinserted as “dummy” bits at
reception (rate matching)
 If more bandwidth is available,
some of the bits could be
repeated (rate matching)
Convolutional
Encoder
Ai
Bi
Ci
xi
data
IN
encoded
data
Convolutional
Encoder
data
IN
data
OUT
channel
Convolutional Coding
encoded
data
+
errors
xi
Ai
Bi
Ci
encoded
data
Viterbi
decoder
Convolutional Encoding
Generator vector {1011011 (A); 1111001 (B); 1110101 (C)}
T
1
T
2
T
3
T
4
T
5
T
6
0
1
1
1
1
1
1
1
1
1
1
0
0
0
1
1
0
0
1
1
1
xi
data
IN
Ai
Bi
Ci
encoded
data
Errors handling
 FEC
 ARQ
 H-ARQ

BASIC TECHNOLOGIES
Errors handling
Turbo convolutional encoding (for data channels)
Turbo Convolutional Encoding
Ai
Bi
Ci
e
n
c
o
d
e
d
d
a
t
a
T T
T T
xi
data
IN
T
T
Turbo code
interleaver
 Turbo code - high performance FEC
mechanism
 Parallel concatenation of two
convolutional encoders operating on
 the original bits and on
 a permutation of the original bits
executed by an interleaver
 Basic coding rate is 1/3
 In order to improve coding efficiency,
some of the A, B, C bits may be omitted
while transmitting (puncturing)(rate
matching)
 If more bandwidth is available, some of
the bits could be repeated (rate matching)
Turbo
Encoder
data
IN
data
OUT
channel
Convolutional Coding
encoded
data
+
errors
xi
Ai
Bi
Ci
encoded
data
Decoder
Errors handling
 FEC
 ARQ
 H-ARQ

BASIC TECHNOLOGIES
Errors handling
Automatic Repeat Request (ARQ)
Three ARQ types are defined:
• Stop and Wait (Sliding window = 0)
• Go Back N
• Selective Repeat
Stop and Wait (Sliding Window = 0)
- Every transmitted block has to be acknowledged by receiver
- Absence of ACK within a specified timeout forces the transmitter to re-transmit the
un-acknowledged block
1
t
1
t
2
2
ACK 1 ACK 2
3
3
lack of
ACK 3
3
3
ACK 3
XMT
RCV
Errors handling
 FEC
 ARQ
 H-ARQ

BASIC TECHNOLOGIES
Errors handling
• Go Back N
Go Back N (Sliding Window  0)
- Multiple blocks (up to a maximum “window”) are transmitted before receiving ACK
- When a specific block is un-acknowledged, transmitter re-transmits the un-acknowledged
block and ALL the following blocks
1
t
1
t
2
2
3 4
3
XMT
RCV
5 6 7 4
4
NAK
4
5 6 7 4
5 6 7
5 6 7
Errors handling
 FEC
 ARQ
 H-ARQ
 LTE window in TS 36.322: 512

BASIC TECHNOLOGIES
Errors handling
• Go Back N
Selective Repeat (Sliding Window  0)
- Multiple blocks (up to a maximum “window”) are transmitted before receiving ACK
- When a specific block is un-acknowledged, transmitter re-transmits the un-acknowledged
block
1
t
1
t
2
2
3 4
3
XMT
RCV
5 6 7 4
4 5 6 7 4
8 9 10
8 9 10
Errors handling
 FEC
 ARQ
 H-ARQ
 LTE window in TS 36.322: 512
NAK
4

 Conventional ARQ discards blocks received with errors. H-ARQ keeps them.
 Multiple copies of same block are transmitted until receiver has enough cumulated information to
decode the block (time diversity).
 Useful for remote located stations that never have the chance of getting/transmitting one single
copy with enough energy
 Hybrid = joint operation of MAC and PHY
 At reception:
 Multiple H-ARQ processes in parallel, trying to recover several outstanding blocks
BASIC TECHNOLOGIES
Errors handling
Hybrid ARQ (H-ARQ)
1
t
1
t
2
2
ACK 1 NACK 2
2
2
NACK 2
2
2
ACK 2
XMT
RCV 2
2
3
total: 2
Errors handling
 FEC
 ARQ
 H-ARQ
 PHY performs retention and recombination
 MAC performs signalling (ACK/NACK as result of CRC check result)
Equivalent to decision based
on majority value for each bit

BASIC TECHNOLOGIES
Errors handling
Hybrid ARQ (H-ARQ)
Errors handling
 FEC
 ARQ
 H-ARQ
 LTE DL traffic handling via H-ARQ
 Sending ACK / NACK toward eNB - 4 sub-frames after reception of data block
 Resending (toward UE) blocks that have been NACK-ed by UE
 Asynchronous mode - retransmission can occur at any time (min 8ms). Requires signaling from eNB.
 Adaptive mode - Each retransmission is executed using a lower modulation level
t
eNB
Transmission in
sub-frame #n
NACK 1 in
sub-frame #n+4
Retransmission in
sub-frame #(n+4)+4 or later
4 sub-frames
(4 ms)
Synchronous
Asynchronous
t
NACK 1
UE
1
1 NACK 1
4 sub-frames
(4 ms) or more
 LTE UL traffic handling via H-ARQ
 Sending ACK / NACK toward UE - 4 sub-frames after reception of data block
 Resending (toward eNB) blocks that have been NACK-ed by eNB
 Synchronous mode - retransmission occurs 4 sub-frames (predefined time) after NACK reception
 Adaptive or non-adaptive mode - modulation and coding can change or not (as decided by eNB)
t
t
1 NACK
eNB
Transmission in
sub-frame #n
NACK 1 in
sub-frame #n+4
Retransmission in
Sub-frame #(n+4)+4
1
Synchronous
NACK 1
UE 1
4 sub-frames
(4 ms)
Synchronous
4 sub-frames
(4 ms)

BASIC TECHNOLOGIES
Errors handling
Operation flow
Errors handling
 FEC
 ARQ
 H-ARQ
H-ARQ ACK H-ARQ NACK
drop after n retransmissions
(e.g. 1 tx + 3 re-tx)
correct incorrect
no
ACK
FEC
processing
incoming
signal
H-ARQ
processing
ARQ processing
no packet
forwarded to
ARQ process
correct packet
forwarded to
ARQ process
ACK
CRC
 If H-ARQ is unsuccessful,
upper layer does not receive
the content of the respective
block
 Upper layer detects missing
data => activates ARQ (ARQ
applies to part of the block
protected by H-ARQ)

BASIC TECHNOLOGIES
Flow / Service / Bearer
 Flows and bearers are unidirectional entities
 For correct operation one entity should be present for each direction
 The diagrams in the slides show only one direction
 To remind the reader about the fact that only one single direction is represented, arrows are used
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
R
Glossary AS - Application Server
HQ - Head Quarter

BASIC TECHNOLOGIES
Flow
 Actual traffic (packets) generated by user (uni-directional entity)
 Packets that have to be handled by the network in the same way (delay, errors, etc.) are grouped
in "flows"
 Characterized by
 End points
 QoS (all packets that are part of same flow should get same network treatment, so that they
would experience same delay, same errors rate)
 Packets type (combination of data, voice, video)
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
Voice
flow
Video
flow
Data
flow
HQ
QoS - Quality of Service
AS - Application Server
HQ - Head Quarter
R
Glossary

BASIC TECHNOLOGIES
Service
 The activity executed by user, while using the network for traffic transport purposes
 The scope of generating and transmitting the packets over the network
 A service is composed of one or more "flows" per direction
Service Number of flows per direction Type of packets in the flows
e-mail 1 data
file transfer 1 data
video conference 2 (3) voice; video (data)
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
Internet surf service
Video conf service
Data
flow
Voice
flow
Video
flow
R
Glossary AS - Application Server
HQ - Head Quarter

BASIC TECHNOLOGIES
Service
 End points
 Type of packets present in the constituent flows
 Relationship among constituent flows (e.g. in video conference service, voice packets and video packets
are generated simultaneously and should be played simultaneously)
 The service is a concept valid outside the network, while in the network the service is represented
by independent packets / flows to be transported by the network under specific QoS terms
QoS - Quality of Service
HQ - Head Quarter
Glossary
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
Video conf service
Data
flow
Voice
flow
Video
flow
R

BASIC TECHNOLOGIES
Service
 A user may activate multiple services in the same time, e.g.
 Service #1 : surfing the Internet
 End points: UE , Internet
 Flow / Packets: data
 Service #2 : video conference
 End points: UE, Company HQ
 Flows / Packets: voice, video
Glossary
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
Video conf service
Data
flow
Voice
flow
Video
flow
R
HQ - Head Quarter

BASIC TECHNOLOGIES
Bearer
 Merriam-Webster: "A person who bears or carries something"
(for somebody else)
e.g. armour-bearer, bow-bearer
... traffic bearer (porter, transporter)
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
non-EPS bearer to HQ
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
EPS - Evolved Packet System
HQ - Head Quarter
R
to AS
Glossary

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 For the purpose of transporting / carrying user's packets (flows) through the network, an
encapsulation service (uni-directional) is created, known as a "bearer"
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
HQ - Head Quarter
R
to AS
Glossary

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 End points
 QoS
 Path in the network
 Capsule structure
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
HQ - Head Quarter
R
Glossary
LTE bearer is characterized by
 End points
 QoS

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 End points
 Same end points as those of the flow it carries
 e.g. EPS bearer end points: UE / P-GW
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
HQ - Head Quarter
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 QoS offered to the capsules carrying user data packets / flows
 In LTE, all packets in a bearer get same treatment resulting in the packets experiencing
basically same delay, same error rate
 Flows requiring different QoS, use different EPS bearers, e.g. in video conf.:
 Voice flow expected QoS: low delay, can live with error rate; constant bit rate
 Data flow expected QoS: low error rate, can live with delays; variable bit rate
 Video flow expected QoS: low delay, low error rate; constant or variable bit rate
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
QCI - Quality Class ID
HQ - Head Quarter
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 QoS offered to the capsules carrying user data packets / flows
GBR - Guaranteed Bit Rate (minimum committed / expected long term throughput average)
(suitable for real time signals (voice, video)) (Also has MBR - Maximum allowed Bit Rate)
non-GBR - (good enough for non real time applications (file transfer, internet access))
 Aggregate Max Bit Rate allowed per UE, for all UE's non-GBR bearers (UE-AMBR)
 Aggregate Max Bit Rate per P-GW, for all non-GBR bearers reaching a P-GW (APN-AMBR)
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
GBR - Guaranteed Bit Rate
AMBR - Aggregate Max Bit Rate
APN - Access Point Name
HQ - Head Quarter
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
QCI GBR type Priority
Delay
(ms)
Packet
error
rate
Typical usage
1 GBR 2 100 10-2 Conversational voice
2 GBR 4 150 10-3 Conversational video (live streaming)
3 GBR 3 50 10-3 Real time gaming
4 GBR 5 300 10-6 Video (buffered streaming)
5 Non-GBR
1
(highest)
100 10-6 IMS signaling
6 Non-GBR 6 300 10-6 Video (buffered streaming)
7 Non-GBR 7 100 10-3 Voice, Video (live streaming)
8 Non-GBR 8 300 10-6 TCP based
9 Non-GBR
9
(lowest)
300 10-6 TCP based
Bearer
 LTE bearer
 QoS
 Standardized
QCI (QoS Class
Identifier)
QCI - QoS Class ID
R
Glossary
TS 23.203

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 Could be a function of transported data flow QoS requirements
 Bearers carrying flows of same service could have different paths, if the flows require
different QoS
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 Fields added by the bearer source to the packet to be transported (marking of original
user packet) for the capsule to reach its intended destination, while experiencing the
intended QoS
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
EPS bearer
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
Radio bearer S1 bearer S5/S8 bearer
S1 bearer S5/S8 bearer
Radio bearer
Bearer
 LTE bearer
 EPS bearer traverses multiple interfaces and technologies; capsule structure in each
section is different => the EPS bearer is in fact a concatenation of multiple bearers
 Bearers are identified by Tunnel ID; Tunnel ID mapping from one bearer to another is
executed in the relevant devices, in each direction separately
R
Glossary
 End points
 QoS

BASIC TECHNOLOGIES
Bearer
 LTE bearer
 Default / dedicated bearer
 At connection to network, UE receives automatically one default non-GBR EPS bearer up
to a P-GW; it provides to UE "always on" access to a pre-defined network (e.g. Internet)
 UE can establish connections to additional networks; for each such network a default
non-GBR bearer is created
 After the creation of the default bearer to a network, UE can create dedicated bearers to
same network, usually GBR
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
Radio bearer
R
Glossary

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
AS
HQ
EPS bearer
Voice
flow
Video
flow
Data
flow
Video conf service
non-EPS bearer
to AS
Radio bearer
Bearer
 LTE bearer
 Mapping of packets to bearers is executed through a classification/filtering process that
checks different fields in the ingress packet (defined in TFT - Traffic Flow Template)(usually IP
DA/SA, Protocol field in IP header, UDP/TCP port, etc.), by
 UE for UL traffic
 P-GW for DL traffic
R
TFT - Traffic Flow Template
Glossary

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
SGi
MME
S-GW1
S11 Rx
Bearer
 LTE bearer
 Mapping of packets to bearers is executed through a
classification/filtering process checking different fields in the
ingress packet (defined in TFT - Traffic Flow Template)
P-GW3
PDN 3
PDN 1
PDN 2
(usually IP DA/SA, Protocol field in IP header, UDP/TCP port, etc.), by
 UE for UL traffic
 P-GW for DL traffic
 UL mapping - When mapping a packet to a bearer (tunnel), UE "knows" which application
generated the packet (=> it knows the destination net, the QoS expected, etc.) so mapping is well defined
 DL mapping - When P-GW3 receives a packet from one of the PDNs, it has to consider the case
in which flows from different PDNs are defined by same fields values (i.e. have same TFT) but
expect different QoS ... (Same application used in both PDNs, but expecting different QoS). As
a result, P-GW3 has to identify the originating PDN ...
 While PDN1 and PDN3 traffic could be differentiated based on their different ingress
ports, traffic from PDN1 and PDN2 can not be differentiated (they have same TFT and
arrive on same physical port) ... unless ...
R
R
PDN - Packet Data Network
Glossary

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
SGi
MME
S-GW1
S11 Rx
P-GW3
PDN 3
PDN 1
PDN 2
Bearer
 LTE bearer
 DL mapping - When P-GW3 receives a packet from one of the
PDNs, it has to consider the case in which flows from
different PDNs are defined by same fields values (i.e. have
same TFT) but expect different QoS ... (Same application used in both PDNs, but expecting
different QoS). As a result, P-GW3 has to identify the originating PDN ...
 While PDN1 and PDN3 traffic can be differentiated based on their different ingress
ports, traffic from PDN1 and PDN2 can not be differentiated (they have same TFT and
arrive on same physical port) ... unless ...
 P-GW3 checks IP addresses of incoming packet
 Checking SA - Assumes that P-GW keeps track of all IP SA in all PDNs to which it
provides access - impossible, too much info
 Checking DA - Assumes that entities in each PDN address the SAME UE using
different IP addresses ... which implies that UE generated traffic uses different IP
SA when addressing different PDN
R
R
Glossary

BASIC TECHNOLOGIES
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
SGi
MME
S-GW1
S11 Rx
P-GW3
PDN 3
PDN 1
PDN 2
Bearer
 LTE bearer
 Conclusion
 When a first bearer is created by UE (default, non-GBR) to
a PDN, the respective P-GW allocates to UE an IP address
to be used by UE as IP SA for all the traffic destined to the
respective PDN. For bearers created toward OTHER PDN, P-GW allocates to UE OTHER IP
address to be used as IP SA. This forces the traffic back from PDN to UE to arrive at P-GW
with IP DA that reflects the originating PDN!
 The amount of IP addresses to be remembered by P-GW is equal to the number of PDNs to
which it is connected (significantly less than remembering ALL the users in those PDNs!)
 Additional bearers created toward the SAME PDN use the IP address received when the
default bearer was created. There can be no identification problems as flows to SAME PDN
can not have SAME values for TFT fields and expect DIFFERENT QoS...
Different QoS expectations => different bearers => different values for TFT fields
R
R
Glossary
net1...
net2...
net3...
net4 ...
net5 ...
net5 c for traffic to PDN 3
net4 a for traffic to PDN 1
net4 b for traffic to PDN 2
Notes
 net4.a, net4.b and net5.c have to be public addresses; reachability to them is advertised by routers R into their respective PDNs
 For practical purposes, in IPv4, a NAT will be probably present between P-GW3 and each of the routers, translating UE's multiple IP addresses into one single IP address toward routers R. (UE has to be a Client)
 UE has to support multiple simultaneous IP addresses
NAT - Network Address Translator

BASIC TECHNOLOGIES
eNB
eNB
Uu
S8
Uu
S6a
Gxc
X2
S10
UE
UE
PCRF
HSS
MME
S11
- Entity located in a diff. net
HSS - Home Subscriber Server
AMBR - Aggregate Max. Bit Rate
PDN - Packet Data Network
PDN 1
 APN
 The name associated with a specific PDN
 APN format: netID.OperatorID
 The name of a table kept in HSS for each known UE,
indicating the rights of the respective UE in terms of access
to the PDN with same APN name [including APN-AMBR
PDN 3
PDN 2
P-GW3
(Aggregate Max Bit Rate) for all the non-GBR flows that the respective UE is allowed to inject
into the APN]
 During the network entry process of a specific UE, MME gets from UE's HSS details related to
the APN(s) that UE has right to connect to (APN name, APN-AMBR, security parameters, etc.)
 MME makes a query to DNS, for APN name; the response is a list of P-GWs that can be
used to access that PDN/APN (e.g. query for APN2 would result in coordinates of P-GW5,
P-GW3 and P-GW4; MME would select one of the P-GWs (based on internal algorithms)
as the one to be used for actual traffic.
 Selected P-GW will then generate an IP address to be used by UE, for DL traffic
identification (see previous slide)
APN2
P-GW6
P-GW5
P-GW4
PDN 8
S-GW
P-GW8
S5
R
R
R
R
R
APN8
local
Glossary

BASIC TECHNOLOGIES
Access Stratum (AS) / Non Access Stratum (NAS)
SAE GW
eNB
eNB
Uu
S5/S8
Uu
S6a
Gxc
Gx/S7
X2
S10
UE
UE
PCRF
HSS
PDN /
IMS
SGi
P-GW3
MME
S-GW1
S11 Rx
Access Stratum (AS) messages
 Control plane messages exchanged by Mobile Device with its Base Station, controlling
radio access related parameters
 Different Radio Access Technologies (RAT) have different sets of AS messages
 In LTE, AS messages / protocols are present between UE and eNB
Non Access Stratum (NAS) messages
 Control plane messages exchanged by Mobile Device with the network itself, using RAT
section in a transparent / pass-through mode
 NAS messages are not specific to a particular RAT
 In LTE NAS messages / protocols are present between UE and MME for session
management and mobility management
R
Glossary RAT - Radio Access Technology
(N)AS - (Non) Access Stratum
AS traffic
NAS traffic

Sect.03 - Basic technologies and concepts (m004) - 16-02-04-1.pptx

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